Search PubMed⌕ Search

Biomedical subjects

F B Wood

Publications and source records attributed to F B Wood.

34 records · Page 2Linked to original sources
PubMed1991

Regional cerebral blood flow correlates of language processes in reading disability.

This series of studies tests the hypothesis of abnormal left hemisphere activation in reading-disabled subjects during language task performance. First, a left superotemporal focus of activation, as measured by regional cerebral blood flow, was found to be positively correlated with task accuracy in a group of 69 normal adults. Next, that left superotemporal activation was replicated in a second group of 83 adults whose childhood reading ability was known from standardized tests given in childhood. Finally, in that latter group, childhood reading ability was also found to be inversely correlated with focal activation in a more posterior, temporoparietal area of cortex. Adult reading outcome was statistically unrelated to this finding. The results are interpreted as suggesting a trait anomaly of left hemisphere cerebral activation in adults who were dyslexic as children and as providing an existence proof of individual differences in focal cortical activation sites during constant task demands.

Adolescent↗
PubMed1990

Neuropsychological profile of adult dyslexics.

One hundred and fifteen adults with well-documented childhood reading status underwent a series of neuropsychological tests including tests of memory, attention, phonological processing, and visual perceptual skills in an attempt to define the neuropsychological profile of dyslexia in adulthood. Compared to a normal nonreading disabled sample, subjects with a history of reading disability performed consistently poorer on most neuropsychological tests. However, after covarying for intelligence and socioeconomic status, only tests of rapid naming, phonological awareness, and nonword reading were significant discriminating measures. The hypothesis that deficits in phonological processing comprise the core cognitive deficits in adults with a history of reading disability was supported. Independent of current adult reading ability, measures of nonword reading, phonological awareness, and rapid naming serve as indicators of a childhood history of reading disability.

Adult↗
PubMed1990

Hypofrontal vs. hypo-Sylvian blood flow in schizophrenia.

Hypofrontality in schizophrenia has been a frequent but not consistent finding in regional cerebral blood flow studies. However, the contributions of subject and state variables such as age, education, task activation, and anxiety, some of which are known to influence blood flow profiles, have not been thoroughly examined in this population. Here, in a sample including 24 normal, 18 schizophrenic, 22 bipolar, and 13 unipolar depressive subjects, narrative prose memory deficit was found to distinguish both schizophrenic and bipolar subjects from normal controls. Further, when these subjects were engaged in repeated trials of a verbal recognition memory task, left hemisphere hypofrontal blood flow in the early stage of learning was related to narrative memory, independent of diagnostic group. In the late stage of learning, state anxiety was significantly associated with left hypofrontality, while right hypofrontality was significantly related to narrative memory--both findings again independent of diagnostic group. A focal suppression of left hemispheric peri-Sylvian activation (in Broca's and Wernicke's areas) uniquely characterized schizophrenia after taking into account variance due to age, education, gender, state anxiety, and verbal memory. It is concluded that a failure of left peri-Sylvian activation during memory task performance reflects a unique language-related focal deficit in schizophrenia.

Adolescent↗
PubMed1989

Long-term follow-up of a childhood amnesic syndrome.

In attempting to explain observed dissociations between impaired and preserved memory functioning in amnesia, various dichotomous memory systems (e.g., procedural versus declarative, episodic versus semantic, working versus reference memory) have often been employed. In such cases, the assumption has been that memory subserved by one system is preserved, while that of the other system is impaired. Cohen and Squire have suggested that in amnesia, declarative memory is impaired, although procedural memory is preserved. Long-term follow-up of a densely amnesic patient refutes this view by demonstrating significant anterograde learning of school subjects including reading, vocabulary, spelling, and arithmetic, all of which include some component of declarative memory. It appears that the procedural/declarative dichotomy is not adequate to explain preserved memory in amnesia.

Adolescent↗
PubMed1989

Event-related potentials, spatial orienting, and reading disabilities.

