PSY2061 Study Guide - Final Guide: Magnetic Resonance Imaging, Cerebral Angiography, Neuromuscular Junction
11 Jun 2018
School
Department
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Professor
Nathaniel Parsons
PSY2061 Learning Objectives Week 2 S1 2018
Research Methods
Describe non-invasive methods for stimulating and recording from the living human
brain and discuss the relative strengths and weaknesses of each research method
There are various methods for stimulating and recording the human brain.
An x-ray is electromagnetic radiation waveform we cannot see. X-rays are able to pass
through the body except through dense calcium rich bones. Cerebral angiography is an x-ray
based technique which uses a radio-opaque dye in a cerebral artery to visualise the cerebral
circulatory system.
EEG is a measure of brain electrical activity. It can be performed using 32, 64, 128 or 256
channel electrodes. EEG’s produce high temporal resolution (frequency) but poor spatial
resolution (location). An event related potential can be observed in an EEG as the signal
spreads from the source, through the brain and across the skull to the skin. The result is a
spatially blurred signal which can be recorded by the electrode.
The signal is then amplified, filtered and digitised (measured in uV). ERP’s are extracting
epochs (time periods) of a signal around similar events and averaging. This acts to cancel
out the “random noise” and identify the original signal with more clarity. Through EEG
recording we can observe that the human brain makes a decision 1.5 seconds before action.
EEG’s can detect brain rhythm as certain frequencies dictate neural communication
characteristics. For instance, alpha waves in parietal-occipital lobes are related to
visuospatial attention. Beta waves in the front-central cortex dictate sensorimotor or
response inhibition.
EMG is similar to the EEG, however, electrodes are placed over muscle cells. The EMG
detects action potentials arriving at neuromuscular junctions of muscle fibres beneath the
electrodes. The detected signal for EMG is much higher magnitude (mV) and is used for
reaction time testing. Measures an individual’s response to stimulus through the process
(Warning -> Stimulus -> Initiated Action -> Terminated Action).
Transcranial Stimulation (TMS) is different from the EEG and EMG because it is not just a
measure of electrical activity but can cause the action potentials. TMS involves very brief
and high voltage stimulations through the process of electromagnetic induction. MI motor
maps obtained with TMS are rapidly modulated with learning. Repetitive TMS (rTMS)
involves delivering stimulation at certain frequencies and can alter synaptic efficacy of the
stimulated cortex. There is the potential that rTMS can be used for treatment of Alzheimer’s,
stroke and depression. Furthermore, TMS can disrupt brain activity which allows researchers
to understand the role of the disrupted area.
TMS and EEG can be used in tandem through the following process
(Stimulate brain via TMS -> action potential fires -> record wavelength at neuromuscular
junction through EEG)
Positron emission tomography (PET) scans allow us to produce an image of brain function.
PET scans involve the injection of radioactive ligand (molecule attached to an atom) into a
vein/ the bloodstream. PET scans are useful for identifying the distribution of a particular
brain molecule. For example Pet scans can measure glucose metabolism, aspects of
dopamine neurotransmission, and accumulation of amyloid beta proteins in Alzheimer’s.
find more resources at oneclass.com
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Document Summary
Describe non-invasive methods for stimulating and recording from the living human brain and discuss the relative strengths and weaknesses of each research method. There are various methods for stimulating and recording the human brain. An x-ray is electromagnetic radiation waveform we cannot see. X-rays are able to pass through the body except through dense calcium rich bones. Cerebral angiography is an x-ray based technique which uses a radio-opaque dye in a cerebral artery to visualise the cerebral circulatory system. Eeg is a measure of brain electrical activity. It can be performed using 32, 64, 128 or 256 channel electrodes. Eeg"s produce high temporal resolution (frequency) but poor spatial resolution (location). An event related potential can be observed in an eeg as the signal spreads from the source, through the brain and across the skull to the skin. The result is a spatially blurred signal which can be recorded by the electrode.
