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R J Davidson

Publications and source records attributed to R J Davidson.

At least 55 records · Page 3Linked to original sources
PubMed1998

Reproducibility of fMRI results across four institutions using a spatial working memory task.

Four U.S. sites formed a consortium to conduct a multisite study of fMRI methods. The primary purpose of this consortium was to examine the reliability and reproducibility of fMRI results. FMRI data were collected on healthy adults during performance of a spatial working memory task at four different institutions. Two sets of data from each institution were made available. First, data from two subjects were made available from each site and were processed and analyzed as a pooled data set. Second, statistical maps from five to eight subjects per site were made available. These images were aligned in stereotactic space and common regions of activation were examined to address the reproducibility of fMRI results when both image acquisition and analysis vary as a function of site. Our grouped and individual data analyses showed reliable patterns of activation in dorsolateral prefrontal cortex and posterior parietal cortex during performance of the working memory task across all four sites. This multisite study, the first of its kind using fMRI data, demonstrates highly consistent findings across sites.

Adult↗
PubMed1998

Baseline EEG asymmetries and performance on neuropsychological tasks.

Thirty-two participants were tested for both resting electroencephalography (EEG) and neuropsychological function. Eight one-minute trials of resting EEG were recorded from 14 channels referenced to linked ears, which was rederived to an average reference. Neuropsychological tasks included Verbal Fluency, the Tower of London, and Corsi's Recurring Blocks. Asymmetries in EEG alpha activity were correlated with performance on these tasks. Similar patterns were obtained for delta and theta bands. Factor analyses of resting EEG asymmetries over particular regions suggested that asymmetries over anterior scalp regions may be partly independent from those over posterior scalp regions. These results support the notions that resting EEG asymmetries are specified by multiple mechanisms along the rostral/caudal plane, and that these asymmetries predict task performance in a manner consistent with lesion and neuroimaging studies.

Adult↗
PubMed1998

Anterior electrophysiological asymmetries, emotion, and depression: conceptual and methodological conundrums.

Two reports in the last issue of this journal attempted to replicate aspects of our previous studies on anterior electroencephalogram (EEG) asymmetry, affective style, and depression. In this commentary, an overview is provided of our model of anterior asymmetries, affective style, and psychopathology. Emphasis is placed on conceptualizing the prefrontal and anterior temporal activation patterns within a circuit that includes cortical and subcortical structures. The causal status of individual differences in asymmetric activation in the production of affective style and psychopathology is considered. Major emphasis is placed on EEG methods, particularly the need for multiple assessments to obtain estimates of asymmetric activation that better reflect an individual's true score. Issues specific to each of the two articles are also considered. Each of the articles has more consistency with our previously published data than the authors themselves suggest. Recommendations are made for future research to resolve some of the outstanding issues.

Depression↗
PubMed1998

Individual differences in freezing and cortisol in infant and mother rhesus monkeys.

Freezing is an adaptive defensive behavior that is expressed in response to an imminent threat. In prior studies with rhesus monkeys, stable individual differences in animals' propensities to freeze have been demonstrated. To understand the factors associated with these individual differences, freezing behavior was examined in infant rhesus monkeys and their mothers, in conjunction with levels of the stress-related hormone cortisol. In both mothers and infants, basal cortisol levels were positively correlated with freezing duration. Additionally, the number of offspring a mother had was negatively correlated with her infant's cortisol level. These findings suggest a link between basal cortisol levels and an animal's propensity to freeze, as well as a mechanism by which maternal experience may affect infants' cortisol levels.

Animals↗
PubMed1998

Asymmetric frontal brain activity, cortisol, and behavior associated with fearful temperament in rhesus monkeys.

The authors examined the hypothesis that rhesus monkeys with extreme right frontal electroencephalographic activity would have higher cortisol levels and would be more fearful compared with monkeys with extreme left frontal activity. The authors first showed that individual differences in asymmetric frontal electrical activity are a stable characteristic. Next, the authors demonstrated that relative right asymmetric frontal activity and cortisol levels are correlated in animals 1 year of age. Additionally, extreme right frontal animals had elevated cortisol concentrations and more intense defensive responses. At 3 years of age, extreme right frontal animals continued to have elevated cortisol concentrations. These findings demonstrate important relations among extreme asymmetric frontal electrical activity, cortisol levels, and trait-like fear-related behaviors in young rhesus monkeys.

