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Performance Accuracy (performance + accuracy)
Selected AbstractsFunctional Magnetic Resonance Imaging of Working Memory among Multiple Sclerosis PatientsJOURNAL OF NEUROIMAGING, Issue 2 2004Lawrence H. Sweet PhD ABSTRACT Background and Purpose. Verbal working memory (VWM) deficits have been a well-replicated finding among patients with multiple sclerosis (MS). Functional magnetic resonance imaging (FMRI) studies have described a VWM system in healthy samples; however, functional neuroimaging of this system among MS patients is just beginning to appear. Methods. Fifteen MS patients and 15 sex-, age-, education-, and IQ-matched healthy control (HC) participants completed a 2-Back VWM task as whole-brain FMRI was conducted. Results. Each group exhibited increased brain activity compared to the 0-Back control task in regions associated with the 2-Back in previous neuroimaging studies. These included Broca's area, supplementary motor area (SMA), premotor cortices (PMC), and dorsolateral prefrontal cortices (DLPFC). MS patients exhibited greater cortical activity than did HC participants in left primary motor and somatosensory cortices, PMC, DLPFC, anterior cingulate, and bilateral SMA. MS patients exhibited relatively less activation in Broca's area, bilateral cerebellum, and other regions not typically associated with the 2-Back (eg, right fusiform gyrus, left lingual gyrus, right hippocampus). Performance accuracy and reaction time did not differ between groups. Conclusions. Normal performance of a challenging VWM task among high-functioning MS patients is associated with a shift toward greater activity in regions related to sensorimotor functions and anterior attentional/executive components of the VWM system. Posterior memory storage systems appeared unaffected, while portions of the visual processing and subvocal rehearsal systems were less active. Although a shift in neural activity was noted relative toHC participants, deviation from regions normally involved in VWM function was not observed in this patient sample. [source] Behavioral response to methylphenidate challenge: Influence of early life parental careDEVELOPMENTAL PSYCHOBIOLOGY, Issue 5 2009Veronika Engert Abstract Rat studies have shown that pups subjected to suboptimal rearing conditions exhibited permanently dysregulated dopamine activity and altered behavioral responses to dopamine stimulation. In humans, heightened stress-induced mesoaccumbens dopamine release in adults reporting low maternal care experience has been shown. We explored the relationship between quality of parental care and behavioral responsivity to reward and 20,mg of the dopamine agonist methylphenidate (MPH). Forty-three male university students accomplished a monetarily rewarded card-sorting task in a placebo controlled between-subjects study design. In participants scoring above the cut-off score for high parental care as assessed by the Parental Bonding Inventory, MPH decreased performance accuracy in the reward condition of the task. Contrarily, reward-induced performance accuracy of low care participants was enhanced with MPH. Activity measures in response to reward and MPH were uninfluenced by parental care. This is the first human study to reveal that the behavioral MPH response interacts with early life parental care experience. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 51: 408,416, 2009. [source] Dissociation between MEG alpha modulation and performance accuracy on visual working memory task in obsessive compulsive disorderHUMAN BRAIN MAPPING, Issue 12 2007Kristina T. Ciesielski Abstract Oscillatory brain activity in the alpha band (8,13 Hz) is modulated by cognitive events. Such modulation is reflected in a decrease of alpha (event-related desynchronization; ERD) with high cognitive load, or an increase (event-related synchronization) with low cognitive demand or with active inhibition of distractors. We used magnetoencephalography to investigate the pattern of prefrontal and parieto-occipital alpha modulation related to two variants of visual working memory task (delayed matching-to-sample) with and without a distractor. We tested nonmedicated, nondepressed patients suffering obsessive-compulsive disorder (OCD), and pair-matched healthy controls. The level of event-related alpha as a function of time was estimated using the temporal-spectral evolution technique. The results in OCD patients indicated: (1) a lower level of prestimulus (reference) alpha when compared to controls, (2) a task-phase specific reduction in event-related alpha ERD in particular for delayed matching-to-sample task with distractor, (3) no significant correlations between the pattern of modulation in prefrontal and parietal-occipital alpha oscillatory activity. Despite showing an abnormally low alpha modulation, the OCD patients' performance accuracy was normal. The results suggest a relationship of alpha oscillations and the underlying thalamocortical network to etiology of OCD and an involvement of a compensatory mechanism related to effortful inhibition of extrinsic and intrinsic interference. Hum Brain Mapp 2007. © 2007 Wiley-Liss, Inc. [source] Functional magnetic resonance imaging response to increased verbal working memory demands among patients with multiple sclerosisHUMAN BRAIN MAPPING, Issue 1 2006Lawrence H. Sweet Abstract Multiple sclerosis (MS) patients frequently experience impaired verbal working memory (VWM). Functional magnetic resonance imaging (fMRI) may help identify neural mechanisms underlying these deficits. Neuroimaging studies of healthy adults have characterized responses associated with increased VWM demands during the n-Back task, suggesting that this experimental paradigm could help identify neural correlates of VWM deficits among MS patients. Fifteen MS patients and 15 matched control participants completed