Since Freud's early years as a budding young neurologist, the hope for objective diagnosis of psychiatric disorders has been alive and well. From Freud's earliest attempts to differentiate hysterical paralysis, loss of sensation, seizure-like episodes, amnesia, and other mental illnesses from certifiable neurologic disorders clinicians have been faced with critical challenges. Most of our classic textbooks have discussed the distinction between the so-called functional and organic disorders with considerable research energy being directed toward being able to differentiate these disorders by mental status examinations or psychological tests. This has been particularly true of schizophrenia in which syndromal qualities have been addressed by several subsequent editions of The Diagnostic and Statistical Manuals of Mental Disorders. The variance in the diagnostic category has been reduced significantly because dimensions, such as good–poor premorbid, paranoid–nonparanoid, positive-negative symptoms, and other such factors, have been considered. Requiring time periods for the manifestation of symptoms along with a better classification of the toxic states and the exclusion of many other biologic complications that can result from psychotic states have further tightened the diagnosis. In spite of these developments, the clinician has still looked forward to more objective and commonly accepted diagnostic criteria.

With major technological developments in the 1970s, clinicians soon had the ability to view the living brain. This has had a major impact on our evolving theory and diagnoses. Because of the emergence of magnetic resonance imaging (MRI) in the mid-1980s, we can now see a slice of the living brain; this slice mimics almost perfectly a slice seen on postmortem (see Figure 1. Even the less-accessible positron emission tomography (PET) scans offered hopes of locating areas of function and dysfunction in the brains of our patients. This further raised the hopes of practicing psychiatrists and psychologists who seek more definitive and objective measures of pathology. Research is proceeding on all sides in this, the “Decade of the Brain”, and we must pause periodically to look at our current state of knowledge and hopes for the future.

Research in areas in which the neurologic substrates are well established (dementias, brain injury, vascular disorders, Parkinsons disease, and so forth) have led the way in the use of these technologies for the diagnosis of pathology. Unfortunately, in psychopathology, the research has been plagued by some circularity in the protocol. In these instances, we use behavioral symptoms and diagnostic descriptors to identify the experimental groups that will then be either confirmed or disconfirmed by imaging studies. Even in more established biologic disorders, the relationship between structure and behavior has not been as compelling as we would hope. Neuroradiologists continue to describe temporal and frontal atrophy in aging populations as being well within normal limits, whereas a subset of these patients show memory and visual-spatial dysfunction that is clearly characteristic of a dementia process.

Nevertheless, our research efforts are leading to significant findings and are totally altering our theoretic explanations of disorders that have historically been explained primarily by psychological conflict, object loss, early developmental patterns, or classical and operant learning. As newer and more available technologies make it possible to observe function, cognitive localization, drug effects, and other such factors, the future seems even more hopeful, despite the many disappointments that abound. This article first briefly describes the neuroimaging procedures that are most accessible and useful to the practicing clinician. Interpretive illustrations of both normal and pathologic images are presented. We offer interpretive strategies along with a view of the current status of imaging products and their potential usefulness in the areas of theory and diagnosis. This is followed by summaries of current research findings of the major areas of psychopathology that have been studied with neuroimaging.