Abstract
Blindsight is the residual visuo-motor ability without subjective awareness observed after lesions of the primary visual cortex (V1). Various visual functions are retained, however, instrumental visual associative learning remains to be investigated. Here we examined the secondary reinforcing properties of visual cues presented to the hemianopic field of macaque monkeys with unilateral V1 lesions. Our aim was to test the potential role of visual pathways bypassing V1 in reinforcing visual instrumental learning. When learning the location of a hidden area in an oculomotor search task, conditioned visual cues presented to the lesion-affected hemifield operated as an effective secondary reinforcer. We noted that not only the hidden area location, but also the vector of the saccade entering the target area was reinforced. Importantly, when the visual reinforcement signal was presented in the lesion-affected field, the monkeys continued searching, as opposed to stopping when the cue was presented in the intact field. This suggests the monkeys were less confident that the target location had been discovered when the reinforcement cue was presented in the affected field. These results indicate that the visual signals mediated by the residual visual pathways after V1 lesions can access fundamental reinforcement mechanisms but with impaired visual awareness.
Highlights
Blindsight is the residual visuo-motor ability without subjective awareness observed after lesions of the primary visual cortex (V1)
The purpose of the present investigation was to test whether visual systems, other than the primary visual cortex, can use the appearance of secondary reinforcing visual cues for the acquisition of novel instrumental behavior
The main findings of the study were: (1) The monkeys were able to discover the location of the hidden area, even when the secondary reinforcing stimulus was presented in V1 lesion-affected visual field
Summary
Blindsight is the residual visuo-motor ability without subjective awareness observed after lesions of the primary visual cortex (V1). To test whether instrumental learning is preserved in blindsight subjects, we used a conditioned visual stimulus presented in the lesion-affected field to reinforce the responses required to discover the location of a hidden area on blank screen (an area without any visual indication). In monkeys with unilateral V1 lesions saccadic eye movements that moved their gaze into the hidden target area were reinforced (“hidden area search task”) This task was similar to that used by Chukoskie et al.[19] and well characterized by a reinforcement-learning model that maintained and updated a reward map of locations. Reward the secondary reinforcing stimuli was presented to the lesion affected visual field, provides further evidence that novel instrumental responses can be acquired in the absence of normal visual awareness
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