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Daniel W Hommer

Publications and source records attributed to Daniel W Hommer.

9 recordsLinked to original sources
PubMed2006

Anticipating instrumentally obtained and passively-received rewards: a factorial fMRI investigation.

During functional magnetic resonance imaging (fMRI), subjects saw cues signaling probabilities of 1.0, 0.5, and 0 of winning $1 for hitting a subsequent target, and cues signaling similar probabilities of reward delivery requiring no instrumental response. Non-instrumental reward anticipation did not elicit activation. Instrumental reward anticipation activated multiple nodes of the basal ganglia-thalamocortical motor circuit. Ventromesial striatum was activated by joint requirement for an instrumental response together with uncertain (but not certain) reward.

Adult↗
PubMed2006

Single subject image analysis using the complex general linear model--an application to functional magnetic resonance imaging with multiple inputs.

A linear time invariant model is applied to functional fMRI blood flow data. Based on traditional time series analysis, this model assumes that the fMRI stochastic output sequence can be determined by a constant plus a linear filter (hemodynamic response function) of several fixed deterministic inputs and an error term assumed stationary with zero mean. The input function consists of multiple exponential distributed (time delay between images) visual stimuli consisting of negative and erotic images. No a priori assumptions are made about the hemodynamic response function that, in essence, is calculated at each spatial position from the data. The sampling rate for the experiment is 400 ms in order to allow for filtering out higher frequencies associated with the cardiac rate. Since the statistical analysis is carried out in the Fourier domain, temporal correlation problems associated with inference in the time domain are avoided. This formal model easily lends itself to further development based on previously developed statistical techniques.

Adult↗
PubMed2005

Childhood-onset schizophrenia: smooth pursuit eye-tracking dysfunction in family members.

BACKGROUND: Childhood-onset schizophrenia (COS), a severe form of the disorder, is of interest for etiologic studies. Smooth pursuit eye-tracking dysfunction (ETD) is a biological marker for schizophrenia. AIMS: To compare familial eye-tracking abnormalities for COS and adult-onset schizophrenia (AOS). METHOD: Eye-tracking performance for 70 COS parents, 64 AOS parents and 20 COS siblings was compared to their respective age-matched control groups. RESULTS: COS and AOS parents had higher rate of dichotomously rated eye-tracking dysfunction than their respective controls (16% vs. 1% and 22% vs. 4%, respectively). COS parents and siblings also differed from controls on several continuous measures. However, scores for COS, AOS and control groups overlapped extensively. CONCLUSIONS: Genetic factors underlying eye-tracking dysfunction appear more salient for COS. However, eye-tracking measures have to be used with caution for endophenotypic definition due to low predictive power. DECLARATION OF INTEREST: The study was done at the National Institutes of Health.

Adult↗
PubMed2004

Incentive-elicited brain activation in adolescents: similarities and differences from young adults.

Brain motivational circuitry in human adolescence is poorly characterized. One theory holds that risky behavior in adolescence results in part from a relatively overactive ventral striatal (VS) motivational circuit that readily energizes approach toward salient appetitive cues. However, other evidence fosters a theory that this circuit is developmentally underactive, in which adolescents approach more robust incentives (such as risk taking or drug experimentation) to recruit this circuitry. To help resolve this, we compared brain activation in 12 adolescents (12-17 years of age) and 12 young adults (22-28 years of age) while they anticipated the opportunity to respond to obtain monetary gains as well as to avoid monetary losses. In both age groups, anticipation of potential gain activated portions of the VS, right insula, dorsal thalamus, and dorsal midbrain, where the magnitude of VS activation was sensitive to gain amount. Notification of gain outcomes (in contrast with missed gains) activated the mesial frontal cortex (mFC). Across all subjects, signal increase in the right nucleus accumbens during anticipation of responding for large gains independently correlated with both age and self-rated excitement about the high gain cue. In direct comparison, adolescents evidenced less recruitment of the right VS and right-extended amygdala while anticipating responding for gains (in contrast with anticipation of nongains) compared with young adults. However, brain activation after gain outcomes did not appreciably differ between age groups. These results suggest that adolescents selectively show reduced recruitment of motivational but not consummatory components of reward-directed behavior.

Adolescent↗
PubMed2003

CSF monoamine metabolites and MRI brain volumes in alcohol dependence.