the n-Back during whole-brain fMRI. Mean signal during adjacent 0-Back blocks was subtracted, on a voxel-wise basis, from mean signal observed during n-Back blocks. Resulting difference scores for 1-, 2-, and 3-Back were compared across groups and difficulty levels. Signal intensity was positively related to difficulty level in anterior regions, including premotor, supplementary motor, and dorsolateral prefrontal cortices. MS patients exhibited significantly greater intensity in these areas compared to controls during the 1-Back, while portions of the left superior frontal gyrus, cingulate, and parahippocampal gyri were relatively less intense at more difficult levels. MS group responses were slower during the 1-Back and tended to be slower during the 3-Back; however, accuracy did not differ at any level. Lesion load was positively related to only 1-Back activity and unrelated to any performance measure. Results suggest that compensatory activity occurs among MS patients matched on performance accuracy. Furthermore, compensatory activity occurs predominantly in regions associated with VWM, and this may decline relative to controls as task demands increase. These findings may help to explain why MS patient performance decreases as a function of effort on neuropsychological tests. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] Signal reconstruction in the presence of finite-rate measurements: finite-horizon control applicationsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2010Sridevi V. Sarma Abstract In this paper, we study finite-length signal reconstruction over a finite-rate noiseless channel. We allow the class of signals to belong to a bounded ellipsoid and derive a universal lower bound on a worst-case reconstruction error. We then compute upper bounds on the error that arise from different coding schemes and under different causality assumptions. When the encoder and decoder are noncausal, we derive an upper bound that either achieves the universal lower bound or is comparable to it. When the decoder and encoder are both causal operators, we show that within a very broad class of causal coding schemes, memoryless coding prevails as optimal, imposing a hard limitation on reconstruction. Finally, we map our general reconstruction problem into two important control problems in which the plant and controller are local to each other, but are together driven by a remote reference signal that is transmitted through a finite-rate noiseless channel. The first problem is to minimize a finite-horizon weighted tracking error between the remote system output and a reference command. The second problem is to navigate the state of the remote system from a nonzero initial condition to as close to the origin as possible in finite-time. Our analysis enables us to quantify the tradeoff between time horizon and performance accuracy, which is not well studied in the area of control with limited information as most works address infinite-horizon control objectives (e.g. stability, disturbance rejection). Copyright © 2009 John Wiley & Sons, Ltd. [source] Role of the Clinical Breast Examination in Breast Cancer ScreeningJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 7 2001Does This Patient Have Breast Cancer? QUESTION: The authors, in an article for the JAMA section on the rational clinical examination, consider the evidence on whether and how to use clinical breast examination as a cancer screening technique. BACKGROUND: Breast cancer is a common disease, particularly in older women. The authors note that by age 70 the annual incidence of breast cancer is one in 200 women. Breast cancer survival is strongly influenced by the stage of the disease at the time of diagnosis. As a result, it is important to consider how best to screen for this disease. In recent years there has been considerable attention in the clinical literature and in the popular media paid to the screening strategies of breast self-examination and of screening mammography, but somewhat less to the potential role of the breast examination by the healthcare provider. In actual clinical practice, the same woman may be the recipient of any, none, or all of these screening modalities. The best way to combine these screening strategies, particularly in the case of the older woman, remains a subject of some uncertainty and controversy. DATA SOURCES: Data were obtained from a MEDLINE search of the English-language literature for 1966 through 1997 and additional articles as identified by the authors. STUDY SELECTION CRITERIA: In their evaluation of the effectiveness of clinical breast examination, the authors included both controlled trials and case-controlled studies in which clinical breast examination was used as a component of the screening. Study of breast examination technique considered both clinical studies and studies using silicone breast models. DATA EXTRACTION: The combined data from the trials included information on approximately 200,000 women who received a breast cancer screening intervention (mammography and/or clinical breast examination). However, none of the studies made the direct comparison of a group receiving clinical breast examination as a sole intervention with a control group that did not receive any screening. Data on the utility of clinical breast examination were partially derived from studies where that screening modality was used in combination with mammography. MAIN RESULTS: A number of trials of cancer screening have demonstrated a reduction in mortality from the use of mammography and clinical breast examination as combined screening strategies compared with no screening, with the inference that the reduction in mortality comes from the earlier detection of breast cancer. The percentage of the detected cancers that are detected in the trials by clinical breast examination despite having been missed on mammography