Structural and functional magnetic resonance imaging in psychiatric disorders

Objective: To report on recent advances in both structural and functional brain imaging studies in psychiatry and to highlight their importance for the field. Method: We reviewed recently published articles dealing with such advances and abstracted them into a selective review of the field. Results: Some of the more important trends include integration of genetic information into research studies, use of novel quantitative image measurement techniques, studies of new subject populations, the use of pharmacologic probes in functional magnetic resonance imaging (fMRI) studies, the incorporation of elements of virtual reality into fMRI task stimuli, and the methodological innovation of hyperscanning. Conclusions: A whole series of new approaches and techniques are resulting in rapid advances in neuroimaging in psychiatry. Several of these show the potential for clinical translation. (Can J Psychiatry 2007;52:158-166) Information on funding and support and author affiliations appears at the end of the article. Clinical Implications * Quantitative measurements obtained from brain imaging are beginning to illuminate our understanding of disease mechanisms in schizophrenia and to cross traditional diagnostic boundaries. * Future definitions of schizophrenia (and many other psychiatric illnesses) will likely come to rely more on such measures. Limitations * The more recent, most informative quantitative brain-imaging measurements are currently not widely available outside specialized centres. * Such measures are also generally more informative at a group, rather than an individual, level. Key Words: functional magnetic resonance imaging, diffusion tensor imaging, independent component analysis The field of neuroimaging in psychiatric disorders has made enormous advances since the first computed tomography studies of patients with chronic schizophrenia some 30 years ago. Some of the more important recent trends include the integration of genetic information into both structural and functional studies, leading to "neuroimaging genomics." Other major influences on psychiatric neuroimaging in the last few years involve the use of a series of novel quantitative image measurement techniques developed for both structural and functional imaging studies, including VBM and algorithms for fusion of images from different imaging modalities (for example, sMRI and fMRI). Although the widespread availability of whole-brain voxel-based measurement techniques such as VBM has expanded the number of brain structures that can be easily and rapidly assessed, the debate over the comparability of this new technique to the use of traditional hand-drawn ROIs is not fully resolved. Also new is the examination of patients with a far wider spectrum of clinical disorders and the inclusion of unaffected first-degree relatives, as well as research including large numbers of subjects, often necessitating multisite research collaborations. Also discussed are newer strategies in functional neuroimaging, including use of pharmacologie probes in fMRI studies, fMRI task stimuli incorporating elements of virtual reality, and the methodologic innovation of hyperscanning. Several comprehensive recent reviews describe the brain regions and circuits implicated in various major mental illnesses and enumerate the affected areas.1-4 Rather than our resummarizing a catalogue of brain regions involved in these disorders, it is of greater intrinsic interest that we review the contemporary themes serving to motivate sMRI and fMRI brain-imaging research in psychiatry. Some of these efforts are not without their controversial aspects, so we also review the debates concerning their application. Let us start with an overview. We will discuss new disciplines such as neuroimaging genomics.5 One innovation that we comment on, but do not explore further, is the move away from neuroimaging studies examining single, isolated brain regions and the move toward examining neural circuits. …