Head-Turning Asymmetries during Kissing

Did you know that there is a name for the scientific study of kissing? It is called Philematology, from the ancient Greek word philos = earthly love. Scientists found out that we use up to 34 muscles for intensive kissing, that kissing increases levels of endorphins and dopamine, and that we exchange as many as 10 million to 1 billion bacteria during kissing (don't worry, 95% of them are not pathogenic for immunologically competent people). You might be aware of that, but have you ever wondered why you nearly never bump your partner’s nose or head when you kiss?

The Kiss by Auguste Rodin, Musée Rodin, Paris

Onur Güntürkün observed 124 kissing pairs in public spaces in three countries and documented that 65% turned their heads to the right and only 35% to the left, resulting in a 2:1 ratio for right-kissing [1]. Where does this head-turning asymmetry come from? Is it due to brain laterality or due to a motor bias?

Romantic Theory about the Influence of Emotion
One hypothesis is that head-turning asymmetry during kissing is linked to brain laterality. In popular psychology the left hemisphere is often said to be involved in analytical thinking, whereas the right hemisphere processes emotions. At least for posing behavior in portraits, it was shown that the emotional context has an effect on lateralisation bias. In emotive conditions, individuals show the left cheek, i.e. turn the head to the left, whereas when posing for an impassive scientific portrait they show the right cheek [2]. Is head-turning to the right during kissing, like posing behavior, also influenced by the emotional context?
To study the association of right-kissing and emotions, subjects were asked to kiss a life-sized doll head without emotion. The right turning ratio was compared to that of kissing couples. The results showed a similar right turning ratio for both the doll kissers and the couples. As no preferential difference between kissing couples and doll kissers was observed, the emotion theory was dismissed. Kissing the doll does not involve emotions like kissing a partner, but the head-turning ratio was still similar [3].

Reappearance of a Neonatal Right-Side Preference
Another possible explanation for the preference of right-kissing is the persistence of a motor bias seen in neonates: During the final weeks of gestation and during early infancy, most humans have a preference for turning the head to the right. This motor bias persists into adulthood and has effects on various asymmetries. The preferential head turning direction in infants can even be used as prediction for later handedness [4]. However, the prevalence of right-handedness is 8:1 [5]; thus not consistent with the 2:1 kissing ratio for the right side observed by Güntürkün. Thus, the kissing asymmetry is not a simple result of right-handedness. If the asymmetry during kissing is caused by a motor bias, how is it related to handedness and other lateral preferences?
To test whether head-turning preference is related to other lateral preferences, the handedness, footedness, and eye preference of volunteers who were asked to kiss a symmetrical doll face were determined. The study revealed that right-kissers were more likely to be right-handed and right-footed than left-kissers [6]. This relation could not be shown for eye preference, but as the data structure was the same the authors speculate that their questionnaire was not detailed enough. However, the study showed that head-turning preference during kissing is indeed due to a motor bias and related to handedness and footedness.

Dominance of Right-Kissers
As kissing always takes two and both kissers are always influenced by the partner’s head-turning preference, scientists were interested in what happens if a right-turner kisses a left-turner. Therefore Van der Kamp and Canal-Bruland analyzed the consistency of the head-turning bias in kissing by using a doll head rotated in different orientations that were either compatible or incompatible with the participant’s head-turning preference. In the study, right-kissers were more likely to persistently turn their head to the right even if the doll's head was turned as if kissing on the left side [7]. Because the head turning bias among right-kissers is stronger than among left-kissers, two people with different head-turning preferences are more likely to turn their heads to the right during kissing. Furthermore, the results support the hypothesis that behavioral asymmetries are stronger for individuals with a lateral preference pattern for the right than for the left side [8].
In conclusion, the observed asymmetries during kissing can be explained by a motor bias rather than by the emotive context.

[1] Güntürkün, Nature, 2003
[2] Nicholls et al, Proc Biol Sci, 1999
[3] Barrett et al, Laterality, 2006
[4] Michel, Science, 1981
[5] Corballis, Psychol Rev, 1997
[6] Ocklenburg and Güntürkün, Laterality, 2009
[7] Van der Kamp and Canal-Bruland, Laterality, 2011
[8] Searlman and Porac, Brain Cogn, 2003

By Claudia Willmes, PhD Alumni, AG Eickholt and AG Schmitz 

This article originally appeared 2014 in CNS Volume 7, Issue 2, Neuroscience of Love

Don’t Give Up On Your Dreams. Sleep On!

Sleep is an almost universal behavior throughout the animal kingdom. Humans spend roughly a third of their life sleeping, therefore we can call it a truly integral part of life. However, is sleep just a uniform state of unconsciousness opposite to being awake? 

Like most animals, humans' sleep and wakefulness are modeled by inner circadian rhythms and external cues, so-called zeitgebers (see also the article on chronotherapeutics on page 10), to a period of roughly 24 hours. In particular, sunlight is able to reset our inner clocks, thereby enabling us to adjust our daily rhythm, e.g. after intercontinental flights. Not sleep itself, but rather when we sleep is regulated by the suprachiasmic nucleus in the anterior hypothalamus, which functions like an internal clock and is affected by environmental inputs (again, especially sunlight, which reaches the hypothalamus via the retinohypothalamic tract) [1].

sleep well; source:  http://bit.ly/2yFBDBZ

Is sleep just a consequence of the brain being less active because it's tired? Although this explanation might appeal to many fellow PhD students, sleep is characterised by a complex pattern of brain activity! Key aspects of sleep are: little motor activity, little response to stimulation, typical postures (like lying down curled up) and the state being quite easily reversible (distinguishing sleep from coma, for example) [1]. These features can be monitored by conventional electrical recordings, including electromyography and electroencephalography (EEG). When people (and animals) fall asleep, EEG recordings show a drastic change in neuronal activity.

Sleep = Brain Activity?!
Broadly speaking, sleep comes in two flavors: REM (rapid eye movement) sleep and non-REM sleep, which consists of four stages of characteristic brain activity patterns. Wakefulness typically comprises approximately 20 Hz waves. When people fall asleep, this frequency falls to 10 Hz and entering sleep stage 1 is characterized by mixed frequency patterns, light muscle activity and slow rolling eye movements. Likewise, body temperature and metabolism slow down. The next stage (stage 2) is characterized by 12-14Hz activity sleep spindles and K complexes, biphasic high-voltage waves. The sleep stages 3 and 4 are also referred to as slow-wave sleep, as EEG recordings of these phases are dominated by delta waves of only 0.5-2Hz frequencies. In contrast to the characteristics of the four stages of non-REM sleep, brain activity in REM sleep resembles wakefulness, with some populations of neurons being even more active when you are in REM sleep than when you are awake. REM sleep is accompanied by an increase of body temperature and metabolic rate but an almost complete loss of muscle tone, except for the eyes which characteristically move rapidly [1].

