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PubMed2003

Hand-assisted laparoscopic lymphadenectomy: a novel approach to a difficult area.

BACKGROUND: Hand-assisted laparoscopic surgery (HALS) is an emerging technique that is gaining acceptance for a wide range of abdominal procedures. We drew upon our growing experience with hand-assisted laparoscopic and thoracoscopic surgery to manage a case that was felt to require a major thoracoabdominal incision if it were to be completed by conventional open surgery. METHODS: A technique is described that combines the advantages of both laparoscopic and open surgery in the form of hand-assisted laparoscopic surgery to permit safe dissection of a retrocrural mass extending into the chest. RESULTS: We used this technique successfully to completely resect a nodal deposit of metastatic embryonal carcinoma previously thought to be inaccessible to surgical resection. CONCLUSION: The use of hand-assisted laparoscopic surgery improves tactile and visual feedback for the operator. This allows complex procedures involving delicate dissection to be completed safely and with less morbidity than open surgery.

Adult↗

PubMed1999

The effect of target proximity on the aniso-accommodative response.

Aniso-accommodation (unequal binocular accommodation) to lens-induced anisometropia has been demonstrated by subjective and objective measurement techniques (Marran and Schor, Vision Res. 38(22), 3601-3619). The gain of the response was significantly reduced for some subjects when aniso-accommodation was stimulated by a target at 1 m compared to a target at 20 cm, even when the targets viewed were matched in retinal image size, convergence levels and aniso-accommodative stimuli. The two conditions did differ in both the accommodative level and proximity of the target. Thus the higher gain of the response in the 20 cm condition could have arisen from either high proximity, high accommodative level or a combination of both. In this investigation, target proximity and accommodative level were manipulated independently while extra-retinal cues such as absolute disparity and image size were held constant. The results show that high target proximity alone rather than accommodative level or a combination of the two was responsible for the distance dependent effect demonstrated by subjects. Furthermore, accommodative level did not affect the response when target proximity was held constant. Subjects who demonstrated invariant aniso-accommodation with changes in viewing distance also demonstrated invariant aniso-accommodation with experimental manipulation of target proximity at the target distances tested, as would be expected. These results suggest that high level processing, rather than a reflex blur response, is involved in aniso-accommodation. This conclusion is strengthened by the previous finding of long reaction and response times, 11 and 15 s respectively, to step aniso-accommodative stimuli (Marran and Schor, Vision Res. 38(22), 3601-3619). Since the experimental target provided subjects with visual feedback of the relative blur of the dichoptically viewed letters, subjects had access to perceptual blur information cues. Some subjects seemed to have required both aniso-blur and proximity to exercise this volitional response. Those subjects who showed a distance invariant aniso-accommodative response may have been able to use perceived aniso-blur alone and their ability to disregard proximal cues may have resulted from greater experience with the aniso-accommodative stimuli. Alternatively, these subjects may have had a lower threshold to proximal stimuli and experienced target proximity at the more distant (1 m) viewing condition.

Accommodation, Ocular↗

PubMed2002

Differential refractive susceptibility to sustained nearwork.

