Peer mentoring Flashcards
What are the limitations of block design?
- highly predictable occurrence of stimuli
- inflecible for more complex tasks
- ecological validity
- cant seperate trials by performance
What are advantages of event-related design?
- flexibility and randomisation
- post hoc sorting
- can look at novelty and priming
- can look at temporal dynamics of response
What does a BOLD signal measure?
the magnetic properties of oxygenated v. deoxygenated blood
What is a limitaion of the block design in MRI studies?
it is highly predictable
What are the 6 preprocessing steps?
- high pass filtering
- motion correction
- slice time correction
- coregistration
- normalisation
- spatial smoothing
Ultimately we want to do statistics on GROUP activation maps. Thus, we must get all of the brains into a ‘standard space’. How do we do this?
Complex algorithms to warp each subject’s brain into the shape of a TEMPLATE BRAIN
What was the original standard based on?
The brain of a 60-year-old French Woman
Why do we no longer use the original standard?
her brain may not be representative of all brains
What standard do we use now for comparing brains?
Montreal Neurological Institute (MNI) space
How was MNI created?
352 scans on normal controls, all right-handed
Advantages of whole brain analysis?
■ No prior hypothesis about areas involved needed.
■ Includes the whole brain.
Disadvantages of whole brain analysis?
■ Can lose spatial resolution –> due to inter-subject averaging.
■ Can produce meaningless lists of areas. Hard to interpret.
■ Depends highly on statistics and selected threshold.
■ Multiple comparisons problem.
Advantages of region of interest?
- hypothesis driven
- avoids multiple comparison problem
- simple
- generalisable
Disadvantages of region of interest?
■ Easy to miss things going on elsewhere in the brain.
■ Not always simple how to define ROIs.
Limitations of fMRI
- data is correlative
- temporal resolution is low
BOLD signal is arbitrary… meaning what?
it has no stbale baseline
How fast is the BOLD signal?
it is slow. peaks 4-5 seconds after stimulus onset and about 16 seconds to return to baseline
What are the two types of designs that can be used in an MRI scan?
block design (long periods of alternating task performance) and event-related design- trials of different conditions are randomly intermixed
How do we analyse results?
- multiple regression
- multiple regression per voxel
- contrast
- threshold of p<0.05
What are the three major sulci?
central, lateral and parietal-occipital
Where are basic physiological and metabolic processes controlled?
by groups of neurons in the brainstem, including thalamus and hypothalamus
What are the types of functions controlled in this area?
respiration, digestion,, glucose, metabolism, arousal…
What are some specific groups of neurons?
- reticular formation (control of arousal and sleep)
- suprachiasmatic nucleus (circadian rhythm)
- ventromedial nucleus (blood glucose into body fat)
What is the function of the cirpus callosum?
to allow messages to travel between hemispheres
where is body temperature controlled?
brain stem
Both perception and motor control have a _____ organisation
hierarchical
What is the correct order of inforamtion processing in perception?
primary visual/auditory/sensory motor areas -> second sensory areas -> association areas
How can we determine causality?
- neurosurgery
- stroke
- brain trauma
- neurodegeneration
- infection
What is neuropsychology
examines the effects of brain damage on cognitive abilities and behaviour
When did neuropsychology emerge?
Paul Broca in the 19th century
Who won the nobel prize for medicine in 1981?
Sperry and Gazzaniga
What surgery did Sperry and Gazzaniga’s patients have?
callosotomy
What is the WADA test
putting one hemisphere to sleep and seeing hwo it responds to stuff (e.g. holding a spoon)
What is hemispatial neglect?
the brain doesnt recognise an area of space
who studied temporal lobe amnesia?
brenda milner with HM
What are the key approaches in neuropsychology?
classic (localisation) and cogntiive (determine cognitive architecture)
What does cognitie neuropsychology rely on?
the logic of dissociation
what are the electrophysiological methods?
micro-electrode recordings and EEG
Eval of micro-electrode recordings
- The most direct and precise measure of brain activity
- However, because it is invasive, its use is very restricted both in terms of the subjects available and brain areas that can be investigated in patients
- High temporal resolution as it measures spikes and post-synaptic potentials
- High spatial resolution as it measures activity at the source
Eval of EEG
•Non-invasive
•High temporal resolution
> it measures fast electrical processes (post-synaptic potentials)
•Low spatial resolution
> the location of activity is difficult to infer
why is EEG not sensitive to spiking activity?
