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EXP NEURO > Neurostimulation > Flashcards

Neurostimulation Flashcards

1
Q

contraction: overview

A
  • myosin can’t bond w actin (due to troponin-tropomyosin complex)
  • Ca binds to complex to expose actin
  • once bonded w actin, myosin heads pull actin filament toward centre of sarcomere
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2
Q

define: neuromuscular junction

A
  • synapse formed btw å motor neuron axon + mm fibre
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3
Q

neuromuscular junction: define motor unit

A
  • axon forming synapses w several mm fibres
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4
Q

neuromuscular junction: how to get precision of mm control?

A
  • based on motor unit size:
  • sml: precise movements of hand (fingers 1:<10)
  • lrg: leg movements (1:>300)
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5
Q

neuromuscular junction: which NT used

A
  • Ach
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6
Q

neuromuscular junction: release of Ach prod?

A
  • prod large endplate potential

- voltage changes opens Ca channels

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7
Q

neuromuscular junction: Ca entry

A
  • triggers myosin-actin interaction (rowing action)

- movement of myosin bridges shortens mm fibre

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8
Q

tension + tetany: aka

A
  • wave summation + tetany AKA freq summation
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9
Q

tension + tetany: list types (4)

A
  • twitch
  • wave summation
  • incomplete tetanus (unfused)
  • complete tetanus (fused)
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10
Q

tension + tetany: how does wave summation occur?

A
  • when set of cells repeatedly stimulated without relaxation
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11
Q

tension + tetany: define tetany

A
  • sustained contraction resulting from high freq stimulation
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12
Q

tension + tetany: eg. external source

A
  • peripheral electrical stimulation
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13
Q

reflex: H reflex

A

stimulus - dorsal root - SC - mm

  • after stimulus + M-wave
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14
Q

name types of brain stimulation (5)

A
  • transcranial magnetic stimulation (TMS)
  • transcranial electrical stimulation (TES)
  • deep brain stimulation (DBS)
  • electroconvulsive therapy (ECT)
  • direct cortical electrical stimulation (DCES)
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15
Q

DBS: involved

A
  • implantation of electrode coils w wires going deep into brain
  • for parkinsons disease
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16
Q

TES: list (4) types

A
  • transcranial direct current stimulation (tDCS)
  • transcranial alternating current stimulation (tACS)
  • transcranial random noise stimulation (tRNS)
  • sham stimulation
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17
Q

tDCS: list (2) types

A
  • anodal

- cathodal

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18
Q

tDCS: features

A
  • Aldini showed direct current stimulation improved mood of melancholy patients
  • Albert found +ve and -ve stimulation had diff effects on cortical excitability
  • recent interest in tDCS is renewed
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19
Q

tDCS: mechanism

A
  • small electric current (~1 mAmp) passed through brain
  • electrodes on scalp
  • 9 volt current source
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20
Q

tDCS: which electrode is +vely/-vely charged?

A

+ve: anodal

-ve: cathodal

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21
Q

tDCS: way current flows from electrodes?

A
  • from anode through skull + brain to cathode
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22
Q

tDCS: device features

A
  • delivers current

- controls w set current intensity and duration of stimulation

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23
Q

tDCS: general features (3)

A
  • noninvasive brain stimulation
  • electrical currents delivered to scalp
  • equivalent to voltages naturally prod by brain (1-2mA)
24
Q

tDCS: anode electrode (4)

A
  • +vely charged current
  • stimulates nearby cortical regions
  • increases +ve charge
  • neurons more likely to reach AP
25
Q

tDCS: cathode electrode (4)

A
  • attracts -vely charged current
  • inhibits nearby cortical regions
  • increases -ve charge
  • neurons less likely reach AP
26
Q

tDCS: critical issues (3)

A
  • tDCS is bipolar
  • pure anodal/cathodal stimulation impossible
  • NOT focal, no way to know where stimulation is occurring (be skeptical of current models)
27
Q

tDCS: diy and foc.us gaming devices

A
  • can diy ur own
  • gaming devices to ‘enhance cognitive function’
  • 2% cost of research/clinical grade sys
28
Q

tDCS: experimental- 3 ver

A
  • anodal
  • cathodal
  • sham
29
Q

tDCS: experimental- sham?