PURPOSE: A possible role for nearwork-induced transient myopia (NITM) (i.e. transient myopia at distance following sustained nearwork) in the development and/or progression of permanent myopia has been suggested. If certain refractive groups are more susceptible to NITM than others, then measures may be implemented to prevent or retard the occurrence of myopia in these individuals. In a recent study (Ciuffreda and Wallis, 1998), it was found that young-adult late-onset myopes (LOM) and early-onset myopes (EOM) were highly susceptible to this NITM accommodative after-effect, while emmetropes (EMMs) were only moderately susceptible, and hyperopes (HYP) were particularly insusceptible, following short periods (10 min) of sustained nearwork at a very close distance (20 cm, 5 D). In the current study, this was extended to encompass a much longer period of nearwork under more naturalistic conditions. METHODS: Young-adult subjects (n = 16) performed a reading task for a continuous period of 4 h at their habitual working distance under naturalistic conditions, i.e. binocular viewing with blur-related visual feedback present. Distance refractive state (binocular viewing) was assessed objectively using a Canon R-1 autorefractor immediately before (pre-task), every hour during the task, and immediately after (post-task) to assess NITM and its subsequent decay to pre-task refractive levels. Subjects were divided into the four refractive subgroups as above, which were each of equal size (n = 4). RESULTS: The NITM was induced in all subjects, except for the hyperopes in which there was a hyperopic refractive shift. The LOMs (0.12 D) and EOMs (0.13 D) were highly susceptible, while the HYPs were especially insusceptible (0.44 D hyperopia), and the EMMs were only moderately susceptible (0.09 D). CONCLUSIONS: The present study extended our earlier investigation by demonstrating the differential refractive susceptibility over a longer period of sustained nearwork, which may be the result of reduced sympathetic activation. It has been speculated that NITM may be a factor in myopigenesis, with a possible mechanism being time-integrated increased retinal defocus from NITM at both distance and near, in conjunction with the normal lag of accommodation during sustained nearwork, thereby causing axial elongation. Hence, a future longitudinal investigation specifically targeting this retinal defocus hypothesis is warranted.

Accommodation, Ocular↗

PubMed2001

Brain-computer communication: self-regulation of slow cortical potentials for verbal communication.

OBJECTIVE: To test a training procedure designed to enable severely paralyzed patients to communicate by means of self-regulation of slow cortical potentials. DESIGN: Application of the Thought Translation Device to evaluate the procedure in patients with late-stage amyotrophic lateral sclerosis (ALS). SETTING: Training sessions in the patients' homes. PARTICIPANTS: Two male patients with late-stage ALS. INTERVENTIONS: Patients learned voluntary control of their slow cortical potentials by means of an interface between the brain and a computer. Training was based on visual feedback of slow cortical potentials shifts and operant learning principles. The learning process was divided into small steps of increasing difficulty. MAIN OUTCOME MEASURES: Accuracy of self-control of slow cortical potentials (percentage of correct responses). Learning progress calculated as a function of training session. RESULTS: Within 3 to 8 weeks, both patients learned to self-regulate their slow cortical potentials and to use this skill to select letters or words in the Language Support Program. CONCLUSIONS: This training schedule is the first to enable severely paralyzed patients to communicate without any voluntary muscle control by using self-regulation of an electroencephalogram potential only. The protocol could be a model for training patients in other brain-computer interface techniques.

Adult↗

PubMed2002

A non-invasive communication device for the paralyzed.

An EEG-based communication system has been developed to re-establish communication in severely paralyzed patients who operate the device by generating shifts of their slow cortical potentials. Training to gain control over slow cortical potentials was based on visual feedback and operant conditioning strategies. The vertical movement of a graphic signal on a computer screen informs the patients about the course of their slow cortical potential amplitude. Positive slow cortical potential shifts move the cursor up, negative shifts move it down. These shifts are then translated into binary responses. When a patient has achieved reliable control over his/her slow cortical potential shifts, these responses can be used to select or reject items presented at the bottom of the screen. As learning processes and applications differ considerably between patients, the present paper describes the data from one patient with amyotrophic lateral sclerosis. After about three months of training, this patient gained stable, near-perfect control over his slow cortical potentials. This skill enabled him to operate a specially designed program to communicate messages to his caregivers.

Adult↗

PubMed1984

[Optical-acoustical analogous biofeedback conditioning in the treatment of fecal incontinence in childhood].

This is a report on the treatment of anal incontinence by biofeedback conditioning. Since August 1982 9 children with incontinence (8 rectoanal agenesia, one Morbus Hirschsprung) were treated by simultaneous optical and acoustical analogous biofeedback conditioning. Training of sensitivity and voluntary contractions were performed and controlled electromanometrically. According to the pressure waves electrical alterations were transformed and feedback visually and acoustically. Results of the training of the maximal voluntary contraction are presented and the superiority of this method for the coordination of the anorectal sphincter function is stressed.

