Cortical Map and Plasticity

American; detailed “brain maps in various sensory systems”; cortical plasticity; helped engineer a version of cochlear implant; FastForWord and Posit Science

Canadian; mapped sensory and motor areas of patients; sensory and motor cortex topographically organized; stimulation of other areas of cortex triggered; one of the originators of the “homunculus”

separates motor cortex and sensory cortex

decisions to move

information from body is received

“little man”; primary somatosensory cortex and primary motor cortex are topographically organized

discovered functional organization of cerebral cortex

all neurons in a vertical cross section of cortex respond to the same sensory signal; neurons are organized in six layers; neurons of a cortical column respond together

• co- Nobel prize laureates 1981

• famous for discoveries outlining the neuronal processing that occurs within the visual cortex

  • determined critical period for visual information from each eye to map onto cerebral cortex

temporal windows during development in which environmental factors influence the formation of synaptic connection and circuit function

• sew right eye of kitten shut during first year of life

  • pattern of ocular dominance columns was altered: neurons in columns that would normally respond to right eye respond to left eye

critical period in animal behavior; imprinting with geese

• mapped cortical area in somatosensory cortex of fingers of monkey

• “use it or lose it” - mapped sensory cortex before and after manipulation of digit 3

  • map for digit 3 disappears and other maps move into the cortical real estate

• “neurons that fire together wire together” - merged two fingers so they respond two the same sensory information

  • cortical maps for digits 3 and 4 merged to form a single map

  • now touching a single point on either of the sewn fingers stimulates the map

change in pressure of air

sound hits eardrum/tympanic membrane which is connected to ossicles (malleus, incus, stapes); auditory system

send information to brain

where sensory information is located [inner ear]

fluid that fills the vestibular and tympanic duct

fluid that fills the cochlear duct (scala media)

tectorial membrane

hair cells

basilar membrane

products movement of perilymph, which in turn products movement of endolymph

where sound is sensed

contains neurons, sends information to hair cells

sensory neurons of the inner ear, located in organ of corti

• stretch-activated channels activate

• depolarization of hair cells

• K+ enters

• Ca+2 voltage-gated channels activated

• neurotransmitters released into synapse

  • sufficient activity hits threshold >> action potential

topographically; high frequencies near base and low frequencies near apex

conductive and sensorineural

damage in outer or middle ear

damage in inner ear (most commonly, hair cells)

treatment option for people with severe to profound sensorineural hearing loss; small, complex, electronic device that can help to provide a sense of sound

electrodes inserted in cochlea, electrodes stimulated by microphone, which stimulates neurons; electrical impulses stimulate dendrites of acoustic neurons