Neuroscience and Clinical Semester 1 Week 3: Research methods in neuroscience Flashcards
What is a CAT scan?
- A computer assisted X-ray procedure
- An X-ray scanner is rotated 1 degree at a time over 180 degree
- Horizontal slices (tomogram)
- A contrast agent may be used to highlight specific areas
- Computer reconstruction to build a 3D image
- This can reveal structural abnormalities
What is an MRI?
- A strong magnetic field causes hydrogen nuclei (protons) to align in the same orientation
- The machine emits radio frequency pulses, causing the protons to spin out of alignment
- When the pulses are turned off, the protons emit electromagnetic energy as they return back to position.
- The MRI scanner is tuned to detect radiation emitted as the protons relax
- Different types of tissue produce different signals and a computer reconstructs image
- Good for soft tissues
What is an fMRI?
- Oxygen and glucose are supplied by the blood as fuel for the brain
- The brain does not store fuel so blood supply changes as needs arise
- Changes are regionally-specific - following the local dynamics of neuronal activity within that region
- fMRI shows where “functional activity” occurs
- Images brain haemodynamics: Blood Oxygen Level Dependent (BOLD) signal
What is electroencephalography (EEG)?
- Method used to record the electrical activity of the brain
- Often uses a net of electrodes (up to 256) placed on the scalp
- High temporal resolution
- Direct reflection of neuronal activity
- Less expensive than fMRI
- Poor spatial localisation due to recordings made at the scalp
- Better suited to answering questions about “when” cognitive processes work not “where” they work
What are event-related potentials (ERPs)?
- Background EEG signal can be removed by trial-averaging revealing the response of a brain region to stimuli
- Portions of the EEG time-locked to an event are averaged together, extracting the neural signature for the event
What are two electrophysiological techniques?
1) Intracellular recording:
- Inserting electrode into cell to record activity of the cell
- Measuring action potentials
2) Extracellular recording:
- Electrode inserted just outside of cell
What are two stimulation techniques?
1) Electrical
- Electrically stimulate and area of the brain and record response
2) Optogenetic
- Light stimulation, extract optically sensitive pigment and inject it into cell membrane, so they become sensitive to light)
2 methods of studying species common behaviours
1) Open-field test
2) Social defeat
What is an open-field test?
- Box for animals to move around in
- Observing grooming/other species-common behaviours
What is a social defeat test?
- Male rats are territorial
- Unfamiliar individual (intruder) introduced to the habitat of a larger or more aggressive individual (resident)
- Aggressive behaviour of the resident is quantified, or consequences of defeat are explored
- E.g. defeated rats tested with drug addiction (stressed rats that had aggressive encounter are more affected by drug)
Two conditioning paradigms
1) Classical conditioning (Pavlov’s dogs):
- Place preference
- e.g. rat will show which area of a box it prefers, then pair the not preferred side with a drug, and the other with saline. If the animal then spends more time in the not preferred side, this shows a liking for the drug (addiction)
2) Operant conditioning:
- Positive and negative reinforcement
- Chunking - learning to link smaller behaviours together
Example of a semi-natural learning paradigm
Morris water maze:
- Testing spatial memory
- Rats get faster at finding hidden platform in opaque liquid
- Measures escape latency (time taken to escape) and spatial transfer test (removing platform and measuring where the rat spends the most time)
- This behaviour is disrupted by hippocampal lesions
What is a field observation?
- investigates evolution/gene-behaviour relationship
- Animal in natural habitat
- Can’t control extraneous variables
3 examples of things to observe in a field observation
1) Aggression
- Many mammals are polygynous - have a social organisation where one male mates with several females (harem) - competition between males for access to females; leads to intra-sexual aggression (aggression between members of the same sex)
2) Social dominance
- Dominant and submissive individuals = common feature of social organisation of animals
3) Courtship display
- Mating effort - males put effort in to impressing the female
