Abstract
PurposeTemperature plays a fundamental role for the proper functioning of the brain. However, there are only fragmentary data on brain temperature (Tbr) and its regulation under different physiological conditions.MethodsWe studied Tbr in the visual cortex of 20 normal subjects serially with a wide temporal window under different states including rest, activation and recovery by a visual stimulation-Magnetic Resonance Spectroscopy Thermometry combined approach. We also studied Tbr in a control region, the centrum semiovale, under the same conditions.ResultsVisual cortex mean baseline Tbr was higher than mean body temperature (37.38 vs 36.60, P<0.001). During activation Tbr remained unchanged at first and then showed a small decrease (-0.20 C°) around the baseline value. After the end of activation Tbr increased consistently (+0.60 C°) and then returned to baseline values after some minutes. Centrum semiovale Tbr remained unchanged through rest, visual stimulation and recovery.ConclusionThese findings have several implications, among them that neuronal firing itself is not a major source of heat release in the brain and that there is an aftermath of brain activation that lasts minutes before returning to baseline conditions.
Highlights
Temperature plays a fundamental role for the proper functioning of the brain
We studied Tbr in the visual cortex of 20 normal subjects serially with a wide temporal window under different states including rest, activation and recovery by a visual stimulationMagnetic Resonance Spectroscopy Thermometry combined approach
Visual cortex mean baseline Tbr was higher than mean body temperature (37.38 vs 36.60, P
Summary
Changes in cerebral blood flow (CBF), changes in the temperature of PLOS ONE | DOI:10.1371/journal.pone.0127314. Post-Activation Brain Warming incoming arterial blood, and extensive heat exchange between the activated and the surrounding brain tissue [1] are the major factors contributing to brain temperature (Tbr) regulation during functional stimulation when CBF, brain metabolism as well as oxygen extraction increase. Mechanisms that reduce heat together with others that increase local heat are at work. Under these conditions is difficult to predict the net heat balance resulting in Tbr because these changes do not occur simultaneously. Based on the Pennes’ bioheat approach [2], temperature distribution in the human brain is predicted to vary inherently within the brain tissue and that activation influences the local temperature according to the anatomical site [3]
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