Biomedical subjects

Andrew M Gordon

Publications and source records attributed to Andrew M Gordon.

At least 19 recordsLinked to original sources

PubMed2006

Fingertip force planning during grasp is disrupted by impaired sensorimotor integration in children with hemiplegic cerebral palsy.

In the present study we examine the ability of children with hemiplegic cerebral palsy (CP) to use anticipatory control of fingertip forces during grasping, and whether anticipatory control is facilitated by lifts with the contralateral hand. Eight children with CP (age 4-13) were asked to perform several lifts of either a 250-g or 500-g object instrumented with force transducers with one hand, followed immediately by several lifts with the contralateral hand. This was repeated for each combination of weight and starting (involved or non-involved) hand. Similar to previous studies, the rate of load force development showed impaired anticipatory control during lifts with the involved hand, intact anticipatory control in the non-involved hand, and transfer of anticipatory control from the non-involved to the involved hand. Surprisingly, however, we also found a transfer from the involved hand to the non-involved hand. The results suggest that the impaired anticipatory control in the involved hand is not purely a sensory or motor problem, and instead is due to an inability to appropriately integrate sensory information with subsequent motor output of the same hand. These results provide important information about the mechanisms underlying impaired anticipatory control, and may have important clinical implications.

Adolescent↗

PubMed2006

Impaired anticipatory control of fingertip forces in patients with a pure motor or sensorimotor lacunar syndrome.

We examined planning and execution of precision grasp in eight right-handed patients with a right pure motor or sensorimotor lacunar syndrome after a subcortical stroke and eight age-matched controls as they grasped and lifted an instrumented object whose weight could be varied without altering its visual appearance. Grip (normal) and load (tangential) forces at the fingertip-object interface were measured and the grip force rate (GFR) and load force rate (LFR) were derived. Planning of precision grasp was assessed by measurement of anticipatory scaling of peak GFR and peak LFR to object weight. Execution of precision grasp was assessed by measurement of both the timing and efficiency of grip-load force coordination: the pre-load phase duration (PLD) and the load phase duration (LPD) measured timing, whereas the grip force at load force onset (GFO) and the grip force at lift-off (GFL) measured efficiency. Subjects lifted a light and heavy object five times first with the RIGHT hand, then with the LEFT hand, and then once more with the RIGHT AFTER LEFT hand. Patients with stroke did not scale the peak LFR or peak GFR to object weight with the RIGHT hand even with repeated attempts; however, they scaled the peak LFR to object weight on the first lift with the RIGHT AFTER LEFT hand (P = 0.01). Patients also prolonged the PLD and LPD and produced excessive GFO and GFL for RIGHT hand lifts, but decreased the GFL for the heavy object (P = 0.016) with the RIGHT AFTER LEFT hand. Correlation of precision grasp variables from lifts with the RIGHT hand with clinical measures showed that anticipatory scaling of peak LFR and peak GFR did not correlate with clinical measures of hand function, whereas the PLD did (r = 0.88, P = 0.004). The results suggest that patients with right hemiparesis from a subcortical lesion of the corticospinal tract have a higher-order motor planning deficit. This planning deficit is dissociable from deficits in motor execution, is not captured by routine clinical assessment, and is correctable by transfer of information from the unaffected hemisphere. A rehabilitation strategy that involves practice with the left hand prior to practice with the right hand may improve planning of grasping behaviour in patients with right hemiparesis.

Adult↗

PubMed2006

Effect of object transport on grasp coordination in multiple system atrophy.

We examined the effects of the parkinsonian variant of multiple-system atrophy (MSA-P) on grasp and forward transport and release of an object. Twelve patients with MSA-P and 10 age-matched control subjects performed the task with each of three object weights (200, 400, 800 gm). Subjects moved at a self-selected pace using a precision grip. The grip (normal) and load (tangential) forces and the object position were recorded. Results indicate subjects with MSA-P have temporal and force coordination deficits. Temporal delays were seen in all subjects with MSA-P, leading to prolonged overall movement times compared to control subjects. These delays occurred throughout the task, with significantly longer transport phases and delays releasing the object. Despite demonstrating an appropriate anticipatory scaling of forces, with increasing grip and load forces for heavier weights, force coordination was compromised in subjects with MSA-P. These subjects generated significant negative load forces prior to transporting the object. In addition, during the transport phase, subjects with MSA-P generated highly variable grip forces. Overall, the results indicate that subjects with MSA-P demonstrate bradykinesia and difficulty coordinating components of an object transport task.

