The adolescent brain: insights from functional neuroimaging research

Abstract

With the development of functional neuroimaging tools, the past two decades have witnessed an explosion of work examining functional brain maps, mostly in the adult brain. Against this backdrop of work in adults, developmental research begins to gather a substantial body of knowledge about brain maturation. The purpose of this review is to present some of these findings from the perspective of functional neuroimaging. First, a brief survey of available neuroimaging techniques (i.e., fMRI, MRS, MEG, PET, SPECT, and infrared techniques) is provided. Next, the key cognitive, emotional, and social changes taking place during adolescence are outlined. The third section gives examples of how these behavioral changes can be understood from a neuroscience perspective. The conclusion places this functional neuroimaging research in relation to clinical and molecular work, and shows how answers will ultimately come from the combined efforts of these disciplines.

Figure 1

Figure illustrates some of the currently available cognitive neuroscience methods and sites of action on both temporal and spatial dimensions. Figure adapted from Churchland and Sejnowski, 1988.

Figure 2

Midline sagittal slices of T1 MRI images of the brain on which loci of activation are depicted. These activation maps provide a summary of the results described in the Cognitive Process Section of this chapter. Loci of activation correspond to age group differences of neural activation in response to various cognitive processes. Unfilled white circles represent sites of activations that are greater for younger participants relative to adults. Conversely, filled white circles represent sites of activations that are greater for adults relative to younger participants. The figure was created using the MRIcro fMRI display software (http://www.sph.sc.edu/comd/rorden/mricro.html). Peak coordinates originate from studies reported in the text. When necessary, Talairach coordinates were transformed into MNI coordinates (http://imaging.mrccbu.cam.ac.uk/imaging/MniTalairach). The sites of these activations have been projected to the midline section since they are all displayed at x = 0, even though most of these activation peaks are lateralized (see Table below). [Table: see text]

Figure 3

SPM99 glass brain indicating greater amygdala activation for adolescents relative to adults in response to an emotional face viewing task (Guyer et al., in press).

Figure 4

The triadic model from Ernst et al (2006) shows a functional imbalance among medial/ventral prefrontal cortex, ventral striatum and amygdala circuits in adolescents (left half) relative to the adult equilibrium (right half).

Figure 5

Coronal and sagittal views of the SPM99 T1 MRI brain, which shows activation loci that are greater for adults than adolescents in a decision making task. These foci are located in the left orbitofrontal/ventrolateral prefrontal cortex and anterior cingulate cortex (Eshel et al. 2007).