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At least 667 records · Page 37Linked to original sources

PubMed2003

The self-to-other ratio applied as a phonation detector for voice accumulation.

A new method for phonation detection is presented. The method utilises two microphones attached near the subject's ears. Simplified, phonation is assumed to occur when the signals appear mainly in-phase and at equal amplitude. Several signal processing steps are added in order to improve the phonation detection, and finally the original signal is sorted in separate channels corresponding to the phonated and non-phonated instances. The method is tested in a laboratory setting to demonstrate the need for some of the stages of the signal processing and to examine the processing speed. The resulting sound file allows for measurement of phonation time, speaking time and fundamental frequency of the subject and sound pressure level of the subject's voice and the environmental sounds separately. The present implementation gives great freedom for adjustment of analysis parameters, since the microphone signals are recorded on DAT tape and the processing is performed off-line on a PC. In future versions, a voice accumulator based on this principle could be designed in order to shorten analysis time and thus make the method more appropriate for clinical use.

Equipment Design↗

PubMed1994

Smoking and Raven IQ.

Nicotine has recently been shown to enhance measures of information processing speed including the decision time (DT) component of simple and choice reaction time and the string length measure of evoked potential waveform complexity. Both (DT and string length) have been previously demonstrated to correlate with performance on standard intelligence tests (IQ). We therefore hypothesised that nicotine is acting to improve intellectual performance on the elementary information processing correlates of IQ. In the current experiment we tested this hypothesis using the Raven Advanced Progressive Matrices (APM) test. APM scores were significantly higher in the smoking session compared to the non-smoking session, suggesting that nicotine acts to enhance physiological processes underlying performance on intellectual tasks.

Adolescent↗

PubMed2006

A cross-sectional study to investigate long-term cognitive function in people with treated pituitary Cushing's disease.

INTRODUCTION: It has been proposed that exposure to high levels of endogenous steroids in untreated pituitary Cushing's disease damages hippocampal structures leading to impairment in learning and memory processes. We hypothesised that patients with treated pituitary Cushing's disease would perform significantly worse on tests of cognitive ability than those with nonfunctioning pituitary adenomas. DESIGN: Sixteen adults with pituitary Cushing's disease (PCD) and 16 adults with non-functioning pituitary adenomas (NFA) undertook the following comprehensive neuropsychological assessments: National Adult Reading Test (NART: premorbid abilities), California Verbal Learning Test (CVLT 2 UK: learning and recall), Stroop (executive functioning), Trail-Making Test (TMT: executive functioning and attention), Adult Memory and Information Processing Battery (AMIPB: Information Processing Speed and Story Recall subtests). RESULTS: There was no significant difference in premorbid IQ scores (NFA mean=101 SD=13; PCD mean=102, SD=13), in verbal learning nor any significant difference in the percentage of verbal material retained in story recall (AMIPB). Performance on higher executive tasks Stroop and TMT and on measures of information processing was similar. However, there were significant decrements between some mean scores for both groups and published normative data with a clear association between higher HADS depression scores and impaired objective memory and attention which was not specific to PCD. CONCLUSIONS: We found no difference in cognitive function between patients with PCD and NFA. The results suggest a discrepancy between patients' subjective perception of functional cognitive impairments and objective findings on psychometric testing and point to the influence of affective symptoms on cognitive performance, particularly in Cushing's disease.

Adult↗

PubMed1984

Effects of methylphenidate (Ritalin) on information processing in hyperactive children.

The effect of methylphenidate on information-processing efficiency was studied in 12 hyperactive, nonretarded children. Performance on six efficiency tasks (Posner Letter Matching, Reaction Time, Memory Search, Category Verification, Item Identification, and Word-Span) and a general measure of on-task behavior were compared for children receiving methylphenidate or a placebo. The median drug dosage was .38 mg/kg, and it was ingested 1 1/2 hours prior to testing. Children blind to the drug-placebo condition were tested on 4 days. In general, methylphenidate-related improvements in attention to on-task behaviors were found. An overall analysis of processing speed suggested that methylphenidate improved efficiency. Methylphenidate significantly decreased reaction times to simple and complex stimulus arrays; differences due to the drug remained even when on-task attentive behaviors were statistically removed. Significantly fewer identification errors occurred on the Posner task in the methylphenidate condition. Results indicated that methylphenidate improved general attentional behaviors and positively influenced processes that define perceptual efficiency.

Adolescent↗

PubMed1983

Age, presentation rate, and the effectiveness of structural and semantic recall cues.

