cognitive neuropsychology presentation on tms

2. 15. 2012 | A Cognitive Neuropsychology Presentation

DomingoSeeYuQuijanoTan

Unsettling the Brain The Functions & Applications of Transcranial Magnetic Stimulation (TMS){

Thursday, February 16, 12

First, a demonstration!

Transcranial Magnetic Stimulation

1. Coil is placed near the head of the patient

2. Electrical current flows in opposite directions and come together at the center-point

3. Magnetic field penetrates the brain & induces an electric field in the underlying region of the cerebral cortex

4. Stimulates excitation & organization of neuronal firing in stimulated region.

The Procedure

• First introduced by Anthony Barker & his colleagues in 1985

• Based on the principle of electromagnetic induction

• The production of an electric current across a conductor moving through a magnetic field

• a method that disrupts normal brain processes

• helps “simulate” brain damage in normal people

What is Transcranial Magnetic Stimulation?

• the primary materials used: magnets and coils

• magnetic fields can induce electrical activity in specific regions of the brain and affect its respective functions

• TMS directly affects brain functioning, unlike fMRI, which merely observes brain activity

What is Transcranial Magnetic Stimulation?

How does it work?

Michael Faradayan English chemist and physicist who discovered electromagnetic induction

His illustration1. When an electrical current is passed through a wire, it generates a time-varying magnetic field.

2. If a second wire is placed nearby, the magnetic field induces electrical current flow in that second wire.

In TMS:the ‘first wire’ is the stimulating coilthe ‘second wire’ is a targeted region of the brain.

Motor conduction in human developmentMotor controlMovement disordersVisionAttentionMemorySpeech & languageEpilepsyDepressionStrokePain & plasticitySwallowing

Transcranial Magnetic Stimulation can stimulate peripheral nerves & brain tissues in in studies encompassing

How does it work?

Instrument: Figure-of-Eight Shaped Coil

Although the stimulation is maximal on the cortical region (cortex), the stimulation also has an (secondary) effect on connected areas of the cortex.

E.g. When the left motor cortex is stimulated, there are 3 likely effects of stimulation:

a. change in activity in the targeted region

b.change in activity in immediately surrounding areas of cortex

c. change in activity of cortical areas directly connected with the stimulated region

It is important to consider to keep an open-mind with the effects of the stimulations.

Secondary Effects

Stimulating the left hemisphere with TMS

1. A cap with the magnetic coil connected to a current is placed on the head.

2. Tiny magnetic pulses disturb circuits on left side of brain that usually sees the bigger picture, and suppresses the detail-hoarding right side.

3. Details unconsciously come to the core, creating a burst of mathematical or other talent

TMS to left hemisphere to disrupt language (uploaded Jan 23, 2012)Thursday, February 16, 12

A TMS Study on Savant Autism

Savant-like skills exposed in normal people by suppressing the left-fronto-temporal lobe

(Synder et al., 2003)

The Study of Autistic Savants

Savant [sa-vahnt](n.) a learned persona person of profound or extensive learning

To help explain what a savant is:

Dustin Hoffman in Rain Man

- portrayed an autistic named Raymond Babbitt

- has astounding memory for - baseball statistics

- the phone book- has great ability to “count

cards” (a strategy in blackjack)

Research Goals

• To test whether savant-like skills can be found in healthy people

• “If neurological impairment is the cause of the autistic's disabilities, could it be the cause of their genius-like abilities, too?

• Through the use of the TMS device, neuroscientists can identify the role of the left fronto-temporal lobe in the savant syndrome and explain how inihibiting it can create almost savant-like skills.

Method

• Repetitive Transcranial Magnetic Stimulation (rTMS) was delivered for 15 min. over the left fronto-temporal lobe of 11 healthy participants

• Participants were required to complete drawing & proofreading tasks

• Participant performance on each of the tasks was evaluated:

• Before the real and placebo magnetic stimulation

• During the real and placebo magnetic stimulation

• Immediately after real and placebo magnetic stimulation

• 45 min. after 15 min of real and placebo magnetic stimulation

Results: Drawing Task

• After 10 minutes of stimulation, N.R. and A.J. radically changed their schema for dogs from their initial 2 drawings before stimulation. During and after stimulation, the style dramatically changed, with the drawings becoming more complex.

• The horses of D.C. became more life-like, even flamboyant, compared to the drawing he completed before stimulation.

Results: Drawing Task 1

Before TMS After 10 min of TMS

After 15 min of TMS

45 min after TMS ceased

Participant D.C.

• During and after real stimulation, R.Y. changed his convention for drawing faces.

• In the placebo stimulation a distinct schema is present in the drawings of R.Y.

• During and after real stimulation, this style changed and R.Y. became preoccupied by the details of eyes.

• These drawings were executed in one minute by R.Y. after viewing the corresponding image of figure 4 for 30 seconds.

Participant R.Y.

Before TMS After 10 min of TMS

After 15 min of TMS

45 min after TMS ceased

Implications of Results: Drawing Task

•Magnetic stimulation caused a major change in the schema or convention of the drawings

Proofreading Task

a bird in thethe hand is worth two in the bush

Sample

Without s)mula)on, par)cipants almost always missed the duplicated ‘the’ in the sentence.

Proofreading Task

• Proverbs

• A series of 10 proverbs was presented on a screen.

• Each proverb was presented on the screen for 2s, during which time the participant read the proverb aloud.

• 2 proverbs in the set contained an error where a word was duplicated

• Paragraph

• A paragraph appeared on the screen, which the participant read aloud. It also contained 2 duplicate word errors and a few errors in spelling and grammar.

