Keeping a cool Head: Hypothermia for Neuroprotection after Cardiac Arrest

Induced hypothermia (lowering the body temperature to ≤35°C) attenuates neuronal damage and provides neuroprotection mainly through lowering the rate of metabolism. It thus finds applications in ameliorating the secondary damage associated with traumatic brain injury, cardiac arrest, and stroke. This article will focus on therapeutic hypothermia after cardiac arrest.

Advantages of Hypothermia
For each degree centigrade decrease in body temperature, cellular metabolism is reduced by 5-7%, but the observed neuroprotective effect of hypothermia is much greater than can be explained by reduced metabolism alone [1].
During hypothermia the brain is exposed to fewer excitatory neurotransmitters and has more time to clear free radicals. It also reduces the average kinetic energy and hence the velocities at which free radicals travel, effectively lowering the likelihood that a free radical can damage vital cell parts before it gets neutralized by the endogenous antioxidative system.
Altogether, hypothermia induces a favorable shift in intracellular concentrations of ions and metabolites such as inorganic phosphate, lactic acid, Ca²⁺ and H⁺, hence slowing brain acidosis [1].

Hypothermia Studies
Animal studies of therapeutic hypothermia have shown profound neuroprotective effects [1]. Despite being the most used model, the small rodent brain is structurally, dimensionally, and metabolically different from the proportionally bigger and complex human brain. Therefore, it probably shows a greater response to neuroprotective efforts. Unlike with rodent models human studies must take into consideration different temperatures, duration of therapy, therapy onset/ending, cooling methods, and factors such as age, gender, and pre-existing illness [1,2]. Clinical studies of hypothermia after cardiac arrest have therefore produced strongly inconsistent results.
The two largest recent controlled studies on humans have shown significant improvements in patients’ neurological outcome and survival. The European study on “Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest” showed a reduction in mortality by 14% and a 16% increase in patients with a good neurological outcome (able to live independently ½ year after cardiac arrest) in the hypothermia group. The 2002 Australian study on “Treatment of Comatose Survivors of Out-of-Hospital Cardiac Arrest with Induced Hypothermia” demonstrated a 26% increase in patients with a good neurological outcome [1,3].

Cooling Methods
Cooling must be accompanied by the use of sedatives and neuromuscular blockers, otherwise treatment will cause shivering and hence re-warming of the body with a counterproductive increase in energy/oxygen consumption. A good treatment protocol and adequate monitoring is required to successfully apply hypothermia.
Many adequate cooling methods are available and, with advancing medical technology, even more have become available. One such new device is an intravascular heat exchanger [3], which allows for rapid cooling and exact monitoring of blood flow and temperature. Another new internal cooling method is the intravenous infusion of iced isotonic fluid, such as saline solution [2,3]. Because saline solution is readily available even in a pre-hospital setting and safe to use regardless of age or gender, this is a suitable candidate for the early initiation of hypothermia. It is nevertheless necessary to maintain the cooled state with other methods later [2,3].
External methods include the application of ice packs to areas with a high heat exchange capability like the armpits, neck, groin or the head in the form of a cooling helmet [3,4]. However, proper placing of these devices requires a breach of privacy, especially when carried out in a pre-hospital setting. In addition the rate of cooling is relatively slow. Alternative methods include the use of cooling blankets or wet-evaporative cooling [4].
Hypothermia should be initiated as soon as safely possible but homeostatic imbalances induced by ischemia and the physical insult of reperfusion will persist for days. Hence there is a long time window (48-72h) to initiate and maintain hypothermia. Any one cooling method alone has shown lower efficacy than two or more methods combined. That and the rapid invention and inclusion of new cooling methods is one reason why an optimal therapy has not been developed and should therefore be researched and compared across qualified hospitals around the world.

[1] Poldermann, Intensive Care Med, 2004
[2] Peberdy et al, Circulation, 2010
[3] Nolan et al, Circulation, 2003
[4] http://bit.ly/13SyEz4


By Rick Cornell Hellmann, Alumni Medical Neurosciences, AG Spinal Cord Injury

Hyperthermia Impairs Memory Functions

On extremely hot summer days, can we really perform our everyday tasks with full efficiency? Can we focus our attention on what we want? Or should we, perhaps, take at least two months off because working during summer does not make any sense?

