Lesson 3 - Ways of studying the brain Flashcards
What are 2 non-invasive ways of studying the brain?
C(A)T scans
MRI scans
What is a C(A)T scan?
A computer assisted x-ray procedure where the x-ray scanner is rotated 1 degree at a time over 180 degree.
Images are stitched together to form 3d image.
Tomograms reveal structural abnormalities eg lesions caused by trauma or stroke or cortical atrophy
(Rotating x-ray)
What is a tomogram?
A tomogram is the horizontal slices of the 3D images to look more in detail to reveal structural abnormalities in the brain
What is an MRI Scan?
A strong magnetic field (up to 3 tesla) causes hydrogen nuclei (protons) to align in the same orientation.
(magnetic resonance imaging)
when a radio frequency is passed thru head, protons emit electro magnetic energy as they ‘relax’
MRI scanner is tuned to detect radiation emitted as protons relax
in an MRI scanner, different tissues produce different types of what?
signals
eg
grey matter has little water so produces different signals and will move back/push back quickly, white matter has more water so hydrogen magnets will flip back slowly
Without needing to crack open head to look inside of it, what are the two methods to study the brain?
fMRI scans
EEG & ERPS
What is an fMRI scanner?
Oxygen and glucose are supplied by the blood as fuel for the brain
Brain doesn’t store fuel, blood supply changes as needs arise and the changes are regionally specific - following the local dynamics of neuronal activity within that region
What do fMRI scans show?
Where functional activity occurs
What is BOLD and what does it rely on
Blood Oxygen Level Dependent signal is the signal that relies on the difference between the haemoglobin that has oxygen and the haemoglobin that doesnt have oxygen
What does an EEG do? (Electroencephalography)
Records the electrical activity of the brain
Using a net of electrodes placedo n the scalp (up to 256)
What are 2 strengths of using an EEG and one weakness of using an EEG?
High temporal resolution
Less expensive than MRI scanner
Poor spatial resolution due to recordings being made at the scalp - hard to figure out exactly where in brain the activity is coming from
What is an ERP? (Event related potential)
Look immediately afterwards how the brain responds to receiving a signal such as stimuli. Background EEG signal is removed by trial averaging revealing the response of a brain region to stimuli.
Portions of the EEG are time averaged together, extract the neural signature for the event
What are the invasive methods of studying the brain?
Electrophysiological Techniques (Intracellular recording and Extracellular recording)
Stimulation techniques - electrical stimulation and Optogenetics
What do ERP waveforms tell us info about?
The neural basis of processing is provided by the difference in activity
What is Intracellular recording and what is Extracellular recording
A form of Electrophysiological techniques
Intracellular recordings place electrode directly into cell recording individual cells in animal brains
Extracellular recordings record the activity of the brain by having an electrode sit just outside the cell and pick up on the cell firing an action potential
What is electrical stimulation
Using electricity, we can artificially activate the cell or turn on the cells
What is Optogenetics?
Allows us to have some control over the brain activity
Neurons can be turned on or off and become sensitive to light by using the rodoxin / opsin gene to produce either polarisation (produced w light off/blue light) or hyperpolarisation (light on / yellow light)
What is the assessment of species common behaviours?
Open field tests (grooming in chunking sequence behaviours)
rats groom from head to ears to body
Aggression in rats is observed and loser feels a consequence
Species specific stressor
Intruder tends to be defeated and they experience the species specific stressor which
increase of stress w defeat
what is the relation between social defeat and drug addiction?
(social defeat paradigm)
The way you respond to stress becomes how likely youll become addicted to drugs
There is an interaction between stress and the way drugs are metabolised by the body
social defeat ^ stress ^ response to drug^
What are the 2 conditioning paradigms ?
Classical conditioning paradigm and operant conditioning paradigm
What is place preference in addiction?
How classical conditioning can be used to test whether a drug is nice
test it on rats
give animal drug in the side it doesnt like and saline in the one it likes and see how much longer the animal spends in the bit it doesnt like
associates the bit it doesnt like w the drug
How can you use operant conditioning to train rats?
Train rat to learn chunking behaviour (press down left then right bar to get food)
What is a semi natural paradigm?
Halfway point between the lab experiment and an experiment involving the natural outside world
