A previous review of the syndrome of Agenesis of the Corpus Callosum (ACC) identified three primary deficits: reduced interhemispheric transfer of sensory motor information, slowed cognitive processing, and deficits in complex problem solving (Brown & Paul, 2019). Interaction of these three deficits contributes to a variety of secondary cognitive and psychosocial deficiencies across domains. Recent research has also identified a possible fourth core deficit in ACC: restricted capacity for elaborative thought and creativity (Renteria et al., 2022; Bogen & Bogen 1988). We examined the syndrome of ACC using an exploratory factor analysis of neuropsychological test data (not including data regarding interhemispheric transfer) and hypothesized it would organize into factors of (1) reduced cognitive processing speed, (2) difficulty with complex problem solving, and (3) difficulty with creative tasks.

The present study analyzed archival data from individuals with ACC (N=60) acquired from common neuropsychological instruments: D-KEFS, WAIS-III, and WRAT-2. Among the participants, 13 had partial ACC, 1 was unspecified, and the remainder had complete ACC. The participants’ ages ranged from 7 to 55 years (M = 21.55, SD = 12.36), with an education level that ranged from 2 to 19 years (M = 11.59, SD = 3.77). All participants had complete data for at least one assessment and all available data was included. Missing values (49.85%) were excluded from analysis. Factor analysis (principal factor solution with promax rotation) was conducted with 33 commonly derived summary (standard) scores. Horn’s Parallel Analysis recommended a 4-factor solution, but we elected to generate a 3-factor model that would more closely follow previous literature.

Factor one involved processing speed and was comprised primarily of D-KEFS Color Word Interference Word Reading (1.02) and Color Naming (.78), D-KEFS Trail Making Test Visual Scanning (.86) and Number Sequencing (.74), and WAIS-III Processing Speed Index (.68). The second factor included several problem solving measures [e.g. D-KEFS Sorting Test Free Sorting (.90) and Sort Recognition (.90), and WAIS-III Perceptual Organization Index (.72)], as well as several additional measures including WAIS-III Working Memory Index (.84), WRAT-2 Arithmetic (.83), and WAIS-III Verbal Comprehension Index (.80). Finally, the third factor involved several measures requiring mental flexibility and cognitive control [e.g. D-KEFS Twenty Questions Test Achievement Score (.70), D-KEFS Design Fluency Switching Condition (.56), and D-KEFS Trail Making Test Number-Letter Switching Condition (.44)], as well as a measure of single word reading [WRAT-2 Reading (.66)].

The findings support inclusion of slowed cognitive processing speed as a core feature of the neurocognitive syndrome in ACC described by Brown and Paul (2019). The second factor is partially consistent with a deficit in complex problem solving, but is not restricted to that cognitive domain. Likewise, the third factor is largely related to mental flexibility and control (one aspect of creativity), but is not restricted to that domain. Future attempts to model the neurocognitive syndrome of ACC may provide greater clarity by including a wider range of cognitive and psychosocial indices and excluding individuals with comorbid neuropathology.