A
  • used as control in experiments
  • emits brief current, remains off for remainder of time
  • patient doesn’t know they aren’t receiving prolonged stimulation
30
Q

tDCS: pros (6)

A
  • cortical changes even after stimulation is ended (depends on length/intensity of stimulation)
  • cheap
  • portable
  • relatively easy to use
  • safe*
  • bidirectional
31
Q

tDCS: cons (3)

A
  • poorly localised
  • no temporal resolution
  • can’t elicit AP
32
Q

tDCS: experimental- Walsh

A
  • ‘bullshit’ no evidence of cognitive effects after single session
  • doubts of use
33
Q

TMS: shape of wand

A
  • using regular circle has large SA

- but 2 coils concentrate to smaller SA

34
Q

TMS: pros- chronometry (2)

A
  • timing the cont of focal brain activity to behaviour

- role of ‘visual’ cortex in tactile information processing in early blind subjects

35
Q

TMS: virtual lesions- causal link btw

A
  • brain activity and behaviour
36
Q

TMS: real lesion eg.

A
  • blind woman lost ability to read braille following bilateral occipital lesions
37
Q

TMS: TMS lesion

A
  • using sighted (blue) and E blind (red)
38
Q

TMS: occipital TMS on braille reading result

A
  • disrupts braille reading in early blind

- not control subjects

39
Q

TMS: critical issues (3)

A
  • online vs. offline design?
  • online: how are sitmuli ordered?
  • offline: how long experiment, r conditions dist evenly within lesion window?
40
Q

coil localisation: find functional effect

A
  • M1 (hand twitch- MEP)

- V5 (moving phosphenes)

41
Q

coil localisation: find anatomical landmark

A
  • inion/nasion - ear/ear vertex

- EEG 10/20 sys

42
Q

coil localisation: move set dist along + across eg.

A

FEF = 2-4cm ant, 2-4cm lateral to hand area

43
Q

coil localisation: but?

A
  • not all brains are same
  • MRI co-registration
  • functional and structural scan
  • frameless stereotactic sys
44
Q

coil localisation: control conditions (5)

A
  • diff hemisphere
  • diff site (these have diff effect/ no effect)
  • real
  • sham (improper technique, extra padding)

or interleave TMS w no TMS trials

45
Q

coil localisation: critical issues control conditions (5)

A
  • control nonspecific stimulation effects
  • control placebo/behavioural arousal etc.
  • control sound
  • control for extra physiological effects (eg. twitching)
  • control for task specificity
46
Q

coil localisation: major pros summary (6)

A
  • reversible lesions without plasticity changes
  • repeatable
  • high spatial/temporal resolution
  • can establish causal link btw brain activation and behaviour
  • can measure/modulate cortical plasticity
  • therapeutic benefits
47
Q

coil localisation: major limitations summary (6)

A
  • only regions on cortical surfaces can be stimulated
  • can be unpleasant for subjects
  • risks to subjects + esp patients
  • stringent ethics required (can’t be used by some institutions)
  • localisation uncertainty
  • stimulation lvl uncertainty
48
Q

safety: seizure induction-

A
  • caused by spread of excitation
  • single-pulse TMS has prod seizures in patients, not normal subjects
  • rTMS: both
  • visual and/or EMG monitoring for after discharges + spreading excitation may reduce risk
49
Q

safety: hearing loss

A
  • TMS loud click (90-130dB) in most sensitive range (2-7kHz)
  • rTMS= more sustained noise
  • reduced alot by ear plugs
50
Q

safety: heating of brain

A
  • theoretical power dissaption from TMS is few mW at 1Hz,

- brain metabolic power is 13W

51
Q

safety: engineering safety

A
  • TMS equipment operates at lethal voltages of up to 4kV

- max energy in capacitor is 500J = dropping 100kg from 50cm on your feet

52
Q

safety: scalp burns form EEG electrodes

A
  • mild scalp burns in subjects w scalp electrodes

- easily avoided eg. sml low-conductivity Ag/AgCl-pellet electrodes

53
Q

safety: effect on cognition

A
  • slight trend toward better verbal memory, improved delayed recall and better motor reaction time
54
Q

safety: local neck pain and headaches

A
  • related to stimulation of local mm and nn, site and intensity dependant
  • particularly uncomfy over fronto-temporal regions
55
Q

safety: effect on mood in normals

A
  • subtle changes in mood are site, freq dependant
  • high freq rTMS of L frontal cortex worsens mood
  • high freq rTMS of R frontal cortex may improve mood
56
Q

safety: contraindications

A
  • metallic hardware near coil (pacemakers, medical pumps etc.)
  • history seizures, history epilepsy in 1st degree relative
  • medicines reducing seizure threshold
  • pregnant
  • history of serious head trauma
  • history of substance abuse
  • stroke
  • status after brain surgery
  • other medical/neurologic conditions assoc epilepsy/seizure will be hazardous
57
Q

safety: critical issues (6)

A
  • purpose of stimulation?
  • type of stimulation?
  • where is stimulation?
  • stimulation adequate?
  • control conditions?
  • safety?

EXP NEURO (10 decks)

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