PT  - JOURNAL ARTICLE
AU  - Adrian G. Bondy
AU  - Bruce G. Cumming
TI  - Feedback Determines the Structure of Correlated Variability in Visual Cortex
AID  - 10.1101/086256
DP  - 2016 Jan 01
TA  - bioRxiv
PG  - 086256
4099  - http://biorxiv.org/content/early/2016/12/23/086256.short
4100  - http://biorxiv.org/content/early/2016/12/23/086256.full
AB  - The variable spiking discharge of sensory neurons in response to a fixed stimulus tends to be weakly correlated (spike-count correlation, rsc). This is widely thought to reflect stochastic noise in shared sensory afferents, in which case it places strict limits on the fidelity of sensory coding. However, it may also be generated by changes over time in feedback from higher-order brain regions. We tested this alternative directly by measuring spiking activity in populations of primary visual cortical (V1) neurons in rhesus monkeys performing different visual discrimination tasks on the same set of visual inputs. We found that the structure of rsc (the way rsc varied with neuronal stimulus preference) changed dramatically with task instruction, despite identical retinal input. This demonstrates that rsc structure primarily reflects feedback dynamics engaged by the task, not noise in sensory afferents. As a consequence, previous analyses of how rsc constrains sensory processing need not apply. Furthermore, these results imply that decision-related activity in sensory neurons is a consequence of task-dependent changes in feedback.