physiology of speech powerpoint ppt for Mbbs students

1. SPEECH
Dr U.Rathna kumari
MD Post Graduate
IPEM

2. • Speech is a highly evolved function of the
cerebral cortex.
• Speech is the human faculty by which thought
processes are symbolically expressed
• Speech is the vocalized form of human
communication
• Speech – peculiar to man.

3. • speech is a mode of communication by means
of sounds – language
• Language is one of the fundamental bases of
human intelligence and a key part of human
culture.
• Language is the symbolization of ideas
• Language consists of five parameters
Speaking, Hearing, Repeating, Reading, Writing.

4. • Central function
– cortical control
• Broca’s area & Wernicke’s area
• Peripheral function
– phonation
– articulation & resonance

5. The primary brain areas concerned with language
are arrayed along and near the sylvian fissure
(lateral cerebral sulcus) of the categorical
hemisphere.
 A region at the posterior end of the superior
temporal gyrus called Wernicke’s area is concerned
with comprehension of auditory and visual
information.
It projects via the arcuate fasciculus to Broca’s
area (area 44) in the frontal lobe.
Speech areas

6. cerebral dominance
• in right handers (90% of the population)
– left side is dominant
• in left handers (10% of the population)
– in 60% left side is dominant
– in 20% right side is dominant
– in 20% bilateral
• In most people, the left cerebral hemisphere is
the dominant hemisphere with respect to
language.

7. • but even for majority of left-handed individuals,
the left hemisphere is still dominant for language.
• This dominance has been demonstrated
• (1) by the effects of lesions of the left
hemisphere, which may produce deficits in
language function (aphasia), and
• (2) by the transient aphasia (inability to speak or
write) that results when a short-acting anesthetic
is introduced into the left carotid artery.

8. Differences in the size of an area called the planum temporale,
which is located in the floor of the lateral fissure, correlate with
language dominance. The left planum temporale is usually larger
than that of the right hemisphere.

9. Broca’s area
• Paul Broca (1861) was the first to provide
convincing evidence that language is localized
to a particular region of the brain.
• this is the motor (expressive) area for speech
• it is in the frontal lobe in front of inferior end
of the precentral gyrus(area 44)
• generally present in the
dominant side

10. Wernicke’s area
• Identified by Karl Wernicke – German
Neurologist
• this is the sensory (receptive) area for speech
• the posterior end of the superior temporal
gyrus in the dominant side
• comprehension of visual &
auditory information

11. Conduction Area
• A deep, white matter tract, connecting the
Wernickes area to the Brocas area.
• Also called arcuate fasciculus (Latin word) -
Curved bundle Neural tract
• Karl Wernicke described the pathway.

13. Exner’s Area
• Seigmund Exner Austrian Physiologist 1846-
1926
• Area just above Broca's area and anterior to
the primary motor control area.
• Area for writing - Close to motor area for hand
movement

14. Reading Area
• Anterolateral region of occipital lobe
• Centre for reading receives impulses from eye.
• is a visual association area that feeds visual
information conveyed by words read from a book
into Wernicke’s area, the language
comprehension area.
• The angular gyrus is needed to make meaning
out of the visually perceived words.
• In its absence, a person can still have excellent
language comprehension through hearing but not
through reading.

15. Area for Naming Objects
• The most lateral portions of the anterior occipital
and posterior temporal lobe.
• The names are learned mainly through auditory
input, whereas the
• physical natures of the objects are learned mainly
through visual input.
• In turn, the names are essential for both auditory
and visual language comprehension
(functions performed in Wernicke’s area located
immediately)

16. Posterior Superior Temporal Lobe —
“Wernicke’s Area”
(a General Interpretative Area)

17. • The somatic, visual, and auditory association
areas all meet one another in the posterior
part of the superior temporal lobe, where the
temporal, parietal, and occipital lobes all
come together.
• it plays the greatest single role in the higher
comprehension levels of brain function that
we call intelligence.
Comprehensive Interpretative Function of the
Posterior Superior Temporal Lobe

18. “Wernicke’s Area”
(a General Interpretative Area)
• Therefore, this region has been called by
different names suggestive of an area that has
almost global importance:
• the general interpretative area,
• The gnostic area,
• the knowing area,
• the tertiary association area, and so forth.

19. • It is best known as Wernicke’s area in honor of
the neurologist who first described its special
significance in intellectual processes.
• global importance of Wernicke’s area - for
processing most intellectual functions of the
brain.
• Loss of this area in an adult usually leads
thereafter to a lifetime of almost demented
existence.

20. Angular Gyrus—Interpretation of
Visual Information
• angular gyrus is the most inferior portion of the
posterior parietal lobe, lying immediately behind
Wernicke’s area and fusing posteriorly into the visual
areas of the occipital lobe as well.
• If this region is destroyed while Wernicke’s area in
the temporal lobe is still intact, the person can still
interpret auditory experiences as usual, but the
stream of visual experiences passing into Wernicke’s
area from the visual cortex is mainly blocked.

21. • Therefore, the person may be able to see
words and even know that they are words but
not be able to interpret their meanings. This is
the condition called dyslexia, or word
blindness.

22. Classical model of the LH language system.
Tyler L K , Marslen-Wilson W Phil. Trans. R. Soc. B
2008;363:1037-1054
©2008 by The Royal Society

23. The probable
sequence
of events
when a subject
names
a visual object
(horizontal
section of hum-
an brain)

24. W
B
B Broca’s area
W Wernicke’s area
visual impulses
angular
gyrus
auditory impulses

26. (f MRI)

28. • Language is one of the greatest gifts by nature to the
mankind. The ability to express our feelings and
understanding others' comes to us right from our
childhood when we start learning a language. The
journey starts with some peculiar sounds (which
normally babies use) which slowly turns into special
words like ma (or mamma) for mother , and the
vocabulary grows and reaches to something around
80,000 words for high school graduates and
approximately double for people associated with
literature . Throughout our life we keep on learning
and building our vocabulary.

29. • It is interesting that in individuals who learn
a second language in adulthood,
• fMRI reveals that the portion of Broca’s area
concerned with it is adjacent to but separate
from the area concerned with the native
language.
• However, in children who learn two
languages early in life, there is only a single
area involved with both.

30. Cerebral asymmetry
• Cerebral hemispheres have shown asymmetry
for speech as well as for many other cognitive
functions
• Split brain operations performed in 1950-60 to
prevent spread of epilepsy has given valuable
information about the functional asymmetry

31. Left side
• Mostly the dominant side
• Verbal
• Temporally sequential in processing
• Mathematical leaning

32. Right side
• Mostly the non-dominant side
• Non-Verbal
• Non-Mathematical non-sequential processing
• Visuospatial tasks: reading faces, mental
spatial transformations, perceiving whole
from parts
• Musical perception

33. This functional asymmetry in a
structurally symmetrical structure is a
unique human attribute
L R