1. The point at which a stimulus first produces a sensation. 2. The lower limit of perception of a stimulus. 3. The minimal stimulus that produces excitation of any structure; e.g., the minimal stimulus eliciting a motor response. SYN: limen (2) [TA]. [A.S. therxold]
- absolute t. the lowest limit of any perception whatever. Cf.:differential t.. SYN: stimulus t..
- achromatic t. SYN: visual t..
- auditory t. the intensity of any barely perceptible sound.
- brightness difference t. the smallest difference that can be perceived as a difference in brightness. SYN: light difference (2).
- t. of consciousness the lowest point at which a stimulus sensation can be perceived.
- convulsant t. the smallest amount of stimulation, electric current, or drug required to induce a convulsion.
- differential t. the lowest limit at which two stimuli can be differentiated. SYN: t. differential.
- displacement t. the least distinguishable break in the contour of a line.
- double-point t. the least degree of separation of two points applied to the body surface that permits their being felt as two.
- erythema t. the dose at which erythema of the skin is produced by irradiation with ultraviolet, gamma, or x-rays.
- fibrillation t. least intensity of an electrical stimulus that will initiate fibrillation.
- galvanic t. SYN: rheobase.
- t. of island of Reil SYN: limen insulae.
- light differential t. the smallest difference in light intensity that can be appreciated.
- minimum light t. SYN: visual t..
- t. of nose SYN: limen nasi.
- pain t. the smallest intensity of a painful stimulus at which the subject perceives pain.
- phenotypic t. a quantitative genetic trait with a continuous distribution termed its liability; may generate two kinds of phenotype, according to whether the liability lies above or below some critical t. at about which a radical change in behavior occurs. For instance, blood uric acid level is a liability with an approximately gaussian distribution. At a critical point of chemical saturation (the t.), crystallization occurs and the resulting gout or nongout is a t. trait.
- relational t. the smallest degree of difference between two stimuli that permits them to be perceived as different.
- renal t. concentration of plasma substance above which the substance appears in the urine.
- speech awareness t. the lowest sound intensity at which speech can be detected. SYN: speech detection t..
- speech detection t. SYN: speech awareness t..
- speech reception t. the intensity at which speech is recognized as meaningful symbols; in speech audiometry, it is the decibel level at which 50% of spondee words can be repeated correctly by the subject.
- stimulus t. SYN: absolute t..
- swallowing t. 1. the moment that the act of swallowing begins after the mastication of food; 2. the critical moment of reflex action initiated by minimum stimulation, prior to the act of deglutition.
- visual t., t. of visual sensation the minimal light intensity evoking a visual sensation. SYN: achromatic t., minimum light t..

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thresh·old 'thresh-.(h)ōld n the point at which a physiological or psychological effect begins to be produced (as the degree of stimulation of a nerve which just produces a response or the concentration of sugar in the blood at which sugar just begins to pass the barrier of the kidneys and enter the urine) <below the \threshold of consciousness> <the \threshold of pain> <a high renal clearance \threshold> called also limen

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(in neurology) the point at which a stimulus begins to evoke a response, and therefore a measure of the sensitivity of a system under particular conditions. A thermoreceptor that responds to an increase in temperature of only two degrees is said to have a much lower threshold than one that will only respond to a change in temperature of ten degrees or more. In this example the threshold can be measured directly in terms of degrees.

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thresh·old (threshґōld) 1. the minimum level of input required to cause some event to occur. 2. limen; that value at which a stimulus just produces a sensation, is just appreciable, or comes just within the limits of perception; see also absolute t. and differential t. 3. renal t. 4. in anatomy, limen (def. 2).

Medical dictionary. 2011.

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  • threshold — [thresh′ōld΄, thresh′hōld΄] n. [ME threschwold < OE therscwold (akin to ON threskǫlder) < base of therscan (see THRASH) + ?] 1. DOORSILL 2. the entrance or beginning point of something [at the threshold of a new career] 3. Physiol. Psychol …   English World dictionary

  • Threshold — Thresh old, n. [OE. threswold, [thorn]reshwold, AS. [thorn]rescwald, [thorn]erscwald, [thorn]erscold, [thorn]rescold, fr. [thorn]rescan, [thorn]erscan, to thresh; akin to Icel. [thorn]reskj[ o]de, [thorn]r[ o]skuldr, Sw. tr[ o]skel, Dan.… …   The Collaborative International Dictionary of English

  • threshold — O.E. þrescold, þærscwold, þerxold doorsill, point of entering, first element related to O.E. þrescan (see THRESH (Cf. thresh)), with its original sense of tread, trample. Second element of unknown origin and much transformed in all the Germanic… …   Etymology dictionary

  • threshold — threshold. См. порог. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Threshold —   [englisch, θreʃəʊld; wörtlich »Schwelle«], an bestimmten Effektgeräten (Flanger, Limiter, Noisegate u. a.) einstellbarer Pegel (Schwellwert), bei dessen Erreichen der beabsichtigte Effekt ausgelöst wird …   Universal-Lexikon

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  • threshold — is spelt with one h (contrast withhold), and the h is optionally silent or aspirated in speech …   Modern English usage

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