Impairment of pronation, supination, and body co-ordination in reach-to-grasp tasks in human Parkinson's disease (PD) reveals homology to deficits in animal models

Analysis of skilled forelimb movement in rats: the single pellet reaching test and staircase test

Brain damage, stroke, and neurodegenerative diseases such as Parkinson's or Huntington's disease can cause severe motor deficits in skilled forelimb use in both humans and rats. These deficits are typically analyzed in a reach-to-eat paradigm. Skilled reaching in rats has been found to be a good model of human skilled reaching. Therefore, rats serve as an excellent tool to monitor the development of deficits after neurological insults or changes after medical intervention. The following protocols comprise two different tests of rat skilled reaching. The single pellet reaching test is a paradigm that involves detailed rating and analysis of qualitative aspects of the reaching movement itself. The staircase test is an objective, high-throughput reaching task that allows reaching success (number of pellets eaten) to be investigated in multiple rats at the same time. Both tests have been used extensively to investigate motor deficits and effects of treatment.

Animal models of post-ischemic forced use rehabilitation: methods, considerations, and limitations

Many survivors of stroke experience arm impairments, which can severely impact their quality of life. Forcing use of the impaired arm appears to improve functional recovery in post-stroke hemiplegic patients, however the mechanisms underlying improved recovery remain unclear. Animal models of post-stroke rehabilitation could prove critical to investigating such mechanisms, however modeling forced use in animals has proven challenging. Potential problems associated with reported experimental models include variability between stroke methods, rehabilitation paradigms, and reported outcome measures. Herein, we provide an overview of commonly used stroke models, including advantages and disadvantages of each with respect to studying rehabilitation. We then review various forced use rehabilitation paradigms, and highlight potential difficulties and translational problems. Lastly, we discuss the variety of functional outcome measures described by experimental researchers. To conclude, we outline ongoing challenges faced by researchers, and the importance of translational communication. Many stroke patients rely critically on rehabilitation of post-stroke impairments, and continued effort toward progression of rehabilitative techniques is warranted to ensure best possible treatment of the devastating effects of stroke.

Effects of Treadmill Exercise on the Recovery of Dopaminergic Neuron Loss and Muscle Atrophy in the 6-OHDA Lesioned Parkinson's Disease Rat Model

This study was to determine the effect of exercise on the recovery of dopaminergic neuron loss and muscle atrophy in 6-OHDA-induced hemi Parkinson's disease model. Exercise was loaded twice per day for 30 minutes each time, at 5 days after 6-OHDA lesioning and continued for 16 days using a treadmill. Exercise significantly increased the number of tyrosine hydroxylase positive neuron in the lesioned substantia nigra and the expression level of tyrosine hydroxylase in the striatum compared with the control group. To examine which signaling pathways may be involved in the exercise, the phosphorylation of GSK3β and ERK were observed in the striatum. In the control group, basal level of GSK3β phosphorylation was less than in both striatum, but exercise increased it. ERK phosphorylation decreased in the lesioned striatum, but exercise recovered it. These findings suggest that exercise inactivates GSK3β by phosphorylation which may be involved in the neuroprotective effect of exercise on the 6-OHDA-induced cell death. In the exercise group, weight, and Type I and II fiber cross-sectional area of the contralateral soleus significantly recovered and expression of myosin heavy chain and Akt and ERK phosphorylation significantly increased by exercise. These results suggest that exercise recovers Parkinson's disease induced dopaminergic neuron loss and contralateral soleus muscle atrophy.