- the spatial extent of action potentials is too small and the time too short for them to be reflected in the EEG
- of the shape of the electrical fields they elicit
What is not an advantage of micro-electrode recordings?
A.Most direct and precise measure of brain activity
B.High temporal resolution
C.High spatial resolution
D.Being highly invasive
D) being highly invasive
Which is not a characteristic of EEG?
A.Being highly invasive
B.Non-invasive
C.High temporal resolution
D.Low spatial resolution
A) being highly invasive
WHat happens in the EEG frequencies as sleep becomes deeper?
Gradual slowing i.e. Lower frequencies
What is REM sleep?
Rapid Eye Movement sleep. EEG frequencies are very fast. During REM most vividly recalled dreams are believed to occur
What is higher frequency in the EEG associate with
Greater cortical activity
What area of the cortex is recordered to assess conscious awareness in patients in a vegetative state?
THe motor cortex
The first brain measurement technique to be used for this purpose was FMRI why might we use EEG instead?
EEG is cheaper and more portable - it can easily be deployed to the patient’s bedside
Which is not a diagnostic criteria for a vegetative state?
A. No overt motor responses to commands
B. No elaborate ‘voluntary’ or ‘willed’ behaviours from the upper or lower limbs
C. No evidence of visual orientation
D. No eye fixation greater than 5 seconds or tracking of visual OR auditory stimuli
E. Verbal Response
E) verbal response
What did Cruse et al find?
3/16 patients activated areas of the motor cortex according to the instructions
What discharges occur in patients suffering with epilepsy?
Abnormal/Excessive synchronisation of post-synaptic potentials, resulting in large amplitude discharges.
What is ictal activity?
during seizures
what is inter-ictal activity
between seizures
How are stimuli compared?
a. With ANOVA.
b. Qualitatively.
c. Separately averaged.
d. Just by looking.
C) separately averaged
What does SOA stand for?
stimulus onset asynchrony
what is the PRP paradigm
Psychological Refractory Period – Present 2 tasks in rapid succession. E.g. Tone discrimination or Word Relatedness.
What did Lien et al (2008) find?
Processing in Task 1 interferes with the processing of the target meaning in task 2. SO… it suggests that meaning is not accessed automatically.
What is SOA
the amount of time between stimulus 1 and stimulus 2
what is the inverse problem?
Inferring cortical generators from known scalp potentials. This is highly uncertain. There is an infinity of cortical current distributions that could result in one scalp distribution.
What are 3 EEG source estimation techniques
Epileptic EEG distribution on scalp
Localisation based on EEG source estimation
Localisation by correlation with concurrently acquired fmri data
WHich is not a strength of EEG:
a. High temporal resolution
b. It can provide detailed temporal information about processing a stimulus
c. Good spatial resolution
d. All of the above
c) good spatial resolution
which of these are not a weakness of EEG:
a. Limited spatial resolution
b. Cannot Localise activity with precision/confidence due to the complexity of the inverse problem
c. Good Temporal resolution
d. All of the above
c) good termporal resolution
Facts about micro-electrode recordings
- highly invasive: require surgery
- high temporal resolution: measure spikes and post-synaptic potentials
- high spatial resolution: measure activity at the source
facts about EEG
- non-invasive (innocuous)
- measures post-synaptic potentials
- high temporal resolution, sicne it measures fast electrical processes
- low spatial resolution location of activity; difficult to infer
Facts about PET
- moderatly invasive: radioactivity is introduced into the body
- measures indirect metabolic correlates of neural activity (e.g. blood, glucose)
- can measure synaptic transmission (e.g. labelling receptors)
- relatively high spatial resolution precision
- low temporal resolution because it measures slow processes
Facts about fMRI
- non0invasive (innocuous)
- measures indirect metabolic correlates of neural activity (e.g. blood)
- high spatial resolution (highest among all techniques)
- low temporal resolution, because it measures slow processes
How are neural signals transmitted?
