W2L3 cerebral cortex

name 3 specialized functions of the specific lobes in the cerebral cortex, and examples for each

–Special senses (e.g. somatic sensation or vision or hearing)

–Motor control (e.g. initiation of voluntary movements)

–Cognitive (e.g. different language or memory functions)

how are the primary areas orientated in the cerebral cortex

paired/matching areas in each lobe & hemisphere
couples are found as one in the lobe and another in the hemisphere

what is functional contra-laterality

(meaning opposite side)
involved with events occurring on the opposite side of the body or of external space

what does topography reveal

•contain MAPS of the body or of external space

function of left and right hemispheres of cerebral cortex

•Left = language functions; Right = spatial awareness/attention

what is the C19 phrenology THEORY

35 personality traits ascribed to different cortical regions- enlarged gyri (felt as ridges on overlying skull) show inc. development, while depressions mean underdevelopment

what are primary cortical areas

A small part of each lobe in each hemisphere, concerned with the most basic or lowest levels of sensory or motor function

name the 4 primary cortical area, and what lobes they are found at

•Primary Somatosensory (S1) Cortex (L & R parietal lobes)

•Primary Motor (M1) Cortex (L & R frontal lobes)

•Primary Auditory (A1) Cortex (L & R temporal lobes)

•Primary Visual (V1) Cortex (L & R occipital lobes)

what is the postcentral gyrus, what can be seen there

long continuous gyrus, starting from bottom, continuing into the medial cortex
can find the s1 cortex here

what happens if there is unilateral damage to the parietal lobe, post-central gyrus

•Unilateral damage results in hemi-anaesthesia (loss of tactile, thermal, pain & joint sensation, opposite side of body)

Topographic Representation or Map of the parietal lobe, post-central gyrus

•Sensory Homonculus

what does the sensory map of the (left) post-central gyrus look like?

why is the map of the body considered to be upside down

the lowest part of the body is displayed on the highest part of the brain
looks like body is hanging from a pole

what is the function of the frontal lobe, pre-central gyrus

•Micro-stimulation (Wilder Penfield) results in movements of opposite body parts

what does unilateral damage to the frontal lobe, pre-central gyrus cause

•Unilateral damage causes hemi-plegia (paralysis, opposite side of body)

Topographic Representation or Map of the frontal lobe, pre-central gyrus

Motor Homonculus

How do different Primary Areas acquire their different functions?

via long-range axon pathways that relay in the THALAMUS

Why do Primary Areas deal with only the opposite side of the body/space?

because axons cross the midline (a.k.a. ‘decussate’) once, somewhere along their pathway in the CNS

Are there anatomical differences between different Primary Areas that relate to their Functional Specialization?

subtle differences in their cellular structure (‘cyto-architecture’/ micro anatomy)

what are the 2 things that pathways inside CNS consist of

separate nuclei in the grey matter
long range axon pathways in the white matter

what do the separate nuclei in the grey matter do

•Operate as ‘relay’ stations, which process information before passing it on via the white matter axons

what do the long range axon pathways in the white matter do

•Transfer this information to neurons at the next relay

where is the thalamus found, how is it paired and what is it made up of

•Central brain location

•Paired: left & right sides separated by narrow 3rd Ventricle

•Comprises many nuclei

what does the thalamus do (2 points)

•Receive input from specific sensory or motor pathways

•‘Relay’ to specific Areas of Cerebral Cortex, via axons in the Internal Capsule (which is a large white matter pathway)

what are the 4 ‘primary’ relay nuclei, what does each do

VL- ventral lateral, relays motor signals to primary motor cortex
VP- ventral posterior nucleus, relays somatosensory info to lateral cortex
MG- medial genicular, relays auditory info to auditory primary cortex
LG- lateral genicular, eye up to primary visual cortex

what are internal capsules

Thalamic axons ‘radiating’ towards the Cortical Grey Matter

what is corona radiate

radiating crown of axons travelling from internal capsule to different areas of the cerebral cortex (seen with yellow arrows here)

what is the cortical cytoarchitecture made up of, what can be found in it

6 Layers of the Grey Matter: neuron  cell bodies, different sizes & densities

why is layer 4 darker, and what is it made up of

darker as it has loads of neuron cell bodies (stellate neurons, which are only found in layer 4)
layer 4 is mainly stellate/granule cells, receive thalamic input

what does layer 4 do

acts as local circuit neurons, excite the cells above and below

what is found in the other layers

mainly pyramidal cells, long-range projections

what are the blue cells here

all the blue dots are cell bodies of corticol neurons
note the darker 4th layer, and layer 1 containing almost no neurons at all, as it only has synaptic connections

what are the 4 types of cortical connections, name the layers they are found in

•Thalamic Input (layer 4)

