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Biomedical subjects

F B Wood

Publications and source records attributed to F B Wood.

At least 19 recordsLinked to original sources
PubMed2000

Cortical activity related to accuracy of letter recognition.

Previous imaging and neurophysiological studies have suggested that the posterior inferior temporal region participates in tasks requiring the recognition of objects, including faces, words, and letters; however, the relationship between accuracy of recognition and activity in that region has not been systematically investigated. In this study, positron emission tomography was used to estimate glucose metabolism in 60 normal adults performing a computer-generated letter-recognition task. Both a region of interest and a voxel-based method of analysis, with subject state and trait variables statistically controlled, found task accuracy to be: (1) negatively related to metabolism in the left ventrolateral inferior temporal occipital cortex (Brodmann's area 37, or ventrolateral BA 37) and (2) positively related to metabolism in a region of the right ventrolateral frontal cortex (Brodmann's areas 47 and 11, or right BA 47/11). Left ventrolateral BA 37 was significantly related both to hits and to false alarms, whereas the right BA 47/11 finding was related only to false alarms. The results were taken as supporting an automaticity mechanism for left ventrolateral BA 37, whereby task accuracy was associated with automatic letter recognition and in turn to reduced metabolism in this extrastriate area. The right BA 47/11 finding was interpreted as reflecting a separate component of task accuracy, associated with selectivity of attention broadly and with inhibition of erroneous responding in particular. The findings are interpreted as supporting the need for control of variance due to subject and task variables, not only in correlational but also in subtraction designs.

Adult↗
PubMed2000

Event-related potentials correlate with task-dependent glucose metabolism.

Cognitive processing is associated with brain electrical activity that is reflected in event-related potentials (ERP). ERP during a target detection task, and regional cerebral glucose metabolism (CMRglc) measured simultaneously, may be influenced by the same neurophysiologic processes. We tested the hypothesis that ERP factors could be directly correlated with CMRglc to derive functional brain maps of brain activity at 120, 160, 200, 280, and 400 ms following stimulus presentation in a target detection task. We controlled for the potential confounding effects of age, sex, and task accuracy, and correlate target-related and nontarget-related ERP separately. Increases and decreases in CMRglc at each time point were identified with statistical parametric mapping (P < 0.001, uncorrected). The 120- and 160-ms maps were the same for target and nontarget processing, while maps for 280 and 400 ms clearly distinguished between targets and nontargets. Extrinsic (early) cognitive processes that depend mainly on stimulus characteristics show less variation based on stimulus meaning (i.e., letter vs shape; target vs nontarget) than later (intrinsic) cognitive processes. These early effects are lateralized to the left hemisphere, for negative ERP factors, and positive ERP-PET correlations are more likely than negative ERP-PET correlations. Thus, brain areas related to task processing impact both ERP and CMRglc measures, suggesting a shared neurophysiologic mechanism for negative ERP factors and increased CMRglc. Direct statistical analysis of these two measures using statistical parametric mapping provides high spatial and temporal resolution in multisubject experiments, while requiring only a single (18)FDG PET scan per subject.

Adult↗
PubMed2000

Chromosome 6p influences on different dyslexia-related cognitive processes: further confirmation.

In this study, which is a continuation and an extension of an earlier study, we enrolled two new families (N=31) and recruited more individuals from the previously ascertained families (N=56). The eight multiplex families (N=171) presented in this study were ascertained from a sample of adult probands whose childhood reading history is well documented through archival information. Six phenotypes were constructed to span a range of dyslexia-related cognitive processes. These phenotypes were (1) phonemic awareness (of spoken words); (2) phonological decoding (of printed nonwords); (3) rapid automatized naming (of colored squares or object drawings); (4) single-word reading (orally, of printed real words); (5) vocabulary; and (6) spelling (of dictated words). In addition, the diagnosis of lifelong dyslexia was established by clinical means. Genotyping was done with nine highly polymorphic markers from the 6p22.3-6p21.3 region. The results of two- and multipoint identity-by-descent and identity-by-state analyses supported the importance of a putative locus in the D6S464-D6S273 region for a number of dyslexia-related cognitive deficits.

