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Abstract—Better rehabilitation outcomes have been linked to higher levels of motivation in animal models of stroke recovery. Virtual reality environments have been postulated to increase the participant’s level of engagement and motivation in performing motor tasks. We evaluated motivation and presence in two groups of healthy participants (<25 yrs old; ≥25yrs old) performing similar reaching tasks in four different environments – physical, 2D virtual reality, 3D virtual reality and video game. Sense of presence and motivation in each environment were assessed. Overall, the participants rated the video gaming environment as being the most motivating and enjoyable. The level of presence was related to motivation for the younger group only for the 2D VR environment but for all three VR environments in the older group. Our findings suggest that training environments can be made more motivating using virtual reality which is an important factor in maximizing motor recovery in neurological patients. Further research is needed to develop highly motivating applications suited to specific rehabilitation goals and patient needs.

I. INTRODUCTION OTIVATION drives the choice of certain behaviors or actions over others. It directly affects the initiation,

direction, intensity and persistence of a behavior contributing to the achievement of the desired goal. There are two distinct types of motivation: extrinsic and intrinsic. Extrinsic motivation occurs when the individual receives encouragement to perform the activity by another person or factor, while intrinsic motivation occurs when the individual generates interest by himself [1]. Intrinsic motivation plays an important role in achieving better rehabilitation outcomes [2], [3]. Individuals who are intrinsically motivated and strongly believe in their physical capacity show better adherence to therapy, put greater effort into the activity and challenge themselves more to achieve the desired outcome. In clinical settings, therapists motivate patients by setting specific attainable goals, using tasks that are challenging and meaningful to the person, providing patients with clear

Manuscript received April 15, 2008. This work was supported in part by

Canadian Foundation for Innovation and Heart and Stroke Foundation of Canada. LA was a grantee of the Canadian Stroke Network. MFL holds a Canada Research Chair in Motor Control and Rehabilitation.

C. B. Lourenco is an exchange student from the State University of Campinas, SP, Brazil, at the School of Physical and Occupational Therapy, McGill University. ( email: chris_lourenco@yahoo.com)

L. Azeff and M. F. Levin are with the School of Physical and Occupational Therapy, McGill University, 3654 Promenade Sir William Osler, Montreal, Quebec. (e-mail: lisa.azeff@mail.mcgill.ca; mindy.levin@mcgill.ca).

H. Sveistrup is with the School of rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa, Canada (e-mail: heidi.sveistrup@uottawa.ca).

instructions on how to complete the task so that the patient feels that he or she has some control over the environment.

Recent research has identified several factors that are linked to maximizing motor learning and motor recovery in individuals who have neurological lesions. One key feature is how much the individual is motivated by and engaged in the activity. Clinicians are challenged to identify motivating and effective intervention methods that will result in functional gains in real-world activities [1], [4]. Virtual reality (VR) technology may address this problem. To date, several studies have used different forms of immersive and non-immersive VR to improve upper limb function in neurological patients (e.g., [5]-[8]). VR provides the added attributes of motivation and innovation as well as the possibility to create interactive and interesting exercise situations selected according to the interests and objectives of the individual learner. The effectiveness of exercise in VEs on motor recovery has also been linked to the sense of presence reported by the users. Presence refers to the extent to which the experience in the computer-generated environment feels like that in the real world [9]. In terms of virtual environments, this has been interpreted as meaning that the more isolated from the physical environment and the more interactive the environment, the more the individual will feel immersed in or a part of the VE. Both involvement and immersion are necessary for the sense of presence. Virtual environments can have different levels of immersion. The use of 3D stereoscopic visualization assists in providing a first-person immersive experience. 3D environments can be provided with flicker glasses and large screen projection systems or by using a head-mounted visual display (HMD) or cave (BNAVE) system. Another type of immersive system is the video capture system (e.g., IREX), where the user views himself (i.e., third person) or their movements directly or via an avatar on a monitor or screen. Less immersive environments can be created on a desktop computer monitor, using a 2-D graphics display, or a liquid crystal display (LCD) projector and a large wall screen.

