Sensation, Perception, and Motor Control Vocabulary

Comprehensive vocabulary flashcards covering key concepts from Sensation & Perception I and Motor Control I & II lecture notes.

Sensation

The physical process of sensory receptors responding to external stimuli by receiving sensory information.

Perception

The organization, processing, and interpretation of sensory information that turns sensation into a meaningful experience.

Macula

An oval-shaped area of the retina important for central vision and detailed, color-rich sight that contains the fovea.

Retina

The layers of cells at the back of the eye that register light, send visual information toward the brain, and perform initial visual processing.

Rods vs. Cones Comparison

Rods process dim light for night vision without color in the periphery with high convergence (many to one ganglion); Cones process bright light for detailed, color vision in the fovea with low convergence (few to one ganglion).

Rods

Photoreceptors (approximately 120 million) sensitive to dim light and useful for nighttime peripheral vision, where many rods feed into one ganglion cell.

Cones

Densely packed photoreceptors (approximately 6 million) in the fovea sensitive to fine details and color across blue, green, and red wavelengths.

M cells (Magnocellular)

Large retinal ganglion cells that detect coarse visual patterns and rapid movement.

P cells (Parvocellular)

Smaller retinal ganglion cells that preserve color information and process finer visual details.

Receptive field

A specific region of visual space to which a particular cell responds, altering its firing rate based on stimulation within that area.

Center-surround receptive field

A ganglion cell organization (such as on-center/off-surround or off-center/on-surround) designed to enhance contrast and detect edges, borders, and light versus dark areas.

Geniculostriate pathway

The primary visual pathway carrying approximately 90% of optic nerve fibers, following the route: Retina -> Optic nerve -> Optic chiasm -> Optic tract -> LGN -> V1.

Nasal retina

The portion of the retina whose nerve fibers cross to the opposite hemisphere at the optic chiasm.

Temporal retina

The portion of the retina whose nerve fibers do not cross at the optic chiasm and stay on the same side.

Tectopulvinar pathway

A fast-acting visual pathway sensitive to motion and novel peripheral objects, projecting from Retina -> Superior colliculus -> Pulvinar nucleus of thalamus -> Cortical areas.

LGN (Lateral Geniculate Nucleus)

A thalamic visual relay nucleus consisting of six layers: Magnocellular (layers 1–2 for motion), Parvocellular (layers 3–6 for color/detail), and Koniocellular (between layers for spatial and primitive color processing).

Retinotopic organization

The mapping system in which spatial relationships in the visual field are preserved in nearby corresponding locations in the brain.

Primary Visual Cortex (V1)

Also called striate cortex; the primary cortical visual area that receives spatially organized projections from the LGN with distortion and inversion.

Cortical magnification

The allocation of a disproportionately large surface area of V1 to processing signals from the fovea compared to the peripheral retina.

Simple cells

Visual neurons in V1 that respond to bars of light at specific orientations and precise spatial locations.

Complex cells

Visual neurons in V1 that respond to particular line orientations but are less selective about the precise spatial location of the stimulus.

Hyper-complex cells

Visual neurons in V1 (also known as end-stopped cells) that prefer lines of particular orientations and specific lengths.

Ocular dominance columns

Vertical columns of cells in V1 that are driven primarily by input from either the left eye or the right eye.

Orientation columns

Vertical columns of cells in V1 tuned to respond to specific line orientations such as vertical, horizontal, or diagonal.

Hypercolumn

A complete functional unit in V1 combining ocular dominance and orientation columns tuned to stimulation at a particular spatial location.

Binocular disparity

The slight difference between the visual images received by each eye due to their position, used by the brain to calculate depth.

Stereopsis

Normal 3-D visual perception produced by the brain blending two slightly disparate images from each eye.

Voluntary movement

Intentionally initiated movement requiring brain and body coordination, such as reaching for a cup.

Involuntary movement

Automatic motor response occurring without intentional initiation, such as a knee-jerk reflex.

Neuromuscular junction

The specialized synapse between a motor neuron terminal button and skeletal muscle fibers.

Lateral corticospinal tract

A contralateral motor pathway crossing in the medulla that controls fine movements of distal muscles including arms, hands, fingers, lower leg, and foot.

Medial motor tract

A motor pathway projecting ipsilaterally and contralaterally to control posture, trunk, proximal limbs, neck, and bilateral movements.

Reflex

A rapid, automatic movement processed within the spinal cord without needing conscious brain input.

Vestibulocerebellum

A cerebellar division receiving input from vestibular nuclei that regulates balance and eye movements.

Spinocerebellum

A cerebellar division receiving somatosensory and kinesthetic input that controls muscle tone, smooth movement, and proximal muscles.

Cerebrocerebellum

A cerebellar division receiving cortical input that manages highly skilled movement and sensorimotor learning.

Dysmetria

A symptom of cerebellar damage characterized by overshooting or undershooting a movement endpoint.

Action tremor

Slow oscillatory movements occurring during a motor act, caused by cerebellar damage disrupting timing between agonist and antagonist muscles.

Agonist muscle

The primary muscle that contracts to produce a specific movement.

Antagonist muscle

The muscle that lengthens and relaxes during a movement to slow and stabilize action.

Forward Model Theory

The theoretical framework proposing that the cerebellum predicts sensory consequences of motor plans before feedback arrives and computes error signals to adjust future movements.

Ballistic movement

A rapid, pre-programmed movement executed too quickly for online feedback correction, such as throwing a ball.

Non-ballistic movement

A slower movement that can incorporate ongoing sensory feedback during execution, such as writing or drawing.

Dysmetria of Thought hypothesis

Schmahmann's proposal that the cerebellum functionally contributes to predicting and coordinating cognitive processes in addition to motor functions.

Basal ganglia

A group of subcortical nuclei (caudate nucleus, putamen, nucleus accumbens, globus pallidus, substantia nigra, subthalamic nucleus) responsible for selecting, initiating, sequencing, and regulating movement.

Direct pathway (Basal ganglia)

The basal ganglia circuit that facilitates and sustains ongoing motor activity ("Do it").

Indirect pathway (Basal ganglia)

The basal ganglia circuit that suppresses unwanted motor activity ("Don't do it").

Parkinson's disease

A neurodegenerative disorder resulting from loss of dopamine neurons in the substantia nigra, leading to indirect pathway overactivity, excessive movement suppression, resting tremors, slowness, and difficulty initiating movement.

Huntington's disease

A neurodegenerative disorder caused by loss of striatal neurons, resulting in underactive movement suppression ("brake failure"), excessive involuntary movements (chorea, dystonia), and cognitive/psychiatric symptoms.

Supplementary Motor Complex (SMC)

A cortical motor area involved in planning, preparing, initiating, sequencing actions, and creating overall abstract motor plans.

Premotor cortex

A cortical motor region (including PMd) that processes sensory cues to determine how an action should be performed.

Primary Motor Cortex (M1)

The cortical area that executes movement by sending command signals to motor neurons driving muscles.

Population vector

The combined firing activity across a group of M1 neurons tuned to preferred directions, which predicts the direction of an upcoming movement.

Anterior Cingulate Cortex (ACC)

A cortical region involved in evaluating action appropriateness, selecting responses, and exercising cognitive control when overriding established habits.

Inferior Frontal Gyrus (IFG)

A cortical area (specifically right IFG) associated with stopping, interrupting, or inhibiting motor actions.

Proprioception

Sensory information regarding the static position of body parts.

Kinesthesia

Sensory information regarding the active movement and motion of body parts.