Neuropathological and Behavioral Effects of Mild Traumatic Brain Injury at High Altitude

Area of Science:

• Neuroscience
• High-altitude physiology
• Traumatic brain injury research

Background:

• High altitude (HA) exposure can impair cognitive function and alter neurovascularization.
• Mild traumatic brain injury (mTBI) causes similar neuropathological and behavioral changes.
• The combined effects of HA and mTBI on the brain are not well understood.

Purpose of the Study:

• To investigate the neuropathological and behavioral consequences of mTBI in mice exposed to chronic high altitude.
• To characterize the impact of HA-mTBI on neuroimaging markers and cognitive function.

Main Methods:

• Mice were exposed to simulated high altitude (5000 m) or sea level for 12 weeks.
• Mice underwent either mTBI (repetitive closed head injuries) or sham procedures.
• Neuroimaging techniques including MRI, DTI, and PET scans were used, alongside behavioral tests for memory recall.

Main Results:

• High altitude and mTBI combined led to reduced cerebral blood flow, global brain volume, and altered glucose metabolism in specific brain regions.
• MRI and DTI revealed white matter alterations in the corpus callosum and caudate nucleus.
• Distinct imaging signatures correlated with hippocampal integrity and thalamocortical connectivity, potentially impacting spatial memory and behavior.

Conclusions:

• Chronic high altitude exposure and mTBI interact to induce complex neuropathological changes, including region-dependent white matter and gray matter alterations.
• Cerebral glucose metabolism is impaired, with specific patterns of reduction and increase observed.
• Despite significant structural and metabolic changes, a synergistic decline in behavioral outcomes was not observed, indicating a dissociation between injury and function.