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Biomedical subjects

C L MacKenzie

Publications and source records attributed to C L MacKenzie.

18 recordsLinked to original sources
PubMed2006

A laboratory study on anticipatory movement in laparoscopic surgery: a behavioral indicator for team collaboration.

BACKGROUND: To assess team collaboration in the context of laparoscopic surgery, laparoscopic cutting tasks performed by single operators and dyad teams were observed. Our previous work suggested that the anticipatory movement performed by a teammate may lead to a shorter total task time than for a single bimanual operator. This report further explores this phenomenon by quantifying the frequency of anticipatory movements and discussing their significance to team collaboration. METHODS: Subjects were required to reach, grasp, and cut a piece of thread using a laparoscopic grasper and scissors. The task was performed by either 8 individual subjects bimanually or 16 paired subjects unimanually (using their preferred hands). The performances were video recorded. The total task time, the time used for thread grasping and cutting, and the number of anticipatory movements were computed and compared between the single operator and the dyad team group. In this report, anticipatory movement is defined as movements of the scissors before the completion of grasping and holding the thread. RESULTS: Shorter durations of total task time were shown for the dyad than for the bimanual group. Anticipatory movements were counted significantly more often when the scissors were controlled by a teammate on the dyad team (96%) than when they were controlled by the preferred hand of the operator (45%). The number of anticipatory movements increased with practice, but no significant difference was shown among practice phases. CONCLUSION: Higher frequency of anticipatory movement was observed in the dyad team, which led to superior performance for team collaboration, as compared with that of the single operator. Performance of anticipatory movements in the dyad team was explained by a shared mental model, which postulates combined capacity for information processing among team members. Results have implications for surgical education, team training, and error prevention in the performance of laparoscopic surgery.

Adult↗
PubMed2005

Video analysis of endoscopic cutting task performed by one versus two operators.

BACKGROUND: In the performance of complex laparoscopic tasks, one question is whether the task should be distributed between two operators or accomplished bimanually by one operator. The authors hypothesized that superior task performance results when two operators work collaboratively in a dyad team as opposed to one operator performing the task bimanually. Furthermore, in a visually misaligned condition, the performance of a team will be more robust than that of a single operator working alone. METHODS: The suture-cutting task was performed by 24 right-handed subjects in a mock surgical setup using a laparoscopic grasper and a pair of laparoscopic scissors. The cutting task was performed by 8 subjects bimanually (using both limbs) and 16 paired subjects unimanually (using their preferred limbs). The image of the work plane was displayed either vertically or superimposed over the work plane. In half of the conditions, the camera was rotated 45 degrees, causing misalignment between the actual and displayed work planes. Movements were videotaped. Important movement events were identified and used to subdivide the task into subtasks. Durations of the subtasks and attempts for grasping and cutting were analyzed using a mixed-design multivariate analysis of variance (MANOVA). RESULTS: For a number of subtasks, the dyad group showed shorter durations than the bimanual group. The 45 degrees rotation of the camera degraded both bimanual and dyad performance, resulting in prolonged movement times for all subtasks. The learning process was facilitated by the superimposed display in that grasper and scissor reaching times improved over trials, as compared with the vertical display. CONCLUSION: The results indicate the superior role of team collaboration, as compared with the single operator, in a complex remote manipulation such as a laparoscopic cutting task. This enhanced task performance is achieved because of the larger capacity for information processing. These results may have some relevance for optimizing performance of endoscopic surgery.

Adult↗
PubMed2003

Reaction times and the decision-making process in endoscopic surgery.