Manganese mixture inhalation is a reliable Parkinson disease model in rats

Manganese (Mn) is an essential trace metal. Regardless of its essentiality, it has been reported that the overexposure causes neurotoxicity manifested as extrapyramidal symptoms similar to those observed in Parkinson disease (PD). Recently, our group reported that mice that inhaled for 5 months the mixture of manganese chloride (MnCl(2)) and manganese acetate Mn(OAc)(3) developed movement abnormalities, significant loss of substantia nigra compacta (SNc) dopaminergic neurons, dopamine depletion and improved behavior with l-DOPA treatment. However, this model has only been characterized in mice. In order to have a well-supported and generalizable model in rodents, we used male Wistar rats that inhaled a mixture of 0.04 M MnCl(2) and 0.02 M Mn(OAc)(3), 1h three times a week for 6 months. Before Mn exposure, animals were trained to perform motor tests (Beam-walking and Single-pellet reaching tasks) and were evaluated each week after the exposure. The mixture of MnCl(2)/Mn(OAc)(3) caused alterations in the motor tests, 75.95% loss of SNc dopaminergic neurons, and no cell alterations in Globus Pallidus or striatum. With these results we conclude that the inhalation of the mixture of Mn compounds is a useful model in rodents for the study of PD.

Closing the gap between clinic and cage: sensori-motor and cognitive behavioural testing regimens in neurotoxin-induced animal models of Parkinson's disease

Animal models that make use of chemical toxins to adversely affect the nigrostriatal dopaminergic pathway of rodents and primates have contributed significantly towards the development of symptomatic therapies for Parkinson's disease (PD) patients. Although their use in developing neuro-therapeutic and -regenerative compounds remains to be ascertained, toxin-based mammalian and a range of non-mammalian models of PD are important tools in the identification and validation of candidate biomarkers for earlier diagnosis, as well as in the development of novel treatments that are currently working their way into the clinic. Toxin models of PD have and continue to be important models to use for understanding the consequences of nigrostriatal dopamine cell loss. Functional assessment of these models is also a critical component for eventual translational success. Sensitive behavioural testing regimens for assessing the extent of dysfunction exhibited in the toxin models, the degree of protection or improvement afforded by potential treatment modalities, and the correlation of these findings with what is observed clinically in PD patients, ultimately determines whether a potential treatment moves to clinical trials. Here, we review existing published work that describes the use of such behavioural outcome measures associated with toxin models of parkinsonism. In particular, we focus on tests assessing sensorimotor and cognitive function, both of which are significantly and progressively impaired in PD.

Oral hapsis guides accurate hand preshaping for grasping food targets in the mouth

Preshaping the digits and orienting the hand when reaching to grasp a distal target is proposed to be optimal when guided by vision. A reach-to-grasp movement to an object in one's own mouth is a natural and commonly used movement, but there has been no previous description of how it is performed. The movement requires accuracy but likely depends upon haptic rather than visual guidance, leading to the question of whether the kinematics of this movement are similar to those with vision or whether the movement depends upon an alternate strategy. The present study used frame-by-frame video analysis and linear kinematics to analyze hand movements as participants reached for ethologically relevant food targets placed either at a distal location or in the mouth. When reaching for small and medium-sized food items (blueberries and donut balls) that had maximal lip-to-target contact, hand preshaping was equivalent to that used for visually guided reaching. When reaching for a large food item (orange slice) that extended beyond the edges of the mouth, hand preshaping was suboptimal compared to vision. Nevertheless, hapsis from the reaching hand was used to reshape and reorient the hand after first contact with the large target. The equally precise guidance of hand preshaping under oral hapsis is discussed in relation to the idea that hand preshaping, and its requisite neural circuitry, may have originated under somatosensory control, with secondary access by vision.

Effect of DHEA on recovery of muscle atrophy induced by Parkinson's disease

PURPOSE

The purpose of this study was to determine the effect of dehydroepiandrosterone (DHEA) on recovery of muscle atrophy induced by Parkinson's disease.

METHODS

The rat model was established by direct injection of 6-hydroxydopamine (6-OHDA, 20μg) into the left striatum using stereotaxic surgery. Rats were divided into two groups; the Parkinson's disease group with vehicle treatment (Vehicle; n=12) or DHEA treatment group (DHEA; n=22). DHEA or vehicle was administrated intraperitoneally daily at a dose of 0.34 mmol/kg for 21 days. At 22-days after DHEA treatment, soleus, plantaris, and striatum were dissected.

