Task 4 - Cerebral cortex Flashcards
Types of cytoarchitecture in the cortex
- Neocortex: Most of the human cortex is neocortex, has six layers
- Paleocortex: The part of the cortex in the olfactory bulb that has only 3 layers
- Archicortex: The part of the cortex in the hippocampus that has only 3 layers
- Allocortex: Paleocortex + archicortex
The 6 layers of the neocortex
- Molecular layer
- External granular layer
- External pyramidal layer
- Internal granular layer
- Internal pyramidal layer
- Multiform layer
Holistic vs. localization paradigm of brain function
A debate in the dawn of neurophysiology between the following 2 positions:
Holistic: The entire cortex has roles in the execution of any brain function
Localization: Functions are localizable to specific cortical areas
Brodmann’s map of the human cortex
- A drawing of a lateral & medial view of a human brain, displaying the segregation of the cerebral cortex into 43 cortical areas belonging to 11 regions
- Each of these areas is characterized by a particular cytoarchitecture
Tracing techniques
- Used to map connectivity between brain areas.
- One must delineate the location of the injection site of a chemical tracer and slice up the brain to create microscopic preparations that allow visualizing the amount of substances that has arrived in each slice
Advantages of the tracing techniques
One learns specifically where the input to a field comes from and where it sends its output to
Disadvantages of the tracing technique
- The injection site never perfectly matches the field of interest
- Substances often spread into adjacent fields
- Substance affects all neurons in the injection site with no discrimination for any segregated patch structure that may exist
Axoplasmic transport
The process responsible for movement of organelles (mitochondria), lipids, proteins, synaptic vesicles, and other parts of the cell membranes to and from the soma down to the axon to the synapses and back to the soma
Types of white matter tacts
- Association fibers: Fibers that interconnect cortical areas within 1 cerebral hemisphere.
- Commisural fibers: Fibers that connect cortical areas in one hemisphere with the same areas in the other hemisphere, enabling coordination of cortical activity across the hemispheres.
- Projection fibers: Fibers that travel to or from cortex to connect it with more caudal CNS areas (thalamus, basal ganglia, brainstem, spinal cord).
Types of association fibers
- Short association fibers
- Long assocation fibers
Types of commisural fibers
-
Corpus callosum: Connects the 2 parietal lobes, and the 2 posterior frontal
lobes with each other -
Anterior commisure: A small bundle of fibers that connects the anterior temporal
lobes & the olfactory bulbs with each other. - Posterior commisure: Located in the midbrain, connecting the 2 pretectal nuclei.
Projection fibers
- Anterior limb
- Posterior limb
- Genu
Which global architecture does the brain have?
Graph-based studies of the brain have shown that the brain has a small-world architecture, which is characterized by dense local clustering of connections between neighboring nodes, due to the existence of relatively few long-range connections
Characteristics of small-world architecture
- The brain contains hubs which can be seperated into two types:
1. Provincial/regional hub
2. Connector hub (which links different subnetworks)
Default mode network (DMN)
A network of brain regions that are consistently active when an individual is not focused on the external environment or engaged in specific tasks.
Key regions:
1. Medial Prefrontal Cortex (mPFC)
2. Posterior Cingulate Cortex (PCC)
