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Hand Sensorimotor Function in Older Children with Neonatal Brachial Plexus Palsy
Pediatric Neurology

Abstract: Routine sensory assessments in neonatal brachial plexus palsy are infrequently performed because it is generally assumed that sensory recovery exceeds motor recovery. However, studies examining sensory function in neonatal brachial plexus palsy have produced equivocal findings. The purpose of this study was to examine hand sensorimotor function in older children with neonatal brachial plexus palsyusing standard clinical and research-based measures of tactile sensibility. Seventeen children with neonatal brachial plexus palsy (mean age: 11.6 years) and 19 age-matched controls participated in the study. Functional assessments included grip force monofilament testing, and hand dexterity (Nine-Hole Peg, Jebsen-Taylor Hand Function). Tactile spatial perception involving the discrimination of pin patterns and movement-enhanced object recognition (stereognosis) were also assessed. In the neonatal brachial plexus palsy group, significant deficits in the affected hand motor function were observed compared with the unaffected hand. Median monofilament scores were considered normal for both hands. In contrast, tactile spatial perception was impaired in theneonatal brachial plexus palsy group. This impairment was seen as deficits in both pin pattern and object recognition accuracy as well as the amount of time required to identify patterns and objects. Tactile pattern discrimination time significantly correlated with performance on both functional assessment tests (P < 0.01). This study provides evidence that tactile perception deficits may accompany motor deficits in neonatal brachial plexus palsy even when measures of tactile registration (i.e.., monofilament testing) are normal. These results may reflect impaired processing of somatosensory feedback associated with reductions in goal-oriented upper limb use and illustrate the importance of including a broader range of sensory assessments in neonatal brachial plexus palsy. 

Authors: Brown SH, Wernimont CW, Phillips L, Kern KL, Nelson VS, Yang LJ


DOI: 10.1016/j.pediatrneurol.2015.12.012.


Home-based Movement Therapy in Neonatal Brachial Plexus Palsy
Journal of Hand Therapy

Abstract: The value of movement-based therapy in peripheral nerve injury conditions such as neonatal brachial plexus palsy (NBPP) is unclear. The purpose of this study was to determinethe effectiveness of a home based movement therapy program in a 17 year old female patient with a right NBPP pan-plexopathyHome training consisted of arm reaching and object manipulation tasks using devices which recorded performance. Training occurred for 1 h/day, 5 days/week for 6 weeks with periodic webcam supervision. Pre- and post clinical, functional and kinematic assessments were performed in a laboratory setting. Following training, shoulder flexion and elbow extension active range of motion increased by 13° and 9°, respectively, and functional ability also improved. Reach movement duration decreased significantly with a concomitant improvement in movement coordination. These results demonstrate that movement therapy has the potential to improve motor function in NBPP years after the initial insult.

Authors: Brown SH Napier RNelson VSYang LJ.


DOI: 10.1016/j.jht.2014.10.004

Effects of Task Context During Standing Reach on Postural Control in Young and Older Adults
Gait and Posture

Abstract:  Reaching is an important component of daily activities with goals to interact and acquire objects in the environment. The task context of reaching, as determined by the behavioral goal and the properties of the object, can influence the control of posture and movements. This study examined age differences in postural stability during a forward reach under two task contexts, grasping versus pointing to a target. Young and olderparticipants living in the community performed the tasks from the standing position. They reached forward, grasped or pointed to a target, and then returned to an upright posture as fast as possible. Postural stability was analyzed using the center of pressure (COP) during two phases of the task: the reaching movement phase and the returning movement phase. In the grasping context, the COP path deviations were significantly larger in older compare to young participants during both the reach and the return movement phases. In addition, during the return movement phase, only older participants showed a context-dependent increase in COP path deviations after grasping compared to pointing. The results highlight the impact of task context on postural stability during standing reach in young and older adults. Interventions for older adults with balance problems should consider incorporating activities that involve the interaction with objects of various properties in the environment. Future studies are necessary to investigate the factors underlying the person-environment interplay of postural control and the adaptation of anticipatorypostural control associated with object interaction during functional tasks in older adults.

