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Behavioral and neuroimaging evidence for a contribution of color and texture information to scene classification in a patient with visual form agnosia.

A common notion is that object perception is a necessary precursor to scene perception. Behavioral evidence suggests, however, that scene perception can operate independently of object perception. Further, neuroimaging has revealed a specialized human cortical area for viewing scenes that is anatomically distinct from areas activated by viewing objects. Here we show that an individual with visual form agnosia, D.F., who has a profound deficit in object recognition but spared color and visual texture perception, could still classify scenes and that she was fastest when the scenes were presented in the appropriate color. When scenes were presented as black-and-white images, she made a large number of errors in classification. Functional magnetic resonance imaging revealed selective activation in the parahippocampal place area (PPA) when D.F. viewed scenes. Unlike control observers, D.F. demonstrated higher activation in the PPA for scenes presented in the appropriate color than for black-and-white versions. The results demonstrate that an individual with profound form vision deficits can still use visual texture and color to classify scenes-and that this intact ability is reflected in differential activation of the PPA with colored versions of scenes.

Adult↗

Multimodality neuroimaging: research and clinical applications.

This manuscript reviews the current stance and the pertinent problems of transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) as brain mapping methodologies. The missing structure-function relation limits the use of TMS, whereas the uncertainty about the functional significance of activated cortical regions might render interpretation of fMRI studies difficult. Advances in image processing, however, allowed for 3- dimensional real-time visual guidance of TMS and integration with fMRI data. We describe the method used to coregister TMS and fMRI and present examples where a multimodality neuroimaging approach might add to our understanding of normal and pathological brain function.

Brain Mapping↗

Drug addiction and its underlying neurobiological basis: neuroimaging evidence for the involvement of the frontal cortex.

OBJECTIVE: Studies of the neurobiological processes underlying drug addiction primarily have focused on limbic subcortical structures. Here the authors evaluated the role of frontal cortical structures in drug addiction. METHOD: An integrated model of drug addiction that encompasses intoxication, bingeing, withdrawal, and craving is proposed. This model and findings from neuroimaging studies on the behavioral, cognitive, and emotional processes that are at the core of drug addiction were used to analyze the involvement of frontal structures in drug addiction. RESULTS: The orbitofrontal cortex and the anterior cingulate gyrus, which are regions neuroanatomically connected with limbic structures, are the frontal cortical areas most frequently implicated in drug addiction. They are activated in addicted subjects during intoxication, craving, and bingeing, and they are deactivated during withdrawal. These regions are also involved in higher-order cognitive and motivational functions, such as the ability to track, update, and modulate the salience of a reinforcer as a function of context and expectation and the ability to control and inhibit prepotent responses. CONCLUSIONS: These results imply that addiction connotes cortically regulated cognitive and emotional processes, which result in the overvaluing of drug reinforcers, the undervaluing of alternative reinforcers, and deficits in inhibitory control for drug responses. These changes in addiction, which the authors call I-RISA (impaired response inhibition and salience attribution), expand the traditional concepts of drug dependence that emphasize limbic-regulated responses to pleasure and reward.

Behavior, Addictive↗

Brain neuroimaging in cannabis use: a review.

In this study, the authors systematically reviewed structural and functional neuroimaging studies of cannabis use. Structural abnormalities generally have not been identified with chronic use. Regular users demonstrate reciprocal changes in brain activity globally and in cerebellar and frontal regions. Abstinence results in decreases, and administration results in increases correlating with subjective intoxication. Chronic use and cannabis administration result in attenuated brain activity in task-activated regions or activation of compensatory regions. Findings correlate partially with neuropsychological data, but generalization is limited by the lack of use of diagnostic criteria, appropriately paired neuropsychological testing or means to better quantify cannabis use and abstinence.

Animals↗

The emerging dialogue between psychoanalysis and neuroscience: neuroimaging perspectives.

Current progress in the cognitive neurosciences is highly relevant to the development of psychoanalytic theory and practice. Neuroscience is today becoming mature enough to provide empirical biological approaches for the investigation of psychoanalytic models and observations. The current state of functional neuroimaging techniques is reviewed, selected paradigms and findings relevant to psychotherapy research are presented, and ways to pursue the dialogue between psychoanalysts and neuroscientists are discussed, as are some related obstacles and pitfalls. The emerging dialogue between psychoanalysts and neuroscientists may help not only to reestablish a solid position of psychodynamic theory and treatment in contemporary medicine, but also to bridge the division between "psychological" and "somatic" treatments, and gain important insights into the mind-brain relationship.