Sleep phases; source: http://bit.ly/2zp9M61

Interestingly, it is easier to wake a person up during REM sleep than stage 3-4 of non-REM [2]. As brain activity during REM sleep pretty much resembles EEG patterns during wakefulness, it may not seem surprising that most dreaming occurs during these phases of a night’s sleep. Dreaming can also occur during non-REM sleep, although with a much lower incidence and slightly different characteristics [2].

Sleep is not a uniform State!
Each sleeper moves through REM and the 4 stages of non-REM sleep several times a night in cycles of 90-110 minutes. During a night’s sleep, the stages do not succeed eachother in a particular order and also change in length. For example, phases of REM sleep can take 1-60 minutes and may be accompanied by brief periods of waking [3]. The cycles through the different phases of sleep, the sleep “architecture”, differ between subjects, single nights, and also change with age. In early childhood, much more time sleeping is speny in deeper sleep stages 3 and 4 whereas in older age stage 2 sleep dominates [4]. (See also our article in "The Aging Brain")

How you sleep changes with age

But what's the point of such a complicated sleep architecture? As also discussed in the articles “Evolutionary basis of sleep” on page 5 and “Sleep and learning ” on page 6 of this issue, sleep serves important functions for the body and thus is necessary. However, being unresponsive to potential threats is a significant problem, which is in part circumvented by the fact that we alternate between periods of deeper and lighter sleep [3].
As you can see sleep is much more than just the most unproductive period between two days. It is quite complex and interesting and science still needs a lot of effort to unravel all its mysteries. Therefore, everyone should spend more time in personal field studies. For example, at home - sleeping.

Good Night!

[1] Kandel, Schwarz, Jessel. Principles of Neural Science, 2003
[2] Staunton, Naturwissenschaften, 2005
[3] Voss, Rev Neurosci. 2004
[4] Zepelin et al., J Gerontol, 1983


by Bettina Schmerl, PhD Student AG Shoichet
This article originally appeared Dedcember 2017 in CNS Volume 10, Issue 04, Sleep 

„Mum, how do dolphins sleep?“: Sleep throughout the animal kingdom

Have you ever wondered whether your dog sleeps like you – and yaps because he is probably dreaming about the mailman? Do all animals need sleep as much as we do? And how on Earth do they continue swimming or even flying during sleep?

Smart because of Mattresses?

First of all, we should define what we are talking about: Sleep can be characterized in many ways, but without electroencephalography with wild animals, we should focus on the behavioral definition: Sleep is when the animal exhibits a rapidly reversible state of immobility and reduced responsiveness to external stimuli. Furthermore, an increased drive for sleep (rebound effect) is expected after sleep deprivation [1].

Lets start with our closest relatives: Great apes exhibit monophasic sleep (like humans and unlike the majority of other mammals), meaning that they concentrate their sleep in one period per day. Theories claim the reason for this is that they are (like us) capable of building a comfortable and safe sleeping platform - allowing them to sleep more safely and therefore more deeply. Maybe our cognitive abilities just came from very comfy beds [2]?

Apes build comfy beds

 

But there are other intelligent animals that definitely have no mattress to sleep on. Many dolphins are able to rest one half of their brain while the other one controls breathing, for which marine mammals have to come to the surface. This phenomenon, which some of us would love to do during boring seminars, is called uni-hemispheric slow-waves (USW). It enables dolphins, whales and also many birds to rest one hemisphere at a time with the contralateral eye closed, changing to the other one after about two hours [1]. Brain waves similar to slow-wave sleep and REM sleep in humans have been recorded in flying frigate birds which migrate for several months at a time [3]. Remarkably, when in REM sleep, these birds as well as some other mammals like the sperm whale also show bi-hemispheric sleep. However, this behaviour can only be found on the ground – or in the case of sperm whales while floating vertically in the ocean, holding their breath for a long time [4]. A strategy like this would never work in many sharks, since they need constant flow through their gills to be able to breathe. Some seem to solve this problem by doing “yo-yo diving“: First they swim to the surface to then glide downwards, giving themselves a short period of rest [5].

Different Animals sleep differently

The sleeping behaviour of terrestrial animals can also be very different from ours: Does anyone sleep while standing - No?! Horses and other bigger herbivores often do, with help of their stay apparatus, which consists of ligaments and tendons that lock into place. Still, many of them need to lie down for REM sleep as it comes with strong muscle atonia. Due to this, horses, giraffes and also elephants actually end up having much less sleep than we are used to, getting away with just 2-4 hours per day [6]. Many short naps seem to be more beneficial for these animals, since it enables them to spend more time alert when predators are around.

Who wouldn’t like to be capable of skipping 5-6 hours sleep per day in order to prepare the next lab meeting? New-born orcas outperform us a lot when it comes to little sleep: They stay awake for one full month after birth, and only rest while pressing their body against their mother. Compared to this, big brown bats and hairy armadillos lead a pretty relaxed life, sleeping for roughly 20 hours per day [6]. 

Image Source: http://bit.ly/2B1GiM7

So far we were mostly talking about sleep similar to human non-REM. But do animals also dream? Of course, no one can ask a cat whether it was recently dreaming of mice. Anyway, many mammals, birds and even reptiles show physiological patterns with consistent with REM sleep. Dragonflies have 350 REM cycles per day, each of them lasting 80s [7] and the platypus spends approximately 5.8-8 h/day in REM [8]. REM sleep is sometimes seen as a key feature during evolution of the amniote – the common ancestor of mammals, birds and reptiles that lived more than 300 million years ago [7]. However, octopus also seem to have REM like sleep patterns that go along with changing colours and twitching of their arms [9].

Yet, the animal kingdom consists of more than vertebrates. What about insects, nematodes and porifera (sponges)? While for porifera there is no evidence of sleeping behavior, the fruitfly D. melanogaster has not only been shown to have sleep-like resting patterns but also exhibit cognitive impairment upon sleep depriviation [1]. A fatigue period (lethargus) before moulting in C. elegans suggests that sleep is somehow connected to development and related to neuronal changes [10].

What's the Purpose behind Sleep...?

Of course most sleep studies focused on very few animals from each taxa so far. For instance, just 50 out of 60000 vertebrate species have been tested for all sleep criteria so far and not all of them were found to meet all of the criteria. Nevertheless sleep-like behavior seems to be present in various animals. Can we assume that all these animals sleep for the same reason - and if so what is the reason?

