Understanding how the normal brain works and how abnormalities in its function occur in mental illnesses is a major goal of research in cognitive neuroscience and neuropsychiatry. This goal has been enormously facilitated by the invention and development of a variety of neuroimaging tools during the past 20 years. I have been fortunate enough to be able to pioneer the use of many of these tools in both the study of the normal brain and in the study of people who suffer from mental illnesses. Before these tools were available, we could only study the brain after people had died, through using post mortem tissue. Now we are able to visualize and measure the structure, function, and chemistry of the living brain in people of all ages, ranging from childhood to old age. This makes it possible to answer interesting questions about brain development and aging, gender differences, the neural basis of creativity or spirituality, and the neural basis of a variety of mental illnesses.
The tools that our research group is currently using include structural Magnetic Resonance (sMR), functional Magnetic Resonance (fMR), magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), and positron emission tomography (PET). These tools permit us to visualize and measure many aspects of the brain—its anatomy (sMR and DTI), its dynamic responses to a wide variety of cognitive stimuli (fMR and PET), and its chemical activity (MRS and PET).
All our imaging work is informed by a three-stage experimental strategy: work out the methods, work out the anatomy or circuitry or systems in normals, and study the nature of the dysfunctions in patients. Consequently, we began our PET studies (and more recently our fMR studies) with basic methodological work. In addition to conducting basic methodological studies, we focus first on the study of normal individuals. Since most existing concepts concerning brain functions and mechanisms have been derived from lesion studies (i.e., stroke, traumatic brain injury), we have very little solid knowledge about the circuitry involved in the performance of mental operations such as focussing attention or encoding and retrieving information in the intact living human brain. The use of tools such as fMR and PET to map these operations in vivo opens an entirely new perspective in cognitive neuroscience. Instead of having to infer how the brain works by observing how it malfunctions when a particular region is "missing," functional imaging now permits us to observe it during in vivo on line normal performance. This in vivo view of the intact functioning brain has led to a reappraisal of some basic assumptions about brain function, such as the nature of human memory systems and their neural substrates.
During the past 20 years we have also developed a variety of software tools that can be used to extract precise quantitive measurements from MR and PET data. These are available in a software package called BRAINS2. (BRAINS=Brain Research: Analysis of Images, Networks, and Systems.) We provide free access to this software to all interested users. It works on a variety of platforms (e.g., Linux, Mac) and provides measurements of cortical gyrification, brain tissue compartments (grey matter, white matter, and cerebrospinal fluid), and specific brain substructures (caudate, putamen, thalamus, cerebellar lobes, hippocampus).