PubMed Health⌕ Search

Biomedical subjects

W Ray

Publications and source records attributed to W Ray.

14 recordsLinked to original sources
PubMed2004

Practice-related modulations of force enslaving and cortical activity as revealed by EEG.

OBJECTIVE: To examine the role of practice in the modification of force enslaving and motor-related cortical potentials using finger force production tasks. This study follows-up previous studies in our laboratory using experienced piano players. METHODS: Two experiments were performed. In Expt. 1, 6 subjects participated in a pre and post EEG session separated by 12 practice sessions which were conducted 3 days a week for 4 weeks. With visual feedback regarding the accuracy of force output, subjects produced one of two force levels with either their ring or index finger. Experiment 2 followed a similar procedure to that of Expt. 1 with additional visual feedback to the degree of finger independency. Both behavioral (isometric force output) and EEG data preceding and accompanying force responses were measured. RESULTS: In Expt. 1 we found that forced enslaving increased along with improved accuracy following 4 weeks of practice. We found a reduction of motor potential (MP) amplitude for the index but not the ring finger following practice. Experiment 2 showed an increase in accuracy and reduction in force enslaving after practice with adequate feedback. The amplitude of MP for the index finger also decreased after practice as in Expt. 1. In contrast, the amplitude of MP for the ring finger increased after practice. CONCLUSIONS: The present study extends our earlier work with piano players and shows the role of practice in modifying behavioral and cortical measures. The concluding theme emergent from our studies is that individuated finger control is not hard-wired, but rather plastic and greatly influenced by deliberate practice. SIGNIFICANCE: This research supports the idea that experience and practice are associated with changes in behavioral and EEG correlates of task performance and have clinical implications in disorders such as stroke or dystonia. Practice-related procedures offer useful approaches to rehabilitation strategies.

Adult↗
PubMed2002

The role of sub-maximal force production in the enslaving phenomenon.

When individuals perform a force task involving only one finger, they involuntarily move other fingers as well. This phenomenon is referred to as the enslaving force or the interdependency of fingers. Given that previous literature on the enslaving force has focused on maximal isometric force production, the present research was designed to study the role of sub-maximal force production in the enslaving phenomenon. To this end, we examined behaviorally three levels of force production with a constant rate of force development. We also examined the temporal organization of enslaving separating the achievement of the desired force (ramp phase) and its maintenance (static phase). During the static phase we found: (i) the amount of enslaving increased with the increment of nominal force level whether the index, middle, ring or little fingers were used as the master finger; (ii) enslaving is strongest in the finger directly adjacent to the master finger; and (iii) in terms of enslaving, the index finger was more 'independent' than the other three fingers, regardless of nominal force produced, followed by the little, middle, and ring fingers. In terms of temporal organization, we found that the time-lag of activation of 'slave fingers' during the ramp phase was reduced as the amount of force level increased. Overall, our data suggest that enslaving effect is a task specific phenomenon and depends on the amount of force produced by the master finger.

Adult↗
PubMed2002

Movement-related EEG potentials are force or end-effector dependent: evidence from a multi-finger experiment.

OBJECTIVES: This study examined behavioral and electrocortical responses in producing 3 levels of force (25, 50 and 75% of MVC) at a constant rate of force development with each of 4 fingers both during the achievement of the desired force (ramp phase) and its maintenance (static phase). We were particularly interested in describing in more detail the interaction between nominal force and finger on various components of movement-related potential (MRP) associated with preparation and execution of isometric force production tasks. METHODS: Our experimental design systematically controlled the rate of force development while nominal force level was experimentally manipulated during isometric force production tasks. We applied time-domain averaging of EEG single trials in order to extract 3 components of MRP (BP(-600 to -500); MP(-100 to 0); MMP) preceding and accompanying behavioral responses. RESULTS: Overall, as in our previous research the effect of force per se was not reflected in the EEG components. However, we did find an interaction between finger and force level in both the Bereitshaftspotential (BP) and motor potential (MP) components of the movement-related potentials. While the middle, ring and little finger produced no differences in EEG components at any of the 3 force levels, the index finger did. We further correlated the force trajectory and the EEG time series with the highest correlations found in the lowest force level with the index finger. As the force level was increased, the correlation was significantly reduced. CONCLUSIONS: Overall, the whole complex of MRP components and evolution of EEG time series during multi-finger isometric force production tasks reflect a combination of factors including the primary end-effector performing the task and interaction of end-effector and the amount of nominal force.