Correlations between cerebrospinal fluid (CSF) concentrations of monoamine metabolites (MAM) and brain structure have been described in schizophrenia, but not in alcoholism. To investigate the relationship between monoaminergic transmission and brain structure in alcoholism, the metabolites of dopamine (homovanillic acid, HVA), norepinephrenine (3-methoxy-4-hydroxyphenylethyleneglycol, MHPG) and serotonin (5-hydroxyindoleacetic acid, 5-HIAA) were measured in lumbar CSF in 54 alcohol-dependent patients and 20 healthy subjects. The volumes of the cerebrum, total grey and white matter, total and ventricular CSF, left and right hippocampus, and corpus callosum area were measured with MRI. MHPG and age were positively correlated in alcoholic women. The MAM concentrations were not significantly correlated with the MRI volumes in the subject categories. There were no differences in MAM across subjects defined by diagnosis and gender, age of onset of alcoholism or comorbidity of psychiatric disorders. Total CSF, cerebrum, and white and grey matter tissue volumes differed between patients and healthy subjects. The greatest difference was the white matter reduction in alcoholic women. In alcoholic women and men, monoaminergic neurotransmission measured by the CSF MAM HVA, MHPG, and 5-HIAA is not significantly correlated with the size of different brain structures.

Adult↗
PubMed2003

Cross-sectional volumetric analysis of brain atrophy in alcohol dependence: effects of drinking history and comorbid substance use disorder.

OBJECTIVE: The authors assessed whether individual differences in drinking history as well as lifetime incidence of comorbid cocaine or marijuana use disorder underlie differential patterns of brain atrophy in subjects with alcohol dependence. METHOD: Segmented magnetic resonance images were used to compare whole brain cerebral gray matter and white matter in 134 male subjects age 30-50 with alcohol dependence, either alone or with comorbid cocaine or marijuana use disorder. RESULTS: Across all subjects, drinking history variables correlated negatively with both gray matter and white matter after age was controlled. Alcohol-dependent subjects with no comorbid substance use disorder (N=51) showed a steeper negative correlation between age and the gray matter/white matter ratio than did alcohol-dependent subjects with a comorbid lifetime cocaine use disorder diagnosis (N=50). Alcohol-dependent subjects with comorbid cocaine use disorder tended to have a steeper negative correlation between age and white matter (adjusted for intracranial volume) than did alcohol-dependent subjects with no comorbid substance use disorder. After age and the greater estimated cumulative alcohol consumption of alcohol-dependent subjects with comorbid cocaine use disorder were controlled in a multiple regression analysis, however, comorbid cocaine use disorder did not account for any independent variance in any volumetric measure. CONCLUSIONS: Brain atrophy among subjects with alcohol dependence reflects individual differences in exposure to alcohol, and the data provide mixed evidence that comorbid cocaine use disorder may exacerbate white matter atrophy in alcoholism.

Adult↗
PubMed2003

Male and female sensitivity to alcohol-induced brain damage.

Women are more vulnerable than men to many of the medical consequences of alcohol use. Although research has shown that male alcoholics generally have smaller brain volumes than nonalcoholic males, the few studies that have compared brain structure in alcoholic men and women have had mixed results. To adequately compare brain damage between alcoholic women and men, it is necessary to control for age and to have separate control groups of nonalcoholic men and women. Although the majority of studies suggest that women are more vulnerable to alcohol-induced brain damage than men, the evidence remains inconclusive.

Age Factors↗
PubMedDate not supplied

Impulsivity in abstinent alcohol-dependent patients: relation to control subjects and type 1-/type 2-like traits.

Extensive literature has linked behavior control problems in childhood to risk for alcoholism, but impulsivity in alcohol-dependent adults has not been well characterized. Using a variety of laboratory measures of impulsivity, we assessed whether detoxified alcohol-dependent patients [(ADP); n = 130] were more impulsive than control subjects [(CS); n = 41]. In comparison with CS, ADP demonstrated (1) increased rates of commission errors, but not omission errors, in a continuous performance test, (2) a more severe devaluation of delayed reward, (3) increased rates of risky responses in a new risk-taking paradigm, and (4) higher psychometric scores of impulsivity and aggression. Across all subjects, aggressiveness correlated significantly with severity of delay discounting. A post hoc analysis of data obtained for male ADP indicated that, in comparison with patients with late onset of problem drinking and no problem-drinking parent, those ADP with earlier age of problem drinking and who reported a problem-drinking father (type 2-like alcohol dependence) demonstrated faster response latencies and more responses to non-target stimuli (commission errors) in the continuous performance test, as well as higher psychometric aggression. In contrast, these subtypes of male ADP did not differ in delay discounting and risk taking. These findings collectively indicate that, in comparison with CS, ADP are more impulsive in several dimensions, with elevated impulsivity in a working memory task as well as aggressivity characteristic of alcohol-dependent men with type 2-like features.

Adolescent↗