Over years, several theories on the function of sleep have been developed. The original idea that sleep is mainly necessary to conserve energy seems quite unlikely nowadays since it decreases metabolism by very little amounts (5-10%), whereas hibernation saves a lot more energy [11]. Another very prominent idea is that sleep is important for learning and memory consolidation (see article of page 6). Even though there is evidence for a role of sleep in memory, it is still disputed what this role exactly is – ranging from memory deletion during REM sleep to maturation of memory circuits [12]. Recently, sleep has been linked with a restorative function in the central nervous system, leading to a clearance of free radicals and other metabolic waste that accumulates during wakefulness [13]. While many of these processes definitely occur during sleep, they don’t explain the great variation in sleep needs and patterns throughout the animal kingdom. 

Do all animals sleep for the same reason?

Trying to address this, some researchers now regard sleep as a state of adaptive inactivity, optimizing the timing of behavior according to prey/food availability and threats in the environment. In this scenario, continuous wakefulness implies the greatest energy demands but maximizes niche exploitation. This can explain why giraffes sleep so little (they have a very low-caloric diet and a high threat of predators). For bats that feed specifically on insects being active between dusk and initial hours of darkness, on the other hand, a longer period of time awake would be highly maladaptive since it increases their risk of becoming prey [14].

... we don't fully know (yet)!

Exploring sleeping behavior of other animals can, therefore, help to clarify its function in humans. While sleep deprivation in humans and rodents so far suggests that sleep influences cognition, emotion, immunity and memory, the function of sleep can still be substantially different when looking at all animals that exhibit sleep-like resting behavior. We should all be aware that, as put by Michel Jouvet, a famous sleep researcher who just passed away, "it’s not enough to use the brain of your experimental animal, it’s also necessary to use your own”. 

Annika Reinhold, MSc Student MedNeuro

References:

[1] Siegel, 2008, Trends in Neurosciences

[2] Shumaker et al., 2014, American Journal of Physical Anthropology

[3] Rattenborg et al., 2016, Nature Communications

[4] Miller et al., 2008, Current Biology

[5] http://bit.ly/2jd1XfV 

[6] http://bit.ly/2zsCd59 

[7] Shein-Idelson et al., 2016, Science

[8] Siegel et al., 1999, Neuroscience

[9] http://bit.ly/2jmPMc6 

[10] Sing et al., 2013, Sleep

[11] Assefa et al., 2015, AIMS Neuroscience

[12] Diekelmann & Born, 2010, Nature Reviews Neuroscience

[13] Xie et al., 2013, Science

[14] Siegel, 2009, Nature Reviews Neuroscience

Billboard:

White Bears, Written Words

What did you get for Christmas, maybe you got a book? As books are one of the most popular Christmas gifts we ask in today's article "Can Reading Harness Brain Plasticity?"

“Once upon a time in Uzbekistan” is not a way that many neuroscience stories begin. But for this issue on nature and nurture, a key narrative began there that would come to influence debates up to the present day.
Alexander Luria, a Soviet neuropsychologist keenly interested in the relationship between culture and the mind, studied the influence of literacy on styles of argumentation. He wanted to test whether cultural experiences could affect thought patterns. By working with illiterate peasants, he uncovered fascinating examples of how written language seemed to be necessary for abstract thought patterns. His most famous example went something like this:

Luria: “In the North, there is snow, and all bears are white. Novaya Zemlya is in the far North. What color are the bears there?”

Peasant: “I don’t know. I’ve never been to the far North. I saw a black bear here once.”

Many more such examples (dealing with everything from describing shapes to objects to self-reference) were collected in Luria’s bestseller, Cognitive Development: its Social and Cultural Foundations [1]. It went on to be a fundamental text in both neuroscience and anthropology.

via Wikimedia Commons

Putting Text in Context
Although literacy has developed too recently to alter the human genome, it is an integral part of most human societies. For example, if you are on your computer today, you will probably scan more than 500,000 words (not to mention what you see in your time offline) [2]! Furthermore, the practice of reading makes a fascinating case study for the effect of a very special type of nurture on the brain.
Reading text is a multimodal exercise, incorporating visual, auditory, and cognitive/predictive elements of language comprehension. Luria argued (and many today agree) that reading was necessary to provide a scaffold for certain types of abstract thought [1,3]. While fascinating on a purely ethnographic basis, studies such as these still leave many questions to ponder. Though literacy underlies many human interactions, it has only developed on a widespread basis in the last few hundred years. Could this relatively new type of cognitive processing be sufficient to make changes in our brain?

Reading the Signals from Neuroimaging
The hills of Uzbekistan are distant from the labs of today, and indeed, so are the approaches that are used. Although many groups worldwide still do not use written language, they generally aren’t accessible with an MRI scanner in tow. So what do we do now?
Today, our primary knowledge about the effects of reading on the brain comes from longitudinal studies in school-age children. These studies [cf 4,5] demonstrate that literacy appears to co-opt pre-existing language networks in the brain. Notably, the left superior temporal sulcus and inferior frontal areas show robust activation, correlating well with development of reading abilities. These findings are intriguing, but not entirely conclusive. In the countries where these studies were performed, children are legally obligated to go to school and receive formalized instruction. Therefore, a non-literate control group cannot be used to provide more definitive answers about the effects of literacy on the brain.

by Mark Larson via Flickr, "Use your library often!"

Recently, researchers have found a way around these challenges, to examine the development of reading skills in a more controlled setting. For example, a group in France has published a set of studies examining the neural correlates of the development of literacy in adults. Essentially, the scientists scanned the brains of adults who had learned to read in childhood using diffusion tensor imaging. They compared them with the brains of adults who had only recently acquired literacy skills. Vast tissue tracts were affected, with literacy acquisition leading to elaboration of tempero-parietal connectivity [6].
A separate study which compared two groups of illiterate adults, one of which received a reading intervention program, found evidence of reading-mediated changes in early visual processing [7]. Other evidence of literacy’s effects on the brain come from people who have reading disorders such as dyslexia. These individuals, contrary to their normally-reading peers, have been shown to demonstrate hypoactivation of several superior temporal areas typically associated with word processing and semantic retrieval [8,9]. Taken together, this work suggests a tightly interlinked series of regions in the brain that are altered through learning to read and whose malfunction may underlie a failure to do so.

Literacy: A Thoroughly Complicated Business
So can we still stand by Luria 80 years later? Yes and no. Although it appears that literacy skills do foster changes in activation and connectivity, we are still a long way from understanding how these changes might underlie certain types of abstract thought (and beliefs about polar bears). Moreover, there are several obstacles to getting the full picture about reading and the brain. At the end of the day, reading is a fundamentally culture-bound phenomenon. It is deeply influenced by the values and educational emphases of the society in which it develops.
As neuroimaging studies progress, we should not forget where all these questions started. Though a trip through the wilderness is certainly not for the faint of heart, it may still be the best way to integrate neuroscientific, ethnographic, and linguistic inquiry. And with a business as complicated as understanding literacy, it may be where we need to return.