Recently, video gaming has been adopted in rehabilitation centers as a new means of exercise delivery in a fun and engaging context. One such system, the Nintendo Wii, requires active arm movements in a variety of game settings. For some games, the clinician can adapt the movement according to the patient’s needs. An advantage of this system over other VR delivery systems is its low cost and ease of use. A disadvantage is that the games are not specifically developed for rehabilitation purposes and thus, do not necessarily focus on rehabilitation goals.

Effect of environment on motivation and sense of presence in healthy subjects performing reaching tasks

Christiane B. Lourenço, Liza Azeff, Heidi Sveistrup and Mindy F. Levin

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In order to evaluate the impact of the training environment on motor recovery in patient groups, it is necessary to first determine whether different environments provide different levels of engagement and motivation to the learner. Thus, the objective of the study was to evaluate motivation and presence in participants performing a reaching task in four different environments. We hypothesized that the motivation to perform reaching movements would be greater in environments that are more immersive and that incorporate more feedback to the user. In addition, since there are no data on the relationship between motivation and age and younger people might have more experience with gaming environments, our second hypothesis was that the level of motivation would vary with age.

II. METHODS

A. Participants Then healthy subjects with previous computer experience were divided into two groups based on age. Group 1 was under 25 years old (aged 13-24 yrs) and Group 2 was over 25 years old (aged 25-38 yrs). All subjects signed informed consent forms approved by the ethics committee of the Center for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR).

B. Protocol Subjects filled in a questionnaire about their previous experience with computers and computer games prior to the session. Then they performed blocks of 20 arm reaching tasks in four different environments presented in a random order: 1) physical (PE), 2) 2D-VR (IREX system), 3) 3D-VR (CAREN system, VE), and 4) video game system (Nintendo Wii, VID; see below for descriptions of environments). The order of environments was determined by a random number generator. The completion of each task in each environment took approximately 15 minutes. After each task, subjects filled in questionnaires rating their level of motivation and presence (if applicable). Finally, they ranked the environments (1 to 4) in terms of the order of preference.

C. Motivation and Presence Questionnaires Motivation: Motivation was measured on the 13-item

version of the Intrinsic Motivation Task Evaluation questionnaire [10]. This questionnaire has three subscales: interest/enjoyment, perceived competence and pressure/tension. The interest/enjoyment subscale is considered the self-report measure of intrinsic motivation while perceived competence and pressure/tension are positively and negatively correlated with intrinsic motivation respectively. Each statement of the questionnaire was scored on a seven-point scale with a midpoint anchor, where 1 is “not at all true”, 4 is “somewhat true” and 7 is “very true”. Subjects were asked to place an “X” in the appropriate box of the scale in accordance with the question content and descriptive labels.

Sense of presence: The sense of presence questionnaire is a 10-item scale based on the Presence Questionnaire [9]. It has five subscales: Control, Sensory, Distraction, Realism and Interest/Enjoyment. The questions on the Control Factor subscale are: Q1: “I felt accustomed to the environment when the experiment started” and Q8: “I felt as though the movement done in the virtual environment were similar to those that I can do in a physical setting”. For the Sensory Factors subscale, the questions were: Q3: “My movements were well represented in the environment” and Q5: “I was able to recognize the sounds while performing the movements”. For the Distraction Factors Subscale, there was one question: Q10: “I was so engaged in trying to successfully complete the task that I was unaware of any activity or distraction that occurred around me”. The Realism Factor subscale had two questions: Q2: “The quality of the images helped me feel as though I was immersed in the environment” and Q4: “I could estimate the distance between myself and the virtual items on the screen”. Finally for the Interest/Enjoyment Subscale, the questions were: Q6: “The activity of performing movements in the virtual environment provides a more pleasant training environment for arm movements” and Q9: “I really enjoyed practicing in the virtual environment and I would like to continue the training”.

