Biomedical subjects

George Bush

Publications and source records attributed to George Bush.

9 recordsLinked to original sources

PubMed2006

Cortical thinning of the attention and executive function networks in adults with attention-deficit/hyperactivity disorder.

Attention-deficit/hyperactivity disorder (ADHD) has been associated with structural alterations in brain networks influencing cognitive and motor behaviors. Volumetric studies in children identify abnormalities in cortical, striatal, callosal, and cerebellar regions. In a prior volumetric study, we found that ADHD adults had significantly smaller overall cortical gray matter, prefrontal, and anterior cingulate volumes than matched controls. Thickness and surface area are additional indicators of integrity of cytoarchitecture in the cortex. To expand upon our earlier results and further refine the regions of structural abnormality, we carried out a structural magnetic resonance imaging study of cortical thickness in the same sample of adults with ADHD (n = 24) and controls (n = 18), hypothesizing that the cortical networks underlying attention and executive function (EF) would be most affected. Compared with healthy adults, adults with ADHD showed selective thinning of cerebral cortex in the networks that subserve attention and EF. In the present study, we found significant cortical thinning in ADHD in a distinct cortical network supporting attention especially in the right hemisphere involving the inferior parietal lobule, the dorsolateral prefrontal, and the anterior cingulate cortices. This is the first documentation that ADHD in adults is associated with thinner cortex in the cortical networks that modulate attention and EF.

Adolescent↗

PubMed2006

Dorsolateral prefrontal and anterior cingulate cortex volumetric abnormalities in adults with attention-deficit/hyperactivity disorder identified by magnetic resonance imaging.

OBJECTIVES: Gray and white matter volume deficits have been reported in a number of studies of children with attention-deficit/hyperactivity disorder (ADHD); however, there is a paucity of structural magnetic resonance imaging (MRI) studies of adults with ADHD. This structural MRI study used an a priori region of interest approach. METHODS: Twenty-four adults with DSM-IV ADHD and 18 healthy controls comparable on age, socioeconomic status, sex, handedness, education, IQ, and achievement test performance had an MRI on a 1.5T Siemens scanner. Cortical and sub-cortical gray and white matter were segmented. Image parcellation divided the neocortex into 48 gyral-based units per hemisphere. Based on a priori hypotheses we focused on prefrontal, anterior cingulate cortex (ACC) and overall gray matter volumes. General linear analyses of the volumes of brain regions, adjusting for age, sex, and total cerebral volumes, were used to compare groups. RESULTS: Relative to controls, ADHD adults had significantly smaller overall cortical gray matter, prefrontal and ACC volumes. CONCLUSIONS: Adults with ADHD have volume differences in brain regions in areas involved in attention and executive control. These data, largely consistent with studies of children, support the idea that adults with ADHD have a valid disorder with persistent biological features.

Adult↗

PubMed2005

Functional neuroimaging of attention-deficit/hyperactivity disorder: a review and suggested future directions.

Over the past few decades, functional neuroimaging techniques have begun to provide unprecedented windows on the neurobiology of attention-deficit/hyperactivity disorder (ADHD) and the neural effects of medications used to treat the disorder. Convergent data from neuroimaging, neuropsychological, genetics, and neurochemical studies have implicated dysfunction of fronto-striatal structures (lateral prefrontal cortex, dorsal anterior cingulate cortex, caudate, and putamen) as likely contributing to the pathophysiology of ADHD. This review 1) provides an overview of the main imaging techniques being used to study ADHD; 2) discusses their relative strengths and weaknesses, highlighting how they can complement one another; 3) shows how the functional imaging literature, which has built on the structural imaging data, is now being used to test focused hypotheses regarding the neurobiological substrate of ADHD; and 4) suggests guidelines for improving future functional imaging studies. Although at present there are no accepted uses for functional imaging in diagnosing ADHD, this article mentions possible future clinical uses of imaging in ADHD.

Attention Deficit Disorder with Hyperactivity↗

PubMed2005

Architecture and neurocytology of monkey cingulate gyrus.

Human functional imaging and neurocytology have produced important revisions to the organization of the cingulate gyrus and demonstrate four structure/function regions: anterior, midcingulate (MCC), posterior (PCC), and retrosplenial. This study evaluates the brain of a rhesus and 11 cynomolgus monkeys with Nissl staining and immunohistochemistry for neuron-specific nuclear binding protein, intermediate neurofilament proteins, and parvalbumin. The MCC region was identified along with its two subdivisions (a24' and p24'). The transition between areas 24 and 23 does not involve a simple increase in the number of neurons in layer IV but includes an increase in neuron density in layer Va of p24', a dysgranular layer IV in area 23d, granular area 23, with a neuron-dense layer Va and area 31. Each area on the dorsal bank of the cingulate gyrus has an extension around the fundus of the cingulate sulcus (f 24c, f 24c', f 24d, f 23c), whereas most cortex on the dorsal bank is composed of frontal motor areas. The PCC is composed of a dysgranular area 23d, area 23c in the caudal cingulate sulcus, a dorsal cingulate gyral area 23a/b, and a ventral area 23a/b. Finally, a dysgranular transition zone includes both area 23d and retrosplenial area 30. The distribution of areas was plotted onto flat maps to show the extent of each and their relationships to the vertical plane at the anterior commissure, corpus callosum, and cingulate sulcus. This major revision of the architectural organization of monkey cingulate cortex provides a new context for connection studies and for devising models of neuron diseases.