[1] Luria, Cognitive Development: Its Cultural and Social Foundations, 1976
[2] Bunz, “Is the link economy of UK news sites managing or making abundance?” in PDA: The digital content blog, Nov 2, 2009
[3] Nell, Neuropsych Rev, 1999
[4] Berl et al, Brain Lang, 2010
[5] Horowitz-Kraus et al, Front Hum Neurosci, 2014
[6] de Schotten et al, Cereb Cort, 2014
[7] Boltzmann and Rüsseler, BMC Neuroscience, 2014
[8] Christodoulou et al, PloS One, 2014
[9] Eicher and Gruen, Mol Genet Metab, 2013

by Constance Holman, PhD Student AG Schmitz
This article originally appeared 2014 in CNS Volume 7, Issue 3, Nature vs Nurture 

The nightmare a couple of days before Christmas

by Daniel S. Margulies

'Twas two nights before Christmas
and throughout the net
a faint murmur was heard
that foretold great regret...[1]

From inbox to inbox
and web dissemination [2]
all soon heard of social neurosciences'
voodoo correlations.

source

But what's in a name?
How could all understand
what statistical nuances of criticism
were at hand? [3]

While some thusly retorted,
it all came too late,
as the mighty blogosphere
had decided its fate.

When a voice from within cried:
``But this is not fair!
Science can't be debated
out in open air!

When complex ideas
and thoughts are at play
behind tightly closed doors
must the dialogue stay.

Until resolutions within
the community are decided,
we're too vulnerable to
sensationalistic media bias.''[4]

``We know,'' said Vul et al,
"that you all are good-hearted.
We know that only needed
to finish what you started--

source

That statistics are tricky
That the tools are quite new;
But running biased
secondary analyses is voodoo.

There are ways to correct
the scientific lit
Just reanalyze your data
and we shall acquit." [5]

``But we did nothing wrong!
You misunderstand!
Using secondary correlations is NOT
some brilliant scam!

To bedazzle you
with brain-behavior relations!
It's just another way of doing
data presentation.''

``But do you really believe
Without correlation values so high
You could publish in Science,
Nature, and Nature Neurosci?''

``The question,'' they responded,
``is not how strong but where
such social function is processed
right under your hair.''

source

But with the tables turned,
None really cared.
Bloggers kept blogging,
And social neuroscience got scared:

``What will we do
when no one wants to fund us?
To publish our papers
or with brain scanners entrust us? [6,7]

Why were those voodoo
critics so mean?!
Naming our names,
and crushing our dreams?

All we ever wanted
was to help understand
Why people need people--
And how our brains lend a hand.

Why are we moral?
And why do we hate?
And how does the love or pain
of another translate?

Why does being alone
sometimes cause us such pain,
If all is controlled
by our solitary brains?

source

But most of all
how could we be to blame
For asking such questions
in the social realm's name?''

Over months the debate dwindled
'Till summer arrived at last
And a salmon was scanned
During a perspective taking task.

The point, the authors told us
Was not that dead salmons feel
But rather that the importance
Of statistical correction was real.

With uproarious laughter
The conference hall replied:
``Multiple comparison correction
Cannot be denied!''



The moral:

When finger pointing begins
You'll get everyone's attention
But surely before long
you'll be buried in dissention.

To say something critical,
Try to say it in jest--
And those who can follow
Might just heed your request.


1.    Vul, E. Ed Vul - Voodoo correlations. (2010).at <http://www.edvul.com/voodoocorr.php>
2.    Begley, S. The 'Voodoo' Science of Brain Imaging. Lab Notes  (2008).at <http://blog.newsweek.com/blogs/labnotes/archive/2009/01/09/the-voodoo-science-of-brain-imaging.aspx>
3.    Abbott, A. Brain imaging studies under fire. Nature News 457,  (2009).
4.    Jabbi, M., Keysers, C., Singer, T. \& Stephan, K.E. Voodoo Correlations in Social Neuroscience" by Vul et al. - summary information for the press. at <www.bcn-nic.nl/replyVul.pdf>
5.    Vul, E. Ed Vul - Voodoo rebuttal.  (2010).at <http://www.edvul.com/voodoorebuttal.php>
6.    Bardin, J. Voodoo That Scientists Do. Seed Magazine  (2009).at <http://seedmagazine.com/content/article/that_voodoo_that_scientists_do/>
7.    Lehrer, J. In Defense of the Value of Social Neuroscience. Mind Matters  (2009).at <http://www.scientificamerican.com/article.cfm?id=defense-social-neuroscience>

New Issue Out Now! SLEEP

“I have too much to do. I can sleep when I’m dead.” Sounds familiar? Why do we even bother spending a third of our lives unconscious? In this issue of the Snoozeletter (sorry for the pun), we drift off to dreamland to explore one of the most mysterious neurological phenomena of all time.

access the full magazine

Have you ever wondered whether your pets dream (about you, hopefully) (pages 4-5)? Or whether skipping a few hours of shuteye is a good idea? Spoiler alert: it’s not! You need it to remember (page 6), to develop (page 11), and work on your fine motor skills (page 13). And with enough sleep deprivation, you will also learn how things go downhill really fast (pages 9 and 14). Think that your sleeping patterns probably don’t match a 9 to 5 schedule? Check out our article on social jetlag (page 7). We cover this year’s Nobel laureates’ work (page 6) and how it could affect treatment of medical illnesses (page 10). So perhaps you shouldn’t feel so guilty for having that session of Napflix & Chill.

Sounds interesting? Well, we also talked to researchers working in a sleep lab (13), as sleep consultants (14), and even studying lucid dreaming (8). From the busiest human to the humble jellyfi sh (page 5), we all need our shuteye. Or perhaps you are dreaming a new collaborative research project? Hear about this year’s exciting DESIRE conference from our correspondent Aliénor Ragot (14).

So put on your pyjamas, crawl into bed with a glass of Glühwein, and get into December hibernation-mode with some great writing from the Berlin neuroscience community. Happy reading, and enjoy the winter holidays!

Constance Holman & Helge Hasselmann

Co-editors-in-chief

Where Faith Meets Science: How Neuroscientists Relate to Religion

...this is the name of a post from Mayim Bialik [1], whom many of you know as Amy Farrah-Fowler in the TV series "The Big Bang Theory". It describes two topics that wouldn’t go together for many neuroscientists. Or would they? Are religion and neuroscience (any science, in fact) really that incompatible?