Adolescent↗
PubMed2000

Hypersexuality and hemiballism due to subthalamic infarction.

OBJECTIVE: A 70-year-old right-handed man presented with a subthalamic infarction followed by persistent hypersexuality and hemiballism. A lacunar infarction 1 cm in diameter was observed on magnetic resonance imaging. We hypothesized that metabolic abnormalities would be detected in cortical areas related to his neurobehavioral symptoms. BACKGROUND: Statistical validation of the regional metabolic changes that may relate to neuropsychiatric symptoms has been elusive. Relating metabolic changes to neuropsychiatric symptoms is especially important in unique neurobehavioral cases. METHOD: Quantitative fluorodeoxyglucose positron emission tomography was obtained for a single-subject comparison with scans from 60 healthy subjects. RESULTS: Substantial glucose hypometabolism (p <0.001, uncorrected; [df = 56]) was identified in the subthalamic nucleus at the site of the lacunar infarction. Hypermetabolism (p <0.01) was identified within the basal forebrain and temporal lobes, anterior cingulate and medial prefrontal cortices (areas previously associated with hypersexuality), and striatum (p <0.001) ipsilateral to the stroke (areas known to relate to hemiballism). CONCLUSIONS: Single-subject statistical parametric mapping may improve our understanding of unique neurobehavioral cases.

Aged↗
PubMed1997

Susceptibility loci for distinct components of developmental dyslexia on chromosomes 6 and 15.

Six extended dyslexic families with at least four affected individuals were genotyped with markers in three chromosomal regions: 6p23-p21.3, 15pter-qter, and 16pter-qter. Five theoretically derived phenotypes were used in the linkage analyses: (1) phonological awareness; (2) phonological decoding; (3) rapid automatized naming; (4) single-word reading; and (5) discrepancy between intelligence and reading performance, an empirically derived, commonly used phenotype. Two-point and multipoint allele-sharing analyses of chromosome 6 markers revealed significant evidence (P < 10(-6)) for linkage of the phonological awareness phenotype to five adjacent markers (D6S109, D6S461, D6S299, D6S464, and D6S306). The least compelling results were obtained with single-word reading. In contrast, with chromosome 15 markers, a LOD score of 3.15 was obtained for marker D15S143 at theta = 0.0 with single-word reading. Multipoint analyses with markers adjacent to D15S143 (D15S126, D15S132, D15S214, and D15S128) were positive, but none reached acceptable significance levels. Chromosome 15 analyses with the phonological awareness phenotype were negative. Parametric and nonparametric linkage analyses with chromosome 16 markers were negative. The most intriguing aspect of the current findings is that two very distinct reading-related phenotypes, reflecting different levels in the hierarchy of reading-related skills, each contributing to different processes, appear to be linked to two different chromosomal regions.

Adolescent↗
PubMed1997

Transitioning to the Internet: results of a National Library of Medicine user survey.

In late 1995, several months prior to the introduction of Internet Grateful Med, the National Library of Medicine (NLM) conducted a customer survey as part of its efforts to make a transition from Grateful Med to new forms of electronic information access and retrieval. A questionnaire survey was mailed to a sample of 2,500 online users randomly selected from domestic users (excluding fixed-fee users) who searched NLM databases during the second quarter of 1995. The final response rate was nearly 83% of eligible respondents. About 70% of NLM customers responding already had access to the Internet, and of those, more than 90% had access to the World Wide Web. However, only 26% of customers with Internet access were using the Internet to access NLM databases. Health care providers account for about 46% of NLM customers but, as a group, search NLM databases relatively infrequently even though they have higher-end equipment. Librarians and information professionals represent about one-fifth of NLM customers and are by far the most intensive users, but tend to have lower-end equipment. Overall, the survey results provide a strong basis for the transition to Internet-based delivery of NLM online database services, including Internet Grateful Med and the NLM family of World Wide Web sites. However, Internet access is uneven, especially in rural areas and at hospitals. This reinforces the need for continuing special outreach efforts directed at improving access for rural and hospital-based users and rural libraries, upgrading computer equipment for medical librarians, and training health care providers in more effective use of Internet-based biomedical information resources.

Chi-Square Distribution↗
PubMed1996

Differences in visuospatial judgement in reading-disabled and normal children.

