Exam 3 Imaging EEG Other

Question 1

EEG

Answer 1

Electroencephalography

Question 2

What is an EEG?

Answer 2

1. •Recorded summed electrical activity from the brain
2. •Reflects neuronal electrical activity in different brain regions
3. •Recorded from the scalp from 21-75 electrodes

Electroencephalograms (EEGs) are Recorded from the scalp from 21-75 electrodes and Record the summed electrical activity from the brain. EEGs Reflects neuronal electrical activity in different brain regions

Question 3

what does EEG reflect?

Answer 3

•Reflects neuronal electrical activity in different brain regions

Question 4

how many electrodes does an EEG typically record from?

Answer 4

•Recorded from the scalp from 21-75 electrodes

Question 5

what are some common diagnostic uses? (7)

Answer 5

1. –Distinguish epileptic seizures from non-epileptic seizures, syncope & sub-cortical movement disorders
2. –Characterize seizures & determine whether to wean anti-epileptic medications
3. –Differentiate “organic” encephalopathy from psychiatric syndromes
4. –In ICU to monitor brain function, blood flow & monitor therapeutically induced comas
5. –Prognosis in some patients with coma
6. –Determine where in sleep cycle during sleep studies
7. –Serve as an adjunct test of brain death

Question 6

what are some advantages for clinical and research uses of EEGs? (9)

Answer 6

•Advantages for clinical & research uses include:

1. –Inexpensive equipment & analysis
2. –Less sensitive to subject movement
3. –Used in long term studies to follow development
4. –Very high temporal resolution
5. –Assess overall brain state
6. –No exposure to large magnetic fields or ionizing radiation
7. –Does not require motor responses
8. –Useful in biofeedback studies
9. –Easily combined with other techniques

Question 7

What is an event related potential?

Answer 7

A form of EEG that has a number of issues:

1. –Low spatial resolution so cannot identify specific brain locations
2. –Setup time consuming and cumbersome
3. –Interpretation of results can be complex
4. –Lot of artifacts with low signal to noise ratio

Question 8

What are some issues with Event Related Potentials? (4)

Answer 8

1. –Low spatial resolution so cannot identify specific brain locations
2. –Setup time consuming and cumbersome
3. –Interpretation of results can be complex
4. –Lot of artifacts with low signal to noise ratio

Question 9

What are Evoked Potientials?

Answer 9

Evoked EEG Potentials are Electrical activity following presentation of a stimulus, as distinct from spontaneous potentials

• Evoked EEG Potentials have become Widespread in clinical use including:
  
  • Auditory evoked potentials
  • Visual evoked potentials
  • Somatosensory evoked potentials

Question 10

how often are evoked potentials used in the clinic?

Answer 10

widespread

Question 11

what are three evoked potentials that enjoy widespread clinical use?

Answer 11

1. Auditory evoked potentials
2. Visual evoked potentials
3. Somatosensory evoked potentials

Question 12

describe auditory evoked potentials

Answer 12

–Auditory evoked potentials

• EEG Responses to tone or click
• Analysis: trace the signal generated by a sound through the ascending auditory pathway

Auditory evoked potentials are EEG Responses to tones or clicks. Analysis involves Tracing the signal generated by a sound through the ascending auditory pathway

Question 13

describe visual evoked potentials

Answer 13

–Visual evoked potentials

• •Stimulus - checkerboard and grating patterns use light and dark squares and stripes
• •Electrodes over occipital area & Z line proximally
• •Potentials named for direction & magnitude

Visual evoked potentials are EEG activity stimulated by strong visual stimuli such as a checkerboard and grating patterns use light and dark squares and stripes

Electrodes over occipital area & Z line proximally

Potentials named for their direction & magnitude

Question 14

SSEP

Answer 14

–Somatosensory evoked potentials (SSEPs)

Question 15

describe Somatosensory evoked potentials (SSEPs)

Answer 15

–Somatosensory evoked potentials (SSEPs)

• •Electrical stimulation of tibial nerve, median nerve or ulnar nerve
• •The response is then recorded from the patient’s scalp
• •Used to assess spinal cord & brainstem function during surgery
• •Amplitude and latency of the recorded peaks from occipital cortex key to assessing damage
• •Dramatic increases in latency or decreases in amplitude are indicators of neurological dysfunction

Somatosensory evoked potentials (SSEPs) are the result of Electrical stimulation of tibial nerve, median nerve or ulnar nerve. The response is then recorded from the patient’s scalp and is used to assess spinal cord & brainstem function during surgery

Amplitude and latency of the Somatosensory evoked potentials (SSEPs) recorded peaks from occipital cortex are key to assessing damage. Dramatic increases in latency or decreases in amplitude are indicators of neurological dysfunction

Question 16

Somatosensory evoked potentials: what are key to assesing damage?

what indicates neurological dysfunction?