RESULTS

The DHEA group showed significant increase (p<.01) in the number of tyrosine hydroxylase (TH) positive neurons in the lesioned side substantia nigra compared to the vehicle group. Weights and Type I fiber cross-sectional areas of the contralateral soleus of the DHEA group were significantly greater than those of the vehicle group (p=.02, p=.00). Moreover, extracellular signal-regulated kinase (ERK) phosphorylation significantly decreased in the lesioned striatum, but was recovered with DHEA and also in the contralateral soleus muscle, Akt and ERK phosphorylation recovered significantly and the expression level of myosin heavy chain also recovered by DHEA treatment.

CONCLUSION

Our results suggest that DHEA treatment recovers Parkinson's disease induced contralateral soleus muscle atrophy through Akt and ERK phosphorylation.

Recovery from ischemia in the middle-aged brain: a nonhuman primate model

Studies of recovery from stroke mainly utilize rodent models and focus primarily on young subjects despite the increased prevalence of stroke with age and the fact that recovery of function is more limited in the aged brain. In the present study, a nonhuman primate model of cortical ischemia was developed to allow the comparison of impairments in young and middle-aged monkeys. Animals were pretrained on a fine motor task of the hand and digits and then underwent a surgical procedure to map and lesion the hand-digit representation in the dominant motor cortex. Animals were retested until performance returned to preoperative levels. To assess the recovery of grasp patterns, performance was videotaped and rated using a scale adapted from human occupational therapy. Results demonstrated that the impaired hand recovers to baseline in young animals in 65-80 days and in middle-aged animals in 130-150 days. However, analysis of grasp patterns revealed that neither group recover preoperative finger thumb grasp patterns, rather they develop compensatory movements.

The use of rodent skilled reaching as a translational model for investigating brain damage and disease

Neurological diseases, including Parkinson's disease, Huntington's disease, and brain damage caused by stroke, cause severe motor impairments. Deficits in hand use are one of the most debilitating motor symptoms and include impairments in body posture, forelimb movements, and finger shaping for manipulating objects. Hand movements can be formally studied using reaching tasks, including the skilled reaching task, or reach-to-eat task. For skilled reaching, a subject reaches for a small food item, grasps it with the fingers, and places it in the mouth for eating. The human movement and its associated deficits can be modeled by experimental lesions to the same systems in rodents which in turn provide an avenue for investigating treatments of human impairments. Skilled reaching movements are scored using three methods: (1) end point measures of attempts and success, (2) biometric measures, and (3) movement element rating scales derived from formal descriptions of movement. The striking similarities between human and rodent reaching movements allow the analysis of the reach-to-eat movement to serve as a powerful tool to generalize preclinical research to clinical conditions.

Cranial and related sensorimotor impairments in rodent models of Parkinson's disease

In Parkinson's disease both limb and cranial sensorimotor functions are impaired, leading to a profound diminished quality of life for many patients. Toxin and genetic animal models of Parkinson's disease are likely essential for understanding the pathology associated with these impairments as well as for the development and testing of potential therapeutics. Here we describe useful novel and established behavioral outcome measures for assessing limb and cranial sensorimotor functions in toxin and genetic models of parkinsonism in rats and mice.

The consummatory origins of visually guided reaching in human infants: a dynamic integration of whole-body and upper-limb movements