Aged↗

PubMed2006

Efficacy of a child-friendly form of constraint-induced movement therapy in hemiplegic cerebral palsy: a randomized control trial.

Constraint-induced (CI) movement therapy is a promising therapy for improving upper limb function in adults after stroke. It involves restraint of the non-involved limb and extensive movement practice with the involved limb. In this study, a single-blinded, randomized, control study was performed to examine the efficacy of CI therapy, modified to be child friendly, in children with hemiplegic cerebral palsy (CP). Twenty-two children (8 females, 14 males; mean age 6 y 8 mo [SD 1 y 4 mo]; range 4-8 y) were randomized to either an intervention group (n=11) or a delayed treatment control group (n=11). Children wore a sling on their non-involved upper limb for 6 hours per day for 10 out of 12 consecutive days and were engaged in play and functional activities. Children in the treatment group demonstrated improved movement efficiency and dexterity of the involved upper extremity, which were sustained through the 6-month evaluation period, as measured by the Jebsen-Taylor Test of Hand Function and fine motor-subtests of the Bruininks-Oseretsky Test of Motor Proficiency (p<0.05 in both cases). Initial severity of hand impairment and testing compliance were strong predictors of improvement. Caregivers reported significant increases in involved limb frequency of use and quality of movement. However, there was no change in strength, sensibility, or muscle tone (p>0.05 in all cases). Results suggest that for a carefully selected subgroup of children with hemiplegic CP, CI therapy modified to be child-friendly, appears to be efficacious in improving movement efficiency of the involved upper extremity.

Analysis of Variance↗

PubMed2006

Activity limitation in hemiplegic cerebral palsy: evidence for disorders in motor planning.

Review of the definition of cerebral palsy (CP) has focused on disorders of movement and posture development that cause activity limitations. Recent research provides new insights into CP, showing that activity limitation in individuals with hemiplegic CP is not exclusively caused by disorders related to movement execution, but is also related to the planning of movements. In this review article, converging evidence is presented suggesting that, in addition to movement execution impairments, impairments in movement planning may also limit the performance of activities of daily living. Evidence from studies of fingertip-force planning and anticipatory planning in object manipulation tasks is discussed.

Activities of Daily Living↗

PubMed2006

Development of hand-arm bimanual intensive training (HABIT) for improving bimanual coordination in children with hemiplegic cerebral palsy.

Constraint-induced (CI) movement therapy is a physical intervention that has been receiving increasing attention in pediatric rehabilitation. So far, the evidence suggests that practice associated with CI therapy may improve impaired unimanual hand function in some children with hemiplegic cerebral palsy (CP). However, CI therapy has several important limitations. Most importantly, children with hemiplegia have impairments in bimanual coordination beyond their unilateral impairments. Thus, an intervention approach to increase functional independence during activities of daily living by using both hands in cooperation is needed. Here we briefly review the etiology of hemiplegic CP, describe studies of pediatric CI therapy efficacy in relation to the etiology, discuss the conceptual and practical limitations of CI therapy for this population, and describe bimanual coordination impairments in children with hemiplegia. Finally, we introduce a new intervention for children with hemiplegia, hand-arm bimanual intensive training (HABIT), to address the limitations of CI therapy and to improve bimanual coordination. HABIT retains the two major elements of pediatric CI therapy (intensive structured practice and child-friendliness). The proposed methodology demonstrates that extensive targeted practice can be provided in a child-friendly manner without using a physical restraint, although the efficacy of such an approach remains to be determined.

Arm↗

PubMed2006

Efficacy of constraint-induced movement therapy on involved upper-extremity use in children with hemiplegic cerebral palsy is not age-dependent.