Image by stux via pixabay

 
Once again, scientists do not disappoint us by providing research on the influence of hyperthermia on cognitive processes. In a number of studies, healthy participants were exposed to high temperatures and then tested on their cognitive abilities in comparison to control groups. The results are consistent and point to the fact that hyperthermia does indeed impair short-term memory. More specifically, it influences reaction time during visual short-term memory performance, yet does not affect the accuracy [1]. Importantly, it enhances activity in bilateral dorsolateral prefrontal cortex and right intraparietal sulcus, regions important for task performance [1]. It is speculated that these activity changes are due to the higher occupation of cognitive resources in response to hyperthermia.
In other studies, it has been shown that heat exposure impairs complicated cognitive abilities, like the aforementioned visual short-term memory. However, it does not affect performance in simple tests, like attention tests [2,3]. Moreover, the authors showed beneficial effects of head cooling during hyperthermia, which preserved memory capacity, but appeared ineffective on visual recognition tests [3].
Armed with this knowledge, you always have a good excuse when something goes wrong on a very hot day. Jumping into a lake is nothing more than improving your cognitive skills! Just remember to keep a cool head, at all times! 

[1] Jiang et al, Int J Hyperthermia, 2013
[2] Gaoua et al, Int J Hyperthermia, 2011
[3] Racinais et al, J Physiol, 2008

by Filip Morys, Alumni Med Neuro
This article originally appeared 2013 in CNS Volume 6, Issue 3, Heat or Cold: What's Good for the Brain?

Laughter As An Exercise

In modern society there is a trend: to accomplish success and peak performance in every field of work, you should be healthy. Therefore, many people start to work out their bodies (and unfortunately not their souls), in gyms. After a while, they get bored. Is there an alternative for those of who are not morally satisfied when they gaze at their reflection in the mirror while doing bicep curls? Yes there is!

If you have enough fun, you could be both fit and healthy! Laughing, at the very least, is equally effective for your body as physical exercises. Let’s explore the biological advantages of laughing to learn more about this radical exercise program.

Nuts and Bolts

Motion, emotion, and cognition are the three elements upon which all our laughing, giggling, and guffawing are based. We know that laughing increases blood pressure and heart rate, changes the way we breathe, reduces the levels of certain neurotransmitters (catecholamines and neuroendocrine peptides), and provides a boost to the immune system [1]. Mirthful laughing can further reduce stress and improve the activity of natural killer cells. As low natural killer cell activity is linked to decreased disease resistance and increased morbidity in those with cancer or HIV, laughter might be a useful cognitive-behavioral intervention [2].

Unlike other elements of human behavior, laughter requires the entire body to actively participate. In particular, laughing can help improve cardiac vagal tone. This tone reflects the relationship between our heart rate and breathing. In stressful situations, cardiac vagal tone indicates the "capacity" of your body to regain calm (and presumably carry on). Regular laughter, therefore, can improve our ability to relax. Intense "belly" laughter exercises the diaphragm and tones the abdomen and many other core muscles [3].

200 LAUGHS = INTENSE ROWING FOR 10 MINUTES

Sounds fantastic! What kind of other physical activities can provide low impact exercise without special equipment or accessories? Not to mention burning calories: Dr. William Fry from Stanford University said in a recent interview that laughing 200 times can burn as many calories as rowing intensely for 10 minutes. It also boosts your energy and gives you that "alive" feeling. How else can laughter keep you fit, both mentally and physically? Perhaps you could try Laughing Yoga, a movement that has been slowly growing worldwide.

Serious Yoga Gets Funny

Although adherents of this type of exercise believe that their practices are strongly rooted in scientific evidence, not all doctors agree. Unfortunately, the medical community is reluctant to embrace and support laughter for health. It is claimed that the effects of humor and laughter are nothing but a placebo effect. Laughing Yoga produces all the psychological benefits of natural (involuntary) laughter by voluntarily simulating laughter or by self-inducing laughter. Laughing Yoga then combines this artificial laughter with yogic breathing as a form of group exercise [4].

Could this truly be effective? Well, it has been shown that aerobic laughter exercise significantly increases positive feelings, social identification, personal efficacy, and the morale of healthy employees in the workplace [5]. Doubtless, there is still a lot of research to be done in the area. At present, it is difficult to sift out the cause and effect of these cited health benefits.

In conclusion, there is no “magic bullet” which could save mankind from depression or lack of physical activity. However, it appears that, with laughter, it is possible to improve your physiological and physical state. According to Laughing Yoga, this is “tricking” your brain-body relationship with unconditional laughter, yoga breathing, stretching, and mental preparation with positive thinking. Why “tricking”? At the end of the day, our bodies don’t feel the difference between the effects of conditional and unconditional laughs [2]. Who knows, this interesting new undertaking might be a great alternative to boring gym classes! More importantly, it could also be an exciting new avenue of treatment for many chronic diseases.

