Sharp wave‐associated activity patterns of cortical neurons in the mouse piriform cortex

• Published in: The European journal of neuroscience 2018-11, Vol.48 (10), p.3246-3254
• Main Authors: Katori, Kazuki, Manabe, Hiroyuki, Nakashima, Ai, Dunfu, Eer, Sasaki, Takuya, Ikegaya, Yuji, Takeuchi, Haruki
• Format: Article
• Language: English
• Subjects: Activity patterns; Cortex (olfactory); Coyotes; Ethyl carbamate; Hippocampus; memory replay; multi‐unit recording; Neuroplasticity; Odor; olfactory cortex sharp wave; olfactory piriform cortex; Paleocortex; Piriform cortex; Sleep; spontaneous neural activity; Synaptic plasticity
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/ejn.14099

The olfactory piriform cortex (PC) is thought to participate in olfactory associative memory. Like the hippocampus, which is essential for episodic memory, it belongs to an evolutionally conserved paleocortex and comprises a three‐layered cortical structure. During slow‐wave sleep, the olfactory PC becomes less responsive to external odor stimuli and instead displays sharp wave (SPW) activity similar to that observed in the hippocampus. Neural activity patterns during hippocampal SPW have been intensively studied in terms of memory consolidation; however, little is known about the activity patterns of olfactory cortical neurons during olfactory cortex sharp waves (OC‐SPWs). In this study, we recorded multi‐unit neural activities in the anterior PC in urethane‐anesthetized mice. We found that the activity patterns of olfactory cortical neurons during OC‐SPWs were non‐randomly organized. Individual olfactory cortical neurons varied in the timings of their peak firing rates during OC‐SPW events. Moreover, specific pairs of olfactory cortical neurons were more frequently activated together than expected by chance. On the basis of these observations, we speculate that coordinated activation of specific subsets of olfactory cortical neurons repeats during OC‐SPWs, thereby facilitating synaptic plasticity underlying the consolidation of olfactory associative memories. We found that the neural activities during sharp waves in the piriform cortex are not random but actually coordinated. This finding might give some suggestions to the function of the piriform cortex as an association cortex.