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Animals near the ectotherm side of the endotherm-ectotherm spectrum rely on external heat sources to regulate their body temperature. When they are cold, overal enzyme activity and metabolic rate is lower.

My question is if these animal tend to 'think' slower when cold?

To be honest, my knowledge of brain physiology is very sketchy, I'm not sure biochemical activity plays a large role vs. electrical and diffusion processes and the latter would be less temperature dependant. So I'm not sure we would expect ectotherms to 'think' slower.

OTOH, wikipedia on endotherms states ...

Some ectotherms, including several species of fish and reptiles, have been shown to make use of regional endothermy, where muscle activity causes certain parts of the body to remain at higher temperatures than the rest of the body. This allows for better locomotion and use of the senses in cold environments.

The source for this claim is on google books, just not the relevant pages (Willmer, Pat; Stone, Graham; Johnston, Ian (2009). Environmental Physiology of Animals)

I'm also not sure how to define 'thinking' within this wide range of animals, I'll take any metric for speed at cognitive tasks or reacting to external stimuli.

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    $\begingroup$ if the lower temperature would make the transmembrane proteins responsible for the maintenance and restore of resting potential, and creation of action potential, work slower or less, I believe it would make the thinking slower. On the other hand, the lower temperature may only alter the strength of the stimulus necessary for the action potential, in which case I don't know if the thinking would be slower or if the only change would be that there would simply be less thinking. I believe both happen, but to be sure one needs to analyze this to a deeper physiologic level and do some calculations $\endgroup$ – Filipe Rocha Apr 26 '17 at 10:08
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    $\begingroup$ temperature definitely affects insect response time, not sure about other ectotherms. biorxiv.org/content/biorxiv/early/2016/06/09/056051.full.pdf $\endgroup$ – John Jan 15 '18 at 7:23
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I would assume as the temperature decreases, even as an ectotherm organism that the neuro processes would decrease. From my experience in chemistry, the colder the temperature the slower the molecules vibrate. As a result, it would take a longer time for the sodium and calcium molecules to move from the end of the neurons to the synapses resulting in delayed thinking. If they are absorbing the energy necessary, then their neuro processes should be functioning normally.

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    $\begingroup$ Welcome to Biology SE and thank you for your contribution! However, we tend to prefer answers that are backed-up by references in this community. As it stands this is really a comment, not an answer. Additionally you seem to be contradicting yourself: will the "molecules" diffuse slower or will the "processes" be functioning properly? $\endgroup$ – vkehayas Dec 15 '17 at 20:53
  • $\begingroup$ It's usually not simply that it would take longer for the ions to move during depolarization. It's much more complicated than that, usually involving a myriad of interactions. A large part of it is that metabolic processes slow down (remember, activation energy often requires heat), and less energy in neurons means they will respond sluggishly. $\endgroup$ – forest Dec 30 '17 at 5:09
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I can't see why it would be different for ectothermal animals than endothermal animals. By lower temperatures, I'm not considering a few degrees one way or the other; there is probably a maximal temperature range for the nervous system to operate, followed by decreases in lower ranges.

You write

Some ectotherms, including several species of fish and reptiles, have been shown to make use of regional endothermy, where muscle activity causes certain parts of the body to remain at higher temperatures than the rest of the body. This allows for better locomotion and use of the senses in cold environments.

Protective mechanisms are also in place in humans, where shivering generates heat, and blood is shunted away from cold areas to core (warmer) areas to protect executive functioning (thinking) and heartbeat regularity. It doesn't mean that once thes compensatory mechanism (and others) are overcome by falling temperatures, that cognition remains unaffected.

Given extremes, there are iguanas falling frozen (not necessarily dead, though) from the trees in Florida. I doubt they even know they're falling. Maybe a muddled "Huh?" when they hit the ground, a car, etc. But I would wager that, could we read their thoughts, they are not racing with anxiety:

My ---, I'm stiff as a board! Someone help me, I can't move a muscle! What's happening? Is this a bad dream where I can't move? Am I dead? Is this HELL? Oh, ---, I wish I had spent more time with my wives and kids! Is a deathbed confession acceptable now? Can anyone hear me? Am I even talking? How could I be talking if I can't move my mouth?!

Hypothermia definitely slows down thinking in humans, e.g. in studies to try to understand the effect of cold on astronauts (not done on astronauts, though):

Chronic multifactorial stress impaired cognitive function and mood; the addition of moderate, acute cold stress further degraded vigilance and mood. When such circumstances occur, such as during disasters or military operations, measures to prevent adverse cognitive and physiological outcomes are recommended.

and

Cold stress is experienced in occupational (military, fishing trawlers, emergency disaster workers) and athletic (winter sports) settings (Muller et al., 2012). It appears that both moderate and extreme reductions in ambient temperature may have a negative effect on cognitive function (Banderet et al., 1986; Palinkas, 2001). Specifically, cold exposure (−20 to 10°C) has led to decrements in memory [complex task (Thomas et al., 1989; Patil et al., 1995)], vigilance [complex task (Flouris et al., 2007)], reaction time [simple task (Teichner, 1958; Ellis, 1982)], and decision making [complex task; see Table ​Table4;4; (Watkins et al., 2014)]. Such consistent findings across such diverse ambient temperatures may be explained by traditional theories of cold induced cognitive decrement (Teichner, 1958; Enander, 1987; Muller et al., 2012). ... Regression analysis from a recent study (Watkins et al., 2014) reported a significant relationship between alterations in thermal comfort and cognitive function in the cold.

So, yes, at sufficiently lower temperatures, cognition is decreased. One theory is that initially it is decreased because attention is directed at the discomfort of being cold (1958), but fMRI studies might clear up that issue nicely.

Cognitive function and mood during acute cold stress after extended military training and recovery.
The Impact of Different Environmental Conditions on Cognitive Function: A Focused Review

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