According to Denny-Brown's 1954 articleDenny-Brown, D., and Betty Q. Banker. "Amorphosynthesis from Left Parietal Lesion." A.M.A. Archives of Neurology and Psychiatry 71, no. 3 (March 1954): 302-13. lesions of the parieto-occipital region cause disturbance of recognition in a patient – left-sided lesions usually cause agnosia, while right-sided lesions usually cause lack of recognition of the person's left side and extrapersonal space. Denny-Brown defines agnosia as a disorder in formation or use of symbolic concepts, such as recognizing body parts; in naming objects; in understanding numbers; or in understanding geographic and/or spatial location. It applies to both sides of a person, even though a lesion in only one side of the parietal lobe – the dominant one – causes it. He argues that amorphosynthesis, on the other hand, is usually caused by a lesion in the non-dominant parieto-occipital lobe and results in lack of awareness on the opposite side of the body.
