High-velocity Movements Research Articles

Automatic recognition of fast and slow phases in nystagmic eye movements using a neural network

This paper presents an algorithm for the automatic classification of fast and slow phases during nystagmic eye movements, using a neural network. When a patient is presented with a nonstationary visual field, the resulting eye movements may be used to determine valuable clinical information about patients with vertigo and balance disorders. When the nonstationary visual field is induced by sinusoidally rotating the patient in a chair, the eye movements—collectively referred to as nystagmus—typically consist of short, high-velocity movements (fast phases) which are in the direction of the stimulus and longer, low-velocity movements (slow phases) which are in the direction opposite to that of the stimulus. The slow phases are produced to compensate for the moving visual field. By extrapolating over the fast-phase segments, the slow-phase segments can be pieced together to form a slow-phase response. When the stimulus is sinusoidal, the slow phase response is also sinusoidal and the magnitude and phase relationships between the stimulus and response may be used to help identify the source of the patient's disorder. Thus, the ability to accurately reconstruct the response from the slow-phase segments is extremely important. This, in turn, necessitates the ability to accurately determine the locations of the fast and slow phases of nystagmus. For the neural network used here, the optimal input feature set and number of hidden units are determined, along with the necessary preprocessing of the network inputs and the postprocessing of the network output data. It is also shown that an effective error-correction algorithm can be applied to the outputs of the neural network to improve its classification ability. Finally, results are presented for the performance of the network on independent sets of test data. The classifications obtained from the neural network when applied to the test data are much more accurate than those obtained using two current classifiers: an algorithm proposed by Wall and Black and an algorithm proposed by Jell, Turnipseed and Guedry

The Effects of Cold Immersion on Muscle Strength

ABSTRACT This study examined the effects of cold water immersion on isokinetic and isometric strength on 10 physically active male college students. Isokinetic knee extension strength (30,180,300, and 400 · sec−1) and isometric strength were assessed. Isometric testing consisted of 5-see isometric knee extension muscle actions at a 45° angle. Subjects randomly performed all three treatment conditions: a cold treatment (12°C), thermal neutral treatment (35.5°C), or nonimmersion room temperature treatment (22–23°C). For the cold and thermal neutral treatments both thighs were immersed in a whirlpool tank with moving water leveled to each subject's gluteal fold. Treatments lasted 45 min. Higher isokinetic velocities demonstrated a significant decrease in average peak torque, average power, and total work. No significant changes were observed for isometric force or low velocity movements. No significant decreases were observed for the angle of peak torque or for time to peak torque. This study demonstrated that if the thighs are immersed in cold water, functional strength performance at higher movement velocities will be impaired.

Velocity specificity of resistance training.

Velocity specificity of resistance training has demonstrated that the greatest strength gains occur at or near the training velocity. There is also evidence that the intent to make a high speed contraction may be the most crucial factor in velocity specificity. The mechanisms underlying the velocity-specific training effect may reside in both neural and muscular components. Muscular adaptations such as hypertrophy may inhibit high velocity strength adaptations due to changes in muscle architecture. However, some studies have reported velocity-specific contractile property adaptations suggesting changes in muscle kinetics. There is evidence to suggest velocity-specific electromyographic (EMG) adaptations with explosive jump training. Other researchers have hypothesised neural adaptations because of a lack of electrically evoked changes in relation to significant voluntary improvements. These neural adaptations may include the selective activation of motor units and/or muscles, especially with high velocity alternating contractions. Although the incidence of motor unit synchronisation increases with training, its contribution to velocity-specific strength gains is unclear. However, increased synchronisation may occur more frequently with the premovement silent period before ballistic contractions. The preprogrammed neural circuitry of ballistic contractions suggests that high velocity training adaptations may involve significant neural adaptations. The unique firing frequency associated with ballistic contractions would suggest possible adaptations in the frequency of motor unit discharge. Although co-contraction of antagonists increases with training and high velocity movement, its contribution is probably related more to joint protection than the velocity-specific training effect.

