Question

Define visual extinction, and explain how attentional theories can explain visual extinction.

Answer 1

The word visual attention indicates the  set of cognitive operations that mediate the selection of relevant and the filtering out of irrelevant information from cluttered visual scenes.it actually involves mostly in the neuroscience in transmission of impulses  extinction is often taken as a cardinal sign indicating an attentional deficit.Patients with visual extinction can perceive a single stimulus in eitherof the hemispheres field if it is presented alone but are unaware of the same stimulus in the contralesional field when another is presented simultaneously on the ipsilesional side.Extinction is more frequent with right hemisphere damage and often persists after recovery from a more severe neglect disorder.

Extinction might leads to the result from sensory imbalance due to weakened or delayed inputs to the affected hemisphere rather than from attentional factors. After, the view that extinction and spatial neglect distributes a common underlying mechanism has been examined on the basis of a few patients with spatial neglect but no clinically noticeable extinction arise.Several observations were less support an attentional account of visual extinction, whereas physical characteristics of contralesional stimuli, such as increased brightness, size or duration, have less or no effect on detection,patients with damage to the parietal lobe are impaired in detecting a contralesional target in the absence of another competing target if their attention is invalidly cued to the ipsilesional field.Extinction is also influenced by expectancy as to where a stimulus is likely to occur based on the preceding stimulus contingencies,new quantitative ways of measuring attentional effects or deficits in visual processing

These findings are not entirely accounted for by current attentional theories that explain extinction by failure of the ability of the right hemisphere to control attention to both sides of space or release of the left hemisphere contraversive orienting bias . It is unclear were these models would assume different residual capacity or different hemispheric bias for orienting to contralesional stimuli when a task requires the reporting of location rather than number, or when there is a given shape star rather than another shape triangle in the right hemifield.in the field of neurowscience these methodology is used at different situations fro finding of brain funcdtions and transortation of information through impulses.