As scientists we try to deduce our knowledge from well-planned experiments and believe what we can see with our own eyes, or through the microscope. A religious person believes in the relation of humanity to the transcendental. On first sight it seems as if these are two contradictory paradigms since there seems to be no experimental evidence for the transcendent (yet), but nevertheless 51% of biological and medical scientists in the U.S. believe in either God or a universal spirit or higher power, according to a Pew Research Center survey in 2009 [2]. Therefore, religion apparently has an influence on today’s scientists and conceivably on their research.

Religious and a Scientist?
Dr. Andrew Newberg, for instance, uses neuroscientific methods to investigate religious and spiritual experiences, pioneering the field of neurotheology (see also article on page 10). Studying the connection between neuroscience and religion, he came to the conclusion that "whether or not God exists out there" is something that neuroscience cannot answer [3]. Dr. Mario Beauregard is another scientist who deals with the existence of a soul. In his book "The Spiritual Brain", he argues in favor of a reality outside the brain that people actually sense during intense spiritual experiences [4].
However, Dr. Michael Graziano, professor of Psychology and Neuroscience at Princeton University, focusing on the brain basis of awareness, likes to describe spiritualism as a fundamental mode of perception by which humans relate to the world. The perceptual world that emerges from that theory is to him not contradicting or threatening science, but a psychological phenomenon that is of high importance to the human existence [5]. Taking this into consideration, the idea of bringing together the world of religion and neuroscience in a single person's belief system does not seem to be impossible anymore.

NEUROSCIENCE CAN’T ANSWER IF GOD EXISTS

 
For Dr. Mayim Bialik, a former neuroscientist from UCLA and reformed-turned-orthodox member of the Jewish faith, working in neuroscience has even deepened her belief in a divine plan for the universe. Importantly, God to her is not an old man in the sky, fulfilling one's wishes if you pray hard enough, but rather "the force in the Universe that drives all of the phenomena that we experience as human beings“. Mayim explains that "understanding the relationship between science and God makes [her] a better scientist and a more complete person." When reading her post "Where faith meets science" you immediately recognize that for her, being religious doesn’t mean regarding the Torah as a science book. Instead, it signifies being grateful and humble in the face of how amazing our universe is, how amazing we are and how amazing our brains are [1].

Two Sides of the Same Coin
All these people seem to tell a story: the story of "Oneness". Even though religion and science seem to be different concepts, they might have more in common than we think. If we regard both as the quest for a description of the same entity, namely the universe and everything in it, then bringing them together could be a really interesting experiment worth trying.
Many great scientists throughout history seemed to be inspired by religiousness in the broadest sense. To quote Albert Einstein: "veneration for this force beyond anything that we can comprehend is my religion" [6]. In a letter to Maurice Solovine in 1951, he wrote "whenever this feeling is absent, science degenerates into uninspired empiricism".
With all this in mind, we should put the relationship between religion and science to the test with skeptic but open reasoning!

[1] http://bit.ly/1LvV5Oi
[2] http://bit.ly/2ttD7sj
[3] http://bit.ly/2uZngpY
[4] http://bit.ly/2uQ5kgF
[5] http://bit.ly/2eHtmEl
[6] Kessler, The Diary of a Cosmopolitan, 1971

by Annika Stefanie Reinhold, MSc Student MedNeuro
This article originally appeared 2017 in CNS Volume 10, Issue 3, Spirituality in Science

Einstein PhD Fellowships

The Einstein Center for Neurosciences Berlin (ECN) calls for applications for its PhD program starting in Fall 2018. 

The ECN member institutions promote cutting-edge neuroscientific research across a wide range of different disciplines and approaches. The ECN provides an umbrella structure that specifically fosters interdisciplinary and collaborative research by facilitating cooperation between institutions and by promoting interaction on all levels. 

With around 100 internationally recognized research groups, the ECN offers outstanding interdisciplinary training and research opportunities for national and international scientists, with research spanning from synapse to behavior, molecule to disease, and brain to mind.

Closing date for applications is January 14th, 2018.

Final interviews will take place in March 2018.

www.ecn-berlin.de/education/phd-fellowships.html

www.ecn-berlin.de/education/phd-fellowships.html

Call for Master’s Applications

The Medical Neurosciences Program invites bright and interested students to apply for our program. 

Ideally,candidates should already have some laboratory work experience, e.g. having worked in a lab for a Bachelor’s project, or other types of work experience such as a residency as a medical doctor.

The program’s rigorous and comprehensively structured education in basic neuroscience provides and trains students to approach questions concerning the central and peripheral nervous system. In addition to the in-depth theoretical training, our program emphasizes state-of-the art practical lab experience, preparing graduates for continued research as PhD students. 

Closing date for applications is January 15th, 2018

https://www.medical-neurosciences.de/en/admission/

Faith and Perspective: an Interview With Three Berlin Neuroscientists

With the upcoming holidays in mind, we are talking about faith and  being a scientist in today's post. Recently, we sat down for a chat with three researchers of the Neuroscience community in Berlin, the topic ranging from juggling neuroscience and faith to common misconceptions about religion. Here’s what they had to say.

Could you please tell us a little about your faith?
I am a Christian, as were my parents. When I was in grade 12, I accepted Jesus Christ as my personal savior and converted to Evangelical Christianity. And I would say during my stay in the university, I came much closer to God. I started seeking him with all my heart; the more I know Him, the more I reflect His character: love and kindness.

I'm basically born into a Hindu family. I have been practicing Hinduism since childhood. During the course of my studies and my PhD in neuroscience, I have started to question both religion and science – specifically whether either of them can fully answer questions on consciousness.

I was born in a Muslim family and had the privilege of having parents that loved to read and had a large collection of books on religion (mainly Islamic) as well as comparative religion-oriented. They encouraged me to read and I spent a great deal of time combing through books at my home. During my childhood, much like other kids, I practiced religion more out of watching what my parents and grandparents did. As a teenager, I became more inquisitive, and started practicing my religion with more reason, intent, and curiosity.

How does your faith help or influence you as a neuroscientist?
My faith shapes every part of my life, and everything I do is based on principles from the Bible. For example, I am faithful – faithful to God, faithful to the people standing next to me in the lab, faithful in everything that I do. I believe that God is watching, hence, I do whatever I do with all my heart. And I consider the opportunities I have got as an immense privilege that I should nurture and care for. Besides, living in harmony with God lets me have internal peace and keep me secure no matter what happens around.

The concept of Hinduism urges one to ask questions about one's inner self/consciousness (also known as Advaita philosophy) which helps me as a neuroscientist to shape and ask questions about workings of the brain leading to conscious behavior.

