Cortical sensory evoked potentials and communicative forebrain functions.

Cortical evoked potentials were measured to visual, auditory and somatosensory stimuli in 20 subjects with serious neurodevelopmental impairments due to various etiologies. The results were compared with behavioral observations to find out whether the absence/presence of the responses corresponded to the level of social functioning. No cortical evoked potentials were elicited in two subjects, responses to the stimulation of one modality were missing in three subjects (retinal b-waves and brainstem auditory and somatosensory evoked potentials were, however, preserved in them). No communicative behavior was observed in subjects with absent responses. Ten subjects had marked deviations in the evoked potentials, the behavioral observations in them, ranging from no communication to sentenced speech. Five subjects had normal response patterns and they showed a great variety of communicative skills, including speech. The results support the view that bilateral loss of cortical somatosensory, visual, and auditory evoked potentials is a sign of loss of neural substrates of communication.