Separate functional subnetworks of excitatory neurons show preference to periodic and random sound structures

Abstract

Auditory cortex (ACX) neurons are sensitive to spectro-temporal sound patterns and violations in patterns induced by rare stimuli embedded within streams of sounds. We investigate the auditory cortical representation of repeated presentations of sequences of sounds with standard stimuli(common) with an embedded deviant (rare) stimulus in two conditions-Periodic (Fixed deviant position) or Random (Random deviant position), using extracellular single-unit and 2-photon Ca+2 imaging recordings in Layer 2/3 neurons of the mouse ACX. In the population average, responses increased over repetitions in the Random-condition and were suppressed or did not change in the Periodic-condition, showing irregularity preference. A subset of neurons also showed the opposite behavior, indicating regularity preference. Pairwise noise correlations were higher in Random-condition over Periodic-condition, suggesting the role of recurrent connections. 2-photon Ca+2 imaging of excitatory (EX) and parvalbumin-positive (PV) and somatostatin-positive (SOM) inhibitory neurons, showed different categories of adaptation or change in response over repetitions (categorized by the sign of the slope of change) as observed with single units. However, the examination of functional connectivity between pairs of neurons of different categories showed that EX-PV connections behaved opposite to the EX-EX and EX-SOM pairs that show more functional connections outside category in Random-condition than Periodic-condition. Finally considering Regularity preference, Irregularity preference and no preference categories, showed that EX-EX and EX-SOM connections to be in largely separate functional subnetworks with the different preferences, while EX-PV connections were more spread. Thus separate subnetworks could underlie the coding of periodic and random sound sequences.

Social experience dependent plasticity of mouse song selectivity without that of song components

“…Such integration likely involves very long time scales of adaptation known in A1 77,78 , long time constant recursive connections and inhibitory inputs 79 . Previous work 52 has looked into very long time scale adaptation 78 of entire sound sequences and change in their representation over time from repeated presentations and show recurrence in EXNs and SOM to play a role. Here we find that optogenetic silencing of SOM INNs paired with sequence presentations alter sequence selectivity as with social experience with largely no change in relative selectivity of single neurons to syllables.…”

“…Thus the single syllables were encoded differentially in a natural context than in a random context -specifically a higher response was generally elicited in SN than in SR, except for the H syllable. The differences could be an effect of stimulus specific adaptation SSA, 51,50,52 due to repeated presentations of syllables more so in SN (for example H in SN15 and SN16). Absence of such long repeats of H in SR could potentially explain the lower response rates to H in SN compared to SR (Fig.…”