Authors: Huang MH, Brown SH


 DOI: 10.1016/j.gaitpost.2014.10.018


Proprioceptively Guided Reaching Movements in 3D Space: Effects of Age, Task Complexity and Handedness
Journal of Experimental Brain Research

Abstract: Aging is associated with impaired upper limb proprioceptive acuity, as reflected by decreased position matching accuracy with increasing task complexity and movement extent. Most studies have primarily used single-joint or planar paradigms to examine age-related changes in proprioception. It is unclear whether these changes can be generalized to more complex multi-joint movements, where additional sensory feedback may affect performance. Since age-related declines in cognitive function may impair the ability to integrate multiple sources of sensory feedback, deficits in position matching ability in older adults may persist when tasks are performed in three-dimensional space. The accuracy with which young and older participants reproduced remembered reference hand positions was assessed under different experimental conditions. Participants matched target locations located directly to the front or 45° to the side relative to the midline using the preferred and non-preferred arms. Either the same (i.e., ipsilateral matching) or the opposite (i.e., contralateral matching) arm was used to reproduce the target location. No differences in matching accuracy were found between young and older participants when matching ipsilaterally. When matching contralaterally, accuracy was worse in older participants for target locations located to the side, which may reflect age-related changes in the perception of peripersonal space. In contrast to previous studies, accuracy did not differ between the preferred and non-preferred arms in either group. These results extend previous findings demonstrating age-related impairments in proprioceptively guided arm movements when interhemispheric transfer is required.

Authors: Schaap TS, Gonzales TI**, Janssen TWJ, Brown SH


DOI: 10.1007/s00221-014-4142-3

Upper-Limb Position Sense Deficits in Adults with Cerebral Palsy 
American Journal of Physical Medicine Rehabilitation

Abstract: The aim of this study was to examine proprioceptive performance in adults with hemiplegic cerebral palsy and the possibility that a home-based sensorimotor training program could improve proprioceptive performance.

Design: This study is a preintervention/postintervention assessment of 12 adults participating in a home-based program consisting of targeted unilateral and bilateral reaching movements, hand manipulation tasks, tactile discrimination, and stereognosis. It did not specifically include proprioceptive tasks. Training sessions were 45 mins, 5 days per week, for 8 wks. Limb position sense was assessed using three conditions: ipsilateral remembered (same arm used for reference and matching targets), contralateral concurrent (reference arm moved and held at target position while opposite arm matched reference position), and contralateral remembered (reference arm moved to target position and then returned to start position before opposite arm matching position).

Results: The participants demonstrated greater absolute and constant error when the more affected arm served as the reference arm, and matching was performed by the less affected arm, particularly in the contralateral remembered condition. After training, the participants demonstrated less absolute error across matching tasks and no change in constant error.

Conclusions: The results suggest an important role for the reference arm in bilateral position matching tasks and the potential for improved proprioceptive performance after training in movement and unrelated sensory tasks.

Authors: Langan J, Kern KL, Hurvitz EA, Brown SH

DOI: 10.1097/PHM.0000000000000100


Deficits in Elbow Position Sense in Neonatal Brachial Plexus Palsy 
Journal of Pediatric Neurology

Abstract: In neonatal brachial plexus palsy, sensory recovery is thought to exceed motor recovery with little attention paid to long-term assessment of proprioceptive ability. However, there is growing evidence that reduced somatosensory function frequently accompanies motor deficits as a result of activity-dependent changes in the central nervous system. Given the importance of proprioception in everyday motor activities, this study was designed to investigate position sense about the elbow joint in neonatal brachial plexus palsy.

A convenience sample of seven individuals with neonatal brachial plexus palsy aged 9-17 years and in seven control individuals aged 10-16 years were recruited for the study. An elbow position matching task was used in which passive displacement of the forearm (reference arm) was reproduced with the same or opposite arm. In both conditions, matching was performed in the absence of vision and required utilization of position-related proprioceptive feedback.