- electric synapse: gap junctions connecting the cytoplasm of two neurons
- Chemical synapse: Signal transmission within a spiking neuron
What is the process of the electric synapse
A. Instantaneous current flow
> very fast transmission of electric signal across connexons, producing virtually no time delays
B. They are found where fast responses and/or synchronisation of activity is required.
> Fast action: Commanding escape responses (crayfish, fish)
> Synchronised activity: Inhibitory neurons in mammalian brain, eye-moving muscles
What is the process of the chemical synapse
A. Resting potential
> Membrane potential when the neuron is at rest (=no signal transmission)
B. Depolarisation
> Graded potential before reaching threshold (-55mV) when the neuron is excited (received signal)
C. Action potential
> Spikes are generated in the integration zone of a neuron if depolarisation reaches threshold (-55mV).
> Signal transmission inside neuron.
D. Signal transmission to next neuron
> It starts when action potentials reach in the output zone of a neuron.
What is a G protein-coupled receptr
It consist of three subunits, influencing adjacent ion channels.
When activated by a conformational change, G protein can interact directly with ion channels or control the release of another messenger molecule inside the postsynaptic cell.
1. Which are NOT typical ion channels? A. Voltage-gated channels B. Leak channels and ion pumps C. Ligand-gated channels D. Regular channels
D) regular channels
What are teo solutions to signal loss caused by increased distances
Long neurons with thicker axons - found in squids, and invertebrates.
Myelinisation of axons (Schwann cells) - mostly in vertebrates
What is neuroglia
Cells that assist the signal propagation (Schwann cells) and provide nutrients to neurons.
In what way are the Nodes of Ranvier involved in saltatory transmission
The neural membrane is exposed at the nodes of Ranvier for ion conductance through voltage-gated channels for Saltatory conduction.
What 2 things determine when a signal is picked up and by which signal is picked up?
- Type of neurotransmitter
2. Duration of neurotransmitter release
What is temporal summation
If the neurotransmitter is released for longer time into the synaptic cleft, then the postsynaptic potential is stronger.
What is spatial summation
If postsynaptic potentials, fired from two different neurons, arrive together in the integration zone, they are summed up.
What is EPSP
depolarisation
What is IPSP
hyperpolarisation
Examples of excitatory sunapses
glutamate, aspartate, nicotinic
examples of inhibitory synapses
GABA, glycine, muscarinic acetylcholine.
What is a spiking neuron
if the membrane at the integration zone is depolarised above a threshold, an action potential will be generated.
The more excitatory input arrives →
the stronger the output signal.
The more inhibitory input arrives →
the weaker the output signal/the neuron may not even fire.
What happens if 2 EPSPs are summed to reach the threshold
An action potential will be generated
What happens if 2 IPSPs are summed?
An action potential will not be generated, so the signal is not transmitted.
WHETHER A SIGNAL IS TRANSMITTED OR NOT DEPENDS ON…
HE SUM OF THE RELATIVE STRENGTHS OF EPSPs AND IPSPs THAT ARRIVE AT THE INTEGRATION ZONE TOGETHER WITHIN A GIVEN TIME WINDOW.
How is information coded in neural networks?
- spatial/temporal summation
- feedforward circuits
- feedback loop
What is spatial/temporal summation
determine the strength of the signal when it is passed on from one neuron to the next.
What is feedforward circuits
distribute the signal to many neurons through divergence of their connections, or is determined by collecting signals from many neurons through convergence.
What is feedback loops
(positive/negative) provide direct or indirect input influencing signals and thus information.
