- An inability to recognize sensory inputs (sight, sound, touch). The most common agnosia is a result of brain injury damaging the rear part of the brain causing visual agnosia (inability to properly recognize objects by sight).
* * *Impairment of ability to recognize, or comprehend the meaning of, various sensory stimuli, not attributable to disorders of the primary receptors or general intellect; agnosias are receptive defects caused by lesions in various portions of the cerebrum. SYN: agnea. [G. ignorance; from a- priv. + gnosis, knowledge]- auditory a. inability to recognize sounds, words, or music; caused by a lesion of the auditory cortex of the temporal lobe.- color a. inability to name or identify specific colors by sight; caused by lesions of the dominant occipital and temporal lobes.- finger a. inability to name or recognize individual fingers, of one's own or of other persons; most often caused by lesion of or near the angular gyrus of the dominant hemisphere.- gustatory a. inability to classify or identify a tastant, even though the ability to distinguish between or recognize tastants may be normal; may be general, partial, or specific.- olfactory a. inability to classify or identify an odorant, although the ability to distinguish between or recognize odorants may be normal; may be general, partial, or specific.- optic a. SYN: visual a..- tactile a. inability to recognize objects by touch, in the presence of intact cutaneous and proprioceptive hand sensation; caused by a lesion in the contralateral parietal lobe. SYN: astereognosis, stereoagnosis, stereoanesthesia.- visual a. inability to recognize objects by sight; usually caused by bilateral parieto-occipital lesions. SYN: optic a..- visual-spatial a. inability to localize objects or to appreciate distance, motion, and spatial relationships; caused by lesion in the occipital lobe. Cf.:simultanagnosia.
* * *ag·no·sia ag-'nō-zhə, -shə n loss or diminution of the ability to recognize familiar objects or stimuli usu. as a result of brain damage see visual agnosia
* * *n.a disorder of the brain whereby the patient cannot interpret sensations correctly although the sense organs and nerves conducting sensation to the brain are functioning normally. It is due to a disorder of the association area in the parietal lobes. In auditory agnosia the patient can hear but cannot interpret sounds (including speech). A patient with tactile agnosia (astereognosis) retains normal sensation in his hands but cannot recognize three-dimensional objects by touch alone. In visual agnosia the patient can see but cannot interpret symbols, including letters (see alexia).
* * *ag·no·sia (ag-noґzhə) [a-1 + gnosia] loss of the power to recognize the import of sensory stimuli; the varieties correspond with the several senses and are distinguished as auditory, visual, olfactory, gustatory, and tactile.
Medical dictionary. 2011.