Answer 16

• •Amplitude and latency of the recorded peaks from occipital cortex key to assessing damage
• •Dramatic increases in latency or decreases in amplitude are indicators of neurological dysfunction

Amplitude and latency of the Somatosensory evoked potentials (SSEPs) recorded peaks from occipital cortex are key to assessing damage. Dramatic increases in latency or decreases in amplitude are indicators of neurological dysfunction

Question 17

what is another test that is being combined with EEG?

why would this be done and what kind of equipment is needed?

Answer 17

•Combining fMRIs with EEG recordings

1. –Specially designed equipment to perform both simultaneously
2. –Take advantage of the temporal accuracy of EEG and the spatial accuracy of fMRI
3. –Potentially very powerful technique

As mentioned previously, Combining fMRIs with EEG recordings with Specially designed equipment to perform both simultaneously can Take advantage of the temporal accuracy of EEG and the spatial accuracy of fMRI and is a Potentially very powerful technique for both clinical and research localization o function

Question 18

what is magnetoencephalography?

Answer 18

1. a relatively new approach
2. •Mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain
3. •Done using very sensitive magnetometers
   
   1. •About 50,000 active neurons are needed to generate a signal that is detectable
   2. •Very weak and must be recorded in magnetically shielded room
4. •Algorithms used to determine structure
5. Clinically used to localize certain seizure foci
6. Experimentally used to study cognitive processes in fetuses and newborns

A relatively new approach is Magnetoencephalography which is the Mapping of brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain. This is done using very sensitive magnetometers

About 50,000 active neurons are needed to generate a signal that is detectable but these are Very weak signals and must be recorded in magnetically shielded room

Algorithms used to determine which brain structures are involved . Presently this non-invasive technique is Clinically used to localize certain seizure foci. Experimentally used to study cognitive processes in fetuses and newborns

Question 19

NIRS

Answer 19

Near-Infrared spectroscopy

Question 20

Near-Infrared Spectroscopy (6)

Answer 20

1. •Near-infrared spectroscopy (NIRS) uses silicon-based charge-coupled devices (CCDs) to convert the IR part of the spectrum into electrical signals
2. •Detects changes in hemoglobin concentrations in active neural tissues
3. •Algorithms used to determine structure
4. •Can only detect changes in cortex
5. •Combined with MRI to elucidate structure in relationship to other structures
6. •Research in this area is just developing – particularly in its application to diagnosis of magnitude of head injury

Another recently developed tehnique is Near-infrared spectroscopy (NIRS). It uses silicon-based charge-coupled devices (CCDs) to convert the IR part of the spectrum into electrical signals. It Detects changes in hemoglobin concentrations in active neural tissues and again uses complex Algorithms used to determine structure

Question 21

Magnetoencephalography: how many active neurons are needed to generate a signal that is detectable?

Answer 21

about 50,000 active neurons

Question 22

Magnetoencephalography: does it produce a weak or strong signal?

Answer 22

•Very weak and must be recorded in magnetically shielded room

Question 23

Magnetoencephalography: what is a clinical use?

Answer 23

•Clinically used to localize certain seizure foci

Question 24

Magnetoencephalography: what is an experimental use?

Answer 24

•Experimentally used to study cognitive processes in fetuses and newborns

Question 25

Near-infrared spectroscopy: what does it detect changes in?

Answer 25

•Detects changes in hemoglobin concentrations in active neural tissues

Question 26

Near-infrared spectroscopy: where can it detect changes?

Answer 26

•Can only detect changes in cortex

Question 27

Near-infrared spectroscopy: what other test can it becombined with to elucidate structure in relationship to other structures?

Answer 27

•Combined with MRI to elucidate structure in relationship to other structures

Question 28

Near-infrared spectroscopy: how well is it’s use developed?

Answer 28

•Research in this area is just developing – particularly in its application to diagnosis of magnitude of head injury

Question 29

Answer 29