Neuroscience: Motor Control, Somatosensation, Audition, and Vision

Comprehensive vocabulary flashcards covering motor control, somatosensation and pain, audition, balance, chemical senses, and vision based on the NSC 3361 lecture materials.

Motor Plan

A set of muscle commands established before the action occurs.

Open-Loop Control

A control mechanism that optimizes speed with no guiding external feedback, producing rapid ballistic movements that are completed regardless of feedback.

Closed-Loop Control

A control mechanism that optimizes accuracy, where information from what is being controlled flows back to the controlling device to guide slower, sustained ramp movements.

Antagonist Muscles

Muscles that contract while opposing muscles extend (e.g., biceps flex while triceps extend).

Synergist Muscles

Muscles that act together to produce movement.

Fast-Twitch Muscle Fibers

Striated muscle fibers that contract rapidly, fatigue quickly, and are the last to be recruited.

Slow-Twitch Muscle Fibers

Striated muscle fibers that contract slowly, fatigue slowly, and are the first to be recruited.

Motor Unit

A single motoneuron axon and all of its target muscle fibers.

Muscle Spindle

A muscle proprioceptive receptor that responds to stretch and signals changes in muscle length.

Golgi Tendon Organ (GTO)

A muscle proprioceptive receptor sensitive to tension and contraction that inhibits motoneurons to prevent muscle from tearing away from bone.

Spasticity

Impaired control of the stretch reflex to the degree that it interferes with voluntary movements, resulting from hyperreflexia when cortical input to spinal reflexes is lost.

Supplementary Motor Area (SMA)

A nonprimary motor cortex region that loads and encodes movement sequences into the primary motor cortex and initiates sequences of movements.

Premotor Cortex

A region in the nonprimary motor cortex containing mirror neurons that plans ahead and fires just before an action is executed.

Purkinje Cells

Cerebellar cortex cells that regulate and guide motor actions through inhibition of movement.

Central Pattern Generator

A neural circuit within the spinal cord that produces rhythmic behaviors such as walking and breathing.

Myasthenia Gravis (MG)

An autoimmune disorder characterized by antibodies attacking nicotinic acetylcholine (ACh) receptors, leading to progressive skeletal muscle weakness throughout the day.

Amyotrophic Lateral Sclerosis (ALS)

A pyramidal disorder (Lou Gehrig's Disease) marked by motoneuron degeneration, individual motor unit fasciculations, and fatal loss of respiratory muscle function.

Ataxia

An extrapyramidal motor impairment marked by loss of balance resembling drunkenness, resulting from cerebellar damage such as cerebellar vermis tumors or alcohol-induced Purkinje cell loss.

Parkinson's Disease (PD)

An extrapyramidal movement disorder characterized by tremors, bradykinesia, shuffling gait, and postural instability, caused by loss of dopamine cells in the substantia nigra or defects in the $\alpha$-synuclein gene.

Chorea

Involuntary, dance-like movements of the arms and hands, prominently seen in Huntington's disease.

Apraxia

An extrapyramidal disorder characterized by an inability to sequence movements properly without muscle paralysis.

Range Fractionation

The sensory coding phenomenon wherein different sensory cells exhibit different firing thresholds across a broad spectrum of stimulus intensities.

Merkel's Disc

A slow-adapting, tonic, superficial somatosensory receptor involved in precise sustained touch.

Meissner's Corpuscle

A fast-adapting, phasic, superficial somatosensory receptor involved in precise burst touch and perception of texture.

Pacinian Corpuscle

A deep, mechanically gated somatosensory receptor that detects vibration and deep pressure.

Ruffini's Corpuscle

A deep, slow-adapting somatosensory receptor that detects skin stretch and tension.

C Fibers

Small, unmyelinated nerve fibers with slow conduction velocity that transmit dull pain.

A-Delta ($A\text{-}\Delta$) Fibers

Large, myelinated nerve fibers with fast conduction velocity that transmit sharp pain.

Dorsal Column-Medial Lemniscal Pathway

The somatosensory pathway responsible for transmitting fine touch, vibration, and proprioception to the brain.

Spinothalamic Pathway

The tactile and ascending sensory system responsible for carrying pain and temperature information to the thalamus.

