Question

What is simultanagnosia? What brain damage is often associated with it, and what evidence is there that it is a disorder of selective attention?

Answer 1

Simultanagnosia (or simultagnosia) is a rare neurological disorder characterized by the failure of a person to see in excess of a solitary article at any given moment. This sort of visual attention issue is one of three noteworthy segments (the others being optic ataxia and optic apraxia) of Bálint's syndrome, an unprecedented and deficiently comprehended assortment of serious neuropsychological hindrances including space portrayal (visuospatial preparing).
Simultanagnosia can be isolated into two unique classes: dorsal and ventral. Ventral occipito-worldly sores cause a mellow type of the turmoil, while dorsal occipito-parietal sores cause a progressively extreme type of the confusion.
Patients with simultanagnosia, a segment of Bálint's syndrome, have a confined spatial window of visual attention and can't see more than one article at any given moment in a scene that contains more than one item. For example, whenever gave a picture of a table containing both nourishment and different utensils, a patient will report seeing just a single thing, for example, a spoon. On the off chance that the patient's attention is diverted to another item in the scene, for example, a glass, the patient will report that they see the glass yet never again observe the spoon. Because of this disability, simultanagnosic patients frequently neglect to fathom the general significance of a scene.
Also, patients note that one stationary article may precipitously vanish from view as they become mindful of another item in the scene.
Simultanagnosic patients frequently display a marvel known as "local capture" where they just recognize the local components of stimuli containing local and worldwide highlights. In any case, ongoing investigations have shown that understood preparing of the worldwide structure can happen. With the suitable upgrade conditions, unequivocal preparing of the worldwide structure may occur. For model, an investigation performed with Navon progressive letters, which are enormous letters made out of littler ones, uncovered that the utilization of littler and denser Navon letters one-sided the patient towards worldwide handling.
In 1909, Rezső Bálint published probably the soonest portrayal of simultanagnosia. He contemplated a patient who effectively distinguished single articles, paying little mind to measure, however asserted that he could possibly observe one article when given an intricate showcase of various things. This patient likewise showed ocular apraxia, an impedance of willful eye developments regardless of unblemished oculomotor reflexes, and optic ataxia, or the debilitation of visually guided hand developments. This gathering of manifestations would later be called Bálint's syndrome. Since the size of the article did not influence his patient's capacity to see a thing, Bálint contended that his patient did not have a narrowing of the tangible field. Thusly, Bálint reasoned that the patient's attention would consistently be as restricted as the size of the thing being observed.In different words, the attentional window of a simultanagnosic patient is constrained to one article.
As opposed to Bálint's theory, Thaiss and De Bleser examined a patient who had a physical confinement of her attentional window. The patient's capacity to see different articles and recognize worldwide structures altogether improved as the size of the introduced picture decreased.Thus, complex stimuli could be handled as wholes inasmuch as they involved a little visual edge.