Injury and recovery in the developing brain: evidence from functional MRI studies of prematurely born children

Abstract

Functional MRI (fMRI) might provide important insights into emerging data that suggest that recovery from injury can occur in the brains of children born prematurely. Strategies employing auditory stimulation demonstrate blood-oxygen-level-dependent (BOLD) activation in preterm infants as young as 33 weeks' gestational age, and reliable BOLD signal in response to visual stimulation occurs at term-equivalent age. Strategies based on fMRI are particularly suited to the study of language and memory, and emerging data are likely to provide insights into perplexing reports that have demonstrated improving cognitive scores but persistent volumetric and microstructural changes in frontotemporal language systems in the prematurely born. Even when sex, gestational age and early medical and environmental interventions are taken into account, fMRI data from several investigators suggest the engagement of alternative neural networks for language and memory in the developing preterm brain.

Figure 1

Blood-oxygen-level-dependent group difference maps (preterm minus term) at 12 years of age in a category language task for males (top row) and females (bottom row). This task is characterized by both positive and negative signal changes. Negative signal changes are shown in blue and violet; positive activations are shown in red and yellow. Male preterm individuals preferentially demonstrate positive blood-oxygen-level-dependent signal in the right language homologs to Broca's region (inferior frontal gyrus) and Wernicke's region (superior temporal gyrus), whereas preterm females do not.

Figure 2

Ventricular size mismatch across groups can provide erroneous evidence for functional differences. In this subtraction, 12-year-old preterm individuals with normal ventricular size and those with ventricular volume measurements at least two standard deviations above the mean were contrasted. Note the positive periventricular blood-oxygen-level-dependent signal shown in red and yellow that arises from a subtraction of white matter (in the normal individuals) and cerebrospinal fluid (in those with ventriculomegaly).

Figure 3

Group difference maps (preterm minus term control study participants) at 12 years of age during a semantic task. As shown by the positive blood-oxygen-level-dependent signals shown in red and yellow, the data indicate a right frontal shift in the language network in the prematurely born children.