Adult↗
PubMed2002

Modulated cortical control of individual fingers in experienced musicians: an EEG study. Electroencephalographic study.

OBJECTIVE: The present research was designed to address the nature of interdependency between fingers during force production tasks in subjects with varying experience in performing independent finger manipulation. Specifically, behavioral and electroencephalographic (EEG) measures associated with controllability of the most enslaved (ring) and the least enslaved (index) fingers was examined in musicians and non-musicians. METHODS: Six piano players and 6 age-matched control subjects performed a series of isometric force production tasks with the index and ring fingers. Subjects produced 3 different force levels with either their index or ring fingers. We measured the isometric force output produced by all 4 fingers (index, ring, middle and little), including both ramp and static phases of force production. We applied time-domain averaging of EEG single trials in order to extract 4 components of the movement-related cortical potentials (MRCP) preceding and accompanying force responses. RESULTS: Three behavioral findings were observed. First, musicians were more accurate than non-musicians at reaching the desired force level. Second, musicians showed less enslaving as compared to non-musicians. And third, the amount of enslaving increased with the increment of nominal force levels regardless of whether the index or ring finger was used as the master finger. In terms of EEG measures, we found differences between tasks performed with the index and ring fingers in non-musicians. For musicians, we found larger MRCP amplitudes at most electrode sites for the ring finger. CONCLUSIONS: Our data extends previous enslaving research and suggest an important role for previous experience in terms of the independent use of the fingers. Given that a variety of previous work has shown finger independence to be reflected in cortical representation in the brain and our findings of MRCP amplitude associated with greater independence of fingers in musicians, this suggests that what has been considered to be stable constraints in terms of finger movements can be modulated by experience. SIGNIFICANCE: This work supports the idea that experience is associated with changes in behavioral and EEG correlates of task performance and may have clinical implications in disorders such as stroke or focal hand dystonia. Practice-related procedures offer useful approaches to rehabilitation strategies.

Adult↗
PubMed2000

Neurophysiological and behavioral indices of time pressure effects on visuomotor task performance.

Using a video game format, this study examined the effects of time pressure (TP) on behavioral and electrocortical indices. The behavioral results were consistent with previous time pressure research in that TP reduced time to perform a task and increases behavioral errors. In addition, electroencephalogram (EEG) measures showed distinctive patterns associated with TP in the theta, mu, and gamma bands along the midline. Site specific changes in the success vs. failure trials were also seen in midline theta at Fz, gamma at Fz, and mu at Cz. Right parietal alpha also differentiated TP and success vs. failure trials. In specific TP (1) increased frontal midline theta activity and (2) increased gamma at midline (frontal, central, and partietal) and in right frontal areas. The results of these findings are discussed in terms of the formation of specific neurocognitive strategies as evidenced by the topographic distribution of task-related modulation of the EEG within certain frequency bands. It is suggested that the effect of TP on visuomotor performance is mediated by adopting either task-relevant or task-irrelevant neurocognitive strategies as evidenced by successful or failed trials, respectively. Whether these strategies are formulated prior to performance or appear spontaneously during task performance remains unclear and is awaiting further experimentation.

Adult↗
PubMed2000

Human oscillatory brain activity within gamma band (30-50 Hz) induced by visual recognition of non-stable postures.

