by the patient. in addition, those patients who may be severely affected tend to fail in detecting their errors on visual inspection. extinction extinction is a phenomenon observable during double simultaneous stimulation of both left and right visual fields. patients with extinction will fail to perceive the stimulus in the contralesional visual field when presented in conjunction with a stimulus in the ipsilesional field. however, when presented on its own, patients can correctly perceive the contralesional stimulus. thus, patients with neglect fail to report stimuli present in the aberrant field, whereas patients with extinction fail to report stimuli in the aberrant field only when double simultaneous presentations occur in both hemifields. analogous to neglect, extinction affects the contralesional visuospatial field in majority of patients with unilateral damage. anatomical correlates of visuospatial neglect and extinction do not overlap absolutely, with extinction proposed to be associated with subcortical lesions. a common method in quick detection of visuospatial extinction is a finger confrontation model. utilized as standard bedside evaluation, the task requires the patient to indicate (either verbally or by pointing) in which visual field the doctor's hand or finger is moving, while the doctor makes a wiggling motion with his index. this enables the doctor to distinguish between deficits resembling neglect and those which may indicate extinction, by presenting either a single stimulus in the contralesional field or two simultaneous stimuli in both the contralesional and ipsilesional visual fields. this quick test can be used immediately in a hospital setting for quick diagnosis, and can be particularly useful following strokes and seizures. regions associated with impairment of visuospatial attention parietal damage the posterior parietal region is arguably the most extensively studied in relation to visuospatial attention. patients with parietal lobe damage most often fail to attend to stimuli located on the contralesional hemisphere, as seen in patients with hemineglect/unilateral visual neglect. as such, they may fail to acknowledge a person sitting to their left, they may neglect to eat food positioned on their left, or make head or eye movements to the left. computed tomography (ct) studies have demonstrated that the inferior parietal lobule in the right hemisphere is the most frequently damaged in patients with severe neglect. parietal damage may decrease the ability to reduce decision noise. spatial cues appear to reduce the uncertainty of a visuospatial decision. disruption to spatial orienting, as seen in hemineglect, suggests that patients with damage to the parietal region may experience an increased difficulty in decision-making regarding targets located in the contralesional field. damage to the parietal region may also increase illusory conjunctions of features. illusory conjunctions occur when people report combinations of features which did not occur. for example, when presented with an orange square and a purple circle, the participant may report a purple square or an orange circle. although it would typically require special circumstances for a non-impaired person to produce an illusory conjunction, it appears that some patients with damage to the parietal cortex may demonstrate a vulnerability to such visuospatial impairments. results from parietal patients suggest that the parietal cortex, and therefore spatial attention, may be implicated in solving this problem of binding features. frontal lobe damage lesions to the frontal cortices have long been known to precede spatial neglect and other visuospatial deficits. specifically, frontal lobe damage has been associated with a deficit in the control of over attention (the production of eye movements). lesions to the superior frontal lobe areas that include the frontal eye fields seem to disrupt some forms of overt eye movements. it has been demonstrated by guitton, buchtel, & douglas that eye movement directed away from an abruptly appearing visual target (“antisaccade”) is remarkably impaired in patients with damage to the frontal eye fields, who frequently made reflexive eye movements to the target. when frontal eye field patients did make antisaccades, they had increased latency of their eye movements compared to controls. this suggests that the frontal lobes, specifically the dorsolateral region containing the frontal eye fields, play an inhibitory role in preventing reflexive eye movements in overt attention control. further, the frontal eye fields or surrounding areas may be critically associated with neglect following dorsolateral frontal lesions. frontal lobe lesions also appear to produce deficits in visuospatial attention related to covert attention (the orienting of attention without the requirement eye movement). using posner's spatial cueing task, alivesatos and milner (1989; see ) found that participants with frontal lobe damage demonstrated a comparably smaller attentional benefit from the valid cues than control participants or participants with temporal lobe damage. voluntary orienting of frontal lobe patients appear to be impaired. the right lateral frontal lobe region was also found to be associated with left-sided visual neglect in an investigation carried out by husain & kennard. a region of overlap was found in the location of lesions in four of five patients with left-sided visual neglect, specifically the dorsal aspect of the inferior frontal gyrus and the underlying white matter. additionally, overlap of lesion areas was also detected in the dorsal region of brodmann area 44 (anterior to the premotor cortex). these results further implicate the frontal lobe in directing attention in visual space. thalamic nuclei damage (pulvinar nucleus) the thalamic nuclei have been speculated to be involved in directing attention to locations in visual space. specifically, the pulvinar nucleus appears to be implicated in the subcortical control of spatial attention, and lesions in this area can cause neglect. evidence suggests that the pulvinar nucleus of the thalamus might be responsible for engaging in spatial attention at a previously cued location. a study by rafal and posner found that patients who had acute pulvinar lesions were slower to detect a target which appeared in the contralesional visuospatial field compared to the appearance of a target in the ipsilesional field during a spatial cuing task. this suggests a deficit in the ability to use attention to improve performance in detection and processing of visual targets in the contralesional region. use in camouflage camouflage relies on deceiving the cognition of the observer, such as a predator. some camouflage mechanisms such as distractive markings likely function by competing for visual attention with stimuli that would give away the presence of the camouflaged object (such as a prey animal). such markings have to be conspicuous, and positioned away from the outline so as to avoid drawing attention to it, in contrast to disruptive markings which work best when in contact with the outline.