Nouchine Hadjikhani
For the past thirteen years, I have successively used anatomy, histology, Positron Emission Tomography (PET), functional Magnetic Resonance Imaging (fMRI), Diffusion Tensor Imaging (DTI), electroencephalography (EEG), magnetoencephalography (MEG) as well as behavioral methods to study the normal and the diseased brain.
My dissertation was based on anatomical studies of the human visual cortex, and examined the callosal connections between different areas of the human brain. As a postdoctoral fellow, I have used PET to address the issue of crossmodal matching between touch and vision, and was able to show communication between modality specific areas through the claustrum.
Since I came to the MGH/HMS/MIT-Athinoula A.Martinos Center for Biomedical Imaging, I have been using different method of brain imaging (fMRI, EEG, MEG) to better characterize the different functional components of our visual system. Using fMRI, we discovered and characterized the area of the brain responsible for color vision. With this knowledge of the basis of the functional organization of the brain, the next issue I have been concentrating on is the interaction between these different areas, both in normal subjects and in people with medical conditions such as migraine, focal brain damage and developmental disorders such as autism. I now share my time between the Martinos Center in Boston and the Brain and Mind Institute at EPFL, Lausanne, Switzerland.
Migraine is a very common yet poorly understood phenomenon. In about 20% of patients, the headache is preceded by a visual phenomenon called the aura. For the first time, our group was able to show that the aura of migraine was a phenomenon similar to cortical spreading depression, invalidating the old vascular theory of migraine and opening new perspectives in the treatment of this common and debilitating disorder. Presently, our group is working on extending our understanding of the pathophysiology of migraine, and examining the long-term consequences of this disease on the brain.
Neurological syndromes following focal lesions provide a way to better understand the functional organization of the brain. We have been using this approach to investigate the network of areas involved in face recognition. Examining the responses of lesioned brains to stimuli characterized in normal controls can cast light on the potential plasticity and help identify appropriate strategies to adopt for rehabilitation.
Autism is a neurodevelopmental disease that affects 1:166 children. The etiology of this syndrome is still not well understood, and the correlations between autism behavioral deficits and their biological substrate is only starting to emerge. Based on our previous studies of the organization of the visual system, we were able to demonstrate that "low level" visual processing is normal in individuals with autism, ruling out a bottom-up deficit. Moreover, our group was the first to provide data disproving a popular theory stating that individuals with autism are lacking the brain area devoted to face identification, opening new hypotheses on the etiology of some of the behavioral aspects of autism potential new therapeutic strategies. We are actively pursuing projects of multimodal imaging of neurodevelopmental disorders.
Emotion perception has been studied using functional imaging for several years, but to date has been concentrated primarily on processes associated with viewing facial expressions. However, from an evolutionary perspective, investigations of expressive body movements may be just as important for understanding the neurobiology of emotional behavior. We published the first functional study on the perception of body expression of emotion in normal subjects, and we are using this new and fascinating model of emotion perception to examine neurodevelopmental disorders and intend to explore this aspect of emotional cognition in autism.