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Psych 377 > Brain Imaging > Flashcards

Brain Imaging Flashcards

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1
Q

what type of recording is best for action potentials?

A

single cell

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2
Q

how are graded potentials recorded?

A

EEG, ERP, MEG

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3
Q

how does single cell recording work?

A

Electrodes inserted into or adjacent to an individual neuron
Activity of the neuron is then related to the behaviors of the organism

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4
Q

which part of the nervous system is single cell recording most often done in and why?

A

This is more common in the peripheral nervous system because opportunities to implant electrodes in the human CNS are limited

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5
Q

the firing patterns of neurons vary, depending on…

A

what information they encode

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6
Q

what is true of most neurons?

A

Most neurons are tuned to a particular stimulus and have a low level of baseline activity

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7
Q

what aspect of an activity seems important in neuronal firing patterns?

A

Context of the activity seems important in neuronal firing patterns

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8
Q

in layman’s terms, how does the basic idea of levels of processing work, and give an example

A

lower levels of processing include many neurons tuned to very specific parts of the stimuli, and higher levels of processing include fewer cells that do more work. For example, in the retina, many many light-receptor cells (rods and cones) project to a few retinal ganglion cells, that then project to fewer LGB (lateral geniculate body) cells, that project to somewhat more visual cortex cells, and those cells project to larger numbers of assicoation cells. higher cells respond to more complex stimuli. ends up looking like ><

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9
Q

what takes place in an EEG?

A

electrodes are placed on scalp, and the output from the electrodes are recorded in a polygraph, summarizing the activity of the population of neurons in the area of the brain underneath each electrode

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10
Q

true or false: recordings from the skull and brain are similar, validating the noninvasive recording

A

true

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11
Q

when using EEGs, how can the origin of the signal be determined?

A

Origin of the signal can be estimated by comparing the recordings from different locations on the skull

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12
Q

what do beta brain waves tell us about the brain state at that time?

A

Beta: high-frequency, low-amplitude waves associated with being alert

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13
Q

what are alpha brain waves and what are they associated with?

A

Alpha: lower-frequency, high-amplitude waves associated with relaxation

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14
Q

what are delta brain waves and what are they associated with?

A

Delta: less-frequent, higher-amplitude waves associated with sleep

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15
Q

what happens to brain waves when in coma?

A

waves become even lower frequency

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16
Q

what can EEGs be used to assess?

A

states of consciousness and depth of anesthesia

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17
Q

how can EEG be used diagnostically?

A

EEG can be used diagnostically to identify abnormal brain signals

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18
Q

what can we tell about epilepsy using EEG?

A

EEG can be used to localize the starting point for the seizures and monitor the spread

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19
Q

what is meant by ‘partial seizure’?

A

In partial seizures, the coordinated activity of many neurons firing is limited to a few regions of the brain

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20
Q

what is meant by ‘generalized seizures”?

A

In generalized seizures, the activity is spread over the entire brain

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21
Q

in talking about EEG and cognitive function, what is coherence theory?

A

Coherence theory suggests that there is a relation between the EEG activity and behavior

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22
Q

in coherence theory, what is high coherence characteristic of?

A

High coherence
Low-frequency, high-amplitude waves
Associated with coordinated activity of neurons, but low cognitive load (like delta waves when sleepy)

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23
Q

in coherence theory, what is low coherence characteristic of?

A

Low coherence
High-frequency, low-amplitude waves
Associated with many neurons firing at different times, actively processing information
(like beta waves)

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24
Q

what are ERPs?

A

Event-related potentials, brief changes in the EEG signal in response to a sensory stimulus or behaviour

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25
Q

what do ERPs respond to?

A

Correspond to the excitatory and inhibitory postsynaptic potentials in sensory neurons

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26
Q

how do you get an ERP?

A

Repeatedly present the stimulus to the subject while recording EEG
Stimulus presentation sets the time = 0; record changes from that time
Average over repeated presentations to eliminate unrelated activity
Resulting graph shows both negative and positive waves

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27
Q

different stimuli may have ____ initial components, but tend to be __ unique at longer times from the initial stimulus

A

similar, more

28
Q

what can we do with the ERPs recorded from different locations?

A

map the progress of information through the cortex

29
Q

in ERP readings, what do deflections upwards represent?

A

inhibitory

30
Q

in ERP readings, what do deflections downwards represent?

A

excitatory

31
Q

how do MEG work?

A

Electrical charges moving along a neuron generate a magnetic field
These fields are very weak but can be detected and mapped using SQUIDS (superconducting quantum interference devices)

32
Q

what can MEG be used for?

A

Maps can be used to estimate the locations of the neurons that are generating the electrical fields

33
Q

what happens in DBS?

A

Implant electrodes into the brain region of interest
Stimulate the region at different frequencies to treat clinical conditions

34
Q

what clinical conditions can DBS be useful in treating?

A

Depression
Obsessive-compulsive disorder
Epilepsy
Parkinson disease

35
Q

how does TMS work?