Event-related potentials (ERPs) were used to investigate the effects of visual-spatial orienting on selective neural processing in boys with learning disabilities. Twenty-seven 8-12 year old boys were classified into four groups depending on whether or not they had a reading disability or attention deficit disorder. Event-related potentials were recorded over the left and right occipital, central, and frontal cortical regions. The behavioral task required the subjects 1) to rapidly switch their attention from the center to the periphery of the visual field (spatial component), and 2) to selectively respond to a target versus a nontarget flash when the target was presented in the relevant visual field (nonspatial component). The amplitude of two ERP components was enhanced in response to relevant as compared to irrelevant stimuli. The enhancement of an early negative occipital-central component, which peaked 180-200 ms following targets (N1), indicated that selective neural processing associated with spatial attention could be switched in 600 ms. This enhancement of N1 was greater in boys with than without a reading disability, which implies that reading disability is associated with enhanced spatial attention. The enhancement of a later positive component, which peaked 300-340 ms following targets (P3), suggested that nonspatial target selection was reduced in boys with a reading disability, particularly over the left occipital hemisphere. Target relevance and reading disability also influenced trial-to-trial variability in the ERP waveform. The effects of reading disability on event-related potentials did not vary as a function of attention deficit disorder, indicating that these two disorders are distinct.

Arousal↗
PubMed1989

Cognitive deficits in reading disability and attention deficit disorder.

This paper presents data from three studies (a cross-sectional study of school-referred children, a test-retest study of subtypes of reading disabilities, and a study of a large, random sample of first graders) that focus on specifying the cognitive deficits associated with reading difficulties and separating them from those associated with attentional deficits. The cognitive deficits associated with difficulty in reading were consistent across samples, developmental levels, definitions, and subtypes of reading disabilities. With IQ, age, and sex controlled for, poor readers were significantly impaired on measures of naming and phonological awareness. The effects of attentional deficits were more variable and complex but were clearly separate from the reading disability effects.

Attention↗
PubMed1988

Separate brain potential characteristics in children with reading disability and attention deficit disorder: relevance-independent effects.

The effects of reading disability (RD) and attention deficit disorder (ADD) on event-related potentials (ERPs) were investigated in 52 boys between 8 and 12 years of age. There were four groups: 25 children without RD divided into two groups (17 without ADD and 8 with ADD) and 27 children with RD divided into two groups (11 without ADD and 16 with ADD). The children participated in three tasks ("games") designed to assess selective attention to the color black (vs white), to any of two letters (vs. two patterns), and to any of 12 letters (vs. 12 patterns). ERPs were recorded over the left and right occipital, central, and frontal hemispheres. Children with RD as compared to those without RD were characterized by the following ERPs: (1) a smaller amplitude positive wave at about 240 msec (P240) over the left central hemisphere: (2) a smaller amplitude positive wave at about 500 msec (P500) over the right central hemisphere: (3) a larger P500 over the right central hemisphere: (3) a larger P500 over both left and right occipital hemispheres: and (4) smaller within-subject-and-condition variability of ERP waveform. These effects did not differ significantly for the three games and, therefore, were not specific to letter processing per se. The effects of RD did not interact with the effects of ADD for the most part. The ERPs clearly indicated these two disorders, in part, involve different underlying brain processes.

Arousal↗
PubMed1988

Separate brain potential characteristics in children with reading disability and attention deficit disorder: color and letter relevance effects.

This experiment was on event-related potential (ERP) indicants of the selective neural processing of black vs. white and letter vs. nonletter stimuli in boys (8-12 years of age) with and without a reading disability (RD) and/or attentional deficit disorder (ADD). Selective neural processing was measured by the increase or difference in ERP amplitude in response to stimuli that were relevant as compared to irrelevant to the color or letter attention task. The 52 children that participated in the study constituted four groups: 25 normal reading children (17 without ADD and 8 with ADD), and 27 RD children (11 without ADD and 16 with ADD). ERPs were recorded over the left and right occipital, central, and frontal regions. Selective neural processing due to stimulus relevance was reduced in boys with RD as compared to normal readers. This reduced selectivity was indicated by a predominantly symmetrical reduction in the magnitude of a positive difference potential over the central regions, between 300 and 360 msec, and then by a left greater than right hemisphere reduction in the magnitude of a positive difference potential over the occipital regions, at about 400 msec. Task relevance increased the within-subject and condition variability of this occipital positive component and this effect was greater for boys without than with RD, particularly over the left hemisphere. Selective neural processing due to stimulus relevance was greater in boys with ADD as compared to those without ADD. This was indicated by an increase in the magnitude of a positive difference potential between 320 and 400 msec over the central and frontal regions and a slow, late, negative difference potential between 600 and 800 msec over the central and occipital regions. These ADD effects tended to be greater over the right than left hemisphere. The unique polarity, scalp distribution, and time course of the effects of RD as compared to ADD on ERPs to relevant stimuli clearly indicated these two disorders, in part, involve different underlying brain deficits.

