Multiscale functional imaging in V1 and cortical correlates of apparent motion

In vivo intracellular electrophysiology offers the unique possibility of listening to the “synaptic rumor” of the cortical network captured by the recording electrode in a single V1 cell. The analysis of synaptic echoes evoked during sensory processing is used to reconstruct the distribution of input sources in visual space and time. It allows us to infer, in the cortical space, the dynamics of the effective input network afferent to the recorded cell. We have applied this method to demonstrate the propagation of visually evoked activity through lateral (and possibly feedback) connectivity in the primary cortex of higher mammals. This approach, based on functional synaptic imaging, is compared here with a real-time functional network imaging technique, based on the use of voltage-sensitive fluorescent dyes. The former method gives access to microscopic convergence processes during synaptic integration in a single neuron, while the latter describes the macroscopic divergence process at the neuronal map level. The joint application of the two techniques, which address two different scales of integration, is used to elucidate the cortical origin of low-level (non-attentive) binding processes participating in the emergence of illusory motion percepts predicted by the psychological Gestalt theory.