Brain Activity & Plasticity Flashcards
(37 cards)
1
Q
Describe electroencephalography (EEG)
A
- EEG
- Electroencephalography → Equipment/ method
- Electroencephalogram → Data output
2
Q
What are the strengths of an EEG?
A
- Good temporal resolution
- Discriminates very brief events in time
- Relatively cheap
- Portable
- Possible to record while people are moving around
- Enables detection of epileptic seizures
- Safe and well tolerated by participants
3
Q
What are the limitations of an EEG?
A
-
Poor spatial resolution
- Difficult to determine precisely from which area of the underlying brain the signal has come
- Typically only detects activity on the surface of the cortex
- Hard to detect activity from more central regions of brain → Electrodes only attached to skull
4
Q
What is electrophysiology?
A
- Action potentials in giant axon of Atlantic squid recorded
- Hodgkin and Huxley in 1952
- Microelectrodes for single neurons
- Mapped…
- Sensory cortex
- Motor cortex
- Development and functional organisation of the visual system
5
Q
What is the strength of electrophysiology?
A
- Records directly from individual neurons
- Is the best method to use if you want to know what the neurons are doing
6
Q
What are limitations of electrophysiology?
A
-
High risks of infection
- Technique is invasive → Penetrates brain
- Only possible to record from a few neurons at a time (100) → Can only record individual neurons or small network activity
7
Q
What is Magnetic Resonance Imaging (MRI)?
A
- Exploits magnetic properties of brain tissue
- Coil generates very strong magnetic field
8
Q
Describe structural imaging with MRI
A
- Magnetic field passes through person’s head → Hydrogen atoms align with magnetic field
- Radio frequency waves temporarily disrupt alignment
- Flip at angle to field
- Flip back to OG position at end of radio pulse
- Release energy absorbed from pulse
- Energy sensed by coil of wire = Signal
- Analysis software converts detected signals into detailed images of brain
- Different areas have different amounts of water = Emit different signals
9
Q
Describe Diffusion Tensor Imaging (DTI)
A
- Small fiber bundles that are not visible with normal MRI
- Detect large axon tracts (white matter) that flow through the brain and connect different regions of cortex
- Bundles of white matter will not move randomly
- Direction parallel to axons that make up the bundles
- Colours added to distinguish between different bundles of axons
- Same equipment as MRI
10
Q
Describe functional imaging with fMRI
A
- Blood Oxygen Level Dependent signal (BOLD) tracks the ratio of oxygenated vs deoxygenated blood (NOT neurons but areas around neurons)
- Cognitive processes use energy = Use oxygen from blood (increase blood flow)
- Oxygenated blood → Doesn’t distort surrounding magnetic field
- Deoxygenated blood → Distorts surrounding magnetic field = Blood vessels more visible
Reflect chnages in oxygen levels in blood (not neurons) = Delay of a few seconds
11
Q
What are the strengths of MRI?
A
- High spatial resolution
- Identify exactly where in the brain different structures are/ function is occurring
- Identifies specific anatomical/ structural and functional properties of different brain regions
12
Q
What are the limitations of using MRI?
A
- Very expensive
- Large equipment that requires a specialist facility
- Safety risks associated with the large magnet = No metal enters MRI room
- Requires specialist staff with radiography training
13
Q
What are Positron Emissions Tomography (PET) scans?
A
- Use radioactive substances known as tracers to visualise glucose metabolism or NT/ receptor function
- Can also use radioactive tracers to bind selectively to proteins of interest
14
Q
What is the strength of PET scans?
A
- Detects different chemicals in brain assoicated with metabolism or specific NT levels/ receptors
15
Q
What are the limitations of PET scans?
A
- Expensive and requires specialist facilities and staff
- Low spatial resolution compared to MRI
- Radioactive tracers injected into participants blood → Considered to be safe but has risks that are managed
16
Q
Describe modifying the brain in a medical context
A
- Psychiatric and neurological conditions associated with abnormal brain functions
- Treatment might involve removal of sections of abnormal brain tissue
- Drugs can be used to selectively target abnormal function of specific NT systems
17
Q
Describe using modifications to enhance brain function
A
- Improvement of healthy function to above or better than normal
18
Q
Compare brain imaging to modulation
A
- Imaging provides correlational information
- Modulation provides information about causation
- Whether a given brain region is necessary for a particular task
19
Q
What are ablation studies?
A
- Deliberate lesions to brain → Relatively high degree of precision
- Ablation = To carry away
- Research → Only animals
- Treatment → Humans
20
Q
What is a frontal leucotomy?
