Crowding alters the spatial distribution of attention modulation in human primary visual cortex

Area of Science:

• Neuroscience
• Visual Perception
• Cognitive Psychology

Background:

• The crowding effect, a reduction in target visibility due to surrounding distractors, is debated.
• Existing theories propose either pre-attentive lateral inhibition or coarse spatial attention resolution.

Purpose of the Study:

• To investigate the neural mechanisms underlying the crowding effect.
• To differentiate between lateral inhibition and attention-based explanations for crowding.

Main Methods:

• High-resolution functional magnetic resonance imaging (fMRI) was employed.
• V1 (primary visual cortex) responses to a target were measured under attended and unattended conditions with and without distractors.
• Distractor configurations varied to assess crowding severity.

Main Results:

• Cortical responses to the target were unaffected by distractors when unattended, ruling out pre-attentive inhibition.
• Attention modulation spread beyond the target and distractor locations in a severe crowding configuration (radial axis).
• This attentional spread was absent in a weak crowding configuration (circumference), supporting coarse spatial attention.

Conclusions:

• Crowding is primarily explained by the coarse spatial resolution of attention, not pre-attentive lateral inhibition.
• Attention dynamically modulates neural responses based on distractor configuration.
• Findings highlight the role of attention in visual perception and object recognition.