[1] Berk et al, Am J Med Sci, 1989

[2] Bennett et al, Altern Ther Health Med, 2003

[3] Martin, Psychol Bul, 2001

[4] Shahidi et al, Int J Geriatr Psychiatry, 2011

[5] Beckman et al, J Prim Prev, 2007

by Nailya Bikmurzina, MSc MedNeuro

this article originally appeared 2015 in CNS Volume 8, Issue 1, Humor

Sprinters, Swimmers, and Bellybuttons

Which sport should you pick up this summer, running or swimming? For your decision, keep in mind that the centre of mass is key to success in speed sports.

How many gold medals would Michael Phelps have won if he had decided to be a runner instead of a swimmer? If Usain Bolt took a dip in the pool rather than a lap around the running track, would he still be a record-breaking sportsman? According to science, they probably would not be as successful had they chosen a different sport.

By HansenHimself via pixabay

 
Professional athletes train in their respective sports for the better parts of their lives. They maintain exercise and dieting plans for years that would break many of us down in days. As a result, they develop a physical prowess that allows them to achieve incredible feats. For many people, however, choosing the wrong sport may mean that they never live up to their true athletic potential.
Genetics, which are at least partly responsible for body mass and height, play a crucial role in determining which sports athletes excel at. In fact, the reason why people of certain ethnicities do better at some sports than others may be explained by simple physics [1]. When running, locomotion is achieved as the centre of mass of the body falls forwards from a height corresponding to the distance from the centre of mass (approximately at the bellybutton in humans) to the ground. While swimming, forward locomotion is dependent on the distance from the bellybutton to the top of the head producing a lever-like mechanism oscillating about the centre of mass and generating water waves.

ATHLETES, TAKE A LOOK AT YOUR BELLYBUTTON!

The location of a person’s centre of gravity affects their aptitude for speed sports. Due to their long torsos, white athletes tend to have lower centres of mass and are often successful at swimming. Black athletes on the other hand usually have high centres of mass (with long, slim limbs) and fare better at running [2].
For all you budding athletes deciding which sport to pursue, it’s always worth taking a look at your bellybutton.
[1] Charles and Bejan, J Exp Biol, 2009
[2] Bejan et al, Int Journal of Design and Nature, 2010

by Ahmed Khalil, PhD Student AG Fiebach

this article originally appeared 2014 in  CNS Volume 7, Issue 3, Nature vs Nurture

Conference Report: 14th Annual Meeting of the Vision Sciences Society 2014

In May 2014 Apoorva Rajiv Madipakkam had the opportunity to visit Florida and the annual Meeting of the Vision Sciences Society.

In the second week of May, vision scientists from around the world came together in Florida, for what is probably one of the largest vision science conferences: the Vision Sciences Society (VSS). 
With every possible topic concerning visual perception, from attention and face perception to computational modeling and eye movements, the conference was filled with the presentation of exciting ideas and data. Workshops that included discussions on the most controversial topic in science – journal publications and impact factors – made the conference even more lively.
Apart from the daytime sessions, the evenings were also filled with interesting events like the Illusion Of The Year contest. The dynamic Ebbinghaus illusion bagged the prize for this year. The classical Ebbinghaus illusion is the apparent change in size of a central circle, depending on the context in which it is presented. That is, the central circle appears bigger when surrounded by smaller circles and smaller when surrounded by bigger circles although the actual size remains the same. The classical illusion has a new twist to it which can be checked out here: http://bit.ly/1s6cpki

Beuchet Chair, source: http://viperlibnew.york.ac.uk/

A report of this conference would, of course, not be complete without the Demo Night, where one could be a part of several visual illusions and phenomena. For example, there was a demonstration of the famous Beuchet chair. Here, the two separate parts of the chair seem to belong together even though they are at different distances. However, they have the appropriate sizes to create a single image on the retina at an intermediate distance. The Demo Night felt a bit like Disneyland for scientists... it was magical, exciting, and required standing in a queue to take part in the demonstration. It definitely felt like the organizers had the perfect recipe for the balance between work and fun! The deadline for submission of abstracts for next year's VSS is the middle of December. For more information: www.visionsciences.org

by Apoorva Rajiv Madipakkam, Alumni AG Sterzer

this article originally appeared 2014 in CNS Volume 7, Issue 3, Nature vs Nurture

The Dancing Brain

Neural Correlates of Dance

Dancing is most definitely my favorite form of art. It is actually one of the few forms that can be placed in both the categories of arts and sports (maybe we should start calling it a ‘spart’!). Dancing beautifully integrates complex motor learning and memory, rhythmic musical synchronization, and creative emotional expression. As a neuroscientist and a dancer, I feel compelled to summarize here the links between these two fascinating fields and some interesting features of the dancing brain.

