Biomedical subjects

Lawrence Frank

Publications and source records attributed to Lawrence Frank.

10 recordsLinked to original sources

PubMed2006

Improved anatomic delineation of the antidepressant response to partial sleep deprivation in medial frontal cortex using perfusion-weighted functional MRI.

This study used functional magnetic resonance imaging (fMRI) to clarify the sites of brain activity associated with the antidepressant effects of sleep deprivation (SD). We hypothesized: 1) depressed responders' baseline ventral anterior cingulate (AC) perfusion will be greater than that of nonresponders and controls; 2) following partial sleep deprivation (PSD), ventral AC perfusion will significantly decrease in responders only. Seventeen unmedicated outpatients with current major depression and eight controls received perfusion-weighted fMRI and structural MRI at baseline and following 1 night of late-night PSD. Talairach-transformed gray matter masks were merged with Talairach Daemon-based region of interest (ROI) templates. Baseline left ventral AC (LVAC) perfusion was greater in responders than nonresponders. There was no difference involving the medial frontal cortex. Responders' LVAC perfusion dropped from baseline to PSD scans compared with nonresponders and controls, as did perfusion in the right dorsal AC. In the patient group as a whole, decrease in LVAC perfusion from baseline to PSD scans correlated directly with the decrease in the modified 17-item Hamilton Depression Rating Scale (HDRS17) between baseline and PSD conditions. These data--the first using fMRI--show greater anatomic specificity than previous findings of SD and depression in linking decreased brain activity in this area with clinical improvement.

Adolescent↗

PubMed2006

Walkability of local communities: using geographic information systems to objectively assess relevant environmental attributes.

Geographic Information Systems (GIS) can be used to objectively measure features of the built environment that may influence adults' physical activity, which is an important determinant of chronic disease. We describe how a previously developed index of walkability was operationalised in an Australian context, using available spatial data. The index was used to generate a stratified sampling frame for the selection of households from 32 communities for the PLACE (Physical Activity in Localities and Community Environments) study. GIS data have the potential to be used to construct measures of environmental attributes and to develop indices of walkability for cities, regions or local communities.

Adult↗

PubMed2005

Residents' perceptions of walkability attributes in objectively different neighbourhoods: a pilot study.

Physical attributes of local environments may influence walking. We used a modified version of the Neighbourhood Environment Walkability Scale to compare residents' perceptions of the attributes of two neighbourhoods that differed on measures derived from Geographic Information System databases. Residents of the high-walkable neighbourhood rated relevant attributes of residential density, land-use mix (access and diversity) and street connectivity, consistently higher than did residents of the low-walkable neighbourhood. Traffic safety and safety from crime attributes did not differ. Perceived neighbourhood environment characteristics had moderate to high test-retest reliabilities. Neighbourhood environment attribute ratings may be used in population surveys and other studies.

Adult↗

PubMed2003

Error-rate-related caudate and parietal cortex activation during decision making.

The role of cortical and subcortical structures in processing success or failure in decision-making situations is unclear. Functional neuroimaging (fMRI) during a two-choice prediction task was used to investigate the relationship between error-rate-related behavioral changes during decision-making and activation patterns in the caudate and parietal cortex. Success-related activation was found in caudate and parietal cortex during a two-choice prediction task. At low error rates, participants utilized success-related behavioral strategies rate by decreasing switching responses and increasing response predictability, which were associated with activation changes in the caudate and parietal cortex. Therefore, less response switching and increased response predictability during decision making can be directly related to the degree of activation in the caudate and posterior parietal cortex.

Adult↗

PubMed2003

Decision making by methamphetamine-dependent subjects is associated with error-rate-independent decrease in prefrontal and parietal activation.

