Journal Article

V1 activity during feedforward and early feedback processing is necessary for both conscious and unconscious motion perception

Revonsuo, Antti, Koivisto, Mika, Hurme, Mikko, Railo, Henry

2019

Overview

The study of blindsight has revealed a seminal dissociation between conscious vision and visually guided behavior: some patients who are blind due to V1 lesions seem to be able to employ unconscious visual information in their behavior. The standard assumption is that these findings generalize to the neurologically healthy. We tested whether unconscious processing of motion is possible without the contribution of V1 in neurologically healthy participants by disturbing activity in V1 using transcranial magnetic stimulation (TMS). Unconscious processing was measured with redundant target effect (RTE), a phenomenon where participants respond faster to two stimuli than to one stimulus, when the task is just to respond as fast as possible when one stimulus or two simultaneous stimuli are presented. We measured the RTE caused by a motion stimulus. V1 activity was interfered with different stimulus onset asynchronies (SOA) to test whether TMS delivered in a specific time window suppresses conscious perception (participant reports seeing only one of the two stimuli) but does not affect unconscious processing (RTE). We observed that at each SOA, when TMS suppressed conscious perception of the stimulus, the RTE was also eliminated. However, when visibility of the redundant target was suppressed with a visual mask, we found unconscious processing of motion. This suggests that unconscious processing of motion depends on V1 in neurologically healthy humans. We conclude that the neural mechanisms that enable motion processing in blindsight are modulated by neuroplastic changes in connectivity between subcortical areas and the visual cortex after the V1 lesion. Neurologically healthy observers cannot process motion unconsciously without functioning of V1. •Blindsight patients can unconsciously process motion despite a V1 lesion.•How well this generalizes to neurologically healthy humans remains open.•We manipulated stimulus visibility using V1 TMS or metacontrast masking.•Unconscious processing was only observed with metacontrast masking.•Unconscious processing of motion depends on V1 in neurologically healthy humans.

• Publisher: Elsevier Inc,Elsevier Limited
• Subject: Adult / Blindness / Blindness - physiopathology / Blindsight / Consciousness - physiology / Consciousness and Cognitive Neuroscience / controlled study / ego development / Feedback / Female / human / human experiment / Humans / Kognitiv neurovetenskap och filosofi / Male / Middle Aged / Motion detection / Motion perception / Motion Perception - physiology / movement perception / Neural networks / Redundant target effect / stimulus / Studies / Temporal perception / TMS / Transcranial Magnetic Stimulation / Unconscious vision / Unconsciousness / visibility / Visual cortex / Visual Cortex - physiology / Visual perception / Young Adult