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Heat: Here’s why the brain slows down

July 27, 2018

An experiment conducted by Harvard University (Boston) has shown that rising temperatures correspond to a decrease in our mental lucidity. The study, published in Plos Medicine, was commented by Professor Alberto Albanese, Head of Neurology I in Humanitas, in an interview with Corriere della Sera.


Following particularly hot days, the researchers involved two groups of students to analyze their cognitive performance. The boys underwent two tests in the following 12 days; some of them stayed in rooms with air conditioning on and a temperature around 21 degrees, while others in rooms with air off and a temperature around 26 degrees.


As the researchers explained, it was found that children in rooms without air conditioning reacted 13% slower and 10% more wrongly than those in rooms with air conditioning. Even a minimal increase in temperatures therefore has an impact on our minds and can lead us to make mistakes in our answers even when faced with questions that we would easily be able to answer.


The comment of Professor Albanese

“It is a very particular experiment, of a mechanistic type, that sheds light on the way the brain works and in particular on the activity of calculation. The authors prepared two tests that the students had to undergo every morning, one of inhibition and one of numerical calculation: these are elementary and daily functions. An example of an inhibition test could be the word “red” written in green: between two options, the subject must choose the color he reads and not the one he sees. These are typical activities of the frontal lobes, a small part of our cognitive abilities.


The experiment evaluates the brain’s functioning as if it were a computer, a kind of measure of the speed of the PC processor under different thermal conditions. There was no analysis of the well being or emotional aspects of the participants, who had not been put in conditions of particular stress or maladjustment. We are talking about slight temperature variations, which do not require particularly complex compensation activities,” explained the professor.

Heat and functioning of brain: what is the relationship?

When the outside temperature is higher, the brain slows down. There is in fact an increase in blood flow and vasodilation and the metabolism no longer functions as it should, with repercussions also on the transmission of nerve impulses. The heat activates compensation mechanisms that tend to keep the body temperature constant (homeostasis).


“In this experiment, then, there is another element to consider: the subjects, young and healthy, deprived of air conditioning had not adapted to the temperature of 26 degrees, an adaptation that would have occurred if they had remained in that climatic condition for a few months (and the brain capacity would therefore have returned normal). This is why the compensation mechanisms that have slowed down the capacity for calculation have been triggered: it is as if their brain has been distracted from the metabolic point of view due to the need to maintain a constant body temperature. Those who usually live in warm regions, for example in the Tropics, have adapted to those temperatures and have no mental slowdown,” said the specialist.


Prof. Albanese then pointed out that sudden changes in temperature affect the cognitive condition and that “For the brain a temperature between 19 and 23 degrees is ideal, but unfortunately we are seeing an increase in temperature changes. Let us think, for example, of the consequences for the elderly: in them, the compensation mechanisms are much more complex than those activated in young people, because they also concern the heart, circulation and lowering of pressure. Harvard’s experiment is a small example of how a slight change in temperature requires adaptations that reduce cognitive performance even in perfectly healthy children,” he concluded.

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