Attention and memory dysfunction after traumatic brain injury: cholinergicmechanisms, sensory gating, and a hypothesis for further investigation

Traumatic brain injury (TBI) is a common occurrence, with a rate of nearly 400000 new injuries per year. Cognitive and emotional disturbances may beco me persistent and disabling for many injured persons, and frequently involv e symptomatic impairment in attention and memory. Impairments in attention and memory have been well characterized in TBI, and are likely related to d isruption of cholinergic functioning in the hippocampus. Additionally, dist urbances in this neurotransmitter system may also account for disturbances in sensory gating and discriminative attention in this population. The elec troencephalographic P50 waveform of the evoked response to paired auditory stimuli may provide a physiologic market of impaired sensory gating among T BI survivors. The first application of this recording assessment to the TBI population is reported. Preliminary findings in three cases are presented, and the interpretation of impaired sensory gating in this population is di scussed. Given the impact of TBI on cholinergic systems, the effects of cho linergic augmentation on attention and memory impairment, and the availabil ity of an electrophysiologic marker of cholinergic dysfunction responsive t o cholinergic agents, a testable cholinergic hypothesis for investigation a nd treatment of these patients is proposed.