Task 4 - Organization of the Cerebral Cortex Flashcards
(20 cards)
The neocortex consists of 6 layers. Name these and explain what they are formed by
Layer 1 - molecular layer, contains neural processes
Layers 3 and 5 - pyramidal neurons of which their axons project to other regions and spinal cord (they’re the main output cells)
Layer 2 and 4 - granullar/stellate neurons which remain within the cortex
Layer 6 - multiform layer; it is the output for varying shapes and sizes
Not all parts of the cortex have the same distribution of cells.
Give two examples.
M1 -agranullar cortex; many pyramidal neurons
Primary sensory cortex - few pyramidal cells, large number of granular neurons
What does Cytoarchiterture mean?
It is the study of the cellular composition of the CNS’ tissues under the microscope, by Broadmann –> Cortex has functional columns that process specific inputs or outputs
Brodmann’s map when used as a pure localization tool of signposts, can generate misleading architectonic localizations of functional imaging data. Why is this?
Because the map does not reflect the intersubject variability of cortical areas (brain changes a lot between people). Therefore, probability maps are being used.
Red indicates regions of high overlap (low intersubject variability)
Blue and green indicates regions of low overlap (high variability)
What is the myeloarchitectonic map?
It is Vogts (name) map to study the brain architecture using myelin-stained histogical sections. It had many more areas that Broadmann’s map
What are the subcortical fibre bundles? Name them.
- Association fibres
- Commisural fibres
- Ascending/descending projection fibers
Explain what the Association fibers do and what they consist of.
Short association fibres interconnect areas within one hemisphere
Long ones connect areas more distant from each other
Consist of:
- Superior longitudinal fasciculus (+arcuate fasciculus)
- Inferior occipitofrontal fasciculus (+ uncinate fasciculus)
- Superior occipitofrontal fasciculus
- Cingulum
Explain what the commissural fibres do and what they consist of.
Connect areas of cortex in one hemisphere with same areas in opposite hemisphere.
Consist of:
- Corpus collasum (+ splenium + genu)
- Anterior and posterior commissures
Explain projection fibers
Fibers to or from cortex via thalamus or basal ganglia, brainstem and/or spinal cord
What is corona radiata?
Process in which projection fibres from all parts of cortex merge and form internal capsule
Explain the anatomy of the internal capsule
V shaped, divided into anterior limb (between caudate putamen and Globus pallidus) and posterior limb (between thalamus and putamen and Globus pallidus)
What are the Tracing techinques?
Used to map connectivity between brain areas
Procedure: delineate location of injection site and on other hand slice up the brain → create microscopic preparations to visualize amount of substances that has arrived in each slice
Most cognitive processes involve multiple brain regions working together; thus brain mapping is now a systematic understanding of large-scale functional organization.
What are the 6 principles for such organization?
- Global brain architecture
- Graded inter-intrahemispheric connectivities
- Coherent functional networks
- Activated and deactivated brain systems
- Default mode network: system involved in self-referential mental processes
- Dissociable fronto-opercular-parietal control systems
Explain the 1st principle
Small world networks: made of contributing nodes that show dense local clustering and short distances between two nodes → balance between local processing and integration of information; Large degree of clustering allows then to work economically
Hubs: brain areas (nodes) that communicate information across different brain systems within small world architecture
—> example: tutorials
What do “small world structures” mean?
The lambic system, basal ganglia, etc are different dense structures that have different functions but communicate, not only within themselves but with other structures as well.
Explain 2nd principle
Highest correlations among homotopic (same regions in different hemispheres) regions occur across primary sensory-motor cortices and significantly lower in unimodal association areas (i.e. areas that deal with one sense)
➔ Left hemisphere shows stronger intrahemishperic connectivity in language and motor areas
➔ Right hemisphere shows stronger intrahemispheric connectivity in attention and visuospatial processing areas
Explain 3rd principle
Brain areas that are active during different cognitive tasks also form large-scale brain networks.
Also reflect fluctuations: pattern of activity remains stable and similar on different tasks
Explain 4th principle
Although brain activity varies with task context, neural activity in some brain systems is supressed while other systems are preferentially actively engaged in task-relevant information processing (bottle neck effect)
—> brain responses within target regions increase/decrease proportionally in relation to cognitive demands and task difficulty
Explain 5th principle
Collectively, default network helps in construction of mental models of personally significant events;
They found this because the forgot a participant in a fMRI and this person started daydreaming. When the came back they saw a lot of activation in the brain (no actual physical activity needed)
Explain 6th rpinciple
→ Salience network: Involved in conflict monitoring, interoceptive-autonomic (feelings of body sensations) and reward processing areas
→ Centra Executive Network: Involved in detecting, integrating and filtering relevant interoceptive, autonomic and emotional information, i.e. identify most relevant information among several internal and external stimuli to guide behaviour - if you’re day dreaming and the fire alarm goes off your attention shifts to the most relevant/important stimuli (alarm)
Dynamic interactions between SN and CEN regulate shifts in attention and access to goal-relevant cognitive resources
