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INTRODUCTION
Studies of individuals with intractable temporal lobe epilepsy (TLE) have demonstrated a consistent relationship between the integrity of left mesial temporal lobe structures and verbal memory function (Griffith et al., 2003, Lencz et al., 1992; Rausch & Babb, 1993; Sass et al., 1992). This has made it possible to predict the likely effect of left temporal lobectomy on verbal memory on the basis of presurgical investigations including MRI hippocampal volumetrics (Trenerry et al., 1993), baseline verbal memory testing (Chelune & Najm, 2001), and the intracarotid amobarbital procedure (IAP; Kneebone et al., 1995; Loring et al., 1995).
In contrast to the established connection between the left temporal lobe and verbal memory, the identification of a reliable neuropsychological marker of right mesial temporal integrity has proven elusive. This has particularly been the case with commonly used commercially available tests of nonverbal/visuospatial memory such as the Rey Complex Figure (RCF) and various Wechsler Memory Scale subtests and indices (Barr et al., 1997; Kilpatrick et al., 1997; Kneebone, 2001; Lacritz et al., 2004; Lee et al., 2002; McDermid Vaz, 2004). This has lead some to argue against the lateralized model of material-specific memory function (Saykin et al., 1992) whereby verbal and nonverbal aspects of memory are supported by analogous (homotopic) regions within the left and right temporal lobes, respectively. It has been suggested that the functional correlates of the right hemisphere may not be as tightly associated with its anatomical substrates as those of the left hemisphere (Rausch, 1991). Others instead have argued that the construction of the nonverbal/visuospatial tests and/or the scoring systems used simply do not capture that aspect of performance to which the right temporal lobe makes a substantial and unique contribution (Barr et al., 1997; Lee et al., 1989). In this regard, Barr et al. (1997) point out that the development of nonverbal/visuospatial tests has proceeded with too little consideration of the conceptual advances made in neuroscientific studies of the visual processing system thereby obfuscating the relationship between structure and function.
In a study of nonverbal memory in temporal lobe epilepsy surgery candidates, Brier et al. (1996) attempted to accommodate contemporary theory of visual cognition by devising a scoring system for the RCF with the intent of obtaining separate indices of figural and spatial...