To replicate the results of research on age-related differences in the effectiveness of structural and semantic memory cues, 18 young, 18 middle-aged, and 18 elderly adults recalled three 20-item lists aided by category labels, or the initial two letters of each word, or no cues. Lists were presented at 1.5 or 4 sec presentation rates to evaluate the effects of changes in processing speed on age-related trends in cue effectiveness. Semantic cues were most effective in improving recall at all three age levels; structural cues produced intermediate levels of recall facilitation. There was no indication of reduced effectiveness of semantic cues with increases in age and presentation rate, suggesting factors other than age-related changes in the depth of processing are responsible for developmental differences in memory.

Adult↗

PubMed1992

Vision, aging, and driving: the problems of older drivers.

Although there are well-recognized declines in visual functioning with age, their contribution to the problems of older persons on tasks in the natural environment, including driving, are largely unknown. Adults ranging in age from 22-92 years were surveyed in regard to their visual difficulties when driving and performing everyday tasks. The visual problems of drivers increased with age along five different visual dimensions: unexpected vehicles, vehicle speed, dim displays, windshield problems, and sign reading. Several of the age-related visual problems that were reported appear to be related to the types of automobile accidents more common among older drivers. The study also replicated the findings from an earlier investigation of non-driving tasks that showed visual declines with age on five dimensions: visual processing speed, light sensitivity, dynamic vision, near vision and visual search. These findings indicate promising areas of research regarding the effects of visual aging on tasks in the natural environment.

Adult↗

PubMed1988

Anterograde and retrograde amnesia in patients with chronic progressive multiple sclerosis.

The performance of 38 patients with chronic progressive multiple sclerosis was compared with that of 26 age- and education-matched controls on a battery of tests of information-processing speed, verbal fluency, naming, egocentric perception, and anterograde and remote memory. Although there were marked differences in the extent and severity of cognitive disturbance among individual patients, as a group they were impaired compared with controls on all measures. Deficits were most striking on the Symbol-Digit Modalities Test and the verbal fluency measures, tests that require rapid information processing. More than 75% of the patients scored below the tenth percentile for controls on the Symbol-Digit Modalities Test, while 61% scored below the tenth percentile on verbal fluency. Memory disturbances were also common. More than 45% of the patients scored below the tenth percentile. The proportion of impaired patients was quite similar for anterograde and remote memory tests and for recall and recognition procedures. The pattern of memory disturbance and slowed information processing resembled deficits generally observed in subcortical dementias, such as Huntington's disease, but in addition, the patients with multiple sclerosis showed naming difficulties that are usually associated with cortical dementias, such as Alzheimer's disease.

Adult↗

PubMed2006

Determination of the potential benefit of time-frequency gain manipulation.

OBJECTIVE: The purpose of this study was to determine the maximum benefit provided by a time-frequency gain-manipulation algorithm for noise-reduction (NR) based on an ideal detector of speech energy. The amount of detected energy necessary to show benefit using this type of NR algorithm was examined, as well as the necessary speed and frequency resolution of the gain manipulation. DESIGN: NR was performed using time-frequency gain manipulation, wherein the gains of individual frequency bands depended on the absence or presence of speech energy within each band. Three different experiments were performed: (1) NR using ideal detectors, (2) NR with nonideal detectors, and (3) NR with ideal detectors and different processing speeds and frequency resolutions. All experiments were performed using the Hearing-in-Noise test (HINT). A total of 6 listeners with normal hearing and 14 listeners with hearing loss were tested. RESULTS: HINT thresholds improved for all listeners with NR based on the ideal detectors used in Experiment I. The nonideal detectors of Experiment II required detection of at least 90% of the speech energy before an improvement was seen in HINT thresholds. The results of Experiment III demonstrated that relatively high temporal resolution (<100 msec) was required by the NR algorithm to improve HINT thresholds. CONCLUSIONS: The results indicated that a single-microphone NR system based on time-frequency gain manipulation improved the HINT thresholds of listeners. However, to obtain benefit in speech intelligibility, the detectors used in such a strategy were required to detect an unrealistically high percentage of the speech energy and to perform the gain manipulations on a fast temporal basis.

Acoustic Stimulation↗

PubMed1989

Use of a neural net computer system for analysis of flow cytometric data of phytoplankton populations.

