Agnosia: Definition, clinical contexts, neurobiological profiles and clinical treatments

Abstract

a disturbance of perception characterized by the lack of recognition of objects, people, sounds, shapes, smells already known, in the absence of memory disturbances and the absence of system lesions elementary sensory. It can occur separately about each of the fi ve senses and for each sense different types of agnosia can be found; in essence, the person suffering from agnosia can use a fork instead of a spoon thinking that they have chosen the spoon, or a shoe instead of a cup or a penknife instead of the pencil [1]. The fi rst cognitive operational model on object recognition was developed by the German neurologist Lissauer, in 1890, who hypothesized that this recognition occurred on two consequential levels of analysis [2]. At the fi rst level (perceptual level) the integration of elementary sensory data takes place in complex forms; At the second level (associative) there is a comparison between what is perceived and the knowledge stored in memory. This model, although still extremely valid today, other extremely valid models have been proposed, based on more in-depth theories regarding the various levels of stimulus processing, especially about visual perception. It often involves damage to the areas of the primary visual cortex and the associative areas via the what and via the where; not surprisingly, a defi cit of the fi rst level involves an apperceptive agnosia, while a defi cit of the second level leads to associative agnosia. Therefore, starting from the sensory data, as a product of stimulation and receptor reactivity, through the fi ve senses (sight, hearing, smell, touch, and taste), we arrive at perception, such as the elaboration of the elementary sensation that reaches the sense organ [2]. Thanks to the studies of Weber (on the diff erential threshold or threshold of relevance of the perceived stimulus) and Fechner (on the sensation, directly proportional to the logarithm of the intensity of the stimulus), we came to say that [2]: 1) The thesis that supported "sensation = perception" (naive realism) is incorrect, while the hypothesis that foresees the analytical difference (critical realism) is correct; 2) Only the stimuli to which the sense organ is sensitive are perceived; 3) The stimulus, to be registered by the sense organ, must be suffi ciently intense, in an absolute sense. Abstract Starting from the general concept of Agnosia, the present work focuses on the clinical, neurobiological, and functional aspects of the morbid condition, suggesting a multidimensional treatment between rehabilitation exercises for lost skills and psychotherapy.