BACKGROUND: There are times during endoscopic procedures when the displayed surgical field does not align with the actual field due to rotation of the camera. The surgeon's performance may deteriorate under this situation. However, the effects of misalignment on the decision-making processes during endoscopic procedures have not been fully explored. The present study addresses this problem and suggests a technique that may be used to alleviate it. METHODS: Two experiments were completed in a mock endoscopic surgical setup where the image of the work plane inside the training box was either projected on a vertical monitor placed at eye level or superimposed over the training box by means of a half-silvered mirror. The work plane consisted of a start plate and four target plates. The experimenter varied the number of choices of target location among one, two, and four target choices. Rotating the camera about its longitudinal axis misaligned the displayed and the actual work plane. There were two experiments that differed in task difficulty. The task in experiment 1 was to touch the target plate, whereas the task in experiment 2 was to reach, grasp, and transport the object from the target to the start plate. RESULTS: Experiment 1 showed that reaction time increased with the number of the choices for a touch task, in accordance with the Hick-Hyman law. Using a grasp-and-transport task, experiment 2 replicated experiment 1 and extended the results to show that the use of a superimposed image display facilitated the decision-making process, leading to shorter reaction times compared to the vertical image display. DISCUSSION: During endoscopic procedures, the surgeon needs to translate indirect perceptions to instrument-mediated actions by "mapping" them through sensorimotor integration. The superimposed image alleviates the mental load of spatial transformations by reducing the difficulty of the required sensorimotor mapping. These findings have important implications for the design of high-quality superimposed display technologies.

Adult↗
PubMed2000

Contribution of visually perceived size to the scaling of fingertip forces when lifting a 'small' object.

The effects of visually perceived size of an object on the scaling of fingertip forces during lifting tasks were investigated using a small and lightweight object. A grip apparatus was attached to the top surface of three different size boxes of equal weight. 15 healthy adults were asked to grasp the grip apparatus with the thumb and index finger, lift it to a height of 5 cm, hold it for 8 sec., and then put it down. Force transducers embedded in the grip apparatus measured grip and load forces. When subjects lifted the same size object repeatedly, there were no size effects on the grip and load forces used by each subject. When the size was pseudorandomly varied, however, the grip and load forces exerted by 7 subjects significantly increased with increased size, while there were no size effects for the remaining subjects (n = 8). These results suggest a smaller contribution of information on size to the force programming when lifting a small object than when lifting a larger and heavier object as used in previous studies.

Adult↗
PubMed1999

Gaze patterns in laparoscopic surgery.

By understanding surgeons' patterns of gaze, and what visual information is being obtained during a procedure, one can improve the operation via new techniques or instrumentation. Part of a larger project on Remote Manipulation in Endoscopic Surgery, we analyzed eye patterns of surgeons from videotape annotation. Three categories of eye patterns were defined: 1) eyes on (gaze on monitor); 2) eyes down (gaze on external operative space); 3) eyes off (gaze away from monitor/hands). In the context of hierarchical decomposition of procedures we compared eye patterns and sequential dependencies (gaze as a function of previous gaze) by procedure, surgical steps and tasks. Timelines showed transitions in eye patterns during the procedure. We determined what visual information is available and what visual information is needed by the surgeons. By comparing these, we suggest technology that can provide these needs.

Feedback↗
PubMed1999

Virtual hand laboratory meets endoscopic surgery.

We describe two recent research projects: the Virtual Hand Laboratory, and Remote Manipulation in Endoscopic Surgery. The Virtual Hand Laboratory (VHL) is a prototype experimental tool for investigating human visuomotor coordination for object manipulation in augmented and virtual environments. The Remote Manipulation in Endoscopic Surgery (RMES) project examined surgeon's use of viewing and manipulating technologies in laparoscopic surgery, both in clinical and experimental settings. Current research brings together these two parallel research projects (VHL and RMES), for applications in planning and real-time execution of surgical procedures as well as for surgical training. We outline our research directions and detail current activities on superposition of display space on the workspace for the surgeon's hands.

Endoscopy↗
PubMed1999

Hierarchical decomposition of laparoscopic procedures.

