Vagus Stimulation - DM

8/8/2019 Vagus Stimulation - DM

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The Effects Of Vagus Nerve Stimulation

On Decision-Making

Coleman O.M.,. Denburg N.L, Tranel D.,

Granner M.A. & Bechara A.


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The advantage of the emotions is that they lead us astray, and theadvantage of science is that it is not emotional.

Oscar Wilde

The Picture of Dorian Gray, 1891


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Study objective

According to Somatic Markers Hypothesis we are guided by somatic

feelings in decision-making.

Vagus nerve may serve as a main route for somatic afferent signals indecision making process.

In this study the authors wondered whether individual performance

in adaptive decision making task may be improved by the direct

electric stimulation of vagus nerve.


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Vagus Nerve

The longest of the cranial nerves

Starts in the brainstem (within themedulla oblongata) and extends, to

abdomen, where it contributes to theinnervation of the vicera

Besides output to the various organs inthe body the vagus nerve conveyssensory information about the state ofthe body organs to the CNS

~ 80% of the fibers afferent

An extraganglial integrator of theautonomic nervous system


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Evidence in favor of Vagus Nerve

involvement in decision making:

Peripheral neuropathies involving authonomic fibers impair adaptive

decision making at IGT (Bechara et al., 1998). (The vagus is an autonomicnerve)

Left vagus stimulation (VNS) causes increased blood flow in bilateralthalamus, hypothalamus, anterior insula, orbital frontal cortex, inferiorfrontal gyrus, and inferior parietal lobule (Henry et al., 1998)

Vagus nerve stimulation improves human memory (Clark et al., 1999;Cahil & McGaugh, 1998)


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Other possible routes by which

somatic information can feedback

to the brain and influence cognition:

S

pinal cord ?subjects with spinal cord injury between the 2nd and 6th cervical

vertebra did not show impairments in IGT (North and OCarroll,

2001). It is known that Sympathetic signals enter and exit the spinal

cord at and below the first thoracic level,

Endocrine route ?

too slow


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Present study

In this study authors implied the electromagnetic stimulation of the left

vagus nerve to explore further the role of somatic (bodily) feedback in

the adaptive decision making at gambling task.


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S

ubjects Medically refractory epileptic patients with implanted vagus nerve

stimulators

1 female, 7 male

Neuropsychological profile:

Underlined scores represent defective performances


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Decision-making assessment

Adaptive decision-making assessed with Iowa gambling task (Bechara,

Damasio, 1994)

Participants performed the task twice with the disadvantageous decks given

different labels and repositioned to different screen locations on the second

trial.

Between two trials participants underwent neuropsychological testing


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Design

* Mixed * Counterbalanced

* Participants blind as to when stimulation occurred


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3

way (2

2

5) ANOVA #1:Independent Variables:

1. task order (on-first versus off-first) - between group comparison

2. stimulation state (on versus off) - within group comparison

3. The 5 blocks of 20 cards from the 100 trials of the gambling task (awithin group comparison)

Dependent variable:

IGT net score (ratio of good vs bad choices) by block


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3 way (2 2 5) ANOVA #1:

By and large, VNS

participants performed more poorly than healthyparticipants with similar demographic characteristics (previous studies)

Statistically significant interaction of stimulation state (on versus off) and

block [F (4, 24) = 3.92; p < .01].

No significant main effect of order, of stimulation condition, of blocks,

nor any other significant interaction.


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3 way (2 2 5) ANOVA #1:

Interestingly, the participants showed opposite learning patterns in twostimulation conditions:

on condition improved performance during the game, except block 5

off condition performance deteriorated during the game, except block 5


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3

way (2

2

5) ANOVA #2:Independent Variables:

1. task order (on-first versus off-first) - between group comparison

2. stimulation state (on versus off) - within group comparison

3. The 5 blocks of 20 cards from the 100 trials of the gambling task (awithin group comparison)

Dependent variable:

change in IGT net score relative to block 1


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3

way (2

2

5) ANOVA #2:

Significant main effect of stimulation condition [F (1, 6) =9.9; p < .02]

No main effect of order of stimulation, blocks, or any interaction .

Newman-Keulspost hoc testing revealed significant differences inperformance between stimulation states for blocks 2, 3 (p < 0.03)

and 4 (p < 0.001). There was a statistical trend for a difference betweenstimulation states of block 5 (p < 0.1)


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Conclusions:

The results suggest that VNS influences decision-making, thus

supporting the hypothesis that the vagus nerves may be a critically

important peripheral substrate for the process of decision-making

Another line of evidence in favor of the Somatic Marker Hypothesis.

Vagus nerve stimulation is a promising instrument for the neuroscience

research


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Thanks

Authors VNSInventors Health professionals

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