Alterations in visual and auditory processing in hemispatial neglect: an evoked potential follow-up study

Hemispatial neglect is common after cerebrovascular stroke in the right hemisphere. Cortical electrophysiological studies, especially investigations of both visual and auditory processing in subjects with neglect are sparse. Our purpose was to assess whether and to which extent subjects with neglect may show impairments in both visual and auditory processing. Thereby, we assessed the evolution of changes in sensory processing and neglect symptoms over a 6 month follow-up period. Twenty-one stroke subjects with hemispatial neglect were studied at baseline, 3 weeks later and at 6 months follow-up. At enrollment, 12 patients were in Acute/subacute and 9 were in the chronic stage of stroke. Visual and auditory evoked potentials (EP) were elicited with unilateral stimulations and electrophysiologic data were registered with high-density EEG. Primary visual and auditory cortex activations seen in EP components were analyzed at three time points in order to detect alterations. Both sensory modalities revealed differences between hemispheres in processing stimuli coming from a unilateral source. Amplitudes of visual and auditory EP components elicited by left-sided stimuli were smaller compared to those elicited by right-sided stimuli in the Acute/subacute group. The behavioral neglect was more severe in those who had smaller EP amplitudes (e.g. EP amplitude after the right auditory stimulus was significantly associated with total behavioral neglect score, r=0.57). The main hemispheric differences diminished by the follow-up 6 months later along with the decreasing severity of neglect in the Acute/subacute group.