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Society for Neuroscience
The Society for Neuroscience (SfN) is an international professional society for brain researchers, founded in Washington, D.C. in 1969, that runs a large annual meeting.
Society for Neuroscience Oral History Project
The Society for Neuroscience Oral History Project is an archival program of video interviews and written autobiographies of senior neuroscientists, conceived by Larry Squire during his 1993 to 1994 SfN presidency.
Soft palate
Soft palate (velum, palatum molle): mobile muscular posterior third of the palate ending in the uvula, with five muscles innervated by the vagus via the pharyngeal plexus except tensor veli palatini (V3); central to swallowing, speech, and sleep apnea.
Solitary nucleus
Solitary nucleus (nucleus tractus solitarii, NTS): dorsomedial medulla gray matter receiving visceral and taste afferents via cranial nerves VII, IX, X; first relay for baroreflex, respiration, and gut reflexes, using glutamatergic vagal input.
Somatic nervous system
Somatic nervous system (SoNS): PNS division for voluntary movement and sensory input via skeletal muscles; 12 cranial and 31 spinal nerve pairs, single-neuron efferent path releasing acetylcholine, distinct from the two-neuron autonomic system.
Somatomotor neuron
Somatomotor neuron (somatic motor neuron, CL:0005024) is a cholinergic, excitatory motor neuron innervating skeletal muscle, subdivided into alpha, beta, and gamma types, and distinct from visceromotor autonomic neurons.
Somatosensory system
Somatosensory system: the nervous system's network for touch, temperature, pain, and proprioception, carried by dorsal column-medial lemniscal and spinothalamic pathways to the somatosensory cortex.
Sorsby fundus dystrophy
Sorsby fundus dystrophy (Sorsby macular dystrophy, SFD) is a rare autosomal dominant retinal disease caused by TIMP3 mutations, causing macular atrophy and choroidal neovascularization with central vision loss from the fourth to fifth decade; anti-VEGF therapy helps if given early.
Sound localization
Sound localization: identifying a sound's direction and distance using interaural time and level differences plus pinna spectral (HRTF) cues; duplex theory, precedence effect, hearing-device limits, and animal comparisons.
Spatial audio
Spatial audio is a family of recording and playback techniques that let listeners perceive sound sources in three-dimensional space, most commonly on headphones using head-related transfer functions.
Spike-timing-dependent plasticity
Spike-timing-dependent plasticity (STDP), a Hebbian synaptic learning rule: pre-before-post spiking within roughly 10–100 ms windows drives LTP, reverse order drives LTD; found at over 20 synapse types from insects to humans.
Spinal cord
Spinal cord: the CNS cylinder of gray and white matter with 31 segments (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal), ascending sensory and descending motor tracts, reflex function, and regeneration failure after injury.
Spinal cord abscess
Spinal cord abscess: pus collection in or around the spinal cord, usually bacterial (staphylococcus) and often a complication of epidural abscess; rare, treated with surgery and IV antibiotics.
Spinal cord injury
Spinal cord injury (SCI): damage to the spinal cord from trauma or disease, causing complete or incomplete loss of movement, sensation, and autonomic function below the injury level; about 15.4 million people affected globally in 2021.
Spinal cord segments and vertebral levels
Spinal cord segments and vertebral levels do not align: the adult cord ends at L1–L2, so its 31 nerve segments sit higher than the vertebrae of the same name.
Spinal cord stimulator
Spinal cord stimulator (SCS): implanted epidural leads plus pulse generator treating chronic neuropathic pain refractory to medical management. Rooted in 1965 gate control theory; first implant 1967, Medtronic system 1968. Complications include infection and lead migration.
Spinal cord traction injury
A spinal cord traction injury is damage to the spinal cord caused by stretching rather than compression, occurring during spinal deformity surgery, delivery, or chronic tethered cord syndrome.
Spinal grey matter
Spinal gray matter is the central, butterfly- or H-shaped region of the spinal cord containing neuronal cell bodies, organized into ten Rexed laminae and surrounded by white matter.
Spinal muscular atrophy
Spinal muscular atrophy, historically called Werdnig-Hoffmann or Kugelberg-Welander disease, is a hereditary disease in which loss of spinal motor neurons causes progressive muscle weakness, treatable with drugs approved since 2016.
Spinal muscular atrophy with respiratory distress type 1
Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a rare genetic motor neuron disease that causes diaphragmatic paralysis and muscle weakness, typically in infants aged 6 weeks to 6 months.
Spinal nerve
Spinal nerve: one of 31 paired mixed nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal) formed by ventral and dorsal roots, exiting via intervertebral foramina as part of the peripheral nervous system.
Spinal stenosis
Spinal stenosis, narrowing of the spinal canal or nerve root spaces pressing on the spinal cord and nerves; most common in the lumbar and cervical spine, caused mainly by aging, with leg symptoms eased by flexion.
Spinocerebellar ataxia
Spinocerebellar ataxia (SCA): group of over 40 rare autosomal dominant neurodegenerative disorders causing cerebellar degeneration and progressive ataxia; SCA3 most common; no FDA-approved SCA drug.
Spinocerebellar ataxia type 19/22
Spinocerebellar ataxia type 19/22 (SCA19/22, ORPHA:98772) is a rare autosomal dominant cerebellar ataxia caused by KCND3 mutations encoding the Kv4.3 potassium channel, with slowly progressive ataxia, cognitive impairment, myoclonus, and tremor.
Spinocerebellar ataxia type 31
Spinocerebellar ataxia type 31 (SCA31) is an autosomal dominant neurodegenerative disease causing late-onset, slowly progressive cerebellar ataxia. Caused by a TGGAA repeat insertion on chromosome 16, it is Japan's third most common inherited ataxia.
Spinocerebellar ataxia type 6
Spinocerebellar ataxia type 6 (SCA6), an autosomal dominant ataxia from CAG repeat expansion in CACNA1A (Cav2.1 calcium channel), causing late-onset, slowly progressive pure cerebellar ataxia with nystagmus; slowest-progressing common SCA.
Spinothalamic tract
The spinothalamic tract, or spinal lemniscus, is a nerve fiber bundle that conveys sensations of pain, temperature, and crude touch from the spinal cord to the thalamus.
Spiral ganglion
The spiral ganglion is a group of sensory neurons in the cochlea of the inner ear that relays sound information from hair cells to the brainstem.
Split-brain
Split-brain: condition after corpus callosotomy, severing the corpus callosum to treat drug-resistant epilepsy. Studied by Sperry, Bogen, and Gazzaniga from the 1960s; classic left-hand/left-visual-field findings; debate over split versus unified consciousness.
Sporadic adult-onset ataxia of unknown etiology
Sporadic adult-onset ataxia of unknown etiology (SAOA, idiopathic late-onset cerebellar ataxia) is a rare non-hereditary degenerative ataxia beginning around age 50, with progressive gait ataxia, dysmetria, and dysarthria, differentiated from MSA-C and increasingly reclassified genetically (FGF14, RFC1).