An MRI method for parcellating the human striatum into matrix and striosome compartments in vivo.

The mammalian striatum is comprised of intermingled tissue compartments, matrix and striosome. Though indistinguishable by routine histological techniques, matrix and striosome have distinct embryologic origins, afferent/efferent connections, surface protein expression, intra-striatal location, susceptibilities to injury, and functional roles in a range of animal behaviors. Distinguishing the compartments previously required post-mortem tissue and/or genetic manipulation; we aimed to identify matrix/striosome non-invasively in living humans. We used diffusion MRI (probabilistic tractography) to identify human striatal voxels with connectivity biased towards matrix-favoring or striosome-favoring regions (determined by prior animal tract-tracing studies). Segmented striatal compartments replicated the topological segregation and somatotopic organization identified in animal matrix/striosome studies. Of brain regions mapped in prior studies, our human brain data confirmed 93% of the compartment-selective structural connectivity demonstrated in animals. Test-retest assessment on repeat scans found a voxel classification error rate of 0.14%. Fractional anisotropy was significantly higher in matrix-like voxels, while mean diffusivity did not differ between the compartments. As mapped by the Talairach human brain atlas, 460 regions were significantly biased towards either matrix or striosome. Our method allows the study of striatal compartments in human health and disease, in vivo, for the first time.

BDNF, relative preference, and reward circuitry responses to emotional communication.

Brain derived neurotrophic factor (BDNF) regulates neural development and synaptic transmission. We have tested the hypothesis that functional variation in the BDNF gene (Val66Met polymorphism, rs6265) affects brain reward circuitry encoding human judgment and decision-making regarding relative preference. We quantified relative preference among faces with emotional expressions (angry, fearful, sad, neutral, and happy) by a keypress procedure performed offline to measure effort traded for viewing time. Keypress-based relative preferences across the ensemble of faces were mirrored significantly by fMRI signal in the orbitofrontal cortex, amygdala, and hippocampus when passively viewing these faces. For these three brain regions, there was also a statistically significant group difference by BDNF genotype in the fMRI responses to the emotional expressions. In comparison with Val/Met heterozygotes, Val/Val individuals preferentially sought exposure to positive emotions (e.g., happy faces) and had stronger regional fMRI activation to aversive stimuli (e.g., angry, fearful, and sad faces). BDNF genotype accounted for approximately 30% of the variance in fMRI signal that mirrors keypress responses to these stimuli. This study demonstrates that functional allelic variation in BDNF modulates human brain circuits processing reward/aversion information and relative preference transactions.

Reward circuitry activation by noxious thermal stimuli.

Using functional magnetic resonance imaging (fMRI), we observed that noxious thermal stimuli (46 degrees C) produce significant signal change in putative reward circuitry as well as in classic pain circuitry. Increases in signal were observed in the sublenticular extended amygdala of the basal forebrain (SLEA) and the ventral tegmentum/periaqueductal gray (VT/PAG), while foci of increased signal and decreased signal were observed in the ventral striatum and nucleus accumbens (NAc). Early and late phases were observed for signals in most brain regions, with early activation in reward related regions such as the SLEA, VT/PAG, and ventral striatum. In contrast, structures associated with somatosensory perception, including SI somatosensory cortex, thalamus, and insula, showed delayed activation. These data support the notion that there may be a shared neural system for evaluation of aversive and rewarding stimuli.

Functional imaging of neural responses to expectancy and experience of monetary gains and losses.

Neural responses accompanying anticipation and experience of monetary gains and losses were monitored by functional magnetic resonance imaging. Trials comprised an initial "prospect" (expectancy) phase, when a set of three monetary amounts was displayed, and a subsequent "outcome" phase, when one of these amounts was awarded. Hemodynamic responses in the sublenticular extended amygdala (SLEA) and orbital gyrus tracked the expected values of the prospects, and responses to the highest value set of outcomes increased monotonically with monetary value in the nucleus accumbens, SLEA, and hypothalamus. Responses to prospects and outcomes were generally, but not always, seen in the same regions. The overlap of the observed activations with those seen previously in response to tactile stimuli, gustatory stimuli, and euphoria-inducing drugs is consistent with a contribution of common circuitry to the processing of diverse rewards.

Beautiful faces have variable reward value: fMRI and behavioral evidence.