The purpose of this report is to outline the hierarchical decomposition of surgical procedures, from surgical steps through tasks and subtasks to tool motions, and highlight implications for surgical training systems. Three common laparoscopic procedures were analysed: cholecystectomy, inguinal hernia repair, and Nissen fundoplication. In laparoscopic training workshops and operating rooms, our observational research included split screen videotaping of both the endoscopic view and our video camera's view of the primary surgeon. Videotapes were extensively annotated and analysed to yield timelines of each procedure, with component surgical steps, substeps, tasks, and subtasks duration as a function of procedure. The hierarchical decomposition of surgical procedures provides a framework for structuring a systematic approach to training, in the real and simulated environment. An example comparing variations in the fundoplication procedure is presented. Our results also have important implications for the design and assessment of new technology and intelligent tools in endoscopic surgery.

Cholecystectomy, Laparoscopic↗
PubMed1994

The speed-accuracy trade-off in manual prehension: effects of movement amplitude, object size and object width on kinematic characteristics.

Earlier studies have suggested that the size of an object to be grasped influences the time taken to complete a prehensile movement. However, the use of cylindrical objects in those studies confounded the effects of object size-extent orthogonal to the reach axis-and object width-extent along the reach axis. In separating these effects, the present study demonstrates that movement time is not affected by manipulation of object size, as long as the latter does not approach the maximal object size that can be grasped. Object width, on the other hand, is shown to exert a systematic influence on movement time: Smaller object widths give rise to longer movement times through a lengthening of the deceleration phase of the movement, thus reproducing the effect of target width on the kinematics of aiming movements. As in aiming, movement amplitude also affects the movement time in prehension, influencing primarily the acceleration phase (i.e. peak velocity attained). The effects of object width and movement amplitude were found to combine in a way predicted by Fitts' law, allowing a generalisation of the latter to the transport component in prehensile actions. With respect to the grasp component, both object size and object width are shown to affect peak hand aperture. Increasing object width thus lowers the spatial accuracy demands on the transport component, permitting a faster movement to emerge. At the same time, the hand opens to a larger grip in order to compensate for eventual directional errors that result.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

The effects of object weight on the kinematics of prehension.

The purpose of these experiments was to determine the effects of object weight and condition of weight presentation on the kinematics of human prehension. Subjects performed reaching and grasping movements to metal dowels whose visible characteristics were similar but whose weight varied (20, 55, 150, 410 g). Movements were performed under two conditions of weight presentation, random (weight unknown) and blocked (weight known). Three-dimensional movements of the thumb, index finger, and wrist were recorded, using a WATSMART system to obtain information regarding the grasp and transport components. The results of the first experiment indicated that object weight and condition of presentation affected the temporal and kinematic measures for both the grasp and transport components. In conjunction with the results of a second experiment, in which time in contact with the dowel was measured, it was shown that the free-motion phase of prehension (i.e., up to object contact) was invariant over the different conditions, however. The changes were observed in the finger-object interaction phase (when subjects applied forces after contact with the dowel), prior to lift-off. These results were interpreted as indicating (a) object weight does not influence the planning and execution of the free-motion phase of prehension and (b) there are at least two motor control phases involved in prehension, one for making contact with the object and the other for finger-object interaction. The changing contributions of visual, kinesthetic, and haptic information during these two phases is discussed.

Journal Article↗
PubMed1991

Is object texture a constraint on human prehension?: kinematic evidence.

The present experiment determined whether object texture influenced the transport and grasp components of human prehension. Infrared markers placed on the index finger, thumb, and wrist were recorded using a WATSMART system. The test objects were cylindrical dowels (103 mm high, 25 mm diameter, and 150 g in weight) of various surface materials (plain metal, coated with Vaseline, and covered with coarse sandpaper). Only temporal kinematic measures were affected by texture: Movement time (ms), time after peak deceleration (ms), percentages of movement time following maximum aperture, velocity, and deceleration were all significantly greater for the slippery dowel than the normal and rough dowels. Results indicated that the increased time associated with the slippery dowel could be explained entirely by increased time between contact with the dowel and dowel lift. Thus, these results are like those of Weir, MacKenzie, Marteniuk, Cargoe, and Frazer (1991), in which object weight was shown not to affect the free-motion phase, which includes the transport and grasp components of prehension. It appears that intrinsic object properties like weight and texture affect only the finger-object interaction phase of prehension; subsequent research is needed to dissociate inertial and surface friction effects while in contact with objects

Journal Article↗
PubMed1990

Integration of visual information and motor output in reaching and grasping: the contributions of peripheral and central vision.