Neuromotor noise and poor handwriting in children

In this article Power Spectral Density Analysis of the velocity profile of handwriting tasks is applied to estimate movement noise in poor and proficient writers. It is hypothesized that poor writers are less effective in the inhibition of neuromotor noise. Evidence for this theory is found in an analysis of electronically sampled handwriting movements of 48 children from grade 2, 3 and 4 (mean ages 8, 9 and 10, resp.). Twenty-four were poor and 24 were good writers, as judged by their teachers. Subjects were matched on age, sex, handedness and educational level. They performed handwriting tasks consisting of simple garlands and arcades, or meaningless words built from the letters ‘e’, ‘n’ and ‘m’. In the tasks stroke accuracy, size and rational direction were systematically varied. The results reveal that movement times were not different between the two groups, but poor writers and good writers used different movement strategies. Movements of the less proficient children were larger and were produced with higher movement velocities. Power Spectral Density Analysis disclosed that handwriting movements of poor writers were substantially more noisy than those of proficient writers, with a consistent peaking of the noise energy in that region of the spectrum which is representative for neuromotor tremor. Also, poor writere were less successful in adapting the level of noise to increased accuracy demands of the tasks. The results support the view that deviant biomechanical strategies might be responsible for deficient motor performance.

Intended rather than actual movement velocity determines velocity-specific training response.

Eight men and eight women trained 3 days/wk for 16 wk by doing attempted ballistic unilateral ankle dorsiflexions against resistance that either rendered the resultant contractions isometric (one limb) or allowed a relatively high-velocity (5.23 rad/s on an isokinetic dynamometer) movement (other limb). Training sessions consisted of five sets of 10 contractions of each type. Training produced the same high-velocity-specific training response in both limbs (P < 0.001). Peak torque increased most at 5.23 rad/s (38%) in comparison to lower velocities (0, 0.26, 0.52, 1.04, 1.55, 3.02, and 4.19 rad/s). Both limbs also showed similar increases in voluntary isometric rate of torque development (26%) and relaxation (47%) and in evoked tetanus rate of torque development (14%). A similar decrease in evoked twitch time to peak torque (6%) and half-relaxation time (11%) was also observed. Thus, all of these training responses, previously associated specifically with high-velocity resistance training, were produced by a training regimen that prevented an actual rapid movement through a range of movement. The results suggest that the principal stimuli for the high-velocity training response are the repeated attempts to perform ballistic contractions and the high rate of force development of the ensuing contraction. The type of muscle action (isometric or concentric) appears to be of lesser importance.

Multi-Joint Reaching Movements and Eye-Hand Tracking in Cerebellar Incoordination: Investigation of a Patient with Complete Loss of Purkinje Cells

Performance on an eye-hand tracking task and a multi-joint reaching movement to a visual target was studied in a patient with stable cerebellar ataxia and in control subjects. The patient subsequently died and a full neuropathological examination was performed. The neuropathological findings were similar to those seen in patients with paraneoplastic cerebellar degeneration, but no tumor was found at autopsy eight years after onset of the patient's cerebellar syndrome. A severe cerebellar cortical degeneration with complete Purkinje cell loss was demonstrated, whereas cerebellar nuclei and brainstem structures showed no neuronal loss. Tracking performance by the patient was characterized by abnormally large numbers of high velocity movements and hand direction reversals, and by excessive lagging of the hand behind the target in time. In the multi-joint reaching movement, the patient showed a delay in movement onset at the elbow joint compared to movement onset at the shoulder joint. The velocity profile of the movement at the shoulder joint was abnormal. The duration of the acceleration phase was poorly correlated with both peak angular velocity and the duration of the deceleration phase. One of the most striking findings was the inability of the patient to consistently produce the same movement direction from trial to trial while reaching to the same target. Our data suggests that the cerebellar cortex is involved in multiple aspects of motor control including visuomotor integration mechanisms.