Position-matching errors were significantly greater for the affected versus the unaffected arm when reproducing a reference position with the same arm. When matching was performed using the opposite arm, errors were dependent upon which arm served as the reference arm. When the unaffected arm served as the reference position, affected arm matching errors were not significantly different from control values. However, in the reverse situation, in which the unaffected arm relied on reference feedback from the affected arm, matching errors doubled compared with control values.

These results provide evidence that position sense is impaired in neonatal brachial plexus palsy and illustrate the importance of assessing proprioception in this population.

Authors: Brown SH, Noble BC*, Yang L, Nelson VS

DOI: 10.1016/j.pediatrneurol.2013.07.018

Age Difference in the Control of Postural Stability During Reaching Tasks 
Journal of Gait and Posture

Abstract: Reaching tasks are commonly performed during daily activities and require anticipatory postural adjustments (APAs) to ensure a stable posture during movement execution. Age-related changes in APAs may impact dynamic balance and cause postural instability during reaching tasks made from standing. The present study examined age differences in postural control during reaching to targets located at different heights. Fourteen young adults (aged 20.0 ± 1.5 yrs) and 16 community-dwelling older adults (aged 73.4 ± 5.3 yrs) participated in the study. The task involved reaching forward to grasp a cylinder, and returning to an upright position as fast and accurately as possible. Postural control was analyzed using the center of pressure (COP) during four phases of the task: COP displacement during APA production, COP trajectory smoothness during the reach and return phases, and COP path length during the recovery phase following movement. APA amplitude measured by COP displacement and COP path length during the recovery phase was larger in older compared to young adults. Dynamic balance represented by COP trajectory smoothness was reduced with age. In both age groups, APA amplitude was largest and COP trajectory smoothness the least during low target reaches.

The results demonstrate that, while older adults can alter APAs in order to maintain postural stability, control of COP during movement execution, particularly during low target reaches, is compromised with aging. These findings have clinical implications for both the assessment of dynamic balance and the development of balance training programs.

Authors: Huang M**, Brown SH

DOI: 10.1016/j.gaitpost.2013.04.004

Home-Based Telerehabilitation Shows to Improved Upper Limb Function in Adults with Chronic Stroke: A Pilot Study 
Journal of Rehabilitation Medicine

Abstract: This pilot study investigates the use of telerehabilitation to improve upper limb performance in chronic stages of stroke recovery. 
DESIGN: Intervention study with pre/post/one month follow-up tests.
METHODS: Seven adults with chronic stroke participated in the study. Tests consisted of lab-based clinical and kinematic assessments. Participants completed the Upper Limb Training and Assessment (ULTrA) program at home. Training was 5 days/week, 60 min/day for 6 weeks with intermittent supervision of participants. 
RESULTS: Participants showed improvements in the training program tasks as well as clinical and kinematic assessments. Results also suggest there may be auxiliary benefits in cognitive function.
Conclusions: A home-based telerehabilitation program is a viable approach to provide rehabilitation in chronic stages of stroke.

Authors: Langan J, DeLave K*, Phillips L*, Pangilinan P, Brown SH

DOI: 10.2340/16501977-1115


Compromised Encoding of Proprioceptively Determined Joint Angles in Older Adults: The Role of Working Memory and Attentional Load 
 Journal of Experimental Brain Research

Abstract: Perceiving the positions and movements of one's body segments (i.e., proprioception) is critical for movement control. However, this ability declines with older age as has been demonstrated by joint angle matching paradigms in the absence of vision. The aim of the present study was to explore the extent to which reduced working memory and attentional load influence older adult proprioceptive matching performance. Older adults with relatively HIGH versus LOW working memory ability as determined by backward digit span and healthy younger adults, performed memory-based elbow position matching with and without attentional load (i.e., counting by 3 s) during target position encoding. Even without attentional load, older adults with LOW digit spans (i.e., 4 digits or less) had larger matching errors than younger adults. Further, LOW older adults made significantly greater errors when attentional loads were present during proprioceptive target encoding as compared to both younger and older adults with HIGH digit span scores (i.e., 5 digits or greater). These results extend previous position matching results that suggested greater errors in older adults were due to degraded input signals from peripheral mechanoreceptors. Specifically, the present work highlights the role cognitive factors play in the assessment of older adult proprioceptive acuity using memory-based matching paradigms. Older adults with LOW working memory appear prone to compromised proprioceptive encoding, especially when secondary cognitive tasks must be concurrently executed. This may ultimately result in poorer performance on various activities of daily living.