The brain circuitry processing rewarding and aversive stimuli is hypothesized to be at the core of motivated behavior. In this study, discrete categories of beautiful faces are shown to have differing reward values and to differentially activate reward circuitry in human subjects. In particular, young heterosexual males rate pictures of beautiful males and females as attractive, but exert effort via a keypress procedure only to view pictures of attractive females. Functional magnetic resonance imaging at 3 T shows that passive viewing of beautiful female faces activates reward circuitry, in particular the nucleus accumbens. An extended set of subcortical and paralimbic reward regions also appear to follow aspects of the keypress rather than the rating procedures, suggesting that reward circuitry function does not include aesthetic assessment.

Response and habituation of the human amygdala during visual processing of facial expression.

We measured amygdala activity in human volunteers during rapid visual presentations of fearful, happy, and neutral faces using functional magnetic resonance imaging (fMRI). The first experiment involved a fixed order of conditions both within and across runs, while the second one used a fully counterbalanced order in addition to a low level baseline of simple visual stimuli. In both experiments, the amygdala was preferentially activated in response to fearful versus neutral faces. In the counterbalanced experiment, the amygdala also responded preferentially to happy versus neutral faces, suggesting a possible generalized response to emotionally valenced stimuli. Rapid habituation effects were prominent in both experiments. Thus, the human amygdala responds preferentially to emotionally valenced faces and rapidly habituates to them.

Acute effects of cocaine on human brain activity and emotion.

We investigated brain circuitry mediating cocaine-induced euphoria and craving using functional MRI (fMRI). During double-blind cocaine (0.6 mg/kg) and saline infusions in cocaine-dependent subjects, the entire brain was imaged for 5 min before and 13 min after infusion while subjects rated scales for rush, high, low, and craving. Cocaine induced focal signal increases in nucleus accumbens/subcallosal cortex (NAc/SCC), caudate, putamen, basal forebrain, thalamus, insula, hippocampus, parahippocampal gyrus, cingulate, lateral prefrontal and temporal cortices, parietal cortex, striate/extrastriate cortices, ventral tegmentum, and pons and produced signal decreases in amygdala, temporal pole, and medial frontal cortex. Saline produced few positive or negative activations, which were localized to lateral prefrontal cortex and temporo-occipital cortex. Subjects who underwent repeat studies showed good replication of the regional fMRI activation pattern following cocaine and saline infusions, with activations on saline retest that might reflect expectancy. Brain regions that exhibited early and short duration signal maxima showed a higher correlation with rush ratings. These included the ventral tegmentum, pons, basal forebrain, caudate, cingulate, and most regions of lateral prefrontal cortex. In contrast, regions that demonstrated early but sustained signal maxima were more correlated with craving than with rush ratings; such regions included the NAc/SCC, right parahippocampal gyrus, and some regions of lateral prefrontal cortex. Sustained negative signal change was noted in the amygdala, which correlated with craving ratings. Our data demonstrate the ability of fMRI to map dynamic patterns of brain activation following cocaine infusion in cocaine-dependent subjects and provide evidence of dynamically changing brain networks associated with cocaine-induced euphoria and cocaine-induced craving.

Synergistic effects of the dopaminergic and glutamatergic system on hippocampal volume in alcohol-dependent patients.

Several genes of the dopaminergic and glutamatergic neurotransmitter systems have been found to be associated with alcohol disease and related intermediate phenotypes. Here, we evaluated genetic variants of the catechol-O-methyltransferase (COMT) and the metabotropic glutamate receptor 3 (mGluR3) genes in alcohol-dependent patients and their association with volumetric measurements of brain structures. By combined analysis of imaging data and genotyping results, large numbers of variables are produced that overstrain conventional statistical methods based on tests for group differences. Limitations in assessment of epistatic effects and multiple testing problems are encountered. Therefore, we introduce a novel method for detecting associations between a set of genetic markers and phenotypical measurements based on machine learning techniques. Hippocampal volume was found to be associated with epistatic effects of the COMT-mGluR3 genes in alcohol-dependent patients but not in controls. These data are in line with prior studies supporting a role for dopamine-glutamate interaction in modulation of alcohol disease.

Regional cerebral blood flow measured during symptom provocation in obsessive-compulsive disorder using oxygen 15-labeled carbon dioxide and positron emission tomography.

