Cerebral Cortex II

LSU KIN 4571 Exam 2

neocortex (isocortex)

outermost layers of the cerebral cortex

granular (stellate)

• star-shaped

• afferent projections (input; info coming into the brain stops here)

• within the cortex

Pyramidal

• pyramid-shaped

• efferent projections (output; info leaving the brain starts here)

Horizontal Laminar and Vertical Columnar

How is the neocortex organized?

Horizontal Laminar Organization

Six Layers

1. Molecular

2. External Granular

3. External Pyramidal

4. Internal Granular

5. Internal Pyramidal

6. Multiform (Fusiform)

Molecular (I)

mostly dendrites and axons from inner cells

External Granular (II)

small granules and pyramidal neurons

External Pyramidal (III)

small/medium pyramidal neurons

Internal Granular (IV)

closely packed granular neurons

Internal Pyramidal (V)

large pyramidal neurons

Multiform (Fusiform) (VI)

many cell types

IV; II

Most afferents terminate in ___ and some in ___.

V; II; III

Most efferents arise from ___ with some coming from ___ and ___ and go to the spinal cord and brain stem.

VI; Thalamus

Info from ___ goes to the ___.

Vertical Columnar Organization

cytoarchitecture/chunks of neurons with similar function

• functional organization (homunculus)

  • divergent pathways

  • good for parallel processing

injury and learning

Vertical Columnar Organization changes with what? (The more you use it, the larger the column)

Subcortical (projection fibers)

impulses to/from subcortical areas (thalamus, brain stem, S.C.); NOT on the surface of the cortex

Association

connect neurons within a hemisphere (Ex. synergists share “rich” connections); both do the same thing so they communicate

Commissural

connect neurons to the contralateral hemisphere (Ex. Corpus callosum and commissures); left side talks to right side

Cell Migration

• In to out

• Thalamic sensory neurons attach to cortical neurons

  • sensory + motor = sensorimotor integration

  • dependent on genetic factors

VI

What layer migrates first during cell migration?

before

Cell migration is complete _______ birth.

Neural Exuberance

“all over the place”; projections to many areas

• pro: redundancy

• con: lacks precision

• No “pathways” in the beginning

• The more you do a task and use a “pathway”, the easier it will be to do the task

Critical Periods

an immature state of neural areas or projections (Ex. starting to use a spoon)

Transformation

general connections become specific

Regressive Events

Cell death and pruning are examples of _________.

50%

During cell death, we lose about _____ of neurons during development.

axonal and synaptic retraction

examples of pruning effective synapses

Neural Darwinism

• “competition”

• forms neural networks

• “survival of the fittest”

• might lead to regressive events without this

• use it or lose it