Hemispheric lateralization of verbal and spatial working memory during adolescence

Abstract

Adult functional magnetic resonance imaging (fMRI) literature suggests that a left-right hemispheric dissociation may exist between verbal and spatial working memory (WM), respectively. However, investigation of this type has been obscured by incomparable verbal and spatial WM tasks and/or visual inspection at arbitrary thresholds as means to assess lateralization. Furthermore, it is unclear whether this hemispheric lateralization is present during adolescence, a time in which WM skills are improving, and whether there is a developmental association with laterality of brain functioning. This study used comparable verbal and spatial WM n-back tasks during fMRI and a bootstrap analysis approach to calculate lateralization indices (LI) across several thresholds to examine the potential of a left-right WM hemispheric dissociation in healthy adolescents. We found significant left hemispheric lateralization for verbal WM, most notably in the frontal and parietal lobes, as well as right hemisphere lateralization for spatial WM, seen in frontal and temporal cortices. Although no significant relationships were observed between LI and age or LI and performance, significant age-related patterns of brain activity were demonstrated during both verbal and spatial WM. Specifically, increased adolescent age was associated with less activity in the default mode brain network during verbal WM. In contrast, increased adolescent age was associated with greater activity in task-positive posterior parietal cortex during spatial working memory. Our findings highlight the importance of utilizing non-biased statistical methods and comparable tasks for determining patterns of functional lateralization. Our findings also suggest that, while a left-right hemispheric dissociation of verbal and spatial WM is apparent by early adolescence, age-related changes in functional activation during WM are also present.

Reduced Frontal Activations at High Working Memory Load in Mild Cognitive Impairment: Near-Infrared Spectroscopy

“…This finding suggests that the magnitude of WM-related frontal activations may be an indicator of neural efficiency in processing verbal WM. Some neuroimaging studies have found that verbal WM was left-lateralized in the brain [26,75], whereas others have reported that it was processed bilaterally [30,76]. The present findings support the view that verbal WM is processed by the prefrontal cortices on both sides.…”

Differences in brain morphology and working memory capacity across childhood

“…Differences in corpus callosum anatomy such as reduced volume or reduced microstructural integrity are related to lower lateralization of function in typical participants and patient groups (Hinkley et al., 2016; Just, Cherkassky, Keller, Kana, & Minshew, 2007; Persson et al., 2006). In turn, lower lateralization is associated with lower performance on cognitive tasks, including executive function tasks (Hinkley et al., 2012; Just et al., 2007; Nagel, Herting, Maxwell, Bruno, & Fair, 2013). Similarly, posterior temporal white matter may provide connections for integration between specialized regions of temporal lobe for verbal and visuospatial working memory with the posterior parietal executive attention network.…”

The contributions of handedness and working memory to episodic memory

“…The absence of an association between WM and handedness may reflect the fact that verbal WM tasks are predominantly left hemisphere lateralized (e.g., Nagel, Herting, Maxwell, Bruno, & Fair, 2013;Wagner, Sziklas, Garver, & Jones-Gotman, 2009), and although some studies have also shown a bilateral involvement, these are strongly attributed to the use of visual strategies to remember the verbal WM material better (e.g., Gerton et al, 2004;Haut et al, 2000). Given that the handedness differences are presumed to reflect differential access to right hemisphere processes, it may be that the handedness groups do not differ in access to left hemisphere processing.…”