OBJECTIVES: Constraint-induced (CI) movement therapy has been shown recently to be promising for improving upper-limb function in children with cerebral palsy (CP). Because little is known about patient characteristics predicting treatment efficacy, not all children may benefit from this intervention. Here we examine the relationship between efficacy of a child-friendly form of CI therapy and age on involved upper-extremity function. DESIGN: Twenty children with hemiplegic CP age 4 to 13 years received CI therapy and completed evaluations. Based on established functional and neuromaturational changes in hand skill development, the children were divided into a "younger group" (age 4-8 years, n = 12) and "older group" (age 9-13 years, n = 8). Children wore a sling on their noninvolved upper extremity for 6 hours per day for 10 of 12 consecutive days, during which time they were engaged in play and functional activities. Each child was evaluated by trained evaluators who were blinded to the fact that the children received treatment. The evaluations took place once before the intervention and at 1 week, 1 month, and 6 months after the intervention. Efficacy was examined at the movement efficiency (Jebsen-Taylor Test of Hand Function, subtest 8 of the Bruininks-Oseretsky Test of Motor Proficiency), environmental (caregiver frequency and quality of involved upper-limb use), and impairment (strength, tactile sensitivity, and muscle tone) levels. RESULTS: Children in both age groups had significant improvements in involved hand-movement efficiency and environmental functional limitations, which were retained through the 6-month posttest. However, there were no differences in efficacy between younger and older children. Both hand severity and the children's behavior during testing (number of redirections), with the latter serving as a reasonable correlate for attention during the intervention, were related to changes in performance in the younger group but not in the older group. CONCLUSIONS: The results suggest that the intensive practice associated with CI therapy can improve movement efficiency and environmental functional limitations among a carefully selected subgroup of children with hemiplegic CP of varying ages and that this efficacy is not age-dependent.

Adolescent↗

PubMed2006

Development of hand function and precision grip control in individuals with cerebral palsy: a 13-year follow-up study.

OBJECTIVE: Although children with cerebral palsy display large developmental differences in hand function from that of typically developing children by the age of 6 to 10 years, little is known about the developmental processes underlying hand function during subsequent development. In this study we investigated the development of manual dexterity in a timed motor task, the timing and amplitude of fingertip-force application during a precision grasping task, and the relationship between changes in these measures. We applied highly quantitative analytical approaches to determine if the fingertip-force application pattern and trial-to-trial variation of fingertip-force application change during development. METHODS: Twelve subjects with cerebral palsy (aged 6-8 years) participated in the first data-collection session conducted between 1989 and 1990. Ten of these subjects (5 with hemiplegia and 5 with diplegia, aged 19-21 years) returned between 2002 and 2003. Manual dexterity was measured by using timed tasks of the Jebsen-Taylor test of hand function. Subjects also lifted an object instrumented with force transducers while we measured the temporal coordination of fingertip coordination and the path ratio between the grip and vertical load-force trajectory (straightness). We used generalized procrustes analysis to determine if there were changes in shape of the force trajectory and intertrial variability. RESULTS: The Jebsen-Taylor test times decreased 45% from the first to the second data session. The overall time to complete the grip-lift task decreased 22%, mainly because of a faster transition from grasp to lift. The grip-force/load-force path ratios decreased from 1.7 to 1.35 (1 = straight line). Generalized procrustes analysis indicated a change in the shape and a decrease in variability in shape of the force-ratio path. CONCLUSIONS: Our results demonstrate that the efficiency in grasping had developed during a 13-year period for this small group of participants with cerebral palsy, which suggests that improvement in hand function occurs over a longer time frame than commonly would be expected.

Adult↗

PubMed2005

Visual properties of objects affect manipulative forces and respiration differently.

Previously, we demonstrated that the respiratory and motor systems responded differently following consecutive lifts of an object whose weight could be altered (lighter or heavier) without changing the object's visual properties. When the weight of the object was altered in a manner unpredictable to the subject, the motor system response reflected the previous weight of the object (light or heavy) while the respiratory system reflected responses seen when lifting the heavier object regardless of whether a lighter or heavier object was lifted previously. It is possible that the default pattern of the respiratory system was due to a lack of visual size cues, which are known to have robust affects on grasp control. To test this hypothesis, 14 seated subjects performed self-initiated alternating lifts with objects whose size and weight covaried such that the weight of the upcoming lift was known despite the weight of the object previously lifted. Following both consecutive and alternating trials, the load force was scaled to the weight of the object (e.g., the heavier the object the larger the force) while the volume was scaled only following the consecutive trials. This suggests that the load forces were developed entirely based on visual information while lung volume was not. In addition, we suggest that following the consecutive trials, the volume increased as the object's weight increased in an effort to assist with trunk stabilization by indirectly increasing intra-abdominal pressure.