• Participants were instructed to read the whole text including the errors

Results: Proofreading Task

• D.C. and R.Y. displayed a noticeable improvement in ability to recognize duplicate words.

• They did comparatively well during and/or immediately after stimulation and comparatively poorly both before and 45 min after.

• These were the same participants who displayed pronounced style changes in their drawings.

• No improved proofreading or drawing abilities were associated with placebo stimulation.

• This suggests any improvements seen with placebo stimulation were merely a consequence of learning.

Results

Change in drawing style

Enhanced proofreading

ability

Altered psychological

experience

D.C D.C D.C

R.Y. R.Y. R.Y.

A.J. *

N.R. N.R.

* did not give a subjective report

Implications of Results: Proofreading Task

• Unlike autistic savants, our propensity to impose meaning and concept blocks our awareness for details making up the concept

• There is non-subjective evidence of the ability to switch on a savant-like skill by turning off part of the brain in healthy individuals.

• Without stimulation, participants almost always missed errors such as the repeated 'the' even after many exposures. This fact is illustrated by the poor performance of all participants who received placebo stimulation.

Study 2

Savant-like Numerosity Skills Revealed In Normal People By Magnetic Pulse (Snyder et al., 2006)

Goals ❖ Method ❖ Results

• Research goal

• To test whether normal individuals are capable of savant numerosity (the ability to instantly answer the exact number of objects)

• Method

• Researchers temporarily stimulated the savant condition in 12 healthy participants by inhibiting the left anterior temporal lobe of with rTMS and making them guess the exact number of discreet elements presented to them

• Results

• 10 participants improved their ability to accurately guess the number of discrete items immediately following rTMS.

• 8 became worse at guessing as the effects of the pulses receded

Advantages

• Opens possibility of changing one’s intelligence

• TMS studies on autism helps researchers to identify brain mechanisms that account for the disorder

• Once they identify these abnormal mechanisms in individuals with autism, they can develop treatments to reverse the symptoms of autism in adults and even treat the disorder preemptively in a child just as she/he is showing signs of autism

• Can test the effectivity of drugs in changing the hyperplasticity of the brain of individuals with autism

Limitations

•Savantism comes from “practice and specialization” (Howe)

•Practice may explain the improvement in certain skills i.e. drawing (Hendren)

•Savant-like skills are activated by the inhibition of the left fronto-temporal lobe only for the duration of the rTMS.

Other Applications

•TMS has the capability to be a novel antidepressant treatment.

•Because TMS is a non-invasive, non-drug therapy, it has been proven to be an effective, long-term treatment for major depression.

1. Depression

TMS was used to transiently disrupt left or right dorsolateral prefrontal cortex (DLPFC) function

It was found that the DLPFC plays a crucial role in the suppressing risk-taking behavior, confirming the role of the prefrontal cortex in decision-making.

A fundamental human capacity such as decision-making can be manipulated in normal subjects through TMS.

TMS can improve naming ability in Alzheimer disease patients at different stages of cognitive decline

2. Alzheimer’s Disease Therapy

3. Risk-Taking Behavior

Critiques & Limitations of TMS

Minor Short-Term Side Effects

• These side effects are generally mild and typically improve after the first week or two of treatment.

• Headache

• Scalp discomfort at the site of stimulation

• Tingling, spasms or twitching of facial muscles

• Lightheadedness

• Discomfort from noise during treatment

Uncommon, serious side effects (rare)

• Seizures

• Mania, particularly in people with bipolar disorder

• Hearing loss due to inadequate ear protection during treatment

Lastly

• TMS effects usually are not limited to the site of stimulation but spread either physically to neighboring areas

Advantages of TMS

• TMS can help in investigating a wide range of brain and cognitive functions, including the cause-and-effect relationships of brain activity and behavior, not just their correlations.

• TMS can enhance the results of other neuroimaging techniques by establishing the causal link between brain activity and task performance.

• TMS can help create “virtual lesions”

• Lesion studies are more functional imaging studies

A Cause-and-effect approach

TMS studies can be conducted in normal subjects, thus eliminating the need for studying actual brain lesions

TMS studies can be conducted intensely and avoiding any harm to the brain.

TMS studies can be repeated in the same subject, allowing one to conduct careful, controlled procedures.

Subjects can be tested with the exact same procedure, allowing accurate statistical evaluation of results.

Advantages of virtual lesion studies

Different areas of the brain can be targeted, which allows one to precisely map brain activity and behavior disruption in the brain.

Different related behavioral tasks can be tested, allowing one to identify specific areas of the brain to a certain cognitive function, ruling out more global mental impairment.

Advantages of virtual lesion studiesAdvantages of virtual lesion studies

Over 3500 papers have been published using or further developing the technique in the 20 years following the first demonstration of TMS.

A Wide, Diverse Scope of Research

The Future of TMS

Further studies

may shed light into neuropsychology of language and memory

may help enhance behavior and intelligence

In conclusion,

TMS provides a novel approach

to studying the relationship

between brain function and

behavior by creating virtual

patients.

Thank you!

References

• http://www.aetna.com/cpb/medical/data/400_499/0469.html

• http://www.youtube.com/watch?v=DBBDiGvupFw

• http://www.centreforthemind.com/images/savantskills.pdf

• http://www.nytimes.com/2003/06/22/magazine/22SAVANT.html?pagewanted=all

• http://www.centreforthemind.com/publications/SavantNumerosity.pdf

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