Please enable JavaScript.
Coggle requires JavaScript to display documents.
PS2061: The Networked Brain: What Are Brain Systems - Coggle Diagram
PS2061: The Networked Brain: What Are Brain Systems
Cortical Networks
Cortical Networks
Cerebral cortex contains many 'networked' areas
Process & exchange info
Understanding architecture gives clues about function
How areas wired up to each other
How activity changes between network nodes
Thalamus as Gateway to Cortex
Subcortical structure composed of collection of nuclei
Reciprocally connected to cortex
Diff areas send & receive projections
Sensory info arrives there before entering cortex
Thalamus --> Functional types cortex
Functional Types of Cortex
Primary
Unimodal
Supramodal
Primary Cortex
Initial level cortical processing
Low level info
Least abstract
Activity specific to one modality
Topographic maps
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 (Chapin, 2004; Schwartz et al., 2006)
Understanding low-level coding of motor cortex
Aids practical uses
Understanding info processing in primary motor cortex
Methods that translate directly to benefits for clinical populations
Neural Prosthetics in Monkey
Allows brain to interface directly w. control technology & bypass damaged circuitry
Electrode array implanted into motor cortex
Multi electrode recordings discriminate multi-neurone signals
Decode intended movements & move robotic limb
Neural Prosthetics in Human (Hochberg et al., 2006)
Tetraplegic human (MN) three years after spinal cord injury
Neuronal ensemble activity recorded through 96-microelectrode array implanted in primary motor cortex
Intended hand motion modulates cortical spiking pattern
Neural cursor used to open and operate devices, operate prosthetic hand & conduct rudimentary actions w. multi-jointed robotic arm
Significance
Neurotechnology to restore independence for humans w. paralysis
Use techniques based on intracortical neuronal ensemble spiking activity
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
How Premotor Areas Work
Observations of 3rd person actions activates ventral premotor 'mirror neurones'
In non-human primates
Significance
May be basis for communication
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
Common Plan for Cortical Networks
Some networks organised according to common heirarchal plan
Large parts of networks modality specific
Process info related to one type input/output
Sensory input & motor output represented at diff levels abstractions at diff levels of networks
Importance\n- Understanding architecture gives clues about architecture of function
Function\n- Process & exchange info\n- Large parts modality-specific\n - Process info related to only one type of input/output
Defining the Problem
Scale
Simplification/generalisation
Scale
Primate brain composed of 10^12 neurones
Each neurone makes 10^3 connections w. other neurones
Info flows in 10^15 connections
Working out how system operates is formidable task
Simplification/Generalisation
Common ways in which problem space reduced
Look out for common principles
Common Principles
Parallel vs serial processing
Convergence vs divergence
Local vs distributed processing
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
