CEREBRAL DOMINANCE / KUNNAMPALLIL GEJO

7/27/2019 CEREBRAL DOMINANCE / KUNNAMPALLIL GEJO

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KUNNAMPALLIL GEJOJOHN,MASLP



KUNNAMPALLIL GEJO JOHN,

BASLP, MASLP




Definition…

Cerebral dominance refers

to the dominance of one

cerebral hemisphere over

the other in the control

of cerebral functions.




The medical term On Cerebral

Dominance refers to thespecialized way each half of our

brain operates and the dominion it

has over certain bodily and mental

functions.

Left is…

Analytical,

Compartmentalizing.

Right is…

Holistic,

Intuitive.




LEFT AND RIGHT BRAIN FUNCTIONSKUNNAMPALLIL GEJO

JOHN,MASLP



How is theinformation

processed differently in

differenthemisphere???




Left hemisphere Right hemisphere

Serial processing Parallel processing

Past and future

moments

Present moment

Thinks in pictures

and learns through

body movt..

Thinks linearly and

methodologically




Cerebral

dominance studies




The CNS characteristics are

examined in terms of

information processing

strategies of the cerebral

hemispheres.

It is well understood by the

observation of behavioral

events and relating them to

known or theorized CNS

functions.




Methods to

investigate hemispheric

processing




Tachistoscopic visual methods

A

P

PL

ER / L eyestimuli

R

L

Hines and Moore

1976

(100ms)




Limitations:

1. Information can be presented only

for a shorter duration.

2. Only short stimulus arrays can beused.

3. Controlled luminous conditions are

needed along with sophisticatedequipment to present and time the

stimulus parameter.




Dichotic listening task

L ear

R ear R hemi

L hemi

R earadvantage




Scalp recorded averaged evoked responses




Advantages:

1.Allows observation of a specific

cortical responses over cortical

areas, hence helps to localize

hemispheric function.

2.Can be used to study relative

activation latencies of

different cortical areas.

[Brown, Marsh, Smith et al.,1980]




Hemispheric alpha asymmetries

Various investigation have

shown that suppression of alpha

brain wave freq [8-13Hz] over

the hemisphere primarilyprocessing specific information

under specific task condition.

Moore as Haynes [1980]variables affecting asymmetry

include gender, task stimuli.




Advantage:

It can be used to study

hemisphere processing over time

using a variety of stimuli such

as phrases and sentences..

Limitations:

Scalp electrodes are used.

Hence results reflect activityof many small zones of cortical

surface benath the electrodes

[Cooper et al., 1974]




Cortical blood flow

Based on,

Change

in blood

flow

Metabolism

and tissue

activity

Lassen, Ingvar et al.,

1978




more activity hemisphere

more regional blood flow




Xenon 133 inhalation method:

Inhales xenon for 1min

ten min normal air breathing

Detectors are placed on scalp and level of

radioactivity is monitored via computer

analysis.

Change in regional blood flow indicate

metabolic changes and consequently, the

various neuronal activity of various sites

in brain

Within and between hemisphere measurement is

also possible.[wood, 1980]




Temporary anesthetization of

cerebral hemisphere

Wada (1949) injected general anesthetic to

be injected to the R / L carotid artery.

It lasts for 2 – 3 min,

Result: temporary loss of language was

evident.

Limitation:

Invasive.

Indicates only gross interhemisperic

activation.

Restricted to medical personnel




Cerebral

hemisphere

asymmetries




Cerebral hemisphere asymmetries

Morphological asymmetries

Geshwind &

Levistsky,

1968

PL

A

N

U

M

T

E

M

P

O

RA

L

E




L occipital horn > R occipital horn

(Mc Rae,

Branch and

Milner 1968)

Suggested

that there

is more

white matter

on the

posterior

portion of R

hemisphere.




L and R

pulvinars are

involved in info processing.

R pulvinar was

involved in processing

visual stimuli.

L pulvinar involved with

verbal or

auditory stimuli




Cognitive/ behavioral

asymmetries

L hemi – process brief sounds (<100ms)

to analyze constituents parts

of auditory stimuli. (Tallal

and Newcomb., 1978).

R hemi – process visual information to

scan auditory and visual

environment to process steady

state information. (Tallal and

Day., 1979)




Spatial stimuli under analyticaltask demands – R hemi

(Weheatly, Willis.,1979)

Trained musicians process music

more L hemispherically than non

musicians. (Gates and Bradshaw,

1977)




Speech is more lateralized

linguistic function i.e. to left

hemi, where as language is least

lateralized being present in

various degrees in both hemi’s.

The R hemi comprehend spoken

words by performing acoustic

pattern match with stored

exemplars, than performingacoustic analysis like L hemi.

(Zaidel.,1979).




The lexicon in the R hemi is

connotated associative and

imaginative where as, that of

left are precise, denotative and

phonologic (Bradshaw., 1980).

Hence studies suggest that

language is not lateralized to

the L hemi, what is laterslized

is all some processing strategies

or mental operations, which

process verbal/ acoustic

parameters of linguistic stimuli.




