Extinction is a neurological disorder that impairs the ability to perceive multiple stimuli of the same type simultaneously. Extinction is usually caused by damage resulting in lesions on one side of the brain. Those who are affected by extinction have a lack of awareness in the contralesional side of space (towards the left side space following a right lesion) and a loss of exploratory search and other actions normally directed toward that side. Effect of the laterality of the sensory inputs Unilateral lesions of various brain structures can cause a failure to sense contralesional stimuli in the absence of obvious sensory losses. This failure is defined as unilateral extinction if it occurs solely in the case of simultaneous bilateral sensory stimulations. Unilateral extinction can occur with bilateral visual, auditory and tactile stimuli, as well as with bilateral cross-modal stimulations of these sensory systems, and is more frequent following right hemisphere brain damage (RHD) than left hemisphere brain damage (LHD). Unilateral sensory extinction is thought by most to be explained by competition models of selective attention where each stimulus competes to gain access to limited pools of attentional resources. Because of a special role of the right hemisphere in attention, lesions of that hemisphere would disadvantage sensory inputs from the contralateral left hemispace relative from those from the right space. The idea that inputs from the contralesional side of space may undergo a faulty processing regardless of whether they are primarily directed to the damaged or intact hemisphere has been provided on the most part by studies on olfactory neglect and extinction. The laterality of the sensory inputs makes a difference insofar as left-sided inputs directed to the intact left hemisphere are not affected by extinction, or affected to a much smaller degree than left-sided inputs directed to the damaged right hemisphere. In other words, the lateral organization of sensory inputs should be reconsidered as a far from negligible factor in the cross-modal pattern of unilateral sensory extinction from unilateral brain damage. Theories of unilateral extinction Two of the major theories of unilateral extinction are the sensory theory and the representational theory. The sensory theory involves an attenuation of sensory input to the right hemisphere from the contralateral side of the body and space. The representational theory involves a disordered internal representation of the contralateral side of the body and space, not dependent on sensory input. Recent literature suggests that unilateral