Perception Leads Reality - The Effect of Temperature on Perception

Perception, defined as the organization and identification of sensory information in order to represent and understand our environment [1], is in a state of constant flux. It should come as no surprise then, that even our body temperature can affect our perception.

Experiments have shown that our perception of time speeds up when our body temperature is increased above normal and decreased when our body temperature is cooled below normal [2]. The most common hypothesis for this phenomenon is that we have a temperature-sensitive biological or chemical clock and that temperature manipulation produces changes in arousal. Perhaps this explains why when we have a fever our sense of time is also warped!
Hypothermia also seems to affect our visual perception. In an EEG study of face recognition, it was found that hyperthermia accelerates the early stages of visual perception. In this experiment, upright and inverted faces were presented to two groups of participants, a control and a hyperthermic group. The hyperthermic group had earlier latencies in the two EEG peaks of interest, the P1 and N170.  However, the specific face sensitive response, the N170 had a significantly smaller amplitude in the hyperthermia group when compared to the controls. Furthermore, the inversion effect of the faces on the N170 remained unaffected. This result suggests that although hyperthermia impairs the detection of faces in the visual field and their initial streaming to face-specific structural mechanisms, the subsequent face-specific configural processing remains unaffected [3].
With respect to odor and taste perception, while the exact effect of our body temperature on odour perception remains unexplored, we know that temperature or heating itself increases the odour of a substance due to the release of volatile molecules. Furthermore, odour ratings rise when the temperature increases when samples are sniffed. However, ratings made retronasally rise only for solids and not liquids. This is thought to be because liquids reach body temperature faster than solids when placed in the mouth. [4]. As the prominent English writer Aldous Huxley says, “There are things known and there are things unknown, and in between are the doors of perception.” 

[1] Schacter, Psychol, 2011
[2] Wearden and Penton-Voak, Q J Exp Psychol B,1995
[3] Sun et al, Int J Hyperthermia, 2012
[4] Delwiche, Food Quality and Preference, 2004

by Apoorva Rajiv Madipakkam, Alumni AG Sterzer
This article originally appeared 2013 in CNS Volume 6, Issue 3, Heat or Cold: What's Good for the Brain?

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?