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The Abnormal and Aging Auditory System.docx

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Paul Faure

December 4 , 2013 Psych 3A03: Audition The Abnormal and Aging Auditory System Onset and Offset Time - Recall that some auditory neurons are sensitive to sound duration, some are sensitive to onset, and some are sensitive to offset: these cues help our auditory systems fuse and segregate sounds of different sources - Not limited to absolute onset and offset – rate of onset, called the attack, and rate of offset, called the release, are often important Temporal Modulations - Most sounds we hear have temporal modulations - Sounds with similar temporal patterns tend to be perceptually fused (grouped)  E.g. musicians playing/singing in time with one another - Sounds with distinct temporal patterns tend to be segregated Comodulation masking Release (CMR) - Subjects asked to detect target ban when either in the presence of a cue band or not - Noise modulated in time - Noise band is either comodulated in amplitude modulation or not to the target band - When they are amplitude modulated the same way, thresholds decrease by 10dB Modulation Detection Interference (MDI) - Probe = 4000Hz - Masker = 1000Hz - Can detect depth of modulation when there is no masker - Signals with a masker that is not amplitude modulated: thresholds slightly increase - Masking signal modulated with the same modulation function as the probe: threshold for detect increases - Modulated at a faster rate than the probe, threshold decreases - Have the same modulation causes them to fuse and we are getting more interference The Abnormal Auditory System - The auditory system can become (or start out) dysfunctional in a number of ways:  Repeated exposure to loud noise  Aging  Pharmacological effects (e.g. ototoxic drugs)  Infections and diseases  Accidents, and  Heredity - Audiologust and otorhinolaryngologists use clues from behaviour and psychophysics to aid in diagnosis and treatment - One important distinction is between symptom and cause – abnormalities in behavioural and psychophysical tests are symptoms Hearing Loss - Hearing loss is a symptom of auditory dysfunction - Many other problems arise as a result of hearing loss (communication disorders, tinnitus, hyperacusis, etc.) - Measured with audiometry (by an audiologist) by looking for a threshold shit - Hearing losses divided into two types by their cause:  Conductive hearing loss (peripheral)  Sensorineural hearing loss How Hearing is Measured - Measured in dB HL - 0: thresholds are not significantly different - Hearing losses at different frequencies Hearing Loss and Threshold Shift - Normal - Mild: thresholds are increased at high frequencies, and therefor sound localization is more difficult but can still use ITD - Moderate: decrease in the speech spectrum - Severe: functionally death - Profound Conductive Hearing Loss (CHL) - Conductive hearing loss: increase in hearing threshold associated with diminished conduction of sound - Diminished conduction of sound in outer or middle ears results in decreased stimulation of the basilar membrane - Has several common causes:  Wax buildup  Damage to tympanic membrane (ruptured eardrums)  Otitis media CHL: Otitis Media and Ear Tubes - Middle ear infections (otitis media) can cause painful swelling and conductive hearing loss in the middle ear - Repeated ear infections and severely blocked Eustachian tubes in children are not uncommon and sometimes require surgical treatment to restore middle ear function - Tympanostomy tubes are inserted into the tympanic membrane to allow pressure equalization and drainage of the middle ear CHL: Otoslerosis and Stapedectomy - Ostesclerosis: calcification of the ossicular chain - Can cause a conductive hearing loss - Solution to this is to surgically remove the stapes and insert a small pin, attached to the incus and grafted through the oval window – essentially an artificial replacement for the stapes CHL: Stapectomy - Surgery to inset artificial stables Sensorineural Hearing Loss (SNHL) - Hearing loss resulting from change in hair cell or auditory nerve function is sensorineural hearing loss - Causes of sensorineural hearing loss are many and not always clear - Most common cause of SNHL is too much mechanical stimulation of basilar membrane and hair c
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