Authors: Goble DJ**, Mousigian M*, Brown SH

DOI: 10.1007/s00221-011-2904-8


Age-Related Declines in the Detection of Passive Wrist Movement 
Journal Neuroscience Letters

Abstract: Age-related changes in proprioceptive ability and their contributions to postural instability have been well documented. In contrast, and despite the known importance of proprioceptive feedback in the control of coordinated arm and hand movement, studies focusing on upper limb proprioception in older populations are few and equivocal in their findings. This study focused on kinesthetic awareness about the wrist joint in healthy young and older adults. Passive movement detection thresholds (PMDTs) were twice as high in older compared to young participants. In contrast to previous findings demonstrating asymmetries in static position sense, PMDT did not differ between the dominant and non-dominant wrist joints nor did direction of joint displacement affect PMDT as has been reported for the lower limb. Preliminary analysis indicated that PMDT was significantly higher in older adults categorized as sedentary while active older adults were able to detect passive movement as well as young adults. These findings demonstrate that upper limb kinesthesia is impaired in older adults although the degree of impairment may be influenced by one's level of physical activity.

Authors: Wright ML**, Adamo DE, Brown SH

DOI: 10.1016/j.neulet.2011.06.015

Remote Monitoring and Quantification of Upper Limb and Hand Function in Chronic Disability Conditions 
International Journal on Disability and Human Development

Abstract: This paper describes a convenient, home-based telerehabilitation system designed to improve upper limb and hand function in adults with cerebral palsy. The training program incorporates a variety of computer-guided sensorimotor activities, such as unilateral and bilateral reaching, reaching and grasping, object manipulation, and tactile discrimination tasks. Quantitative measures of performance are uploaded to the laboratory after each training session for further analysis. Webcam monitoring of performance occurs periodically throughout the training period. Twelve adults with cerebral palsy completed a 45 min/day, 5 days/week training program over 8 weeks. Temporal measures of performance indicated significant improvement in reaching and hand manipulation ability as well as improved tactile discrimination. Preliminary analysis of the time course of change revealed variable patterns within and across participants. The capacity to measure change throughout a training program provides an opportunity to investigate how learning occurs over time in chronic disability. Compliance was excellent, with subjective reports indicating improvement in activities of daily living. Future development includes a fully automated system with stand alone modules, which allow for customization of training protocols depending upon specific needs of the user.

Authors: Brown SH, Langan J, Kern KL, Hurvitz EA

DOI: 10.1515/IJDHD.2011.064


Influence of Task on Interlimb Coordination in Adults with Cerebral Palsy
Archives of Physical Medicine and Rehabilitation

Abstract: To examine movement time and kinematic properties of unilateral and bilateral reaching movements in adults with cerebral palsy (CP), focusing on how different types of bilateral movements, simultaneous or sequential, may influence interlimb coordination.

Quantitative study using between-group repeated-measures analyses.

Motor control laboratory at a research university.

Adults with hemiplegic CP (n=11; mean age ± SD, 33±10y; 4 men) and age-matched controls (mean age ± SD, 32±9y; 4 men).

Not applicable.

Main Outcome Measures
Movement time (MT), maximum deviation from a straight trajectory to the target, and peak speed.

Although adults with hemiplegic CP showed strong unilateral deficits, bilateral simultaneous reaching movements were temporally and spatially coupled. Movement of the less affected arm slowed to match the movement of the more affected arm. In contrast, bilateral sequential movements improved MTs of the less affected and more affected arms.

