CEREBRAL DOMINANCE / KUNNAMPALLIL GEJO
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Transcript of CEREBRAL DOMINANCE / KUNNAMPALLIL GEJO
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KUNNAMPALLIL GEJOJOHN,MASLP
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KUNNAMPALLIL GEJO JOHN,
BASLP, MASLP
KUNNAMPALLIL GEJOJOHN,MASLP
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Definition…
Cerebral dominance refers
to the dominance of one
cerebral hemisphere over
the other in the control
of cerebral functions.
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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.
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LEFT AND RIGHT BRAIN FUNCTIONSKUNNAMPALLIL GEJO
JOHN,MASLP
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How is theinformation
processed differently in
differenthemisphere???
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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
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Cerebral
dominance studies
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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.
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Methods to
investigate hemispheric
processing
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Tachistoscopic visual methods
A
P
PL
ER / L eyestimuli
R
L
Hines and Moore
1976
(100ms)
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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.
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Dichotic listening task
L ear
R ear R hemi
L hemi
R earadvantage
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Scalp recorded averaged evoked responses
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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]
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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.
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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]
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Cortical blood flow
Based on,
Change
in blood
flow
Metabolism
and tissue
activity
Lassen, Ingvar et al.,
1978
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more activity hemisphere
more regional blood flow
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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]
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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
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Cerebral
hemisphere
asymmetries
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Cerebral hemisphere asymmetries
Morphological asymmetries
Geshwind &
Levistsky,
1968
PL
A
N
U
M
T
E
M
P
O
RA
L
E
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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.
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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
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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)
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Spatial stimuli under analyticaltask demands – R hemi
(Weheatly, Willis.,1979)
Trained musicians process music
more L hemispherically than non
musicians. (Gates and Bradshaw,
1977)
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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).
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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.
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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.
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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
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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
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HEMISPHERIC PROCESSING
OF STUTTERINGINDIVIDUALS
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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
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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]
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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.
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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]
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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.
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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.
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JOHN,MASLP
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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
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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.
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JOHN,MASLP
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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].
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JOHN,MASLP
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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.
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JOHN,MASLP
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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.
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JOHN,MASLP
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Evidence from neuro imaging
techniques
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JOHN,MASLP
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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.
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JOHN,MASLP
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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.
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KUNNAMPALLIL GEJO