Recent Research Results
Neurons in the deepest part of the neocortex alter their functions with sensory experience
February 21, 2023
The mammalian cerebral cortex consists of six layers, with distinct roles in information processing. At the bottom of the neocortex, on the boundary between the gray matter and white matter, there is a thin sheet of neurons called L6b. L6b neurons are thought to be remnants of subplate neurons that transiently form neural circuits during perinatal development and guide cortical maturation. Most subplate neurons undergo cell death, while some survive. However, the functional properties of L6b/surviving subplate neurons remain largely unknown. We found that L6b/ surviving subplate neurons in the primary visual cortex (V1) exhibit sensory responses and experience-dependent plasticity in juvenile mice.
We performed functional measurements of surviving subplate neurons by using two-photon Ca2+ imaging with post hoc tissue clearing and 3D immunohistochemistry of a subplate neuron marker. Most of the recorded L6b neurons expressed a subplate neuron marker and they demonstrated broadly tuned visual response properties (Figure 1).
Then we examined whether L6b neurons exhibit experience-dependent plasticity. To this end, we used ocular dominance plasticity as an experimental model. In this model, if one eye is occluded for several days during the sensitive period in juvenile animals, neurons in V1 lose their response to the deprived eye. By using chronic two-photon imaging of visual responses from the same neurons, we found that L6b neurons exhibited ocular dominance plasticity (Figure 2).
These results indicate that surviving subplate neurons exhibit sensory responses and experience-dependent plasticity.
Yoneda T, Hayashi K, and Yoshimura Y (2023) Experience-dependent functional plasticity and visual response selectivity of surviving subplate neurons in the mouse visual cortex. PNAS. DOI: 10.1073/pnas.2217011120
Figure 1
(A) A fixed brain before (left) and after (right) tissue clearing. (B) L6b neurons from in vivo two-photon imaging (left) and the same areas from a cleared brain (right). (C) Most of the recorded L6b neurons expressed CTGF which is a subplate neuron marker. Foxp2 is a marker of cortico-thalamic neurons. (D) An example of a volumetric image of cleared brain.
We performed chronic two-photon imaging of visual responses from the same L6b neurons. Neuron images and their visual responses of chronically recorded L6b neurons. Significant visual response of right eye stimuli decreased after right eye deprivation.