Activity in the visual cortex is modulated by top-down attention locked to reaction time

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Visual Perception

Background:

• The relationship between subjective perception and objective neural activity is a key area in neuroscience.
• Understanding how the brain processes visual changes and the role of attention is crucial for cognitive function.

Purpose of the Study:

• To investigate the correlation between perceptual experience and hemodynamic activity in the visual cortex during a change detection task.
• To determine if non-sensory evoked hemodynamic signals are localized and related to spatial attention.

Main Methods:

• Functional magnetic resonance imaging (fMRI) to measure blood oxygenation level-dependent (BOLD) signals in the visual cortex.
• A change detection task where participants indicated perceived changes in visual stimuli.
• Control experiments to differentiate sensory-evoked activity from non-sensory evoked activity.

Main Results:

• A significant increase in the BOLD signal was observed in the primary and extrastriate visual cortex whenever a change was perceived, irrespective of accuracy.
• This non-sensory-evoked activity was spatially localized to the perceived change location.
• The hemodynamic response failed to occur when changes were missed or attention was diverted.
• Non-sensory signal latency correlated linearly with reaction time, while amplitude was contrast-independent.

Conclusions:

• Hemodynamic activity in the visual cortex is modulated by the perception of change, not solely by sensory input.
• The findings support the hypothesis that top-down spatial attention mediates this non-sensory hemodynamic signal, distinct from awareness itself.
• This neural signal is a marker for the spatial focus of attention during visual processing.