Dance Performance

Not surprisingly, the brain areas that are activated during dancing are mostly the ones involved in the planning and execution of movements (motor cortex and basal ganglia), in receiving feedback from the muscles (somatosensory cortex), and in the fine tuning and coordination of movements (cerebellum) [1].

Brown and colleagues looked more deeply into which brain areas are activated by particular aspects of dancing. They placed amateur tango dancers in a positron emission tomography scanner while performing leg movements on a designed apparatus. The putamen (part of the basal ganglia) was strongly activated only when the subject danced to regular, metric music, but not to an irregular rhythm. The cerebellum was implicated in matching dance steps to music and the superior parietal lobule was engaged in spatial guidance of leg motions [2].These findings suggest that different areas of the central nervous system are responsible for the control of specific and distinct tasks in dancing.

Source: Chris Gash

Dance Observation

Other neuroimaging studies observed the brain's response to visual observation of dance. Dancers trained in either ballet or capoeira (a Brazilian martial art) and non-dancers watched videos of both these styles while their brains were scanned. All subjects showed activation of brain areas involved in action observation and simulation networks – the “mirror neuron system”.

However, activation of these areas was stronger in dance experts and even stronger when the dancers saw movements they had been trained to perform, compared to watching movements they were unfamiliar with. There was no difference in the brain activity of non-dancers while watching ballet or capoeira [3]. This shows that even passive observation of dance activates movement areas in the brain as if you were moving yourself, and that dancers have an enhanced neural representation of their personal motor repertoire.

With Practice Comes Adaptation

An interesting study showed that the brain of ballet dancers adapts to prevent them from feeling dizzy. Brain scans revealed that the vestibular cerebellum, an area responsible for the perception of dizziness, is smaller in dancers compared to non-dancers [4]. This demonstrates that even the vestibular response is sensitive to training. Also, skilled dancers depend less on vision for postural control compared to non-dancers. Instead, they rely on their highly accurate proprioception – the sense of awareness of body parts’ positions in space [5].

DANCING INCREASES NEURAL CONNECTIVITY

Professional dancers are also trained with motor techniques to perform highly demanding moves in apparently effortless ways. An electromyography study showed that, when performing swinging leg movements, skilled ballet dancers selectively applied minimal muscle tension at the very same position where the sway force was maximal. This means that they learn to optimize motor function and consequently reduce energy costs in terms of force and muscle contraction [6].

Benefits of Dancing

Several studies have observed better balance, posture, proprioception, and cardio-respiratory resistance in dancers compared to non-dancers. But don’t think you would have to become a professional to profit from these benefits. Even short episodes of breakdance training increase balance skills in young amateurs [7].

Dance practice has the potential to improve not only motor, but also cognitive skills. An impressive 21-year study showed that frequent dancing is highly protective against dementias, such as Alzheimer’s disease, lowering the risk as much as 76%! It was also found to be much more beneficial than doing crossword puzzles (47% reduced risk), reading (35%) or swimming or bicycling (0% – no difference at all) [8].

DANCERS RELY ON PROPRIOCEPTION MORE THAN VISION

Neuroplasticity is likely responsible for this effect. When we dance, we enrich our brain, making split-second decisions and creating new synapses and neural paths that become especially valuable as we age.

Dancing is not only physically demanding, it is cognitively demanding as well. So when you dance, you are exercising both your body and your brain. Regular dance training makes you improve innumerable motor and cognitive skills, contributes to brain plasticity, and enhances social interaction. And, all health benefits aside, dancing is simply fun! How much better can it possibly get?

[1] Hänggi et al, Hum Brain Mapp, 2010
[2] Brown et al, Cereb Cortex, 2006
[3] Calvo-Merino et al, Cereb Cortex, 2005
[4] Nigmatullina et al, Cereb Cortex, 2013
[5] Golomer and Dupui, Int J Neurosci, 2000
[6] Lepelley et al, Exp Brain Res, 2006
[7] Ricotti and Ravaschio, Gait Posture, 2011
[8] Verghese et al, N Engl J Med, 2003

by Mariana Cerdeira, PhD Student AG Harms

This article originally appeared 2015 in CNS Volume 8, Issue 2, Art. And the Brain.