Synaptic wiring motifs in posterior parietal cortex support decision-making

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• The posterior parietal cortex (PPC) shows choice-selective neural activity during perceptual decision-making.
• The synaptic mechanisms underlying this selective activity in the PPC remain largely unknown.

Purpose of the Study:

• To investigate the relationship between synaptic connectivity and selective neural activity in the PPC.
• To understand how neural circuit motifs contribute to decision-making computations.

Main Methods:

• Combined virtual-reality behavioral tasks with in vivo two-photon calcium imaging.
• Utilized high-throughput electron microscopy to map synaptic connections.
• Developed and analyzed neural-circuit models to simulate circuit function.

Main Results:

• Identified an 'opponent inhibition' motif: excitatory neurons target inhibitory interneurons with matching selectivity, which then inhibit pyramidal neurons with opposite selectivity.
• This motif was observed across neurons with activity peaks in different task epochs.
• Circuit models demonstrated that opponent inhibition amplifies selective inputs, improving trial-type information encoding and generating choice-specific sequential activity.

Conclusions:

• Synaptic connectivity, specifically the opponent inhibition motif, plays a crucial role in generating choice-selective activity in the PPC.
• This circuit mechanism supports learned decision-making by enhancing information encoding and temporal dynamics.