Bilateral sequential movements were conducive to faster MT compared with unilateral or bilateral simultaneous movements. Training that includes bilateral sequential movements may be beneficial to adults with hemiplegic CP. Upper-limb movements are coordinated in a variety of ways to perform routine bilateral tasks. Some bilateral tasks, such as stacking boxes, require more symmetric movements of the upper limbs. Other bilateral tasks, such as opening the refrigerator with 1 hand while placing an item on the shelf with the other hand, emphasize coordinated sequential action between upper limbs. Despite the prevalence of integrative upper-limb use, the control of different forms of bilateral movement is not well understood. A more comprehensive knowledge of upper-limb bilateral movements may hold important implications for developing more effective upper-limb movement therapies.

Authors: Langan J, Doyle ST*, Hurvitz EA, Brown SH

DOI: 10.1016/j.apmr.2010.07.015

Where was my Arm Again? Memory-Based Matching of Proprioceptive Targets is Enhanced by Increasing Target Presentation Time 
Neuroscience Letters

Abstract: Our sense of proprioception is vital for the successful performance of most activities of daily living, and memory-based joint position matching (JPM) tasks are often utilized to quantify such proprioceptive abilities. In the present study we sought to determine if matching a remembered proprioceptive target angle was influenced significantly by the length of time given to develop a neural representation of that position. Thirteen healthy adult subjects performed active matching of passively determined elbow joint angles (amplitude = 20 degrees or 40 degrees extension) in the absence of vision, with either a relatively "short" (3 s) or "long" (12 s) target presentation time. In the long condition, where subjects had a greater opportunity to develop an internal representation of the target elbow joint angle, matching movements had significantly smaller variable errors and were associated with smoother matching movement trajectories of a shorter overall duration. Taken together, these findings provide an important proprioceptive corollary for previous results obtained in studies of visually-guided reaching suggesting that increased exposure to target sensory stimuli can improve the accuracy of matching performance. Further, these results appear to be of particular importance with respect to the estimation of proprioceptive function in individuals with disability, who typically have increased noise in their proprioceptive systems.

Authors: Goble DJ**, Noble BC*, Brown SH

DOI: 10.1016/j.neulet.2010.06.053

Upper Limb Asymmetries in the Perception of Proprioveptively Determined Dynamic Position Sense
Journal of Experimental Psychology: Human Perception and Performance

Abstract: Recent studies of position-related proprioceptive sense have provided evidence of a nonpreferred left arm advantage in right-handed individuals. The present study sought to determine whether similar asymmetries might exist in "dynamic position" sense. Thirteen healthy, right-handed adults were blindfolded and seated with arms placed on instrumented manipulanda. In Part 1, subjects performed dynamic position matching of 3 target elbow amplitudes determined with the preferred or nonpreferred arm, and then matched during movement of the same or opposite elbow. In Part 2, a similar paradigm was used, but with varying target determination speeds to account for the so called "tau effect." Overall, it was found that errors were smaller when the matching phase involved the nonpreferred arm, especially for larger target amplitudes. This asymmetry was independent of the tau effect and likely reflects specialization of the right hemisphere/left arm for proprioceptive feedback processing that is either position- or dynamic position-related.

Authors: Goble DJ**, Brown SH


DOI: 10.1037/a0018392

The Effects of Internet-Based Home Training on Upper Limb Function in Adults with Cerebral Palsy 
Journal of Neurorehabilitation and Neural Repair

Abstract: While adults with hemiplegic cerebral palsy (CP) can have significant upper limb dysfunction, the effects of movement-based training has not been investigated. Objective: This uncontrolled trial assessed the effects of a home and internet-based upper limb intervention program targeting motor and sensory function. 

Methods: Twelve adults, aged 21 to 57 yrs, GMFCS levels I-III with asymmetric upper limb involvement participated in the Upper Limb Training and Assessment (ULTrA) program. Clinical and functional measures included the Motor Activity Log (MAL), the Nine-Hole Peg test, and grip strength. An upper limb training system consisting of a laptop, webcam, target light board, and hand manipulation/ discrimination devices was installed in each participant’s home. Training occurred 40 min/day, 5 days/wk for 8 wks and included both unilateral and bilateral reach movements as well as a series of hand sensorimotor tasks such as card turning, stereognosis, and tactile discrimination. Data generated during each session were transmitted to the laboratory via the Internet. Main outcome measures were movement time, interlimb delay time, and performance on hand sensorimotor tasks. 