Adult↗

PubMed2005

Prior experience and current goals affect muscle-spindle and tactile integration.

We previously have shown that reports of illusory elbow extension from biceps vibration can be attenuated by touching a stationary cue-surface with the index fingertip of a vibrated arm. However, this was not the case if the subject had previously felt genuine motion of the cue-surface without biceps vibration. Two potential explanations for this are that the sense of elbow orientation results from tactile and muscle stretch cues that are integrated based on (1) an awareness of the tactile cue's mobility or (2) specific patterns of tactile and muscle spindle activity resembling the elbow motion during previous interactions with the tactile cue. We tested these hypotheses by comparing how touching the cue-surface attenuated the reports of arm movement during biceps vibration after a demonstration of the cue- surface mobility without involving any elbow motion versus simultaneously touching the cue-surface as it moved and extending the elbow to correspond exactly to the elbow extension illusion during vibration. Touching the cue-surface stopped attenuating the reports of elbow extension during biceps vibration only after experiencing actual cue-surface motion while moving the elbow . This supports the second hypothesis that tactile and muscle stretch feedback that are integrated based on specific patterns of tactile and muscle spindle activity recalled from previous interactions with the tactile cue. We also tested the influence of motor set on the sense of elbow position in this paradigm. We found that even after touching the stationary cue-surface had ceased to attenuate illusory elbow motion during biceps vibration, illusory elbow motion during vibration still could be attenuated. This was possible if the subjects intended to actively use their wrists rather than the elbow to maintain fingertip contact. We conclude that muscle stretch and tactile cues are integrated to locate the arm within a highly specific context associated with tactile and proprioceptive feedback from prior experience and current movement goals.

Adult↗

PubMed2005

Patterns of impairment in digit independence after subcortical stroke.

The nature of impairment in hand motor control after stroke and its relationship to hand function are still not well understood. In this study, we investigated digit independence in patients with subcortical stroke (n = 8) and moderate hand impairment, defined by wrist and hand Fugl-Meyer scale scores < or =25/33, and age-matched controls (n = 8). Subjects made cyclical flexion-extension movements of an instructed digit while keeping the other digits as still as possible. Movements of the metacarpo-phalangeal (MCP) joints of the five digits were measured using an instrumented glove. The ability to move an instructed digit individually (individuation index), and the ability to keep a noninstructed digit as still as possible (stationarity index) were determined for each digit. Contrary to the finding of normal thumb individuation in a recent study of patients with variable hand motor impairment after stroke, we found that independent movement for all digits was significantly impaired, although individuation and stationarity were differentially affected for each digit. All the digits, including the thumb, showed a similar impairment in individuation. In contrast, stationarity was affected in a digit-dependent pattern: the thumb was affected least, and the middle finger was most impaired. Stroke subjects did not extend their digits fully to the baseline position, and the angular displacement at maximum digit extension correlated significantly with digit individuation. Contrary to expectation, digit independence correlated weakly with clinical tests of hand function, which emphasize grasp. This suggests that corticospinal projections might be separated with respect to function rather than finger topography.

Adult↗

PubMed2005

Methods of constraint-induced movement therapy for children with hemiplegic cerebral palsy: development of a child-friendly intervention for improving upper-extremity function.

We delineate the methodology for constraint-induced movement therapy (CIMT) modified for children with hemiplegic cerebral palsy (CP) and describe important considerations that need to be made when testing this intervention in children. The resulting intervention evolved from piloting and testing it with 38 children with hemiplegic CP who were between the ages of 4 and 14 years. Thirty-seven successfully completed the treatment protocol. The intervention retains the 2 major elements of the adult CIMT (repetitive practice, shaping) and was constructed to be as child-friendly as possible. It involves restraining the noninvolved extremity with a sling and having the child engage in unimanual activities with the involved extremity 6 hours a day for 10 days (60 h). Specific activities are selected by considering joint movements with pronounced deficits and improvement of which interventionists believe have greatest potential. The activities are chosen to elicit repetitive practice and shaping. The intervention is conducted in groups of 2 to 3 children to provide social interaction, modeling, and encouragement. Each child is assigned to an interventionist to maintain at least a 1:1 ratio. CIMT can be modified to be child-friendly while maintaining all practice elements of the adult CIMT. The modified therapy is tolerated by most children. Further modifications will likely be required to hone in on the specific components of the intervention that are most effective before applying them to children who are most likely to benefit.

