Post-Activation Brain Warming: A 1-H Mrs Thermometry Study

PurposeTemperature plays a fundamental role for the proper functioning of the brain. However, there are only fragmentary data on brain temperature (T-br) and its regulation under different physiological conditions.MethodsWe studied T-br 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 T-br in a control region, the centrum semiovale, under the same conditions.ResultsVisual cortex mean baseline T-br was higher than mean body temperature (37.38 vs 36.60, P< 0.001). During activation T-br remained unchanged at first and then showed a small decrease (-0.20 C degrees) around the baseline value. After the end of activation T-br increased consistently (+ 0.60 C degrees) and then returned to baseline values after some minutes. Centrum semiovale T-br 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.