Motion contrast in primary visual cortex: a direct comparison of single neuron and population encoding

Area of Science:

• Neuroscience
• Visual Cortex Research
• Sensory Processing

Background:

• Classical receptive field (CRF) activity in the primary visual cortex is modulated by external stimuli.
• This modulation, primarily described via firing rates, is crucial for processing features like motion contrast.
• Surround influences on neural activity can manifest as variations in firing rate, pairwise spiking, or local field coherence.

Purpose of the Study:

• To investigate the co-existence and integration of different neural signatures of surround modulation.
• To compare how firing rates and phase-locking to low-gamma frequency reflect motion contrast in single cells and neuronal assemblies.
• To determine if different neural signatures represent distinct aspects of surround visual information.

Main Methods:

• Recorded spiking and Local Field Potential (LFP) activity in anesthetized cat primary visual cortex.
• Utilized natural-like scenes with motion contrast in the surround of CRFs.
• Analyzed single-cell firing rates and neuronal assembly phase-locking to low-gamma frequency.

Main Results:

• Motion contrast modulated both firing rates and phase-locking, but in semi-independent neuronal populations.
• Neuronal assembly activation correlated with single-neuron firing rates.
• Assembly phase relations, unlike firing rates, reflected the direction of surround motion and were affected by interhemispheric connection deactivation.

Conclusions:

• Motion contrast is represented by complementary and superimposed neural signatures in the primary visual cortex.
• Different neuronal populations and neural codes (rate vs. phase-locking) may process distinct aspects of surround visual information.
• Assembly phase relations are particularly sensitive to motion direction and interhemispheric interactions.