Orientation and Distance Dependence of Pairwise Correlation in Macaque V1

Neuronal responses to sensory stimuli are not independent from each other. For instance, trial-to-trial fluctuations in response strength are shared between neurons. Understanding the mechanisms that underlie these pairwise correlation is critical for determining their role in encoding sensory information. Our goal was to measure the effects of different orientation preferences and electrode recording distances on the correlation of paired neurons under different task difficulty. We simultaneously recorded single-unit activities from V1 neuronal pairs with non-overlapping receptive fields separating in different millimeter scales (up to 7.5 mm), while rhesus monkeys performed a detection task under two levels of task difficulty. We found that correlation of distant neurons is dependent on distances, but not sensitive to differences of orientation preference and task difficulty. These findings suggest that correlation of distant neurons likely involves feedback from extra-striate cortex. The circuit mechanism they imply provides new constraints on the functional connectivity that correlation may play in visual processing.