NSCI 110 1st EditionExam #3 Study Guide Chapters 10, 11, 12, 14 (Book Notes)Chapter 10: Functional Anatomy of the Auditory System- Auditory receptors are the inner hair cellso Cilia of the inner hair cells do not touch the overlying tectorial membrane, so they bend when fluid flows through o Outer hair cells sharpen resolution by contracting or relaxing This changes the stiffness of the tectorial membrane Movement causes calcium channels in these cells to open or close  an influx of calcium causes the inner hair cells to be stimulatedo Movement to the left towards the taller cilia results in depolarization Calcium channels open and an action potential is induced- Pathways to the auditory cortexo Inner hair cells synapse with bipolar cells These bipolar cells form the auditory (cochlear) nerve Receive input from a single inner hair cell receptor o Cochlear nerve axons travel to the brainstem and synapse in the medulla with the cochlear nucleus Ventral stream has projections to the superior olive and trapezoid body (both in brainstem) Dorsal stream has projections directly to the inferior colliculuso Projections can travel contralaterally or ipsilaterally All information is carried to the inferior colliculus, where it branches contralaterally or ipsilaterally into either side of the medial geniculate nucleus (MGN) in the thalamus From the MGN information can travel either to the primary auditory cortex (A1) or auditory cortical regions around it- The primary auditory cortex lies among Heschl’s gyrus o A2 areas lie adjacento Wernicke’s area is adjacent to A1 but on the opposite side than the A2 Also called “planum temporale” or “posterior speech zone” Larger on left side of the brain because of its role in generating speecho Heschl’s gyrus is larger on the right side because of its role in analyzing musico The auditory cortex surrounds the insula (perpendicular to lateral fissure) Multifunctional cortical tissueo The localization of certain tasks on one side of the brain is lateralization- Hearing pitch involves tonotopic representation on the basilar membrane  highest frequency at the base and lowest at the tip (maximal displacement by those particular sound waves occurs at different locations along the basilar membrane)o The axons travelling to the primary auditory cortex in order Anterior end  low frequencies Posterior end  high frequencieso Cochlear implants are devices inserted in the inner ear to allow deaf people to hear Transduce sound waves and send them to corresponding locations on the basilarmembraneo The cochlea has difficulty differentiating pitch in low-frequency ranges (less neurons)- Detecting loudness is controlled by higher or lower firing rates of bipolar cellso More intense vibrations lead to more shearing and increased neurotransmitter release More frequent signals indicate louder sounds- Detecting the source of a soundo Neurons take into account the different between arrival times of sound waves between each ear This is accomplished by the superior olivary complex- Receive input from each ear and can compare arrival times When we detect no difference the sound is coming from either directly behind or in front of us Difficult to distinguish above from below, however- Compensate by tilting or turning our headso Also compare loudness from both sides Higher frequency waves cannot as easily bend around the head, so these pitchesare louder to the ear it hits first- Lateral superior olive and trapezoid body- Detecting patterns in soundo Ventral pathway is responsible for auditory object recognition Decoding the meaning of speech sounds into recognizable wordso Dorsal pathway is responsible for integrating auditory and somatosensory info for speech production- Broca confirmed that language was lateralized to the left hemisphere and specific functions are localized to different parts in ito Area just anterior to the central fissure is Broca’s area Unable to speak despite language comprehensiono How to relate speech to hearing? Wernicke’s area is posterior to the central fissure This area is responsible for comprehension of languageo Wernicke’s vs. Broca’s aphasia  aphasias induced by damage to any speech areas- Wernicke’s model ~ Wernicke proposed that images of words are encoded by their sounds o When we hear a word that matches that stored sound image, we recognize it (comprehension) Occurs in posterior temporal lobeo Broca’s area receives information from Wernicke’s area through the arcuate fasciculus Controls articulation of words by activating motor activityo However, based this on postmortem observations of huge lesions (not as accurately mapped as the current model)- Auditory and speech zones are spatially mappedo Electrical stimulation of either Broca’s or Wernicke’s areas disrupts BOTH processeso Neurosurgery for intractable epilepsy  patient is awake and conscious  Surgeon performs operation and neurologist analyzes EEG- Numbered tickets on different brain surface areas where there are noticeable changes in patient’s behaviors or sensations (produces a cortical map) Found that A1 stimulation produced simple tones, ringing sounds- Stimulation in adjacent auditory cortex caused some interpretation to sound Speech also controlled by dorsal area of frontal lobe and motor/somatosensory cortices that control facial, tongue, throat muscles- Processing musico Music perception involved in the right hemisphere and composing music involved in the left Listening to bursts of noise  Heschl’s gyrus Listening to melodies  A2 (right hemisphere) Comparing pitches  right frontal lobeo Amusia is tone deafness (inability to distinguish between notes) Cortical thickness that is abnormal may result in musical ineptness or deficits Musicians with perfect pitch have thinner cortex in posterior part of dorsolateralfrontal lobeo We may have a musical innateness  infants prefer musical scales over random notes Bias for regular rhythms- Music is used as a therapeutic tool to engage cerebral regionso Treatment for mood disorders like depression, stroke, and Parkinson’so Listening to rhythm activates the motor and premotor cortex Can improve gait and arm training after stroke- Parkinson’s patients walking to the beat of music Enhances ability to discriminate speech sounds and distinguish speech from