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Abstract:
The so-called perception-action model (PAM) postulates two visual systems. A dorsal pathway from early visual areas to posterior parietal cortex processes information for the control of action whereas a ventral pathway from early visual areas to inferotemporal cortex serves the transformation of visual information for perception. One postulation of the PAM was that the ventral pathway plays an essential role for the guidance of delayed movements to memorised targets. Unfortunately, this assertion was only tested in patient DF who not only suffered damage to the ventral pathways but also considerable damage to the dorsal system bilaterally. We investigated a stroke patient (HWS) with a unilateral lesion in the ventral pathway who showed lateralised symptoms of visual agnosia. HWS showed accurate immediate reaching towards a visible peripheral target. However, introducing a delay between stimulus presentation and motor response, HWS was noticeably less accurate in his contralesional hemisphere compared to age- matched healthy controls. This observation not only confirms previous findings but allows for a clear attribution of a deficit in delayed reaching to the ventral stream since HWS suffered from a first-time unilateral stroke resulting in a circumscribed lesion to the occipital-temporal cortex in the right hemisphere.
