Association Cortices Flashcards
How does the cortex develop?
Inside-out cortical development
neurons migrate towards the cortical plate with the help of radial glial cells = radial glial migration
migration is achieved through the action of cytoskeletal microtubules resulting in the formation of 6 cortical layers of the cerebellum
Brain Tissue Histology:
How many layers in the following:
- allocortex
- mesocortex
- neocortex
- 3/4 layers (olfactory system and
hippocampus) - 3 layers (paralimbic region connecting
the limbic system to higher neocortical
areas) - 6 layers (90% of the brain)
***histology
Brain Tissue Connections:
Role of the following layers:
- Layer IV
- Layers III & V
- Layer IV = input
- Layers III & V = output
(generally)
areas of the brain collecting sensory information would have a thicker layer IV as there would be more inputs
motor cortex would have thicker output layers
Brodmann identified 52 separate areas of the brain based on
the histology and architecture of the brain in these different areas
Nervous System Circuitry:
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Anatomy of the Brain:
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What is the function of the primary cortex?
Deals with unprocessed information from the body/retina
What is the function of the secondary association cortex?
integration of information of other parts of the brain
Association Cortex Areas:
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Parallel Processing in the Brain: Sensorimotor Integration:
- perceptual mechanisms generate a
sensory representation of the external
world and individual in it - cognitive processes decide on course
of action - motor plan relayed to action systems
to implement
What is the dorsal stream in the cortex?
the dorsal stream from occipital to parietal cortex is concerned with:
- location
- motion
- action
(Where/How)
What is the ventral stream in the cortex?
The ventral stream from occipital to temporal cortex is concerned with:
- object identity
- conscious perception
(What)
Dorsal and Ventral Streams in the Cortex:
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Which Brodmann Area is assigned to the primary motor cortex?
Area 4
Which Brodmann Area is assigned to the premotor/supplementary motor area?
Area 6
Which Brodmann Area is assigned to the posterior parietal cortex?
Areas 5 & 7
Temporo-parieto-occipital region:
integration of information where temporal, parietal and occipital lobes meet
higher cognitive areas in this area, where all information comes together
shorter connections, faster, less likely to have damage to information
The Binding Problem:
- Lashley’s epipotential theory: every
neuron in the CNS has the potential to
perform every function -> not true
because loss of some parts of brain
function can not be recovered - Grandmother cell hypothesis = only
one cell in CNS for a function,
grandmother cell will know everything
to do with your grandmother, if it is
damaged, you will lose the knowledge
of your grandmother
Cortical Plasticity:
- adult brain has a low incidence of
regeneration - some degree of plasticity in the
somatosensory cortex located in the
postcentral gyrus - when fingers are amputated there are
changes in that cortical area to reflect
the missing digits now responding to
stimulations from adjacent skin areas - cortical plasticity diminishes with age
How does fMRI work?
- brain has no energy stores and
requires glucose - glucose needs to be transported to the
brain and causes arterioles to dilate - signal characteristics of oxy and deoxy
haemoglobin indirectly measures local
neuronal activity based on this
vascular response - poor spatial and temporal resolution
What is conduction aphasia?
lesion of the arcuate fasciculus
inability to repair but preserved comprehension and fluency
Broca’s Area:
- frontal lobe
- posterior inferior frontal gyrus
- superior branch of left middle cerebral
artery - non-fluent (makes sense but cant find
words) dysphasia (expressive
dysphasia)
Wernicke’s Area:
- temporal lobe
- posterior third of superior temporal
gyrus - inferior branch of left middle cerebral
artery - fluent (but nonsensical)
dysphasia (receptive dysphasia)
Which white matter tract links brocas and wernickes area?
Arcuate Fasciculus
important for repetition
Language Areas:
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Alexia without agraphia:
- pure word blindness
- lesion of splenium (posterior corpus
callosum) - dominant occipital lobe lesion
- disconnection of visual cortex from
Wernicke’s area - inability to read = alexia
- name colours = colour anomia
- cant read, but can identify colours,
objects etc
What is the Wada test?
- establishes language and memory
lateralisation in each hemisphere - injection of barbiturate into one
carotid artery, monitored with EEG - if you infuse the dominant
hemisphere, language ability is
significantly impaired
Gerstmanns Syndrome:
- dominant lobe parietal lobe damage
- supplied by middle cerebral artery
- finger agnosia
- left-right confusion
- dysgraphia
- dyscalculia
Visual Neglect:
- non-dominant hemisphere
- failure to acknowledge or be aware of
items on the contralesional side
Aprosody:
- non-dominant hemisphere damage
- intonation of speech is altered
Prosopagnosia:
- non dominant hemisphere (fusiform
gyrus) damage - facial blindness
Gnosis
knowledge
Anosognosia
lack of insight (unaware of deficit, not denial )
Agnosia:
- unable to recognise and idenitfy
objects, people or sounds using one or
more of their senses despite othewise
normally functioning senses - apperceptive - failure in recognition
due to perception deficits - associative - failure in recognition
despite no deficit in perception eg
math colours but can not name or
identify objects
