1. Cortical circuits
Domina Petric, MD

2. Origins
Cerebral cortex develops from the outer walls of telencephalic vesicles.
During embrionic life human brain has twice as many neurons than after birth and later.

3. Neuroblasts Neuroblasts differentiate into neurons and glia.
Progenitor cell can become stem cell.
Stem cell can reenter the cell cycle at some point across the lifespan.

4. Cortical plate
Migrations of the neuroblasts from the inner region near the ventricles to the outer regions where cerebral cortex will be built.
Developing cortex is the cortical plate.

5. Migration
Neuroblasts migrate from the ventricular zone to the cortical plate along a scaffold provided by radial glial cells.

6. Layer 4 of the cerebral cortex
Layer 4 is the target of first order thalamic nuclei.
It is called the thalamic recipient zone.
Layer 4 is populated by smaller, stellate cells so it is called also the granular layer of the cerebral cortex.

7. The thalamic recipient zone! Two pyramidal layers
The outermost layer.
Two
granular
layers
The thalamic recipient zone!
Two
pyramidal
layers
Rich of synaptic connections.
The innermost layer.

8. Inputs
Cells in the layer 4 interconnect with each other, but also send major inputs to the upper layers of the cerebral cortex: layers 2 and 3.

9. Information pathways from layers 2 and 3
horizontal pathway, from one region of the layer to a neighboring region
pathway through the corpus callosum to the corresponding cortical area in the opposite hemisphere

10. Infragranular layers
Infragranular layers (layers 5 and 6) can give rise to descending projections.
Layer 5 cells can project to the basal ganglia, brainstem and even to the spinal cord for certain regions of the cerebral cortex.

11. Infragranular layers Cells in layer 6 project back to the thalamus.
Layer 6 cells also provide a return input to layer 4.

12. Canonical microcircuit of the cerebral cortex
Functions:
amplification of the signal
new computations
broad communication (from one cortical column to the next, from one cortical area to another, from cortical areas to distant parts of the brain)
Amplification
Computation
Communication

13. Cortical cytoarchitecture
Betz cells in layer 5 are the largest neurons in the cerebral cortex.
Inner granular layer (4) is very prominent in the sensory cortex and it is diminished in its thickness and density of cells in the motor cortex.

14. paleocortex (pyriform cortex)
Medial temporal lobe
paleocortex (pyriform cortex)
archicortex (hippocampus)

15. Literature
Leonard E. White, PhD, Duke University