?Involvement of nuclei at different level
?Applied anatomy
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2
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
?Cochlear nu-receptors- hair cells in Organ of Corti
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?1st order neuron- spiral ganglion- bipolar neurons ?peripheral process- hair cells of spiral ganglion ? central
processes & axons - cochlear nerve- bifurcates & terminate
in Dorsal & Ventral Cochlear Nu ? 2nd order neurons -
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dorsal & ventral ? axons CROSS & few uncrossed in dorsalpart 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.
?Lateral lemniscus ? terminate at ?Inferior Colliculus (MB)
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?Inferior colliculus - 4th order of neuron- (Inf Brachiaum)Auditory pathway
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?Inferior colliculus - 4th Order Neuron - center forauditory reflexes Medial Geniculate body
through inferior brachium.
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?Medial Geniculate body - 5th order of neuron & is -Final Relay Station - hearing pathway.
?5th order of neuron ? starts from MGB- forms
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acoustic radiation -reaches- acoustic area of
cerebral hemisphere ?
?Acoustic area accepts bilateral impulses.
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?Temporal lobe - Superior Temporal gyrus area
41,42.
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89
Auditory area....
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?Primary auditory area - floor of post ramus of lateralsulcus.
?Superior surface of superior temporal gyrus has two
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transverse temporal gyri (Heschl's gyrus)
? area-41 & 42 receives inputs from medial geniculate
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body.Auditory areas
?Primary auditory area ? area 41
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?Superior temporal gyrus ? bilateral representation
?Detection of direction & frequency of sound.
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?Lower frequencies are located in anterior/lateralpart & higher frequencies are located in
posterior/medial part
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?Auditory association area - area 42 ? co-relatesand comprehension of present stimulus to past
ones
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?Higher Auditory association area - area 22 ?Wernicke's area- comprehension of spoken
language & interpretation of sound.
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Auditory areas?Lesion of primary auditory area 41 & 42 of one side
produces bilateral partial deafness, b/o bilateral
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receiving of inputs via medial geniculate body.?Auditory association cortex- area 22 , Wernicke's
speech area. Interpretation of sounds on past
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experiences. Sensory aphasia.?Olfactory area- 28 , lateral olfactory stria & gyrus
,anterior part of parahippocampal gyrus & uncinate
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gyrus.?Area 8 ? frontal eye field
?Area 44 & 45 ? Broca's speech area ? motor
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speech area in dominant cerebral hemisphere.
?Prefrontal cortex- (area - 9-12)
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?Depth of feeling?Foresightedness
?Tactfulness
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?Mature judgement
?Pleasure & displeasure
?Lesion of prefrontal cortex (9 -12) - Lack of self
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responsibility ,Vulgarity of speech, euphoria ,
clownish behaviour
?Area-40- Astereognosis & tactile aphasia
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?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
increased frequency of word produced....
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?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.
Angular gyrus - interconnects -visual area & auditory
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areas.Wernicke's is necessary for- language
comprehension while Broca's area, 44, language
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production. Superior longitudinal fasciculus orarcuate 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