Agonistic Behavior↗
PubMed1998

Relations between PET-derived measures of thalamic glucose metabolism and EEG alpha power.

Electroencephalogram (EEG) alpha power has been demonstrated to be inversely related to mental activity and has subsequently been used as an indirect measure of brain activation. The thalamus has been proposed as an important site for modulation of rhythmic alpha activity. Studies in animals have suggested that cortical alpha rhythms are correlated with alpha rhythms in the thalamus. However, little empirical evidence exists for this relation in humans. In the current study, resting EEG and a fluorodeoxyglucose positron emission tomography scan were measured during the same experimental session. Over a 30-min period, average EEG alpha power across 28 electrodes from 27 participants was robustly inversely correlated with glucose metabolic activity in the thalamus. These data provide the first evidence for a relation between alpha EEG power and thalamic activity in humans.

Adult↗
PubMed1998

A two-color BCR-ABL probe that greatly reduces the false positive and false negative rates for fluorescence in situ hybridization in chronic myeloid leukemia.

The t(9;22) translocation resulting in the fusion of BCR and ABL genes is pathognomonic in chronic myeloid leukemia (CML) and may be investigated at the molecular level using fluorescence in situ hybridization (FISH). Two-color BCR-ABL probes visualizing one fusion signal (1F FISH) have high false positive rates (FPR) and false negative rates (FNR). The FPR is a result of the random spatial association of probe signals within normal interphase cells so that some cells appear to contain the BCR-ABL fusion gene. The FNR of 1F FISH probes depends on the distance between the BCR and ABL probes hybridized to the BCR-ABL fusion gene (< or =368 kb); the "gap" between the signals causing the cell to be interpreted as normal. To overcome these difficulties, a two-color probe was used, employing four yeast artificial chromosome (YAC) sequences that span the breakpoint regions of the BCR and ABL genes and that visualize the two fusion signals BCR-ABL and ABL-BCR in CML cells (2F FISH). The FNR for the 2F FISH probes was assessed on clonal Ph+ granulocyte-macrophage-colony-forming cell (CFU-GM) derived colonies and was reduced to 0.4% (2/450), compared with an FNR of 13.5% (111/823) with 1F FISH. The FPR in normal mononuclear cells for the 2F FISH was 0. 19 +/- 0.12% (3/1,700), whereas the FPR using 1F FISH was 4.5 +/- 2.3% (63/1,294). The 2F FISH can thus be used to evaluate very small frequencies of BCR-ABL-positive and -negative interphase cells and may be of use in the clinical monitoring of CML.

Adult↗
PubMed1997

Brain electrical asymmetries during cognitive task performance in depressed and nondepressed subjects.

BACKGROUND: Studies using electroencephalogram (EEG) measures of activation asymmetry have reported differences in anterior asymmetry between depressed and nondepressed subjects. Several studies have suggested reciprocal relations between measures of anterior and posterior activation asymmetries. We hypothesized that depressed subjects would fail to show the normal activation of posterior right hemisphere regions in response to an appropriate cognitive challenge. METHODS: EEG activity was recorded from 11 depressed and 19 nondepressed subjects during the performance of psychometrically matched verbal (word finding) and spatial (dot localization) tasks. Band power was extracted from all epochs of artifact-free data and averaged within each condition. Task performance was also assessed. RESULTS: Depressed subjects showed a specific deficit in the performance of the spatial task, whereas no group differences were evident on verbal performance. In posterior scalp regions, nondepressed controls had a pattern of relative left-sided activation during the verbal task and relative right-sided activation during the spatial task. In contrast, depressed subjects failed to show activation in posterior right hemisphere regions during spatial task performance. CONCLUSIONS: These findings suggest that deficits in right posterior functioning underlie the observed impairments in spatial functioning among depressed subjects.

