Prolonged studies of perfluorocarbon associated gas exchange and of the resumption of conventional mechanical ventilation

We applied functional magnetic resonance imaging (FMRI) to map the somatotopic organization of the primary motor cortex using voluntary movements of the hand, arm, and foot. Eight right-handed healthy subjects performed self-paced, repetitive, flexion/extension movements of the limbs while undergoing echo-planar imaging. Four subjects performed movements of the right fingers and toes, while the remaining subjects performed movements of the right fingers and elbow joint. There was statistically significant functional activity in the left primary motor cortex in all subjects. The pattern of functional activity followed a topographic representation: finger movements resulted in signal intensity changes over the convexity of the left motor cortex, whereas toe movements produced changes either at the interhemispheric fissure or on the dorsolateral surface adjacent to the interhemispheric fissure. Elbow movements overlapped the more medial signal intensity changes observed with finger movements. Functionally active regions were confined to the cortical ribbon and followed the gyral anatomy closely. These findings indicate that FMRI is capable of generating somatotopic maps of the primary motor cortex in individual subjects.     

A case of porencephaly with mirror movements: pathophysiological investigation by using long-latency long-loop reflex and dipole tracing method

We report a 42-year-old left-handed woman with congenital right hemiparesis and bilateral mirror movements in the hands. She had a porencephaly of the left hemisphere and the brain MRI demonstrated cortical and subcortical defect of the left hemisphere from Brodmann's area 6 to 40 including the left motor cortex. By electrical stimulation of the left median nerve at the wrist, N20 of the somatosensory evoked potential was recorded in the right postcentral gyrus by using the dipole tracing method. Long-loop reflexes from the bilateral thenar muscles were recorded and their latencies were almost the same. The stimulation of the right median nerve did not evoke N20, nor long-loop reflex. These electrophysiological findings suggest that the reorganization of the motor system made the right motor cortex to innervate bilateral hands, and caused bilateral mirror movements. In other words, the mirror movements managed to relieve the paralysis of the right hand though the damage of the left motor cortex was present. In the previous literature we are able to find hypotheses regarding the mechanism of mirror movements in congenital hemiparesis. Here we discussed about the reorganization of the motor system in the damaged brain.     

Expectancy of Pain Is Influenced by Motor Preparation: A High-Resolution EEG Study of Cortical Alpha Rhythms.

This high-resolution electroencephalographic (EEG) study on alpha event-related desynchronization (ERD) evaluated whether anticipatory activity precedes a sensorimotor interaction induced by concomitant painful stimuli and sensorimotor demand. An omitted-stimulus paradigm induced the expectancy of the painful stimulation at the left hand. In the experimental condition, the painful stimulation was associated with a visual go/no-go task triggering right-hand movements. Two control conditions manipulated the painful sensorimotor interaction variable. Compared with the control conditions, the expectancy of the painful sensorimotor interaction increased the high-band alpha EEG oscillations over the right primary sensorimotor cortex contralateral to the nociceptive stimuli and, to a lesser extent, over the centroparietal midline. These findings suggest that concomitant painful stimuli and simple sensorimotor go/no-go demands affect anticipatory activity as revealed by alpha ERD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Smad6 inhibits BMP/Smad1 signaling by specifically competing with the Smad4 tumor suppressor

