NIRS as a Tool for Early Clinical Diagnosis of Autism

Autism is usually described in terms of behaviors, such as abnormal and repetitive movements, difficulties in producing speech, and other manifestations of impaired executive planning and motor control. These behaviors are thought to reflect underlying disconnections in the nervous system. Magnetoencephalography (MEG), functional neuroimaging (fMRI), positron emission tomography (PET), electroencephalography (EEG), and diffusion tensor imaging (DTI) are all being used in complementary ways to establish an understanding of autism in terms of functionally associated regions of the brain. Patterns of dynamic communication across anatomically distinct brain structures can be studied using event-triggered experimental protocols in fixed laboratory settings. There remains, however, the important challenge of detecting the early emergence of abnormal connectivity and asynchrony in the brains of at-risk infants, preferably with non-invasive, fast, and relatively inexpensive scanning procedures.

The near-infrared portion of the electromagnetic spectrum, coupled with the well-known absorption differences between oxygenated and deoxygenated hemoglobin can, in principle, allow detection of regions of active brain activity analogous to BOLD measurements with magnetic resonance spectroscopy. In fact, the absorptive properties of infrared light are ideal for somewhat deeper tissue imaging provided that scattering can be source-modeled. The development of fast multi-channel electro-optic processors and source-detector pairs deployed on skull-caps has enabled the emergence of near-infrared spectroscopy (NIRS), sometimes referred to as diffuse optical tomography (DOT). This technology could prove useful in the early detection of temporal processing or functional connectivity problems in human infants, as well as impaired blood circulation that might limit neurodevelopment.

This Boston Club addressed the progress that has been made in applying NIRS to the problem of autism. Is there a unique diagnostic niche that could be occupied by this relatively inexpensive technology? What hurdles must be surmounted before these instruments can be used to obtain replicable data over time and in comparison with other investigators? Will it be possible one day to measure absolute, rather than relative, levels of blood flow, opening up the possibility of monitoring responses to pharmaceutical or behavioral interventions?

Sharon Fox, MD, Children’s Hospital Boston

Martha Herbert, MD, Ph.D., Massachusetts General Hospital

Katherine Martien, MD, Massachusetts General Hospital

Near- Infrared Spectroscopy and High Density EEG to Study Neural Mechanisms of Cognitive Dysfunction in Autism
Andrei Medvedev, Ph.D., Georgetown University

The Social Brain and its Development in Autism
Kevin Pelphrey, Ph.D., Yale University

Developing and Validating Near- Infrared Neuroimaging for Mobile Clinical Applications
Gary Strangman, Ph.D., Massachusetts General Hospital

Neuroimaging of Autism: Connectivity and Cognition
John Van Meter, Ph.D., Georgetown University

Jennifer Wagner, Ph.D., Children’s Hospital Boston

2009

The Nancy Lurie Marks Family Foundation, Wellesley , MA