microstereognosia

   Also known as microstereognosis. Both terms stem from the Greek adjective mikros (small), and the medical term stereognosis (from the Greek words stereos (solid, tight, compact) and gnosis (insight)), meaning the ability to identify solid objects through the tactile sensation. The term microstereognosia was introduced in or shortly before 1945 by the Jewish neurologist Lipman Halpern to denote a tactile *illusion in which an object (held in the palm of one's hand, for example) appears to be significantly smaller than it is. The term is used in opposition to *macrostereognosia. Pathophysiologi-cally, both conditions are associated primarily with thalamic dysfunction, and with mild parietal sensory impairment. Conceptually, microstereognosia may be seen as the tactile equivalent of *micropsia (i.e. seeing things as smaller than they are). The two conditions have also been known to occur in conjunction with one another.

   References

   Critchley, M. (1953). The parietal lobes. London: Edward Arnold & Co.

   Halpern, L. (1945). Macrostereognosia. An unusual phenomenon in a case of thalamic syndrome. Journal of Nervous and Mental Disease, 102, 260-264.

   Halpern, L. (1959). Simultaneous visual and tactile illusions of size. Confinia Neurologica, 19, 301-306.