Abstract
To produce consistent sensory perception, neurons must maintain stable representations of sensory input. However, neurons in many regions exhibit progressive drift across days. Longitudinal studies have found stable responses to artificial stimuli across sessions in visual areas, but it is unclear whether this stability extends to naturalistic stimuli. We performed chronic 2-photon imaging of mouse V1 populations to directly compare the representational stability of artificial versus naturalistic visual stimuli over weeks. Responses to gratings were highly stable across sessions. However, neural responses to naturalistic movies exhibited progressive representational drift across sessions. Differential drift was present across cortical layers, in inhibitory interneurons, and could not be explained by differential response strength or higher order stimulus statistics. However, representational drift was accompanied by similar differential changes in local population correlation structure. These results suggest representational stability in V1 is stimulus-dependent and may relate to differences in preexisting circuit architecture of co-tuned neurons.
Highlights
To produce consistent sensory perception, neurons must maintain stable representations of sensory input
To ensure our selected imaging fields solely contained V1 neurons, we used a widefield microscope to determine visual area boundaries through established retinotopic mapping procedures[53,54,55] (Fig. 1b, “Methods”). Visual landmarks such as blood vessels were used to identify and align the 2-photon imaging field on a given recording session, and small differences in the alignment of the horizontal plane were corrected in postprocessing using nonrigid image registration software[9]
Here we investigated the extent to which representational drift exists in populations of individual neurons through a comparison of neural responses to artificial (PDG) and naturalistic (MOV) visual stimuli in the primary visual cortex of awake mice over many weeks
Summary
To produce consistent sensory perception, neurons must maintain stable representations of sensory input. Multiphoton imaging sacrifices temporal resolution afforded by precise spike measurement, its high spatial resolution mitigates sampling biases and reduces ambiguity in neuronal identification during chronic measurements, allowing for longitudinal studies of large neuronal populations[11,17,18] These developments have produced the opportunity to expand the investigation of cortical stability to other brain areas over longer time periods. While single-neuron representational drift has been theorized to play a role in learning in areas like the motor cortex and hippocampus[3,8,26,27,28], recent evidence has demonstrated its presence in odor-evoked responses in the mouse olfactory cortex[29] It is less clear what purpose would be served by instability in early sensory areas, where the circuitry is tasked with reliably representing external sensory information on a single exposure. The evidence of stable stimulus representation in the face of this variability has led to the suggestion that the functional connectivity of the sensory cortex may grant it robustness to noise while maintaining the ability to undergo experience-dependent plasticity[17]
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