Intro to Brain Anatomy - Cortical Cytoarchitecture Flashcards
Cytoarchitecture
- Cyto = cell
- Architecture = structure
- Study of how the layers change in thickness and density provides us insight into function
Early Studies
- End 19th century
- Alcohol harden the brain
- Could inspect thin sections of tissue and stain
- Many pertinent studies in early 20th century
Staining Techniques
- Golgi stain
- Nissl stain
- Weigert stain
Golgi Stain
- Stains about 10% of neurons
- Can see the morphology of the neuron
Nissl Stain
- Stains the cell bodies of all neurons
- Great for cytoarchitecture since determines the cell densities
Weigert Stain
- Stains the axons
Cortical Cytoarchitecture
- Two main types of neurons in the cortex:
- Pyramidal neurons
- Granule/stellate neurons
Pyramidal Neurons
- Soma shaped like a pyramid
- Basal dendrites
- Apical dendrite
- long axon that exits the cortex
- The typical cortical neuron
Granulate (stellate) neurons
- Smaller and rounder
- Axons usually do not leave the cortex
- Mainly distribute information to neighbouring layers
- Does not always appear in old cortex
Cortical Layers
- Layer I:
Few cells
Info from apical dendrites of neurons in lower levels - Layer II:
External granular layer although now understood to consists of mainly pyramidal layers. -
Layer III:
External pyramidal layer
Pyramidal cells increase in size from outer to inner boundary
Project axons to cortical areas
cortico-cortical connections -
Layer IV:
Internal Granular layer
Granular neurons
Receive input from cortical and subcortical areas -
Layer V:
Internal Pyramidal layer
Pyramidal neurons
Axons extend to subcortical structures
cortical-subcortical connections - Layer VI:
Spindle-shaped neurons (modified pyramidal form neuron)
Axons mainly project to subcortical structures
Function Example 1 :
Primary Motor Cortex is _______
- Agranular
- Large pyramidal neurons occupy layer V and project to the spinal cord to control movement
Motor cortex cares more about sendin**g information than receiving.
Function Example 2:
Primary sensory areas are ________
- Hypergranular
- referred as korniocortex (dust cortex)
- Receive a lot of input from the thalamus
Agranular
Separation between pyramidal cells of layers III and V is not clear.
Dysgranular
Separation between layers III and V is interrupted
Granular
Separation between layers III and V is very clear
Old Cortex
- Fewer than 6 layers
-
Hippocampus
- Part of it just 1 layer
Parahippocampal Gyrus
- Contains (From up to down):
- Thalamus
- Hippocampal Sulcus
- Pyriform Cortex
- Entorhinal Cortex
- Parahippocampal Cortex
- Rhinal Sulcus
- Collateral Sulcus
- Fusiform Gyrus
- Occipito-Temporal Sulcus
- Inferior Temporal Gyrus (ITG)
- L4 p.22:
- Used to be referred as Rhinencephalon (nose brain)
- Patient H.M.
- Important for Memory consolidation
- Pyriform cortex
- Entorhinal cortex
- Parahippocampal cortex
Pyriform cortex
- Primary olfactory cortex
- Also known as: Paleocortex (old cortex)
Entorhinal cortex
- Above amygdala and anterior hippocampus
Parahippocampal cortex
- Above the posterior hippocampus
From where did all the cortex evolved?
From the archicortex and paleocortex
Which is the most famous cytoarchitectonic map?
- Brodmann’s
- Brodmann areas
Precentral Gyrus
- At least two cytoarchitectonic areas:
-
Area 4
- Real M1
- Fast direct projections to spinal cord
- Layer V: Beltz cells
-
Area 6
- Premotor cortex
-
Area 4
- Both agranular
Beltz Cells
- Extremely large pyramidal neurons
- In layer V of Area 4
- Axons are big and very myelinated
Why are the Beltz cells the largest on the dorsal motor cortex?
- Given Penfield’s schema, the dorsal part of the motor cortex is the one in charge of controlling the legs.
- The information needs to get further down the spinal cord
- Longer axon = larger cell body
Postcentral Gyrus
- 3 cytoarchitectural areas:
-
Area 3:
- Real S1 (primary somatosensory cortex)
- posterior bank of central sulcus
- Input from thalamus
-
Area 1:
- Postcentral gyrus
-
Area 2:
- Anterior bank of postcentral sulcus
-
Area 3:
What are those!
- Green: Pars Triangularis
- Pink: Pars Opercularis
- Blue: Pars Orbitalis
Area 44
- Approximately Pars Opercularis
- Dysgranular
Area 45
- Approximately Pars Triangularis
- Granular frontal cortex
- Unusually large pyramidal neurons
Area 47/12
- Approximately Pars Orbitalis
- (Not a Brodmann Area)
- Granular frontal cortex
- lacks usually large pyramidal neurons
True or False
Brodmann’s Areas only exists in the language dominant hemisphere.
False
They exist in both hemispheres and their functionality is pretty much the same.
We say that the left hemisphere is dominant for language.
True or False
The left hemisphere is the language dominant hemisphere.
True
Traditional Broca’s Area
- Areas 44 and 45
- Some people don’t include the pars triangularis
- Some people don’t include the pars opercularis
Primary Auditory Cortex A1
- Area 41
- Occupies the transverse temporal gyrus within the Sylvian fissure
- Heschl’s gyrus
Heschl’s Gyrus
- Area 41
- A1
- Can be one or two:
- Is two the Area 41 is in the most anterior
Areas to know
- 4: M1
- 6: Premotor cortex
- 3: S1
- 1, 2: Somatosensory cortex
- 17: V1 (superior to calcarine sulcus)
- 18: “V2”
- 41: A1
- 44: pars opercularis
- 45: pars triangularis
- 47/12: pars orbitalis
- 22: STG
- 40: Supramarginal gyrus
- 39: Angular Gyrus
L5 p. 17