Animals↗

PubMed2004

Human anterior cingulate neurons and the integration of monetary reward with motor responses.

The human dorsal anterior cingulate cortex (dACC) has been implicated in cognitive processes that have been proposed to play a role in integrating contextual information needed to select or modify appropriate motor responses. In humans, however, there has been little direct evidence tying the dACC to the integration of contextual information and behavioral response. We used single-neuron recordings from human subjects to evaluate the role of the dACC in reward-based decision making. Subjects undergoing planned surgical cingulotomy performed a task where they were instructed to make specific movements in response to changing monetary rewards. In many neurons, activity increased in response to a diminished reward, and was also predictive of the movement ultimately made. After dACC ablation, subjects made selectively more errors when they were required to change movement based on reward reduction. These findings suggest that the dACC in humans plays an important role in linking reward-related information with alternative actions.

Analysis of Variance↗

PubMed2004

Brain function and structure in adults with attention-deficit/hyperactivity disorder.

Cross-sectional data suggest that brain dysfunctions are a central component of attention-deficit/hyperactivity disorder (ADHD) in children, and a growing literature is suggesting the same for adults. This article reviews the current state of the literature pertaining to the structural and functional brain abnormalities that are found in adults with ADHD. Because the literature on ADHD in children is more extensive than that reported heretofore in ADHD in adults,the authors include brief summaries of the child literature to help inform that found in adults.

Adolescent↗

PubMed2004

Anterior cingulate cortex activation during cognitive interference in schizophrenia.

BACKGROUND: Previous studies have reported evidence of structural and functional abnormalities in the anterior cingulate cortex of patients with schizophrenia. METHOD: The authors studied 19 male patients with chronic schizophrenia and 15 healthy male comparison subjects with functional magnetic resonance imaging and the novel Multi-Source Interference Task, a task designed to elicit robust dorsal anterior cingulate cortex activation in individual subjects. Group averaged and individual (region-of-interest-based) brain activation patterns were compared during the performance of control and interference trials. RESULTS: Performance (reaction times and accuracy) did not differ between healthy subjects and patients with schizophrenia. Comparison of interference and neutral blocks revealed activation in the medial wall of the prefrontal cortex in 93% (N=14) of the healthy subjects and 84% (N=16) of the subjects with schizophrenia. Sixty-seven percent (N=10) of the healthy subjects but only 16% (N=3) of the subjects with schizophrenia displayed maximum medial wall activation within the dorsal anterior cingulate cortex. CONCLUSIONS: The Multi-Source Interference Task produced robust activation in the medial wall of the prefrontal cortex during cognitive interference. Analysis of individual activation patterns revealed medial wall abnormalities in schizophrenia patients.

Cognition Disorders↗

PubMed2002

Neural and behavioral substrates of mood and mood regulation.

A review of behavioral and neurobiological data on mood and mood regulation as they pertain to an understanding of mood disorders is presented. Four approaches are considered: 1) behavioral and cognitive; 2) neurobiological; 3) computational; and 4) developmental. Within each of these four sections, we summarize the current status of the field and present our vision for the future, including particular challenges and opportunities. We conclude with a series of specific recommendations for National Institute of Mental Health priorities. Recommendations are presented for the behavioral domain, the neural domain, the domain of behavioral-neural interaction, for training, and for dissemination. It is in the domain of behavioral-neural interaction, in particular, that new research is required that brings together traditions that have developed relatively independently. Training interdisciplinary clinical scientists who meaningfully draw upon both behavioral and neuroscientific literatures and methods is critically required for the realization of these goals.

Affect↗

PubMed2001

Dorsal anterior cingulate cortex: a role in reward-based decision making.

Dorsal anterior cingulate cortex (dACC) is a brain region that subserves cognition and motor control, but the mechanisms of these functions remain unknown. Human neuroimaging and monkey electrophysiology studies have provided valuable insights, but it has been difficult to link the two literatures. Based on monkey single-unit recordings, we hypothesized that human dACC is comprised of a mixture of functionally distinct cells that variously anticipate and detect targets, indicate novelty, influence motor responses, encode reward values, and signal errors. As an initial test of this conceptualization, the current event-related functional MRI study used a reward-based decision-making task to isolate responses from a subpopulation of dACC cells sensitive to reward reduction. As predicted, seven of eight subjects showed significant (P < 10(-4)) dACC activation when contrasting reduced reward (REDrew) trials to fixation (FIX). Confirmatory group analyses then corroborated the predicted ordinal relationships of functional MRI activation expected during each trial type (REDrew > SWITCH > CONrew > or = FIX). The data support a role for dACC in reward-based decision making, and by linking the human and monkey literatures, provide initial support for the existence of heterogeneity within dACC. These findings should be of interest to those studying reward, cognition, emotion, motivation, and motor control.

Adult↗