BACKGROUND: The study was designed to determine the mediating neuroanatomy of obsessive-compulsive disorder (OCD). METHODS: The short half-life tracer oxygen 15-labeled carbon dioxide was used to allow for repeated positron emission tomographic determinations of regional cerebral blood flow on each of eight patients with OCD during a resting and a provoked (symptomatic) state. RESULTS: Individually tailored provocative stimuli were successful in provoking OCD symptoms, in comparison with paired innocuous stimuli, as measured by self-report on OCD analogue scales (P = .002). Omnibus subtraction images demonstrated a statistically significant increase in relative regional cerebral blood flow during the OCD symptomatic state vs the resting state in right caudate nucleus (P < .006), left anterior cingulate cortex (P < .045), and bilateral orbitofrontal cortex (P < .008); increases in the left thalamus approached but did not reach statistical significance (P = .07). CONCLUSIONS: These findings are consistent with results of previous functional neuroimaging studies and contemporary neurocircuitry models of OCD. The data further implicate orbitofrontal cortex, caudate nucleus, and anterior cingulate cortex in the pathophysiology of OCD and in mediating OCD symptoms.

A positron emission tomographic study of simple phobic symptom provocation.

BACKGROUND: The goal of this study was to determine the mediating neuroanatomy of simple phobic symptoms. METHODS: Positron emission tomography and oxygen 15 were used to measure normalized regional cerebral blood flow in seven subjects with simple phobia during control and provoked states. Stereotactic transformation and statistical parametric mapping techniques were employed to determine the locations of significant activation. RESULTS: Statistical parametric maps demonstrated significant increases in normalized regional blood flow for the symptomatic state compared with the control state in the anterior cingulate cortex, the insular cortex, the anterior temporal cortex, the somatosensory cortex, the posterior medial orbitofrontal cortex, and the thalamus. CONCLUSIONS: The results suggest that anxiety associated with the simple phobic symptomatic state is mediated by paralimbic structures. Moreover, activation of somatosensory cortex may reflect tactile imagery as one component of the phobic symptomatic condition.

Cerebral structural abnormalities in obsessive-compulsive disorder. A quantitative morphometric magnetic resonance imaging study.

BACKGROUND: A previous pilot study of only posterior brain regions found lower white-matter volume in patients with obsessive-compulsive disorder than in normal control subjects. We used new cohorts of patients and matched normal control subjects to study whole-brain volume differences between these groups with magnetic resonance imaging-based morphometry. METHODS: Ten female patients with obsessive-compulsive disorder and 10 female control subjects, matched for handedness, age, weight, education, and verbal IQ, underwent magnetic resonance imaging with a 3-dimensional volumetric protocol. Scans were blindly normalized and segmented by means of well-characterized semiautomated intensity contour mapping and differential intensity contour algorithms. Brain structures investigated included the cerebral hemispheres, cerebral cortex, diencephalon, caudate, putamen, globus pallidus, hippocampus amygdala, third and fourth ventricles, corpus callosum, operculum, cerebellum, and brain stem. Anterior to posterior neocortical regions, including precallosum, anterior pericallosum, posterior pericallosum, and retrocallosum, with adjacent white matter were also measured. Volumes found different between groups were correlated with Yale-Brown Obsessive Compulsive Scale score and Rey-Osterieth Complex Figure Test measures. RESULTS: Confirming results of our earlier pilot study and expanding the findings to the whole brain, patients with obsessive-compulsive disorder had significantly less total white matter but, in addition, significantly greater total cortex and opercular volumes. Severity of obsessive-compulsive disorder and nonverbal immediate memory correlated with opercular volume. CONCLUSIONS: Replication of volumetric white-matter differences suggests a widely distributed structural brain abnormality in obsessive-compulsive disorder. Whereas determining the etiogenesis may require research at a microscopic level, understanding its functional significance can be further explored via functional neuroimaging and neuropsychological studies.

Functional magnetic resonance imaging of symptom provocation in obsessive-compulsive disorder.

BACKGROUND: The new technique of functional magnetic resonance imaging was used to investigate the mediating neuroanatomy of obsessive-compulsive disorder symptoms. METHODS: Ten patients with obsessive-compulsive disorder and 5 normal subjects were studied via functional magnetic resonance imaging during control and provoked conditions. Data analysis entailed parametric and nonparametric statistical mapping. RESULTS: Statistical maps (nonparametric; P < 10(-3)) showed activation for 70% or more of patients with obsessive-compulsive disorder in medial orbitofrontal, lateral frontal, anterior temporal, anterior cingulate, and insular cortex, as well as caudate, lenticulate, and amygdala. No normal subjects exhibited activation in any brain region. CONCLUSIONS: Results of functional magnetic resonance imaging were consistent with past studies of obsessive-compulsive disorder that used other functional neuroimaging modalities. However, paralimbic and limbic activations were more prominent in the present study.

