Auditory saccade impairment after central thalamus lesions

Visual and auditory saccades were studied in three patients with an isolate d lesion located in the central thalamus. Visual saccades proved to be norm al, whereas for auditory stimuli, the amplitude of the first saccade was as ymmetric: saccades ipsilateral to the lesion were significantly smaller tha n those directed to the contralateral side. The patients were able to make a corrective saccade and hence to improve gain and to decrease gain asymmet ry. It is suggested that patients were able to localise auditory targets co rrectly, but did not correctly take into account eye position during the sa ccade, probably as a consequence of an inaccurate efference copy (corollary discharge) signal. The findings are in keeping with the hypothesis that th e central thalamus deals with saccades that are based on extraretinal signa ls.