Twenty-seven studies were carried out on the recognition of the shapes of geometrical figures of different sizes by healthy adults, on the recognition of the direction of movement of a light spot within the field of vision, and of visual illusions produced by rhythmic visual stimulation. Tachystoscopic presentation of figures and the onset of movement were synchronized with different phases of the EEG alpha-rhythm in the occipital region. In controls, stimuli were presented without a shift in the alpha-rhythm. Recognition improved significantly when small figures were presented at relatively late phases of the alpha-wave and when large figures (up to 9 degrees) were presented at relatively early phases. Recognition of the side and direction of apparent movement (in the left or right halves of the visual field and centrifugal or centripetal) depended on the phase of the alpha-wave only for nonuniform (accelerating or decelerating, depending on direction) movement, allowing for the cortical magnification factor. Centrifugal movements in experiments were recognized better than in controls, while centripetal movements were recognized worse, and elicited a relatively long-latency movement response. Diffuse rhythmic light stimulation at the alpha-rhythm frequency produced the illusory percept of a ring or circle in 11 of 12 subjects. The optimal stimulation frequency for this was tightly connected with the dominant alpha-rhythm frequency, with a correlation coefficient of 0.86. The link between these effects and the propagation of the wave process through the visual cortex, as reflected by the EEG alpha-rhythm, is discussed. The data support the hypothesis of Pitts and McCulloch [29], which proposes scanning of the visual cortex by a wave process operating at the frequency of the alpha-rhythm, which reads information from the visual cortex.     

Evidence for motor simulation in imagined locomotion.

A series of experiments examined the role of the motor system in imagined movement, finding a strong relationship between imagined walking performance and the biomechanical information available during actual walking. Experiments 1 through 4 established the finding that real and imagined locomotion differ in absolute walking time. We then tested whether executed actions could provide a basis for imagined walking rate using 2 approaches. Experiments 5 and 6 used a perceptual-motor recalibration paradigm, finding that after physically walking in a treadmill virtual reality environment, actors recalibrated the time to imagine walking to a previously viewed target. This finding mirrors previous perceptual-motor recalibration work measuring actual walking to previously viewed targets. Experiments 7 and 8 used a dual-task paradigm in which actions performed concurrently with imagined walking increased the similarity between real and imagined walking time, but only when they were biomechanically consistent with the act of walking. The striking influence of biomechanical information on imagined locomotion provides evidence for shared motor systems in imagined and executed movements and is also directly relevant to the mechanisms involved in egocentric spatial updating of environmental layout. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Imagined spatial transformation of one's body.

This study examined two related phenomena: (a) the judgment of whether a human body part belongs to the left or right half of the body and (b) the imagined spatial transformation of one's body. In three experiments, observers made left–right judgments of a part of a body whose orientation differed from their own by a rotation about one of 13 axes. To do so, they imagined themselves passing to the orientation of the stimulus. Time for (a) left–right judgments and (b) accompanying imagined spatial transformations depended on the extent of the orientation difference (OD) between the observer and stimulus. More important, time for phenomena (a) and (b) depended strongly, and in the same way, on the direction of OD. Further results showed that the rate of imagined spatial transformations can vary strongly for different axes and directions of rotation about an axis. These and other results (e.g., Parsons, 1987a) suggest that temporal and kinematic properties of imagined spatial transformations are more object-specific than could be previously assumed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional magnetic resonance imaging of motor cortex: hemispheric asymmetry and handedness

A hemispheric asymmetry in the functional activation of the human motor cortex during contralateral (C) and ipsilateral (I) finger movements, especially in right-handed subjects, was documented with nuclear magnetic resonance imaging at high field strength (4 tesla). Whereas the right motor cortex was activated mostly during contralateral finger movements in both right-handed (C/I mean area of activation = 36.8) and left-handed (C/I = 29.9) subjects, the left motor cortex was activated substantially during ipsilateral movements in left-handed subjects (C/I = 5.4) and even more so in right-handed subjects (C/I = 1.3).     

