Nonuniform spike count shared variability in the mouse early visual system

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Sensory stimuli are encoded by the collective activity of neuronal populations in the mammalian cortex.
• Trial-to-trial variability in neural responses, particularly non-independent variability between neurons, can modulate the amount of sensory information conveyed by population activity.
• The structure, sources, and impact of shared variability at various timescales on visual information processing remain incompletely understood.

Purpose of the Study:

• To investigate the structure and functional implications of shared neural variability in the primary visual cortex (V1) and lateral geniculate nucleus (dLGN) of awake mice.
• To determine how shared variability at different timescales affects the coding of visual information.
• To compare shared variability under natural visual drive versus artificial electrical stimulation.

Main Methods:

• Simultaneous recording of tens to hundreds of single neurons in V1 and dLGN using Neuropixels probes in awake mice.
• Measurement of global and layer-specific shared spike count variability across timescales (millisecond to second).
• Comparison of shared variability during visually-evoked responses versus electrically-evoked cortical responses.

Main Results:

• Shared variability in neural populations was found to be low-dimensional.
• Depending on the timescale, shared variability could facilitate synergistic or redundant coding.
• Computational decoders could leverage shared variability to improve information transmission at fine timescales (< 10 msec).
• Shared variability had a negligible impact on information at longer timescales (100 msec) in V1.

Conclusions:

• Information regarding visual inputs is present within shared neural variability, but it is not uniformly distributed.
• Shared variability's impact on visual information coding is timescale-dependent and varies across neural ensembles within V1.