The local and long‐range input landscape of inhibitory neurons in mouse auditory cortex

Abstract

Roughly 20% of the neurons in the mouse cortex are inhibitory interneurons (INs). Of these, the three major subtypes are parvalbumin (PV), somatostatin (SST), and vasoactive intestinal polypeptide (VIP) expressing neurons. We used monosynaptic rabies tracing to compare the presynaptic input landscape onto these three IN subtypes in the mouse primary auditory cortex (A1). We compared both local patterns of monosynaptic inputs as well as long‐range input patterns. The local monosynaptic input landscape to SST neurons was more widespread as compared to PV and VIP neurons. The brain‐wide input landscape was rich and heterogeneous with >40 brain regions connecting to all the three INs subtypes from both hemispheres. The general pattern of the long‐range input landscape was similar among the groups of INs. Nevertheless, a few differences could be identified. At low resolution, the proportion of local versus long‐range inputs was smaller for PV neurons. At mesoscale resolution, we found fewer inputs from temporal association area to VIP INs, and more inputs to SST neurons from basal forebrain and lateral amygdala. Our work can be used as a resource for a quantitative comparison of the location and level of inputs impinging onto discrete populations of neurons in mouse A1.

Direct piriform-to-auditory cortical projections shape auditory-olfactory integration

“…Because most long-range intra-telencephalic projections are excitatory (Shepherd, 2013;Harris and Shepherd, 2015), odor enhancement may be due to excitation of ACx by direct Pir input, whereas odor suppression may arise from indirect input via local circuitry or via other brain regions. In our anterograde tracing experiments identifying Pir-recipient neurons, we observed that the TeA receives a large amount of Pir input (Fig 2 ), a finding that is consistent with previous studies (Tasaka et al, 2020(Tasaka et al, , 2023 and suggests that TeA is a region that might relay Pir input to ACx, ultimately affecting ACx activity. Together these results pave the way for future studies to disentangle the relative contributions of direct Pir input versus indirect pathways to auditory-olfactory integration in ACx, and how the Pir-to-ACx pathway interacts with other multimodal and higher-order brain circuity.…”