Brain↗

Brain mechanisms of sleep: contribution of neuroimaging techniques.

Functional brain neuroimaging essentially relies on two basic principles: functional segregation and functional interaction. Recent studies of the functional segregation of the human brain during sleep, using positron emission tomography and statistical parametric mapping, indicate that human brain function is organized in a very specific way in each state of vigilance. During slow wave sleep, the most deactivated areas are the upper brainstem, thalamic nuclei and basal forebrain; deactivation of the basal ganglia is also seen. In the cortex, the least active areas are the associative cortices of the frontal and parietal cortex. The anatomical extent of this deactivation remains uncertain. In rapid eye movement (REM) sleep there is significant activation of the dorsal tegmentum of the ponto-mesencephalic region and the thalamic nuclei. Within the cortex, the limbic areas (amygdala, hippocampus, orbito-frontal cortex and anterior cingulate cortex) are activated. In contrast, the associative areas of the frontal and parietal cortices are less active than other parts of the brain. The functional interactions between the amygdala and the temporal cortex during REM sleep differ markedly from those during other states of vigilance, and there is also an inverse relationship between the activities of the primary and secondary visual areas.

Brain↗

Studies of altered social cognition in neuropsychiatric disorders using functional neuroimaging.

In this paper, we review studies using functional neuroimaging to examine cognition in neuropsychiatric disorders. The focus is on social cognition, which is a topic that has received increasing attention over the past few years. A network of brain regions is proposed for social cognition that includes regions involved in processes relevant to social functioning (for example, self reference and emotion). We discuss the alterations of activity in these areas in patients with autism, depression, schizophrenia, and posttraumatic stress disorders in relation to deficits in social behaviour and symptoms. The evidence to date suggests that there may be some specificity of the brain regions involved in these 4 disorders, but all are associated with dysfunction in the amygdala and dorsal cingulate gyrus. Although there is much work remaining in this area, we are beginning to understand the complex interactions of brain function and behaviour that lead to disruptions of social abilities.

Brain↗

Comparative utility of technetium-99m hexamethylpropylenamine oxime single photon emission computed tomography (SPECT) with anatomic neuroimaging and electroencephalography (EEG) in childhood intractable epilepsy.

Intractable epilepsies pose a therapeutic challenge. Precise localization of the epileptic focus is imperative before planning surgical intervention. Functional imaging is an important component of presurgical work-up. Positron emission tomography is unavailable in developing countries; hence, the need to evaluate the available imaging modality, single photon emission computed tomography (SPECT), was felt. We investigated 61 children with intractable epilepsy, identified by predefined criteria, by performing electroencephalography (EEG), magnetic resonance imaging (MRI), computed tomography (CT), and ictal and interictal SPECT. The localizing value of ictal and interictal SPECT imaging for epileptic foci was correlated with clinical, electrophysiologic, and anatomic neuroimaging data. An ictal SPECT was obtained in 9, and interictal SPECT was performed in all (61). Ictal SPECT was localizing in 8 of 9 (88.8%). Interictal SPECT was localizing in a significantly higher proportion of patients (47.54%) than either the scalp EEG (16.39%) (P = .0003) or CT scan (21.56%) (P = .0046). Our data demonstrated that interictal and ictal SPECT identified more focal changes in children with intractable epilepsy than interictal EEG, CT, and probably MRI. The definitive proof of the SPECT-based findings being epileptogenic foci awaits correlation with intraoperative monitoring and postoperative follow-up.

Adolescent↗

Neuroimaging in spasticity and movement disorders.

Advances in neuroimaging provide unique opportunities to evaluate brain structure, biochemistry, and function. Although a number of imaging techniques have been used in newborns, cranial ultrasonography in premature infants and nuclear magnetic resonance modalities, including magnetic resonance imaging and diffusion-weighted imaging, in high-risk term infants are of foremost benefit. Interpretation is based on knowledge of characteristic imaging findings in specific childhood neurologic disorders and an understanding of differential diagnosis in cerebral palsy syndromes, such as spastic diplegia and various subtypes of extrapyramidal cerebral palsy. This review focuses on imaging studies that can be effectively used in at-risk infants and in children with spasticity and movement disorders to refine diagnosis and guide therapeutic interventions.