A
- Altering frontal lobe in order to treat psychiatric disorders
- Removal of frontal lobe in chimpanzee = Calmer and more cooperative
- Had initial impression of improvements but lead to personality consequences
- Apathy
- Emotional unresponsiveness
- Inability to plan
Developed by Egas Moniz
21
Q
What are the two methods for a frontal leucotomy?
A
- Leucotome inserted into one of several holes drilled in skull
- Wire extruded from tip
- Leucotome rotatedd to remove core of tissue
- Cutting implement inserted above eyelid
- Push through base of skill
- Rocked from side to side to slice through frontal lobes → Separate from rest of brain
22
Q
What is electroconvulsive therapy (ECT)?
Non-invasive electrical brain stimulation
A
- Stimulate seizure to treat psychiatric conditions
- Used to treat range of conditions → Now only depression
- Mechanism of action is unknown
- Electrical stimulation needs to be strong enough to induce seizure
IMPORTANT
23
Q
What is transcranial direct current stimulation (tDCS)?
Non-invasive electrical brain stimulation
A
- Weak electrical pulse
- Battery connected to sponges attached to head
- Highly debated
- Improvement may have been because of high arousal
24
Q
What is transcranial magnetic stimulation (TMS)?
Non-invasive electrical brain stimulation
A
- Coil carrying an electrical current generates brief, focal magnetic pulse which activates a small region of cortex underlying the coil
- Activation acts like a ‘virtual lesion’
- Temporarily disrupts tissue for a few hundred milliseconds
- Painless unless it triggers a muscle contraction
- Treats depression, OCD
25
Describe synaptic plasticity
* Adaptibility of neural connections
* Existing synapses can be strengthened or weakened (shrink or removed)
* New synapses can be generated
* Pattern of activation can impact future activation of neurons
26
Describe long-term potentiation (LTP)
* Repeated stimulation (AP) → Synaptic connection becomes stronger
* Post synaptic neuron becomes more 'sensitive' to NT release
* More likely to reach AP threshold
* ↑ Post-synaptic potential = Neural signal faster
## Footnote
Hebb's Rule or Hebbian Learning → Neurons that fire together wire together
27
Describe long-term depression (LTD)
* Weakening of synaptic connections due to lack of use
* Less sensitive to NT
* Less likely to fire
## Footnote
Use it or lose it
28
What is neurogenesis?
* Brain's ability to generate new neurons (replace dead ones)
* Restricted to hippocampus (consolidation) and olfactory bulb (detection of smell)
29
Relate neuroplasticity to brain rehabilitation
* Neurogenesis does not occur in all brain regions
* Entire brain cannot replace damaged tissue (only hippocampus and olfactory bulb)
* Sustained damage after strokes/ brain damage → Neurons typically not replaced
* However still large capacity for adaptation of surviving neurons due to LTP + LTD
* ↑ Heathy brain regions
* ↓ Damaged areas
* Improved function and recovery through retraining brain to compensate for loss
30
Describe motor control
* Performing an action requires involvement from different brain areas
* Sensory signals (sight, hearing)
* Brain selects signals relevant to task
31
Describe the behavioural component of emotional responses
* Muscular changes that are appropraite to the situation that elicits them
* E.g. Aggressive posture = Defence
* E.g. Submissive posture = Fear
32
Describe the autonomic component of emotional responses
* Physiological changes induced by the autonomic NS
* Facilitate behavioural responses
* E.g. Sympathetic NS increasing heart rate, dilating pupils
33
Describe the hormonal component of emotional responses
* Hormones reinforce autonomic changes
* E.g. Adrenal gland secretes adrenaline → Further increase blood flow to muscles, nutrients in muscles = glucose
34
Describe the integration of emotional responses (3 components)
* Amygdala coordinates emotional response
* Behavioural, autonomic, hormonal
* Sends appropriate signals to autonomic and hormonal
* Can impact cognitive and behavioural performance
* Nervous → Noradrenaline
* Impulsive decisions + Errors
* Emotional responses help integrate sensory signals + Coordinate appropriate regulation of brain and body
* Modifies person's experience to match context
35
What is the supplementary motor area (SMA)?
* Medial surface of the brain
* Rostral to primary motor cortex
* Behavioural sequences → Well-learned sequences of responses
36
Describe the two descending tracts within the primary motor cortex
* Lateral group
* Control of independent limb movements → Hands and fingers
* Right and left make different movements E.g. One moves, other stays still
* Ventromedial group
* Automatic movements
* Posture and locomotion
37
What is the motor association cortex?
* Includes supplementary motor area and premotor cortex
* Planning movements
* Imitating the actions of other people → Understanding functions of other's behaviour
