Functional magnetic resonance imaging. A new technique with implications for psychology and psychiatry

When change is the only constant: The promise of longitudinal neuroimaging in understanding social anxiety disorder

Longitudinal studies offer a unique window into developmental change. Yet, most of what we know about the pathophysiology of psychiatric disorders is based on cross-sectional work. Here, we highlight the importance of adopting a longitudinal approach in order to make progress towards identifying the neurobiological mechanisms of social anxiety disorder (SAD). Using examples, we illustrate how longitudinal data can uniquely inform SAD etiology and timing of interventions. The brain's inherently adaptive quality requires that we model risk correlates of disorders as dynamic in their expression. Developmental theories regarding timing of environmental events, cascading effects and (mal)adaptations of the developing brain will be crucial components of comprehensive, integrative models of SAD. We close by discussing analytical considerations when working with longitudinal, developmental data.

Cognitive neuroscience from a behavioral perspective: A critique of chasing ghosts with geiger counters

Cognitive neuroscience is a growing new discipline concerned with relating complex behavior to neuroanatomy. Relatively new advances in the imaging of brain function, such as positron emission tomography (PET), have generated hundreds of studies that have demonstrated a number of interesting but also potentially problematic brain-behavior relations. For example, cognitive neuroscientists largely favor interpretations of their data that rely on unobserved hypothetical mechanisms. Their reports often contain phraseology such as central executive, willed action, and mental imagery. As B. F. Skinner argued for decades, cognitive constructs of neurological data may yield nothing more than a conceptual nervous system.

Reduction in BOLD fMRI response to primary visual stimulation following alcohol ingestion

The physiology of alcohol's effects on brain function is poorly understood. Emission tomographic imaging has revealed both acute and chronic alterations in resting cerebral hemodynamics and metabolism following alcohol ingestion. However, cerebral functional integrity under these conditions has received less attention. Functional magnetic resonance imaging (fMRI) offers a non-invasive method for assessing brain functional activation. In order to assess its utility for studying the effect of alcohol on brain function, we performed fMRI with photic stimulation before and after administration of either 0.7 mg/kg alcohol (N = 12) or placebo (N = 5), resulting in peak breath alcohol levels averaging 0.069 g/dl. We found that the amplitude of visual cortical activation in response to photic stimulation was significantly reduced by approximately 33% following alcohol administration (4.0 +/- 1.7% vs. 2.7 +/- 1.3%, P = 0.02), but not following placebo (4.2 +/- 1.5% vs. 4.1 +/- 1.4%, P = 0.7). The results also suggest that the baseline right hemispheric predominance of activation in response to photic stimulation may be reduced following alcohol, suggesting a greater effect on the right hemisphere, consistent with previous studies and alcohol's known effects on visuospatial processing. In addition, through the course of each activation session, there was a progressive reduction in response following alcohol. These data demonstrate that the cerebral effects of alcohol intoxication can be studied with fMRI, and that the effects on brain function of even moderate alcohol intoxication may be widespread, may be lateralized, and may include the visual system.

Abnormal facial emotion recognition in depression: serial testing in an ultra-rapid-cycling patient

Normal subjects use the right insula and bilateral anterior temporal and prefrontal cortices to recognize the emotion expressed in a human face. Mood disorder subjects have a selective deficit in recognizing human facial emotion. Brain imaging studies show that they fail to activate the right insula to the same degree as controls, even when accurately assessing facial emotion. Many issues remain, however, including whether the facial emotion recognition errors in mood disorder subjects are state dependent or persist during normal mood states (and, thus, reflect a trait abnormality). To probe this issue, we repeatedly studied a male bipolar II patient's ability to recognize faces' emotional content. This patient made significantly more errors in facial emotion recognition during the depressed state. He also demonstrated a significant negative bias when he was depressed compared with nondepressed states. This case study demonstrates the state dependency of the defect in human facial emotion recognition.

Multi-modality mapping of motor cortex: comparing echoplanar BOLD fMRI and transcranial magnetic stimulation. Short communication

Multiple non-invasive methods of imaging brain function are now available for presurgical planning and neurobiological research. As these new methods become available, it is important to understand their relative advantages and liabilities, as well as how the information gained compares across different methods. A current and future trend in neurobiological studies as well as presurgical planning is to combine information from different imaging techniques. Multi-modal integration may perhaps give more powerful information than each modality alone, especially when one of the methods is transcranial magnetic stimulation (TMS), with its ability to non-invasively activate the brain. As an initial venture in cross comparing new imaging methods, we performed the following 2 studies, locating motor cortex with echoplanar BOLD fMRI and TMS. The two methods can be readily integrated, with concurring results, although each have important limitations.

Schizophrenia, psychosis, and the basal ganglia

Schizophrenia is one of the most common and perhaps the most disabling of mental disorders, for which effective forms of treatment have not yet been established definitively. The findings reviewed in this article strongly suggest that basal ganglia abnormalities are involved in the pathophysiology of psychotic syndromes in general, and schizophrenia in particular.