Arousal↗
PubMed1987

Separate verbal memory and naming deficits in attention deficit disorder and reading disability.

In this study, verbal memory and naming abilities were investigated in reading disabled (RD) and control children who were characterized according to the presence or absence of attention deficit disorder (ADD). Results indicate that deficits in learning and memory for recently acquired information occur as a function of ADD rather than RD while deficits in naming are specific to RD rather than ADD. We conclude that ADD is a major source of additional and separate cognitive morbidity in RD children.

Attention Deficit Disorder with Hyperactivity↗
PubMed1982

Synesthesia. II. Psychophysical relations in the synesthesia of geometrically shaped taste and colored hearing.

The psychophysical function in two synesthetic subjects, one with geometrically shaped taste and the other with colored hearing, is investigated. Each synesthete is compared with three control subjects. Pilot studies are used to construct appropriate response domains. Compared to controls, synesthetes give a restricted set of responses that are also asymmetric with respect to the range of choices available in various subsets of the response domain. A combination of absolute and relative effects is also distinctive of synesthetic percepts. It is concluded that synesthesia is a distinct phenomenon unlike ordinary mediated associations, and occupies an intermediate position in the range of simple to complex brain mechanisms.

Adult↗
PubMed1980

Persistent retrograde memory deficit after transient global amnesia.

A 64-year-old woman suddenly had an attack of confusion and amnesia that suggested transient global amnesia. However, her loss of memory for recent events lasted more than ten days and was accompanied by psychomotor agitation and transient alteration of sexual behavior. The patient had no other neurologic signs during the episode. She recovered completely from the recent memory deficit, but was left with a persistent retrograde amnesia for a period of five to ten years and total amnesia for the acute episode. The EEG was suggestive of a left medial temporal lobe lesion.

Amnesia↗
PubMedDate not supplied

Evaluation of brain activity in FDG PET studies.

PURPOSE: A tool (Gemini) was developed for quantifying regions of interest (ROIs) in registered MR and PET data. Its use was validated through phantom and simulated studies. METHOD: Hot spheres were imaged in a phantom (3:1 and 5:1 target-to-nontarget ratios). The computerized 3D Hoffman brain phantom was used to simulate PET studies. Spherical local activity features of two diameters (4 and 10 mm) and five intensities (5, 15, 25, 50, and 100% increase over gray matter) were added to the data in the thalamus and Brodmann area 37. The data were reprojected into sinograms and blurred with a 7 mm kernel. Poisson noise was added, and the sinograms were then reconstructed and analyzed using both SPM96 and Gemini spherical ROIs. RESULTS: Based on phantom and simulated data, the 95th percentile of intensity within a Gemini ROI afforded a reasonable joint optimization of variance (reliability) and accuracy (validity). SPM96 and Gemini results were similar for the larger (10 mm) feature, but in this application, Gemini was more sensitive than SPM96 for the small feature (4 mm). CONCLUSION: Gemini, a tool for display and measurement of spherical ROIs in registered PET and MR data, is precise and accurate for testing hypotheses of differences in localized brain activity, comparing favorably with SPM96.

Brain↗
PubMedDate not supplied

Evaluating Internet end-to-end performance: overview of test methodology and results.