D. Reaching task and environments To evaluate the effect of the environment on motivation,

we controlled for confounding factors of arm dominance and the type of movement performed. Thus, all movements were performed by the dominant arm and we selected or created tasks that were as similar to each other as possible. Initial subject positions were also similar. Subjects were seated with the shoulder in slight abduction (20º) and internal rotation, the elbow flexed to 90º and the forearm completely pronated. The hand was held at the level of the sternal xiphoid process. Subjects performed 20 pointing movements in each environment. For PE and 3D-VR, subjects reached towards a numerical target as fast and as accurately as possible. Movement start was indicated by an auditory or visual command and feedback was provided about movement accuracy and speed. In 2D-VR, subjects were instructed to reach to intercept a soccer ball coming towards them and aimed at a goal behind them. In VID, subjects were asked to reach their arm forward to strike a ball on a pool table. For the latter environments, the cue to move was the appearance of the ball on the screen.

E. Environments The PE consisted of a wooden frame on which two rows

of three targets each were suspended (Fig. 1A). Middle targets were aligned with the subject’s sternum at shoulder height so that the targets were located in the ipsilateral, midline and contralateral workspaces. Targets were 6cm x 6cm squares labeled 1 to 6, separated by a center-to-center distance of 26cm. They were placed in front of the seated subject at a standardized distance equal to the length of the outstretched arm to the fingertips. The subject was cued to

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reach to a specific target by a recorded computer voice. If the reach was successful in terms of accuracy and speed (4 s), a ‘ping’ sound was heard. If it was not successful, a buzzer sound was heard.

The 2D-VR was a commercially available system (GestureTek, www.gesturetek.com /irex, Toronto, Fig. 1B) in which subjects sat in front of a green screen and viewed a mirror image of themselves projected onto a large 2m wide x 1.5m screen placed 3′4″ in front of them. Subjects played a soccer game in which they saw themselves as the goalkeeper. The soccer balls came from any part of the right side of the screen towards the subject, whose task was to intercept and deflect the ball from getting into the net. When the ball was ‘touched’ by the hand, a ‘thud’ sound was heard

and the ball was deflected. If the ball was not intercepted, a moan from the crowd was heard and the ball entered the goal. A time index and game score were displayed indicating the number of goals scored against the participant.

The 3D-VR consisted of a 6 target scene similar in dimensions to the PE projected on the large screen at the same distance as for 2D-VR and viewed with flicker glasses to create a stereoscopic effect. The environment was created with the CAREN VR simulation system (Computer Assisted Rehabilitation Environment; Motek BV) and resembled the interior of an elevator with two horizontal rows of buttons (Fig. 1C). This system consists of software permitting the creation of a 3D interactive environment designed for the upper limb [8]. Feedback was identical to that in PE but subjects could also view a game score indicating the number of successful reaches.

The VID was a video game console (Fig. 1D, Nintendo Wii, PowerPC “Broadway”). The system included a Wii remote, a sensor bar using Bluetooth technology, and a CD containing games software. We used a game of pool in which the subject was required to strategize how best to hit a white ball placed on a virtual pool table, with a ‘cue’ and one hand, in order to strike one of the other balls. The game was projected onto the large screen.

F. Kinematic data acquisition analysis Twenty reaching trials were recorded in each

environment. Arm and trunk kinematics were recorded with Optotrak 3010 system (Northern Digital, 120 Hz, Waterloo, Canada). Seven infrared-emitting diodes (IREDs) were

placed on the (1) index, (2) dorsomedial border of the wrist crease, (3) lateral epicondyle, (4,5) ipsilateral and contralateral acromion processes, (6) spinous process of the sixth cervical vertebra, and (7) greater trochanter of femur.

Kinematic outcomes were endpoint trajectories and movement errors, joint angular excursions and trunk displacement. The amplitude of the velocity vector, obtained by numerical differentiation of the x, y and z position of the marker placed on the index finger was used to compute the arm tangential velocity. Movement onset and offset were defined from the tangential velocity trace. Arm trajectory shape was characterized by a length index computed as the ratio of actual 3D path length to the length of an ideal straight line joining the initial and final positions. Movement accuracy was computed as the root mean squared error of the absolute distance between the final endpoint position and

Fig. 1. Similar reaching actions were performed in four environments: A. PE – Physical environment; B. 2D-VR – IREX game environment; C. 3D-VR – 3D scene of 6 targets appearing as elevator buttons; and D. VID – Nintendo Wii pool game environment. Environments B-D were projected onto a large screen.

