9 - Cognitive and behavioral probes of developmental landmarks for use in functional neuroimaging

Summary

Introduction

Functional magnetic resonance imaging (fMRI) allows neuroscientists to examine the function of the human brain, especially the developing human brain, in a relatively noninvasive manner. Previous approaches were relatively indirect techniques such as scalp-recorded electroencephalography (EEG) and event-related brain potentials or brain imaging techniques that required exposure to ionizing radiation, for example positron emission tomography (PET), single photon emission computed tomography (SPECT), and X-ray computed tomography (CT). While these latter techniques may be used with pediatric patient populations when clinically warranted, the ethics of exposing children to unnecessary radiation for the advancement of science are still under debate (Casey and Cohen, 1996; Morton, 1996; Zametkin et al., 1996).With fMRI, developmental research is possible. This technique is described in detail in Chapter 3. In the current chapter age-appropriate behavioral paradigms and task designs for use with fMRI in the context of developmental studies are described.

The significance of studying functional brain changes in a developmental context becomes more apparent when we consider aspects of brain development in general (see Chapter 7). The brain continues to develop after birth and well into childhood.Huttenlocher (1990, 1997) has demonstrated that pruning and reorganization of some cortical regions are relatively protracted. While synaptic density reaches adult levels by approximately 5 months in the visual cortex, prefrontal cortex still shows a 10% greater synaptic density at 7 years than in adulthood.