Use of complex three-dimensional objects to assess visuospatial memory in healthy individuals and patients with unilateral amygdalohippocampectomy

Because many visuospatial memory tests do not reliably detect right medial temporal lobe (MTL) dysfunction, we developed a novel object recognition test using complex three-dimensional stimuli. To influence encoding strategy, half the stimuli were multicolored (color towers) and accompanied by verbally based instructions, and half were gray (gray towers) and accompanied by visuospatially based instructions. In Experiment 1, healthy subjects completed the test while performing verbal or visuospatial interference tasks or without interference. In Experiment 2, patients with unilateral amygdalohippocampectomies for intractable epilepsy completed the test without interference. Results suggest that color tower recognition was partially dependent on verbal processing and sensitive to MTL lesions in general. Recognition of gray towers was reliant on visuospatial processing, and the decay in accuracy after a delay was sensitive and specific to right MTL lesions. These findings suggest that test stimuli such as three-dimensional objects can be useful in assessing right MTL dysfunction.