Adolescent↗

PubMed1994

Vagal Nerve Monitoring during Parapharyngeal Space Tumor Removal.

The vagus nerve innervates the intrinsic and extrinsic laryngeal musculature as well as the complex pharyngeal plexus. Acute paralysis of this nerve results in dysfunctional speech, deglutition, and airway protection. These untoward effects, which lead to additional infectious and aerodigestive complications, may arise following manipulation of the vagus nerve during the surgical removal of a variety of neoplasms found in the parapharyngeal space.The vagal nerve has been intraoperatively monitored in an effort to maintain its anatomic and functional integrity. Bipolar hook-wire electrodes are introduced transcutaneously through the cricothyroid membrane and are guided into the vocalis muscle by an assistant performing direct laryngoscopy. Continuous, real-time monitoring of the vagal nerve is provided by audio and visual feedback to the operating surgeon. Potentially injurious stretching, heating, and compression of the nerve are easily detected, and monopolar stimulation of the nerve is used to map the nerve's course through the tumor bed.This presentation outlines our technique for vagal nerve monitoring in patients with tumors of the parapharyngeal space and intact preoperative vocal cord mobility. Selected cases are presented and illustrated through intraoperative and postoperative videotapes.

Journal Article↗

PubMed2005

Interaction of vision and movement via a mirror.

I have noticed a striking effect that vision can have on movement: when a person makes circular motions with both hands, clockwise with the left hand, counterclockwise with the right hand, while watching the reflection of one hand in a parasagitally placed mirror, if one arm makes a vertical excursion, the other arm tends to make the same vertical excursion, but not typically if the excursing arm is viewed in plain vision. This observation may help in understanding how visual feedback via a mirror may be beneficial for rehabilitation of some patients with movement deficits secondary to certain neurologic conditions, and illustrates that the traditional division of neural processes into sensory input and motor output is somewhat arbitrary.

Feedback, Psychological↗

PubMed2000

Monocular and binocular vision in the control of goal-directed movement.

In the present research the authors examined the time course of binocular integration in goal-directed aiming and grasping. With liquid-crystal goggles, the authors manipulated vision independently to the right and left eyes of 10 students during movement preparation and movement execution. Contrary to earlier findings reported in catching experiments (I. Olivier, D. J. Weeks, K. L. Ricker, J. Lyons, & D. Elliott, 1998), neither a temporal nor a spatial binocular advantage was obtained in 1 grasping and 2 aiming studies. That result suggests that, at least in some circumstances, monocular vision is sufficient for the precise control of limb movements. In a final aiming experiment involving 3-dimensional spatial variability and no trial-to-trial visual feedback about performance, binocular vision was associated with greater spatial accuracy. Binocular superiority appeared to be most pronounced when participants were unable to adjust their limb control strategy or procedure on the basis of terminal feedback about performance.

Adult↗

PubMed1983

The lateral coding of rotations: a study of the simon effect with wheel-rotation responses.

A number of experimental studies have consistently shown the locus of spatial S-R compatibility effects to be the selection of the response within an abstract memory code. The purpose of the present study was to test, in the particular case of wheel rotations, the general proposition that any response that a subject internally codes in terms of left and right may be interfered with by the lateral location of the stimuli in a Simon paradigm. Experiment 1 showed that the auditory Simon effect occurred in a task where the subjects had to rotate a steering wheel bimanually either clockwise or counterclockwise according to sound pitch, despite the fact that responses of this kind are undefined with respect to laterality. Experiment 2 confirmed this result in a unimanual rotation condition and suggested that the ear-rotation compatibility effect may be added to the effect of a biomechanical factor, pronation versus supination, supporting the idea of an abstraction motor code. In Experiment 3, subjects rotated the steering wheel with their hands on the lowest part of the wheel. When the response movement made the spot of a C.R.T. move laterally in accordance with the performed rotation, the subjects coded their response directly in terms of its effect on the visual display. For subjects not receiving visual feedback, no compatibility effect occurred. however, the individual data were compatible with the notion that some subjects in this group coded their responses in terms of wheel rotations, and others in terms of hand movements.