Physiology and Structure of Three New Uropod Proprioceptors in the Crayfish Procambarus Clarkii

ABSTRACT Three new chordotonal organs are described: APCO for the abdominal-proto-podite joint, PExCO for the protopodite-exopodite joint and PEnCO for the protopodite-endopodite joint of the crayfish uropod. The PEnCO is a distinct strand chordotonal organ, while the APCO and PExCO are webbed structures arising from peripheral nerve roots 2 and 3 of the terminal abdominal ganglion, in which some of their somata are located (‘root cells’). Physiological experiments showed that the organs monitor position and movement at all three joints. Position monitoring is limited to open angles of the exopodite and extended angles of the protopodite (no limits on endopodite position sensitivity). Distinct hysteresis is shown by most position-sensitive units. The abdomen-protopodite joint is monitored through four orders of velocity magnitude, while the exopodite and endopodite, which are involved in tailfan flare, are primarily monitored at high movement velocities. Large, phasic units in all three chordotonal organs (COs) can monitor continuous, high-velocity movement with little adaptation. These results are discussed in relation to known motor control mechanisms for crayfish uropods during swimming, walking, escape and righting behaviours.

Lip movement in apraxia of speech.

Peak articulatory velocity of the lower lip and temporal coordination between the upper and lower lips were studied in 5 neurologically impaired subjects with speech behaviors consistent with a diagnosis of apraxia of speech. Differences in velocity and the timing between the movement onset of the two lips were compared for accurate and inaccurate productions of words. Peak articulatory velocity also was measured during the productions of the syllable [pae] and during a nonverbal movement. There were no systematic differences across accurate and inaccurate productions of words in peak articulatory velocity or movement onsets of the two lips. Furthermore, there were no systematic changes in movement velocity related to speech rate. We conclude that some apraxic speakers do not have a defect in the ability to produce high movement velocities.

Organization and properties of neurons in a visual area within the insular cortex of the cat

1. Extracellular recordings from 304 neurons were obtained with carbon fiber-containing multibarrel micropipettes. The cells were isolated in the insula in cats anesthetized with barbiturate and immobilized with gallamine triethiodide. Cells were tested with visual stimuli in the form of bars of light, moving edges, and square-wave, drifting grating patterns. 2. The spatial extent of the visually responsive region of insular cortex was assessed and was found to be limited to a surface area of approximately 6-8 mm2, the perimeter being delimited caudally by visually unresponsive cortex of the anterior sylvian gyrus, rostrally by the cortex surrounding the posterior third of the orbital sulcus (ventral bank), dorsally by the rostral extension of the dorsal bank of the anterior ectosylvian sulcus, and ventrally by a visually unresponsive zone bounded by a region about 2 mm2 ventrolateral from the anterior ectosylvian sulcal infolding. Furthermore, a group of unimodal, visually responsive cells often was found in the upper bank of the anterior rhinal sulcus. 3. The possibility of there being a visuotopic organization of insular neurons was examined by analyzing the distribution of receptive-field representation of neurons in sequential penetrations, as well as by searching for spatial progressions in the locations of visually responsive areas within the region. No such clear-cut organization was found among the cells of the insula. 4. Visually responsive neurons were encountered in groups, within electrode penetrations. These groupings were roughly segregated into three distinct levels within the depth of the cortex: the first between the pial surface and 600 micron, the second between 1,100 micron and 1,800 micron, and the third between 2,000 micron and 2,500 micron. 5. Neurons were classified according to their velocity sensitivity, directional preference, orientation sensitivity, length preference, modality specificity, response to electrical stimulation of extrageniculostriate regions, and response to light stimulation in the presence of microiontophoretically administered bicuculline methiodide (BMI). 6. Cells of superficial layers tended to exhibit a preference for high-velocity movements of light bars (600 degrees s-1), whereas those of deeper laminae generally preferred relatively lower velocity movements (60 degrees s-1). The clear preferences of many cells for certain directions of movement within the 360 degrees arc suggested the presence of a dynamic orientation sensitivity. 7. Proportionately more cells preferred moving bars (57%) to small moving spots (43%).(ABSTRACT TRUNCATED AT 400 WORDS)

Physiological properties of visually responsive neurones in the insular cortex of the cat

Extracellularly recorded responses of neurones in the insula and the adjoining rostroventral bank of the anterior ectosylvian sulcus to moving bars of light and to electrical stimulation of the superior colliculus and suprageniculate nucleus were recorded in barbiturate-anaesthetized cats. Insular cortical neurones had extremely large receptive fields, exhibited a high incidence of directional selectivity, responded best to high or medium velocity movements of the stimulus and some displayed fairly powerful end-inhibitions. Orthodromically elicited responses from the superior colliculus and suprageniculate nucleus were obtained at latencies of 5–6.5 ms and 3.0–6.0 ms, respectively. No polysensory responses were obtained from visually sensitive neurones. These data provide evidence that a population of neurones in the dorsal rim of the insula comprise a visual area which may be closely related anatomically and functionally to the recently described anterior ectosylvian visual area.