Results: Following training, affected limb reach movement time decreased significantly for unilateral and bilateral tasks. Interlimb delay during sequential reaching also decreased. Significant improvement in hand manipulation tasks was also seen. Compliance was excellent and there were no adverse effects. Conclusion: The ULTrA program had beneficial effects for adults with CP and is safe and convenient to use. This system contrasts sharply with programs with similar intent that require participant travel and hours of therapist-based intervention.

Authors: Brown SH, Lewis CA, McCarthy JM*, Doyle ST*, Hurvitz EA

DOI: 10.1177/1545968310361956

Timing and the Control of Rhythmic Upper-Arm Movements 
Journal of Motor Behavior

Abstract: Accurate timing of limb displacement is crucial for effective motor control. The authors examined the effects of movement velocity, duration, direction, added mass, and auditory cueing on timing, spatial, and trajectory variability of single- and multijoint rhythmic movements. During single-joint movements, increased velocity decreased timing and spatial variability, whereas increased movement duration increased timing variability but decreased spatial variability. For multijoint movements, regardless of condition, increasing velocity decreased joint timing, spatial, and trajectory variability, but all hand variabilities were unaffected by velocity, duration, load, or direction. Timing, spatial, and trajectory variability was greater at the shoulder compared with the elbow and minimal at the hand, supporting the notion that reaching movements are planned in hand space as opposed to joint space.

Authors: Shafir T**, Brown SH

DOI: 10.1080/00222890903397137


Proprioceptive Target Matching Asymmetries in Left-Handed Individuals 
Journal of Experimental Brain Research

Abstract: In right-handers, the ability to reproduce proprioceptive targets has been shown to be asymmetric, favoring the non-preferred left arm. The present study sought to determine whether a similar arm/hemisphere asymmetry exists for left-handers. Ten strong left-handed adults used the left or right arm to perform proprioceptive target matching tasks that varied in processing demands (i.e., need for memory, interhemispheric transfer) and target amplitude (20, 40°). Similar to right-handers, left-handed individuals had smaller total errors when matching with the non-preferred arm. This asymmetry was greatest in conditions with increased processing demands and larger amplitude targets. These results provide the first evidence to date of right arm/left hemisphere dominance for proprioceptive target matching in left-handers that is the “mirror image” of right-handers.

Authors: Goble DJ**, Noble BC*, Brown SH

DOI: 10.1007/s00221-009-1922-2

Deficits in the Ability to Use Proprioceptive Feedback in Children with Hemiplegic Cerebral Palsy 
International Journal of Rehabilitation Research

Abstract: Compared with motor impairment in children with hemiplegic cerebral palsy (CP), less attention has been paid to sensory feedback processing deficits. This includes, especially, proprioceptive information regarding arm position. This study examined the ability of children with hemiplegic CP to use proprioceptive feedback during a goal-directed target-matching task. Eight children with hemiplegic CP and eight typically developing children performed proprioceptively guided matching of elbow position with either arm. Between groups, it was found that matching errors were significantly greater for the affected arm of children with hemiplegic CP. With respect to the side of brain injury, deficits were only seen for children with right hemisphere damage. These results provide valuable information that may assist in the development of more effective sensorimotor rehabilitation and training paradigms.

Authors: Goble, DJ**, Hurvitz EA, Brown SH

DOI: 10.1097/MRR.0b013e32832a62d5

The Influence of Age and Physical Activity on Upper Limb Proprioceptive Ability 
Journal of Aging and Physical Activity

Abstract: Our understanding of age-related declines in upper limb proprioceptive abilities is limited. Furthermore, the extent to which physical activity might ameliorate age-related changes in proprioception is not known. Upper limb proprioceptive acuity was examined in young and older (active and sedentary) right-handed adults using a wrist-position-matching task that varied in terms of processing demands. Older individuals were also classified according to their participation in tasks specific to the upper limb. Errors were greater for older than younger individuals. Older sedentary adults showed greater errors and performed movements less smoothly than older active adults. The nonspecific group showed greater errors and longer movement times than the upper-limb-specific group. In older adults, decreased ability to perceive limb position may be related to a sedentary lifestyle and declines associated with memory and transfer of proprioceptive information. Performing tasks specific to the upper limbs may reduce age-related declines in proprioception.