Journal Article↗

PubMed1984

The timing of natural prehension movements.

Prehension movements were studied by film in 7 adult subjects. Transportation of the hand to the target-object location had features very similar to any aiming arm movement, that is, it involved a fast-velocity initial phase and a low-velocity final phase. The peak velocity of the movement was highly correlated with its amplitude, although total movement duration tended to remain invariant when target distance was changed. The low-velocity phase consistently began after about 75% of movement time had elapsed. This ration was maintained for different movement amplitudes. Formation of the finger grip occurred during hand transportation. Fingers were first stretched and then began to close in anticipation to contact with the object. The onset of the closure phase was highly correlated to the beginning of the low velocity phase of transportation. This pattern for both transportation and finger grip formation was maintained in conditions whether visual feedback from the moving limb was present or not. Implications of these findings for the central programming of multisegmental movements are discussed.

Journal Article↗

PubMed1985

Some aspects of the motor organization of the oculomotor system.

Oculomotor responses in looking to visual targets were examined for motor coordination parallel to that found in manual pointing. ocular responses did not show any evidence that speed-accuracy tradeoff when the correlation of latency (reaction time) and accuracy was assessed. The oculomotor system did show a range effect, hidden under a general undershoot of target position and present only when no visual feedback about target position was available to allow correction during the movement. Cues to allow predictive timing of the response seemed very important for oculomotor reaction time. processing of timing of movement may be handled differently for oculomotor than for manual orienting, and calculation of position in space may be processed in common, leading to both similarities and differences for the two motor systems.

Journal Article↗

PubMed1988

The effects of time and distance on accuracy of target-directed locomotion: does an accurate short-term memory for spatial location exist?

The present study was an attempt to replicate the findings of an influential set of experiments by Thomson (1980, 1983) in which he demonstrated a highly accurate but transitory short-term memory for target location during locomotion. No evidence of Thomson's rapidly decaying 8 s short-term memory was found in either of the two experiments presented here. The distance to the target, not the elapsed time, was found to be the major variable affecting the accuracy of walks made without the benefit of visual feedback; as target distance increased so did locomotor error. Increasing the elapsed time to more than 8 s between viewing the target and reaching the vicinity of the target had no effect on the accuracy of walks made with eyes closed. When the elapsed time was greater than 30 s, however, performance began to deteriorate. These results suggest, in sharp contrast to Thomson's experiments, that short-term memory for target location decays rather slowly during locomotion. In this regard, short-term memory in locomotor tasks appears to be little different from the kinds of short-term memory associated with other motor acts.

Journal Article↗

PubMed1990

Tracking with and without target in 6- to 15-year-old boys.

It is well documented that, in adults, manual tracking of a visual periodic target is very accurate in a wide variety of experimental conditions. With children between 5 and 9 years of age, however, the response lags significantly behind the stimulus. The first study presented here attempts to described the acquisition of this skill by children between 9 and 15 years of age. Within this age span, adult proficiency in pursuing a rapid target was approached through an improvement in response synchronization. Yet adults were distinguishable from the oldest children by a fundamentally different mode of movement execution: The former maintained a smooth modulation of the proper motor pattern, whereas the latter relied mainly on corrections through visual feedback. The second experiment showed that these different perceptuomotor strategies may be related to the availability of a more accurate and stable motor pattern with age. Young children had difficulties reproducing the stimulus after it was withdrawn, with performance deteriorating as the trial progressed. The initial mismatch and the following drift tended to decrease with age, even though the oldest children's stationary performance was still not as consistent with the target motion as the adult response.

Journal Article↗

PubMed1991

Interactions between goal-directed eye and arm movements: arguments for an interdependent motor control.

The accuracy of movements of the arm directed toward a point in space was investigated in healthy human subjects. To study the influence of the eye movement itself, on the guidance of the arm in the absence of any visual context, subjects performed the goal-directed arm movements without visual feedback about the arm displacement and the target position. The subjects were asked either to keep their eyes centered or oriented toward a previously flashed target. The analysis of the distribution of the errors in arm final position in the two conditions suggests that the eye movement influences the final position adopted by the arm. It is postulated that an interaction exists between the eye and arm systems during the motor program elaboration phase.

