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Corollary discharge signals play an important role in monitoring self-generat ed movements to guarantee spatial constancy. Recent work in macaques suggests th at the thalamus conveys corollary discharge information of upcoming saccades pas sing from the superior colliculus to the frontal eye field. The present study ai med to investigate the involvement of the thalamus in humans by assessing the ef fect of thalamic lesions on the processing of corollary discharge information. T hirteen patiente with selective thalamic lesions and 13 healthy age-matched con trol subjects performed a saccadic double-step task in which reiino-spatial di ssonance was induced, i.e. the retinal vector of the second target and the movem ent vector of the second saccade were different. Thus, the subjects could not re ly on retinal information alone, but had to use corollary discharge information to correctly perform the s econd saccade. The amplitudes of first and second saccades were significantly sm aller to patients than in controls. Five thalamic lesion patients showed unilate ral deficits in using corollary discharge information, as revealed by asymmetrie s compared with the other patients and controls. Three patients with lateral tha lamic lesions including the ventrolateral nucleus (VL) were impaired contralater ally to the side of damage and one patient with a lesion in the mediodorsal thal amus (MD) was impaired ipsilaterally to the lesion. The largest asymmetry was fo und in a patient with a bilateral thalamic lesion. The results provide evidence for a thalamic involvement in the processing of corollary discharge information to humans, with a potential role of both the VL and MD nuclei.
Corollary discharge signals play an important role in monitoring self-generat ed movements to guarantee spatial constancy. Recent work in macaques suggests th at the thalamus conveys corollary discharge information of upcoming saccades pas sing from the superior colliculus to the frontal eye field. The present study ai med to investigate the involvement of the thalamus in humans by assessing the ef fect of thalamic lesions on the processing of corollary discharge information. T hirteen patiente with selective thalamic lesions and 13 healthy age-matched con trol subjects performed a saccadic double-step task in the reiino-spatial di ssonance was induced, ie the retinal vector of the second target and the movem ent vector of the second saccade were different. Thus, the subjects could not re ly on retinal information alone, but had to use corollary discharge information to correctly perform the s econd saccade. The amplitudes of first and second saccades were significantly sm aller to patients than in controls. Five thalamic lesion patients showed unilate ral deficits in using corollary discharge information, as revealed by asymmetrie s compared with the other patients and controls. Three patients with lateral tha lamic lesions including the ventrolateral nucleus (VL) were impaired contralater ally to the side of damage and one patient with a lesion in the mediodorsal thal amus (MD) was impaired ipsilaterally to the lesion. The largest asymmetry was fo und in a patient with a bilateral thalamic lesion. The results provide evidence for a thalamic involvement in the processing of corollary discharge information to humans, with a potential role of both the VL and MD nuclei.