Biopsychology : Ways of studying the Brain Flashcards
What is spatial resolution?
Spatial resolution – refers to the smallest feature (or measurement) that a scanner can detect. Greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy.
What is temporal resolution?
Temporal resolution – refers to the accuracy of the scanner in relation of time or how quickly the scanner can detect changes in brain activity
Whats a BOLD response?
Blood oxygen level dependent response
fMRI - how does it work?
fMRI measures changes in blood oxygenation in the brain when a person performs a task - measures BOLD reaction. It works on assumption that an active brain area consumes more oxygen. Energy requires glucose and oxygen, which is carried in the blood by haemoglobin and is released by neurons. Neuronal activity and blood supplying oxygen relationship – neurovascular coupling.
fMRI - What resolution does it have?
High spatial resolution – you can clearly distinguish distinct areas of the brain.
Low temporal resolution – you can measure the whole brain in about 0.8 seconds, missing a lot of information
fMRI - what’re the strengths?
- High spatial resolution
- Non-invasive
fMRI - what’re the limitations?
- Low temporal resolution (5 sec time lag between image and neuron firing)
- Expensive (3 tesla magnate – stronger than the Earths gravitational pull, and about £2000 per subject)
- Unable to have a large sample size, therefore less generalisable
- Indirect measure → you’re not actually studying brain activity, your studying blood flow (difficult to establish causation)
- Movement artifacts → moving your head very slightly can affect results
- Accessibility → people with metal in their body (pacemaker, tattoos, metal plates, and pregnancy, etc) can’t use it
EEG - how does it work?
Electro-encephalo-gram - Measures the electrical activity in the brain with electrodes that are fixed onto the scalp (usually using a skull cap). It works on the assumption that info is processed in the brain as electrical activity in the form of action potential.
- Small electrical charges are detected by the electrodes and graphed over a period of time indicating the level of activity
- There are 4 types of waves: alpha, beta, theta, delta
- They’re measures in amplitude (vertical) and frequency (horizontal)
- EEGs are often used by clinicians as a diagnostic tool bc unusual arrhythmic patterns of activity may indicate neurological abnormalities (epilepsy, tumours, sleep disorders, etc)
EEG - what’s its resolution?
Low spatial resolution – you can only roughly see where the activation is and you can only see what is happening on the surface of the brain
High temporal resolution- in the milliseconds (50-60 ms)
EEG - what’re the strengths?
- High temporal resolution
- Non-invasive
- Low cost (about a £100 a patient)
- Portable (take it to a bedside – Adrian Owen’s ‘Locked-In patients’ study), allowing for increased accessibility for highly disabled, critical injury, comas, etc
- Wide range of populations (can use it with anyone – part from people with extremely thick hair, like dreadlocks, even if you have metal in your body)
- Direct neural measure
- Contributed to understanding sleep and diagnosis of epilepsy
EEG - what’re the limitations?
- Low spatial resolution
- Susceptible to artifacts → if you blink, it alters the results dramatically
- Limited to surface activity in the cerebral cortex (even though below the surface is also participating in the signal)
- Difficult interpretation → because you can’t properly localise activity
- Requires skilled technicians
ERP - how does it work?
Evoked response potential/ event-related potential – basic and general form of looking at brain activity by cognitive neuroscientists isolating specific neural responses associated with sensory, cognitive and motor events. They work by using a statistical averaging techniques that filters out extraneous brain activity from the original EEG recording technique, leaving only the responses that relate (brainwaves triggered by a specific event)
ERP - what’s its resolution?
Low spatial resolution – you can only roughly see where the activation is and you can only see what is happening on the surface of the brain
High temporal resolution- in the milliseconds (50-60 ms)
ERP - what’re the strengths?
- High temporal resolution, better spatial than EEGs
- Non-invasive
- Low cost (about a £100 a patient)
- Sensitive to cognition
ERP - what’re the limitations?
- Low spatial resolution (vs fMRI, PET)
- Low signal-to-noise ratio → requires repeats and averages
- Limited to surface activity in the cerebral cortex (even though below the surface is also participating in the signal)
