Stimulus duration modulates awareness-dependent brain activation in the fusiform gyrus independently of task-relevance

An fMRI study used an inattentional blindness design to separate conscious face perception from stimulus duration. Fifty-six participants performed a distractor task while background line stimuli, sometimes containing an abstract face, appeared for 500 or 1000 ms. Awareness was manipulated by informing some participants about the face. Awareness-related activation in the fusiform gyrus increased and broadened with longer stimulus duration, with no such effects elsewhere. Functional connectivity between the right inferior frontal junction and right fusiform gyrus depended on awareness and duration. Longer stimuli also increased responses in parietal and visual areas, including V1, regardless of awareness. The authors suggest that activation in stimulus-related visual areas is coupled to the duration of conscious perception.

Study at a glance

Abstract

Conscious perception in daily life encompasses continuous experience and persistent percepts of visual inputs. However, the temporal dimension of consciousness, specifically neural mechanisms maintaining sustained conscious percepts over time, remains comparatively understudied. Many studies feature either brief stimulus durations or prolonged supraliminal stimuli without inducing an unconscious comparison condition. This approach prevents investigation of whether activation in specific brain regions corresponds to the maintenance of a conscious percept. In this functional magnetic resonance imaging (fMRI) study, we used an inattentional blindness design to manipulate awareness across two stimulus durations, independent of report or other task-related confounds. Participants (N=56) performed a visual distractor task while line stimuli were presented in the background, sometimes containing an abstract human face for either 500 or 1000 ms. Conscious face perception was manipulated through prior information about the face, with informed participants consciously perceiving the face while uninformed p articipants remained unaware of it. Awareness-related activation in the fusiform gyrus(FG) exhibited modulation by stimulus duration based on an increased and broader spatial extent of activation during prolonged versus short conditions.No awareness-related effects were found in other brain areas.However, significant functional connectivity between the right inferior frontal junction and the right FG depending on stimulus awareness and duration was found. Furthermore, longer stimuli,compared to shorter ones, led to increased responses in parietal and visual cortical areas, including V1, regardless of stimulus awareness. These findings suggest that specifically activation in stimulus-related visual areas is coupled to the duration of conscious visual perception.