Clinical outcomes following cocaine infusion in nontreatment-seeking individuals with cocaine dependence.

BACKGROUND: In this study we explored if laboratory-based cocaine administration to human subjects was associated with long-term adverse outcomes. METHODS: Twenty-one non--reatment seeking individuals with cocaine dependence were evaluated at baseline and again 5 and 10 months following cocaine infusion in a brain imaging study. Outcomes included computer-driven multidimensional clinical assessments and radioimmunoassay of hair. For comparison, identical data were collected from 19 cocaine-dependent subjects who did not receive the infusion. RESULTS: The infused and noninfused groups did not differ on frequency of cocaine use (corroborated by radioimmunoassay of hair), Addiction Severity Index drug composite score, or Hamilton Rating Scale for Depression score at both follow-up time points. In a time-related trend analysis, both groups showed significant reductions in frequency of cocaine use. CONCLUSIONS: Laboratory-based cocaine administration can be a safe paradigm even in individuals who are not engaged in treatment.

Reduced basal ganglia volumes in trichotillomania measured via morphometric magnetic resonance imaging.

A morphometric magnetic resonance imaging (MRI) study compared volumes of brain structures in 10 female subjects with trichotillomania (repetitive hair-pulling) versus 10 normal controls matched for sex, age, handedness, and education. Three-dimensional MRI scans were blindly normalized and segmented using well-characterized semiautomated intensity and differential contour algorithms by signal intensity-frequency histograms. Consistent with one a priori hypothesis, left putamen volume was found to be significantly smaller in trichotillomania subjects as compared with normal matched controls. This is the first report of a structural brain abnormality in trichotillomania. Results are discussed in terms of putative relationships between trichotillomania, Tourette's syndrome, and obsessive-compulsive disorder.

Cocaine decreases cortical cerebral blood flow but does not obscure regional activation in functional magnetic resonance imaging in human subjects.

The authors used functional magnetic resonance imaging (fMRI) to determine whether acute intravenous (i.v.) cocaine use would change global cerebral blood flow (CBF) or visual stimulation-induced functional activation. They used flow-sensitive alternating inversion recovery (FAIR) scan sequences to measure CBF and blood oxygen level-dependent (BOLD) sensitive T2* scan sequences during visual stimulation to measure neuronal activation before and after cocaine and saline infusions. Cocaine (0.6 mg/kg i.v. over 30 seconds) increased heart rate and mean blood pressure and decreased end tidal carbon dioxide (CO2). All measures returned to baseline by 2 hours, the interinfusion interval, and were unchanged by saline. Flow-sensitive alternating inversion recovery imaging demonstrated that cortical gray matter CBF was unchanged after saline infusion (-2.4 +/- 6.5%) but decreased (-14.1 +/- 8.5%) after cocaine infusion (n = 8, P < 0.01). No decreases were detected in white matter, nor were changes found comparing BOLD signal intensity in cortical gray matter immediately before cocaine infusion with that measured 10 minutes after infusion. Visual stimulation resulted in comparable BOLD signal increases in visual cortex in all conditions (before and after cocaine and saline infusion). Despite a small (14%) but significant decrease in global cortical gray matter CBF after acute cocaine infusion, specific regional increases in BOLD imaging, mediated by neurons, can be measured reliably.

Pharmacokinetics of N-acetylprocainamide in patients profiled with a stable isotope method.

N-Acetylprocainamide (NAPA) absorption and disposition were profiled in five patients with ventricular arrhythmias by the simultaneous intravenous administration of NAPA-13C and oral administration of a 500 mg NAPA hydrochloride tablet. NAPA distribution was modeled with a three compartment mammillary system. The central compartment volume of 14.1 +/- 2.6 L (mean +/- SD) was similar to expected intravascular space, corrected for NAPA partitioning between erythrocytes and plasma. Other compartment volumes, intercompartmental and nonrenal clearances, and the steady-state distribution volume of 1.45 +/- 0.09 L/kg were similar to normal subject values. The least-squares estimate of 1.67 for the NAPA renal clearance/creatinine clearance ratio was similar to the value of 1.68 previously reported for functionally anephric patients and showed the expected age-associated decrease. The oral NAPA dose was 78.0% +/- 11.7% absorbed and interindividual variation in NAPA absorption was correlated with fast intercompartmental clearance (r = 0.89, p = 0.045). Because fast intercompartmental clearance partly reflects splanchnic blood flow, hemodynamic changes may affect NAPA bioavailability, as has been found for procainamide.

