Memory and perceptual deficits during electrical stimulation in the left and right thalamus and parietal subcortex

Mechanisms for perception and memory were probed by electrical stimulation via chronic electrodes in the human thalamus. Stimulation within the left pulvinar nucleus induced transient dysphasia and a retrograde loss in recent memory for verbal memoranda. In contrast, comparable stimulation of the right pulvinar failed to disrupt verbal behavior and, instead, disabled the mechanism for discrimination and recognition of complex visual patterns. The findings suggest that an asymmetry in the functional organization of linguistic and nonverbal processes appears to exist at the level of the lateral thalamus. The hypothesis is advanced that the pulvinar scans incoming sensory traces and searches long-term memory registers for appropriate cues and labels.