Variables which affect right and

left hemisphere processing

Authors: Zaidel (1979)

Method: dichotic / tachistopic

Variable: phonological component in

nonsense syllables.

Results: greater phono comp, greater

the left hemi activation.




Author: Tallal and Newcombe (1978)

Method: responding sounds of varying

duration

Variable: duration of auditory

stimuli

Result: L hemi damaged subjects were

impaired in their ability to respond

to sounds of brief duration




Author: Faber – Clark and Moore (1983)

Method: alpha suppression

Variable: recall and recognition and

word lists

Result: greater L hemi supp with recall

greater R hemi suppression for

recognition




HEMISPHERIC PROCESSING

OF STUTTERINGINDIVIDUALS




CNS investigation --- str lackCD for speech

[Travis and Orton 1931]

Travis.,1931

Hypothesized,

Stg results from asynchronous

arrival of nerve impulses in b/ljaw muscles




Douglass et al., 1943

Str – less time alpha in R occipital

area when compared to left during

silence.

EEG studies – neuronal dysfunction

rather than hemispheric

differences [Fox., 1960]




WADA TECHNIQUE Wada and Rasmussen., 1960 found

4 str demonstrated transient aphasia

regardless of either L/R side sodium amytal

injection, suggesting lack of cortical

dominance for speech.

Follow up studies…

Andres et al, 1972, failed to find significant differences between those who

stuttered and those who did not with regard

to hemispheric dominance for language.




DICHOTIC LISTENING

Meaning linguistic stimuli have usuallyshown stutterers with left ear advantage.

[ Brady and Moore, 1975]

LEA – words and NO EAR advantage for nonsense syllables.

[ Perin & Eisenson, 1970]

No REA for severe stutterers while least

severe stutterers found to be similar to

non str.

[ Davenport, 1979]




Rosenfield & Goodglass, 1980,

found that str were inferior tonon str in all comparisons of

response to CV non sense syll

and interpreted these findings

as evidence of a phoneme

perception deficiency.

The obtained LEA could reflect

the deficiency of R hemi processing of phonological

information.




TACHISTOSCOPIC VISUAL

PROCEDURE

Using meaningful linguistic stimuli

Moore, 1976, reported

Str had L field preference than non str.

Plakosh [1978] found

No visual field preference for str and

concluded that str were more dependent onvisuospatial aspects of visually presented

linguistic stimuli than non str.

KUNNAMPALLIL GEJO

JOHN,MASLP



ELECTRO PHYSIOLOGICAL

METHODS

Moore & Mc Farland, 1980

Alpha supp was more in R post

temporoparietal areas in stutteres.

Comprehension of connected verbal

discourse was unaffected in male

stutterers and reduced alpha supp.

Suggested that R hemi superiority in

processing semantic aspects of

language.KUNNAMPALLIL GEJO

JOHN,MASLP



CEREBRAL BLOOD FLOW

Wood, Stumps et al., 1980,

2 str were sujected to CBF

measurements while reading aloud.

2 conditions:

1st – under haloperidol – read –

increased fluency

2nd – without medication – both str

showed increased CBF in brocas area onR compared to L hemi during sttg.

During fluent movt CBF was observed in

L hemi compared to R hemi.

KUNNAMPALLIL GEJO

JOHN,MASLP



THEORIES OF CEREBRAL

DOMINANCE

In 1920’s a numb of reports

suggest that individual who

stutter are most likely to beleft handed or ambidextrous than

non stutterers and onset of stg

is in conjunction with attempts

to change in their handedness

[Bloodstein, 1933].

KUNNAMPALLIL GEJO

JOHN,MASLP



Orton proposed theory of cerebral

dominance and Lee Edward Travis popularized Orton’s theory.

Orton and travis theorized that because muscles of speech mechanism

receive nerve impulses from both L

and R hemi, one hemi needs to be

more dominant for the speech movt

to be synchronized.

KUNNAMPALLIL GEJO

JOHN,MASLP



They suggest that NS of people whostr had not matured sufficiently

to achieve hemispheric dominance

over speech movt.

This maturational failure could

have resulted from hereditary

influence, disease injury or

emotional arousal or fatigue.

KUNNAMPALLIL GEJO

JOHN,MASLP



Evidence from neuro imaging

techniques

KUNNAMPALLIL GEJO

JOHN,MASLP



Author : Ingham and Ingham, 1994

Method: PET and CBF

Subjects: 4 adult with developmental

stuttering and 4 normal speakers.

Result: Incresed BF to thesupplementary motor area to superior

lateral premotor cortex during sttg.

KUNNAMPALLIL GEJO

JOHN,MASLP



Author : Hurley M , Heilman KM , 2001

Method: MRI

Subjects: 16 adult with persistent

developmental stuttering.

Result: the right and left planum temporale

were significantly larger in the adults withPDS . Some gyral variants were unique to the

adults with PDS, including a second diagonal

sulcus and extra gyri along the superior

bank of the sylvian fossa.

KUNNAMPALLIL GEJO

JOHN,MASLP

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KUNNAMPALLIL GEJO

CEREBRAL DOMINANCE / KUNNAMPALLIL GEJO

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