Both visual and verbal impairments have been reported in two independent streams of research into the etiology of dyslexia or reading-disability. To address the question of the presence of either abnormality in reading-disabled children, visuospatial and phonological ability were assessed and contrasted in 39 Normal and 26 Reading-disabled children. To assess whether these deficits are unique to dyslexia, scores were also compared to those of a group of 12 Poor Readers ("garden-variety" backward readers with low IQs). The Benton Judgement of Line Orientation Test was used for its simplicity and clinical reliability: Reading-disabled subjects performed significantly worse than Normal readers (but similar to Poor Readers). Reading-disabled subjects performed worse for lines in the left-hemifield compared to Normal subjects and also had a greater tendency to scan the task in reverse order (left-to-right) from the usual right-to-left scanning pattern observed in the Normal group when performing this test. When both verbal and visuospatial variables were combined in a multiple regression analysis, 71% of reading variance could be accounted for. These results suggest that Reading-disabled children not only have poor phonological awareness, but they also show visuospatial deficits. However, poor performance on both these tasks was also observed in the group of Poor Readers, suggesting that these deficits are not unique to children with specific reading disability. The results lend further evidence to the hypothesis that reading disability cannot solely be attributed to left-hemisphere dysfunction resulting in phonological impairment. There are other behavioral deficits, possibly caused by a common mechanism, some of which, like visuospatial ability, can be measured by simple behavioral tests such as the Judgment of Line Orientation Test.

Child↗
PubMed1995

Temporal and spatial processing in reading disabled and normal children.

The ability to process temporal and spatial visual stimuli was studied to investigate the role these functions play in the reading process. Previous studies of this type have often been confounded by memory involvement, or did not take into account the evidence which suggests a visual transient deficient in some dyslexics. Normal (n = 39), reading disabled (n = 26), and backward reading children (n=12) were compared on a visual computer game, which consisted of a temporal and a analogous spatial dot counting task. Reading disabled children performed significantly worse than normal children on the Temporal Dot Task, but were only mildly impaired on the Spatial Dot Task, Backward readers were not significantly better than the reading disabled group on either task, suggesting that poor poor visual temporal processing is not specific to dyslexia. In a group of 93 children, a regression model including age, verbal IQ, phonological awareness, and visual temporal processing ability, predicted 73% of the variance of reading ability. The results suggest that dyslexics perform worse in tasks that require fast, sequential processing and that this impairment may be partially responsible for their reading difficulties.

Attention↗
PubMed1995

Verbal and visual problems in reading disability.

Most individuals interested in reading disability favor the view that disordered language processing is the main cause of children's reading problems and that visual problems are seldom, if ever, responsible. Nevertheless, in a preliminary study (Eden, Stein, & Wood, 1993) we showed that visuospatial and oculomotor tests can be used to differentiate children with reading disabilities from nondisabled children. In the present study we investigated a larger sample of children to see if these findings held true. Using 93 children from the Bowman Gray Learning Disability Project (mean age = 11.3 years; 54 boys, 39 girls), we compared the phonological and visuospatial abilities of nondisabled children (children whose reading at fifth grade rated a Woodcock-Johnson reading standardized score between 85 and 115), and children with reading disability (whose reading standardized score was below 85 on the Woodcock-Johnson). In addition to performing poorly on verbal tests, the children with reading disability were significantly worse than nondisabled children at many visual and eye-movement tasks. A high proportion of the variance (68%) in reading ability of both the nondisabled children and those with reading disability could be predicted by combining visual and phonological scores in a multiple regression. These results provide further support for the hypothesis that reading disability may, to some extent, result from dysfunction of the visual and oculomotor systems.

Brain↗
PubMed1995

Electrophysiological indicants of black-white discrimination performance for letter and non-letter patterns.

