My laboratory is interested in understanding the underlying cellular and physiological mechanism of mild traumatic brain injuries (mTBIs). Our work has established that spreading depolarizations are initiated in closed skull concussion-like injuries in mice. Spreading depolarizations are massive events in the brain that are associated with a propagating wave of complete tissue depolarization. The depolarization is associated with a huge drop in the extracellular potential and suppression of cortical activity as shown below. Recovery from spreading depolarizations are metabolically challenging and in compromised tissue can result in cell death and tissue loss.
Our laboratory was the first to directly record the electrophysiological responses of spreading depolarizations following a closed skull injury. The traces above show the electrophysiological responses of a spreading depolarization. The top trace is the large extracellular potential shift known as the "DC shift". The middle trace is the high frequency activity of the cortex. Along with the DC shift the high frequency is suppressed and eventually recovers within a few minutes. The bottom trace is the power (voltage squared) of the high frequency activity.
Spreading depolarizations are also associated with dynamic changes in the cerebral blood flow. In mice the spreading wave of depolarization is also associated with a reduction in cerebral blood flow. Our laboratory uses laser speckle contrast imaging (shown above) to monitor the cerebral blood flow. The dotted lines indicate the leading edge of the spreading depolarization immediately following a concussion-like injury.
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