NEUROPSYCHOLOGY OF LEARNING DISABILITIES: PAST AND FUTURE Byron P. Rourke BYRON P. ROURKE, Ph.D., is professor of psychology, University of Windsor, and clinical professor, School of Medicine, Yale University. INTRODUCTION AND OVERVIEW Specific subtypal definitions. Of particular interest Some of the issues that dominated, or at least held are two subtypes of LD that we have identified in a reli- sway, in the neuropsychology of learning disabilities able and valid manner: nonverbal learning disabilities (LD) in the 1970s included: the definition of LD, (NLD) and basic phonological processing disabilities whether there are reliable and valid subtypes of LD, (BPPD). whether and to what extent LD are related to cerebral The NLD subtype (syndrome) is characterized by a spe- dysfunction, and whether LD are related to types and/or cific pattern of relative assets and deficits in academic degrees of psychosocial dysfunction (Rourke, 1975). It (well-developed single-word reading and spelling rela- is clear that these issues are not mutually exclusive. tive to mechanical arithmetic) and social (e.g., more Indeed, they are intimately connected. We have made efficient use of verbal than nonverbal information in progress in examining these issues, but future chal- social situations) learning, as well as specific, develop- lenges will be substantial. mentally dependent patterns of psychosocial function- ing. Generally, in children with NLD below the age of Definitions: General and Subtypal 4, psychosocial functioning is relatively typical or It has become clear that so-called “discrepancy” defi- reflective of mild deficits. Following this period, emerg- nitions of LD lack scientific credibility (Fletcher et al., ing manifestations of externalized psychopathology are 1989; Fletcher, Francis, Rourke, Shaywitz, & Shaywitz, frequent; the child may be characterized as “hyperac- 1992). One alternative is strictly neuropsychological tive” and “inattentive.” The usual course with respect definitions that my colleagues and I have proposed to activity level is one of perceived “hyperactivity” fol- (e.g., Rourke, van der Vlugt, & Rourke, 2002). lowed by evident normoactivity and then hypoactivity The following are our general definition and some with advancing years. By older childhood and early elements of our specific subtypal definitions of LD. The adolescence, the typical pattern of psychopathology definitions arise from the part of our research program is of the internalized variety, characterized by with- during the last 40 years that has focused on delineating drawal, anxiety, depression, atypical behaviors, and reliable and valid subtypes of LD. (For reviews of this social skill deficits. work and the development of these definitions, see The BPPD subtype is characterized by a specific pattern Rourke, 1985, 1987, 1988a, 1988b, 1989, 1991, 1993, of relative assets and deficits in academic (i.e., poorly 1995a, 1995b, 2000; Rourke & Conway, 1997; Rourke & developed single-word reading and spelling relative to Fuerst, 1992; Rourke et al., 2002.) mechanical arithmetic) and social (e.g., more efficient General definition. LD are specific patterns (sub- use of nonverbal than verbal information in social situ- types) of neuropsychological assets and deficits that ations) learning. The neuropsychological profile and eventuate in specific patterns of formal (e.g., academic) outcomes of this subtype of LD stand in marked con- and informal (e.g., social) learning assets and deficits. trast to those of NLD. For example, the misspellings of LD may also lead to specific patterns of psychosocial individuals who exhibit NLD are almost always phonet- functioning. These generalizations must be construed ically accurate (Sweeney & Rourke, 1978), whereas the and evaluated within the context of particular historical misspellings of persons with BPPD are most often pho- and sociocultural contexts. netically inaccurate. Also, the neuropsychological assets Volume 28, Spring 2005 111 and deficits of the BPPD subtype do not necessarily lead tant because the common phenotype of NLD evident to any particular configuration of difficulties in psy- in these diseases and disorders (Rourke et al., 2002) chosocial/adaptive behavior. strongly suggests that a common treatment program For a more extensive description of the neuropsycho- (e.g., Rourke, 1995d) should be considered for interven- logical assets and deficits (definitions) of NLD, the inter- tion planning with youngsters who exhibit them. For ested reader is referred to Rourke (1989). The principal this and other reasons, investigations along these lines characteristics of NLD have been refined (e.g., Casey, would be expected to continue. Rourke, & Picard, 1991; Harnadek & Rourke, 1994; Psychosocial