Task 4 - Cerebral cortex Flashcards
The 5 different lobes
Frontal, parietal, temporal, occipital and limbic
Neocortex
The part of human cortex that has 6 layers. Most of the human cortex is neocortex.
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
2 major cell types in the cortex
Pyramidal neurons: Found in layers III & V, their axons project out of the cortex to other regions of the brain & spinal cord, making them the main output cells
Granular/stellate neurons: Found in layers II and IV, remain within the cortex, they are the main interneurons.
Molecular layer
Layer 1 of the cortex, contains mostly neuronal processes
Multiform layer
Layer VI, contains output neurons of varying shapes & sizes
The 6 Layers
- Molecular layer (I)
- External granular layer (II)
- External pyramidal layer (III)
- Internal granular layer (IV)
- Internal pyramidal layer (V)
- Multiform layer (VI)
Different cortical areas have different distributions of cells in all layers
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.
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.
Microtubule
Run along the length of the axon and provide the main cytoskeletal
tracks for transportation
Kinesin and dynein
Motor proteins that move cargo in the anterograde (from soma to axon tip) and
retrograde (backwards to the soma) directions, respectively
Association fibers
Fibers that interconnect cortical areas within 1 cerebral hemisphere
Commissural 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
Ascending & descending 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
2
- Short assocation fibers: Connect areas in adjacent gyri, facilitating activity along a gyrus or sulcus.
- Long association fibers: Connect more distant areas
Types of Long association fibers
2
- Superior longitudinal fasciculus (includes arcuate fasciculus)
- Inferior occipitofrontal fasciculus (includes uncinate fasciculus)
- Superior occipitofrontal fasciculus
- Cingulum
Superior longitudinal fasciculus
- Provides important sensory communication between the parietal, occipital and temporal lobes and the frontal cortex so that appropriate action can be performed.
- Includes arcuate fasciculus which connects the 2 language areas with each other in the language-dominant hemisphere
Inferior occipitofrontal fasciculus
- Below the insula, connects frontal, temporal, and occipital cortices.
- Fibers that hook around the margin of the lateral fissure and connect the frontal and temporal lobes are called the uncinate fasciculus
Superior occipitofrontal fasciculus
Runs adjacent to the corpus callosum and connects the frontal, parietal and occipital lobes.
Cingulum
Located deep within the cingulate & parahippocampal gyri (a.k.a. limbic lobe of the limbic system), connects limbic cortex areas (a.k.a. areas overlying the limbic system structures) with each other
Types of commissural fibers
3
- Corpus callosum
- Anterior commisure
- Posterior commisure
Subsections of corpus callosum
2
- Splenum: The posterior pole
- Genu: The anterior pole
Corpus callosum
The largest commissural bundle, which lies deep in the interhemispheric fissure, connecting the 2 parietal lobes, and the 2 posterior frontal lobes with each other
Anterior commissure
A small bundle of fibers that connects the anterior temporal lobes & the olfactory bulbs with each other
Posterior commissure
Located in the midbrain, connecting the 2 pretectal nuclei.
Projection fibers
Projection fibers come from all parts of the cortex in the corona radiata and converge
into a compact bundle called the internal capsule
Internal capsule
A V-shaped (in horizontal section) bundle, which can be divided into several parts:
-
Anterior limb: Between the caudate and the lenticular nucleus (putamen + globus
pallidus). - Posterior limb: Between the thalamus and the lenticular nucleus.
- Genu: Where the 2 limbs meet.
Default-mode network
- Network of brain regions that are active when an individual is at rest and not focused on the outside or engaged in tasks. It’s often referred to as the brain’s “resting state” network because it becomes more active when the mind is wandering or engaging in internally focused tasks like self-reflection etc.
- Key brain regions involved in the default mode network are:
The medial prefrontal cortex (mPFC), posterior cingulate cortex (PCC), precuneus, inferior parietal lobule (IPL), and medial temporal lobe (MTL)
Salience network
- Important for monitoring the saliency of external inputs and internal brain events.
- Anchored in the frontoinsular (FI) cortex (anterior insula) and dorsal anterior cingulate cortex (dACC) and is extensively connected with subcortical and limbic structures involved in reward and motivation
Central executive network
- The central executive network is engaged during tasks that require focused attention, working memory, decision-making, problem-solving, and cognitive control
- Key brain regions associated with the central executive network include the dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), and parts of the parietal cortex
