Article
The beat goes on: rhythmic modulation of cortical potentials by imagined tapping.
Department of Psychology, University of Pennsylvania, Philadelphia, PA 19104, USA.
Journal of Experimental Psychology Human Perception & Performance (impact factor:
3.06).
09/2006;
32(4):986-1005.
DOI:10.1037/0096-1523.32.4.986
pp.986-1005
Source: PubMed
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Article: Effects of spatial selective attention on the steady-state visual evoked potential in the 20-28 Hz range.
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ABSTRACT: Steady-state visual evoked potentials (SSVEPs) were recorded from the scalp of subjects who attended to a flickering LED display in one visual field while ignoring a similar display (flickering at a different frequency) in the opposite visual field. The flicker frequencies were 20.8 Hz in the left-field display and 27.8 Hz in the right-field display. The SSVEP to the flicker in either field was enhanced in amplitude when attention was directed to its location. The scalp distribution of this SSVEP enhancement was narrowly focused over the posterior scalp contralateral to the visual field of stimulation. A source analysis using Variable Resolution Electromagnetic Tomography (VARETA) indicated that the source current densities for the SSVEP attention effect had a focal origin in the contralateral parieto-occipital cortex.Cognitive Brain Research 05/1998; 6(4):249-61. · 3.77 Impact Factor -
Article: Dynamic changes in corticospinal excitability during motor imagery.
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ABSTRACT: We investigated temporal changes in the amplitudes of motor-evoked potentials (MEPs) induced by transcranial magnetic stimulation over the left motor cortex during motor imagery. Nine subjects were instructed to imagine repetitive wrist flexion and extension movements at 1 Hz, in which the flexion timing was cued by a tone signal. Electromyographs (EMGs) were recorded from the first dorsal interosseous, flexor carpi radialis and extensor carpi radialis muscles of the right hand, and magnetic stimulation was delivered at 0, 250, 500 and 750 ms after the auditory cue. On average, the evoked EMG responses were larger in the flexor muscle during the phase of imagined flexion than during extension, whilst the opposite was true for the extensor muscle. There were no consistent changes in the amplitudes of MEPs in the intrinsic hand muscle (first dorsal interosseous). The EMG remained relaxed in all muscles and did not show any significant temporal changes during the test. The H-reflex in the flexor muscle was obtained in four subjects. There was no change in its amplitude during motor imagery. These observations lead us to suggest that motor imagery can have dynamic effects on the excitability of motor cortex similar to those seen during actual motor performance.Experimental Brain Research 04/1999; 125(1):75-81. · 2.39 Impact Factor -
Article: Prediction of Mortality Risk by Different Methods of Indexation for Left Ventricular Mass
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ABSTRACT: Objectives. We sought to compare the predictive value of echocardiographically determined left ventricular hypertrophy on death from all causes and cardiac mortality using various methods of indexation for left ventricular mass.Background. Considerable controversy exists regarding the optimal method for indexing left ventricular mass to body size in the clinical setting.Methods. The study included 988 consecutive patients who had both coronary angiograms and echocardiographic examinations in an inner-city public hospital in Chicago, Illinois. Patients were followed up for a mean of 7 years (range 2 to 11).Results. Various left ventricular mass indexes (e.g., mass indexed for height, height2, height2.13, height2.7, body surface area and body surface area1.5 were highly correlated (r = 0.90 to 0.99). Used as a continuous measure, an increase in any left ventricular mass index was associated with similar risk of death from all causes and cardiac diseases. Although left ventricular hypertrophy assessed by mass indexed for body surface area using the published conventional partition values provided somewhat better prediction, the adjusted relative risk was in general not significantly different from hypertrophy based on other indexes. Patients with left ventricular hypertrophy defined concordantly by indexes based on both body surface area and height (or height2.7) had, by definition, the highest average mass indexes among all groups and experienced as much as a threefold greater risk of death than those without hypertrophy. A small proportion of patients (12%) who were classified into the hypertrophy group by height-based indexes alone, but not by body surface area, had a moderate increase in mass and showed no increase in risk, even though being overweight was extremely prevalent in this group.Conclusions. Because of the high correlation among various body size indexes, left ventricular hypertrophy, defined by different indexes for left ventricular mass, similarly confers increased risk of mortality in patients with or without coronary artery disease.(J Am Coll Cardiol 1997;29:641–7)Journal of the American College of Cardiology 04/1997; · 14.16 Impact Factor
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Keywords
alternation frequency
brief visual stimuli
constant rate
covert actions
frequency analysis
hemispheres
homologous foci
imagined movements
imagined rhythmic movements
imagined taps
neural level
overt
Participants synchronized overt
posterior parietal cortex
prominent power foci
sensorimotor cortex
tag cortical activity
taps
topographic maps