BACKGROUND: One important aspect in decision making is how success or failure influences the selection of a response. In a previous investigation, methamphetamine-dependent subjects (MD) selected win-stay/lose-shift consistent responses than normal comparison subjects (NC), which may imply that MD are more influenced by success. This study examined whether the degree of success and the degree of predictability differentially affected MD's decision making. METHODS: Using functional magnetic resonance imaging, 14 MD were compared with 14 NC while performing the two-choice prediction task at three success rates and the two-choice response task. RESULTS: The increase in win-stay/lose-shift consistent responses by MD relative to NC was independent of success rate. Irrespective of success, MD showed less task-related activation in orbitofrontal cortex (Brodmann's area [BA] 10), dorsolateral prefrontal cortex (BA 9), anterior cingulate (BA 32), and parietal cortex (BA 7). Whereas NC showed success-related patterns of neural activation in the orbitofrontal, dorsolateral prefrontal, and parietal cortex, MD showed activation that was highest when the outcome was most unpredictable. CONCLUSIONS: Our results are consistent with the hypothesis of a more rigid stimulus-response relationship during MD's decision making, which may be due to a shift from processing "success" toward processing the degree of stimulus "predictability."

Adult↗

PubMed2002

Schizophrenia subjects show intact success-related neural activation but impaired uncertainty processing during decision-making.

Decision-making is a complex process that is important for everyday life. This study examined the effect of the degree of success, and outcome uncertainty, on decision-making and associated neural substrate activation in schizophrenia subjects (SZS) and normal comparison subjects (NCS). A total of 15 subjects with a diagnosis of schizophrenia and 15 age- and education-matched NCS participated in this study. These subjects completed the two-choice prediction task during functional magnetic resonance imaging. Decision-making characteristics and activation of neural substrates were obtained at 20, 50, or 80% error rate. Success and uncertainty influenced the behavioral characteristics on the two-choice prediction task, and the task-related activation in SZS and NCS. Neither success nor uncertainty differentially affected the behavioral characteristics of SZS relative to NCS during the two-choice prediction task. Nonetheless, there was a significant interaction between group and error rate in bilateral parietal cortex. The activation in NCS was the highest when the outcome was most uncertain. In contrast, task-related activation in SZS was not modulated by the degree of uncertainty. Thus, SZS failed to utilize the parietal cortex to process decision-making situations with highly uncertain outcomes.

Adult↗

PubMed2002

Parietal dysfunction is associated with increased outcome-related decision-making in schizophrenia patients.

BACKGROUND: Decision-making is a complex process and depends on a network of fronto-parietal and cingulate areas. Decision-making dysfunctions in schizophrenia patients are characterized by an alternation between stereotypic and unpredictable responses. This study tested the hypothesis that schizophrenia patients show less decision-making-related activation in the prefrontal and parietal cortex. METHODS: Fifteen schizophrenia patients were matched with fifteen normal comparison subjects. During functional magnetic resonance imaging (fMRI) scanning, subjects were tested on the two-choice prediction task (predicting the location of a randomly presented stimulus) and the two-choice response task (responding according to the location of the stimulus). RESULTS: Schizophrenia patients relative to comparison subjects generated more outcome-dependent responses. Schizophrenia patients and normal comparison subjects showed decision-making-related activation in right prefrontal cortex, insula, anterior cingulate, and bilateral precuneus. Schizophrenia patients showed less activation in inferior, medial prefrontal, and right superior temporal cortex and more activation in the postcentral and inferior parietal cortex. Decision-making-related activation in both right prefrontal and bilateral parietal cortex was higher in medicated compared to unmedicated schizophrenia patients. CONCLUSIONS: These results support the hypothesis that the interaction between prefrontal and parietal cortex during decision-making by schizophrenia patients is dysregulated, which results in an increased outcome-dependent response selection.

Adult↗

PubMed2002

Error rate and outcome predictability affect neural activation in prefrontal cortex and anterior cingulate during decision-making.

Decision-making in the presence of uncertainty is a complex process that involves both affective and cognitive factors. Both error rate and predictability have been implicated in the process of response selection during decision-making. This study examined the hypothesis that the rate of errors during decision-making differentially affects the activation in prefrontal and cingulate cortex. BOLD echo-planar signal intensity was obtained during a two-choice prediction task across 90-s blocks with 20, 50, or 80% error rates. This study yielded three main findings. First, at chance level error rates, activation of the right dorsolateral (BA 9, 46), inferior prefrontal (BA 44), and precuneus (BA 7) during the two-choice prediction task replicated the finding previously reported. Second, premotor (BA 6) and parahippocampal (BA 36) areas were relatively more active at high error rates, and dorsolateral (BA 9, 46) and inferior prefrontal cortex (BA 44) as well as parietal (BA 40) and cingulate cortex (BA 25, 32) were more active during low error rates. Third, the relationship between the frequency of the dominant strategy underlying decision-making (win-stay/lose-shift) and the activation in the dorsolateral prefrontal cortex and the anterior cingulate was dependent on error rate or outcome predictability. These results support the hypothesis that error rates and predictability affect the activation patterns in the neural systems underlying decision-making because these structures maintain a representation of the reinforcement history for the available response alternatives to select an "optimal strategy."

