Task 4 - Cerebral Cortex Flashcards
Cerebral cortex lobes
Frontal Parietal Temporal Occipital Limbic
Subcortical fiber bundles
Connect cortical areas:
- Association fibers
- Commissural fibers
- Ascending/descending projection fibers
Histological Cortex Organization
Organized in layers: Neocortex: 6 layers I-VI -> enables thought Older cortical areas only 3 layers: -paleocortex -archicortex
Paleocortex
Olfactory bulb, uncus, anterior commissure
Archicortex
Hippocampus, dentate gyrus
Pyramidal Neurons
- in layers III and V
- triangular structure: 1 apical dendrite and abundant dendritic trees coming from cell body
- main output cells of cortex: project into other brain regions and spinal cord
Granular Neurons
- in layers II and IV
- stellate neurons
- shorter axons, smaller dendritic trees
- remain in cortex
- > main interneurons of cortex
Layer I
Molecular layer
contains neuronal processes
Layer VI
Multiform layer
contains output neurons
Agranular Cortex
Mainly contains pyramidal neurons projecting to lower motor neurons (e.g. primary motor cortex)
-> not many granular neurons
Granular Cortex
Mainly contains granular neurons processing sensory information (e.g. primary sensory cortex)
-> few pyramidal cells
Cytoarchitecture
Cortex is organized into functional units
- > cortical columns
- columns specizalized to process specific inputs or outputs (depends on function)
Cortical layers
I: molecular layer II: external granular layer III: external pyramidal layer IV: internal granular layer V: Internal pyramidal layer VI: Multiform layer
Subcortical fiber bundle function
Relay information to and from specific brain areas
Association fibers
Interconnect areas within one hemisphere:
- short association fibers: connect areas in adjacent gyri
- long association fibers: connect areas more distant from each other
Commissural fibers
Connect cortical areas of one hemisphere with the same ones in the opposite hemisphere
-> enables coordination of cortical activity across hemispheres
Anterior commissure
Connects anterior temporal lobes and olfactory bulbs with each other
Posterior Commissure
In midbrain, connects pretectal nuclei
Projection fibers
Travel to or from the cortex: ascending or descending
- descend to: basal ganglia, brainstem, spinal cord
- converge in internal capsule
Brodmann’s cortical organization
- divided human cortex into 43 cytoarchitectonic areas
- each area labelled by number between 1-52 (areas 12-16, 48-51 not found in human cortex)
- > cytoarchitectonic map
- > architectonic units of Brodmann later linked to functional areas of the brain with neuroimaging
Axoplasmic Transport
Movement of organelles, lipids, proteins, synaptic vesicles and other parts of cell membranes to and from the soma down the axon to synapses and back to soma
-> essential to growth and survival of neuron
Microtubules
- run along length of axon
- provide main cytoskeletal tracks for axoplasmic transport
Motor proteins
Move axoplasmic transport cargo to axon and back to soma
- kinesin & dynein
- bind and transport different cargos: mitochondria, cytoskeletal polymers, synaptic vesicles containing neurotransmitters
Anterograde axoplasmic transport
Facilitated by Kinesin
- movement of organelles outward (from soma to axon tip)
- cargo moved in transport vesicles along microtubules mediated by kinesin
Kinesin
Anterograde motor protein
Dynein
Retrograde motor protein
Retrograde axoplasmic transport
Movement of molecules/organelles inward: from axon tip to soma
- cargo moved in transport vesicles mediated by dynein
- source of recycling of many substances + informs soma of conditions at axon terminal
Tracing
Injection of substance and imaging of its metabolization
- > importatn for mapping connectivity between brain areas
- provides specific insights where input to field comes from and where it projects to
Disadvantages Tracing
- injection site never perfectly matches field of interest
- substances often spread into adjacent fields
- substances affect various neurons in injection cells -> not only targeted neurons
1st Major principle of Large-Scale functional organization
Characterized by non-random, small-world, modular global brain architecture with strategic hub regions regulating communication among different functional systems
2nd Major priniple of large-scale functional organization
Large-Scale functional organization underlies strong interhemispheric connectivity with gradient of decreasing left-right connectivity from sensory to association and hetermodal cortices
3rd Major principle of large-scale functional organization
Human brain is intrinsically organized into coherent functional networks
4th major principle of large-scale functional organization
Functional brain organization is characterized by tasks- and context-dependent activated and deactivated brain systems (-> limited parallel processing to restrict neural resources)
5th major principle of large-scale functional organization
Default-mode network:
- large scale network formed by most widely deactivated regions
- tightly functionally and structurally interconnected
- important for self-referential information processing and monitoring of internal mental landscape
6th major principle of large-scale functional organization
Core prefrontal parietal control systems can be separated into distinct brain networks with distinct roles:
- salience network
- central executive network
Small-world architecture
Network in which constituent nodes have a large degree of clustering and relatively short distances between two nodes
-> promotes high specialization and high integration within modular architecture
Cortical hubs
Brain areas communicating information across different brain systems within a small-world architecture
e.g. posterior cingulate cortex: facilitates rapid integration of information across multiple functional systems
Bias of interhemispheric connectivity
Left hemisphere: bias toward stronger intrahemispheric connectivity
Right hemisphere: bias toward stronger interhemispheric connectivity
-> consistent with laterlization for language and bilateral visuospatial attention networks
Interhemispheric connectivity gradient
Highest interhemispheric interaction strength: primary sensorimotor cortices
- lower correlations across heteromodal association areas
- lower correlations across heteromodal association areas
Default-Mode Network
Anchored in posterior cingulate cortex and medial prefrontal cortex
- set of brain regions deactivated during wide range of cognitive tasks
- linked to: episodic memory, autobiographical memory, internal speech
- > construction of mental models of personally significant events
Fronto-Opercular-Parietal Control Systems
Salience Network
Central executive network
Salience Network
Anchored in anterior insular and anterior cingulate cortex
- integrated brain signals of conflict-monitoring, interoceptive-autonomic, and reward-processing areas
- > identification of homeostatically relevant stimuli to guide behavior
Central Executive Network
Frontoparietal network anchored in dorsolateral & ventrolateral prefrontal cortices and supramarginal gyrus in lateral parietal cortex
-> critical for active maintenance and manipulation of information in working memory
(rule-based problem solving, decision-making in goal-directed behavior)
Interaction between Salience and Central Executive Networks
Regulate shifts in attentions and access to goal-relevant cognitive resources
