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The organization and lateralization of brain activity in infants and toddlers from birth through five years of age
Poster B24 in Poster Session B and Reception, Thursday, October 6, 6:30 - 8:30 pm EDT, Millennium Hall
Stephen Gotts1, Shawn Milleville1, Alex Martin1; 1Section on Cognitive Neuropsychology, Laboratory of Brain and Cognition, NIMH/NIH
The cerebral lateralization of language, fine motor coordination and visuospatial abilities in humans has been studied extensively in adults, and direct relationships have been observed between degree of skill in these domains and the degree of brain lateralization (e.g. Gotts et al., 2013). However, less is known about the developmental trajectory of brain lateralization, especially at the earliest ages. In the current study, we use fMRI data from the Baby Connectome project (Howell et al., 2019) to examine the overall organization and lateralization of resting-state brain activity in sleeping infants and toddlers from birth (0 months) through 5 years of age (N = 260, each with 10 minutes of resting-state fMRI data). Organizing age into non-overlapping bins of approximately 50 participants each (0-6 mo., 7-11 mo., 12-16 mo., 17-24 mo, 25-70 mo.), the resting-state data in each bin were parcellated into networks across a range of thresholds using the InfoMap algorithm (as in Persichetti et al., 2021). Using a common threshold (top 10% of connections) that maximized split-half agreement and number of parcels within each age bin, parcellations were found to be highly similar across bins, with 4 large cortical parcels (Occipital, Lateral Temporal, Somatomotor, and Frontal) and 2 subcortical parcels (Basal Ganglia and Thalamus/Cerebellum). The only prominent changes observed across the age bins involved the differential grouping of the posterior cingulate cortex (PCC) and frontal cortex with the lateral temporal cortical parcels. At the youngest ages, these elements remain in separate parcels (0-6 mo.). From 7-11 months and older, the PCC is grouped with the lateral temporal cortex. Only at the oldest ages (25-70 months) was the frontal cortex grouped with the PCC and the lateral temporal parcels as is typical in adulthood, suggestive of the emergence of a language/speech system. Examining continuous effects of age within and across parcels (partialing head motion), prominent and widespread increases in long-range functional connectivity between parcels were observed with age, whereas increased local functional connectivity (within parcel) was only observed in occipital cortex (P<.028, q<.05 for all). Finally, the lateralization of the cortical parcels was examined using the Segregation (within-across hemisphere correlation) and Integration (within+across hemisphere correlation) metrics developed by Gotts et al. (2013). In contrast to the adult, the strongest lateralization effects were detected with the Integration metric, with left lateralization observed across ages for the PCC, Occipital, and Somatomotor parcels and right lateralization observed for the Frontal parcel. Left lateralization for the PCC parcel (which is part of the larger language system in the adult) was highly significant even for the earliest ages (0-6 mo., P=.0018, q<.05). Only the Occipital parcels exhibited lateralization with the Segregation metric (rightward) (P<.0039, q<.05 for all), and neither metric exhibited strong changes in lateralization over this age range. Taken together, the results suggest that much of the early changes in brain organization involve the establishment of long-range functional connections between large scale brain networks, and cerebral lateralization – while detectable from 0-6 months, differs markedly from the adult in both quantity and quality.
Topic Areas: Development, Multisensory or Sensorimotor Integration