Flow cytometry has been used over the past 5 years to begin detailed exploration of the distribution and abundance of picoplankton in the oceans. Light scattering and fluorescence measurements on individual plankton cells in seawater samples allow construction of population signatures from size and pigment characteristics. The use of "list mode" data has made these studies possible, but on-shore analysis of copious data does not permit on-site reexamination of important or unexpected observations, and overall effort is greatly handicapped by data analysis time. Here we describe the application of neural net computer technology to the analysis of flow cytometry data. Although the data used in this study are from oceanographic research, the results are general and should be directly applicable to flow cytometry data of any sort. Neural net computers are ideally suited to perform the pattern recognition required for the quantitative analysis of flow cytometry data. Rather than being programmed to perform analysis, the neural net computer is "taught" how to analyze the cell populations by presenting examples of inputs and correct results. Once the system is "trained," similar data sets can be analyzed rapidly and objectively, minimizing the need for laborious user interaction. The neural network described here offers the advantages of 1) adaptability to changing conditions and 2) potential real-time analysis. High accuracy and processing speed near that required for real-time classification have been achieved in a software simulation of the neural network on a Macintosh SE personal computer.

Computer Systems↗

PubMed1992

Regularized linear method for reconstruction of three-dimensional microscopic objects from optical sections.

The inverse problem involving the determination of a three-dimensional biological structure from images obtained by means of optical-sectioning microscopy is ill posed. Although the linear least-squares solution can be obtained rapidly by inverse filtering, we show here that it is unstable because of the inversion of small eigenvalues of the microscope's point-spread-function operator. We have regularized the problem by application of the linear-precision-gauge formalism of Joyce and Root [J. Opt. Soc. Am. A 1, 149 (1984)]. In our method the solution is regularized by being constrained to lie in a subspace spanned by the eigenvectors corresponding to a selected number of large eigenvalues. The trade-off between the variance and the regularization error determines the number of eigenvalues inverted in the estimation. The resulting linear method is a one-step algorithm that yields, in a few seconds, solutions that are optimal in the mean-square sense when the correct number of eigenvalues are inverted. Results from sensitivity studies show that the proposed method is robust to noise and to underestimation of the width of the point-spread function. The method proposed here is particularly useful for applications in which processing speed is critical, such as studies of living specimens and time-lapse analyses. For these applications existing iterative methods are impractical without expensive and/or specially designed hardware.

Computer Simulation↗

PubMed1996

Inhibition of return is not detected using illusory line motion.

Inhibition of return (IOR) is the name that has been assigned to a response time (RT) delay to a stimulus presented at a recently stimulated spatial location. A commonly held explanation for the origins of IOR is that perceptual processing in inhibited and that this inhibition translates into slower RT. Three experiments with 10 subjects were used to directly test this perceptual explanation. The first two experiments assessed the level of perceptual facilitation present in the IOR paradigm using the frequency and latency of illusory line motion judgments. Contrary to the predictions of the perceptual view, the line motion and RT measures revealed only speeded processing at previously stimulated spatial locations. Experiment 3 required a simple detection response and used the same stimulus and timing parameters as those in Experiments 1 and 2. IOR was present, replicating the recent finding that judgments based on perceptual qualities of the stimulus do not demonstrate a RT delay, whereas simple detection tasks do show RT inhibition at previously stimulated locations. These findings are discussed in relation to a number of hypotheses about the origin of the RT delay.

Humans↗

PubMed1999

Verbal and spatial short-term memory: common sources of developmental change?

Verbal and spatial span, articulation and tapping rate, and verbal and spatial speed-of-search tasks were administered to sixty 6- to 12-year-olds. A variance-partitioning procedure was then used to identify age-related and age-invariant components of variance in span. Outcomes were very similar for verbal and spatial span, in particular, (i) most of the age-related variance was shared by the speed-of-search and rate predictors, (ii) articulation rate provided an age-independent contribution, (iii) changing-state versions of predictor tasks did not account for variance over steady-state versions, and (iv) predictors of the same modality as the span task did not outperform predictors of the other modality. We conclude that verbal and spatial short-term memory appear to rely on similar processes when serial recall is required and that developments in span are closely tied to increases in processing speed.

Age Factors↗

PubMed1996

Cognitive slowing in patients with acquired brain damage: an experimental approach.

Nine brain-damaged patients (19-54 years old) with "cognitive slowing", and 10 healthy subjects (26-56 years old) were tested with a slightly modified version of a Sternberg memory task (varied-set procedure). Cognitive slowing in the sense of reduced information-processing speed is reflected by mean RTs and slopes and intercepts derived from the RTs as a function of memory set size. Patients showed a marked increase of these parameters. While the results obtained from the control subjects are in accordance with typical Sternberg findings, patients showed no parallel regression lines for positive and negative responses. As an alternative explanation for this result an extended "self-terminating" process is proposed that also appears to be helpful in explaining the overall cognitive slowing in the patients.

Adult↗

PubMed2005

Corpus callosal microstructural integrity influences interhemispheric processing: a diffusion tensor imaging study.