Functional and developmental analysis of a visual corticopretectal pathway in the cat: a neuroanatomical and electrophysiological study.

The sensory corticopretectal projection in the cat and in its postnatal development were investigated combining neuroanatomical and electrophysiological techniques. The anatomical pattern of fiber termination was studied in relation to age using the anterograde HRP tracing method. Large injections were made in areas 17 and 18 of one or both hemispheres in 1-13 week old kittens and cats. Terminal label in the ipsilateral pretectum was seen only after the fourth week of life. Electrical stimulation in the same cortical areas evoked postsynaptic orthodromic excitation in 9-18% of cells at 4 weeks increasing to about 60% in the adult. In cats, but not in kittens, successful stimulation depended on the retinotopic matching of stimulation and recording sites. In adult cats a high incidence of direction and velocity tuning and a high degree of binocularity were seen in cells driven by the cortex as opposed to cells not so driven. Cortex driven cells in cats and kittens received convergent retinal input mainly via direct W-fibers, whereas cells not driven from cortex shock mainly received delayed W-fiber input. In kittens visual responses lacked sensitivity for direction and high movement velocity of patterns until 6 weeks postnatally, whereas ocular dominance distribution was not age-dependent.

Information processing deficits in Parkinson's disease during movement

The capacity to process information during movement selection and execution was studied in Parkinsonian patients and controls in a task involving movement of a hand-held stylus between two targets whose size and separation could be systematicaly varied. Movement time and accuracy were evaluated when the size and required accuracy of movements were changed to modify movement difficulty. Movement time and inaccuracy of patients with Parkinson's disease were exaggerated by increasing target separation so as to increase movement extent (target size held constant) or by decreasing target size (target separation held constant). The fact that these changes in task difficulty caused greater deterioration of performance for patients than for controls is consistent with previous studies indicating that Parkinsonian patients have deficits in executing high-velocity movements. These data also show that performance deficits by Parkinsonian patients can be brought out by increasing movement difficulty through requiring increased movement accuracy. These findings are interpreted in relation to the relative contribution of deficits in movement execution vs motor programming in the motor disorders of Parkinson's disease.

Eye position signals in the flocculus of the monkey during smooth-pursuit eye movements.

1. Discharges of Purkinje cells and mossy fibres were recorded from the flocculus of monkeys trained to fixate a small visual target and to track the target when it moved slowly.2. Discharges of Purkinje cells changed tonically with shifts of gaze. Firing rates were linearly related to eye positions for either the entire or more than half the eye-position range in 12.6% of Purkinje cells tested (76/603 units).3. The eye position-related activity (position component) was observable in these cells also during smooth-pursuit eye movements. It was typically seen during slow eye movements (velocities less than 10 deg/s) but became undetectable during high velocity movements (faster than 50 deg/s).4. The position component became prominent when smooth pursuit was executed at the preferred loci of the individual cells. In the majority of the cells tested at their preferred loci, the position component was observable to a relatively high frequency, such as 0.5 Hz (+/- 10 deg; peak velocity 31 deg/s).5. Forty-five mossy fibre units showed saccade-related bursts and position-related intersaccadic tonic activity during steady eye position. In each unit, the position component was found only during fixations within a specific range of eye positions. During fixations outside these regions, all position-related mossy fibres were completely silent.6. During sinusoidal smooth-pursuit eye movements, the mossy fibres also displayed cyclic modulations in activity. All fibres discharged with eye movements in one direction and were silent during eye movements in the other direction.7. Saccade-related bursts from mossy fibres led the onset of saccades, ranging from 0 to 19 ms with a mean lead-time of 6.9 ms. This observation negates the possibility that the position-related signals might represent proprioceptive impulses from the stretch receptors of the extraocular muscle.

