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Structure of Brain & The Networked Brain: What Are Brain '…
Structure of Brain & The Networked Brain: What Are Brain 'Systems'
Cortical Networks
Location\n- Cerebral cortex contains many 'networked' areas\n- Some networks organised according to common heirarchal plan\n- Sensory input & motor output represented @ diff levels abstractions @ diff levels of networks
Cortex\n- Thalamus\n - Subcortical structure composed of collection nuclei\n- Cortex reciprocally connected to thalamus\n- Diff areas send & receive projections to it\n- Sensory info arrives there before entering cortex\n- Thalamus --> Functional types cortex
Functional Types of Cortex\n- Primary\n- Unimodal\n- Supramodal
Primary Cortex\n- Initial level cortical processing\n- Low level info\n - Least abstract\n- Activity specific to one modality\n- Topographic maps\n - Arrangement reflects physical parameters
Primary Visual Cortex/V1/Area 17\n- Retinal project to lateral geniculate nucleus of thalamus\n- LGN relay info to V1\n- V1 is first area to process visual info
Retinotopic Organisation\n- Diff areas of visual field represented in discrete areas of cortex
Primary Cortices\n- Orientation selectivity\n - Neurones fire in relation to orientation of visual stimuli\n - Organised into orientation-specific 'columns'
Primary Auditory Cortex\n- Info relayed to medial geniculate nucleus of thalamus\n- MGN project to primary auditory cortex in superior temporal gyrus of temporal lobe\n- Cells fire in relation to auditory frequencies
Cochleotopic Organisation\n- Diff areas of auditory field represented as neurones in three zones\n - RI, R & AI\n - Relate to high/low frequency
Primary Motor Cortex\n- Sends info to spinal cord\n - Still primary cortical area as lowest point in motor heirarchy\n- When neurones stimulated diff muscle groups on cotralateral side activated\n- Neuronal recordings during movement\n - Population activity related to direction of movement
Topographic Organisation\n- Diff areas of motor neurones represented in relation to brain
Brain-Machine Interfaces\n-
Neural Prosthetics
Unimodal Cortex\n- Intermediate level cortical processing\n- Intermediate level info\n- Activity specific to one modality\n- Neural organisation in topographic maps\n - Reflect physical parameters less obviously
Unimodal Visual Cortex\n- Plethora visual areas outside V1\n- Areas seem to be selectively responsive to specific visual properties\n- Visual perception appears to use 'divide & conquer' strategy\n - Processing distributed & specialised
Area MT\n- Neurones selective for visual motion\n - Direction & location specific
Visual Areas\n- Distributed in occipital, temporal & parietal lobe\n- Networked into dorsal & ventral stream\n- Info @ each level of stream becomes more abstract
Dorsal Stream\n- Where pathway\n- Extends into parietal lobe\n- Processes location-related info
Ventral Stream\n- What pathway\n- Extends into temporal lobe\n- Processes object-related info
Unimodal Auditory Cortex\n- Areas in temporal lobe
Auditory Areas\n- Core cortex\n- Belt cortex\n- Parabelt cortex
Belt Cortex\n- Surrounds core cortex\n- Receive projections from core cortex\n- Composed seven fields on superior temporal gyrus
Parabelt Cortex\n- Surround belt cortex\n- Receive input from belt cortex
Unimodal Motor Cortex\n- Send outputs to primary motor cortex & spinal cord\n- All areas called premotor areas
Premotor Areas\n- In frontal lobe\n- Several subdivisions\n- Function for preparatory activity in specific areas (Crammons & Kalaska, 2000)
Subregions\n- Dorsal\n- Ventral\n- Medial
Dorsal\n- Upper part on lateral convexity
Ventral\n- Lower part of lateral convexity
Medial\n- On medial wall
Further Subdivision\n- Anterior\n- Posterior
Areas\n- 6ab (F7) = Anterior PMd\n- 6aa (F2) = Posterior PMd\n- BA44/45 (F5) = Anterior PMv\n- Inferior BA 6 (F4) = Posterior PMv
Supramodal Cortex\n- High level cortical processing\n- High level info\n - Very abstract\n- Activity specific to type info processing not single modality\n- Neural organisation reflect physical parameters less obviously
Association/Heteromodal cortex\n- Neurones have very complex response properties\n- Sensory/motor-related neural activity often dependent on context\n- Where cortical hierarchies terminate
Areas\n- Prefrontal cortex\n- Parietal cortex\n- Some temporal lobe areas
Function\n- Process & exchange info\n- Large parts modality-specific\n - Process info related to only one type of input/output
Importance\n- Understanding architecture gives clues about architecture of function
Behavioural Neurophysiology
Definition\n- Recording from single neurons in monkey/premotor cortex\n - Clicking sound amplified activity of single neurone
What Premotor Areas Do\n- Observation of 3rd person's actions activate ventral premotor mirror neurones in non-human primates\n- Suggests may be basis for communication
Hierarchies & Sensory/Motor Neurones\n- Visual\n- Auditory\n- Motor
Visual\n- Sensory/motor neurones in retina & V2\n- Thalamic area of LGN\n- Primary cortex V1\n- Unimodal cortext V3 or MT/V5 --> V4 --> Infero-temprial cortex or or PO --> Parietal cortex,\n- Supramodal cortex ventral prefrontal cortex & hippocampal system
Auditory\n- Sensory/motor neurones in cochlea\n- Thalamic area of MGN\n- Primary cortex Core\n- Unimodal cortext Belt --> Parabelt\n- Supramodal cortex of superior temporal sulcus --> superior temporal gyrus
Motor\n- Supramodal cortex dorsal prefrontal cortex\n- Unimodal cortext PMd, PMv, SMA & CMAd/v/r\n- Primary cortex of primary motor cortex\n- Thalamic area of Motor thalamus\n- Sensory/motor neurones in spinal cord