Normal aging and chronic alcoholism result in disruption of brain white matter microstructure that does not typically cause complete lesions but may underlie degradation of functions requiring interhemispheric information transfer. We examined whether the microstructural integrity of the corpus callosum assessed with diffusion tensor imaging (DTI) would relate to interhemispheric processing speed. DTI yields estimates of fractional anisotropy (FA), a measure of orientation and intravoxel coherence of water diffusion usually in white matter fibers, and diffusivity ( ), a measure of the amount of intracellular and extracellular fluid diffusion. We tested the hypothesis that FA and would be correlated with (i) the crossed-uncrossed difference (CUD), testing visuomotor interhemispheric transfer; and (ii) the redundant targets effect (RTE), testing parallel processing of visual information presented to each cerebral hemisphere. FA was lower and higher in alcoholics than in controls. In controls but not alcoholics, large CUDs correlated with low FA and high in total corpus callosum and regionally in the genu and splenium. In alcoholics but not controls, small RTEs, elicited with equiluminant stimuli, correlated with low FA in genu and splenium and high in the callosal body. The results provide in vivo evidence for disruption of corpus callosum microstructure in normal aging and alcoholism that has functional ramifications for efficiency in interhemispheric processing.

Aging↗

PubMed2003

Implicit learning deficit in children with developmental dyslexia.

Several neuropsychological deficits have been reported as characteristic of the cognitive profile of dyslexic children. Phonological and visual processing are often impaired as well as auditory processing, attention and information processing speed. We investigated whether implicit learning, is impaired in dyslexic children and adolescents. Tests of implicit and declarative learning were administered to 18 clinically defined dyslexics and 18 similar age controls. Dyslexics showed a reduced learning rate in the implicit but not in the declarative task, suggesting a specific deficit of implicit learning. Although alternative hypothesis cannot be ruled out, considering that implicit learning is a cognitive function primarily processed by the cerebellum and that recent neurological and physiological data suggest a cerebellar dysfunction in dyslexia, the present results suggest an impairment of cerebellar system in reading disabilities.

Analysis of Variance↗

PubMed2003

Cognitive function in relation to hearing aid use.

Two experiments were conducted to investigate possible relationships between cognitive function and hearing aid use. In Experiment 1, 72 first-time hearing aid users were tested for speech recognition in noise (Hagerman sentence test) with and without hearing aids. Cognitive function was assessed by tests of working memory (reading span test) and verbal information-processing speed. The results indicate that, after controlling for age and hearing loss, significant correlations exist between the measures of cognitive performance and speech recognition in noise, both with and without hearing aids. High cognitive performance was associated with high performance in the speech recognition task. In Experiment 2, 17 first-time hearing aid users with either high or low working-memory capacity tested an experimental hearing aid which processed the sound differently depending on whether or not speech was detected. The results revealed that those with high working-memory capacity were better than those with low capacity at identifying and reporting the specific processing effects of the aid. This may have implications for how reported results should be interpreted in a research context, how a person's rehabilitation needs are formulated, and how hearing aid controls should be supervised. In conclusion, careful attention should be paid to the cognitive status of listeners, as it can have a significant influence on their ability to utilize their hearing aids.

Adult↗

PubMed1998

A kindred affected by cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). A 2-year neuropsychological follow-up.

We report a 2-year prospective neuropsychological study of five asymptomatic subjects with magnetic resonance imaging (MRI) abnormalities from an Italian kindred affected by cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). These subjects completed tests for attention capacities, processing speed, abstract thinking, short-term memory, learning and constructional praxis. Seven normal subjects matched for age and education, belonging to the same pedigree and not having MRI hyperintensities were examined as controls. The results did not show significant differences between asymptomatic subjects and normal controls. Cognitive performance of asymptomatic subjects did not deteriorate during a 2-year follow-up. Our findings suggest that, at this stage of the disease process, the presence of diffuse leukoencephalopathy does not imply subtle cognitive defects.

Adult↗

PubMed2000

Cognitive and linguistic correlates of children's discourse after closed head injury: a three-year follow-up.

The discourse of 91 children who had sustained severe (n = 68) or mild (n = 23) closed head injury (CHI) was examined at least three years postinjury. The groups' retellings of a narrative story were analyzed according to two domains, information and language. In comparison to the mild CHI group, the severe group produced stories characterized by reduced content and information, impaired organization, fewer words, and less complex sentences. The relationships between discourse production and the groups' performance on measures of language, executive function, memory, and processing speed were examined. Correlations were found between discourse production and general verbal ability including verbal fluency. Correlations were also found for discourse performance and executive function measures associated with problem solving and working memory. Site and extent of lesion were not useful in predicting discourse production. These findings indicate that children who sustain a severe closed head injury during early to middle childhood are at risk for persisting deficits in discourse processing and other cognitive abilities.

Adolescent↗