Adult↗
PubMed1997

A practical guide for the diagnosis and treatment of acute sinusitis.

OBJECTIVE: To develop guidelines for the diagnosis and management of acute sinusitis. OPTIONS: Diagnostic clinical criteria and imaging techniques, the role of antimicrobial therapy and duration of treatment, and the role of adjunct therapy, including decongestants, glucocorticosteroids and nasal irrigation. OUTCOMES: Improved accuracy of clinical diagnosis, better utilization of imaging techniques and rational use of antimicrobial therapy. EVIDENCE: A MEDLINE search for relevant articles published from 1980 to 1996 using the MeSH terms "sinusitis," "acute sinusitis," "respiratory infections," "upper respiratory infections," "sinusitis" and "diagnosis," "sinusitis" and "therapy," "sinusitis" and "etiology," and "antimicrobial resistance" and search for additional articles from the reference lists of retrieved articles. Papers referring to chronic sinusitis, sinusitis in compromised patients and documented nonbacterial sinusitis were excluded. The evidence was evaluated by participants at the Canadian Sinusitis Symposium, field in Toronto on April 26-27, 1996. VALUES: A hierarchical evaluation of the strength of evidence modified from the methods of the Canadian Task Force on the Periodic Health Examination was used. Strategies were identified to deal with problems for which no adequate clinical data were available. Recommendations arrived at by consensus of the symposium participants were included. BENEFITS, HARMS AND COSTS: Increased awareness of acute sinusitis, accurate diagnosis and prompt treatment should reduce costs related to unnecessary investigations, time lost from work and complications due to inappropriate treatment. As well, physicians will be better able to decide which patients will not require antimicrobial therapy, thus saving the patient the cost and potential side effects of treatment. RECOMMENDATIONS: Clinical diagnosis can usually be made from the patient's history and findings on physical examination only. Five clinical findings comprising 3 symptoms (maxillary toothache, poor response to decongestants and a history of coloured nasal discharge) and 2 signs (purulent nasal secretion and abnormal transillumination result) are the best predictors of acute bacterial sinusitis (level I evidence). Transillumination is a useful technique in the hands of experienced personnel, but only negative findings are useful (level III evidence). Radiography is not warranted when the likelihood of acute sinusitis is high or low but is useful when the diagnosis is in doubt (level III evidence). First-line therapy should be a 10-day course of amoxicillin (trimethoprim-sulfamethoxazole should be given to patients allergic to penicillin) (level I evidence) and a decongestant (level III evidence). Patients allergic to amoxicillin and those not responding to first-line therapy should be switched to a second-line agent. As well, patients with recurrent episodes of acute sinusitis who have been assessed and found not to have anatomic anomalies may also benefit from second-line therapy (level III evidence). VALIDATION: The recommendations are based on consensus of Canadian and American experts in infectious diseases, microbiology, otolaryngology and family medicine. The guidelines were reviewed independently for the advisory committee by 2 external experts. Previous guidelines did not exist in Canada.

Acute Disease↗
PubMed1997

Neuroanatomical correlates of pleasant and unpleasant emotion.

Substantial evidence suggests that a key distinction in the classification of human emotion is that between an appetitive motivational system association with positive or pleasant emotion and an aversive motivational system associated with negative or unpleasant emotion. To explore the neural substrates of these two systems, 12 healthy women viewed sets of pictures previously demonstrated to elicit pleasant, unpleasant and neutral emotion, while positron emission tomographic (PET) measurements of regional cerebral blood flow were obtained. Pleasant and unpleasant emotions were each distinguished from neutral emotion conditions by significantly increased cerebral blood flow in the vicinity of the medial prefrontal cortex (Brodmann's area 9), thalamus, hypothalamus and midbrain (P < 0.005). Unpleasant was distinguished from neutral or pleasant emotion by activation of the bilateral occipito-temporal cortex and cerebellum, and left parahippocampal gyrus, hippocampus and amygdala (P < 0.005). Pleasant was also distinguished from neutral but not unpleasant emotion by activation of the head of the left caudate nucleus (P < 0.005). These findings are consistent with those from other recent PET studies of human emotion and demonstrate that there are both common and unique components of the neural networks mediating pleasant and unpleasant emotion in healthy women.