Reaching-to-eat (skilled reaching) is a natural behaviour that involves reaching for, grasping and withdrawing a target to be placed into the mouth for eating. It is an action performed daily by adults and is among the first complex behaviours to develop in infants. During development, visually guided reaching becomes increasingly refined to the point that grasping of small objects with precision grips of the digits occurs at about one year of age. Integration of the hand, upper-limbs, and whole body are required for successful reaching, but the ontogeny of this integration has not been described. The present longitudinal study used Laban Movement Analysis, a behavioural descriptive method, to investigate the developmental progression of the use and integration of axial, proximal, and distal movements performed during visually guided reaching. Four infants (from 7 to 40 weeks age) were presented with graspable objects (toys or food items). The first prereaching stage was associated with activation of mouth, limb, and hand movements to a visually presented target. Next, reaching attempts consisted of first, the advancement of the head with an opening mouth and then with the head, trunk and opening mouth. Eventually, the axial movements gave way to the refined action of one upper-limb supported by axial adjustments. These findings are discussed in relation to the biological objective of reaching, the evolutionary origins of reaching, and the decomposition of reaching after neurological injury.

Manganese inhalation as a Parkinson disease model

The present study examines the effects of divalent and trivalent Manganese (Mn²⁺/Mn³⁺) mixture inhalation on mice to obtain a novel animal model of Parkinson disease (PD) inducing bilateral and progressive dopaminergic cell death, correlate those alterations with motor disturbances, and determine whether L-DOPA treatment improves the behavior, to ensure that the alterations are of dopaminergic origin. CD-1 male mice inhaled a mixture of Manganese chloride and Manganese acetate, one hour twice a week for five months. Before Mn exposure, animals were trained to perform motor function tests and were evaluated each week after the exposure. By the end of Mn exposure, 10 mice were orally treated with 7.5 mg/kg L-DOPA. After 5 months of Mn mixture inhalation, striatal dopamine content decreased 71%, the SNc showed important reduction in the number of TH-immunopositive neurons, mice developed akinesia, postural instability, and action tremor; these motor alterations were reverted with L-DOPA treatment. Our data provide evidence that Mn²⁺/Mn³⁺ mixture inhalation produces similar morphological, neurochemical, and behavioral alterations to those observed in PD providing a useful experimental model for the study of this neurodegenerative disease.

Challenges Facing Quantification of Rat Locomotion along Beams of Varying Widths

Optoelectronic motion capture systems have been widely used to investigate temporal gait parameters in humans and animals in order to understand function and behavioural attributes of different pathologies, e.g. Parkinson's disease (PD). The aim of the present paper was to investigate the practicality of utilising this system to investigate the effects of a unilateral 6-hydroxydopamine (6-OHDA) lesion on rat locomotion while walking on beams of varying widths (graduated, narrow, and wide). Temporal gait parameters of ten male Lister Hooded rats (five controls and five hemiparkinsonian) were observed using passive markers placed in locations that were representative of their four limbs and their body axis. The results demonstrate that marker-based motion capture can provide an effective and simple approach to quantifying temporal gait parameters for rat models of PD. They also reveal how the width of the path affects the locomotion in both experimental cohorts. Such measurements can be compared with human motion analysis to explore correlations between the animal model and human behaviour, which is an important step for translational medicine.

Music attenuates excessive visual guidance of skilled reaching in advanced but not mild Parkinson's disease

Parkinson's disease (PD) results in movement and sensory impairments that can be reduced by familiar music. At present, it is unclear whether the beneficial effects of music are limited to lessening the bradykinesia of whole body movement or whether beneficial effects also extend to skilled movements of PD subjects. This question was addressed in the present study in which control and PD subjects were given a skilled reaching task that was performed with and without accompanying preferred musical pieces. Eye movements and limb use were monitored with biomechanical measures and limb movements were additionally assessed using a previously described movement element scoring system. Preferred musical pieces did not lessen limb and hand movement impairments as assessed with either the biomechanical measures or movement element scoring. Nevertheless, the PD patients with more severe motor symptoms as assessed by Hoehn and Yahr (HY) scores displayed enhanced visual engagement of the target and this impairment was reduced during trials performed in association with accompanying preferred musical pieces. The results are discussed in relation to the idea that preferred musical pieces, although not generally beneficial in lessening skilled reaching impairments, may normalize the balance between visual and proprioceptive guidance of skilled reaching.

