Age-related differences in the interhemispheric asymmetry of local cortical responses to abstract and concrete verbs in children: a magnetic mismatch negativity study

Abstract

BACKGROUND: The development of brain neural networks that support lexico-semantic processing in children remains a poorly understood topic in neuroscience. Meanwhile, investigations in adults have provided ample evidence regarding the brain circuits underpinning the processing of abstract and concrete semantics. These studies have shown that interhemispheric asymmetry in neural responses across modal and amodal cortical areas might be an important marker that helps in distinguishing these two types of semantics, with more left-lateralized activity patterns for abstract than concrete word comprehension. However, little is known about such distinctions in children; thus, addressing this gap was the goal of this study. AIM: This study aimed to investigate age-related differences in the lateralization of neural response patterns associated with the processing of abstract and concrete semantics in children. METHODS: This study employed magnetoencephalography and a mismatch negativity (MMN) paradigm in a group of 41 healthy children aged 5–13 years. The participants were passively exposed to the auditory series of abstract and concrete Russian verbs presented outside the focus of attention. Spatiotemporal patterns of the dynamics of neuromagnetic sources activity were reconstructed using minimum-norm estimate within predefined regions of interest: primary auditory cortex, primary motor cortex, and inferior frontal gyrus of both hemispheres. The magnitudes of MMN responses were further compared statistically between the two hemispheres within two age groups: younger (aged 5–9 years) and older (aged 10–13 years) children. RESULTS: Regionally specific differences were found in the lateralization of event-related MMN responses to concrete compared with abstract words in motor and inferior frontal cortical areas (paired permutation tests, p 0.05). Moreover, in the younger group (aged 5–9 years), responses to the abstract and pseudoword stimulus were left-lateralized, and this effect was most pronounced in the inferior frontal regions (45 and 47 Brodmann fields) of the left hemisphere. In the older group (aged 10–13 years), no pronounced left-lateralized response was observed in these areas. However, for the concrete hand action verb stimulus, different patterns of the interhemispheric asymmetry of the hand motor area responses were observed: the response in the younger group was right-lateralized, whereas in the older group, the response was bilateral. CONCLUSION: The present area- and hemisphere-specific dynamics of neuromagnetic responses in the motor cortex and Broca’s area might correlate with the age-related changes in neurocognitive strategies for the comprehension of abstract and concrete language.