•Inter-Cortical ‘Association’ projections (layers 2 & 3)

•Inter-hemispheric projections via corpus callosum (layers 2 & 3)

•Subcortical descending projections (layers 5 & 6)

what does brodmann’s area describe

Korbinian Brodmann (~1900), identified 52 discrete areas of human cerebral cortex, based on differences in layer thickness, cell size & distribution (i.e., cytoarchitecture) 

what is expressive aphasia, what causes it

inability to express language, can be caused by focal lesion in the inferior frontal lobe

what is receptive aphasia, what causes it

inability to understand spoken language, caused by focal lesion in left superior temporal lobe

2 type of memory

Procedural: Motor Skill Acquisition
Declarative: Facts & Episodes

3 points about procedural memory

•No conscious access

•Acquisition difficult (practice), long-term retention

•Cerebellum & Premotor Cortex (e.g., Broca’s Area)

4 points about declarative memory

•Conscious recollection

•Acquisition easy (single events), retention variable

•Short-term, ‘Working’: Pre-Frontal Cortex

•Long-term ‘Autobiographical’: Limbic System

what are 5 things (3 with working memory, 2 with personality) changes that damage to the pre-frontal cortex can do

Working Memory Loss

Difficulty organizing moment-by-moment behaviour

Numerous plans, instantly abandoned

Distractible

+ Personality changes

Impatient of restraint

Licentious & Profane

what can bilateral hippocampus removal cause

Anterograde Amnesia

•unable to form new long-term personal memory of any autobiographical life events

which MAPs is inverted

the somatosensory map in the post-central gyrus is inverted

what does it mean when we say inverted MAPs

sensory info coming from the top part of the body (eg, fac) is processed by neurons in the lower part of the gyrus, with sensory info coming from lowest part of body processed by neurons at upper part of gyrus

what does the visual hemifield MAPs in the banks of the calcarine sulcus look like

is distorted, many neurons in the posterior half of the cortex process sensory info coming from a small part of the central retina (fovea, macula), with relatively few neuros at the anterior end of the cortex, devoted to processing info coming from a bigger region of the peripheral retina

name 3 white matter pathways

optic nerve, internal capsule, corpus callosum

name the functions of areas 4, 17 and 44/45

Four main lobes of the cerebral cortex and their primary functions

Frontal lobe: Motor control and voluntary movements
Parietal lobe: Somatic sensation
Temporal lobe: Hearing and auditory functions
Occipital lobe: Visual functions

What is meant by "functional contralaterality" in brain function?

Functional contra laterality is the phenomenon where each hemisphere of the brain controls and processes sensory input from the opposite side of the body

What is the primary somatosensory cortex (S1) responsible for?

The primary somatosensory cortex (S1) processes sensory input from the body, such as touch, pain, and temperature, and contains a map of the opposite body parts known as the sensory homunculus

What is the role of the primary motor cortex (M1)?

The primary motor cortex (M1) controls voluntary movements of muscles, and like the somatosensory cortex, it has a distorted map of opposite body muscles called the motor homunculus

What is the motor homunculus, and where is it found?

The motor homunculus is a topographic map of muscles in the primary motor cortex (M1), showing areas responsible for different muscle movements

What is Broca's area and its associated function?

Broca's area, located in the left inferior frontal gyrus, is involved in speech production. Damage to this area leads to expressive aphasia, where patients have difficulty speaking but can understand language

What is Wernicke's area responsible for?

Wernicke's area, located in the superior temporal gyrus of the left hemisphere, is essential for understanding spoken language. Damage here results in receptive aphasia, impairing comprehension but leaving speech production intact

What role does the corpus callosum play in the brain?

The corpus callosum connects the left and right cerebral hemispheres, allowing information to be shared between them

How is the visual map in the primary visual cortex (V1) organized?

The visual map in V1 is inverted and distorted, with large areas devoted to central vision and smaller areas for peripheral vision

What is the function of pyramidal cells in the cerebral cortex

Pyramidal cells are long-range projection neurons that transmit signals from one region of the brain to another, primarily found in layers 2-3 and 5-6 of the cortex