In the free-looking task (as part of the stable value procedure) that induced automatic saccades (Figure 1D), caudate tail neurons showed presaccadic activity that was significantly stronger to preferred value objects than to nonpreferred value objects (Figure 7B, bottom). Such
presaccadic activity was absent in caudate head neurons (Figure 7B, top). The caudate tail-specific activity preceding automatic saccades was confirmed using a free-viewing procedure (Figure S5) in which four objects, chosen SKI-606 mouse randomly on each trial, were presented simultaneously and the monkey looked at them with no reward consequence. To further test the flexible-stable dichotomy hypothesis, we selectively inactivated the caudate head or the caudate tail by injecting a GABAA receptor agonist, muscimol (Figure 8A). The inactivation of the caudate head disrupted the initiation of saccades in the flexible value task (which we call controlled saccades) (Figure 8B, top). Before the inactivation, the target acquisition time on single object trials was significantly shorter for high-valued objects than for low-valued objects (Figure 1B, Figure S6B, left). This bias of controlled saccades decreased significantly during the caudate head inactivation
(Figure 8B, top) but Selleckchem PF-06463922 only for contralateral saccades (from 69.7 ms to 20.4 ms; p < 0.01, paired t test). The bias decrease was largely due to earlier saccades to low-valued objects (Figure S6B, top). The caudate head inactivation also disrupted the choice of the high-valued objects in the flexible value task (Figure S7C, top), again only for contralateral saccades (p < 0.05, paired t test), when four, not two, objects were used. However, the caudate head inactivation did not affect saccades in the stable value procedure using either the free-looking task (Figure 8C,
aminophylline top) or the free-viewing procedure (Figure S8B). In contrast, the inactivation of the caudate tail specifically disrupted the initiation of saccades in the stable value task (free-looking task) (Figure 8C, bottom). Before the inactivation, the likelihood of saccades to the presented object (which we call automatic saccades) was higher for high-valued objects than for low-valued objects (Figure 1D, Figure S6D, left). This bias of automatic saccades disappeared during the caudate tail inactivation (Figure 8C, bottom) but only for contralateral saccades (from 19.9% to −1.2%; p < 0.01, paired t test). The bias decrease was largely due to more frequent saccades to low-valued objects (Figure S6D, bottom). Among the saccades made to the presented object, there was no change in latency.