The functional neuroanatomy of mood disorders

Mood disorders may be associated with global and regional changes in cerebral blood flow and metabolism. The accumulated functional neuroimaging findings in mood disorders were reviewed in order to examine a proposed neuroanatomic model of pathophysiology. Global cerebral blood flow and glucose metabolism appear normal, but may be decreased in late-life depression. Regional cerebral blood flow and glucose metabolism deficits are present, and may be indicators of brain regions participating in neuroanatomic circuits involved in mood disorders. Decreased pre-frontal cortex blood flow and metabolism in depressed unipolar and bipolar patients are the most consistently replicated findings, and correlate with severity of illness. Basal ganglia abnormalities have been found in depressed unipolar and bipolar patients, involving decreased blood flow and metabolism. Temporal lobe abnormalities are present in bipolar disorder patients, and perhaps unipolar depression. There is conflicting evidence of abnormalities in other limbic regions. Cognitive impairment may correlate with decreased metabolism in frontal and cerebellar areas. The relationship between functional neuroimaging findings and clinical course, and therefore state and trait characteristics, has not been systematically investigated. Antidepressant medications, but not ECT, seem to reverse some of the identified functional brain changes in the depressed state. The structural, neurotransmitter and neuropathological correlates of these functional abnormalities are yet to be determined. Functional abnormalities in frontal, subcortical and limbic structures appear to be part of the pathophysiology of mood disorders.

Functional magnetic resonance imaging in schizophrenia: initial methodology and evaluation of the motor cortex

The purpose of the present study was to evaluate the differential activation of the motor cortex during finger tapping in patients with schizophrenia using the newly available imaging method of functional magnetic resonance imaging (fMRI). Nine patients with DSMIII-R schizophrenia and 9 well-matched healthy volunteer subjects underwent fMRI examination on a conventional MR unit; activation of the primary motor cortex was evaluated during performance of a finger motion task. Localized activation of the motor cortex was observed in 17 of 18 subjects during fMRI. Patients and controls were, however, indistinguishable with respect to signal intensity or area thereof within the motor cortex. fMRI did not reveal motor cortical dysfunction in schizophrenia. Despite its infancy, fMRI holds considerable promise to advance understanding of the neurodynamics of psychiatric disorders, particularly schizophrenia.

What have we learned from functional imaging studies in schizophrenia? The role of frontal, striatal and temporal areas

OBJECTIVES

Functional imaging technologies allow assessment of cerebral blood flow, cerebral metabolism, cellular metabolic processes, cerebral receptor density and occupancy. This review examines the contribution of such studies to our understanding of schizophrenia. The role of the frontal lobes, the basal ganglia, the temporal lobes and the neuronal circuits which connect them is examined with respect to this literature.

METHOD

All studies in schizophrenia using positron emission tomography, single photon emission computerised tomography, xenon studies, functional and spectroscopic magnetic resonance imaging formed the basis of this review. Only those studies published in English were reviewed.

RESULTS

The most consistent finding in schizophrenia has been that of hypofrontality, while the results of studies examining subcortical structures provide preliminary support for the concept of fronto-striatal dysfunction. Functional imaging has not yet provided consistent results in the study of temporal lobe function. Although receptor studies have shed light on the actions of antipsychotic medications, the findings for dopamine receptor numbers remain controversial. Spectroscopic and functional MRI remain in their infancy as research tools in schizophrenia.

CONCLUSIONS

Although there are significant methodological issues to be addressed, functional imaging technology is providing increasing insights into schizophrenia and its treatment. Future research will be truly multidisciplinary as it will require the collaboration of psychiatrists, imaging physicians, neuropsychologists and neuroscientists.

Functional magnetic resonance imaging at 1 T: motor cortex, supplementary motor area and visual cortex activation

Functional activation of the brain has been visualized using magnetic resonance imaging (MRI). Early studies used echo planar imaging and magnetic fields of 2 T and above. However, recent studies have successfully shown the activation of visual and motor areas of the brain using conventional clinical 1.5 T MRI systems. The purpose of the present study was to replicate these studies at a lower field strength. Eight motor and two visual activation studies were performed using a 1 T clinical scanner. Activation was seen in the contralateral motor cortex during motor stimulation in six of the eight volunteers. Activation was also documented within the contralateral supplementary motor area in four of the six volunteers with motor cortex activation. The supplementary motor area was located in the posteromedial aspect of the superior frontal gyrus. Both volunteers subjected to photic stimulation showed activation within the visual cortex. Results show that functional imaging can be successfully carried out with a 1 T clinical scanner. The size of the image intensity on activation change suggests that contrast may not be due solely to susceptibility changes.

Some methodological issues in neuroradiological research in psychiatry

An outline is given of some of the methodological issues discussed in neuroradiological research on psychiatric illness. Strengths and shortcomings of magnetic resonance imaging (MRI) in depicting and quantifying brain structures are described. Temporal lobe anatomy and pathology are easily accessible to MRI, whereas limits on anatomical delineation hamper approaches to frontal lobe study. White matter hyperintense lesions are sensitively depicted by MRI, but specificity is limited. Distinction of vascular and primary degenerative dementia is considerably improved by CT and MRI analysis. Computed tomography (CT) and MRI have enhanced the understanding of treatable organic psychiatric disorders, e.g., normal pressure hydrocephalus. Subcortical and white matter pathology has been replicated in CT and MRI studies of late-onset psychiatric disorders, clinical overlap with cerebrovascular disease or neurodegeneration may be of import. Transcranial sonography findings of brainstem structural change specific to unipolar depression may contribute to the understanding of affective psychoses. Magnetic resonance spectroscopy and functional MRI are likely to stimulate psychiatric research in the future.

Is there a distinct subtype of major depression in the elderly?

Evidence for and against the notion of a specific subtype of depressive illness in the elderly is reviewed. There is little to support a distinction based on clinical features, neurobiological markers, treatment response or prognosis, but subtle organic cerebral change may predispose to late-onset depression in a significant minority of cases.