Top-down modulation of human early visual cortex after stimulus offset supports successful postcued report

Area of Science:

• Neuroscience
• Cognitive Science
• Visual Perception

Background:

• Modulations in early visual processing are crucial for conscious perception.
• Existing research primarily examines influences before or during visual stimuli.
• Emerging theories suggest late top-down influences after stimulus offset also impact perception.

Purpose of the Study:

• To investigate the role of top-down influences after visual stimulus termination on conscious perception.
• To directly test if post-stimulus auditory cues modulate early visual cortex activity related to conscious report.

Main Methods:

• Functional magnetic resonance imaging (fMRI) study utilizing a postcued report procedure.
• Auditory postcues were presented at different time intervals (200 ms and 1000 ms) after visual stimulus offset.
• Behavioral performance (target report accuracy) and brain activity in early visual cortex (V1, V2) were measured.

Main Results:

• Auditory postcues presented 200 ms after stimulus offset enhanced target-specific signals in V1 and V2.
• This enhancement correlated with accurate conscious reporting of the visual target.
• Postcues presented 1000 ms later showed reduced correlation with conscious report accuracy.

Conclusions:

• Top-down modulation in early visual cortex within a few hundred milliseconds after stimulus offset is critical for conscious visual report.
• This suggests that visual stimulus representation remains malleable and subject to top-down influences shortly after the stimulus disappears.
• Findings support theories emphasizing the role of late, top-down processes in constructing conscious visual perception.