Is there a start/end in a neural network?
The observer defines the start and end.
Are networks hierarchical?
yes
Is one neuron a ‘queen’?
No, but there could be some small bosses or gatekeepers, as proposed by the grandmother cell/agnostic cell hypotheses.
Are networks clearly segregated from each other?
No, they can branch out into parallel streams, have feedback loops, share neurons with other networks, and change over time.
Which of these is an excitatory synapse?
a. Nicotinic acetylcholine
b. Muscarinic acetylcholine
c. Glycine
d. None of the above
a. nicotinic acetylcholine
Which of the following statements is false?
a. Neuroglia assist cell propagation
b. Myelination causes the problem of signal loss.
c. EPSPs/IPSPs arrive at the integration zone
d. Spiking neurons can generate action potentials.
b. Myelination causes the problem of signal loss.
What is non-declarative memory
Skill learning
Conditioning
Priming
What is declarative memory
Semantic memory (facts) Episodic (what, when, where)
What is Hebb synapse
The site of contact between neurons(synapse) plays a role in memory formation.
Hebbian theory claims that an increase in synaptic efficiency comes from a presynaptic repeated stimulation of the postsynaptic cell.
Hebb’s synapse in steps
- Cell A repeatedly excites cell b
- This causes a metabolic change
- A’s efficiency at firing B is increased
In what ways can the efficiency in synapses be increased
- Temporal Filtering: change in selectivity for the frequency range of spikes arriving in the axon terminal
- Gain Control: change in the amount of neurotransmitter released for a given signal
- Presynaptic facilitation or depression
What is presynaptic depression
This a form of synaptic plasticity studied in Aplysia.
The withdrawal reflex is mediated by sensory neurons that synapse to the motor neurons
After repeated stimulation over an hour, habituation occurs because the sensory neurons release less neurotransmitter to the motor neurons
If this process carries on over several days, there is a long term habituation caused by a retraction of some synaptic terminals from the sensory to motor neurons
Which sequence would cause associative learning in Pavlov’s Dog?
a. Food (US) preceding a sound (CS)
b. Sound (CS) preceding food (US)
c. Food (US) preceding salivation (UR)
b. Sound (CS) preceding food (US)
Are London taxi drivers hippocampi bigger or smaller than bus drivers
ANSWER: BIGGER
London taxi drivers hippocampi is larger than bus drivers.
- Greater grey matter volume in the mid-posterior hippocampi
- Less volume in anterior hippocampi
What three pathways in the hippocampus are involved with spatial memory formation
- Mossy fibre pathway (dentate gyrus to CA3 pyramidal cells).
- Perforant pathway
(input from entorhinal cortex) - Schaffer collateral pathway (CA3 to CA1 pyramidal cells)
CA1 pyramidal neurons (in the perforant pathway) have 2 glutamate receptors in their dendrites
QUESTION: What are these 2 receptors called?
- AMPA receptors
a. Ionotropc (ligand-gated ion chanels)
b. Open if glutamate binds to them → Na+ flow into postsynaptic neuron
c. EXCITATORY - Na+ influx depolarises EPSPs - NMDA receptors
a. Ligand and voltage gated
b. Cell resting = blocked by Mg2+
c. Binding glutamate is necessary but alone insufficient to open them
What 2 conditions are required to open NMDA receptors?
Binding of glutamate
Membrane depolarises above the threshold expelling the Mg2+ plug
Is hippocampal LTP the mechanism underlying spatial learning?
YES - Increasing evidence from various studies suggest this.
What’s the most economical way to inactivate the transmitter?
A: Re-uptake
B: Diffusion
C: Enzymatic degradation
D: Axonal propagation
A) re-uptake
Which phases of the synaptic sequence can drugs alter?