In our holy book, the Quran, there are hundreds of verses which encourage us to study and ponder. In fact, in the very first verse, where the truth about Allah is revealed to the prophet Muhammad, the first divine command is “Read!”. A quest for knowledge is thus one of the most important pursuits that one can have in life. Many people in different religions are taught that they cannot contest what is written or preached, but I believe that Islam teaches us always to be skeptical and build strong counterarguments, or put things to the test. Using this type of reasoning is extremely important for me as a neuroscientist. Furthermore, Islam teaches us that we should gain our livelihood through righteous means. That means if you happen to be a researcher, do research with a purpose and rationale behind it. We are held accountable after death for how we used our health, knowledge and time during life. Therefore, whatever we do has to be legitimate and meaningful. So, in that sense, faith definitely influences neuroscience in that it gives me a purpose behind the daily struggles of research because I know that even if I fail, I learn a lot more and that all these efforts are not futile.

What do you believe your faith can teach you about neuroscience?
I know that God has placed eternity in our heart and mindset to seek and explore what has been done under heaven. But, there are questions that science is not able to answer; about creation and existence, purpose of life, etc. People might seek and try lots of things, but there is always a void inside our heart that God can only fill. The Bible teaches us that we were uniquely, fearfully, and wonderfully created as part of a perfect system. It is fascinating to see how the universe operates by itself. Hence, being a scientist (as well as a Christian) gives me great appreciation for how intricate biological systems are perfectly made, and work together in harmony. And this makes me wonder how one can perceive it as a random event.

Hindu scriptures like Vedas and Upanishads have dealt with mind and brain in depth. For example, there are concepts of divisions of mind like Buddhi (intellect/logical part of brain), Manas (emotional parts) and Indriyas (senses). Furthermore, these texts have a lot of insights on how senses interact with the mind.

The Quran teaches us that our intelligence is what sets us apart from animals – the ability to think and reason. Islam instills in an individual that he or she is so much more than the sum of all their synapses or microbiome. Of course, with great power comes great responsibility – we shouldn’t take it all for granted. Islam thus teaches us that to lead a meaningful life, we need to use our brains!

Has neuroscience changed the way that you see your faith?
If anything, I think it’s the other way around!

Neuroscience has definitely helped me form more solid ideas of mind and brain combining the aspects of mind mentioned in Vedas.

Yes. Science is all about inquiry, and established knowledge changes fast. This has helped me be more enquiring and skeptical about my own faith. In my everyday life, I try to reason with myself a lot about the how’s and why’s of the lifestyle I follow. Neuroscience reinforces this habit.

Has anyone ever challenged you about your faith as a scientist?
Well, I am having discussions with colleagues all the time, and I think sometimes they might get perplexed with my faith. Scientists are always looking for concrete proof, something tangible to prove things about God and the universe. But faith is something that has to be experienced – it’s something that I personally have experienced, and it is something that no one can take away from me. To help you understand, look at the concept of love. It’s something that I (and most other people) have experienced, yet is completely intangible and needs to be felt to be believed. It can’t be measured!

Actually, I never felt a clash between ideas in Hinduism and neuroscience. Hinduism encourages one to seek answers for questions on 'Paramatma' which is the 'Primordial Self'. In my opinion, that is also the ultimate goal of neuroscience – to understand perception and consciousness.

Oh yes, I am challenged all the time! I have lots of friends from different religions, including some who identify as atheists. Discussing religion and science with them is a favorite topic of mine. Having your beliefs questioned is also refreshing in the sense in that it teaches you that beliefs or ideas that form your core personality may not have any significance for others – and that’s ok. Or the fact that one need not believe in a theistic religion to go out and do good in society or some seriously awesome science. I firmly believe that if the Quran is a divine miracle, its prophecies or claims will be testable and could not be falsified. My knowledge regarding both religion and neuroscience is fairly basic but this very reason motivates me to question both and improve my understanding.

Are there any misconceptions that you feel people have about your faith?
The biggest misconception I have faced is ‘faith and science are considered incompatible’. When I tell people I am a Christian, I have been asked how do you believe and be a scientist at the same time. With science, I try to understand and discover what is already there. My faith gives me the bigger picture, the purpose for life. Being a Christian is not also having certain religious practices and rituals. Faith is all about having a personal relationship with God. To me, having faith and being a religious person are not the same thing! Religion is something based on rules: do this, don’t do that. To me, being a Christian is personally experiencing God and walking the walk of life with Him through the ups and downs.

Well, it’s not specifically neuroscientific, but whenever I say I'm from India, people ask "are you a vegetarian?". I am actually, but not all Hindus are [laughs]. Some confusion also arises about the number of Gods that we have. Even though we have millions of Gods as a way of placing and expressing faith, we all believe in Paramatma, 'Primordial Self'.

There are two misconceptions that I’ve noticed a lot. First, that Islam hinders scientific progress as it’s just a set of rituals from the 7^th century. This is absurd and any hindrances to science per se are products of people’s actions (combine less education and in depth study of religion + science) rather than their faith. This also extends to people’s take on women and STEM. Despite societal constraints on women in some Muslim countries, there have also been some remarkable outcomes. If you look at countries like Iran or Pakistan, they have some of the highest number of women in STEM professions in the Muslim world. A second big misconception is that Islamic teachings are rigid, set in stone and cannot be challenged. Also not true. In fact, the Quran openly challenges people to bring a counter argument against its verses and claims to promote a lifestyle model that can adapt to the change in time.

What do you think is the most important thing for people to understand about your faith?
Faith and science are not incompatible. It just takes an open heart to experience God like love. It is not something you can validate and understand with logic. It is not rocket science either, if we genuinely and humbly seek God with an open heart, we will find Him. He is not hidden or somewhere far away, He is around revealing himself in one or another way throughout our journey. Believing in Christ gives eternal life, internal peace, meaning to life and a positive way to look at everything. A life worth living is a life with meaning and purpose. God loves you!

 People have thought about understanding the brain since many centuries, which is reflected in the religious scriptures like Vedas. Perhaps one could get answers by reading these scriptures!

As I mentioned before, the concept of skepticism and inquiry is very important. As far as scientific research is concerned, Islam encourages people to do that as it may be one way of recognizing the common design involved behind the universe and the man. For modern day issues like organ-donation and blood transfusion for instance, it encourages ‘’ijtihad’’ (thorough exertion of a jurist's mental faculty in finding a solution to a legal question). Finally, Islam stresses that acquiring knowledge and then having the wisdom to act on that knowledge is what makes us distinct from our relatives in the animal kingdom. In the Quran, the reader is warned that not acting on acquired wisdom (be it through religious books or years spent in scientific training) will demote the status of its believers. Herein lies the key problem, and the majority of Muslims who passively follow Islam like a religion of rituals and obligations don’t bother to treat it as an all-encompassing lifestyle that could be so much more beyond prayer and supplications. Believing in Quran and its writer (the Almighty) do not automatically entitle anyone to any kind of superiority (religious or educational) over others who don’t. Success in any walk of life is guaranteed to those who work hard for it.