A

In the same way that a moving electrical charge can induce a magnetic field, a magnetic field can cause the movement of electrical charges
TMS applies a strong magnetic field at the surface of the skull to change the electrical activity of the adjacent neurons

36
Q

what can TMS be used for?

A

TMS can be used to stimulate or inactivate the neurons, allowing researchers to infer the function of the area from behavioral changes
TMS can be used clinically to treat pain, movement disorders, and depression

37
Q

what type of imaging technique is X ray?

A

static

38
Q

what was the downside of traditional x-rays?

A

Traditional X-rays provided an image of the brain, but just an image of the structure that did not show activity and mostly showed the bone

39
Q

what technique replaces some of the CSF in the spinal cord with air?

A

pneumoencephalography

40
Q

how does pneumoencephalography work?

A

replaces some of the cerebrospinal fluid in the spinal cord with air and collects images as the air moves to the ventricles, increasing contrast

41
Q

what is angiography and how does it work?

A

Angiography injects a tracer into the blood supply that will absorb X-rays and result in a high-resolution image of the circulatory system

42
Q

how does Computed Tomography work? (CT)

A

Narrow beams of X-rays are recorded passing through the brain at different angles
Computer software reconstructs the three-dimensional brain

43
Q

what is the resolution of CT scans?

A

about a 1 mm cube, called a voxel

44
Q

what does dynamic brain imaging reveal?

A

the task-related activity

45
Q

most forms of dynamic brain imaging produce what?

A

indirect measures of brain activity, looking at the blood flow changes and blood oxygenation level changes that correlate with neural activity

46
Q

how does Positron Emission Tomography work?

A

A radioactive tracer is injected into the circulatory system to be carried to the brain
Tracer accumulates more in areas that are metabolically active, such as neurons using action potentials to communicate
When the radioactive tracer decays, it gives off energy in the form of positrons
Positrons are antimatter and when they interact with matter, they are destroyed, giving off energy that is detected and localized by the detectors arranged around the head

47
Q

what is the purpose of subtraction in brain imaging?

A

to pare through the noise, Subtraction of the activity related to the control condition from the activity related to the experimental condition should leave only the brain activity that is related to the task

48
Q

what is the formula for subtraction in brain imaging?

A

activity related to experimental condition - activity related to control condition

49
Q

how does one use subtraction to find the areas common across subjects of a test?

A

average task-related activity

50
Q

what is the procedure of subtraction in brain imaging?

A

stimulation - neural = difference…….individual differences all added up gives you the MEAN difference image

51
Q

How do MRI work?

A

-each proton in hydrogen is a small magnet
-the patient is put into a strong magnetic field, which causes all the protons in the body to align with this external magnetic field
-radiofrquency energy is used to force the protons to orient to a 90 degree angle with the magnetic field, and as theyre reorienting they give off energy

52
Q

in MRI, what does T1 measure?

A

T1 measures how long it takes for the protons to reorient to the strong magnetic field

53
Q

in MRI, what does T2 measure?

A

T2 measures how long it takes for proteins to become desynchronized around the horizontal axis after the radiofrequency pulse is turned off

54
Q

what is the benefit of using T1 and T2 in MRI?

A

T1 and T2 constants vary in different tissues, and this can be used to map the different types of tissue in the brain

55
Q

what can DTI map?

A

the movement of water molecules

56
Q

what does DTI stand for?

A

Diffusion tensor imaging

57
Q

how does DTI work?

A

-highlights the axonal connections between different parts of the brain, as the direction of movement is always constrained along the length of the axon

58
Q

what do rs-FMRI measure?

A

rs-fMRI looks at activity of the brain when it is not engaged in any particular task

59
Q

How are rs-FMRI interpreted?

A

Different brain regions show correlated levels of activity
Some parts of the brain that are connected structurally show highly correlated activity, but other areas that are connected do not show correlated activity

60
Q

what are motifs (in terms of rs-FMRI)

A

patterns of activity spreading from one cortical area to another

61
Q

what can motifs tell us?

A

can characterize cognitive processes, like learning, or disease states like depression or Alzheimers

62
Q

how does optical tomography work?

A

Functional near-infrared spectroscopy (fNIRS) shines near-infrared light through the skull and detects the light reflected from the blood
Oxygenated and deoxygenated hemoglobin absorb light differently, so the reflected light provides a measure of blood oxygenation
Computer reconstructs the image of the brain activity and how that changes as the task changes

63
Q

what do brain imaging techniques differ in?

A

expense, spatial resolution, temporal resolution, invasiveness

64
Q

what are the pros and cons of PET?

A

pro: can identify and localize a wide range of chemicals and metabolic processes
con: only provides indirect measure of neuronal activity and relies on subtraction method

65
Q

what are pros and cons of fMRI?

A

pro: can provide detailed structural and functional info about the brain, and refinements to the technique like DTI and rs-FMRI allow researchers to ask new and more elaborate questions
con: fMRI is a confined space, provides indirect measure of neuronal activity

66
Q

pros and cons of fNIRS

A

Pro: inexpensive, portable
con: can only record near surface of brain and resolution not as detailed

Psych 377 (11 decks)

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