The postnatal development of the motor speech area: a preliminary study

Area of Science:

• Neuroscience
• Developmental Biology
• Speech Science

Background:

• Motor speech and orofacial motor zones mature throughout early childhood.
• Brain hemisphere lateralization is critical for specialized functions like language.

Purpose of the Study:

• To investigate the maturation of motor speech and orofacial areas in both hemispheres of infants.
• To analyze dendritic development patterns in relation to hemispheric and functional dominance.

Main Methods:

• Quantitative analysis of basilar dendrite patterns in layer 5 cortical pyramids.
• Study included 17 age-graded human infants from 3 to 72 months.

Main Results:

• Early development (3 months) shows right hemisphere prominence in orofacial areas over motor speech areas.
• A shift occurs, with left hemisphere dendrite systems eventually exceeding the right by 72 months.
• Despite leftward shift, right motor speech areas retain longer distal segments even in mature subjects.

Conclusions:

• Early right-hemisphere structural primacy transitions to left-hemisphere primacy, potentially linked to phylogenetic asymmetries.
• Developmental dissociation between macro- and microenvironments, influenced by epigenetics, may occur.
• A critical period for language acquisition is suggested, impacting normal lateralization.