Recurrent circuitry is required to stabilize piriform cortex odor representations across brain states

Area of Science:

• Neuroscience
• Computational Neuroscience
• Sensory Processing

Background:

• Pattern completion is crucial for memory retrieval from incomplete cues.
• Recurrent neural networks are theoretically proposed to implement pattern completion via attractor dynamics.
• The precise role of recurrent circuitry in stabilizing neural representations across different brain states remains incompletely understood.

Purpose of the Study:

• To investigate the role of recurrent connections in the piriform cortex for stabilizing odor representations.
• To determine if piriform cortex exhibits attractor dynamics and if recurrent circuitry supports this.
• To elucidate the auto-associative function of the piriform cortex in sensory processing.

Main Methods:

• In vivo electrophysiological recordings in head-fixed mice.
• Administration of ketamine/xylazine anesthesia to alter brain states.
• Perturbation of recurrent circuitry in the piriform cortex.
• Analysis of odor-evoked responses and neural activity patterns.

Main Results:

• Odor responses in the olfactory bulb degraded under anesthesia, while piriform cortex responses remained robust.
• Recurrent connections in the piriform cortex were essential for stabilizing odor representations across anesthesia-induced state changes.
• Piriform cortex odor representations demonstrated attractor dynamics both within and across trials.
• Elimination of recurrent circuitry abolished these attractor dynamics.

Conclusions:

• Recurrently-connected piriform cortical populations are critical for stabilizing sensory representations against degraded inputs.
• The piriform cortex, supported by its recurrent circuitry, functions as an auto-associative network for pattern completion.
• These findings highlight the importance of recurrent circuits in maintaining robust neural representations for memory and sensory processing.