Functional organisation of the brain and brain plasticity Flashcards
What is a neuron?
The elementary unit of the nervous system. Basic signalling units. They receive, integrate and transmit signals
What is the soma?
Cell body. Contains the cell’s nucleus and DNA
What are dendrites?
They receive input. They are the branches of the neuron that pick up signals carried adjacent neurons
What are axons? (& myelin)
(Output). The fatty sheath that covers an axon is made up of myelin which speeds up conduction of nerve impulses
What are glial cells?
- They provide supportive functions - housekeepers of CNS
- They do not generate signals themselves
- ~10x more glial cells in the brain than neurons
- Without them neurons would not function properly and may die (e.g. multiple sclerosis
What are the 2 main types/locations of neural signalling?
Within the neuron and between neurons
What is a synapse?
The space between neurons where communication happens.
Presynaptic neuron –> synapse –> post synaptic neuron
What does chemical transmission happen between?
Cell-to-cell
What is the brain and what does it do (in broad, non-specific terms)?
- Provide knowledge about how the brain works and understanding the consequences of brain damage
- Helps understand how cognition is created/implemented
- Knowledge about brain structure and function can inform and constrain psychological theories (integration)
- There is a strong association between the brain, the mind and behaviour
- We are reverse engineering something already ‘designed by nature’ to understand these relationships
What does medial versus lateral mean?
Middle versus to the side
What does superior versus inferior mean?
Superior versus below
What does anterior versus posterior mean?
Front versus back
What does dorsal versus ventral mean?
Back versus abdomen
What does ventromedial prefrontal cortex versus dorsolateral prefrontal cortex mean?
vmPFC (just above your eyes) means low and in the middle whereas dlPFC means higher up and on the side
What is grey matter?
On the outside of the brain. Contains the cell bodies of neurons
What does cortex mean?
Bark. Large thin layer of neurons covering the brain. Roughly 3mm thick
What significance does the folding of the cortex have?
It is many bumps and grooves, meaning it is highly folded. It is folded to maintain a high SA to volume ratio (save space), to bring the neurons closer together (improves communication) and the regions closer together (improve efficiency of communication)
How does cortical folding develop?
- Cortical folding also changes dramatically across development
- Folding peaks in around the 66th-80th week of life (birth = 40 weeks), remaining high in adults
What does GI stand for?
Gyrification index, a way of measuring extent of folding
What is white matter?
- Like the motorways or roads between the cities (grey matter)
- Make up connections between regions
- Appears while because of fatty myelin covering axons
What are tracts?
- Bundles of neuronal fibres connecting brain regions (motorway analogy)
- Studied using DTI methods
What are DTI methods?
Diffusion tensor imaging, an imaging method based on measuring the movement of water molecules in the brain
What are the 3 types of white matter pathways?
- Projection tracts: Connect ‘higher’ and ‘lower’ brain regions, and brain to spinal cord (e.g., corticospinal)
- Association tracts: Connect regions within same hemisphere (IFOF)
Commissural tracts: Links L and R hemispheres (e.g., corpus callosum)
What are gyri (si: gyrus)?
A ridge or protruding surface of the brain (pink bit)
What are sulci (si: sulcus)?
A depression, groove, crevice in brain surface (black bits)
What are the 4 lobes?
Temporal, parietal, Frontal, Occipital
What is the temporal lobe responsible for?
Hearing, language and memory
What is the parietal lobe responsible for?
Movement, spatial processing, somatosensory processing
What is the cerebellum responsible for?
Balance, fine motor movements, timing
What is the dorsal portion frontal lobe?
Primary motor cortex
What is the motor cortex?
Area at the back of the frontal lobes that controls voluntary movements
What does stimulation to specific parts of the motor cortex in left or right hemisphere do?
makes specific body parts move on the opposite (contralateral) side of the body
What is the homunculus?
(little man) Body regions represented in the ‘homunculus’, with ordered point-to-point relationship (e.g., toes next to ankle representation)
- Size of each body part relates roughly to size of cortical region that controls muscles in that body part - except face & hands (much larger cortical representation because they are extremely important to functioning, more nerve fibres than in other parts of the body)
- So, face & hands are over-represented as they have more fine muscles & therefore muscle control – more receptors
What is located in the parietal lobe?
Primary somatosensory cortex
What is the primary sensory cortex?
o an area at the front of the parietal lobes
- It registers and processes body sensations
- Stimulate this area and the person reports being touched
- The more sensitive a body region, the greater area of sensory cortex devoted to it
- Contralateral organisation
What is the occipital lobe?
Also known as the ‘visual cortex’
- A blow to back of the head might cause you to go blind
- If stimulated there, you may see flashes of colour/light
What is the temporal lobe?
Contains the auditory cortex
- If stimulated there, you might hear something that isn’t real
- fMRI data from people with schizophrenia reveal that auditory areas are active during hallucinations
What is the association area?
- Makes humans different
- Most of the rest of cortex made up of brain areas not involved in primary motor or sensory functions (e.g. vision, audition etc.)
What is cortical cytoarchitecture?
- Cell structure and organisation
- Brodmann (1909)
- Original drawings of ~52 different brain areas
- He categorised these neural regions according to their distinctive:
- Cell morphology
- Cell organisation (e.g. layers)
(not overly modern but must be showing something so it’s still in use today) - System still in common use today (e.g., fMRI findings)
- Numbering often done rather randomly
What are subcortical structures?
- Below the cortex are older, more primitive areas of the brain – with more basic functions (breathing, temperature, hormones, sleep, fight/flight, etc…)
- E.g. Amygdala, hippocampus, hypothalamus
What is plasticity?
The brain’s capacity for modification
- Evident in brain reorganisation following damage
- Especially in children (younger = more plastic)
What have experiments on the effects of experience on brain development revealed?
- Most severed neurons will not regenerate
- However, neurons can reorganise in response to damage
- And new neurons are growing all the time
What is phantom limb?
Sensations of an arm or leg that has been lost or removed. The limb still lingers in their minds and is painful
What is the main theoretical reasoning behind phantom limb?
It emerged from sensitive nerve endings
What sis Ramachandran find while studying phantom limbs?
- Hypothesised that the missing lower arm area of the sensory cortex might have reorganised due to missing the normal sensory input
- The face and upper arm areas are on either side of arm area, they would be most likely to take over the cortex that is lacking normal innervation by arm
- Found that stimulating the patient’s face led to ‘sensations’ in their phantom limb and so face-area did innervate the arm area!
- Same finding with the upper arm area
- 2 representations for missing arm: one on the face & one on upper limb
- The ‘hand area’ in brain no longer being stimulated (no hand!), so the neighbouring face and arm areas ‘took over’ this region
What was found by Maguire (2000) studying taxi drivers with MRIs?
- The hippocampus is a brain area involved in spatial navigation/maps
- Study with London taxi drivers showed they had a larger hippocampus than controls
- Shows more experience in spatial navigation is associated with a larger hippocampus
- Furthermore, the amount of time learning to be and working as a taxi driver was correlated with size of hippocampus
How can brain organisation change with experience?
The brain is not as ‘hard-wired’ as once thought
- This can happen due to experience or damage, such that brain areas may reorganize themselves over time
- This means that everyone’s brain is unique and is constantly being sculpted by experience