This study examined event-related potentials (ERPs) and behavioral measures, considered to be sensitive to the selective processing of black versus white letter and non-letter patterns, in a group of seventy-four randomly selected 6 to 8 year old children. Results demonstrated faster and more accurate behavioral performance on the experimental task for the letter than for the non-letter patterns. The ERP measures provided complementary information regarding this letter facilitation effect, indicating that the selective neural processing of letter as compared to non-letter patterns was present in the electrophysiological waveform within the initial 100-140 ms after stimulus presentation. Later ERP measures (200-260 and 500-600 ms post-stimulus) in response to the letter stimuli showed greater differences as a function of task relevance over the left than over the right hemisphere. The results from the present study indicate a remarkably early facilitative influence of stimulus type (letter versus non-letter patterns) on the luminance discrimination of these stimuli and are consistent with an overlap of linguistic and perceptual processing.

Automatism↗
PubMed1995

Event related potentials in adults diagnosed as reading disabled in childhood.

The purpose of this study was to identify electrophysiological correlates of reading disability (RD) in adults with psychometrically documented childhood reading histories. Specific a-priori hypotheses for these correlates were generated from the findings of Harter, Anllo-Vento, Wood & Schroeder (1988a); Harter, Diering & Wood (1988b). The subjects were 32 males with normal intelligence and no history of attention deficit disorder or current major psychopathology. Event related potentials were recorded over O1, O2, C3', C4', F3, and F4 to letter stimuli using an intralocation selective attention paradigm. Subjects with RD showed a general reduction in positivity starting at 150 ms and continuing up to 500 ms. The reduced positivity at left central P240 replicated the findings of Harter et al. (1988b) with children. However, adult RD was associated with more diffuse, bilateral reduction in electrophysiological response to all stimuli. A possible relationship between the bilaterality of the neural deficit and the severity of the dyslexia was proposed: that a bilateral deficit may be involved in severe cases.

Adult↗
PubMed1994

Differences in eye movements and reading problems in dyslexic and normal children.

It has been suggested that eye movement abnormalities seen in dyslexics are attributable to their language problems. In order to investigate this claim, we studied eye movements in dyslexic children, during several non-reading tasks. Dyslexic children were compared to normal and backward readers on measures of fixation, vergence amplitude, saccade and smooth pursuit. The results were compared to the children's phonological ability. Dyslexic children (n = 26) had significantly worse eye movement stability during fixation of small targets than normal children (n = 39). Vergence amplitudes were lower for dyslexics than for controls. A qualitative assessment of saccadic eye movements revealed that dyslexics exhibit fixation instability at the end of saccades. Assessment of smooth pursuit revealed poor smooth pursuit in the dyslexic group, particularly when pursuing a target moving from left to right. Dyslexic children also performed significantly worse than normal children on a test of phonological awareness (Pig Latin). Eye movement results were studied in the light of the findings on phonological awareness: dyslexics with small vergence amplitudes also always have poor phonemic awareness. However, poor fixation control is found in dyslexics with or without poor phonological ability. The backward reading children performed similar to the dyslexics on all tests, suggesting that the deficiencies observed in this study are not specific to children with dyslexia. The problems experienced by the children (revealed by a questionnaire) are in agreement with those measured in terms of eye movement recordings and phonemic awareness. Sex, handedness, IQ or the presence of attention deficit disorder (ADD) did not appear to influence the children's performances on any of the eye movement tasks. The presence of oculomotor abnormalities in a non-reading task strongly suggests that the underlying deficit in the control of eye movements seen in dyslexics is not caused by language problems alone.

Attention Deficit Disorder with Hyperactivity↗
PubMed1992

A reading level match study of nonword reading skills in poor readers with varying IQ.

This study evaluated the hypothesis that poor readers are characterized by poor nonword reading skills, but that a specific deficit, as opposed to a developmental lag, in nonword reading will be found only in subjects whose reading is discrepant from intellectual ability. To test this hypothesis, we measured nonword reading skills in 93 (64 male, 29 female) third-grade poor readers and 54 (37 male, 17 female) fifth-grade poor readers (with and without reading/IQ discrepancies) who were matched to 147 (81 male, 66 female) nondisabled first graders on word identification skills. Results showed third- and fifth-grade poor readers to be significantly more impaired than word-identification level match first graders on all measures on nonword reading. These findings were not related to the verbal IQ level within the poor reader groups and, thus, provide strong evidence for a deficit in nonword reading skills that is not explained by verbal intelligence.

Age Factors↗
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↗