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KIN 311 > TMS > Flashcards

TMS Flashcards

1
Q

What does TMS stand for?

A

Transcranial Magnetic Stimulation

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2
Q

What does TMS result in?

A
  • Indirect trans-synaptic activation of corticospinal neurons
  • Direct Activation of corticospinal neurons
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3
Q

How is TMS measured?

A
  • TMS sends electrical signal through loops to excitable tissue (brain)
  • Short but strong electrical signal sent, creating magnetic field which induces ionic currents to excite tissue underneath
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4
Q

When is TMS administered?

A
  • Various time periods of preparing movement
  • different neural excitabilities
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5
Q

What does the TMS induce?

A
  • MEP (motor evoked potential)
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6
Q

What does MEP stand for?

A
  • Motor evoked potential
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7
Q

What is the TMS evoked MEP’s amplitude used to measure?

A
  • neural excitability
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8
Q

Describe and Define the motor evoked potential and motor silent period

A
  • MEP: result of activating corticospinal neurons in the primary motor cortex
  • Silent period: Refractory period + activation of inhibitory interneurons of motor cortex
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9
Q

Describe the H-Reflex

A
  • Same curcuit as stretch relfex
  • Electrical stimulate nerve bundle
  • ## High intensity: activate motor neurons in muscle directly creating M-wave (before H-wave)
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10
Q

Describe the basic “monosynaptic” reflex circuit

A
  • electric signal at nerve bundle
  • Recruit large sensory afferent
  • Sensory afferent synapse recruit motor neuron in spinal cord
  • Generates muscle response (H-wave)
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11
Q

Distinguish between mechanisms for stretch reflex and H-reflex

A
  • Stretch reflex when you physically stretch the nerve bundle and the muscle reacts
  • H-reflex is when the nerve bundle is electrically stimulated and generates muscle activation
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12
Q

Explain the concept of reflex excitability

A
  • The H-wave amplitude directly reflects the reflex excitability
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13
Q

Describe the time course of corticospinal excitability as measured with TMS prior to and after movement initiation

A
  • Premovement - increased corticospinal excitability
  • Postmovement - increase in corticospinal excitability
  • Postmovmenet - Decrease in corticospinal excitability
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14
Q

Explain the premovment -increase corticospinal excitability measured with TMS

A
  • Occurred 80ms before emg onset
  • Higher activation as it gets to response
  • Reaction Time with subthreshold
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15
Q

Describe teh Postmovement increase in corticospinal excitability seen with TMS measurement

A
  • 0-100ms after the emg burst
  • M1 excitability still remained baseline, but decreasing
  • 100-160ms, second increase in excitability, may be related to subthrshold, second agonist burst
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16
Q

Describe teh Postmovement decrease in corticospinal excitability that is measured with TMS

A
  • Corticospinal excitability is reduced from 550-1000ms after EMG offset
17
Q

Describe and explain the “dual nature” of corticospinal activation during the temporal preparation for an upcoming action

A
  • Both inhibitory and excitatory are activated during corticospinal action of the temporal preparation stage
  • Exticitatory for the movement preparing processes
  • Inhibitory to forbid body from initiating the motor program
18
Q

Explain teh mechanism for concurrent neural activation and suppresion

A
  • Shown by reduction in MEP amplitude (inhibition)
  • Shown by shortening silent period (activation)
19
Q

Describe and discuss the modulation of corticospinal excitability during the inhibition of a prepared action

A
  • MEP of corticospinal activity will gradually increase exponentially until the “go” signal cannot be withhled at around 150ms prior to target
20
Q

Describe how the H-reflex can be used as a probe for motor preparation

A

H-reflex can be stimulated during different times of motor preparation in a reaction time task
- Foreperiod interval
- Reaction time interval (prior to movment onset - 25-75ms)

21
Q

Describe and explain the modulation of spinal excitability during foreperiod and reaction time intervals

A

During Short, Constant Foreperiod Intervals
- Depression of H-reflex magnitude (supressed response)
- To “tune” motor-neuron pool for upcoming interval
During reaction time intervals
- Facilitation of H-reflex magnitude (facilitated response)

KIN 311 (3 decks)

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