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target centre. Three joint angles were computed, elbow flexion/extension, shoulder flexion/ extension and shoulder horizontal adduction/ abduction based on the dot product of the vectors formed by pairs of IREDS placed on bony landmarks of the arm and trunk. Anterior trunk displacement was measured as forward displacement (cm) in the sagittal plane of the IRED located on the trunk.

G. Statistical Analysis Both parametric and non-parametric statistics were used.

Differences in eight kinematic outcomes of movements made in different environments were compared using repeated measures ANOVAs with factors group and environment. For questionnaire data (Motivation and Presence), Cronbach’s Alpha coefficient (criterion level 0.70) and Tukey-Kramer post hoc tests were used to verify internal consistency and reliability. Based on the results of this comparison, questions could be combined and expressed as a single score. Since variances for the questionnaire were not homogeneous, non-parametric tests were used (Mixed Model ANOVA). A significance level of p<0.05 was used, adjusted for multiple comparisons by type using the Bonferroni correction.

III. RESULTS

A. Participants

Subjects were 6 males and 4 females in group 1 and 3 males and 7 females in group 2. All participants had previous computer experience with computer applications. Only 3 participants in group 1 reported having previous experience with computer games. Most participants in each group believed themselves to be skilled with computers (50% reported being very good and 50% reported being good for both groups). Ninety percent of participants in each group reported spending more than 10 hours per week using computer applications. For the remaining participant in each group, this amount was 5-10 hours per week.

B. Comparison of movement kinematics across four environments All of the movements involved elbow extension, shoulder

flexion and either shoulder horizontal abduction or adduction depending on the location of the targets. All targets were within reach and did not require trunk rotation and flexion. There were no significant differences in trajectory length, precision, elbow extension or trunk rotation between the four environments. However, movements in VID were faster (F3,54=17.83; p<0.001) and made with more shoulder flexion (F3,54=8.12; p<0.001) and anterior trunk movement (approximately 17 to 29 mm; F3,54 = 7.67; p<0.001). Movements in 2D-VR used less shoulder horizontal adduction (F3,54=8.12; p<0.001) and less shoulder abduction (F3,54=5.960; p<0.001) compared to the other environments.

C. Motivation and Presence Questionnaires The Cronbach alpha showed acceptable internal

consistency for the motivation and presence subscales with values ranging from 0.82-0.91 and from 0.83-0.90 respectively, in all the environments. Thus, individual item scores on each scale were averaged and expressed as mean scores. There were no differences between age groups. Based on results of the Motivation Questionnaire, overall participants rated VID as being the most motivating environment (F3,54=5.06; p<0.05). Subscale analysis indicated that the VID had the highest level of interest/enjoyment (p<0.05) while perceived competence and pressure/tension scores were similar to the other environments. There were no differences between age groups or environments.Although there were no differences in sense of presence between VR environments, the level of presence perceived by the subjects was correlated with their level of motivation. Correlations were made between Question 10 of the Presence Questionnaire: “I was so engaged in trying to successfully complete the task that I was unaware of any activity or distraction that occurred around me” and Question 8:“It was important to me to do well at this task” of the Motivation Questionnaire. For combined group data, significant correlations were found for the 2D-VR (r= 0.66, p < 0.002), 3D-VR (r = 0.44, p < 0.05) and VID-Wii (r = 0.49, p < 0.03) environments. Correlations were stronger in the older group of subjects (Group 2: 2D-VR: r = 0.67, p < 0.04; 3D-VR: r = 0.68, p < 0.04; and VID: r = 0.81, p < 0.004) environments whereas for the younger group (Group 1), there was only a correlation between sense of presence and motivation for the 2D-VR environment (r = 0.90; p < 0.001, Fig. 2).

D. Preferred Environment Ninety percent of Group 1 participants and 60% of Group

2 participants stated that their preferred environment was VID. The second most preferred environment for the younger group (Group 1) was the 3D-VR (40%) while for the older group (Group 2), the 3D-VR and 2D-VR environments were chosen with the same frequency (30%).

