Neuropsychology of Deafness Jill M. Plevinsky January 23, 2014
Neuropsychology of DeafnessJill M. PlevinskyJanuary 23, 2014
OutlineBrief 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
Anatomy and physiology of the ear and hearingThe 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.
Etiology of deafnessType 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
Age of onset of deafnessPrelingually 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
Causes of hearing loss in adultsOsteosclerosis
Meniere’s 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
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
fMRI findings• A) Regions in which poorer-hearing
listeners showed less language-driven brain activity
• B) Overlap of these regions defined probably primary auditory cortex
• C) Strongest cortical connectivity is to the prefrontal cortex, followed by premotor and temporal cortices
Causes of hearing loss in childrenOtitis media: inflammation in the middle ear
Congenital hearing lossAutosomal dominant hearing lossAutosomal recessive hearing lossX-linked hearing lossPrenatal infections, illnesses, and toxins
Meningitis
Acquired hearing loss Infections, ototoxic drugs, meningitis, measles, encephalitis, chicken pox,
influenza, mumps, head injury, noise exposure
Assessing deaf and hard of hearing individualsCommunication mode and test administration
Use of interpreters
Selection of appropriate tests and test usage
Demographic factors influencing test interpretation
Impact of deafness on neuropsychological performance30-40% 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 it’s assumed that their hearing devices compensate for their disability
Cognitive development in deaf childrenAcademic achievement
Reading development
Language development
Performance on standardized intelligence tests
Visual-spatial and memory skills
Conceptual development
Neuropsychological function
Cognitive development in deaf childrenAcademic achievement
Reading development
Language development
Performance on standardized intelligence tests
Visual-spatial and memory skills
Conceptual development
Neuropsychological function
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 doesn’t automatically translate to it’s eventual function
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
Neural and cortical plasticity associated with cochlear implantsThe 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
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
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
Insights into social cognitionDevelopmental 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
ReferencesAlberti, P.W. (2001). The anatomy and physiology of the ear and hearing. Evaluation, prevention, and
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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.
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References (cont.)Kral, A. & Eggermont, J.J. (2007). What’s to lose and what’s to learn: Development under auditory deprivation, cochlear implants and limits of cortical plasticity. Brain Research Reviews. 56, 259-269.
Kral, A. & Sharma, A. (2011). Developmental neuroplasticity after cochlear implantation. Trends in Neuroscience. 35, 111-122.
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