Attention demands of movements as a function of their duration and velocity

The attention demands of initiating and controlling discrete movements were examined as a function of their movement time (MT) and average movement velocity. Experiment 1 showed that the attention required to execute a movement decreased as MT decreased, although Experiment 2 through independently manipulating MT and movement velocity, revealed that movement velocity is the key determiner of attention demands rather than MT. The attention demands of preparing a high velocity movement are greater than during its execution with the reverse being the case for relatively slow velocity movements. The results are compatible with the view that it is the initiation of error corrections that are attention demanding (Keele 1973).

The physiological basis of tactile sensibility in the beak of geese

The discharges in single afferent fibres of the ophthalmic nerve innervating the upper beak in two kinds of geese (Anser anser andAnser albifrons) were studied during manual and controlled mechanical stimulation. Three types of unit were recorded. 1) Rapidly adapting units deriving from Grandry corpuscles had receptive fields of up to 12 mm in diameter which overlapped or enclosed each other in certain beak skin areas. They responded quantitatively to the velocity of a displacement and there was a wide range of variability in the threshold sensitivity of minimal required displacements and the sensitivity to changes in the stimulus velocity. Grandry units were not spontaneously active and lacked an amplitude component in the response to trapezoidal stimuli. 2) Rapidly adapting units, almost certainly deriving from Herbst corpuscles, required high movement velocities to be activated and appeared to respond only to the acceleration or deceleration phase of a movement. Consequently, Herbst units were excited optimally by vibratory stimuli between 40 and 1500 cycles/sec. A consistent relationship between the velocity of a trapezoidal stimulus and the frequency of discharge in Herbst units could not be demonstrated. The units were not spontaneously active and were located in receptive fields which were often small but could occasionally cover the whole beak. 3) Slowly adapting units deriving from a still unidentified morphological structure were found to originate exclusively in the horny tip of the bill. These units were often spontaneously active and two kinds of slowly adapting discharge with a regular and an irregular discharge were observed. Trapezoidal stimuli elicited both dynamic and static responses which were proportional to the velocity of the movement and its displacement amplitude, respectively. Larger displacements were followed by silent periods which increased in duration with increasing displacement amplitudes. The time course of the adaptation of a response to a constant displacement showed several time constants. The discharge frequency increased on cooling and decreased on warming the receptive field. 4) The experimental findings are discussed with respect to morphological and other physiological results. A model of the operating principle in tactile sensory mechanisms in the goose is proposed, based on the evidence of the morphological and physiological organization of mechanoreceptors and primary afferent units in the beak skin of geese.

A Punch-Card-Controlled Component-Part Insertion Machine

A new high-speed programmed insertion device for axial-lead component parts is described, which produces the "Y" coordinate motion by movement of the printed wiring board and the "X" and "Z" motion by movements of the insertion head. Although the basic idea is not new, it is claimed that its combination with novel mechanisms has resulted in a truly high-speed experimental programmed machine. Success of the machine is credited to a new small-and lightweight inserting tool, which allows high-velocity movement, using low power, and with reduced resonance. A series of pneumatic cylinders are shown, following the binary progression to provide specific strokes by IBM punched-card control, for both lead preparation and insertion. Salient features of the mechanism are described as follows: a) almost any part under a diameter of 0.250 inch and a length of 0.850 inch can be handled, b) component parts are center-taped on reels after wrap-around terminals have been added, c) torque sleeves and yokes remove component parts from the tape reels, d) cards are stacked and conveyor fed to the insertion head, e) the controller is in console form, and takes binary-coded cards directly without the need for a decoder, and f) 1,920 bits of information are available from only two cards. Factors which have been experienced in connection with the manufacture of Sage Computers at IBM Kingston are mentioned. It is claimed that for over two-million insertions, most failures have been eliminated, even though insertion is at the average rate of 60 per minute. Potential of the system is estimated at a maintained speed of at least 120 per minute, with its future hinted by the insertion speed of less than 0.1 second which has been attained. Possible utilization of the equipment for other purposes is stressed, such as for programmed drilling.