Sema4D/CD100 deficiency leads to superior performance in mouse motor behavior

BACKGROUND

Sema4D/CD100 is a type of class 4 semaphorin, exhibiting crucial roles in growth cone guidance in developing neurons. Sema4D is widely expressed throughout the central nervous system in embryonic mouse brain, and is selectively localized to oligodendrocytes and myelin in the postnatal brain. However, direct evidence of the actual involvement of Sema4D in the neuronal network development crucial for neurobehavioral performance is still lacking. The present study therefore examined whether Sema4D deficiency leads to abnormal behavioral development.

METHODS

Both wild-type and Sema4D-deficient mice were subjected to behavioral analyses including open-field, adhesive tape removal, rotarod tests and a water maze task.

RESULTS

Open-field tests revealed increased locomotor activity in Sema4D-deficient mice with less percentage of time spent in the center of the field. In both the adhesive tape removal and rotarod tests, which examine motor coordination and balance, Sema4D-deficient mice showed significantly superior performance, suggesting facilitated motor behavior. Both Sema4D-deficient and wild-type mice successfully learnt the water maze task, locating a hidden escape platform, and also showed precise memory for the platform position in probe tests. However, the swimming speed of Sema4D-deficient mice was significantly faster than that of wild-type mice, providing further evidence of their accelerated motor behavior.

CONCLUSION

Our mouse behavioral analyses revealed enhanced motor activity in Sema4D-deficient mice, suggesting the crucial involvement of Sema4D in the neurodevelopmental processes of the central structures mediating motor behavior in mice.

Experimental models: help or hindrance

Although many potential therapeutics have improved motor and cognitive function in animal models of experimental stroke, very few have been found to have similar beneficial effects in clinical trials. In this review, we examine the advantages and disadvantages of the currently available rodent models in the development of cellular therapies for stroke and how they have been applied. The lack of translation between the animal work and clinical benefits is not because the animal models are not useful. If the recommendations of the Stroke Academic Industry Roundtable are followed, then the studies will produce more clinically relevant information about potential new cell therapies. However, it will also be necessary to design clinical trials in a manner consistent with the preclinical study results.

Stress accelerates neural degeneration and exaggerates motor symptoms in a rat model of Parkinson's disease

The causes of most cases of Parkinson's disease (PD) are still poorly understood. Here we show that chronic stress and elevated corticosterone levels exaggerate motor deficits and neurodegenerative events in a Parkinson's disease rat model. Animals were tested in skilled and non-skilled movement while being exposed to daily restraint stress or oral corticosterone treatment. Stress and corticosterone compromised normal motor function and exaggerated motor deficits caused by unilateral 6-hydroxydopamine lesion of the nigrostriatal bundle. Moreover, stress and corticosterone treatments diminished the ability to acquire compensatory strategies in limb use during skilled reaching and skilled walking. In contrast, lesion control animals were able to significantly improve in the ability of skilled limb use during the repeated test sessions. The exaggerated motor impairments in stress-treated animals were related to accelerated loss of midbrain dopamine-producing neurons during the first week postlesion. Correlation analysis revealed a significant connection between loss of tyrosine hydroxylase-positive cells and increase in Fluoro-Jade-positive cells only in stress- and corticosterone-treated animals. Furthermore, stress and elevated corticosterone levels caused greater permanent loss of midbrain neurons than found in non-treated lesion animals. These findings demonstrate that stress and elevated corticosterone levels can exaggerate nigral neuronal loss and motor symptoms in a rat analogue of PD. It is therefore possible that stress represents a key factor in the pathogenesis of human PD by impeding functional and structural compensation and exaggerating neurodegenerative processes.

