Experiments were initiated to identify the neuroanatomical basis underlying different types of memory and perceptual dysfunctions exhibited by patients with neurological disorders. One theoretical line focused on using implicit and explicit memory tasks within the framework of data-versus conceptually-driven; other investigations examined the role of the temporal lobe in perceiving information containing high and low spatial frequencies. Normals and right brain-damaged patients did better when memory processing engaged at study (data-or conceptually-driven) matched that required at test. Patients with left hemisphere lesions showed normal performance levels on data-driven tests but were impaired on both implicit and explicit conceptually driven tests. Although controls and left lesion patients performed normally, patients with right hemisphere lesions showed deficits with data-driven, nonverbal materials. When sets of perceptual stimuli were identical, high spatial frequency information was preferred, but when stimuli differed, low frequency information was perceived better. This pattern did not hold for left brain damage subjects who were impaired in strategic processing. Also, patients performed worse than controls in processing upright faces but actually performed better with the inverted faces. Perceptual asymmetries are less pronounced between the hemispheres than processing asymmetries, and the mode of processing interacts with perceptual characteristics of incoming stimuli to bias perception toward high or low spatial frequencies.
