Lecture 11&12 - Map Plasticity and Pathologies Flashcards
1
Q
What is a bad example of plasticity?
A
- Phantom Limbs: removal of sensory surface can lead to ongoing sensations from the surface
2
Q
What is PLP?
A
- Phantom Limb Pain
- Some stereotypical experiences that a lot of PL patients feel
- Pharmaco resistant
3
Q
What did Ramachandran do?
A
- Very small N group
- Strong spatial relationship between intact body and sensation of phantom limb
- Could touch someones face to make him feel his thumb due to the human plasticity map
- Got patients into MEG and used one hemisphere to act as a baseline and found a closeness within cortex that would have responded to the missing limb
4
Q
What happens when you look at a larger population?
A
- Sensations stable?: do you still feel it when i stroke face
- Are sensations modality specific?: Is it an itch/pain?
5
Q
Is there a relationship between PLP and remapping?
A
- Sig correlations between extent of remapping and intensity of phantom limp pain
- Stimulus on lip, on digit on hand
- Both hemispheres show different things: broken side = D2 & D4 increased in size and moved closer
6
Q
What is dystonia?
A
- Co-contraction of agonist/antagonist muscles
- Can happen genetically or if you over practise a particular sensation e.g musicians
- Lots of overlap in areas of digits
7
Q
How to track rehab of dystonia?
A
- Rehab = changed organisation of map NOT to normal, but textbook level normal
- Changes in experience are mirrored in the map
8
Q
What is mirror box therapy?
A
- Amputee places intact hand in box and put amput on other size
- Look at mirror and intact hand moves and visual stimulation catches and feeling of amputation falls = reduction in pain
9
Q
What is proprioception?
A
- Muscle and joint senses
- Patient IW lost fine touch and proprioception
- Has no body sense when eyes are closed
- Regained ability to walk and use limbs again
10
Q
What is the body schema?
A
- Body can be updated based on experience and is plastic
11
Q
Difference between top-down/bottom-up
A
- Bottom up: info comes from env
- Top down: info coming from areas of brain
- Bottom up is being altered by previous experiences of the world = multiple maps
12
Q
What are neurobiological substrates?
A
- Multiple maps that only occur in particular areas e.g found different states of motor system
13
Q
What happens when info from different modalities conflict? (Rubber hand exp)
A
- Rubber hand illusion: Visual info comes from hand & proprioception comes from real hand
- Visual and tactile input synchronised
- Paintbrush strokes real hand behind barrier
- Can feel touch in fake arm
- Ask ppts to indicate with other hand where hand in experiment is = adrift to rubber hand
- More adrift = correlates to how much you think the hand is yours
14
Q
To what degree is the rubber hand incorporated into the body schema? (Exp)
A
- Induced rubber hand illusion in MRI scanner
- Made brisk stabbing movements with sharp needle
- Subjects reported feelings of ownership over hand and anxiety when threatened
15
Q
What was the brain activity in the rubber hand exp?
A
- Pre-supplementary motor area activated when real hand threatened. Also activated for fake hand.
- Activity in insula and ACC was correlated with degree to which individuals thought fake hand was real
16
Q
What is consolidation?
A
- Mechanisms that act to stablise and enhance memories over time
- Memories do not have to be declarative/procedural
- Changes to cortical map structure are a kind of memory
17
Q
What does consolidation require?
A
- Requires a signal to ensure changes that are of significance
- Basal forebrain has been studied in cortical projection
18
Q
What is the signal for consolidation?
A
- Neurons in NBM use Ach as neurotransmitter
- Ach is also neuromodulator: regulates firing of larger groups of neurons
19
Q
How to link the NBM and Ach to map plasticity? (Exp)
A
- Lesion studies: remove NBM and cortex is starved of cholinergic input = no D2&4 expansion = map does not expand
20
Q
What is auditory cortex plasticity?
A
- Map of frequencies not map of body (A1)
e.g looks like piano keyboard - Performed on rodents
21
Q
What was the experimental design for rodents?
A
- Naive rat and manipulated rat: tone represented in A1 = manipulated artificial signal
- Can reshape auditory map: some could not identify other tones because of the way their maps changed.
22
Q
How does cholinergic input modulate the way that cortical neurons respond to sensory stimuli?
A
- Neural modulation shws env subtly changes mapping
- Retuning the receptive fields within the sensory cortex by giving them an overwhelming signal
23
Q
What is the role of NBM and map plasticity in naturalistic learning?
A
- When linking map plasticity and NBM activity = no real learning as no task performed by rats
- Link map changes, forebrain activity and changes in performance on an actual task
- Lesioned NBM = more specific
24
Q
How did they experiment plasticity in naturalistic learning?
A
- Trained rats to retrieve sugar pellets through a slit using a forepaw
- One group had NBM lesion, other group fake lesioned
- Real lesion = lower accuracy & longer to acquire reaching task skill
- Looking at cotor cortex, elicited forepaw movement = 30% increased in fake lesion compared to untrained rats
- NBM lesioned rats forepaw area = decreased 22% (even when trained)
- Links impairment of learning with disruption of plasticity
25
Q
What is the importance of ACh
A
- Linkage of NBM to ACh
- Sensory input from env may signal HOW to learn
- ACh determines WHAT we learn
26
Q
How to increase cognitive enhancement?
A
- Drugs made for other things but enhance normal people’s conc & memory
- Subtly changing electric charge and change how neurons fire e.g torpedo fish for headache relief in roman times & dude that connected murderers bodies to batteries in a theatre to make them move
27
Q
What did Fritsch and Hitzig do?
A
- Electrical stimulation of cortex can produce movements & Performed this on dog brains
- Aided in development of functional localisation
- Scalp could modulate human brain function e.g depression
- Application of positive d-c current had a stimulating effect whereas a negative current inhibited
- Mostly forgotten after Electroconvulsive Therapy
28
Q
What is modern day electrical stimulation?
A
- Transcranial electrical stimulation
- Surface electrodes constant current stimulator: used as a modulator
29
Q
What was the meta-analysis for TES
A
- Not found to generate a significant effect on anything other than change Motot-evoked potentials (evaluates motor cortex)
- Cheap, easy to apply
- Very variable
- Meta analysis was dodgy as authors decided to throw away a lot of data
30
Q
Why are TES effects so variable?
A
- Differences in cortical anatomy between ppts
- Differences between electrode positioning between participants
- State-dependent effects of cortical activity between ppts