Dimensions of LD Rourke & Tsatsanis, 1996), and the NLD and BPPD The investigation of the relationship between psy- subtypes more fully explored (Rourke, 1995a, 1995b; chosocial functioning and LD has a long history in the Rourke et al., 2002). field. Many early studies of the relationship between LD We have also developed rules of classification for NLD and psychosocial functioning were aimed at discovering and BPPD (e.g., Drummond, Ahmad, & Rourke, in press; the psychosocial profile of children with LD. Most of Pelletier, Ahmad, & Rourke, 2001), which have been these investigators assumed that this profile would be shown to have clear external validity with respect to dysfunctional. However, no such profile was found. types of psychosocial dysfunction for children (Pelletier (Rourke and Fuerst [1991] provided a summary of this et al., 2001) and adults (Ahmad, Rourke, & Drummond, early work.) under review). The next step in our study of subtypes of Once again, it was the determination of subtypal dif- LD involves determining reliable and valid neuropsy- ferences that led to advances in this area. First, it was chological assets and deficits of children who exhibit demonstrated that there are reliable subtypes of psy- the “output disorder” subtype (see Rourke, 1989, and chosocial functioning among children with LD (Fuerst, Rourke & Del Dotto, 1994). This subtype is character- Fisk, & Rourke, 1989; Fuerst & Rourke, 1995; Rourke ized by deficits in organizing, directing, and orchestrat- 1988a; Rourke & Fisk, 1981). Next, we were able to ing behavior rather than by deficits that derive demonstrate that the incidence and severity of psy- primarily from limitations in “receptive” skills (as in chosocial dysfunction is radically dependent upon sub- NLD and BPPD). typal differences (e.g., Pelletier et al., 2001; Rourke & LD and Brain Dysfunction Fuerst, 1991, 1992, 1996; Tsatsanis, Fuerst, & Rourke, An early article (Rourke, 1975) pointed out that the 1997). For example, we have demonstrated several assumption then in vogue, namely, that LD were due to times that children with NLD are particularly and some type of brain dysfunction, was scientifically un- increasingly prone to serious forms of psychosocial dys- justifiable. Rather, it was the task for neuropsychologists function over the course of development, whereas those to demonstrate whether and to what extent such was with BPPD are not (e.g., Tsatsanis et al., 1997). Also of the case. interest, these psychosocial subtypes are evident regard- Since that time, this issue has undergone rather less of level of Full Scale IQ (Ralston, Fuerst, & Rourke, intense scientific study. As a result, we are now 2003), and in children who have sustained traumatic fairly confident that there are strong relationships brain injury (Hayman-Abello, Rourke, & Fuerst, 2003). between brain dysfunction and LD. These relationships It is expected that future studies of this nature will have been most clearly demonstrated in neuroimaging continue to shed light on the complex interactions and electrophysiological studies involving evoked between LD, psychosocial functioning, and brain func- responses. And, once again, these relationships are tion/dysfunction. For example, we have begun to inves- strongly, and sometimes exclusively, related to LD tigate possible differences in the brain metabolism of subtypal differences (Collins & Rourke, 2003; Dool, children with LD who exhibit different subtypes of psy- Stelmack, & Rourke, 1993; Fiedorovicz et al., 2001). chosocial functioning. This approach yielded very inter- Furthermore, it has been demonstrated that the pat- esting results when applied to children with epilepsy tern of neuropsychological assets and deficits that (Collins & Rourke, in preparation), and we expect that characterizes NLD is evident in a wide variety of pedi- this will be the case for children with LD as well. atric neurological diseases and disorders such as Interventions for LD Asperger syndrome (Ellis & Gunter, 1999; Klin, A number of interventions have been suggested for Volkmar, Sparrow, Cicchetti, & Rourke, 1995), early children with LD (e.g., Rourke, 1995d; Rourke, Fisk, & shunted hydrocephalus (Fletcher, Brookshire, Bohan, Strang, 1986; Rourke et al., 2002). Some that seem par- Brandt, & Davidson, 1995), velocardiofacial syndrome ticularly exciting from a neuropsychological perspective (Fuerst, Dool, & Rourke, 1995), and Williams syndrome are those currently being investigated by G. Reid Lyon, (Anderson & Rourke, 1995). This is particularly impor- Jack M. Fletcher, and their associates. A recent review Learning Disability Quarterly 112 (Lyon, Fletcher, Fuchs, & Chhabra, in press) contains Fuerst, D. R., Fisk, J. L., & Rourke, B. P. (1989). Psychosocial func- a considerable