Retinal oscillations carry visual information to cortex

TL;DR

This study demonstrates that retinal oscillations encode visual information through two multiplexed channels in thalamic spike trains, with one conveying local image changes and the other transmitting global scene features via gamma oscillations.

Contribution

It reveals that retinal oscillations facilitate dual-channel encoding of visual information in thalamic relay cells, highlighting a multiplexed neural coding mechanism.

Findings

Thalamic spike trains encode information in two frequency bands.

Gamma oscillations carry global visual scene information.

Oscillations can transmit more information than firing rate alone.

Abstract

Thalamic relay cells fire action potentials that transmit information from retina to cortex. The amount of information that spike trains encode is usually estimated from the precision of spike timing with respect to the stimulus. Sensory input, however, is only one factor that influences neural activity. For example, intrinsic dynamics, such as oscillations of networks of neurons, also modulate firing pattern. Here, we asked if retinal oscillations might help to convey information to neurons downstream. Specifically, we made whole-cell recordings from relay cells to reveal retinal inputs (EPSPs) and thalamic outputs (spikes) and analyzed these events with information theory. Our results show that thalamic spike trains operate as two multiplexed channels. One channel, which occupies a low frequency band (<30 Hz), is encoded by average firing rate with respect to the stimulus and carries information about local changes in the image over time. The other operates in the gamma frequency band (40-80 Hz) and is encoded by spike time relative to the retinal oscillations. Because these oscillations involve extensive areas of the retina, it is likely that the second channel transmits information about global features of the visual scene. At times, the second channel conveyed even more information than the first.