This study examined the contributions made by peripheral and central vision to reaching and grasping. A specially designed contact lens system was used to restrict information to the peripheral retina. Modified goggles were used to restrict information to the central retina. A WATSMART motion analysis system was used to record and reconstruct three dimensional kinematic data. Analyses included an examination of peak kinematic values as well as a qualitative description of the trajectory profiles as related to transport and grasp components. With only peripheral vision, information related to size and shape of an object was inadequate, thus affecting the organization of both the transport and grasp components. With only central vision, information related to the location of an object was inadequate, affecting the organization of the transport but not the grasp component. Implications are discussed relevant to the current models of visuomotor control of reaching and grasping.

Adult↗
PubMed1989

Evidence for cerebral asymmetries in a finger sequencing task.

Visual input was lateralized using a specially designed contact lens system. Subjects performed a sequence of two keypresses in response to a light stimulus with either the left or the right hand in a choice reaction time paradigm. Two choice reaction time conditions were used: (A) hand certainty, sequence uncertainty and (B) hand uncertainty, sequence certainty. Reaction time (RT) results indicate that there are no significant differences between the left and right hemisphere in selecting a sequential response in either of the two conditions. Interfinger time (IFT) results show a relative left eye (right hemisphere)-left hand advantage when there was hand certainty, sequence uncertainty and a relative left eye (right hemisphere) disadvantage for both hands when there was hand uncertainty, sequence certainty. The RT results do not support the concept of a center in the left hemisphere for selection of the components of a two-element sequential keypress, prior to movement initiation. However, the IFT results indicate that there are differences in the processing ability of the left and right hemispheres in a sequencing task, after movement initiation.

Adult↗
PubMed1988

Manual localization of lateralized visual targets.

The effects of visual field, responding limb and extrapersonal space on the ability to localize visual targets using slow positioning movements of the arm were examined. Special contact lenses were used to lateralize visual information and to make comparisons with localization under monocular control conditions. Subjects made slow positioning movements to place a cursor directly beneath target lights. They saw target lights but not the moving limb during the trial. For directional error, results indicated that subjects were more accurate localizing targets lateralized to the right hemisphere than targets lateralized to the left hemisphere, indicating right hemisphere superiority for localization of visual targets in grasping space. Localization performance was significantly better with the right hand than the left hand. the left hand demonstrated a directional bias to the right of the targets. Responding hand and visual field did not interact. Finally, contrary to subjects' awareness and verbal reports, target localization was not less accurate in lens than in monocular control conditions. This was true for both amplitude and directional error. This is consistent with other studies where visual information about limb position is not available.

Journal Article↗
PubMed1985

Contact lens design for lateralizing visual input.

A contact lens designed for use in lateralizing visual input is described. The design includes a carrier soft contact lens into which a smaller hard contact lens is inserted. The hard lens is partially painted black to obstruct a portion of the visual field, as required for experimental purposes.

Brain Mapping↗
PubMed1981

Methods in the study of motor programming: is it just a matter of simple vs. choice reaction time? A comment on Klapp et al. (1979).

A recent article (Klapp, Abbott, Coffman, Greim, Snider, and Young, 1979) has concluded that central time demands of motor programming can only be determined by choice reaction time methodology. A critique of the theoretical position and results of this study is made showing that this conclusion is unwarranted. We go on to suggest that the simple vs. choice reaction time controversy might only be clouding a more basic issue in motor programming research; viz., identification of relevant internal response variables. Finally, a case is made for the notion that the choice reaction time paradigm may produce response competition (interference) effects and as a result confound measures presumed to reflect only the processes involved in the organization of movement.

Comment↗