Authors: Adamo DA**, Alexander NB, Brown SH


Dynamic Proprioceptive Target Matching Behavior in the Upper Limb: Effects of Speed, Task Difficulty and Arm/Hemisphere Asymmetries 
Journal of Behavioral Brain Research

Abstract: Although proprioception consists of static (i.e. position) and dynamic (i.e. movement) components, most studies regarding the matching of proprioceptive targets have focused only on position. Further, these position-matching studies have recently indicated that proprioceptive ability is influenced by several factors including task difficulty and arm preference. The purpose of the present study, therefore, was to quantify the matching of dynamic proprioceptive target arm movements under different matching conditions. Using torque motor-driven manipulanda, 11 blindfolded, right-handed adults experienced triangular velocity profiles at 2 different peak speeds (30 degrees /s or 60 degrees /s) with the preferred and non-preferred elbow. Subjects then matched the dynamics of these target movements with either the same (ipsilateral remembered) or opposite (contralateral remembered) elbow. Matching errors were generally larger for the more difficult, contralateral remembered versus ipsilateral remembered task, and for greater target speed conditions. One arm difference was found indicating a non-preferred arm advantage for the matching of average target acceleration in the ipsilateral remembered condition. Overall, these results demonstrate that dynamic proprioceptive feedback-matching performance is influenced by several factors including peak speed, task difficulty and limb preference.

Authors: Goble DJ**, Brown SH

DOI: 10.1016/j.bbr.2008.11.034


Upper Limb Asymmetries in the Matching of Proprioceptive Versus Visual Targets 
Journal of Neurophysiology

Abstract: The purpose of the current study was to determine the extent to which “sensory dominance” exists in right-handers with respect to the utilization of proprioceptive versus visual feedback. Thirteen right-handed adults performed two target-matching tasks using instrumented manipulanda. In the proprioceptive matching task, the left or right elbow of blindfolded subjects was passively extended by a torque motor system to a target position and held for 3 s before being returned to the start position. The target angle was then matched with either the ipsilateral or contralateral arm. In the second task, visual matching, circular targets were briefly projected to either side of a visual fixation point located in front of the subject. Subjects then matched the target positions with a laser pointer by moving either the ipsilateral or contralateral arm. Overall, marked arm differences in accuracy were seen based on the type of sensory feedback used for target presentation. For the proprioceptive matching task errors were smaller for the nonpreferred left arm, whereas during the visual matching task smaller errors were found for the preferred right arm. These results suggest a left arm/right hemisphere advantage for proprioceptive feedback processing and a right arm/left hemisphere advantage for visual information processing. Such asymmetries may reflect fundamental differences between the two arm/hemisphere systems during the performance of bimanual tasks where the preferred arm requires visual guidance to manipulate an object, whereas the nonpreferred stabilizes that object on the basis of proprioceptive feedback.

Authors: Goble DJ**, Brown SH

DOI: 10.1152/jn.90259.2008

The Biological and Behavioral Basis of Upper Limb Asymmetries in Sensorimotor Performance 
Neuroscience and Biobehavioral Reviews

Abstract: Asymmetries in upper limb performance are a fundamental aspect of human behavior. This phenomenon, commonly known as handedness, has inspired a great deal of research over the course of the past century garnering interest across a multitude of scientific domains. In the present paper, a thorough review of this literature is provided focusing on the current state of knowledge regarding neuro-anatomical and behavior-based arm asymmetries. It is hoped that this information will provide a basis for new insights regarding the design and implementation of future studies regarding arm laterality.

Authors: Goble DJ**, Brown SH

DOI: 10.1016/j.neubiorev.2007.10.006

*denotes undergraduate student researcher

**denotes current or former graduate student