Our principal finding from this study is that there were changes at the level of brain electrical activity (EEG) during cognitive tasks while subjects were instructed to visually recognize non-stable postures of a computer animated human body model. In particular, there was clear enhancement of the amplitude within the gamma band (30-50 Hz) activity associated with visual recognition of non-stable postures at fronto-central and parietal areas in all subjects. The Morlet's wavelet transform was applied to examine the change of time-frequency (TF) energy within a range of 1-70 Hz frequencies range as a function of experimental tasks. There was a high energy burst within the 35-45 Hz TF cluster at fronto-central and parietal areas when subjects visually recognized non-stable postures. Experimental evidences were provided demonstrating that EEG activity recorded during visual recognition of non-stable postures was related to specific judgement of postural instability. In a series of control experiments, additional evidences were provided to justify the specific sensitivity of EEG 40-Hz activity to the act of visual recognition of postural instability. The contamination of muscle activity in the reported EEG results during perceptual tasks was also ruled out. Our findings are consistent with the notion of existence of specialized neural detectors (predictors) for specific postures and goal-oriented behavior. However, the functional significance and precise cognitive and neurophysiological mechanisms predicting the existence of these detectors remain to be explored.

Adolescent↗
PubMed1995

Neonatal sucking behaviors.

Neonatal sucking responses or behaviors have been of great interest to researchers and clinicians since the early 1800s. Since 1960, there has been a resurgence of interest in the objective study of sucking behaviors in both the psychological and medical literature. The studies have examined both nutritive and non-nutritive sucking measurements. Sucking behaviors have been studied to understand the development of the feeding mechanism as well as to track neurobehavioral development. The relationship between sucking behaviors and behavioral organization of the newborn are considered, along with a historical perspective of sucking measurements, relevant literature on nutritive sucking, physiologic correlates, differences in breast and bottle feeding patterns, non-nutritive sucking, and factors that modify sucking organization. Implications for nursing practice will be discussed.

Bottle Feeding↗
PubMed1994

Diet affects hepatocyte membrane composition, fluidity, and taurocholate transport in suckling rats.

We postulated that age-related changes in hepatocyte basolateral membrane lipid composition might contribute to the diminished Na(+)-dependent taurocholate transport noted in suckling animals. Basolateral membrane vesicles (BLMVs) were prepared from suckling rats (day 11) whose dams were fed diets predominant in lard (LBLMV), corn oil (COBLMV), or fish oil (FOBLMV). Fatty acid compositions of milk and BLMV differed significantly among the groups. Membrane cholesterol was higher in FOBLMV compared with the COBLMV and LBLMV groups; lipid phosphorus and the relative distribution of phospholipid classes were similar. Fluorescence anisotropy (1,6-diphenyl-1,3,5-hexatriene) was higher in FOBLMV (0.230) than in LBLMV (0.222) or COBLMV (0.217). Excited state lifetimes were similar in all groups. Na(+)-dependent taurocholate transport was increased at 5 and 20 s in LBLMV and COBLMV compared with FOBLMV. In vitro alteration of membrane cholesterol-fluidity did not alter taurocholate transport. In conclusion, although affected by alterations in diet, simple changes in membrane fluidity-cholesterol content do not affect Na(+)-dependent taurocholate transport.

Animals↗
PubMed1992

Developmental changes in hepatic basolateral membrane lipid composition and fluidity.

Membrane fluidity and lipid composition influence the activity of a variety of membrane proteins. Decreased rates of hepatic ion clearance are associated with the neonatal period. We postulated that hepatic basolateral membranes derived from suckling animals might be less fluid than those from adult animals. Basolateral membrane vesicles were prepared from the livers of 1-week-old (SBLMV) and adult (ABLMV) rats by a Percoll gradient method. Na+/K(+)-ATPase activities were similar in the two groups. Double bond index, cholesterol and cholesterol/phosphorus ratios were significantly higher in SBLMV compared with ABLMV, while lipid phosphorus and relative percentages of phospholipid subclasses did not differ. Fluorescence anisotropy measured using diphenylhexatriene as well as 2-(9-anthroyloxy)stearate was significantly greater in SBLMV compared with ABLMV, while measurements made with 12-(9-anthroyloxy)stearate were similar in both age groups. Mean excited state lifetimes, lifetime distributions, and rotational correlation times were similar in both groups. These data suggest that hepatic basolateral membranes derived from suckling rats are less fluid than those from adult animals and further suggest that this difference may be due to increased cholesterol in hepatic basolateral membranes derived from suckling animals.

