Child and Adolescent Brain Development: Motor Systems, Visual Pathways, and Perception

Vocabulary practice flashcards covering motor pathways, cortical and subcortical motor anatomy, movement disorders, and the neuroanatomy of the visual and facial perception systems.

Afferent Fibers

Nerve fibers that carry sensory nerve impulses toward the central nervous system (CNS), approaching the brain and affecting what you feel.

Efferent Fibers

Nerve fibers that carry motor nerve impulses away from the central nervous system (CNS) to muscles, exiting the brain and producing an effect on action.

Dorsal Column (Posterior Column)

The column of the spinal cord that contains ascending sensory fibers.

Ventral Column (Anterior Column)

The column of the spinal cord that contains descending motor fibers.

Cerebellum

Known as the 'Little Brain'; coordinates motor movement and posture, adapts movements to changing conditions, assists with timing and motor planning, and is organized ipsilaterally.

Basal Ganglia

A group of subcortical nuclei located deep beneath the cerebral cortex involved in the initiation and control of movement, consisting of the caudate nucleus, putamen, and globus pallidus.

Motor Fluency

The outcome of a circular experience of practice coupled with novel experience that produces complex, fluid, and accurate movements.

Motor Transfer

The process by which learned motor movements and retrieved motor memories are adapted, modified, and applied to acquire new motor skills.

Primary Motor Cortex (M1)

A strip of frontal lobe tissue located along the precentral gyrus that generates neural impulses to initiate and execute purposeful movements via contralateral, somatotopic organization.

Motor Homunculus

A somatotopic cortical mapping of the body where adjacent cortical areas correspond to adjacent body parts, disproportionately organized according to movement complexity.

Hemiplegia

The loss of voluntary movements on the contralateral side of the body (particularly in distal effectors like hands and fingers) and emergence of spasticity, frequently following a middle cerebral artery hemorrhage.

Supplementary Motor Area (SMA)

A motor structure located anterior to the primary motor cortex that helps organize and plan out the sequential steps of complex movements.

Orbital Prefrontal Cortex

A subdivision of the prefrontal cortex responsible for the executive control of social and emotional behavior, governing deliberate choices in social interactions.

Lateral Prefrontal Cortex

A subdivision of the prefrontal cortex that oversees the executive control of cognition, including attention, focus, planning, and working memory.

Medial Prefrontal Cortex

A subdivision of the prefrontal cortex dedicated to the executive control of motor behavior.

Cerebral Palsy (CP)

A non-progressive, heterogeneous group of movement, postural, and muscular disorders diagnosed in approximately $10{,}000$ infants each year in the United States.

Spastic Cerebral Palsy

A subtype of cerebral palsy marked by stiff muscles and spasticity, associated with damage to or developmental differences in the cerebral cortex.

Dyskinetic Cerebral Palsy

A subtype of cerebral palsy marked by uncontrollable movements (dyskinesia), associated with damage to the basal ganglia.

Ataxic Cerebral Palsy

A subtype of cerebral palsy marked by poor balance and coordination (ataxia), associated with damage to the cerebellum.

Multiple Sclerosis (MS)

A multifocal demyelinating disease affecting roughly $400{,}000$ people in the U.S. ($200$ diagnosed weekly) where sclerotic plaque lesions destroy myelin sheaths and disrupt nerve transmission.

Huntington’s Disease

An adult-onset, progressively disabling, and lethal genetic disorder affecting roughly $30{,}000$ Americans, characterized by choreiform movements and deterioration of the striatum/basal ganglia (especially the caudate nucleus).

Parkinson’s Disease

A neurodegenerative disease affecting approximately $1\text{ million}$ people in the U.S., caused by the loss of dopamine-producing cells in the substantia nigra, resulting in tremor, rigidity, bradykinesia, and postural instability.

Dopamine

A neurotransmitter synthesized in the substantia nigra; depletion results in Parkinson's disease, whereas excessive levels have been implicated in schizophrenia.

Hemifields

The right and left visual field halves of each eye; visual input from each hemifield is sorted at the optic chiasm to project contralaterally to the opposite hemisphere.

Optic Chiasm

The X-shaped commissure where optic nerve fibers from the nasal half of each retina decussate, ensuring that each cerebral hemisphere receives visual inputs from the contralateral visual space.

Superior Colliculus

A midbrain structure (optic tectum) receiving approximately $10\%$ of retinal projections (roughly $150{,}000$ neurons) that coordinates head and eye movements to orient toward peripheral visual stimuli.

Lateral Geniculate Nucleus (LGN)

A laminated sensory nucleus located in the dorsal thalamus that receives feed-forward input from optic tracts and $80\%$ feedback from V1, relaying signals to the visual cortex via optic radiations.

Calcarine Fissure

A prominent sulcus on the medial surface of the occipital lobe that divides the upper and lower halves of the visual field within the primary visual cortex.

Primary Visual Cortex (V1)

Striate cortex located in the occipital lobe containing an inverted, 2D topographic retinotopic map representing the contralateral visual field.

Cortical Magnification

The organizational feature of V1 where a disproportionately large area of cortical tissue is devoted to processing inputs from the fovea relative to the peripheral visual field.

Dorsal Stream ('Where' Pathway)

A higher-order visual processing pathway extending from V1 to the parieto-occipital association cortex, specialized for analyzing motion and spatial relationships between objects.

Ventral Stream ('What' Pathway)

A higher-order visual processing pathway extending from V1 to the occipitotemporal association cortex, specialized for analyzing object form, color, letters, and faces.

Prosopagnosia

A neurological condition termed 'face blindness' characterized by the inability to recognize familiar human faces, resulting from lesion or dysfunction within the fusiform face area (FFA).

Facial Inversion Effect

The disproportionate decrement in human facial recognition accuracy when faces are presented upside down compared to upright, an effect that is characteristically absent in individuals with autism spectrum disorder.