1,240 articles
Scleral buckle
Scleral buckle (scleral buckling): silicone explant sutured to the sclera to indent the eyewall and close retinal breaks in rhegmatogenous retinal detachment; introduced by Custodis in 1949, refined by Schepens and Lincoff, still used alone or with vitrectomy.
Semantic memory
Semantic memory: Tulving's 1972 memory system for general world knowledge, facts, and word meanings, distinct from episodic memory; hub-and-spoke ATL brain basis, K.C. and semantic dementia evidence.
Semaphorin
Semaphorins are a family of secreted and membrane proteins with a conserved Sema domain, first described in 1993 as axon guidance repellents; they signal via plexins and neuropilins and act in immunity, angiogenesis, and cancer.
Semicircular canals
Semicircular canals: three fluid-filled inner-ear loops (anterior, posterior, horizontal) sensing angular head acceleration via endolymph-cupula mechanics; basis of the VOR, Ewald's laws, BPPV, and vHIT/caloric testing.
Sense
A sense, also known as the five senses, is a biological system that detects stimuli through receptors and sends signals to the brain; humans have an estimated 22 to 33 senses.
Sensitization
Sensitization is a form of non-associative learning in which behavioral responses are amplified after an aversive or noxious stimulus, classically studied in the Aplysia gill- and siphon-withdrawal reflex.
Sensorineural hearing loss
Sensorineural hearing loss (SNHL): inner ear hearing loss from damaged cochlear hair cells or auditory nerve fibers, caused by aging, noise, ototoxic drugs, Ménière's disease, or genetics; permanent, managed with hearing aids, cochlear implants, and now OTOF gene therapy.
Sensory Feedback
Sensory feedback: a organism's own sensory-system information about a task, movement, or skill (MeSH Feedback, Sensory). Covers proprioceptive and cutaneous sources, spinal sensorimotor circuits, intrinsic versus augmented feedback in motor learning, and wearable haptic feedback devices.
Sensory nervous system
The sensory nervous system detects external and internal stimuli through receptors and relays them to the brain, generating touch, pain, vision, hearing, and other senses.
Sensory substitution
Sensory substitution delivers information from a lost sense (vision, hearing, balance) through another modality such as touch or sound; pioneered by Bach-y-Rita's 1969 TVSS, now including devices like BrainPort.
Sequelae of trachoma
Sequelae of trachoma: trachomatous conjunctival scarring, trichiasis, and corneal opacity following repeated Chlamydia trachomatis infection; WHO grading, entropion mechanism, surgery outcomes, and declining global burden.
Serotonergic neuron
Serotonergic neurons synthesize and release serotonin (5-HT) from hindbrain raphe nuclei (B1–B9 groups), about 0.015% of rat brain neurons, with TPH2/SERT/VMAT2 phenotype, rostrocaudal subtypes, and forebrain-to-spinal cord projections.
Serous retinal detachment
Serous retinal detachment (exudative retinal detachment, ICD-11 9B73.3): subretinal fluid separates the retina from the RPE without a break, caused by CSC, inflammation, tumors, or hypertension; treated medically.
Sexuality after spinal cord injury
Sexuality after spinal cord injury (SCI): how lesion level and completeness change arousal, erection, ejaculation, lubrication, orgasm, and fertility, plus assessment tools (IIEF, FSFI) and rehabilitation approaches.
SF268
SF268 (SF-268, CVCL_1689) is a human glioblastoma/astrocytoma cell line from the right parietal lobe, established in 1987, an NCI-60 CNS drug-screen line with homozygous TP53 p.Arg273His and a flagged Y-chromosome identity issue.
SF295
SF295 (SF-295, CVCL_1690) is a human glioblastoma cell line established at UCSF from a 67-year-old woman's left temporal lobe tumor; an NCI-60 CNS panel line with PTEN, TP53, and TERT promoter mutations.
Shaken baby syndrome
Shaken baby syndrome (SBS), renamed abusive head trauma (AHT) by the AAP in 2009, is a diagnosis attributing the infant triad of subdural hemorrhage, retinal hemorrhage, and encephalopathy to violent shaking; incidence 25–35 per 100,000 under age 1, fatal in about one quarter of cases, and scientifically contested.
Shepard tone
Shepard tone: auditory illusion by Roger Shepard (1964) of octave-spaced components under a fixed bell-shaped envelope, heard as endlessly rising or falling pitch; basis of the Risset glissando, tritone paradox, and film and game sound design.
Sixth nerve palsy
Sixth nerve palsy (abducens palsy, CN VI palsy): paralysis of the sixth cranial nerve causing esotropia and horizontal double vision worse at distance and toward the affected side; usually microvascular, about 80% recover.
Sleep
Sleep is a naturally recurring, reversible state of reduced responsiveness in which the brain cycles through REM and non-REM phases, regulated by circadian rhythms and sleep pressure.
Sleep cycle
Sleep cycle: the repeating NREM (stages 1-3) then REM sequence during sleep, about 80-100 minutes per cycle, four to six per night, deep sleep early and REM later; discovered 1953 by Aserinsky and Kleitman.
Sleep inertia
Sleep inertia: temporary grogginess, disorientation, and impaired performance immediately after waking, lasting 30-60 minutes typically; worst during circadian low and after deep sleep; managed with short naps, caffeine, and light.
Sleep paralysis
Sleep paralysis: temporary inability to move or speak while falling asleep or waking, caused by REM atonia persisting into wakefulness; affects about 8% of people, often with intruder or incubus hallucinations, and interpreted culturally as Pandafeche, kanashibari, or jinn attacks.
Sleep Stages
Sleep stages: the AASM's five human sleep states W, N1, N2, N3, and REM (stage R), scored from 30-second polysomnography epochs by EEG, EOG, and EMG patterns; N2 has spindles and K-complexes, N3 delta slow waves, REM atonia.
Slice preparation
Slice preparation: cutting 300–400 µm living brain sections for acute electrophysiology or long-term organotypic culture, from Harrison's 1907 explant to Stoppini's 1991 membrane-interface method, with ice-cold ACSF cutting and 6–12 hour acute viability.
Slow-wave sleep
Slow-wave sleep (SWS, deep sleep, stage N3) is the deepest NREM sleep stage, defined by high-amplitude 0.5–2 Hz delta waves on EEG, homeostatically regulated, central to memory consolidation, and reduced with aging.
Smell
Smell, or olfaction, is the chemical sense by which gaseous odorant molecules are detected and identified, mediated by the olfactory nerve and closely coupled to taste in flavor perception.
Smooth pursuit
Smooth pursuit: continuous eye movement tracking a slowly moving object to hold its image on the fovea; requires a moving target, has 100–125 ms latency, and involves MT/MST, FEF, cerebellum, and vestibular nucleus pathways.
Sneezing
Sneezing (sternutation): a protective airway reflex expelling nasal irritants via trigeminal nerve and brainstem NMB pathway; caused by allergies, infections, light; up to 40,000 droplets per sneeze.
Social neuroscience
Social neuroscience: interdisciplinary field studying neural, hormonal, cellular, and genetic mechanisms of social behavior; term coined early 1990s (Cacioppo and Berntson); distinct from the journal Social Neuroscience (2006).