Electrophysiological recordings of brain activity

Question 1

Widely used electrophysiological techniques

Answer 1

1. micro-electrode recordings
2. EEG/ERP

Question 2

Widely used metabolic brain imaging techniques

Answer 2

1. PET
2. fMRI

Question 3

Micro-electrode recordings

Answer 3

1. electrical activity can be measured from brain tissues using very thin electrodes inserted into the tissue
2. data is acquired from single brain cells
3. firing rate is typically measured - frequency of action potentials generated
4. highly invasive - requires surgery
5. high temporal resolution - measures spikes and post-synaptic potentials
6. high spatial resolution - measure activity at the source

Question 4

Quiroga and colleagues

Answer 4

1. recorded spike rates of cells in the medial temporal lobe in patients undergoing monitoring for surgery
2. many showed selective responses to a specific item irrespective of view
3. some cells that responded to the face also responded to the name of the person, showing that they were not simply coding for visual
4. pattern of very selective responses was also seen for other pictures

Question 5

advantages and disadvantages of micro electrode recordings

Answer 5

1. most direct and precise measure
2. invasive

Question 6

EEG

Answer 6

1. EEG is the change in voltage recorded from sensors on the scalp
2. EPSP (Excitatory postsynaptic potential) at the dendrite end, difference in electrical charge which is what is picked up by EEG
3. EPSP - temporary deficit of positive charge develops in the area of extracellular space where sodium enters the neuron, temporary surplus of positive charge develops in the area near the soma where potassium exits cell
4. EEG is not sensitive to spikes because the spatial extent of action potentials is too small and time too short
5. EEG is less sensitive to brain structures that are further down from the scalp, because electrical fields diminish with distance
6. Can use ERPs to examine how rapidly the EEG signal oscillates
7. Non invasive
8. Measures post synaptic potentials
9. High temporal resolution since it measures fast electrical processes
10. low spatial resolution - location of activity difficult to infer

Question 7

ERP

Answer 7

1. Refers to the methodology of analysing EEG recordings
2. by extracting from the EEG segments time-locked to specific events
3. different sections of EEG are related to different types of stimuli are separately averaged and then compared
4. labelled by order or latency
5. the size of peaks is related to stimuli/tasks
6. EEG is obtained from the surface of the head, each point on the head surface reflects cortical activity originating from distant regions, very difficult to precisely pinpoint the regions of the brain where particular ERP activity originates
7. EEG source estimation to pinpoint