SENSATION AND PERCEPTION EXAM 2 What is the spiral ganglion spiral ganglion group of cell bodies clustered together in the peripheral nervous system somas clustered at spiral ganglion dendrites synapse at the base of hair cells axons synapse in ipsilateral cochlear nuclei nucleus group of cell bodies clustered together in CNS In order what brain structures are involved in the auditory pathway and what is a main function of each of those stops Auditory Pathway all structures from basilar membrane to cortex have tonotopic organization this pathway is bilateral so almost all structures get information directly or indirectly from both ears Brain Structures involved in Auditory Pathway 1 Cochlear nuclei medulla pons gets ipsilateral information from 8th cranial nerve different types of specialized neurons that respond preferentially to different aspects of a sound ex Onset of a sound at a given frequency some fire action potentials with the same rate as auditory nerve fibers that synapse upon them neurons project to superior olive in pons inferior colliculus 2 Superior Olive pons first place in brain to get info from both ears via cochlear nuclei left CN to left and right SO and vice versa important in sound localization medial superior olive interaural time difference lateral superior olive interaural intensity difference 3 Inferior Colliculus Midbrain map of auditory space important structure for orienting toward a sound tectospinal pathway goes from there back down to cervical spinal cord to help direct muscles of neck to turn your head 4 Medial Geniculate Nucleus MGN thalamus relay filter for auditory info heading to cortex projects to primary auditory cortex recieves projections back from cortex 5 Primary Audio Cortex A1 superior part of temporal lobe it s a little medial to the surface of the brain a lot of processing has already occurred prior to the cortex as move through cotex processing becomes more sophisticated understanding speech is a good example of this doesn t happen in A1 primary auditory cortex A1 any sounds elicits activity tonotopic organization secondary auditory cortex A2 belt zone more complex sounds elicit activity auditory association cortex parabelt zone more complex sounds elicit acitivity processes other sensory info as well Also Why is the superior olive a good place for sound localization to occur hint think about where it gets info from What cues does this region use to localize sound lateral inhibition sharpen tuning to 1 freqeuncy by suppressing nearby frequencies What is different b t the midbrain of different critters think humans compared to birds and fish and why the difference tectum inferior colliculi superior colliculi part of midbrain is very big in birds and fish very important in orienting to a stimulus inferior colliculi auditory info superior colliculi visual info What is the difference b t interaural time difference interaural intensity difference What brain structure is responsible for each What where is auditory cortex primary secondary and association What is tonotopic organization How do these parts of cortex differ from each other in terms of processing What are Wernike s and Broca s areas important for What about insula What are Broca s and Wernike s aphasias Speech Processing in the Brain A1 of course deep in lateral sulcus belt zone and parabelt zone too when listening to speech or music but at this level the activation is balanced between the hemispheres language is usually in left hemisphere it is lateralized as sounds become more complex they are processed more anterioally and ventrally to A1 Broca s Area important in the motor production of speech to a much lesser extent in comprehension Wernicke Area important in language comprehension insula pronounciation of words part of frontal lobe of L cortex near motor cortex Broca s Apahasia non fluent aphasia caused by damage to Broca s area and surrounding area difficulty with motor production of words spoke signed written omit prepositions and conjunctions and have difficulty understanding them trouble with writing and gestureus comprehension deficits with complicated senstence structure trouble saying no ifs ands or buts trouble reading to be or not to be so mild problem with language not just vocal muscles problems with articulation in BA could reflect damage to the insula patients misprounce words lipstick likstip pateitns with apraxia of speech almost always have damage to the insula fMRI shows activation of left anterior insula and BA during pronounciation of words Wernicke s Aphasia fluent aphasia impaired ability to remember names of objects impaired language comprehension articulate speech speak smoothly but nonsense difficulty finding the right word What is prosody prosody rhythmic musical aspects of speech right hemisphere What parts of the brain are important for processing language What is different between the left and right hemispheres in terms of language speech processing Blue listening to complex sounds and speech bilateral yellow categorizing sounds green speech forms intelligible sentences lateralized Describe sketch the Jeffress model of sound localization What brain region does this interaural time difference auditory pathway hair cells cochlear nuclei superior olive inferior coliculus MGN A1 a sound coming from 1 side of the head will arrive at that ear louder than the other ear interaural level intensity difference sooner than the other ear interaural time difference medial superior olive lateral superior olive each cochlear nucleus projects to the ipsilateral and contralateral MSO and LSO How do we determine the interaural level difference and what brain region does that How does that brain region make the comparison Why is ILD different from front to back Interaural level difference at 90 and 90 nonexistent at 0 and 180 true for ITD as well correlation for angles between isn t quite as good as with ITDs because irregular shape of head and pinnae sound is most intense in nearest ear head blocks high frequency sounds better than low frequency sounds so greater ILD for high frequency sounds than for low frequency sounds 6000 Hz vs 200 Hz not symmetrical from front to back because of filtering characteristics of pinnae 4000 Hz 60 vs 120 ILD is analyzed in LSO LSO gets excitatory input from ipsilateral ear and inhibitory input from contralateral ear via MNTB a sound coming from the left side will be more intense in the left ear and therefore better at
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