Functional magnetic resonance imaging of brain reward circuitry in the human.

To produce behavior, motivational states necessitate at least three fundamental operations, including (1) selection of objectives focused on goal-objects, (2) compilation of goal-object information, and (3) determination of physical plans for securing goal-objects. The second of these general operations has been theorized to involve three subprocesses: (a) feature detection and other perceptual processing of putative goal-object "rewards," (b) valuation of goal-object worth in the context of potential hedonic deficit states, and (c) extraction of incidence and temporal data regarding the goal-object. A number of subcortical brain regions appear to be involved in these three informational subprocesses, in particular, the amygdala, sublenticular extended amygdala (SLEA) of the basal forebrain, and nucleus accumbens/subcallosal cortex (NAc/SCC). Components of the amygdala, SLEA, and NAc/SCC together constitute the larger anatomic structure of the extended amygdala. Functional magnetic resonance imaging (fMRI) studies of humans have recently begun to localize these subcortical regions within the extended amygdala during specific experimental conditions. In this manuscript, two human cocaine- infusion studies and one cognitive psychology experiment are reviewed in relation to their pattern of fMRI activation within regions of the extended amygdala. Activation in the NAc/SCC, in particular, is evaluated in relation to a hypothesis that one function of the NAc/SCC and associated brain regions is the evaluation of goal-object incidence data for the computation of conditional probabilities regarding goal-object availability. Further work is warranted to test hypothesized functions for all regions within the extended amygdala and integrate them toward an understanding of motivated behavior.

Acute plasticity in the human somatosensory cortex following amputation.

We studied a patient after amputation of an arm and found that in less than 24 h stimuli applied on the ipsilateral face were referred in a precise, topographically organized, modality-specific manner to distinct points on the phantom. Functional magnetic resonance imaging (fMRI) performed one month later showed that brush-evoked activity in the brain demonstrates objective signal changes which correlate with perceptual changes in the phantom hand. This finding in humans corresponds to the observations of immediate plasticity in cortical pathways described in animals, including primates. The results suggest that reorganization of sensory pathways occurs very soon after amputation in humans, potentially due to the unmasking of ordinarily silent inputs rather than sprouting of new axon terminals.

Noxious hot and cold stimulation produce common patterns of brain activation in humans: a functional magnetic resonance imaging study.

We used functional magnetic resonance imaging (fMRI) to determine whether similar brain regions activate during noxious hot and cold stimulation. Six male subjects underwent whole brain fMRI during phasic delivery of noxious hot (46 degrees C) and noxious cold (5 degrees C) stimulation to the dorsum of the left hand. Mid-brain regions activated included thalamus, basal ganglia and insula. Cortical areas activated included cingulate, somatosensory, premotor and motor cortices, as well as prefrontal and inferior parietal cortex. Most regions activated bilaterally but with stronger activation contralateral to the stimulus. Noxious cold stimulation produced significantly increased volumes of activation compared to noxious heat in prefrontal areas only. Our results suggest a similar network of regions activate common to the perception of pain produced by either noxious hot or cold stimulation.

A functional magnetic resonance imaging study of auditory vigilance with low and high information processing demands.

This study identified the brain activations associated with auditory vigilance tasks, using functional magnetic resonance imaging. We created auditory continuous performance tests (CPTs) in which a demanding task (working memory task) was made more difficult than a simple vigilance task by increasing working memory and interference filtering demands. Two cohorts of normal male controls performed significantly worse on the working memory CPT than on the vigilance task. Compared to the vigilance task, performance of the working memory task produced significant signal change in lateral and medial prefrontal cortex, precentral cortex, temporal lobe, including insula and hippocampus, parietal-occipital cortex, cingulate, thalamus, and superior colliculus. Performance and degree of activation was associated with an estimate of IQ. Further research should clarify the contributions of working memory and interference filtering to the activated network.