Similar to human OA, we found that the reach amplitude reduction by PRR inactivation was significantly smaller in the foveal than extrafoveal condition for both monkeys (Figure 3C; t test, p < 0.01, Experimental Procedures). Thus, so far, we reproduced three major OA symptoms: (1) misreaching for visual targets in the peripheral visual field, (2) no deficits in

saccades, and (3) reduced reaching errors in the central visual field. These results support our prediction that PRR can be a neural substrate responsible for the OA misreaching. The reaching impairment by PRR inactivation was not limited to memory-guided reaches; in the task under the extrafoveal condition in the above section, the monkeys selleck screening library immediately reached to the visible target without a memory period, yet significant hypometria was caused by PRR inactivation (t test, p < 0.01 for both monkeys). This result shows that misreaching is not due to spatial memory being impaired. It is also notable that the reaching impairment was not limited to reaches whose goals are directly cued by illuminating the target location; instead, misreaching manifested even when the goal was indirectly inferred from a symbol after a learned association rule between the

symbols and target locations (Figure S2). This result is Tyrosine Kinase Inhibitor Library consistent with the finding that PRR neurons encode symbolically cued reach goals similarly to directly cued reach goals (Hwang and Andersen, 2012). Therefore,

the hypometria reflects a general deficit of reach goal for representation as opposed to a selective impairment of direct visuomotor transformation. Human OA patients with unilateral lesions typically show stronger impairment for reaches to targets in the contralesional field, consistent with the lateralized spatial representation in human PPC (Blangero et al., 2010; Perenin and Vighetto, 1988). To compare, we computed the average inactivation effect for the contralesional versus ipsilesional targets, respectively. The inactivation effect was computed as the percentage reduction of the reach amplitude from the control baseline amplitude (Experimental Procedures). Although reach amplitudes in both monkeys were significantly affected in both hemifields (t test, p < 0.01), the effect was stronger for the contralesional field for monkey Y, but it was stronger for the ipsilesional field for monkey G (Figures 2C, 2D, and 4A). This puzzling difference between the two monkeys was resolved when we examined the reach direction represented by the neurons in the local area that we inactivated in each monkey separately. Figure 4B displays the histogram of the preferred direction of the spiking units recorded in a proximal area (within ∼1 mm) from the inactivation cannula prior to the inactivation experiment during the memory-guided reach task.