The study of neurons in V1 when with no visual stimuli is present showed that the underlying cortical circuitry is characterized by the fact that neurons with similar orientation selectivity are coupled across the cortex.
Interestingly, the patterns of spontaneous activity in V1 are often highly correlated with activity elicited by specific visual stimuli, suggesting that ongoing spontaneous activity reflects dynamic switching between a set of intrinsic cortical states that are also present during stimulus-driven activity. These intrinsic states seem to correspond closely to the orientation maps observed during visual stimulation.
Overall, these findings suggest, that background activity in V1 is not just a background state that the cortex relates to and rather a constantly ready, dynamic state, that is highly correlated with its functional properties.
Source: Priebe, N.J. (2016) ‘Mechanisms of Orientation Selectivity in the Primary Visual Cortex’, Annual Review of Vision Science, 2(1), pp. 85–107. Available at: https://doi.org/10.1146/annurev-vision-111815-114456.