Abstract
Across sensory systems, complex spatio-temporal patterns of neural activity arise following the onset (ON) and offset (OFF) of stimuli. While ON responses have been widely studied, the mechanisms generating OFF responses in cortical areas have so far not been fully elucidated. We examine here the hypothesis that OFF responses are single-cell signatures of recurrent interactions at the network level. To test this hypothesis, we performed population analyses of two-photon calcium recordings in the auditory cortex of awake mice listening to auditory stimuli, and compared them to linear single-cell and network models. While the single-cell model explained some prominent features of the data, it could not capture the structure across stimuli and trials. In contrast, the network model accounted for the low-dimensional organization of population responses and their global structure across stimuli, where distinct stimuli activated mostly orthogonal dimensions in the neural state-space.
Highlights
Neural responses within the sensory cortices are inherently transient
For each subsampling of stimuli, we reduced the dimensionality of the responses using principal component analysis (PCA), and kept the dominant dimensions that accounted for 90% of the variance. (E) Examples of the OFF responses to distinct stimuli of two different auditory cortical neurons
We showed that strong OFF responses observed in auditory cortical neurons form transiently amplified trajectories that encode individual stimuli within low-dimensional subspaces
Summary
Neural responses within the sensory cortices are inherently transient. The transient onset component has been long considered the dominant feature of auditory responses and has been extensively studied across the auditory pathway (Liu et al, 2019b; Kuwada and Batra, 1999; Grothe et al, 1992; Guo and Burkard, 2002; Yu et al, 2004; Heil, 1997a; Heil, 1997b), with respect to its neurophysiological basis and perceptual meaning (Phillips et al, 2002). Due to less evidence of OFF-responsive neurons in anaesthetized animals, OFF cortical responses have received comparably less attention. OFF responses have been observed in awake animals throughout the auditory pathway, and in the mouse AC they arise in 30–70% of the responsive neurons (Scholl et al, 2010; Keller et al, 2018; Joachimsthaler et al, 2014; Liu et al, 2019a; Sollini et al, 2018)
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