fMRI Studies
Our laboratory specializes in using functional magnetic resonance imaging (fMRI) to reveal the neural underpinnings of autism. In so doing, our studies are conducted with adults and adolescents with autism, as well as infants and toddlers at risk for the disorder. In this way we can discover how the brain changes across development. Additionally, we have used fMRI to study brain functional development in typically developing infants and toddlers. Results from our studies of normal development are foundational to our understanding of the mechanisms that go awry in autism.
fMRI with School-Age Children, Adolescents and Adults During Face Processing Reveal Surprising Properties about Brain Function in the Disorder
For many, the ability to process a face is fundamental to the human social experience. It is the face that conveys socio-emotional meaning and acts as a portal between one’s internal state and the surrounding environment. Early studies of face processing in autism revealed a startling effect: reduced or completely absent functional activity in the brain region that strongly supports face processing, namely, a region in the middle lateral fusiform gyrus often referred to as the “FFA.” (see Pierce et al., 2001; Schultz et al., 2000) for examples of this early work.
New studies, however, now show a remarkable effect: Namely, extrinsic factors that serve to increase attention, motivation, or interest can cause more normal functional activation in brain regions and networks in high functioning autistic individuals. For example, showing familiar faces (Pierce et al., 2004) or increasing gaze fixation to the face by inserting a dot on the face and instructing subjects to attend to the face results in more normal fusiform activity (Hadjikhani et al., 2004; Hadjikhani et al., 2007).
One interpretation of this finding is that the fusiform gyrus, an important brain region involved in face processing in normal individuals, can and does function in autism, but whether or not it does so depends more on systems that mediate fusiform function, such as attention, motivation, and reward systems, rather than the fusiform per se.
fMRI Studies with Typically Developing Toddlers Reveal How the Brain Develops Language Expertise
While studies of the older child and adult with autism have revealed findings that may be key to our understanding of the neurobiology of autism, they can not directly inform questions of how autism first emerges. A question we are addressing in our research is what are the brain regions that are abnormal at the earliest ages in autism, when aberrant language and social behaviors are first detected? To do this, we utilize fMRI methodology to map specific brain regions that are responsive to different stimuli. Because fMRI requires that the child remain very still, we perform these studies during natural sleep without the use of sedation or medication.
In order to identify the key systems that fail in autism, an understanding of the neural bases for typical language acquisition at this critical time period is needed. We addressed this question in our sleep fMRI study of typical toddlers (Redcay et al, in press 2007). As shown in the Figure below, in response to speech, typical toddlers in our study displayed extended networks of activation to complex speech information. Specifically, functional activity was prominent in a number of different frontal and cerebellar regions that are involved in social, emotional, attention, novelty detection or sequence tracking functions in adults, whereas activity in 3 year old typical children was prominent primarily in classic adult receptive language cortices. It may be that activation of these long-distance extended networks is important in establishing long distance connectivity, organizing long-distance synchronized interactivity, and stabilizing specialized and lateralized functional networks during early development. Moreover, this evidence supports a more general assumption in the neurodevelopmental literature that frontal cortex development is key to the rapid acquisition of a variety of higher-order complex skills
fMRI with infants and toddlers at-risk for autism
Our laboratory is currently in the process of collecting data on the brain response to both language and emotion stimuli in infants and toddlers at-risk for an ASD.
Preliminary results of our language study suggest that 2-3 year-old children with autism show neither the normal full extended networks present in younger mental-aged matched typical toddlers, nor the mature pattern seen in chronological age-matched typical children. Instead in response to speech, these young autistic children display signs of immature, deviant and abnormally lateralized activity in frontal and temporal cortices, the cortices with the most overgrowth at that age.