Neuroplasticity, Cortical Maps, and Sensory Substitution Lecture Notes

A set of vocabulary flashcards covering key concepts of neuroplasticity, cortical mapping, somatosensory pathways, and sensory substitution mechanisms.

Adaptive Myelination

A process where oligodendrocyte progenitor cells differentiate and wrap axon segments in response to experience.

Rosenzweig's Environmental Enrichment Study

Research showing that experience shapes brain anatomy, demonstrated by rats housed in isolation having thinner dendrites and fewer synapses than rats raised in enriched group environments.

Apoptosis

Programmed cell death that is regressive yet essential for normal formation during prenatal brain development.

Hemispheric Isolation (Arrowsmith Exercise)

The practice of wearing an eye patch during cognitive training to isolate input to one hemisphere and force the use of the weaker side.

Sensitive Periods

Windows of rapid development during which brains are more modifiable, meaning early exposure before age $7$ to languages, music, or motor skills has a greater impact than starting at age $15$.

Wernicke's Aphasia

A condition characterized by fluent but meaningless speech with semantic errors, such as saying '…word-things not coming right… fluffy running green telephone.'

Hebb's Rule (Synaptic Weakening)

The principle stating that a synapse weakens when the presynaptic neuron fires, but the postsynaptic neuron does not fire at the same time.

"Use It or Lose It"

A neuroplasticity concept explaining that neural pathways weaken after extended disuse, such as a pianist's motor sequence synapses after a year of tendinitis.

Premotor Cortex

The cortical area that plans movement, whose neural activity temporally precedes the primary motor cortex during movement execution.

Sensory Transduction

The process wherein receptor cells convert energies from our environment into electrical energy in the form of action potentials.

Experience-Dependent Plasticity

Cortical reorganization driven by localized use, such as a long-time violinist developing an enlarged S1 representation for the string-pressing fingertips of the left hand.

Cortical Column

A vertical cortical slice where all constituent neurons respond to the same stimulus or body region.

Somatosensory Homunculus Over-Representation

The disproportionate allocation of cortical space to regions like the hands and face due to higher receptor density at the skin surface.

Barrel Cortex

The whisker-related cortical territory that is enlarged in blind mole rats, showing that cortical space reflects behavioral importance and experience-dependent use.

Medulla

The first site in the somatosensory pathway where dorsal root ganglion neurons carry incoming touch information.

Merzenich's Amputation Experiment

A study demonstrating that when digit $3$ is amputated in monkeys, its S1 cortical territory disappears, and sensory processing from adjacent digits ($2$ and $4$) expands into the vacated space.

Cochlear Implant Base Electrodes

Electrodes positioned near the base of the cochlea that primarily activate high frequencies, aligning with how natural base hair cells respond.

Tracts

Bundles of axons situated within the central nervous system (CNS), functioning as the equivalent of nerves in the peripheral nervous system (PNS).

Axon Collaterals

Axon branches whose growth cones follow trophic gradients to form synapses with nearby intact inputs, driving cortical map reorganization after injury.

Tongue (Sensory Substitution)

A tactile site preferred over the back for Bach-y-Rita's devices because its high mechanoreceptor density provides superior spatial resolution of touch information.

Stereocilia Deflection Away from Tallest Cilium

Hair cell displacement that closes mechanically-gated channels, hyperpolarizes the hair cell, and drops neurotransmitter release.

Cochlear Base Damage

Sensorineural hair cell damage located at the base of the cochlea, typically caused by loud machinery and resulting in high-frequency hearing loss above $4{,}000\,\text{Hz}$.

Residual Effect

The prolonged balance stability experienced by Cheryl Schiltz following sensory substitution therapy, likely driven by Hebbian plasticity enabling the remaining $2\%$ of functional vestibular hair cells to strengthen connections.