Figure 2.

Basal ganglia mechanism for automatic gaze orienting to stably high-valued objects. A, Basal ganglia circuit controlling gaze orienting. This scheme represents the circuit mediated by the caudate tail (CDt), but equivalent circuits are present for the caudate head (CDh) or caudate body (CDb). CDt receives inputs from visual cortical areas, whereas CDh and CDb receive inputs from the frontal and parietal cortical areas. Arrows indicate excitatory connections (or effects). Lines with circular dots indicate inhibitory connections. Unbroken and broken lines indicate direct and indirect connections, respectively. B, An SNr neuron encoding stable values of visual objects. Shown superimposed are the neuron's responses to 60 high-valued objects (red) and 60 low-valued objects (blue). These objects (i.e., fractals) are shown in C. Before the recording, the monkey had experienced these objects with a large or small reward consistently for >5 daily learning sessions but had not seen them for >3 d. Firing rates (shown by spike density functions) are aligned on the onset of the object (time 0). The object disappeared at 400 ms. The neuron was located in the caudal-lateral part of SNr, which receives concentrated inputs from CDt (not CDh or CDb) and projected its axon to SC (as shown by antidromic activation). D, Free viewing task. On each trial, four fractal objects were presented simultaneously and the monkey freely looked at them. Examples of saccade trajectories are shown by white lines. The monkey tended to look at stably high-valued objects (denoted as H). No reward was delivered during or after free viewing. A, Reproduced with permission from Hikosaka et al. (2013). B, C, Reproduced from Yasuda et al. (2012).