NATS 1860 Study Guide - Final Guide: Transcranial Magnetic Stimulation, Near-Infrared Spectroscopy, Radioactive Tracer

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Published on 14 Apr 2013
School
York University
Department
Natural Science
Course
NATS 1860
NATS EXAM
2. Briefly explain each of the following imaging techniques, including which signals are being
measured from the brain, and describe one strength and one weakness
Functional MRI:
Detects small signal due to blood flow
Infer dynamic neuronal activity changes
Strength
Good combination of temporal and spatial resolution
Weakness
Indirect inference of neuronal activity through secondary measure (blood flow)
PET: Position emission tomography
Detects gamma rays emitted by a radioactive tracer isotope that is attached to
molecules (e.g. glucose in blood)
Can measure neuronal activity by proxy though blood flow
Strength
Can trace different substances
Weakness
Worse spatial and temporal resolution than fMRI
EEG: Electroencephalography
The activity of neurons in your brain involves electrochemical activity
A very small but detectable eclectic field can be measured on the surface of the scalp
using sensitive electrodes and amplifiers
Strength
Good temporal resolution
Weakness
Long and uncomfortable subject setup
MEG: Magnetoencephalography
Similar to EEG, but involves magnetic fields instead of electric field
Strength
Improved setup time and subject comfort compared to EEG
Weakness
Confined to signals at surface of brain
TMS: Transcranial magnetic stimulation
Very strong but brief magnetic pulse is applied near surface of head
Induces electrical current flow on surface of brain
Strength
Allows manipulation of neuronal activity and thus causal inference
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Weakness
Limited to surface of brain
NIRS: Near infrared spectroscopy
Shine infrared light through skull
Detects changes in absorption due to blood flow
Strength
Non-invasive, very safe, good for infants
Weakness
Does not work in every subject
Optical Imaging:
Directly view the surface of the cortex using a video camera
Electrical activity can also be measured by using a voltage-sensitive dye
Strength
Allows measurement and comparison of both intrinsic and electrical activity
Weakness
Confined to the surface of the brain
Electrophysiology:
Directly record action potentials and other electrical activity in neurons by placing
electrodes in the brain
Strength
Activity of multiple individual neurons can be directly compared
Weakness
Records from small number of neurons
3. Compare and contrast the human brain and a digital computer, including memory capacity,
processing, speed, and the capabilities of understanding and being intelligent or conscious.
Describe one ability that a computer excels at but a human brain doesn’t and vise versa
Digital computers are good at implementing simple rules quickly and exact. They can
out perform brains in many simple tasks
- Symbolic manipulations (algebra), repetitive calculations, chess
Brains are good at making judgments, inferences, and generalizations. They are prone
to error, but they can solve many problems that are presently untenable with machines
- Face recognition, speech recognition, language
Brains and machines can both solve the same tasks as the other, only they are much
slower at tasks which they are not specialized at
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Document Summary

Nats exam: briefly explain each of the following imaging techniques, including which signals are being measured from the brain, and describe one strength and one weakness. Detects small signal due to blood flow. Good combination of temporal and spatial resolution. Indirect inference of neuronal activity through secondary measure (blood flow) Detects gamma rays emitted by a radioactive tracer isotope that is attached to molecules (e. g. glucose in blood) Can measure neuronal activity by proxy though blood flow. Worse spatial and temporal resolution than fmri. The activity of neurons in your brain involves electrochemical activity. A very small but detectable eclectic field can be measured on the surface of the scalp using sensitive electrodes and amplifiers. Similar to eeg, but involves magnetic fields instead of electric field. Improved setup time and subject comfort compared to eeg. Confined to signals at surface of brain. Very strong but brief magnetic pulse is applied near surface of head.

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