A big thank you to all interviewees!

Content has been edited lightly for clarity and length with participants’ permission.

by Constance Holman, PhD Student AG Schmitz
this article originally appeared 2017 in CNS Volume 10, Issue 3, Spirituality in Science

Ever thought about an editorial career?

Springer Nature offices in Berlin invited PhD students and Postdoctoral Researchers to inform them about editorial and publishing careers at Springer Nature. The event took place on November 30, 2017. 

When I got an invitation for the event via the facebook group Career Development Seminar Series (check it out and join!), I jumped at the opportunity to get new ideas on how to proceed in my career, having just recently finished my PhD.

To say the least, my expectations were more than met. The evening started with four editors presenting their career paths, which was very inspiring. This was followed by a more general presentation that gave insights on how an editorial job looks like, what the different positions at Springer Nature are, and how to secure a job at Springer Nature. In the subsequent Q&A session participants asked questions from all angles ranging from how to stand out as an applicant, how the application process looks like, and how high the salaries are.

Afterwards we were invited to chat with the speakers and some more editors over drinks and snacks. Unfortunately I couldn’t eat the snacks as I was so busy talking to people, but it contributed to a very welcoming atmosphere. All in all I found the event very helpful and encouraging! 

If you are as excited as me about disseminating science, enjoy writing and communication, and are keen to read cutting-edge research before it is published, then pursuing a career in the editorial or publishing field could be right for you. 

 

Visit Springer Nature’s editorial and publishing careers page for further information and job openings at www.springernature.com/editorial-and-publishing-jobs or contact Katie Riddle, the Global Editorial Talent Manager at k.ridd@nature.com

Claudia Willmes

PhD Alumna AG Eickholt / AG Schmitz

Glory with the Silly Bits Left In - Neuroscience and the Ig Nobels

Costumes. Sing-alongs. The Win-a-Date-With-a-Nobel-Laureate contest. The truth is that the annual Ig Nobel prizes are probably the best scientific awards ceremony around. Every year in Cambridge, Massachusetts, distinguished members of the scientific community (including a handful of real Nobel Laureates) gather to celebrate some of the weirdest research around. What must one do to earn such a prestigious honor? The Ig Nobel Prize has two simple requirements: the project in question must make people laugh. But then, it must make them think.

 

 Momentous History
The Ig Nobel prize was founded in 1991 as a spin-off of the Annals of Improbable Research. This scientific journal (and today, blog) published by Harvard, collects examples of the strangest, most useless, and poorly thought-out research on the planet. But faced with a surplus of such work, they needed a way to honor the best of the best (or perhaps the worst of the worst?). As such, the Ig Nobel Prize was born.
So just what kind of research makes one laugh, then think? Well, the laughter is simple, but the thinking falls into two categories. Sometimes, prize-winners’ research will cause deep existential thoughts. For example, the 1995 Ig Nobel for Psychology went to Watanabe and colleagues for teaching pigeons to differentiate between paintings by Picasso and Monet [1]. However, other thoughts are of the “how-on-earth-did-they-get-funding-for-that?” nature. 2013’s physics prize went to a group who determined that humans are capable of running on the surface of a pond... if the pond and the people are on the moon [2].

Conrad von Soest, Source: wikicommons

Thankfully, the Ig Nobel does not discriminate between disciplines, and members of all walks of life are equally “honored”. To avoid undue embarrassment, winners are contacted privately and offered the chance to decline their Ig Nobel. The number of refusals is a tightly-guarded secret, but all published winners seem to accept the reward with good grace. For some, however, it’s just bad press: the prestigious Ig Nobel for Peace was awarded to president Viktor Lukashenko of Belarus for outlawing applause in public, and to the Belarusian State Police for arresting a one-armed man for breaking the new law. Sadly, you can’t make this stuff up [3].

“Innovation” in Brain-Based Disciplines
But enough background. This newsletter is a space for the brain! 2014 was a marvelous year for many reasons. It was also the year in which an exciting Ig Nobel for Neuroscience was awarded, spurred by ground-breaking work on what happens in people’s brains when they see the face of Jesus in their toast [4]. However, there have been many, many prizes in closely related fields. For example, the Cognitive Science prize was awarded to a certain Dr. Nakagaki, for demonstrating that a species of mold can solve puzzles. It should be noted that the award-winning paper was published in Nature [5]. In 2005, the Peace prize was given to a team who monitored neural activity in a locust while it watched Star Wars [6].
A common theme among neuro-related Ig Nobels is pain, specifically the kind where study participants probably need to be generously compensated. Are you concerned about traumatic brain injuries? Never fear! Bolliger and colleagues won a Peace Ig Nobel for studying whether it is better to be smashed over the head by an empty or a full beer bottle [7]. What about the burgeoning field of neuro-aesthetics? Well, de Tommaso and colleagues combined art contemplation with zapping subjects with a powerful (and presumably painful) laser to showcase modulation of the nociceptive response [8]. Of course, the Ig Nobels are not simple violence-mongers. In 2010, a group from the UK was awarded the Peace Ig Nobel for scientifically proving that swearing helps relieve pain [9].

Eternal Questions
The Ig Nobels have occasionally waded into real scientific controversy. For example, in 2012, a winning team led by Craig Bennett used a very fancy MRI machine and very simple statistics to find amazing activity-related correlations… in a dead salmon [10]. The study was meant as a tongue-in-cheek criticism of poor statistical practices in functional neuroimaging, but instead, infuriated many members of the community. Other studies, which seem rather silly at first glance, have actually been incredibly important. Eleanor Maguire and colleagues got an Ig in 2000 for showing that the hippocampi of London cab drivers are more developed than those of other professionals [11]. This work was one of the first hints that brains could substantially develop and rewire themselves in adulthood. No laughing matter at all for the neuroscience community…

Making you laugh. Then making you think.

Still, as a young researcher in an immensely serious field, I'd like to believe that we are capable of finding humor in neuroscience. The Ig Nobels, while quite silly and (delightfully) overblown are a fun tool for reminding ourselves that science is meant to answer people’s questions. Even if those questions are as frivolous as “why does needing to urinate change decision-making capability?” [12]. Yes, the scientific community can stand to learn a lot from the Ig Nobels. Even if it is only to keep one’s own research in perspective, and approach all discoveries with an open mind and good sense of humor.

