Hearing Loss and Treatment 1 Understand the difference between conductive and sensorineural hearing loss in terms of where they are and what can cause them Conductive Tympanic Membrane and or ossicles can t move properly they don t transmit amplify vibrations to the cochlea Caused by obstruction in the ear canal or eardrum perforation penetration trauma or increased pressure such as a qtip otitis media middle ear fills with mucous during an infection o thresholds are raised by 50 DB o resolved as the infection clears o Otosclerosis abnormal growth of middle ear bones especially near the oval window by the stapes o Surgery is needed to free ossicles from bone growth o Aural Atresia and Micortia right o AA absence of auditory canal TM o M Severe deformation of the external o Usually occurs without middle ear damage or damage to the auditory nerve ear left o Sensorineural Damage to hair cells auditory nerve or Can be confined to a certain part of the both cochlea Caused by o Age related changes Presbycusis affects high frequencies first in part due to exposure to everyday noise o Noise induced affects around 4 000 Hz Single loud incident gun Long term exposure factory music o Ototoxicity drugs some antibiotics and cancer drugs are toxic to hair cells o Inherited developmental malformed cochlea Prenatal problems drug or alcohol exposure CMV rubella syphilis etc Perinatal infantile childhood disorders Hypoxia premature birth measles severe ear infections 2 What sorts of capabilities do modern hearing aids have Don t just amplify sounds Amplify signal and compress intensity differences Amplify sounds for frequencies that are most impaired Amplify speech and diminish noise Directional amplify speech in one direction with directional microphones amplify in front not in back 3 How do cochlear implants work What patients would be candidates for an implant Remember that the auditory nerve must be in tact Auditory nerve must be intact Tiny flexible coil with about 24 mini electrodes Threaded through round window and into the cochlea Connected to radio receiver under the scalp and signals are transmitted from microphone behind the ear Signals stimulate the AN fibers sounds aren t normal Sound Localization 1 Describe sketch the Jeffress model of sound localization What brain region does this interaural time difference Sound reaches the close ear first Action potential travels toward the MSO Sound reaches the far ear a little later Action potential begins traveling toward the MSO Action potentials converge on an MSO neuron that responds most strongly if their arrival is coincident 2 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 ILD in which ear is the sound more intense ILD is largest at 90 degrees and 90 degrees and nonexistent at 0 180 degrees The LSO Lateral Superior Olive gets excitatory input from the ipsilateral ear and inhibitory input from the contralateral ear A sound coming from the left side will be more intense in the left ear bc it is exciting LSO neurons on that side and inhibiting them on the other more activity Our head isn t a perfect circle and the pinnae are not symmetrical either The head blocks high frequency sounds better than low greater ILD for high than low This is because low frequency sound waves have more space between them therefore they can pass over the head without being affected by its shape 3 What are the cones of confusion Same ITD at 40 60 degrees and 120 degrees 4 What cues do we use to determine how far away a sound is Hint we described 3 Relative intensity of a sound Works close within 1 meter Intensity works best as a cue if the sound source is moving Spectral composition of a sound Higher frequencies dampen more than lower frequencies thunder is a crack nearby or a boom further away Direct vs reverberant energy Direct comes from the sound course Reverberant comes from sound bouncing off surfaces 5 What is the effect of the pinnae on sounds entering the ear Understand what the head related transfer function is describing The pinna funnels sound energy into the ear canal Better at funneling some frequencies more so than others Intensities of these frequencies change based on location of the sound HRTF head related transfer function Describes how the pinna ear canal head and torso change the intensity of sounds with different frequencies that arrive at each ear from a different location in space azimuth and elevation Into to Touch Anatomy and Physiology 1 What are are somatosensation and kinesthesis What are the types of kinesthetic receptors Where are they and what kind of info do they convey Somatosensation collective term for sensory signals from the body Touch pain temperature Kinesthesis perception of the position and movement of our limbs in space 2 What is haptic perception What is perception for action What is action for perception In the latter what types of exploratory procedures do we use to give us info about an object and what type of info do those procedures yield Haptic perception knowledge of the world that is derived from sensory receptors in skin muscles tendons and joints usually involving active exploration meaning touch relies on action to get info as opposed to vision or audio which are more passive Example of haptic perception For instance aligning the arrows and opening a child proof aspirin bottle in the dark Exploratory procedure feel an object to learn about it Perception for action grasp and manipulate objects in a stable coordinated manner to maintain proper balance and posture 3 If the skin is anesthetized but kinesthetic receptors are intact can you still grasp manipulate an object Why or why not the kinesthetic receptors work but the touch receptors don t subject can t maintain stable grasp on objects they must manipulate 4 What do you know about haptic search What features of an object that you are touching pop out and what features do not Compare that to vision Surface density and temperature You can detect before using selective attention to identify a particular feature preattentive feature detection Doesn t work for horizontal vs vertical lines Relies on material properties not object Opposite the visual system which is good at contours lines 5 Can we perceive patterns with the skin What are the limitations on this capability How does this capability compare to looking w blurred vision Can
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