Inhalation of divalent and trivalent manganese mixture induces a Parkinson's disease model: immunocytochemical and behavioral evidences

The present study investigates the effects of divalent and trivalent manganese (Mn(2+)/Mn(3+)) mixture inhalation on mice to obtain a novel animal model of Parkinson disease (PD) inducing bilateral and progressive cell death in the substantia nigra compacta (SNc) and correlating these alterations with motor disturbances. CD-1 male mice inhaled a mixture of 0.04 M manganese chloride (MnCl(2)) and manganese acetate (Mn(OAc)(3)), 1 h twice a week for 5 months. Before Mn exposure, animals were trained to perform motor function tests and were evaluated each week after the exposure. By doing this, overall behavior was assessed by ratings and by videotaped analyses; by the end of Mn exposure period, animals were killed. The mesencephalon was processed for tyrosine hydroxylase (TH) immunocytochemistry. After 5 months of Mn mixture inhalation, mice developed evident deficits in their motor performance manifested as akinesia, postural instability and action tremor. SNc of the Mn-exposed animals showed an important decrease (67.58%) in the number of TH-immunopositive neurons. Our data provide evidence that MnCl(2) and Mn(OAc)(3) mixture inhalation produces similar morphological and behavioral alterations to those observed in PD providing a useful experimental model for the study of this neurodegenerative disease.

Experience--a double edged sword for restorative neural plasticity after brain damage

During the time period following damage, the brain undergoes widespread reorganizational processes. Manipulations of behavioral experience can be potent therapeutic interventions for shaping this reorganization and enhancing long-term functional outcome. Recovery of function is a major concern for survivors of central nervous system damage and management of post-injury rehabilitation is increasingly becoming a topic of chief importance. Animal research, the focus of this review, suggests that, in the absence of behavioral manipulations, the brain is unlikely to realize its full potential for supporting function. However, experiences also have the capacity to be maladaptive for brain and behavioral function. From a treatment perspective, it may be unwise to adopt the canon of "first, do no harm" because maladaptive experiences include behaviors that individuals learn to do on their own. A better understanding of how behavioral experience interacts with brain reorganization could result in rehabilitative therapies, individually tailored and optimized for functional outcome.

High frequency stimulation of the subthalamic nucleus improves speed of locomotion but impairs forelimb movement in Parkinsonian rats

The subthalamic nucleus (STN) plays an important role in motor and non-motor behavior in Parkinson's disease, but its involvement in gait functions is largely unknown. In this study, we investigated the role of the STN on gait in a rat model of PD using the CatWalk method. Parkinsonian rats received bilateral high frequency stimulation (HFS) with different stimulation amplitudes of the STN. Rats were rendered parkinsonian by bilateral injections of 6-hydroxydopamine (6-OHDA) into the striatum. One group of 6-OHDA animals was implanted bilaterally with stimulation electrodes at the level of the STN. Stimulations were performed at 130 Hz (frequency), 60 micros (pulse width) and varying amplitudes of 0, 3, 30 and 150 microA. Rats were evaluated in an automated quantitative gait analysis method (CatWalk method). After behavioral evaluations, rats were killed and the brains processed for histological stainings to determine the impact of the dopaminergic lesion (tyrosine hydroxylase immunohistochemistry) and the localization of the electrode tip (hematoxylin-eosin histochemistry). Results show that bilateral 6-OHDA infusion significantly decreased (70%) the number of dopaminergic cells in the substantia nigra pars compacta (SNc). Due to 6-OHDA treatment, the gait parameters changed considerably. There was a general slowness. The most pronounced effects were seen at the level of the hind paws. Due to implantation of STN electrodes the step pattern changed. STN electrical stimulation improved the general slowness but induced slowing of the forelimb movement. Furthermore, we found that HFS with a medium amplitude significantly changed speed, the so-called dynamic aspect of gait. The static features of gait were only significantly influenced with low amplitude. Remarkably, STN stimulation affected predominantly the forepaws/limbs.

