?Involvement of nuclei at different level
?Applied anatomy
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Auditory pathway
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?Transmits auditory stimulus from hearing receptors(organ of corti`s) to auditory area in cerebral cortex.
1. Organ of Corti (receptor)
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2. Dorsal & ventral cochlear nuclei
3. Trapezoid body & Superior olivary nuclei
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4. Lateral lamniscus5. Inferior colliculus
6. Medial geniculate body
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7. Auditory radiation
8. Auditory cortex
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3Auditory pathway
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?Cochlear nu-receptors- hair cells in Organ of Corti?1st order neuron- spiral ganglion- bipolar neurons ?
peripheral process- hair cells of spiral ganglion ? central
processes & axons - cochlear nerve- bifurcates & terminate
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in Dorsal & Ventral Cochlear Nu ? 2nd order neurons -dorsal & ventral ? axons CROSS & few uncrossed in dorsal
part of Lower part of pons - Superior Olivary nucleus-
?3rd Neuron ? Superior Olivary Nucleus - lateral lemniscus
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Formation of Trapezoid body- In dorsal part of pons ?
intermediate /dorsal acoustic striae-nucleus of trapezoid
body.
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?Lateral lemniscus ? terminate at ?Inferior Colliculus (MB)?Inferior colliculus - 4th order of neuron- (Inf Brachiaum)
Auditory pathway
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?Inferior colliculus - 4th Order Neuron - center for
auditory reflexes Medial Geniculate body
through inferior brachium.
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?Medial Geniculate body - 5th order of neuron & is -
Final Relay Station - hearing pathway.
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?5th order of neuron ? starts from MGB- formsacoustic radiation -reaches- acoustic area of
cerebral hemisphere ?
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?Acoustic area accepts bilateral impulses.?Temporal lobe - Superior Temporal gyrus area
41,42.
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8
9
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Auditory area....?Primary auditory area - floor of post ramus of lateral
sulcus.
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?Superior surface of superior temporal gyrus has two
transverse temporal gyri (Heschl's gyrus)
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? area-41 & 42 receives inputs from medial geniculatebody.
Auditory areas
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?Primary auditory area ? area 41
?Superior temporal gyrus ? bilateral representation
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?Detection of direction & frequency of sound.?Lower frequencies are located in anterior/lateral
part & higher frequencies are located in
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posterior/medial part?Auditory association area - area 42 ? co-relates
and comprehension of present stimulus to past
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ones?Higher Auditory association area - area 22 ?
Wernicke's area- comprehension of spoken
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language & interpretation of sound.Auditory areas
?Lesion of primary auditory area 41 & 42 of one side
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produces bilateral partial deafness, b/o bilateralreceiving of inputs via medial geniculate body.
?Auditory association cortex- area 22 , Wernicke's
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speech area. Interpretation of sounds on pastexperiences. Sensory aphasia.
?Olfactory area- 28 , lateral olfactory stria & gyrus
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,anterior part of parahippocampal gyrus & uncinategyrus.
?Area 8 ? frontal eye field
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?Area 44 & 45 ? Broca's speech area ? motorspeech area in dominant cerebral hemisphere.
?Prefrontal cortex- (area - 9-12)
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?Depth of feeling
?Foresightedness
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?Tactfulness?Mature judgement
?Pleasure & displeasure
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?Lesion of prefrontal cortex (9 -12) - Lack of selfresponsibility ,Vulgarity of speech, euphoria ,
clownish behaviour
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?Area-40- Astereognosis & tactile aphasia?Area-39 ? word blindness ? unable to read
words even if were written by one self
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?Area 22 - word deafness - sensory aphasia.
Decreased interpretation of sounds/words and
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increased frequency of word produced....?Area 44 & 45 ? motor aphasia
Speech area....
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Wernicke's area- 22, dominant hemisphere ,
interpretation of spoken ,written ,symbols & signs.
Allows understanding of written & spoken language.
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Angular gyrus - interconnects -visual area & auditoryareas.
Wernicke's is necessary for- language
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comprehension while Broca's area, 44, languageproduction. Superior longitudinal fasciculus or
arcuate fasciculus interconnect these two areas.
Sensory aphasia- unable to understand written or
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spoken words with normal vision/hearing.
Speech area's.....
?Apraxia- parietal lobe -impairment of performance
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of learned movements.
?Wernicke's aphasia- inability to understand spoken or
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written words ? Broca's ok- uses all meaningless andincorrect words...no meaning. Called-fluent aphasia
or receptive aphasia ,
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?Broca's aphasia- unable to articulate words-nonfluent aphasia, hesitant aphasia /distorted-
?What they wish to say but can not speak.
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?Global aphasia- extensive damage to cortex