Layer V Neurons in Mouse Cortex Projecting to Different Targets Have Distinct Physiological Properties

Abstract

Hattox AM, Nelson SB. Layer V neurons in mouse cortex projecting to different targets have distinct physiological properties. J Neurophysiol 98: 3330 -3340, 2007. First published September 26, 2007 doi:10.1152/jn.00397.2007. Layer V pyramidal neurons are anatomically and physiologically heterogeneous and project to multiple intracortical and subcortical targets. However, because most physiological studies of layer V pyramidal neurons have been carried out on unidentified cells, we know little about how anatomical and physiological properties relate to subcortical projection site. Here we combine neuroanatomical tract tracing with whole cell recordings in mouse somatosensory cortex to test whether neurons with the same projection target form discrete subpopulations and whether they have stereotyped physiological properties. Our findings indicate that corticothalamic and -trigeminal neurons are two largely nonoverlapping subpopulations, whereas callosal and corticostriatal neurons overlap extensively. The morphology as well as the intrinsic membrane and firing properties of corticothalamic and corticotrigeminal neurons differ from those of callosal and corticostriatal neurons. In addition, we find that each class of projection neuron exhibits a unique compliment of hyperpolarizing and depolarizing afterpotentials that further suggests that cortical neurons with different subcortical targets are distinct from one another.

Optogenetic neuronal stimulation promotes functional recovery after stroke

“…These increases in neurotrophins, possibly resulting from the interactions between the two hemispheres after stimulation, further confirms the involvement of the contralesional cortex in the stroke recovery process (6,42,43). It is also possible that the increases in neurotrophins are related to the contralesional limb movement during M1 stimulation (Movie S1), as this movement can send signals back to contralesional and ipsilesional cortices (44,45). BDNF, the most extensively studied neurotrophin, has been shown to promote poststroke recovery and enhance axonal and dendritic sprouting (10,11), which are critical repair/plasticity processes for recovery.…”

Blindsight: The Anatomical and Functional Post-Injury Neural Plasticity of The Visual System

“…The cortical thalamic neurons belong to this type. The most represented cell population in our study is localized in V layer and it shows an aspect characteristic of cortical thalamic projections, as documented by many Authors [19,20].…”

The Fezf2–Ctip2 genetic pathway regulates the fate choice of subcortical projection neurons in the developing cerebral cortex

“…Recording from individual layer 5 neurons and dendritic analysis in Fezf2 ϩ/Ϫ or Fezf2 Ϫ/Ϫ mice were performed as described in ref. 15. Details are available in SI Methods.…”

“…Projection neurons in layer 5 can be categorized into several electrophysiological classes that correlate with their projection patterns. Callosal projection neurons exhibit strong spike frequency adaptation in response to intracellular current injections, whereas many neurons that extend axons to the spinal cord, thalamus, or trigeminal nucleus fire trains of single action potentials without adaptation, and corticotectal neurons fire in bursts (15). To ascertain whether Fezf2 regulates the physiological fates of layer 5 neurons, we blinded each animal's genotype and recorded from individual layer 5 neurons in brain slices from Fezf2 ϩ/Ϫ and Fezf2 Ϫ/Ϫ mice.…”

“…Callosal and subcortical projection neurons also exhibit distinctive electrophysiological properties. Callosal neurons show strong spike frequency adaptation in response to intracellular current injection, whereas subcortically projecting cells fire actions potentials without adaptation (2,10,(13)(14)(15). Finally, these classes of neurons differ in dendritic morphology: subcortical projection neurons extend apical dendrites into layer 1, whereas those of callosal neurons are shorter (2,10,13,14,16).…”