- Some act as early as the propagation of the action potential
- Others may influence the release of the transmitter
- Others modulate how the transmitter interacts with the post-synaptic channels (receptors)
- Finally, some alter the presence of the transmitter in the synapse by modulating its inactivation and recycling
Which chemical blocks sodium channels in the axon’s membrane? A: Dopamine B: Amphetamine C: Tetrodotoxin D: Tetanospasmin
C) tetrodotoxin
Describe two substances that influence the release of the transmitter
Tetanospasmin, which interferes with the vesicles of the neurotransmitter GABA fusing with the cell membrane.
This reduces the amount of GABA released into the synapse.
Botulinum toxin interferes with the release of Acetylcholine at nicotinic synapses, by preventing the vesicles from fusing with the cell membrane
Amphetamine facilitates the release of dopamine from the vesicles when these fuse with the membrane
Curare occupies acetylcholine’s receptors in inhibitory (nicotinic) synapses, blocking them and causing paralysis
A: TRUE
B: FALSE
B) False
interacts with excitatory synapses
What is an agonist
Imitates the behaviour of the neurotransmitter (NT)… INCREASING its effect.
example of an agonist
→ HEROIN; artificially modified form of morphine (opium).
→ It is an AGONIST of ENDORPHINS. Natural body chemicals that bind to OPIATE RECEPTORS and reduces pain and induces relaxation.
What are 2 Other Agonists and What Do They Bind To and What are they Involved in?
Marijuana (Cannabis) → Contains THC.
Agonist of Anandamide; Natural body chemical which binds to CANNABINOID RECEPTORS.
Involved in emotion, pain, appetite and memory.
Tobacco (Nicotine) → Stimulates NICOTINIC RECEPTORS. Agonist for ACETYLCHOLINE. (ACh)
Short-live generalised excitatory effect, e.g.. Increases blood adrenaline level.
•What are the 3 stages of neurotransmitter inactivation and recycling process….
1.Diffusion: Transmitter is lost in the inter-cellular space
2. Enzymatic Degradation: Enzymes break down the transmitter.
3. Re-Uptake (uptake): Transmitter is recycled either in pre or post-synaptic neuron.
This is the most economical way to inactivate the transmitter as it saves synthesis resources
Why is chocolate technically not “addictive”?
Because anandamide (agonist = THC) and phenylethylamine (related to amphetamine) are not found in amounts considered to have a substantial effect.
For the treatment of what disorder is the drug “Prozac” used and how does it work?
Prozac/Fluoxetine is used for the treatment of depression. It is an SSRI (Selective Serotonin Reuptake Inhibitor). It works by inhibiting the absorption of serotonin via the serotonin transporter without affecting other monoamines (e.g. dopamine).
Other treatment drugs for depression are MAO inhibitors and Tricyclic antidepressants.
What are benzodiazepines used to treat and how do they work?
GABA agonists used to treat anxiety disorders (characterised by deficits in GABA-ergic transmission).
They do not bind to the same receptor as GABA itself, therefore, are a non-competitive agonist.
Beta Blockers such as propranolol can also be used to treat anxiety disorders as they address the physiological symptoms such as increased heart rate.
SSRI’s are also commonly prescribed for anxiety.
What are neuroleptics used to treat and how do they work?
Neuroleptics such as Haldol are anti-psychotic drugs used to treat schizophrenia and other psychotic disorders (e.g. bipolar and major depressive disorder). They block the transmission of dopamine by binding to dopamine receptors without opening ion channels (they are antagonists).
Atypical Antipsychotics such as Quetiapine (seroquel) are also used.
What does cocaine do, what is the overall effect of amphetamines and what symptoms can this elicit?
Cocaine blocks the transporter of noradrenaline and dopamine, thus interfering with their re-uptake and boosting their effect. The overall effect is a boost in monoamine transmission (dopamine, noradrenaline, serotonin).
Increasing monoaminergic (especially dopaminergic) transmission can induce schizophrenia-like symptoms. Hence why you feel elation after ingesting the substance. It is important to note use of these drugs can elicit a psychotic ‘break’.
Antagonist = “You are antagonising me”
Inhibiting from doing something.
Agonist = “You are agonising me”
Stimulating a reaction.