Brain↗

Neuroimaging in leukodystrophies.

The application of techniques based on in vivo magnetic resonance to the study of leukodystrophies is evaluated. Magnetic resonance imaging (MRI), the most important neuroimaging modality for patients with leukodystrophies, has proven invaluable for the detection of the extent and etiology of white-matter involvement, diagnosis, and monitoring of disease progression. Proton magnetic resonance spectroscopy, which can detect several brain metabolites, including those related to axonal function and myelination, can provide additional diagnostic and prognostic information and, in some cases, allows a rare insight into the biochemical pathology of leukodystrophies. The potential of other advanced magnetic resonance techniques, including diffusion tensor imaging, magnetization transfer contrast, and molecular imaging, is also discussed. In the future, anatomic and physiologic magnetic resonance techniques are expected to be integrated into a single examination that will provide a detailed characterization of white-matter diseases in children.

Brain↗

Neuroimaging in cerebral palsy: Patterns of brain dysgenesis and injury.

Despite advances in obstetric and neonatal care, the overall prevalence of cerebral palsy has remained stable, supporting the belief that pathogenesis is primarily due to prenatal brain dysgenesis and injury. Neuroimaging studies have consistently shown abnormalities in 70% to 90% of affected children, facilitating clinical classification into groups with early brain malformations, white-matter injury, neonatal encephalopathies, and a heterogeneous group of postnatally acquired disorders. White-matter injury, well seen on conventional magnetic resonance imaging (MRI), is the leading cause of cerebral palsy in children born preterm. As many as 20% of very low birthweight infants have cystic and/or diffuse white-matter injury, termed periventricular leukomalacia, with evidence of associated pathology in other cortical and subcortical structures. In the group with acute, term perinatal pathology, a variety of imaging modalities, in addition to MRI, have diagnostic utility. In general, when added to conventional MRI, advanced techniques, such as diffusion tensor imaging, diffusion-weighted imaging, and magnetic resonance spectroscopy, provide a more complete picture of structural and functional brain abnormalities. The results have led to improved understanding of pathogenesis, especially in regard to periventricular leukomalacia and hypoxic-ischemic encephalopathy. This information might lead to interventions preventing brain injury in preterm infants and asphyxiated term newborns.

Brain↗

Neuroimaging of Tourette syndrome.

Traditional neuropathologic methods have provided only limited insight into the central nervous system abnormalities underlying Tourette syndrome. In the past 20 years, investigators have turned increasingly to in vivo neuroimaging approaches to localize, quantify, and characterize neuroanatomic, functional, and neurochemical distinctions in living subjects with Tourette syndrome. Research methods have included aggregate measures of cerebral energy metabolism, assessments of cerebral structure and size, and highly specific assessments of neurochemical markers of select neurons and synapses. Although the available data have important limitations, an encouraging convergence of findings implicates abnormal function in the Tourette syndrome striatum and in associated limbic and frontal cortical systems.

Brain↗

Colpocephaly: pitfalls in the diagnosis of a pathologic entity utilizing neuroimaging techniques.

Colpocephaly has been described as the persistence of the fetal configuration of the lateral ventricles. The pathologic picture is characterized by multiple features of disturbed or arrested development of the brain, which results in diminished thickness of the cerebral white matter in the posterior portion of the centrum semiovale, giving rise to large occipital horns of the lateral ventricles. This ventricular configuration allows the clinician to suspect the presence of this developmental disturbance utilizing computed tomographic images. In this paper, we present a case that demonstrates that not every patient with enlargement of the posterior horns of the lateral ventricles has the underlying developmental abnormalities that constitute colpocephaly as described by Yakovlev and Wadsworth. Furthermore, we point out the difficulties that can arise in the attempt to make a diagnosis of a pathologically defined condition on the basis of neuroimaging results alone.

Cerebral Palsy↗

Performance on the Mattis Dementia Rating Scale in patients with vascular dementia: relationships to neuroimaging findings.