Adolescent↗
PubMed1997

Manipulating affective state using extended picture presentations.

Separate, extended series of positive, negative, and neutral pictures were presented to 24 (12 men, 12 women) undergraduates. Each series was presented on a different day, with full counterbalancing of presentation orders. Affective state was measured using (a) orbicularis oculi activity in response to acoustic startle probes during picture presentation, (b) corrugator supercilii activity between and during picture presentation, and (c) changes in self-reports of positive and negative affect. Participants exhibited larger eyeblink reflex magnitudes when viewing negative than when viewing positive pictures. Corrugator activity was also greater during the negative than during the positive picture set, during both picture presentation and the period between pictures. Self-reports of negative affect increased in response to the negative picture set, and self-reports of positive affect were greatest following the positive picture set. These findings suggest that extended picture presentation is an effective method of manipulating affective state and further highlight the utility of startle probe and facial electromyographic measures in providing on-line readouts of affective state.

Adult↗
PubMed1997

The concurrent recording of electroencephalography and impedance cardiography: effects on EEG.

Three experiments were performed testing the effects of a variety of impedance cardiograph electrode types and recording arrangements on recorded electroencephalography (EEG) using either a monopolar single-ear reference or a physically linked ears reference. EEG was recorded either alone or concurrently with an impedance cardiograph. When the cardiograph was recorded using a spot electrode for the top current-inducing electrode, there was an overall decrease in power density of the EEG, and this effect was dependent on the location of the recording electrode. This effect was diminished when the top cardiograph spot electrode was replaced by a mylar-coated neck band electrode and EEG was recorded using a monopolar, single-ear reference. However, there tended to be an overall increase in log power density of the EEG in each frequency band below 60 Hz when less technologically advanced EEG amplifiers were used. This effect was diminished if the EEG was recorded using a physically linked ears reference. Recommendations for the concurrent recording of EEG and impedance cardiography are discussed.

Adolescent↗
PubMed1997

Emotional activation of limbic circuitry in elderly normal subjects in a PET study.

OBJECTIVE: This study was undertaken to identify brain structures associated with emotion in normal elderly subjects. METHOD: Eight normal subjects aged 55-78 years were shown film clips intended to provoke the emotions of happiness, fear, or disgust as well as a neutral state. During emotional activation, regional cerebral blood flow was measured with the use of [15O]H2O positron emission tomography imaging, and subjective emotional responses were recorded. Data were analyzed by subtracting the values during the neutral condition from the values in the various emotional activations. RESULTS: The stimuli produced a general activation in visual pathways that included the primary and secondary visual cortex, involving regions associated with object and spatial recognition. In addition, the specific emotions produced different regional limbic activations, which suggests that different pathways may be used for different types of emotional stimuli. CONCLUSIONS: Emotional activation in normal elderly subjects was associated with increases in blood flow in limbic and paralimbic brain structures. Brain activation may be specific to the emotion being elicited but probably involves complex sensory, association, and memory circuitry. Further studies are needed to identify activations that are specific for emotion.

Aged↗
PubMed1997

Neuroanatomical correlates of externally and internally generated human emotion.

OBJECTIVE: Positron emission tomography was used to investigate the neural substrates of normal human emotional and their dependence on the types of emotional stimulus. METHOD: Twelve healthy female subjects underwent 12 measurements of regional brain activity following the intravenous bolus administration of [15O]H2O as they alternated between emotion-generating and control film and recall tasks. Automated image analysis techniques were used to characterize and compare the increases in regional brain activity associated with the emotional response to complex visual (film) and cognitive (recall) stimuli. RESULTS: Film- and recall-generated emotion were each associated with significantly increased activity in the vicinity of the medial prefrontal cortex and thalamus, suggesting that these regions participate in aspects of emotion that do not depend on the nature of the emotional stimulus. Film-generated emotion was associated with significantly greater increases in activity bilaterally in the occipitotemporparietal cortex, lateral cerebellum, hypothalamus, and a region that includes the anterior temporal cortex, amygdala, and hippocampal formation, suggesting that these regions participate in the emotional response to certain exteroceptive sensory stimuli. Recall-generated sadness was associated with significantly greater increases in activity in the vicinity of the anterior insular cortex, suggesting that this region participates in the emotional response to potentially distressing cognitive or interoceptive sensory stimuli. CONCLUSIONS: While this study should be considered preliminary, it identified brain regions that participate in externally and internally generated human emotion.

