- 1. A f.; a structure of definite shape or cellular arrangement. 2. That which is formed. 3. The act of giving form and shape. SYN: formatio (1) [TA].- concept f. in psychology, the learning to conceive and respond in terms of abstract ideas based upon an action or object.- personality f. the life history associated with the development of individual patterns and of one's individuality.- reaction f. in psychoanalysis, a postulated defense mechanism in which attitudes and behaviors that are adopted are the opposites of that which the individual would ordinarily be expected to express and actually feel at an unconscious level.- reticular f. (RF) a massive but vaguely delimited neural apparatus composed of closely intermingled gray and white matter and extending throughout the central core of the brainstem and into the diencephalon; the term refers to the large neuronal population of the brainstem that does not compose motoneuronal cell groups or cell groups forming part of specific sensory conduction systems; its neurons generally have long dendrites and heterogeneous afferent connections, the reason why the f. is often called “nonspecific”; the reticular f. has complex, largely polysynaptic ascending and descending connections that play a role in the central control of autonomic (respiration, blood pressure, thermoregulation, etc.) and endocrine functions, as well as in bodily posture, skeletomuscular reflex activity, and general behavioral states such as alertness and sleep. SYN: formatio reticularis [TA], reticular substance (2), substantia reticularis (2).- rouleaux f. the arrangement of red blood cells in fluid blood (or in diluted suspensions) with their biconcave surfaces in apposition, thereby forming groups that resemble stacks of coins. SYN: pseudoagglutination (2). [Fr. pl. of rouleau, a roll]
* * *for·ma·tion fȯr-'mā-shən n1) an act of giving form or shape to something or of taking form: DEVELOPMENT2) the manner in which a thing is formed: STRUCTURE
* * *for·ma·tion (for-maґshən) 1. the process of giving shape or form; the creation of an entity or of 2. a structure of definite shape. a structure of definite shape; see formatio.
Medical dictionary. 2011.