Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Increased behavioral interference from hemispheric collateralization of language production and spatial attention in dual-task performance
Poster Session C, Friday, October 25, 4:30 - 6:00 pm, Great Hall 3 and 4
Miaomiao Zhu1, Qing Cai1; 1East China Normal University, Shanghai, China
Most individuals exhibit left hemisphere dominance for language and right hemisphere dominance for spatial attention, which are considered typical lateralization patterns. Previous studies with brain lesions and animal models have suggested that disruptions during the establishment of functional lateralization can lead to cognitive deficits. However, the effects of different lateralization patterns on behavioral performance and their underlying mechanisms in healthy individuals remain unclear. This study focused on left-handed individuals (N = 98 for brain imaging, 45 of them for behavioral testing), given their higher prevalence of atypical lateralization patterns compared to right-handers. Functional lateralization of language and spatial attention was measured using functional magnetic resonance imaging during the verbal fluency and landmark tasks, respectively. Lateralization indices (LI) were calculated via a bootstrap method, with right dominance defined as LI < 0 and left dominance defined as LI > 0. Language performance was assessed by the number of words generated in the verbal fluency task. Spatial attention ability was measured by spatial bias in the continuous spatial trisection task (CSTT). These single tasks were integrated into a novel dual-task paradigm. Overall behavioral performance was calculated by summing the z-scores of the two tasks, and overall cognitive interference was quantified by summing the z-scores of performance differences between the dual and single tasks. Diffusion data were analyzed using a fixel-based approach to explore the relationship between lateralization patterns and interhemispheric connectivity across seven subdivisions of the corpus callosum. The results indicated that individuals with a collateralization pattern (both functions lateralized to the same hemisphere) exhibited marginally reduced overall performance in the dual-task compared to those with a typical lateralization pattern (T = -2.16, P = 0.055). The reduction was particularly evident in the CSTT but not in verbal fluency task. Second, individuals with a collateralization pattern showed greater overall performance interference than those with a typical lateralization pattern (T = 2.56, P = 0.022). However, no such differences in performance interference were identified between the reversed lateralization pattern (right language dominance and left attention dominance) and the collateralization pattern. Marginal interference differences were also observed between the typical and reversed lateralization patterns (T = 1.77, P = 0.063). Third, no significant differences in callosal connectivity were found among the groups. Additionally, a negative correlation was observed between the degree of lateralization and the combined fiber density and the cross-section of the corpus callosum’s rostrum (r = -0.33, p_fdr = 0.056). These findings suggest that the functional crowding of language production and spatial attention within the same hemisphere increases cognitive interference, thereby reducing cognitive efficiency. The absence of behavioral advantages in the reversed pattern group suggests that while this functional segregation allows for parallel processing, atypical brain organization may diminish the potential benefits. Moreover, the relationship between callosal connection and functional lateralization appears to be related more to the extent of lateralization rather than the pattern. This study advances our understanding of how lateralization patterns influence behavior and offers new insights into the mechanisms underlying cognitive deficits resulting from brain reorganization after lesions.
Topic Areas: Language Production, Disorders: Developmental