Adult↗
PubMed1997

Neuroanatomical correlates of happiness, sadness, and disgust.

OBJECTIVE: Happiness, sadness, and disgust are three emotions that differ in their valence (positive or negative) and associated action tendencies (approach or withdrawal). This study was designed to investigate the neuroanatomical correlates of these discrete emotions. METHOD: Twelve healthy female subjects were studied. Positron emission tomography and [15O]H2O were used to measure regional brain activity. There were 12 conditions per subject: happiness, sadness, and disgust and three control conditions, each induced by film and recall. Emotion and control tasks were alternated throughout. Condition order was pseudo-randomized and counterbalanced across subjects. Analyses focused on brain activity patterns for each emotion when combining film and recall data. RESULTS: Happiness, sadness, and disgust were each associated with increases in activity in the thalamus and medial prefrontal cortex (Brodmann's area 9). These three emotions were also associated with activation of anterior and posterior temporal structures, primarily when induced by film. Recalled sadness was associated with increased activation in the anterior insula. Happiness was distinguished from sadness by greater activity in the vicinity of ventral mesial frontal cortex. CONCLUSIONS: While this study should be considered preliminary, it identifies regions of the brain that participate in happiness, sadness, and disgust, regions that distinguish between positive and negative emotions, and regions that depend on both the elicitor and valence of emotion or their interaction.

Adult↗
PubMed1997

Functional magnetic resonance imaging studies of emotional processing in normal and depressed patients: effects of venlafaxine.

BACKGROUND: Functional magnetic resonance imaging (fMRI) techniques were used to identify the neural circuitry underlying emotional processing in control and depressed subjects. Depressed subjects were studied before and after treatment with venlafaxine. This new technique provides a method to noninvasively image regional brain function with unprecedented spatial and temporal resolution. METHOD: Echo-planar imaging was used to acquire whole brain images while subjects viewed positively and negatively valenced visual stimuli. Two control subjects and two depressed subjects who met DSM-IV criteria for major depression were scanned at baseline and 2 weeks later. Depressed subjects were treated with venlafaxine after the baseline scan. RESULTS: Preliminary results from this ongoing study revealed three interesting trends in the data. Both depressed patients demonstrated considerable symptomatic improvement at the time of the second scan. Across control and depressed subjects, the negative compared with the positive pictures elicited greater global activation. In both groups, activation induced by the negative pictures decreased from the baseline scan to the 2-week scan. This decrease in activation was also present in the control subjects when they were exposed to the positive pictures. In contrast, when the depressed subjects were presented with the positive pictures they showed no activation at baseline, whereas after 2 weeks of treatment an area of activation emerged in right secondary visual cortex. CONCLUSION: While preliminary, these results demonstrate the power of using fMRI to study emotional processes in normal and depressed subjects and to examine mechanisms of action of antidepressant drugs.

Adolescent↗
PubMed1996

Human amygdala activation detected with echo-planar functional magnetic resonance imaging.

Echo-Planar functional magnetic resonance imaging (EP-fMRI) was used to study the activity of the amygdala while three normal female subjects viewed alternating blocks of affectively neutral and affectively negative still pictures. Bilateral activation in the amygdala that was significantly correlated with the changing valence of the visual stimuli was found in all three subjects. These findings are consistent with the large corpus of data from non-human studies suggesting that the amygdala is a key structure for extracting the affective significance from external stimuli. This is the first known report of phasic amygdala activation detected with EP-fMRI in normal human subjects responding to affective stimuli.

Adult↗