Use of complex three-dimensional objects to assess visuospatial memory in healthy individuals and patients with unilateral amygdalohippocampectomy Benjamin M. Hampstead a,b, ⁎, Simon Lacey c , Sunita Ali b , Pamela A. Phillips b , Anthony Y. Stringer b,d , K. Sathian a,b,d,c a Rehabilitation R&D Center of Excellence, Atlanta VAMC, Decatur, GA, USA b Department of Rehabilitation Medicine, Emory University, Atlanta, GA, USA c Department of Neurology, Emory University, Atlanta, GA, USA d Department of Psychology, Emory University, Atlanta, GA, USA abstract article info Article history: Received 10 October 2009 Received in revised form 17 February 2010 Accepted 19 February 2010 Available online xxxx Keywords: Learning Memory Visual memory Epilepsy Medial temporal lobe Amygdalohippocampectomy Neuropsychological 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. Published by Elsevier Inc. 1. Introduction The medial temporal lobes (MTLs) are critical for learning and memory [1] and are also highly susceptible to seizure activity [2]. It is widely accepted that, in a normally lateralized brain, lesions to the left MTL result in verbal memory deficits, whereas right MTL lesions affect visuospatial memory—findings that date back to the seminal works of Milner [3] and Kimura [4]. As a result, neuropsychological evaluations employ a variety of verbal and visuospatial memory tests to help lateralize dysfunction in patients with temporal lobe epilepsy (TLE) and assess the risks of postoperative memory decline. Although the relationship between verbal memory and the left MTL is well established [5–10], many commonly used visuospatial memory tests do not reliably detect right MTL dysfunction. For example, no significant performance differences were found between patients with left and those with right TLE on the Brief Visuospatial Memory Test—Revised [11], Taylor Complex Figure (TCF) or Figure Memory Test [12], Continuous Visual Memory Test [13], or Rey–Osterrieth Complex Figure [14,15]. Although some subtests of the Wechsler Memory Scale may detect right MTL dysfunction [16], there is no consensus on this [6,17–19]. One reason for this inconsistency may be that the right MTL and associated areas mediate learning and memory for complex visuospatial information such as faces, landscapes, and buildings [20,21], all of which are three-dimensional and not easily verbally described. Conversely, the traditional “pencil and paper” neuropsychological tests are two- dimensional and may be susceptible to verbal labeling [17] (consistent with a dual-coding approach [22]). Because the hippocampus is involved in learning and memory of novel stimuli [23] and associating spatial relationships between objects [24], the right MTL may be critical for the initial learning of novel visuospatial material [25]. These considerations suggest that tests using novel, complex, three-dimen- sional stimuli, which are difficult to verbalize, should be more sensitive to right MTL dysfunction than the traditional tests described above. In support of this, patients with right TLE have consistently demonstrated deficits (relative to healthy controls or patients with left TLE) on tests assessing spatial memory with object–location associations [7,26–29] and complex scenes [30]. Consistent with Milner's initial findings [3], tests involving facial recognition have also shown promise in detecting right MTL dysfunction [31]. The severity of deficits on such tests is associated with the extent of right hippocampal resection [28]. Epilepsy and Behavior xxx (2010) xxx–xxx ⁎ Corresponding author. Department of Rehabilitation Medicine, Emory University School of Medicine, 1441 Clifton Road NE, Room 150, Atlanta, GA 30322, USA. Fax: +1 404 712 1652. E-mail address: bhampst@emory.edu (B.M. Hampstead). YEBEH-02224; No. of pages: 7; 4C: 3 1525-5050/$ – see front matter. Published by Elsevier Inc. doi:10.1016/j.yebeh.2010.02.021 Contents lists available at ScienceDirect Epilepsy and Behavior journal homepage: www.elsevier.com/locate/yebeh ARTICLE IN PRESS Please cite this article as: Hampstead BM, et al, Use of complex three-dimensional objects to assess visuospatial memory in healthy individuals and patients with unilateral amygdalohippocampectomy, Epilepsy Behav (2010), doi:10.1016/j.yebeh.2010.02.021