Adult↗

PubMed2002

Behavioral and functional neuroimaging evidence for prefrontal dysfunction in methamphetamine-dependent subjects.

Stimulant-dependent subjects show dysfunctions in decision-making similar to those seen in subjects with ventromedial prefrontal cortex lesions. Studies of drug craving, reward association, and decision-making have implicated dysfunctions of the dorsolateral and orbitofrontal cortex as a key neural substrate in subjects with stimulant dependence. Here, a functional magnetic resonance imaging (fMRI) study was carried out to determine the relationship between decision-making dysfunction and neural activation in different prefrontal areas. This investigation tested the behavioral hypothesis that methamphetamine-dependent subjects in early sustained remission show decision-making dysfunctions that are consistent with an increased reliance on stimulus-contingent response selection. It was hypothesized that these decision-making dysfunctions are due to differences in task-related activation in the dorsolateral and ventromedial prefrontal cortex. Ten methamphetamine-dependent subjects were compared with ten age- and education-matched controls performing a two-choice prediction task and a two-choice response task during a fMRI session. Response bias, latency, and mutual information measures assessing the underlying strategies of the decision-making sequences were obtained. First, methamphetamine-dependent subjects were more influenced by the immediately preceding outcome during the two-choice prediction task relative to normal comparison subjects. Second, methamphetamine-dependent subjects activated less dorsolateral prefrontal cortex (BA 9) and failed to activate ventromedial cortex (BA 10,11) during the two-choice prediction task compared with the two-choice response task. These results support the basic hypothesis that stimulant-dependent subjects exhibit fundamental cognitive deficits during decision-making that are consistent with both orbitofrontal and dorsolateral prefrontal dysfunction.

Adult↗

PubMedDate not supplied

Rheumatoid arthritis of the cervical spine.

BACKGROUND CONTEXT: Rheumatoid arthritis affects over 2 million patients in the United States. It is the most common inflammatory disorder of the cervical spine. The natural history is variable. Women tend to be more commonly involved than men. Atlantoaxial instability is the most common form of cervical involvement and may occur either independently or concomitantly with cranial settling and subaxial instability. Cervical spine involvement can be seen in up to 86% of patients and neurologic involvement in up to 58%. Myelopathy is rare but when present portends a poor prognosis. What is frustrating for clinicians treating these patients is that pain cannot be equated with instability or instability with neurologic symptoms. The goal is to identify patients at risk before the development of neurologic symptoms. Both radiographic and nonradiographic risk factors play an important role in the surgical decision-making process. PURPOSE: We will describe the current concepts in rheumatoid arthritis of the cervical spine. Emphasis is placed on the natural history, anatomy, pathophysiology and decision-making process. STUDY DESIGN: A review of the current concepts of rheumatoid arthritis of the cervical spine. METHODS: MEDLINE search of all English literature published on rheumatoid arthritis of the cervical spine. RESULTS: Rheumatoid arthritis of the cervical spine was first described by Garrod in 1890. The prevalence has been estimated to be 1% to 2% of the world's adult population. Despite its prevalence, the etiology of rheumatoid arthritis remains unknown. Because of its potentially debilitating and life-threatening sequelae in advanced disease, rheumatoid arthritis in the cervical spine today remains a high priority to diagnose and treat. CONCLUSIONS: Many aspects of the natural history and pathophysiology of the rheumatoid spine remain unclear. The timing of operative intervention in patients with radiographic instability and no evidence of neurologic deficit is an area of considerable controversy. Continued surveillance into the natural history of the rheumatoid spine is required.

Arthritis, Rheumatoid↗