Frank Haist, Ph.D. - US grants

DESCRIPTION (provided by applicant): Face processing is a pivotal component of human social communication and interaction. A single glimpse of a face yields a tremendous amount of information such as identity, gender, age, race, emotional state, attention, intention, and even veracity. Disordered face processing is believed to underlie a variety of social-cognitive disorders. Thus, neuroscientists have devoted considerable attention to understanding the brain foundations of face processing. Most of this work has focused on brain structures involved in adults'expert level face processing, while little effort has been directed to the questions of how these critical brain systems develop. In contrast to the limited data on the development of brain systems for face processing, an extensive body of work has examined the behavioral changes associated with the emergence of face expertise. That work has shown that expertise in face processing emerges slowly over a long period that begins at birth and extends well into adolescence. Experience and development play a crucial role in establishing mature face expertise. The behavioral studies have also shown that expertise with faces involves change in a number of key processing factors. Among these are the level at which faces are processed (subordinate vs. micro- ordinate/individual), the shift to dominance of configural over featural processing, and more subtly the effects of degree of exposure to different classes of faces. This proposal draws from the extensive body of behavioral data on the development of face expertise to direct our exploration of the development of the neural systems that support face processing in 6- to 15-year-old children. Two projects (five experiments) are proposed. Project 1 provides an in depth examination of change in regional responsiveness and neural networks in the developing brain's spontaneous processing of faces as opposed to objects;thus providing a comprehensive measure of neurodevelopmental change in face expertise. Project 2 examines the influence of process-based factors on the emergence of face expertise. We will use innovative analytical tools to explore functional neural systems across development, in addition to traditional fMRI regional analyses. The knowledge obtained from these studies of typically developing children will advance our understanding of face processing in children with neurological impairments (e.g., autism, developmental prosopagnosia, Williams syndrome, perinatal stroke). This could result in new methods for testing typically developing children and provide standards to assess children in special populations that are at risk for visual processing delays and deficits. PUBLIC HEALTH RELEVANCE: Face processing deficits are believed to underlie several profound developmental social-cognitive disorders (i.e., autism, William's Syndrome). This project will provide crucial data on the development of the neural networks and neuroanatomical substrates supporting expertise for human face processing in typically developing children. New theories and assessment methods for children at risk for visual processing deficits and delays may result from these results.

Functional magnetic resonance imaging (FMRI) based on the blood oxygen-level dependent (BOLD) signal has revolutionized cognitive neuroscience. However, the FMRI BOLD signal is an indirect measure of neural activity dependent on fluctuations in the oxygenation level of blood that is neither a direct measure of neural activity nor the hemodynamics responding to that activity. There is accumulating evidence that the indirect nature of the BOLD signal can provide inaccurate estimates of neural activity when comparing groups or individuals with differences in neurovascular coupling. This means that the BOLD signal may provide inaccurate estimates of neural activation in contrasts for typical and atypical development, psychiatric and neurological disorders, and response to psychoactive or pharmacological agents. The BOLD signal may systematically under- or over-estimate neural activity at rest or in response to task or challenge factors in one group or the other. To increase the validity of FMRI, it will be critical to understand how the additional factors modulating the BOLD signal vary across contrasts. This project seeks to meet this challenge by applying a newly developed quantitative FMRI (QFMRI) technology that, unlike other methods of QFMRI, uses standard MRI approaches that do not require the inhalation of special gases (e.g., CO2) and thus are capable of being used in a variety of settings and populations just as traditional BOLD FMRI is used today. Here, we will evaluate the advantages of QFMRI across typical development, an area that has strong evidence for inaccurate estimates of neural activity based on the BOLD signal. This project will use a dual-echo arterial spin labeling (ASL) to obtain baseline cerebral blood flow (CBF) and CBF and BOLD changes during performance on four perceptual processing tasks (visual, auditory, face, and object processing) in three developmental groups: children (8-9 years), adolescents (14-15 years) and young adults (20-30 years). In addition, we will obtain a measure of the cerebral metabolism rate of oxygen (CMRO2) in the baseline state using the newly developed GESSE technique for measuring R2'? (scaling parameter M). In Aim 1, we will use our direct measure of M to define neural activity in our tasks more precisely across development. This will allow us to characterize the validity of the BOLD method in developmental studies. In Aim 2, we will investigate the relationship of our QFMRI estimates of the physiological measures of neural activity with structural brain measures including cortical thickness, area, volume, and whole brain volume. The findings from this study of typical development will have broad implications in all areas of basic and clinical neuroscience, and may provide metrics allowing researchers to adjust prior findings of BOLD signal developmental trajectories to correct for potential underestimates of neural activity in children and adolescents based on the BOLD signal alone.