Low response variability in simultaneously recorded retinal, thalamic, and cortical neurons

Area of Science:

• Neuroscience
• Visual System Physiology
• Computational Neuroscience

Background:

• Cortical cell responses to repeated stimuli are often highly variable.
• Retinal cells exhibit lower response variability compared to cortical cells.
• Understanding response reliability across successive visual processing stages is crucial.

Purpose of the Study:

• To investigate and compare spike count variability in retinal ganglion cells (RGCs), lateral geniculate nucleus (LGN) relay cells, and primary visual cortex simple cells.
• To determine the factors contributing to response reliability differences across these visual pathway stages.
• To re-evaluate the perceived variability of cortical cell responses.

Main Methods:

• Simultaneous electrophysiological recordings of visual responses from RGCs, LGN cells, and V1 simple cells in cats.
• Analysis of spike count variability relative to a Poisson process.
• Quantification of absolute and relative refractory periods at each stage.

Main Results:

• Spike count variability was lower than Poisson at all recorded stages (retina, LGN, cortex).
• Variability increased progressively from RGCs to LGN to cortex.
• Absolute and relative refractory periods were found to largely explain the observed reliability at each stage.

Conclusions:

• Cortical cell responses can be more reliable than commonly assumed.
• Differences in reliability across the visual pathway are explained by decreasing firing rates and shorter refractory periods from retina to cortex.
• The findings provide insights into the neural mechanisms underlying reliable visual information processing.