Human vestibuloocular reflex and its interactions with vision and fixation distance during linear and angular head movement

Human vestibuloocular reflex and its interactions with vision and fixation distance during linear and angular head movement. J. Neurophysiol. 80: 2391-2404, 1998. The vestibuloocular reflex (VOR) maintains visual image stability by generating eye movements that compensate for both angular (AVOR) and linear (LVOR) head movements, typically in concert with visual following mechanisms. The VORs are generally modulated by the "context" in which head movements are made. Three contextual influences on VOR performance were studied during passive head translations and rotations over a range of frequencies (0.5-4 Hz) that emphasized shifting dynamics in the VORs and visual following, primarily smooth pursuit. First, the dynamic characteristics of head movements themselves ("stimulus context") influence the VORs. Both the AVOR and LVOR operate with high-pass characteristics relative to a head velocity input, although the cutoff frequency of the AVOR (<0.1 Hz) is far below that of the LVOR ( approximately 1 Hz), and both perform well at high frequencies that exceed, but complement, the capabilities of smooth pursuit. Second, the LVOR and AVOR are modulated by fixation distance, implemented with a signal related to binocular vergence angle ("fixation context"). The effect was quantified by analyzing the response during each trial as a linear relationship between LVOR sensitivity (in deg/cm), or AVOR gain, and vergence (in m-1) to yield a slope (vergence influence) and an intercept (response at 0 vergence). Fixation distance (vergence) was modulated by presenting targets at different distances. The response slope rises with increasing frequency, but much more so for the LVOR than the AVOR, and reflects a positive relationship for all but the lowest stimulus frequencies in the AVOR. A third influence is the context of real and imagined targets on the VORs ("visual context"). This was studied in two ways-when targets were either earth-fixed to allow visual enhancement of the VOR or head-fixed to permit visual suppression. The VORs were assessed by extinguishing targets for brief periods while subjects continued to "fixate" them in darkness. The influences of real and imagined targets were most robust at lower frequencies, declining as stimulus frequency increased. The effects were nearly gone at 4 Hz. These properties were equivalent for the LVOR and AVOR and imply that the influences of real and imagined targets on the VORs generally follow low-pass and pursuit-like dynamics. The influence of imagined targets accounts for roughly one-third of the influence of real targets on the VORs at 0.5 Hz.     

The current state of health care in the former Soviet Union: implications for health care policy and reform

OBJECTIVE: To study planning of movement in Parkinson's disease. METHODS: The spatiotemporal pattern of movement related desynchronisation (MRD) preceding a self paced voluntary wrist flexion was compared between two groups of 10 untreated right and left hemiparkinsonian patients receiving no treatment and 10 control subjects. The MRD was computed in the 9 to 11 Hz frequency band from 11 source derivations covering the frontocentral, central, and parietocentral areas, during two successive left and right experimental conditions. RESULTS: In the two patient groups the desynchronisation appeared over the primary sensorimotor area contralateral to the affected side with a shorter latency (750 ms before movement onset for the right hemiparkinsonian group and 875 ms for the left hemiparkinsonian group) than in the control group (1750 ms), only when the movements were performed with the akinetic hand. For the non-affected hand, the same latency as in the control group was noted (1750 ms). CONCLUSION: The delay of appearance of MRD in Parkinson's disease confirmed that the programming of movement is affected, thus partially explaining akinesia.     

Dividing attention between the hands and the head: Performance trade-offs between rapid finger tapping and verbal memory.

Tested a multiple resources approach to time-sharing performance which assumes that each cerebral hemisphere controls its own set of processing resources that it cannot share with the other hemisphere. Right-handed men performed a verbal memory task while concurrently tapping the index finger of either hand as rapidly as possible. Task priority was manipulated with a payoff scheme. Ss remembered more on the verbal task when concurrently tapping with their left hands than when tapping with their right hands, and their memory performance was much better when the memory task was emphasized than when the tapping task was emphasized, regardless of hand. For the tapping task, decrements from baseline tapping rates and trade-offs between tasks were equal for both hands when Ss were reading the to-be-remembered words aloud. In contrast, during the retention interval, decrements were larger for the right hand than the left, and there were no task trade-offs. On right-hand trials, both tasks required exclusively left-hemisphere resources, whereas on left-hand trials, right-hemisphere resources were required to execute the tapping movements per se, but left-hemisphere resources were necessary to coordinate those movements with the movements required for overt speech. The data underscore the importance of manipulating task priority to obtain an accurate picture of a task's resource requirements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interference effects in bimanual coordination are independent of movement type.

Simultaneously executed limb movements interfere with each other. Whereas the interference between discrete movements is examined mostly from a cognitive perspective, that between rhythmic movements is studied mainly from a dynamical systems perspective. As the tools and concepts developed by both communities are limited in their applicability to the other domain, it remains unclear if a common cause underlies motor interference in both domains. We investigated the interference between simultaneously executed discrete and rhythmic wrist movements. The discrete movements' reaction time and movement time decreased with increasing rhythmic movement frequency. The discrete movements accelerated or decelerated the rhythmic movements in a manner that depended on movement frequency and the discrete movement's initiation phase. The acceleration/deceleration profile was bimodal at low frequencies and unimodal at high frequencies, mimicking the hallmark feature of rhythmic-rhythmic coordination, thus suggesting that interference between movements may be invariant across different movement types. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decreased heterogeneity of capillary plasma flow in the rat whisker-barrel cortex during functional hyperemia

The pattern of capillary plasma perfusion was investigated in the rat brain during functional activation. Functional hyperemia was induced in the left whisker-barrel cortex by deflection of the right mystacial vibrissae for 2 min at frequencies of 1-7 Hz. Rats were decapitated under anesthesia 3-4 s after i.v. bolus injection of Evans blue dye. The steep increase of the arterial dye concentration ensures that divergent capillary plasma transit times result in unequal intracapillary dye concentrations. Plasma perfusion heterogeneity was determined from the coefficient of variation (CV) of Evans blue concentrations measured in numerous single capillaries of the whisker-barrel cortex. Functional hyperemia was quantified from measurements of CBF using the [14C]-iodoantipyrine technique in a second experimental group. CBF in the left whisker-barrel cortex increased with the stimulation frequency and was maximal at 5 Hz compared to the right side. Conversely, plasma perfusion heterogeneity decreased with stimulation frequency in a reciprocal way, being minimal at 5 Hz. Results indicate a decrease in the microcirculatory flow heterogeneity during functional hyperemia in the brain.     

Spectral power and coherence analysis of sleep EEG in AIDS patients: decrease in interhemispheric coherence

Fifteen patients aged between 26 and 55 years with the acquired immunodeficiency syndrome (AIDS) and various cerebral manifestations of the disease underwent an all-night sleep electroencephalogram (EEG) registration. The recordings of 15 age-matched volunteers were examined as controls. Sleep stages were determined visually and the following spectral analysis was based on corresponding artifact-free 40-second periods. The sampling rate was 64 second-1, the spectral resolution was 0.25 Hz and the frequency ranged from 0.25-24 Hz. The power density spectra of eight EEG derivations (left and right frontopolar, frontal, central and occipital; reference montage to the ipsilateral Cb electrodes) and the coherence spectra of interhemispheric (interfrontal, interoccipital) and intrahemispheric (frontooccipital, left and right) channel pairs were computed. The power density of the patients in the 11.5-13-Hz frequency range of nonrapid eye movement (NREM) sleep was considerably lower than that of the controls (p < 0.05 and p < 0.01 at left and right frontal derivations, two-tailed Mann-Whitney U test). The power density of rapid eye movement (REM) sleep showed no consistent differences between the two groups. The interfrontal coherence of the whole frequency range below 12 Hz was markedly lower in the patient group. This applied to NREM sleep and also to REM sleep (p < 0.01 and p < 0.001 for different frequency bands between 1 and 12 Hz in NREM and REM sleep). Possible relations to clinical features are discussed.     

Handedness and asymmetry of hand representation in human motor cortex

The cortical representation of five simple hand and finger movements in the human motor cortex was determined in left- and right-handed people with whole-head magnetoencephalography. Different movements were found to be represented by spatially segregated dipolar sources in primary motor cortex. The spatial arrangement of neuronal sources for digit and wrist movements was nonsomatotopic and varied greatly between subjects. As an estimator of hand area size in primary motor cortex, we determined the smallest cuboid volume enclosing the five dipole sources within the left and right hemisphere of each subject. Interhemispheric comparison revealed a significant increase of this volume in primary motor cortex opposite to the preferred hand. This asymmetry was due to a greater spatial segregation of neuronal dipole generators subserving different hand and finger actions in the dominant hemisphere. Mean Euclidean distances between dipole sources for different movements were 10.7 +/- 3.5 mm in the dominant and 9.4 +/- 3.5 mm in the nondominant hemisphere (mean +/- SD; P = 0. 01, two-tailed t-test). The expansion of hand representation in primary motor cortex could not simply be attributed to a greater number of pyramidal cells devoted to each particular movement as inferred from current source amplitudes. The degree of hemispheric asymmetry of hand area size in the primary motor cortex was correlated highly with the asymmetry of hand performance in a standardized handedness test (r = -0.76, P < 0.01). These results demonstrate for the first time a biological correlate of handedness in human motor cortex. The expansion of hand motor cortex in the dominant hemisphere may provide extra space for the cortical encoding of a greater motor skill repertoire of the preferred hand.     

Ser-311-Cys polymorphism of the dopamine D2 receptor gene and schizophrenia--an analysis of schizophrenic patients in Fukuoka

Functional brain imaging studies have indicated that several cortical and subcortical areas active during actual motor performance are also active during imagination or mental rehearsal of movements. Recent evidence shows that the primary motor cortex may also be involved in motor imagery. Using whole-scalp magnetoencephalography, we monitored spontaneous and evoked activity of the somatomotor cortex after right median nerve stimuli in seven healthy right-handed subjects while they kinesthetically imagined or actually executed continuous finger movements. Manipulatory finger movements abolished the poststimulus 20-Hz activity of the motor cortex and markedly affected the somatosensory evoked response. Imagination of manipulatory finger movements attenuated the 20-Hz activity by 27% with respect to the rest level but had no effect on the somatosensory response. Slight constant stretching of the fingers suppressed the 20-Hz activity less than motor imagery. The smallest possible, kinesthetically just perceivable finger movements resulted in slightly stronger attenuation of 20-Hz activity than motor imagery did. The effects were observed in both hemispheres but predominantly contralateral to the performing hand. The attempt to execute manipulatory finger movements under experimentally induced ischemia causing paralysis of the hand also strongly suppressed 20-Hz activity but did not affect the somatosensory evoked response. The results indicate that the primary motor cortex is involved in motor imagery. Both imaginative and executive motor tasks appear to utilize the cortical circuitry generating the somatomotor 20-Hz signal.     

Distributed neural systems underlying the timing of movements

Timing is essential to the execution of skilled movements, yet our knowledge of the neural systems underlying timekeeping operations is limited. Using whole-brain functional magnetic resonance imaging, subjects were imaged while tapping with their right index finger in synchrony with tones that were separated by constant intervals [Synchronization (S)], followed by tapping without the benefit of an auditory cue [Continuation (C)]. Two control conditions followed in which subjects listened to tones and then made pitch discriminations (D). Both the S and the C conditions produced equivalent activation within the left sensorimotor cortex, the right cerebellum (dorsal dentate nucleus), and the right superior temporal gyrus (STG). Only the C condition produced activation of a medial premotor system, including the caudal supplementary motor area (SMA), the left putamen, and the left ventrolateral thalamus. The C condition also activated a region within the right inferior frontal gyrus (IFG), which is functionally interconnected with auditory cortex. Both control conditions produced bilateral activation of the STG, and the D condition also activated the rostral SMA. These results suggest that the internal generation of precisely timed movements is dependent on three interrelated neural systems, one that is involved in explicit timing (putamen, ventrolateral thalamus, SMA), one that mediates auditory sensory memory (IFG, STG), and another that is involved in sensorimotor processing (dorsal dentate nucleus, sensorimotor cortex).     

Alien hand syndrome: influence of neglect on the clinical presentation of frontal and callosal variants

Three patients with mesial frontal and extensive callosal lesions due to anterior cerebral artery infarction manifested an alien hand syndrome (AHS) with varied features. Patient 1 with left hemispheric lesion showed right hand's impulsive reaching and grasping and left hand's antagonistic movements to the right (intermanual conflict; IMC). Patients 2 and 3 with right hemispheric lesion manifested a left hemihypokinesia which was thought to have suppressed the frequency and amplitude or even the occurrence of left hand's reaching and grasping. IMC and other left hand's non-antagonistic, irrelevant movements to the right remained. Because the term "IMC" is often misused and not strictly defined, its association with right hand's reaching and grasping is quite uncommon, its significance as a sign of callosal disconnection is not well validated, and because left hand's reaching and grasping tend to be suppressed by motor neglect, a trend may then develop for the right hand to be the sole focus of pathological behaviour in patients with the so-called frontal AHS (Feinberg, Schindler, Flanagan et al., 1992).     

Neural activity during attention shifts between object features

To investigate the neural mechanisms involved in shifting attention we used positron emission tomography to examine regional cerebral blood flow (rCBF) during a task that demands shifting attention between color and shape. Significant activation was observed in the right dorsal prefrontal cortex and parieto-occipital cortex at all frequencies of attention shifts. The frequency of shifts between categories correlated significantly with rCBF in the rostral part of the supplementary motor area and the left precuneus, whereas the number of successive correct responses correlated with rCBF in the orbitofrontal cortex and the caudate nucleus. This study suggests that several prefrontal regions may participate in the processes of shifting attention in different ways.     

Sex differences in EEG in adult gonadectomized rats before and after hormonal treatment

EEG activity was recorded from the left and right parietal cortex in adult male and female Wistar rats that were gonadectomized (GNX) after puberty during 2 days without and 3 days with hormonal treatment (either testosterone propionate, 5 alpha-DHT or vehicle in males and progesterone, estradiol benzoate or vehicle in females). In contrast to EEG characteristics reported for intact rats, GNX abolished right over left parietal activation in both sexes and, sex differences in EEG interhemispheric correlation and in theta and delta relative power in the right parietal; additionally GNX males showed higher absolute power than females. Hormonal treatment reestablished interparietal asymmetry in both sexes and a lack of sex differences in absolute power, however, it was not enough to reestablish sex differences in delta and theta proportion in the right parietal nor in interhemispheric correlation. Differential effects were obtained with testosterone propionate and 5 alpha-DHT in males suggesting that activational effects of testosterone on EEG are probably exerted through testosterone or its aromatized metabolites. The results of our study indicate that the activational effects of gonadal steroids after puberty are necessary for maintaining sex differences in the EEG of the adult rat.     

The perception of flicker on raster-scanned displays

Experiments have verified the observations of Corbett and White that people are more sensitive to flicker on raster-scanned displays (e.g., television and visual display terminals) if the field scan direction is changed from the conventional top-to-bottom direction to bottom to top, left to right, or right to left. When measured by means of the flicker fusion frequency (FFF), this effect is present only when normal eye movements are permitted. With fixation, the FFF is similar for all scan directions. The effect is demonstrated by the different frequencies at which a directional component is detected in the flicker (which we have called the rolling flicker threshold frequency, or RFTF); the RFTF is lower for top-to-bottom scanning. The effect does not appear to be associated with any asymmetry in eye movements or with eccentricity of the retinal image. The hypothesis that this difference is a consequence of adaptation to televisions and VDTs is supported by the observation that the effect's magnitude correlates with daily exposure time to televisions and VDTs and by a pilot study showing that the effect is reduced when one views a television scanned from bottom to top for 1 h.