Animals↗
PubMed1988

Nephrotoxicity in leukemic patients receiving empirical amphotericin B and aminoglycosides.

Twelve leukemic patients (19%) receiving amphotericin B and aminoglycosides had nephrotoxicity (creatinine value greater than 2.0 mg/dl). Patients with nephrotoxicity tended to be older than patients without nephrotoxicity; gender and total amphotericin B dose were not related to nephrotoxicity. Sodium administration has previously been shown to reverse amphotericin B nephrotoxicity. In this series, among patients receiving ticarcillin at greater than or equal to 18 gm/day (93.6 mEq of sodium per day) the incidence of nephrotoxicity was significantly decreased (1/30, or 3.3%). A multivariate analysis showed that this protective effect of ticarcillin was not dependent on the fact that patients receiving ticarcillin were less likely to receive vancomycin. There were insufficient patients receiving sodium in the absence of ticarcillin to study the effect of sodium alone. However, our observations are consistent with the hypothesis that sodium can prevent renal dysfunction in this clinical situation.

Adult↗
PubMed1987

Malignant lymphomas of follicular center cell origin in man. VI. Large cleaved cell lymphoma.

Between 1970 and 1986 61 patients with large cleaved cell lymphoma (LCCL) were observed and treated. Median age was 56, and there were slightly more women than men (ratio, 1.4:1). Forty-four cases (72%) had both a nodular and diffuse pattern; eight cases were nodular; nine cases were diffuse. Forty-three patients (70%) had Stage III or IV disease; four patients were Stage I (7%); 14 were Stage II (23%). Bone marrow was involved in 15 of 56 evaluable patients (27%). The median survival was 57 months. It was significantly shorter in symptomatic patients (median, 20 months) than in asymptomatic patients (median, 66 months; P = 0.002). Survival time was also shorter in Stage III and IV patients (median, 46 months) compared with Stage I and II patients (median, 100+ months; P = 0.032). Survival was independent of the disease pattern, marrow involvement, age, gender, and surface immunoglobulin heavy or light chain. Among Stage III and IV patients, survival was the same in patients who received therapy initially and in those who were treated expectantly. Among 10 advanced-stage patients who did not initially receive therapy, the median time to beginning therapy was 17 months; five patients received no therapy for 40 to 96 months. Among 14 advanced-stage patients receiving therapy regarded as curative in aggressive lymphoma, 50% experienced a complete remission (CR). However, unlike other aggressive large cell lymphomas, long-term, relapse-free survival was observed in only 9% of patients as the majority of CRs were associated with relapse rather than cure. Despite the fact that it is a large cell lymphoma, LCCL is best regarded as an indolent lymphoma.

Adult↗
PubMedDate not supplied

Should cases with a 'known' cause of their disease be excluded from study? (commentary).

Assigning a cause to an individual event is a natural impulse. This impulse sometimes finds its way into epidemiologic research, if researchers assign a specific cause to some cases of a disease under study. In epidemiologic studies of drug effects, assigning a cause to specific cases is often used as a reason to exclude these cases from cohort or case-control studies, because the disease in these cases is thought to be the result of a 'known cause'. These exclusions are invalid. It is always valid, however, to exclude all subjects with 'known' causes from a study, cases from the numerator and the people or person-time at risk from the denominator (or from the control series in a case-control study). If the exclusions from the denominator would be negligibly small or the relative number of excluded cases with 'known' causes is small, then the exclusion of just the cases with 'known' causes will introduce little bias.

Arrhythmias, Cardiac↗