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A critical period of brain development: studies of cerebral glucose utilization with PET
1Division of Pediatrics, Children's Hospital of Michigan, Wayne State University School of Medicine, Detroit 48201, USA. hchugani@pet.wayne.edu
Insights
The human brain
Area of Science:
- Neuroscience
- Developmental Biology
- Radiology
Background:
- Human brain development extends significantly beyond infancy.
- Positron emission tomography (PET) reveals dynamic changes in brain glucose metabolism during postnatal maturation.
- Early brain activity is concentrated in sensory, motor, and limbic regions.
Purpose of the Study:
- To investigate the protracted timeline of human brain maturation.
- To map the developmental trajectory of glucose utilization in the brain.
- To correlate metabolic maturation with behavioral development and synaptogenesis.
Main Methods:
- Utilized positron emission tomography (PET) to measure glucose metabolism in human subjects across different age groups.
- Analyzed regional glucose utilization rates from birth through adolescence.
- Correlated metabolic data with known developmental milestones and synaptogenesis.
Main Results:
- Glucose metabolism increases in sensory, motor, and visual cortices by 2-3 months, and in the frontal cortex by 6-12 months.
- Childhood brain glucose utilization is significantly higher than adult levels, peaking around age 4.
- Metabolic maturation, characterized by declining glucose utilization, continues until ages 16-18 years.
Conclusions:
- Human brain maturation is a prolonged process extending into late adolescence.
- High childhood glucose metabolism supports extensive neural development and plasticity.
- Findings have implications for understanding brain injury recovery and critical learning periods.
Abstract:
Studies with positron emission tomography indicate that the human brain undergoes a period of postnatal maturation that is much more protracted than previously suspected. In the newborn, the highest degree of glucose metabolism (representative of functional activity) is in primary sensory and motor cortex, cingulate cortex, thalamus, brain stem, cerebellar vermis, and hippocampal region. At 2 to 3 months of age, glucose utilization increases in the parietal, temporal, and primary visual cortex; basal ganglia; and cerebellar hemispheres. Between 6 and 12 months, glucose utilization increases in frontal cortex. These metabolic changes correspond to the emergence of various behaviors during the first year of life. The measurement of absolute rates of glucose utilization during development indicates that the cerebral cortex undergoes a dynamic course of metabolic maturation that persists until ages 16-18 years. Initially, there is a rise in the rates of glucose utilization from birth until about age 4 years, at which time the child's cerebral cortex uses over twice as much glucose as that of adults. From age 4 to 10 years, these very high rates of glucose consumption are maintained, and only after then is there a gradual decline of glucose metabolic rates to reach adult values by age 16-18 years. Correlations between glucose utilization rates and synaptogenesis are discussed, and the argument is made that these findings have important implications with respect to human brain plasticity following injury as well as to "critical periods" of maximal learning capacity.