IV. DISCUSSION Kinematic comparisons showed that movements were

similar for most of the parameters studied. Differences were observed however because of particular demands of the tasks in the VID and 2D-VR environments. In the VID environment, in order to successfully cause the virtual pool ball to interact with the other balls on the virtual table, the subject had to use a high arm acceleration which accounted for the higher endpoint velocity and trunk movement. In the 2D-VR, all of the soccer balls originated from the same part of the virtual soccer field which was in front of the subject’s arm. Thus, the demands of the task did not require subjects to move their arm into the ipsilateral or contralateral workspaces and consequently, they used less shoulder horizontal abduction/adduction compared to the other environment. Aside from these differences, movements did not differ in terms of endpoint straightness and precision,

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elbow extension and trunk movements suggesting that the subjects were comparing similar movement experiences in each of the four environments.

VID was the most motivating and the most preferred environment for both groups of subjects. As in the other environments, VID required that the user develop a strategy or plan in order to successfully interact with the environment. One explanation for the preference of this environment could be that the VID was initially created to provide entertainment and therefore has a more interesting visual and auditory interface than the other environments.

Healthy adolescents and young adults were easily able to interact with this environment that required a high level of motor functioning and contained visual and auditory distracters. Although potentially providing a more motivating environment for motor rehabilitation than traditional therapeutic situations, it is necessary to assess if interaction in such environments will meet clinical needs and be rewarding for patients who are older or have neurological and/or cognitive deficits. Movement re-education is aimed at recovery of lost or deficient movement patterns of the affected limb via guided and graded exercise. Although current video game software may be used to encourage global movement, since the parameters of the environment are not programmable, unguided activities in gaming environments may encourage movements that are compensatory or unwanted.

All subjects felt a high sense of presence in all environments, with no differences between environments. The sense of presence is related to the individual’s ability to isolate himself from the physical environment and interact in a meaningful way with the virtual one. Our results suggest

that subjects felt comparable levels of presence in each of the environments suggesting that presence was not related to how real the virtual task may have appeared (i.e., playing virtual pool or reaching for elevator buttons). We also found a correlation between motivation and presence in the whole group of subjects. Individual group analysis showed that presence and motivation were linked only in the 2D-VR environment for the younger group while it was linked in all three of the virtual environments for the older group. This might suggest that feeling a sense of presence in the environment may be more important to motivate older

individuals compared to younger ones. The level of presence and degree of motivation generated following extended use may also differ as a function of environment and is yet to be determined.

The second most preferred environment was the 3D-VR for the younger group and the 2D-VR for the older group. The 2D-VR environment is similar to a virtual reality gaming device which was specifically developed for rehabilitation applications. It has a variety of games that can be used to address training objectives such as improving balance, gait, limb coordination, range of motion, strength, etc. One important feature is that activities can be chosen to increase joint ranges and or movement speed according to individual rehabilitation goals. The 3D-VR system was also developed for rehabilitation. It is a fully programmable system and our application was specifically designed to retrain upper limb coordination during reaching tasks. The program incorporates elements important to optimize motor learning such as enhanced extrinsic feedback (KR and KP). These environments were found to be less motivating than the VID-Wii in our groups of healthy subjects. This may be

Fig. 2. Correlations between Question 10 of the Presence Questionnaire and Question 8 of the Motivation Questionnaire in different environments and

groups.

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due to the fact that these environments have a less cluttered interface and require more simple movements, as is necessary for rehabilitation applications. Interestingly, both groups preferred the virtual and gaming environments to the physical one. Of note, is that the task in 3D-VR and PE were exactly the same except that when performed in the context of a VR environment, the same reaching task was rated as being more motivating. Overall, our results suggest that rehabilitation exercises performed in virtual environments are more motivating for the subject which may lead to better rehabilitation outcomes. This is the subject of a research program currently underway in patients with stroke-related arm paresis.

V. CONCLUSION The VID system was considered to be the most motivating

and preferred environment for arm reaching tasks. However, in order to apply this system as a rehabilitation tool, further research with different patient groups is needed. In addition, specific applications should be created to adapt the system to address rehabilitation goals and that allow clinicians to manipulate variables and to adapt the environment and game situations according to patient’s needs.

ACKNOWLEDGMENT Thanks are extended to Leah Feldman, Daniel Wolf,

Rachel Kizony and study participants as well as to Christian

Beaudoin and Valeri Goussev for technical support.

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