Simultaneous mnemonic and predictive representations in the auditory cortex

Abstract

Recent studies have shown that stimulus history can be decoded via the use of broadband sensory impulses to reactivate mnemonic representations. It has also been shown that predictive mechanisms in the auditory system demonstrate similar tonotopic organization of neural activity as that elicited by the perceived stimuli. However, it remains unclear if the mnemonic and predictive information can be decoded from cortical activity simultaneously and from overlapping neural populations. Here, we recorded neural activity using electrocorticography (ECoG) in the auditory cortex of anesthetized rats while exposed to repeated stimulus sequences, where events within the sequence were occasionally replaced with a broadband noise burst or omitted entirely. We show that both stimulus history and predicted stimuli can be decoded from neural responses to broadband impulse at overlapping latencies but linked to largely independent neural populations. We also demonstrate that predictive representations are learned over the course of stimulation at two distinct time scales, reflected in two dissociable time windows of neural activity. These results establish a valuable tool for investigating the neural mechanisms of passive sequence learning, memory encoding, and prediction mechanisms within a single paradigm, and provide novel evidence for learning predictive representations even under anaesthesia.

Hierarchical Deviant Processing in Auditory Cortex of Awake Mice

“…In addition, an earlier study (Chen et al, 2015) using two-photon guided patch-clamp recordings in the primary auditory cortex of anesthetized mice suggested that the early component (0-100 ms after tone onset) of the neural response to a deviant sound may reflect neural adaptation, while the late component (200 – 400 ms after onset) may reflect deviance detection. However, while rodents can detect single deviants (Ulanovsky et al, 2003; Yaron et al, 2012) and change in acoustic features (An et al, 2021; Yang et al, 2021), to the best of our knowledge there is no direct evidence for MMR signaling in complex sound sequences, although rats can perform sequence chunking if extensively trained (Luo et al, 2021) or if the sequences are repetitive enough (Cappotto et al, 2021). It therefore remains elusive whether the primary auditory cortex, or higher order regions, can also encode deviance in more complex stimulus patterns which are more similar to natural sound sequences.…”