Journal Article↗

PubMed1992

Evidence for an error deadzone in compensatory tracking.

Humans and monkeys show intermittent arm movements while tracking moving targets. This intermittency has been explained by postulating either a psychological refractory period after each movement and/or an error deadzone, an area surrounding the target within which movements are not initiated. We present a technique to detect and quantify the size of this deadzone, using a compensatory tracking paradigm that distinguishes it from a psychological refractory period. An artificial deadzone of variable size was added around a visual target displayed on a computer screen. While the subject was within this area, he received visual feedback that showed him to be directly on target. The presence of this artificial deadzone could affect tracking performance only if it exceeded the size of his intrinsic deadzone. Therefore, the size of artificial deadzone at which performance began to be affected revealed the size of the intrinsic deadzone. Measured at the subjects' eye, the deadzone was found to vary between 0.06 and 0.38 degrees, depending on the tracking task and viewing conditions; on the screen, this range was 1.3 mm to 3.3 mm. It increased with increasing speed of the target, with increasing viewing distance, and when the amplitude of the movement required was reduced. However, the deadzone size was not significantly correlated with the subjects' level of performance. We conclude that an intrinsic deadzone exists during compensatory tracking, and we suggest that its size is set by a cognitive process not simply related to the difficulty of the tracking task.

Journal Article↗

PubMed1996

Mechanisms controlling head stabilization in the elderly during random rotations in the vertical plane.

Frequency-related response characteristics of the mechanisms controlling stabilization of the head in 10 elderly subjects were compared with response characteristics in 8 young adults. Angular velocity of the head with respect to the trunk and EMG responses of 2 neck muscles were recorded in 10 seated subjects during pseudorandom rotations of the trunk in the sagittal plane at frequencies of 0.35 to 3.05 Hz. Subjects were required to actively stabilize their heads with (VS) and without (NY) visual feedback so that voluntary mechanisms and the influence of vision could be tested. Reflex mechanisms were examined when subjects were distracted by a mental calculation task during rotations in the dark (MA). Age emerged as an influential factor in the performance of head stabilization mechanisms, and decrements in performance were even more pronounced in the older as compared with younger elderly subjects. Age effects could be seen in the (a) diminished ability to voluntarily stabilize the head, particularly with the absence of vision, (b) impaired ability to stabilize the head when cognitively distracted, and (c) appearance of a resonant response of the head. Control of head stabilization shifted from reflex mechanisms to system mechanics, probably as a result of age-related changes in the integrity of the sensory systems. The elderly's system mechanics could not effectively compensate for the disturbances, however, and instability was the result.

Journal Article↗

PubMed1996

Age-related differences in the integration of sensory information during the execution of a bimanual coordination task.

Young (n = 7) and elderly (n = 7) subjects performed bimanual coordination patterns in the transverse plane according to the in-phase or antiphase mode. Sensory information was manipulated through visual (with or without vision of the limbs) and proprioceptive input (with or without vibratory stimuli on one limb). Movement patterns with vibrations showed higher deviations from the intended relative phase than did those without vibrations. This finding suggests that the proprioceptive information induced by the vibrations and the movement interfered, leading to a disruption of the coordination patterns. In addition, as compared with the elderly, the young subjects performed more stable movements under normal circumstances but were more strongly affected by vibratory stimuli during the performance of in-phase movements. During antiphase movements, both age groups experienced a decrease of pattern stability. Furthermore, the absence or presence of visual feedback influenced the performance of the young subjects more than that of the elderly. The presence of vision led to stable in-phase movements, whereas a decrease of pattern stability was observed for antiphase movements. In general, these results demonstrate that manipulation of feedback sources affects young subjects more than elderly ones, and this can be related to a reduced sensory sensitivity as a function of aging.

Journal Article↗