OBJECTIVE: An evaluation of Internet end-to-end performance was conducted for the purpose of better understanding the overall performance of Internet pathways typical of those used to access information in National Library of Medicine (NLM) databases and, by extension, other Internet-based biomedical information resources. DESIGN: The evaluation used a three-level test strategy: 1) user testing to collect empirical data on internet performance as perceived by users when accessing NLM Web-based databases, 2) technical testing to analyze the Internet paths between the NLM and the user's desktop computer terminal, and 3) technical testing between the NLM and the World Wide Web ("Web") server computer at the user's institution to help characterize the relative performance of Internet pathways. MEASUREMENTS: Time to download the front pages of NLM Web sites and conduct standardized searches of NLM databases, data transmission capacity between NLM and remote locations (known as the bulk transfer capacity [BTC]), "ping" round-trip time as an indication of the latency of the network pathways, and the network routing of the data transmissions (number and sequencing of hops). RESULTS: Based on 347 user tests spread over 16 locations, the median time per location to download the main NLM home page ranged from 2 to 59 seconds, and 1 to 24 seconds for the other NLM Web sites tested. The median time to conduct standardized searches and get search results ranged from 2 to 14 seconds for PubMed and 4 to 18 seconds for Internet Grateful Med. The overall problem rate was about 1 percent; that is, on the average, users experienced a problem once every 100 test measurements. The user terminal tests at five locations and Web host tests at 13 locations provided profiles of BTC, RTT, and network routing for both dial-up and fixed Internet connections. CONCLUSION: The evaluation framework provided a profile of typical Internet performance and insights into network performance and time-of-day/day-of-week variability. This profile should serve as a frame of reference to help identify and diagnose connectivity problems and should contribute to the evolving concept of Internet quality of service.

Evaluation Studies as Topic↗
PubMedDate not supplied

Emerging issues in the genetics of dyslexia: a methodological preview.

A review of the classic and recent evidence on the genetics of reading disability (RD) shows encouraging progress, and accumulating evidence of genetic risk factors that operate within families and are separately localizable to more than one chromosomal region. The accelerating pace of these findings, however, suggests the need to consider some methodological issues about the design and interpretation of current and future studies. A major issue is the shape of the distribution of reading ability in the population, and we offer three tests of increasing rigor for determining whether those distributions are categorical, and hence not suitable for analyses that depend on the assumption of a continuous normal distribution. These tests are as follows: a nonnormal preponderance of cases with RD (i.e., the hump in the lower end of the distribution); a difference in the within-group variance-covariance matrices for typical readers compared to those with RD; and a correlation between a neurogenetically relevant criterion and a categorical reading variable that is larger than the correlation between the same criterion and a continuous version of the same reading variable. We emphasize also the importance of interactive relationships between multiple genetic loci, the variations in genotypic range as well as type of affectedness, the need to account for remediation variance, and the importance of lifespan changes in the phenotypes.

Causality↗
PubMedDate not supplied

Selective predictive value of rapid automatized naming in poor readers.

This study considers the differential predictive value of rapid naming tests for various aspects of later reading, where the differential is between nondisabled and poor readers. Two large-N longitudinal samples of students who have been evaluated from third through eighth grades are studied: (a) a randomly accessed, normally distributed group including students with varying degrees of reading ability (N = 154), and (b) a group of poor readers whose single-word reading in third grade is at or below the population 10th percentile (N = 64). Outcomes in fifth and eighth grade were measured in both groups. Single-word reading in both grades was strongly predicted from third-grade rapid naming only within the poor readers, even when IQ, socioeconomic status, and third-grade single-word reading were statistically controlled. Although rapid naming had predictive value within the large, normally distributed group, its predictive power was entirely absent in the average-reading nondisabled students who were between the 10th and 90th percentiles (n = 122). The fact that rapid naming has predictive power only for poor readers but not for average readers is interpreted as suggesting that impaired readers are qualitatively different from the normal-reading population and are not simply the "tail" of a normal distribution of reading ability. It also seems that it is the automaticity of retrieval, not the knowledge of names itself (as in confrontational naming tasks), that gives the predictive power in rapid naming. These data are considered in light of the one- and two-factor theories of the underlying processes involved in reading disability or dyslexia.

Anomia↗