- 1.Neuropsychology of Deafness Jill M. Plevinsky January 23, 2014
2. Outline Brief etiology of deafness Neuropsychological assessment of deaf persons Developmental and cognitive implications of deafness Neural and cortical plasticity associated with sensory loss Neural and cortical plasticity associated with cochlear implants Neurobiology of sign language Social cognitive neuroscience insights from deafness 3. Anatomy and physiology of the ear and hearing The pinna and external auditory canal form the outer ear, which is separated from the middle ear by the tympanic membrane. The middle ear houses three ossicles, the maleus, incus and stapes and is connected to the back of the nose by the Eustachian tube. Together they form the sound conducting mechanism. The inner ear consists of the cochlea which transduces vibration to a nervous impulse and the vestibular labyrinth which houses the organ of balance. 4. Etiology of deafness Type of hearing loss depends on where in the ear the problem occurs Three basic types: Conductive hearing loss Occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the ossicles of the middle ear Sensorineural hearing loss (SNHL) Occurs when there is damage to the inner ear (cochlea), or to the nerve pathways from the inner ear to the brain Mixed hearing loss Sometimes occurs in combination with SNHL, damage to the outer or middle ear and the inner ear or auditory nerve 5. Age of onset of deafness Prelingually deaf 95% of all deaf children are prelingually deaf May be capable of oral communication, but usually develop these skills much later than they developmentally should Postlingually deaf Many retain their ability to use speech and communicate with others orally 6. Causes of hearing loss in adults Osteosclerosis Menieres disease Autoimmune inner ear disease Very loud noise Acoustic neuroma Physical head injury Presbycusis Ototoxic medications Aminoglycoside antibiotics, salicylates (aspirin) in large quantities, loop diuretics, drugs used in chemotherapy regimens 7. Hearing loss in older adults Hearing loss is one of the most common complaints in adults over the age of 60 Individual differences in hearing ability predicted the degree of language-driven neural activity during comprehension Linear relationship between hearing ability and gray matter volume in the primary auditory cortex Declines in auditory ability lead to a decrease of neural activity during processing of higher-level speech, and may contribute to loss of gray matter volume in the primary auditory cortex 8. fMRI findings A) Regions in which poorer-hearing listeners showed less language-driven brain activityB) Overlap of these regions defined probably primary auditory cortexC) Strongest cortical connectivity is to the prefrontal cortex, followed by premotor and temporal cortices 9. Causes of hearing loss in children Otitis media: inflammation in the middle ear Congenital hearing loss Autosomal dominant hearing loss Autosomal recessive hearing loss X-linked hearing loss Prenatal infections, illnesses, and toxins Meningitis Acquired hearing loss Infections, ototoxic drugs, meningitis, measles, encephalitis, chicken pox, influenza, mumps, head injury, noise exposure 10. Assessing deaf and hard of hearing individuals Communication mode and test administration Use of interpreters Selection of appropriate tests and test usage Demographic factors influencing test interpretation 11. Impact of deafness on neuropsychological performance 30-40% of those who are deaf or hard of hearing have additional disabilities resulting from the same condition, disease, or accident that caused the hearing loss Those with mild-moderate hearing loss are sometimes overlooked when it comes to other special needs because its assumed that their hearing devices compensate for their disability 12. Cognitive development in deaf children Academic achievement Reading development Language development Performance on standardized intelligence tests Visual-spatial and memory skills Conceptual development Neuropsychological function 13. Cognitive development in deaf children Academic achievement Reading development Language development Performance on standardized intelligence tests Visual-spatial and memory skills Conceptual development Neuropsychological function 14. Neural and cortical plasticity associated with sensory loss The process of developing a functional auditory system is affected significantly by sensory deprivation Sensory deprivation is associated with cross-modal neuroplastic changes in the brain Deaf individuals show superior skills in perceptual tasks Exact mechanisms of cross-modal plasticity and neural basis of behavioral compensation are largely unknown Not all neuroplastic changes represent behavioral gains and the restoration of a deprived sense doesnt automatically translate to its eventual function 15. Cochlear implantation Surgically implanted devices providing a sense of sound Cochlear implants bypass damage to sensory hair cells in the cochlea by directly stimulating the auditory nerve and brain Candidates have to have severe-profound sensorineural hearing loss in both ears, a functioning auditory nerve, realistic expectations of results, support of family/friends 16. Neural and cortical plasticity associated with cochlear implants The optimal time to implant a young congenitally deaf child with a unilateral cochlear implant is within the first 3.5 years of life when the central pathways show maximal plasticity Neuronal mechanisms underlying sensitive periods for cochlear implantation Delays in synaptogenesis Deficits in higher order cortical development Cross-modal recruitment 17. Consequences of long-term auditory deprivation a) Deaf children who receive a cochlear implant at 7 y.o. show abnormal cortical auditory evoked potentials and a lack of top-down modulation of incoming auditory stimuli b) Long-term deafness beyond the critical period results in cross-modal cortical reorganization c) Auditory deprivation can result in deficits in processing of multimodal stimulation necessary for language learning 18. Neurobiology of sign language Distinctions between spoken language (SpL) and sign language (SL) Neural systems supporting signed and spoken language are very similar both involve a predominately left-lateralized perisylvian network The use of space in SL The role of the parietal cortex in SL processing The role of face and mouth in SL processing 19. Insights into social cognition Developmental pathways for sociocognitive process are influenced by complex interaction effects of early temperament predispositions, socialization processes, relationship, and culture Visual attention Impulsivity and distractibility High-level visual processing Facial expressions Human actions Language and communication Theory of mind 20. References Alberti, P.W. (2001). The anatomy and physiology of the ear and hearing. Evaluation, prevention, and control. (pp. 53-62). http://www.who.int/occupational_health/publications/noise2.pdf Calderon, R. (1998). Learning disability, neuropsychology, and deaf youth: Theory, research, and practice. Journal of Deaf Studies. 3, 1-3. Corina, D. & Knapp, H. (2006). Sign language processing and the mirror neuron system. Cortex. 42, 529-539. Corina, D. & Singleton, J. (2009). Developmental social cognitive neuroscience: Insights from deafness. Child Development. 80, 952-967. Hill-Briggs, F., Dial, J.G., Morere, D.A., & Joyce, A. (2007). Neuropsychological assessment of persons with physical disability, visual impairment or blindness, and hearing impairment or deafness. Archives of Clinical Neuropsychology. 22, 389-404. Knapp, H.P. & Corina, D.P. (2010). A human mirror neuron system for language: Perspectives from signed languages of the deaf. Brain & Language. 112, 36-43. 21. References (cont.) Kral, A. & Eggermont, J.J. (2007). Whats to lose and whats to learn: Development under auditory deprivation, cochlear implants and limits of cortical plasticity. Brain Research Reviews. 56, 259-269. 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Cortical development, plasticity and re-organization in children with cochlear implants. Journal of Communication Disorders. 42, 272-279.