Antagonist (Inhibits) – binds to post-synaptic receptors and…
blocks the binding of naturally occurring neurotransmitters.
Agonist (Stimulates/Imitates) – Binds to post-synaptic receptors and …
stimulates action potential.
What is the difference between a synaptic receptor agonist and antagonist? Illustrate your answer with a named receptor and its agonist and antagonist.
Antagonist (Inhibits) – binds to post-synaptic receptors and blocks the binding of naturally occurring neurotransmitters.
Agonist (Stimulates/Imitates) – Binds to post-synaptic receptors and stimulates action potential.
Example: GABA + Alcohol. In low doses alcohol acts as an agonist and in high doses acts as an antagonist. In very high doses alcohol destroys cell membranes and causes brain death.
Muller looked at the main reasons reported for drug use, can you name some?
- Improved Social interaction
- Facilitated sexual behaviour
- Improved cognitive performance and counteracting fatigue
- Facilitated recovery from and coping with psychological stress
- Self-medication for mental problems
- Sensory curiosity - Expanded perception horizon
- Euphoria, hedonia, and high
- Improved physical appearance and attractiveness
Effects of cocaine on the brain
Cocaine addiction is associated with brain damage risks, appearing minutes/hours after consumption
E.g. Seizures, early strokes, and lesions resulting in movement disorders
Along with reduced volume of the inferior portion of the frontal lobe
What is heroine associated with
A reduction in grey matter (e.g. in the frontal temporal regions
A reduction in white matter (spongiform leukoencephalopathy)
Brain hypoxia (reduced oxygen availability
Stroke (loss of blood supply)
Cerebral edema (water saturation)
Myelopathy (paralysis produced by spinal lesions)
What is alcohol linked to
Alcoholism is linked to Wernicke-Korsakoff syndrome
Wernicke’s encephalopathy -> brain shrinkage
- Characterised by changes in mental state and inability to concentrate, apathy.
- Korsakoff syndrome is characterised by anterograde amnesia, language problems and difficulty with movement.
- Korsakoff syndrome can sometimes be treated with thiamine supplements.
What did Yucel et al,2008 find
Cannabis use is associated with a reduction in brain volume, especially in the hippocampus and the amygdala
What did Moore et al, 2007 find
Longitudinal research shows that cannabis use is associated with development of psychotic symptoms
What are the causes of addiction
- Effects of drug-related cues - cue reactivity
- Effects of drug tolerance and withdrawal
- Drugs influences on processing of rewards and incentives (pleasure & motivation)
- Self medication
What is drug tolrance
reduced reaction to the same dose of a drug after repeated use.
what is drug withdrawal
symptoms which appear when stopping or reducing drug intake after having developed drug dependence, for example: sweating, fatigue, vomiting, insomnia, irritability and shaking.
What is tolerance a form of?
homeostatic protection, reducing the potentially harmful effects of the drug
•e.g. by raising heart rate in heroin addicts
but can lead to overdose
What is the Unviersal Reinforcement Circuit?
Involves activation of the VTA or Nucleus Accumbens (situated in the Basal Ganglia)
What did Wise et al (1978) find?
Administration of a dopamine antagonist (PIMOZIDE) increases lever pressing, even WITHOUT REINFORCEMENT…
What is the Incentive Salience Theory? How does it differ from the Anhedonia Hypotheses?
- Dopaminergic circuit involving NA (nucleus accumbens) and VTA (ventral tegmentum area) is responsible for the motivation to obtain a drug, not the pleasure obtained from it.
- Sensitisation to drugs occurs because addicts drug use strongly potentiates (increases the power of) the motivation-related dopaminergic synapses in the brain, with repeated use of the drug leading to greater responses in the dopamine circuit, independently from the effects of the drug on euphoria.
- Differs from Anhedonia hypotheses as…
- Anhedonia hypotheses relates to PLEASURE (reward).
- Incentive salience theory relates to MOTIVATION (incentive).
