Measuring brain activity Flashcards
EEG - electroencephalography - limitations and advantages
Strengths
Good temporal resolution meaning the info outputed is accurate to time - discriminate very brief events in time
Cheap for scientific purposes
Portable and possible to record EEG as people move around
Safe and well tolerated by patients as there are no real risks
Very little concerns or fears surround the use of this technology
Limitations
Poor spacial resolution - hard to distinguish where the signal is originated
Usually detect only actvity from the surface of the cortex as it is closets to the electrodes
Electrophysiology - single neurons - strengths and limitations
Strengths
Usful for investigating what individual neurons are doing
Limitation
It being invasive causes it to have a high risk of infection or accidnetly cause damage
Neurons work collectively with other neurons in a large network and therefore network activity is hard to investigate
MRI
Exploits magnetic properties of brain tissue
MRI coil generates a very strong magnetic field, stronger than earths
Magnetic field passes through the head and causes hydrogen atons to align with the magnetic field
Radio frequency waves are temporarily disrupt the alignment and consequently relay back a signal which the machine detects
Different areas of brain tissue emit different signals as they all contain different amounts of water
Analysis software coverts the signals in detail images of different structures in the brain
Strength
Very high spacial resolution
Can identify specific brain structures and functioning
Identify specific anatomical/structural and functional properties of different brain regions
Limitations
Very expensive
Large and requires a special facility where is magnetically shielded
Safety risks
Requires specialist staff with radiography training
fMRI - limitations and strengths
Cognitive processes uses energy from oxygen in hemoglobin
Oxygenated blood doesnt distort surrounding magnetic field whereas deoxygenated blood does
As blood oxygen decreseases, blood veseels become more visisble - this is the basis for the blood oxygen level dependent (BOLD) effect used for fMRI
Map human brain function throught he use of observing oxygen
When the brain uses energy there is an increase of blood flow to the area as oxygen is release in energy expenditure
Blood flow to area one second later - lag time
Positron emissions tomography
Involves the use of tracers which are radioactive substance, to visualise glucose metabolism or a neurotransmitter/receptor function
Can use radioactive tracers to bind selectively to proteins of interest
Strengths
Can detect different chemicals in the brain associated with metabolism or functional properties such as specific neurotransmitter levels or proteins
Limitations
Expensive and requires specialist facilities and staff
Low spacial resolution compared to MRI
Requires radioactive tracers that is injected into the blood - considered safe but it is important that risks are minimised
Enhancement
Refers to the development from healthy function to above/better than normal
Frontal leucotomy
Procedure involving the severance of nerve pathways to and from the frontal lobe
Initially, it created improvements, but overtime side effects were brought about
Consequences revolved around personality such as apathy, emotional unresponsiveness, disinhibition and inability to plan
Two methods for frontal leucotomy
A hole was drilled into the skull and a leucotome was inserted to rotate and remove a core of tissue
Cutting implement was inserted above the eyelid and pushed through the base of the skull and rocked from side to side to slice through the frontal loves and separate it from the rest of the brain
Agonistic drugs
Increases synthesis of neurotransmitter molecules
Increases release of neurotransmitter molecules from terminal buttons
Binds to postsynaptic receptors and either activates them or increasaes the effect of neurotransmitter molecules
Antagonistic drugs
Blocks synthesis of neurotransmitter molecules
Blocks release of neurotransmitter molecules from terminal buttons
Drug binds to postsynaptic receptors and blocks the effect of neurotransmitter molecules
Transcranial magnetic stimulation (TMS)
Coil carrying electrical current outputs a brief focal magnetic pulse which activates a small region of cortex
This activation temporarily disrupts tissue for a few hundred millseconds
Painless
Cause muscle contraction of targeted cortex function
Ablation
Involves surgical removal of specific brain areas
Limited to animal studies for research purposes
Only used for medical treatment in humans
Can cause scar tissue that leads to other problems
Deliberate lesion require a high degree of precision
Brain modulation
technology acting directly on nerves
provide information on the causation and the involvement of a specific brain region for a specific task
