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Executive Function and Brain Maturation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Knowing how and why the brain grows and changes during adolescence can help scientists, practitioners, educators, and parents begin to understand the behaviors and feelings associated with normal and abnormal development during this crucial period of life. The laboratory is currently working on several studies designed to aid our understanding of key aspects of brain maturation during adolescence. We are particularly interested in the so-called “executive” areas of brain functioning. “Executive function” refers to cognition encompassing all activities related to planning, organization, self-regulation, self-awareness, emotion and cognition integration, goal-directed behavior, and action initiation. Most executive development in humans occurs during adolescence. Two of the major studies we are conducting in relation to brain maturation and executive functioning are described below. We are hoping to continue both of these studies longitudinally, to capture individual development across the continuum of adolescence. Study: Age-Related Changes in Specific Areas of the Pre-frontal Cortex: Investigating regionally-specific volumetric changes in prefrontal cortex among adolescents In the human brain, the frontal lobe is considered crucial for executive functions including abstract reasoning, behavioral and emotional regulation, and many additional aspects of higher cognition. While previous studies have established that this region of the brain continues to change throughout adolescence, a void persists regarding the regional specificity of this development. The present study used Magnetic Resonance Imaging (MRI) to address this question with the goal of illuminating how volume and organization shift in early puberty (27 subjects; 11.07-19.41-years-old). Though total gray matter volume was found to increase with age, changes within the sub-regions exhibited varied patterns of development. For example, medial prefrontal volume significantly declined with increasing age. Evidence of simultaneous white matter organizational change was also observed. These findings suggest frontal lobe maturation is regionally-specific and may closely parallel refinement of executive functions known to be necessary for a successful transition from adolescence to adulthood. Study: Developmental Changes in Frontal White Matter: Assessing brain connectivity in adolescence It is our goal to integrate results from our fMRI studies with data acquired from diffusion tensor imaging in the same individuals. Diffusion tensor imaging (DTI) is a relatively new magnetic resonance technique that holds great promise with regard to the exploration and characterization of regional connectivity in the developing brain. Simply, DTI is based on the idea that bipolar magnetic field gradient pulses cause the three-dimensional displacement of the water molecules within a given area (termed diffusion anisotropy). It is thought that differences in diffusion anisotropy reflect unique structures within, and resultant organization of, the examined tissue. Diffusion anisotropy in white matter stems from its specific organization in parallel running axonal fiber bundles; diffusion in the direction of the fibers is faster than in the perpendicular direction. Investigators have recently exploited this feature to map the orientation in space of white matter tracks in the brain, assuming that the direction of the fastest diffusion would indicate the overall orientation of the fibers. In isolation this technique will enable the visualization of neural pathways, or the lack thereof in our subjects, thereby enabling an examination of how the brain may establish or embellish specific connections during adolescence. Diffusion Tensor MRI (DTI), combined with blood oxygen level dependant (BOLD) fMRI, allows us to more directly investigate how both the structure and function of the brain influence our ability to perform certain tasks. |
