Functional Networks
Cortical Networks
organised according to hierarchical plan
modality specific - process info related to one type of input/output eg auditory, visual
thalamus - gateway to cortex - collection of nuclei - sensory info arrives here before entering cortex
Cortex
Primary cortex
Unimodal Cortex
Supramodal cortex
high level cortical processing
high level v. abstract info
activity not specific to single modality but type of info processing
neural organisation reflects physical parameters less obviously
initial level of cortical processing
low level info
activity specific to 1 modality
topographic arrangement reflects physical parameters
intermediate level cortical processing
intermediate level info
activity specific to 1 modality
neural organisation less topographic
Primary Cortexes
Primary Visual Cortex
retina projects to LGN of thalamus #
LGN relays info to PVC
PVC is 1st cortical area to process visual info (V1) #
Primary Auditory Cortex ("core")
Primary Motor Cortex
Retinotopic organisation - diff areas of the visual field are represented in discrete areas of the cortex
Primary cortices
orientation selectivity - neurons fire in relation to the orientation of a visual stimulus
organised into orientation-specific 'columns'
info relayed to medial geniculate nucleus of thalamus #
MGN projects to PAC in superior temporal gyrus of temporal lobe #
cells fire in relation to diff auditory frequencies and are mapped cochleotopically #
cochleotopic neurons arranged into 3 zones
Unlike the sensory system, the primary motor cortex sends information out to the spinal cord
It is still a primary cortical area because it is at the lowest point of the motor hierarchy.
When neurons are stimulated, different muscles groups on the ‘contralateral’ side are muscles groups on the ‘contralateral’ side are activated.
The neurons are arranged topographically
Neuronal recordings during movement: ‘population’ activity is related to the direction of the movement
Brain machine interfaces
Neural Prosthetics: Understanding information processing in the primary motor cortex allows scientists to develop methods that translate directly into benefits for clinical populations
This technology allows the brain to interface directly with control technology and bypass damaged circuitry
Hochberg et al 2006 - MN (tetraplegic)
Technique based on intracortical neuronal ensemble spiking activity could provide a valuable new neurotechnology to restore independence for humans with paralysis.
Decoders: A 'neural cursor' with which MN opened simulated e-mail and operated devices such as a television, open and close a prosthetic hand, rudimentary actions with a multi-jointed robotic arm.
Neuronal ensemble activity recorded through a 96- microelectrode array implanted in primary motor cortex
Intended hand motion modulates cortical spiking patterns three years after spinal cord injury.
Unimodal Cortexes
Unimodal Visual Cortex
Unimodal Auditory Cortex
Unimodal Motor Cortex
Supramodal Cortex
V2, V3, V4, V5 - selectively responsive to specific visual properties
divide and conquer strategy
occipital, temporal and parietal lobes
networked into dorsal and ventral streams
dorsal "where" pathway
extends into parietal lobe
processes location-related info
ventral "what" pathway
extends into temporal lobe
processes object-related info
auditory areas of temporal lobe
core cortex (primary)
belt cortex
parabelt cortex
surrounds core cortex
receives projections from core cortex
composed of 7 fields on the superior temporal gyrus
surrounds belt
receives input from belt cortex
Unlike sensory areas, unimodal motor areas sendtheir outputs to the primary motor cortex and spinal cord
Areas of unimodal motor cortex are called ‘premotor’ areas.
They are all in the frontal lobe
There are several subdivisions
The premotor cortex consists of distinct cortical areas that receive inputs from the prefrontal cortex and send outputs to the primary motor cortex.
3 broad subregions: dorsal, ventral, medial
What do premotor areas do?
Paper on monkies and accidental discovery of mirror neurons
Also known as ‘association cortex’ and ‘heteromodal cortex’.
Neurons in these areas have very complex response properties
Sensory- or motor-related neural activity is often dependent on context
Areas include the prefrontal cortex, the parietal cortex, and some temporal lobe areas.
The cortical hierarchies terminate in supramodal cortex
Essay questions
Reading
Textbook
Van Essen & Maunsell 1983
Egner 2009
Badre Esposito 2009
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