Spike synchrony reveals emergence of proto-objects in visual cortex

Area of Science:

• Neuroscience
• Computational Neuroscience
• Visual Perception

Background:

• Neurons in the early visual cortex process elemental features.
• The mechanism for organizing these features into perceptual objects remains unclear.
• Previous theories suggested spiking synchrony encodes feature grouping (binding-by-synchrony), but evidence is mixed.

Purpose of the Study:

• To investigate an alternative hypothesis: intrinsic feedback circuits group features into "proto-objects" by enhancing neural responses.
• To test if synchrony occurs specifically between neurons within the same feedback grouping circuit.
• To explore the role of synchrony and feedback circuits in object-based processing and selective attention.

Main Methods:

• Recorded neural activity from macaque visual cortex.
• Utilized border-ownership selectivity to identify neurons within the same feedback grouping circuit.
• Analyzed neural synchrony in relation to feature binding and a selective attention task.

Main Results:

• Found synchrony specifically between neurons belonging to the same feedback grouping circuit, supporting the grouping hypothesis.
• Observed synchrony with both attended and ignored objects, suggesting automatic grouping.
• Synchrony was weakly elevated with binding, arguing against it as the primary code for binding.
• Feedback grouping circuits modulated response strength, indicating a role in encoding binding.

Conclusions:

• Intrinsic feedback circuits, rather than solely spiking synchrony, play a crucial role in grouping visual features into proto-objects.
• Feedback circuits encode binding by modulating feature neuron responses, offering a novel coding mechanism for perception.
• The findings challenge the binding-by-synchrony theory and propose a new framework for understanding early visual object formation.