Adolescent↗

PubMed2005

Speech motor development during acquisition of the voicing contrast.

Lip and jaw movements were studied longitudinally in 19-month-old children as they acquired the voicing contrast for /p/ and /b/. A movement tracking system obtained lip and jaw kinematics as participants produced the target utterances /papa/ and /baba/. Laryngeal adjustments were also tracked through acoustically recorded voice onset time (VOT) of the consonants. Across this period of developmental phonological change, the children began to produce VOTs in 2 distinct categories for voiced and voiceless plosives. Specific kinematic differences were observed during oral opening and closing and between spatial and temporal parameters of movement. The development of the voicing contrast was most closely associated with changes in jaw kinematics for oral opening in comparison to that of the lip. Conversely, movements into oral closing were not accompanied by significant increases in jaw, upper lip, or lower lip displacement or velocity, although a decrease in jaw movement variability was found. There was no evidence of phoneme-specific movement differences between /p/ and /b/ in the children or in the adults studied. Spatial coupling between the jaw and upper lip changed significantly across sessions, whereas changes in temporal coupling were not observed. Findings indicate that oral opening and closing have different task requirements and that children modify their articulatory movements to meet the demands of each task. Overall, the findings illustrate how orofacial movements and laryngeal function change in parallel during linguistic development.

Adult↗

PubMed2005

A critical review of constraint-induced movement therapy and forced use in children with hemiplegia.

Hemiplegia is a physical impairment that can occur in childhood following head trauma, cerebral vascular accident or transient ischemic attack (stroke), brain tumor, or congenital or perinatal injury. One of the most disabling symptoms of hemiplegia is unilaterally impaired hand and arm function. Sensory and motor impairments in children with hemiplegia compromise movement efficiency. Such children often tend not to use the affected extremity, which may further exacerbate the impairments, resulting in a developmentally learned non-use of the involved upper extremity, termed 'developmental disuse'. Recent studies suggest that children with hemiplegia benefit from intensive practice. Forced use and Constraint-Induced Movement Therapy (CI therapy) are recent therapeutic interventions involving the restraint of the non-involved upper extremity and intensive practice with the involved upper extremity. These approaches were designed for adults with hemiplegia, and increasing evidence suggests that they are efficacious in this population. Recently, forced use and constraint-induced therapy have been applied to children with hemiplegia. In this review, we provide a brief description of forced use and CI therapy and their historical basis, provide a summary of studies of these interventions in children, and discuss a number of important theoretical considerations, as well as implications for postural control. We will show that whereas the studies to date suggest that both forced use and CI therapy appear to be promising for improving hand function in children with hemiplegia, the data are limited. Substantially more work must be performed before this approach can be advocated for general clinical use.

Age Factors↗

PubMed2004

Control of multidigit grasping in Parkinson's disease: effect of object property predictability.

We examined the extent to which subjects with Parkinson's disease (PD) modulate normal fingertip forces during five-digit grasping based on the object's center of mass (CM). We also tested the effect of trial-to-trial predictability of CM location on the distribution of all fingertip forces relative to thumb force. Ten right-handed subjects with PD (OFF and ON medication) and 10 healthy age-matched control subjects participated. Subjects lifted a manipulandum that measured normal forces exerted by each digit. The CM location was changed from trial-to-trial either in an unpredictable (random) or predictable (blocked) order. Discriminant analysis and information theory were used to quantify the extent to which force-sharing patterns could be discriminated as a function of CM location. All subjects modulated fingertip normal forces as a function of CM location regardless of its predictability, although larger forces were employed when its location was unpredictable. However, in controls, normal force modulation of individual fingers to the object's CM location occurred over a greater range of forces when the CM location was predictable than when it was unpredictable. In contrast, subjects with PD exhibited a similar force modulation to CM location regardless of its predictability. There was a clearer discrimination of force-sharing patterns when the CM location was predictable for controls but not for subjects with PD OFF medication. Medication improved the time course of normal force modulation to CM location. These results indicate that subjects with PD maintained the ability to modulate individual fingertip forces to the object's physical properties. Nevertheless, subjects with PD did not benefit from the a priori knowledge of object CM location to the same extent as controls. These findings support the notion that PD affects the ability to use anticipatory control mechanisms.