Periaqueductal Gray (PAG)

A midbrain region abundant in opioid receptors that mediates pain perception and descending pain suppression.

Gate Control Theory of Pain

A theory proposing that spinal transmission of pain can be closed or inhibited by increased activity in large sensory $A$ fibers ($A\text{-}\alpha$ and $A\text{-}\beta$).

Reflex Sympathetic Dystrophy (RSD)

A neurogenic chronic pain condition marked by progressive diffuse pain, swelling, and abnormal dendrite remodeling where light touch stimuli are perceived as painful.

Cingulate Cortex

The cortical region where pain is processed emotionally, showing increased activity as the unpleasantness of pain escalates.

Fourier Analysis

The mathematical decomposition of complex acoustic waveforms into their individual constituent sine waves.

Organ of Corti

The inner ear structure located on the basilar membrane containing hair cells that push against the tectorial membrane to transduce sound vibrations.

Tip Links

Filamentous structures linking the tops of stereocilia that sway in response to sound vibrations, opening ion channels to depolarize hair cells.

Tonotopic Organization

The spatial arrangement of auditory processing structures wherein neurons are ordered systematically by sound frequency ('high in the back, high inside').

Frequency Theory

An auditory theory stating that sound pitch is represented by the firing rate of auditory neurons, operating primarily for low frequencies up to $1000\text{ Hz}$.

Volley Principle

An auditory encoding mechanism for intermediate frequencies ($1000 - 5000\text{ Hz}$) where groups of neurons work together by alternating firing to code the entire sound wave.

Place Theory

A pitch perception theory stating that sound frequency is determined by the point of maximum vibration along the basilar membrane, dominant for high frequencies above $5000\text{ Hz}$.

Medial Superior Olive (MSO)

A brainstem sound localization nucleus functioning as a coincidence detector that computes interaural differences in time/latency for low-frequency sounds.

Lateral Superior Olive (LSO)

A brainstem sound localization nucleus that computes interaural differences in sound intensity/loudness for high-frequency sounds.

Pure Word Deafness

A form of central auditory impairment characterized by an inability to understand spoken verbal language despite preserved speech production and intact comprehension of nonverbal sounds.

Auditory Agnosia

A central auditory disorder where an individual can hear pure tones normally but cannot recognize either verbal or nonverbal sounds.

Tinnitus

A persistent ringing sensation in the ears caused by cochlear and central nervous system damage where outer hair cells increase signal amplification following inner hair cell death.

Accommodation

The optical process in which ciliary muscles alter the curvature of the lens to focus near or far images on the retina.

Rhodopsin

The photopigment located in rod photoreceptors consisting of opsin and retinal that initiates visual phototransduction.

Blindsight

The unconscious ability of individuals with damaged primary visual cortex ($V1$) to locate or point to visual stimuli through intact extrastriate pathways to $V2$ and $V5$.

Magnocellular Cells (M-Cells)

Large ganglion cells in the LGN constituting the 'where' pathway that project to the dorsolateral parietotemporal cortex to analyze object motion, location, and brightness contrast without color sensitivity.

Parvocellular Cells (P-Cells)

Small ganglion cells in the LGN constituting the 'what' pathway that project to the inferior occipitotemporal cortex ($V4$) to analyze object shape and fine spatial details.

Koniocellular Cells (K-Cells)

Small neurons in the blob channel of the LGN specialized for color analysis.

Visual Area V4

An extrastriate visual cortical area responsible for color perception and the processing of complex circular, concentric, and radial shapes.

Visual Area V5

The extrastriate visual cortical region specialized for motion detection; bilateral lesions result in akinetopsia (motion blindness).

Opponent-Process Hypothesis

A color vision theory stating that color is coded along three antagonistic axes whose fatiguing relieves reciprocal inhibition and generates afterimages.

Simultagnosia

A visual deficit resulting from inferotemporal cortex dysfunction characterized by an inability to perceive a visual scene as a cohesive whole.

Palinopsia

A visual perceptual disorder where afterimages or visual trails persist after a stimulus has passed, caused by damage affecting $V5$ in bilateral occipital and middle cortices.

Optic Ataxia / Visual Agnosia

A neurological condition marked by the inability to identify objects visually or use visual information to guide hand movements toward them, despite normal tactile identification.