Lateral entorhinal cortex afferents reconfigure the activity in piriform cortex circuits

Area of Science:

• Neuroscience
• Olfactory System Research
• Spatial Navigation

Background:

• Odor representations in the piriform cortex (PCx) encode spatial context.
• The brain origins and integration mechanisms of this spatial information into the PCx remain unclear.

Purpose of the Study:

• Investigate the lateral entorhinal cortex (LEC) as a source of spatial context influencing PCx microcircuit and olfactory responses.
• Elucidate how LEC inputs modulate PCx neuronal activity and interact with olfactory sensory inputs.

Main Methods:

• Patch-clamp recordings in mouse brain slices targeting superficial (SP) and deep (DP) pyramidal neurons, and parvalbumin (PV) and somatostatin (SOM) inhibitory interneurons.
• Optogenetic stimulation of excitatory LEC projections to assess their impact on PCx activity.
• Examined the interaction between LEC inputs and lateral olfactory tract (LOT) sensory signals.

Main Results:

• LEC inputs are heterogeneously distributed in the PCx, with stronger excitatory currents in SP and PV neurons.
• LEC inputs differentially modulate inhibitory circuits, activating PV and suppressing SOM interneurons.
• Simultaneous LEC and LOT activation enhances SP and DP neuron spiking, sharpening DP responses via LEC-induced inhibition of delayed LOT-evoked spikes.

Conclusions:

• LEC afferents reconfigure PCx activity by modulating neuronal excitability and inhibitory circuits.
• LEC inputs activate PV interneurons, suggesting a mechanism to inhibit recurrent activity and regulate olfactory responses.
• Findings contribute to understanding how the PCx integrates olfactory and nonolfactory information to form odor object representations.