varies across the trials from a low of 3% of the detected cancers to a high of 45%. It is speculative whether the marginal contribution of clinical breast examination to the mortality reduction in these screening trials corresponds to the percentage of cancers detected by clinical breast examination alone. In most of the clinical trials, the technique of breast examination reportedly was not well described. It is unclear therefore how much the technique of breast examination used varied within and among the clinical trials. Data from studies using examinations of breast models made of silicone demonstrated that test performance accuracy correlated with a lengthier breast examination, better breast examination technique, and perhaps with examiner experience. The report includes data from six comparator studies and from two demonstration projects. Of the six comparator studies, four compared a screened population with an unscreened population and two compared different intensities of screening strategies. None of the eight clinical trials was directed to a geriatric population and in fact older women were excluded by upper age entry criteria from the six comparator studies. (The upper age limit for study entry in the six comparator studies varied from 49 to 64.) CONCLUSION: The authors drew on the pooled results of these eight studies to conclude that clinical breast examination has a sensitivity of 54% (95% confidence interval, 48.3,59.8) and a specificity of 94% (95% confidence interval, 90.2,96.9). The authors conclude that screening clinical breast examination should be done for women age older than 40. [source] The Effects of Fetal Alcohol Syndrome on Response Execution and Inhibition: An Event-Related Potential StudyALCOHOLISM, Issue 11 2009Matthew J. Burden Background:, Both executive function deficits and slower processing speed are characteristic of children with fetal alcohol exposure, but the temporal dynamics of neural activity underlying cognitive processing deficits in fetal alcohol spectrum disorder have rarely been studied. To this end, event-related potentials (ERPs) were used to examine the nature of alcohol-related effects on response inhibition by identifying differences in neural activation during task performance. Methods:, We recorded ERPs during a Go/No-go response inhibition task in 2 groups of children in Cape Town, South Africa (M age = 11.7 years; range = 10 to 13),one diagnosed with fetal alcohol syndrome (FAS) or partial FAS (FAS/PFAS; n = 7); the other, a control group whose mothers abstained or drank only minimally during pregnancy (n = 6). Children were instructed to press a "Go" response button to all letter stimuli presented except for the letter "X," the "No-go" stimulus, which occurred relatively infrequently. Results:, Task performance accuracy and reaction time did not differ between groups, but differences emerged for 3 ERP components,P2, N2, and P3. The FAS/PFAS group showed a slower latency to peak P2, suggesting less efficient processing of visual information at a relatively early stage (,200 ms after stimulus onset). Moreover, controls showed a larger P2 amplitude to Go versus No-go, indicating an early discrimination between conditions that was not seen in the FAS/PFAS group. Consistent with previous literature on tasks related to cognitive control, the control group showed a well-defined, larger N2 to No-go versus Go, which was not evident in the FAS/PFAS group. Both groups showed the expected larger P3 amplitude to No-go versus Go, but this condition difference persisted in a late slow wave for the FAS/PFAS group, suggesting increased cognitive effort. Conclusions:, The timing and amplitude differences in the ERP measures suggest that slower, less efficient processing characterizes the FAS/PFAS group during initial stimulus identification. Moreover, the exposed children showed less sharply defined components throughout the stimulus and response evaluation processes involved in successful response inhibition. Although both groups were able to inhibit their responses equally well, the level of neural activation in the children with FAS/PFAS was greater, suggesting more cognitive effort. The specific deficits in response inhibition processing at discrete stages of neural activation may have implications for understanding the nature of alcohol-related deficits in other cognitive domains as well. [source] Prenatal Alcohol Exposure Affects Frontal,Striatal BOLD Response During Inhibitory ControlALCOHOLISM, Issue 8 2007Susanna L. Fryer Background: Prenatal alcohol exposure can lead to widespread cognitive impairment and behavioral dysregulation, including deficits in attention and response inhibition. This study characterized the neural substrates underlying the disinhibited behavioral profile of individuals with fetal alcohol spectrum disorders (FASD). Methods: Children and adolescents (ages 8,18) with (n=13) and without (n=9) histories of heavy prenatal alcohol exposure underwent functional magnetic resonance imaging while performing a response inhibition (go/no-go) task. Results: Despite similar task performance (mean response latency, performance accuracy, and signal detection), blood oxygen level-dependent (BOLD) response patterns differed by group. Region-of-interest analyses revealed that during portions of the behavioral task that required response inhibition, alcohol-exposed participants showed greater BOLD response across prefrontal cortical regions (including the left medial and right middle frontal gyri), while they showed less right caudate nucleus activation, compared with control participants. Conclusions: These data provide an account of response inhibition-related brain functioning in youth with FASD. Furthermore, results suggest that the frontal,striatal circuitry thought to mediate inhibitory control is sensitive to alcohol teratogenesis. [source] | ||||||||||