Organization of the cerebral cortex Flashcards
Cerebral cortex structure
Cerebral cortex consists of two folded sheets of gray matter (cell bodies) organized into 2 hemispheres (left & right)
- The surface of the cortex has become increasingly more convoluted with evolutionary development. → high surface area to volume ratio → efficient packaging.
- Gyri: the raised surface of the cortex
- Sulci: the dips or folds of the cortex
Lateral surface of each hemisphere is divided into 4 lobes: Frontal, temporal, parietal, occipital lobe and the insular cortex is an island of cortex lies buried underneath the temporal lobe.
General:
- Approx. 16 billion neurons;
- vertically organized in horizontal layers;
- radially organized in vertical hypercolumns and microcolumns
Cortical layers
have specific functions: movement in the motor cortex, vision in the visual cortex
3 mm thick,
organized in different layers with different densities at different part/site/region of the cortex → 6 layers in neocortex, mesocortex (cingulate gyrus and insula), and the allocortex (primary olfactory cortex and hippocampus)
Brodmann´´s area
regions of cortex defined by the relative distribution of cell types across cortical layers (cytoarchitecture)–> one of the most influential ways of dividing up the cerebral cortex up to ~ 52 areas
Regions divided by function (only to be used for primary sensory and motor areas) e.g. Brodmann areas 17 and 6 → termed the primary visual cortex and the primary motor cortex.
Cortical sheet
The whole cortical sheet is made of a collection of anatomical fundamental columnar units called microcolumns (~50 µm of diameter)
cortical minicolumn
a vertical column through the cortical layers of the brain. Neurons within the microcolumn “receive common inputs, have common outputs, are interconnected, and may well constitute a fundamental computational unit of the cerebral cortex” → anatomical fundamental columnar units
Cortical column (macro/hypercolumn)
is a group of neurons in the cortex of the brain that can be successively penetrated by a probe inserted perpendicularly to the cortical surface, and which have nearly identical receptive fields
E.g. if a single cell within a column responds to touch on the palm of the left hand, then other cells within the same column will also respond to that stimulus. → functional fundamental units
Map-like organization of cortical areas
The arrangement of the cortical columns within a certain cortical area reveals a map-like organization
E.g. the organization of sensory maps in the cortex reflects that of the corresponding sensing organs
E.g. Retinotopy = topographic map / is the mapping of visual input from the retina to neurons, particularly those neurons within the visual stream e.g. in the primary visual cortex.
Self-organizing maps
a type of artificial neural network that is trained using unsupervised learning to produce a low dimensional, typically two dimensional representation of a higher dimensional data set while preserving the topological structure of the data.
Using competitive learning rather than the error-correction learning (e.g., backpropagation with gradient descent)
Cortical connectivity
The different cell types in the cerebral cortex and their occurrence in the different layers enable to analyze the cortical connectivity.
Each cortical layer is connected with all other layers and with itself.
Not every connection is realized equally frequently
Canonical cortical circuit
Show the main information flow within the cortex layer
Arrows represent connectivity within nodes, ordered spatially according to their anatomical localization. Curved arrows illustrate intrinsic (excitatory and inhibitory) connectivity.
→ able to present the hierarchy of cortical areas with the canonical cortical circuit
Which brain regions important to control the overall generation of movement?
basal ganglia is very important to control the overall generation of movement.
the cerebellum is important for dexterity and smooth execution of movement, to acquire new motor skills
supplementary motor area is one of the important motor areas of cerebral cortex,
Broca’s Area is one of the important motor areas of the cerebral cortex,
