title: Laminarly orthogonal excitation of fast-spiking and low-threshold-spiking interneurons in mouse motor cortex.
abstract: In motor cortex, long-range output to subcortical motor circuits depends on excitatory and inhibitory inputs converging on projection neurons in layers 5A/B. How interneurons interconnect with these projection neurons, and whether these microcircuits are interneuron and/or projection specific, is unclear. We found that fast-spiking interneurons received strong intralaminar (horizontal) excitation from pyramidal neurons in layers 5A/B including corticostriatal and corticospinal neurons, implicating them in mediating disynaptic recurrent, feedforward, and feedback inhibition within and across the two projection classes. Low-threshold-spiking (LTS) interneurons were instead strongly excited by descending interlaminar (vertical) input from layer 2/3 pyramidal neurons, implicating them in mediating disynaptic feedforward inhibition to both projection classes. Furthermore, in a novel pattern, lower layer 2/3 preferentially excited interneurons in one layer (5A/LTS) and excitatory neurons in another (5B/corticospinal). Thus, these inhibitory microcircuits in mouse motor cortex follow an orderly arrangement that is laminarly orthogonalized by interneuron-specific, projection-nonspecific connectivity.
authors.affiliation: Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
authors.forename: Alfonso J
authors.initials: AJ
authors.lastname: Apicella
authors.forename: Ian R
authors.initials: IR
authors.lastname: Wickersham
authors.forename: H Sebastian
authors.initials: HS
authors.lastname: Seung
authors.forename: Gordon M G
authors.initials: GM
authors.lastname: Shepherd
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D003342:Corpus Striatum / Q000502:physiology*; D005260:Female; D007395:Interneurons / Q000502:physiology*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009044:Motor Cortex / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D056347:Neuroanatomical Tract-Tracing Techniques / Q000379:methods; D017966:Pyramidal Cells / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology*