Effect of optokinetic stimulation on weight-bearing shift in standing and sitting positions in stroke patients.

BACKGROUND: Patients with hemiplegia after stroke tend to bear weight on the non-paretic side and exhibit large postural sway during static standing and walking, which may increase their risk of falls. Improvement of the sitting posture balance in the early phase of rehabilitation by adjusting weight-bearing would minimize the risk of falls as early rehabilitation reportedly improves walking ability and prevents falls in later phases of rehabilitation or at discharge. AIM: This study aimed to evaluate the effect of optokinetic stimulation (OKS) on shift of the weight-bearing (displacement of the center of pressure [CoP]) in patients with hemiplegia who are incapable of independent standing. DESIGN: Quasi-experimental, cross-sectional study. SETTING: Rehabilitation hospital. POPULATION: Patients with hemiplegia in the subacute phase after stroke (N.=37). METHODS: Standing and sitting balance tests were performed during OKS projected onto a screen. For OKS, a pattern of random dots was presented, which continuously moved in horizontal or torsional directions during both static standing and sitting conditions. Postural sway was assessed during standing and sitting by measuring the sway path, sway area, sway velocity, and mean displacement of CoP. The magnitude of the lateral change in CoP as an indicator of the weight-bearing shift was evaluated by subtraction of the mean CoP of the right-left axis component in the stationary condition from the mean CoP sway during OKS. RESULTS: OKS induced a unilateral change of the mean CoP position in patients during both, sitting and static standing, indicating that OKS can shift the weight-bearing in patients after stroke, irrespective of the posture condition. Moreover, the same OKS approach evoked an analogous shift in patients with more severe symptoms, with impairment in independent standing. CONCLUSIONS: OKS could induce a significant shift in weight balance in patients with hemiplegia after stroke who are incapable of independent standing, suggesting that the OKS approach can be applied to a broader spectrum of patients, including those with more severe symptoms. CLINICAL REHABILITATION IMPACT: OKS approach would improve exercise training in the early phase of rehabilitation of patients with hemiplegia after stroke.

The Use of Augmented Reality Technology in Medical Specimen Museum Tours.

Human anatomical specimen museums are commonly used by medical, nursing, and paramedical students. Through dissection and prosection, the specimens housed in these museums allow students to appreciate the complex relationships of organs and structures in more detail than textbooks could provide. However, it may be difficult for students, particularly novices, to identify the various parts of these anatomical structures without additional explanations from a docent or supplemental illustrations. Recently, augmented reality (AR) has been used in many museum exhibits to display virtual objects in videos captured from the real world. This technology can significantly enhance the learning experience. In this study, three AR-based support systems for tours in medical specimen museums were developed, and their usability and effectiveness for learning were examined. The first system was constructed using an AR marker. This system could display virtual label information for specimens by capturing AR markers using a tablet camera. Individual AR markers were required for all specimens, but their presence in and on the prosected specimens could also be obtrusive. The second system was developed to set the specimen image itself as an image marker, as most specimens were displayed in cross section. Visitors could then obtain the label information presented by AR without any markers intruding on the display or anatomical specimens. The third system was comprised of a head-mounted display combined with a natural click interface. The system could provide visitors with an environment for the natural manipulation of virtual objects with future scalability.

Plane-specific Purkinje cell responses to vertical head rotations in the cat cerebellar nodulus and uvula.

We recorded simple spike (SS) and complex spike (CS) firing of Purkinje cell in the cerebellar nodulus and uvula of awake, head-restrained cats during sinusoidal vertical rotation of the head in four stimulus planes (pitch, roll, and two vertical canal planes). Two SS response types (position- and velocity-types) with response phases close to those of head position and velocity, respectively, were recognized. Optimal response planes and directions for SS and CS of each cell were estimated from the response amplitudes in the four stimulus planes by fitting with a sinusoidal function. The principal findings are as follows: (1) two rostrocaudally oriented functional zones of Purkinje cells can be distinguished; (2) the medially located parasagittal band is active during rotation in the pitch plane; (3) the laterally located band is active during rotation in the roll plane. These two zones are the same as previously reported zones in the cerebellar flocculus active during head rotation in the canal planes in the point that both cerebellar sagittal zones are plane-specific functional zones, suggesting that the anatomical sagittal zones serve as functional plane-specific zones at least in the vestibulocerebellum.

Saccade eye movements as a quantitative measure of frontostriatal network in children with ADHD.

BACKGROUND: Evidence of poor inhibition in attention deficit hyperactivity disorder (ADHD) comes primarily from neuropsychological tasks and neuroimaging studies, many of which have revealed structural/functional abnormalities of the frontostriatal network with opposing functions of disinhibition and inhibition. Studies of saccades have therefore contributed to the understanding of the pathophysiological basis of ADHD. OBJECT: To investigate the development of reflexive/voluntary control of saccades in normal children, compare saccade parameters between ADHD and control groups, and clarify dysfunctional nervous systems in ADHD. METHODS: Subjects comprised 50 normal subjects (6-35 years), 19 ADHD patients (6-11 years) and four patients with frontal lesions (13-15 years). Saccade latency and accuracy were computed in all saccade tasks, while percentage of anticipatory errors (PAE) was determined in memory-guided saccade task, and percentage of direction errors (PDE) was determined in antisaccade task. RESULTS: In normal controls, significant correlations were observed between saccade latency, saccade accuracy, error rates and age. Significant differences existed between ADHD and 6- to 8-year-old controls in saccade latency and accuracy. The ADHD group showed significantly higher PAE and PDE rates than controls. Patients with frontal lesions showed significantly higher PAE and PDE. CONCLUSIONS: These results suggest that saccade eye movements do not fully mature until adolescence, and that ADHD patients show dysfunction in "response inhibition", which is modulated by the frontal lobe, particularly the prefrontal cortex, cingulate cortex and basal ganglia.

Voiceless affricate/fricative distinction by frication duration and amplitude rise slope.

Previous psychophysical studies have shown that the perceptual distinction between voiceless fricatives and affricates in consonant-vowel syllables depends primarily on frication duration, whereas amplitude rise slope was suggested as the cue in automatic classification experiments. The effects of both cues on the manner of articulation between /integral of/ and /t integral of/ were investigated. Subjects performed a forced-choice task (/integral of/ or /t integral of) in response to edited waveforms of Japanese fricatives /integral of i/, /integral of u/, and /integral of a/. We found that frication duration, onset slope, and the interaction between duration and onset slope influenced the perceptual distinction. That is, the percent of /integral of/ responses increased with an increase in frication duration (experiments 1-3). The percent of /integral of/ responses also increased with a decrease in slope steepness (experiment 3), and the relative importance between slope portions was not even but weighted at onset (experiments 1 and 2). There was an interaction between the two cues of frication duration and steepness. The relative importance of the slope cue was maximum at a frication duration of 150 ms (experiment 3). It is concluded that the frication duration and amplitude rise slope at frication onset are acoustic cues that discriminate between /integral of/ and /t integral of/, and that the two cues interact with each other.

[Study of saccadic eye movement in children with attention deficit/hyperactivity disorder].

Recent studies have postulated that impairment of behavior inhibition, leading to executive dysfunction in future, is the fundamental pathophysiology of attention deficit/hyperactivity disorder (AD/HD). To evaluate this, we studied two saccadic eye movement tasks: visual- and memory-guided, in 8 children with AD/HD (combined type;mean age, 9.1 years, range 6 approximately 11 years) and 16 healthy children (mean age, 9.2 years, range 6 approximately 12 years). In the memory-guided saccade task, reflexive anticipatory errors were more frequently observed in AD/HD than in controls. The children with AD/HD showed longer response latency in the memory-guided saccade task, and greater coefficient of variation in both the latency and amplitude in both the tasks. These results suggested that saccade tasks, especially the memory-guided task, may be useful in clarifying pathophysiology of AD/HD.

Effect of side-down tilt on optokinetic nystagmus and optokinetic after-nystagmus in cats.

Slow phase velocity (SPV) of optokinetic nystagmus (OKN) and after-nystagmus (OKAN) was examined in the cat in side-down tilts. In the upright position, the axis of SPV (direction of SPV vector) during OKN was always close to the stimulus axis. In side-down positions, yaw stimulation induced OKN with the vector deviating from the stimulus axis toward the pitch-axis, so as to make the SPV rotational plane be shifted toward the earth horizontal plane, while pitch-axis stimulation induced no change in vector direction. This yaw-to-pitch cross-coupling is qualitatively similar to that previously described in primates. SPV vector size during yaw stimulation is greatest when the stimulus axis is oriented vertically, and the vector size is smaller when the stimulus is in the gravity direction than when it is in the anti-gravity direction. The SPV vector for the rapid-rise response showed no clear change with head orientation, indicating that the direct optokinetic pathway has no contribution to the induction of cross-coupling. Cross-coupling was found also during OKAN. The SPV trajectories were fitted well using the velocity storage integrator model. SPV vector change of cat OKN/OKAN in head tilt could be fitted by changing gain elements in the model.

Control of orienting movements: role of multiple tectal projections to the lower brainstem.

In movement neuroscience this past decade, a conceptual approach that puts emphasis on population coding was clearly dominant. The purpose of numerous studies has been to define presumably homogeneous groups of neurons on the basis of the correlation of their discharges with sensory and motor events. The goal of this chapter is to stress the importance of taking into account individual properties of neurons, this being an essential prerequisite for a biologically meaningful definition of neuron populations. Taking as an example the executive limb of the neural network controlling gaze movements, we demonstrate the functional and anatomical diversity of tectal and reticular neurons, which are generally considered as homogeneous populations and used, accordingly, as lumped elements in models. We argue that the extraction of effector-specific signals from the global command of gaze displacement is based not on the interplay between discrete neural modules, but rather on a gradual process of signal specification at all levels of the executive network. An eventual accurate description of this network will require knowledge of the unique combinations of afferent inputs and efferent connections for as many subsets of its constituent neurons as is conceivably possible.

Time course of tonal frequency-response-area of primary auditory cortex neurons in alert cats.

Cells in the A1 auditory cortex of alert animals show various response time-courses during pure-tone stimuli: tonic, phasic-tonic, and phasic. Previously the time course of the spike firing rates was examined at a characteristic frequency (CF) or in a range of frequencies including CF. We investigated time-course of the frequency-response-area (FRA) during pure-tone stimuli in A1 cells of alert cats. The short rise/fall time (0.1-2 ms) and long stimulus duration (0.5 s) was used for investigation of the time course. FRA changed with time drastically in the phasic cells, mildly in the phasic-tonic cells, but not in the tonic cells. The best-response frequency (BF) within FRA was constant throughout the stimulus duration in the tonic and phasic-tonic cells, but was difficult to define in the phasic cells. The phasic firing properties of the phasic cells were preserved even during the bandnoise stimuli at various bandwidth and spectral locations. The variability of FRA time-course between cell types may play a role for analyzing auditory spectral cues that vary with a wide range of time constant.

Critical spectral regions for vowel identification.

The first two formant frequencies (F1 and F2) are the cues important for vowel identification. In the categorization of the naturally spoken vowels, however, there are overlaps among the vowels in the F1 and F2 plane. The fundamental frequency (F0), the third formant frequency (F3) and the spectral envelope have been proposed as additional cues. In the present study, to investigate the spectral regions essential for the vowel identification, untrained subjects performed the forced-choice identification task in response to Japanese isolated vowels (/a, o, u, e, i/), in which some spectral regions were deleted. Minimum spectral regions needed for correct vowel identification were the two regions including F1 and F2 (the first and fourth in the quadrisected F1-F2 regions in Bark scale). This was true even when phonetically different vowels had a similar combination of F1 and F2 frequency components. F0 and F3 cues were not necessarily needed. It is concluded that the relative importance in the spectral region is not equivalent, but weighted on the two critical spectral regions. The auditory system may identify the vowels by analyzing the information of the spectral shapes and the formant frequencies (F1 and F2) in these critical spectral regions.

Tonal response patterns of primary auditory cortex neurons in alert cats.

The firing rates of primary auditory cortex (A1) neurons are known to be modulated only at the onset, offset, and change of a tonal stimulus in anesthetized animals. The tonal response pattern has been rarely investigated in alert animals. We investigated the time-course of A1 neuron responses to a steady tonal stimulus in alert cats. We found four types of firing responses based on statistical evaluation of the time course of the firing rate. The tonic cells (38 cells) showed a significant (P<0.05) firing increase throughout the stimulus period after a relatively long latency (mean, 25.3 ms) with little tendency of adaptation. The phasic-tonic cells (22 cells) showed a significant firing increase throughout the stimulus period after a medium latency (19.8 ms) with tendency of adaptation to less than a half of the maximum excitation level. Phasic cells (15 cells) responded, after a short latency (10.2 ms), at onset and offset of the stimuli. The unresponsive cells (26 cells) did not show a significant firing increase during stimuli. The findings suggest that there is a functional difference between each type of cells: the tonic cells encode information of static auditory signals in their firing rates; the phasic-tonic cells, of the changing auditory signal during the stimulus period; and the phasic cells, of rapid change of the auditory signal at onset and offset.