Adult↗

PubMed2004

Bimanual coordination during a goal-directed task in children with hemiplegic cerebral palsy.

Most studies of impaired hand function in children with hemiplegic cerebral palsy (CP) have focused on either the involved or the non-involved extremity in isolation. Coordination of the involved and non-involved hand during bimanual tasks in these children is not well understood. The present study examined bimanual coordination using a drawer-opening task under speed and hand constraints in 10 children with hemiplegic CP (5 males and 5 females, mean age 13y 5mo, range 8y to 16y) and 10 age-matched right-handed developing typically children (6 males and 4 females, mean age 13y 1mo). Children were asked to reach forward and open a drawer with one hand and then activate a light switch inside the drawer with the contralateral hand. The role of the two hands (open drawer and activate switch) and speed (self-paced vs fast-as-possible) were varied. The children with hemiplegic CP were slower (p<0.001) and less coordinated in this task, with reduced movement overlap of the two hands (p<0.001) and sequential completion of the two movement objectives (p<0.001). Moreover, the hand used for each task subcomponent affected task performance for the children with hemiplegic CP (p<0.05). Interestingly, faster speed facilitated better bimanual coordination for the children with hemiplegic CP (p<0.001). Results highlight the importance of movement constraints on task performance and suggest that movement speed might facilitate better bimanual coordination.

Adolescent↗

PubMed2003

Influence of fingertip contact on illusory arm movements.

Recent evidence suggests that reaching movements are more accurate when end point contact occurs, suggesting that fingertip contact contributes to a final estimation of arm position. In the present study we tested two hypotheses: 1). that fingertip contact influences illusions of arm movement produced by muscle vibration and 2). that this influence depends on the a priori context of the stability of the contact surface. Subjects sat with their elbows on a table and eyes closed. They demonstrated the perceived orientation of the left (cue) arm by mirroring the location with the right (report) arm. We manipulated deep proprioceptive cues by vibrating the left biceps brachia, causing illusions of elbow extension, and tested whether these illusions were altered when the fingertip remained in contact with a stable external surface. The context at this point represents a prior assumption that the external contact surface is stable. Midway through the experiment, the context was changed by challenging the prior assumption that the contact surface was stable by demonstrating that it could move. Unbeknownst to the subject, the external contact surface remained stable during data collection throughout the experiment. As expected, without tactile cues, biceps vibration caused illusory elbow extension. Conditions with fingertip contact and biceps vibration in the stable context demonstrated that contact largely eliminated the overestimation of cue arm elbow angle. However, in the context of a possibly unstable (movable) contact surface, the reports of elbow extension returned. Thus a priori notions about the stability context of an external contact surface influence how this tactile cue is integrated with proprioceptive sensory modalities to generate an estimate of arm location in space. These findings support the notion that tactile cues are used to calibrate proprioception against external spatial frameworks.

Adult↗

PubMed2003

Tactile feedback contributes to consistency of finger movements during typing.

Touch typing movements are typically too brief to use on-line feedback. Yet, previous studies have shown that blocking tactile feedback of the fingertip of typists leads to an increase in typing errors. To determine the contribution of tactile information to rapid fine motor skills, we analyzed kinematics of the right index finger during typing with and without tactile feedback. Twelve expert touch typists copy-typed sentences on a computer keyboard without vision of their hands or the computer screen. Following control trials, their right index fingertip was anesthetized, and sentences were typed again. The movements of the finger were recorded with an instrumented glove and electromagnetic position sensor. During anesthesia, typing errors of that finger increased sevenfold. While the inter-keypress timing and average kinematics were unaffected, there was an increase in variability of all measures. Regression analysis showed that endpoint variability was largely accounted for by start location variability. The results suggest that tactile cues provide information about the start location of the finger, which is necessary to perform typing movements accurately.

Adult↗