3.1 Methods of Studying the Nervous System

Question 1

What are the non-invasive methods of studying the brain?

Answer 1

• C(A)T scans
• MRI scans
• fMRI scans
• electroencephalography (EEG)
• event related potentials (ERPs)

Question 2

What are the invasive methods of studying the brain?

Answer 2

• intracellular recording
• extracellular recording
• electrical stimulation
• optogenetic stimulation

Question 3

Which type of method can only be used on animals?

Answer 3

those that are invasive

Question 4

What are C(A)T scans?

Answer 4

• a computer assisted X-ray procedure
• X-ray scanner is rotated 1° at a time over to 180°
• all 180 images are stitched together
• horizontal slices (through an 3D image (tomogram)
• reveals structural abnormalities, such as cortical atrophy or lesions from a stroke/trauma

Question 5

What are MRI scans?

Answer 5

• a strong magnetic field (up to 3 tesla) causes hydrogen atoms to align in the same orientation
• a radio frequency wave is passed through the head, protons emit electro magnetic energy as they ‘relax’
• the MRI scanner is tuned to detect radiation emitted as the protons relax
• different tissue types produce different signals
• computers reconstructs an image

Question 6

What is an fMRI scan?

Answer 6

• functional so works out which area of the brain is active when undergoing certain tasks
• O2 and glucose are supplied by the blood as fuel for brain (O2 found in haemoglobin)
• the brain does not store this fuel so blood changes as needs arise
• changes are region specific
• images brain hemodynamics (blood oxygen level dependant signal: BOLD)

Question 7

What is an EEG?

Answer 7

• records electrical activity in the brain
• uses a net of electrodes on to the scalp

Question 8

What are the positives and negatives of an EEG?

Answer 8

+ has high temporal resolution
+ direct reflection of neuronal activity
+ less expensive than fMRI

• poor spatial localisation due to recordings made at the scalp
• better suited at answering questions about when cognitive processes happen, not where

Question 9

What are ERPS?

Answer 9

• event related potentials: how brain responds to input
• background EEG signal can be removed by trail-averaging revealing the response of a brain region to stimuli
• portions of the EEG time-locked to an event are averaged together
• neural signature for the event is extracted

Question 10

What do ERP waveforms tell us?

Answer 10

• information about the neural basis of processing is provided by the difference in activity

Question 11

What are the two electrophysical invasive techniques?

Answer 11

• intracellular recording
• extracellular recording

Question 12

How does an extracellular recording work?

Answer 12

• sits just outside the cell next to the membrane

Question 13

What are the two invasive stimulation techniques?

Answer 13

• electrical
• optogenetic

Question 14

How does electrical stimulation work?

Answer 14

• brains use change in electrical activity properties to communicate
• we can use electricity to turn cells on in areas of the brain and assess the animals behaviour

Question 15

How does optogenetic stimulation work?

Answer 15

• allows us to control brain activity
• extracts optical pigment which sticks inside a virus
• this then injects into neurons
• the cells are now sensitive to light and can turn the neurons on