We report data examining the relations between endogenous allocation of visual attention and effects of motor-preparation on attention. We tested a patient with a spatial bias in perceptual report following damage to the left inferior parietal lobe and superior temporal gyrus. Previously we have shown that the spatial bias in report can be reduced when a movement is planned to where a target falls in the contralesional field, while the bias is exacerbated when a movement is planned to the ipsilesional side (Kitadono and Humphreys, 2007, Cognitive Neuropsychology, 24). Here we pitted the effects of planning a movement to the contra- or ipsilesional side against the effects of endogenous visual attention, manipulated by varying the probability of where a target would fall. In a no-movement baseline, there was better identification of contralesional targets when there was a good likelihood of targets appearing on the contralesional side (the 20-80 and 50-50 conditions) compared with when targets had a low probability of occurring there (the 80-20 condition). This sensitivity to target probability interacted with the effects of planning a movement to the contra- or ipsilesional side. When the target had a good probability of falling in the contralesional field (the 20-80 and 50-50 conditions), planning a movement to the ipsilesional side disrupted contralesional report. When there was a high probability of an ipsilesional target (the 80-20 condition), planning a movement to a congruent side improved contralesional report. The results indicate that effects of endogenous attention and of motor-based attention influence a common system controlling visual orienting