[1] Watanabe et al, J Exp Anal Behav, 1995
[2] Minetti et al, PLoS One, 2012
[3] Barry, New York Times, 2011
[4] Liu et al, Cortex, 2013
[5] Nakagaki et al, Nature, 2000
[6] Rind and Simmons, J Neurophysiol, 1992
[7] Bolliger et al, J Forensic Leg Med, 2009
[8] de Tommaso et al, Conscious Cogn, 2008
[9] Stevens et al, Neuroreport, 2009
[10] Bennett et al, 2010, JSUR
[11] Maguire et al, PNAS, 2000
[12] Tuk et al, Psych Sci, 2011

Constance Holman, PhD student AG Schmitz
This article originally appeared 2015 in CNS Volume 8, Issue 1, Humor

Nobel Prize 2017: What Makes Our Cells Tick?

Since Wednesday the Nobel Week in Stockholm is taking place. During one week the Laureates give press conferences and hold their Nobel Lectures. The week culminated in the Nobel Prize Award Ceremony and Banquet yesterday night, December 10. (see the full programme here)

source

In October this year, the Nobel Prize of physiology or medicine was awarded to the three chronobiologists Jeffrey Hall, Michael Rosbash and Michael Young. They received the prize for their discovery of the molecular machinery that controls the biological clock.

1 million euros for telling time

In 1984, Jeffrey Hall and Michael Rosbash in Boston, simultaneously with Michael Young in New York, discovered that they could disrupt the biological clock in fruit flies by mutating a gene. This gene, called period, encodes the protein PER, which happens in a 24-hour (circadian) rhythm. During the night, PER accumulates in cells and during the day it is degraded. They hypothesized that PER could control its own concentrations via an inhibitory feedback loop. However, PER was unable to enter the nucleus... How could it influence its own production? A few years later, Michael Young was able to answer this question. In 1994, he discovered another gene called timeless and its protein TIM which, when coupled with PER, enables both of them to cross the nuclear membrane. Now the only remaining question was how PER achieved its 24-hour rhythm. Michael Young also answered this question with the discovery of a third gene called doubletime. Doubletime encodes the protein DBT that can slow down the accumulation of PER and thus produces circadian oscillations.

Wide Implications
These mechanisms were later shown to be similar in humans. Yet, the importance of the biological clock is still underestimated today, not only by the general public, but also in medicine. From hormone concentrations, functioning of the immune system, to even behavior, the biological clock regulates a vast variety of physiological and psychological functions. Sleep is just one of the things under strong influence of the biological clock. In spite of the importance of sleep, millions of people work nightshifts, thereby desynchronizing their biological clock and jeopardizing their health. This year’s Nobel Prize might provide a leg up for the chronobiologists in their efforts to show the general public how important our internal clock is. It is a win, not only for the three scientists, but for the entire research field.

Zehring, W.A., Wheeler, D.A., Reddy, P., Konopka, R.J., Kyriacou, C.P., Rosbash, M., and Hall, J.C. (1984). P-element transformation with period locus DNA restores rhythmicity to mutant, arrhythmic Drosophila melanogaster. Cell 39, 369–376.

Bargiello, T.A., Jackson, F.R., and Young, M.W. (1984). Restoration of circadian behavioural rhythms by gene transfer in Drosophila. Nature 312, 752–754.


by Jan de Zeeuw, PhD Student AG Kunz

The Hypothalamus: Central Appetite Regulation

Feeding and energy expenditure are controlled by complex neural networks distributed throughout the forebrain and brainstem. Homeostatic feeding behavior is integrated within the hypothalamus. 

Key peripheral signals of energy status such as gut hormones and adipokines either signal to the hypothalamus directly or indirectly via the brainstem and vagal afferent fibres. Adiposity signals such as insulin and leptin are involved in the long-term energy homeostasis, and gut hormones such as ghrelin are implicated in the short-term regulation of meal ingestion [1-3]. The Hypothalamus comprises various nuclei, of which the arcuate nucleus (ARC), the paraventricular nucleus (PVN), the ventromedial nucleus (VMN), the dorsomedial nucleus (DMN), and the lateral hypothalamic area (LHA) play a role in energy homeostasis.

Hypothalamic Orexigenic and Anorexigenic Neuropeptides
The ARC, known as the infundibular nucleus in man, is situated at the base of the hypothalamus. It contacts the peripheral circulation through semi-permeable capillaries in the underlying median eminence and is thus in an ideal position to integrate hormonal signals for energy homeostasis. In the ARC, there are two important discrete neuronal populations: Neurons coexpressing neuropeptide Y (NPY) and agouti-related peptide (AgRP) stimulate food intake, whereas neurons coexpressing pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) suppress food intake. Both subpopulations project to the LHA and PVN, where they control the function of second-order neurons. In the PVN, two distinct subpopulations of neurons produce the anorexigenic (appetite-suppressing) neurotransmitters thyrotropin-releasing hormone, and corticotropin-releasing hormone. In contrast to this, in the LHA, two other subpopulations produce the orexigenic (appetite-stimulating) neurotransmitter orexin (hypocretin) and melanin-concentrating hormone (for review see [4, 5]).

Peripheral Hormones and Peptides Regulating Appetite
Leptin, predominantly synthesized in adipose tissue, inhibits NPY/AgRP neurons and stimulates POMC/CART neurons. Circulating leptin levels are directly proportional to adiposity in animals and humans. Insulin, which is produced in the β cells of the pancreas and rapidly secreted after a meal, binds to insulin receptors on the surface of POMC/CART neurons and activates them. The rise in circulating insulin in response to a glucose load is proportional to fat mass. Ghrelin, a hormone from the stomach, exerts a stimulating effect when binding at growth hormone secretagogue receptors on NPY/AgRP neurons. Circulating ghrelin decreases in response to chronic overfeeding and increases in response to chronic negative energy balance associated with exercise or anorexia nervosa. Whereas obese people usually have high plasma leptin, they have low plasma ghrelin (for review see [6]).

[1] Simpson et al., Arc Bras Endocrinol Metabol, 2009
[2] Stanley et al., Physiol Rev, 2005
[3] Suzuki et al., Endocr J, 2010
[4] Velloso et al., Neuroimmunomodulation, 2008
[5] Suzuki et al., Exp Diabetes Res, 2012
[6] Neary et al., Clin Endocrinol (Oxf.), 2004

By Charlotte Klein, PhD Alumna AG Neural Regeneration and Plasticity  
This article originally appeared 2012 in CNS Volume 5, Issue 4, Fat Gut or Fat Brain