Impairment on screening measures such as the Mattis Dementia Rating Scale (MDRS) provides evidence of dementia in patients with cerebrovascular disease. However, the relationships between neuroimaging findings and performance on the MDRS in vascular dementia (VD) have not been determined. In the present study, we examined the relationships between subcortical hyperintensity (SH) volume and whole brain volume (WBV) on the subscales and total score of the MDRS. Results revealed that SH accounted for a significant amount of variance on the Initiation/Perseveration and Construction subscales, whereas WBV accounted for a significant amount of variance on the Memory subscale. The total score on the MDRS was found to be significantly related to WBV but not SH. These results suggest that subcortical damage and brain volume account for different aspects of cognitive decline in VD and that overall cognitive impairment may reflect cortical and subcortical involvement.

Aged↗

Reduplicative paramnesia: longitudinal neurobehavioral and neuroimaging analysis.

Reduplicative paramnesia (RP) is a delusion in which the patient perceives familiar places, objects, or events to have been duplicated. The current case describes the development of RP in an 81-year-old male following a large right frontal lobe infarction. As the patient had been hospitalized previously with hemorrhagic contusions, neurologic, neuropsychological, and neuroimaging data were obtained both prior to and following RP onset. Psychophysiologic data were obtained following the development of the delusion. Both premorbidly and at follow-up, neuropsychological functioning was characterized by significant impairments of learning and memory and frontal-executive functions. Language and visuospatial skills and motor speed were intact both before and after RP onset. The case is described within the context of preexisting theories of RP, and it is surmised that the delusion is secondary to temporal-limbic-frontal dysfunction giving rise to a distorted sense of familiarity and impaired ability to resolve the delusion via reasoning.

Accidental Falls↗

Statistical methods in neuroimaging with particular application to emission tomography.

We review statistical methods being applied in four key areas connected with PET and SPECT neuroimaging: (i) image reconstruction (briefly); (ii) tracer-kinetic, or compartmental, modelling; (iii) inference from region-of-interest data; (iv) inference at the pixel or voxel level. Under the last heading, we pay particular attention to the analysis of data from serial scans. We conclude by identifying some topics for future statistical research.

Algorithms↗

The endophenotype of impulsivity: reaching consilience through behavioral, genetic, and neuroimaging approaches.

Impulsivity is a multidimensional construct with implications for understanding the etiology and treatment of multiple forms of psychopathology. As a multidimensional construct, however, the processes underlying impulsivity, particularly behavioral inhibition, must be separated to allow for investigations into its neurogenetic bases. Evidence from both animal and human studies supports the role of dopamine in impulsivity, and neuroimaging research is elucidating brain regions involved in behavioral inhibition. Evidence is now emerging that suggests an interaction between dopamine system genes and frontal brain regions in underlying individual differences in behavioral inhibition. However, to reach a comprehensive understanding of the neurogenetic bases of behavioral inhibition, an appropriate framework is required. Therefore, it is proposed that by identifying intervening variables more sensitive to the effects of genetic variation, known as an endophenotype approach, we will be able to overcome many of the methodological limitations that prevent a better understanding at present.

Adult↗

Callosal anomalies in patients with spinal dysraphism: correlation of clinical and neuroimaging features with hemispheric abnormalities.

Dysgenesis of the corpus callosum can occur in association with spinal dysraphic lesions. Clinical and neuroimaging features were reviewed in 23 patients (12 male, 11 female; mean age 11.3 years) with caudal spinal dysraphism (myeloschisis in eight, meningomyelocele in 10, and lumbosacral lipoma in five) to characterize types and degrees of callosal and other cerebral anomalies. T1- and T2-weighted magnetic resonance images were obtained, and the total midsagittal cross-sectional area of the corpus callosum was determined. The corpus callosum appeared normal in nine patients and was abnormal in 14. In five patients the corpus callosum was narrow, with all regions present; the cerebral hemispheres were hypoplastic. Two patients with dysgenesis of frontal, parietal, and occipital lobes had a small, partly agenetic corpus callosum. In the remaining seven patients the posterior third of the corpus callosum was absent or hypoplastic; six of them had ventriculomegaly that selectively affected the occipital horns (colpocephaly). All callosal anomalies were accompanied by hemispheric ones. This supports a disordered developmental relationship between the corpus callosum and the hemispheres as a cause. Spinal dysraphism can no longer be considered a single developmental abnormality, given the frequent association of other defects.

Adolescent↗