Practice questions tutorial Flashcards
What happens during action potential
During the action potential the polarity of the membrane reverses from negative (at baseline) to positive (at the peak of the action potential).
What do small peaks on a plot repesent
The smaller peaks showing the membrane going from about -60 mV to about -40 mV are likely to be excitatory post-synaptic potentials (EPSPs), which (if strong enough) lead to action potentials. On this plot only some EPSPs are strong enough to lead to action potentials.
What technique can register field potentials non-invasively?
Electroencephalography (EEG)- its signal reflects changes in Field Potentials.
In the experiment illustrated on the right, subjects are asked to attend to one side of the screen, where a target shape may appear though sometimes the target is presented on the opposite side. Attending to the side where the target is presented results in an increased amplitude of the P1 and N1 (early) peaks in the ERP.
In which lobe would you expect this difference to be largest (Occipital, Frontal, Parietal or Temporal)?
The early ‘perceptual’ components of the ERP originate in the posterior regions of the brain (occipital lobe and inferior temporal lobe- we know this from microelectrode data), so they should be maximal over the posterior scalp. Because the visual field is represented contra-laterally (left hemi-field in the right hemisphere), the attentional modulation should be maximal over the ‘other’ side relative to the stimulus side, so over the right side of the scalp in this example.
What physiological process made the signal stronger in these voxels in one condition relative to the other?
The parts of the brain that are more active require more oxygen. This demand is met by an increase in blood flow into them. The freshly oxygenated blood contains more oxygen that can be used in these areas – which means that there is a temporary increase in oxy-haemoglobin and a temporary reduction in deoxy-haemoglobin. Because deoxy-haemoglobin reduces the MR signal, its reduction results in an increase in the signal.
What is the area of Psychology concerned with research on the effects of brain damage on behaviour called? What can brain damage reveal that brain measurement cannot?
The area of Psychology concerned with research on the effects of brain damage on behaviour is called Neuropsychology. The techniques that measure brain activity cannot determine whether the patterns of activity they measure are causally related to the psychological process under investigation (whether the activity is NECESSARY or ESSENTIAL). Neuropsychology can establish whether certain brain region or structure is causally related to a psychological process.
What is a “single dissociation” and what is a “double dissociation” in neuropsychology?
When a patient (or a group of patients) has a performance deficit in condition B, but has normal performance in condition A, this is a “single dissociation” between conditions A and B.
When some patients are impaired in condition B, but have normal performance in condition A, whilst other patients are impaired in condition A, but unimpaired in condition B – this is a “double dissociation” between conditions A and B.
Why is a double dissociation seen as providing more insight than a single dissociation?
A single dissociation can reflect a qualitative difference between experimental processes, with the two conditions relying on different sets of processes. However, it can also reflect a quantitative difference, with both conditions relying on the same set of processes, but with one condition being somewhat more vulnerable to the effects of damage.
A double dissociation is harder to explain as a quantitative difference where one condition is generally more vulnerable to the effects of damage. It therefore more likely reflects a true qualitative difference in the underlying processes.
What can TMS do that brain-measurement techniques such as fMRI or EEG cannot?
Brain measurement techniques such as fMRI or EEG are fundamentally limited in that they can reveal correlations between brain activity and behaviour, but they cannot determine whether brain activity causes behaviour – TMS can do the latter.
Why is it often said that TMS elicits ‘neural noise’?
Although TMS does make a loud click when it is switched on, the term ‘neural noise’ refers to something altogether different. It refers to the fact that the ionic currents TMS induces in the brain disorganise the ongoing neural activity- it introduces ‘processing’ noise.
