The Brain: the right hemisphere is the basis of knowledge during the first months of life


The study entitled,Structural and functional brain asymmetries in the early phases of life: a scoping review, by Patrizia Bisiacchi and Elisa Cainelli of the Department of General Psychology of the University of Padua, highlights that the right hemisphere of the newborn brains is the basis of cognitive activities. Asymmetries of the brain are the rule rather than the exception, yet despite this, the process of specialization in one cerebral hemisphere (lateralization) is poorly understood.

Anatomical asymmetries explain only a small part of the functional variability of lateralization, which may differ in regards to age and the characteristics of development. Understanding how hemispheric asymmetries develop can help shed a light on the poorly understood lateralization process, as well as the nature and role of alterations in the cerebral lateralization found in many neurodevelopmental disorders.

Prof. Bisiacchi explains “Our work has shown that premature infants, who may be at high risk of developing learning difficulties may benefit from right hemisphere cognitive stimulation to support the recognition of acoustic and visual stimuli early on in life. This work is based on our review of all scientific articles on functional development (brain activity, at rest or under-stimulation) and structural (anatomy) asymmetries of the brain. We research studies that included full-term neonates, foetuses, and premature infants, resulting in 57 studies, each quite different from one another in terms of technique and methods of investigation. Most of the structural studies focused on the temporal lobe, the hub of language recognition, whose lateralization of the left hemisphere is found in 90% of people, and for which is now a consolidated fact highlights an area generally more pronounced on the left than on the right, and a morphological asymmetry already present from the 29th week of gestation.”

However, not all results agree and variabilities are more evident for other, less studied, brain areas.

Unlike data on structural asymmetries, functional data agree with each other, identifying a leftward dominance for auditory and linguistic stimuli and an overall dominance of the right hemisphere for all other stimuli.

The predominance of the right hemisphere both at rest and during non-linguistic sensory stimulation is in line with Geschwind and Galaburda's (1985) theory of right hemisphere conservatism. According to this theory, the right hemisphere develops earlier and would be less subject to external influences because the basis of its function is necessary for survival, such as emotional processes, facial recognition, and visuospatial processing. The genetic influences on the development of the left hemisphere would instead be less marked, allowing for a slower pace of maturation and greater plasticity and responsiveness to environmental stimulation, necessary for the development of complex functions dependent on the surrounding environment such as language.

“Our review also highlights another dissociation between structural studies and functional results, with controversial results, that are in line with each other,” continues Prof Bisiacchi. “Functional studies may allow the cerebral function to use tasks appropriate for the immature brain, which can capture characteristic asymmetries better than structural, static photographs of the brain. These anatomical investigations also restore the image of areas with slower maturation, characterized by greater plasticity and dependence on experience, which could justify greater inter-individual variability.”

These results, published in the journal Brain Structure and Function, suggest that treating infants at risk should aim at strengthing the functional abilities that are supported by the right hemisphere and more related to the sensory characteristics of the stimuli used.