Differential effects on forelimb grasping behavior induced by fetal dopaminergic grafts in hemiparkinsonian rats

Skilled forelimb movements depend on an intact dopaminergic (DA) neurotransmission and are substantially impaired in the unilateral rat model of Parkinson's disease. It has remained unclear, however, to what extent reaching and grasping movements can be influenced by intrastriatal transplantation of fetal DA neurons. Here an extensive behavioral assessment of skilled forelimb movement patterns in hemiparkinsonian and DA-grafted rats was carried out. Good DA graft survival was accompanied by a compensation of drug-induced rotational asymmetries. Interestingly, skilled forelimb use was significantly improved in transplanted animals as compared to lesion-only animals in the staircase test. Qualitative analysis of single forelimb reaching movement components revealed dissociable patterns of graft effects: while some movement components in grafted animals improved, others remained unchanged or even deteriorated. These findings provide novel insights into the complex interactions of graft-derived restoration of DA neurotransmission and skilled forelimb behavior.

Validation studies of the human movement analysis panel for hand/arm performance

The human movement analysis panel (HMAP) measures separable components of arm motion and simple and complex finger coordination. HMAP testing takes 30min to administer. In separate experiments we have validated the HMAP against the standard grooved pegboard and measures of gait speed, and demonstrated important learning effects over both short durations of days, and longer intervals of months to years in normal subjects of different ages. Stepwise regression demonstrated the strongest correlation between the HMAP complex motor times and pegboard both-hand removal (R(2)=0.52, p=0.002 for dominant and R(2)=0.33, p=0.02 for non-dominant hands). The most consistent and sensitive measure of HMAP motor performance overall was the complex motor time. The HMAP is a short-duration, easily administered, objective quantitative test of motor function, with potential applications in aging, and in Parkinson's Disease and related motor disorders. The HMAP has a smaller version used in primates, so that measurements made in primate models of disease and its treatment are directly comparable to analogous clinical measurements made in the corresponding human disease.

A qualitative and quantitative analysis of skilled forelimb reaching impairment following intracerebral hemorrhage in rats

The Montoya staircase test is commonly used to measure skilled forelimb reaching ability in a number of brain injury and disease models, but little has been done to characterize the precise nature of the impairments observed after stroke. The present study used slow motion video-recording to analyze staircase reaching performance both qualitatively and quantitatively, and to precisely determine the components of fine forelimb motor function that are disturbed in the collagenase model of hemorrhagic stroke. Male Sprague-Dawley rats were trained to reach for pellets in the staircase task, and subjected to either striatal hemorrhage induced by microinjections of bacterial collagenase or sham surgery. Reaching performance was recorded and examined before surgery, and 2 and 4 weeks later. Impaired animals made fewer attempts and retrieved less pellets than did shams, especially from the lower steps. Interestingly, impaired animals were less able to retrieve a pellet even when the forepaw made contact with it. Detailed qualitative analysis determined that significant disturbances were most prominent in components of skilled reaching that involved fine manipulation of the distal muscles, especially the wrist and digits. While some components of the reaching impairment were found to partially recover at 4 weeks post-surgery, the impairments in these distal motor movements persisted and there was no significant improvement in overall success. These results suggest that the collagenase model of intracerebral hemorrhage produces a functional impairment that most severely affects fine control of the distal forelimb and paw.

Changes in the kinematic structure and non-kinematic features of movements during skilled reaching after stroke: a Laban Movement Analysis in two case studies

The purpose of this study was to adapt a universal language for human movement, Laban Movement Analysis (LMA), to capture the kinematic and non-kinematic aspects of movement in a reach-for-food task by subjects whose movements had been affected by stroke. Two control subjects, one stroke subject with internal capsule damage, and one subject with right posterior parietal stroke were video recorded while performing the reaching task. The movements of limb advancement, grasping the food, and limb withdrawal to place the food in the mouth, were notated using LMA. A scale, the Expressive Reaching Scale (ERS), was derived from the notation. All subjects completed the task; however, the stroke subjects displayed abnormalities in both the kinematic and non-kinematic aspects of movements during reaching with either limb. The most extensive impairments were in the contralateral-to-stroke limb and were most severe in the subject with internal capsule damage. The ERS rating scale may be a useful diagnosis and assessment tool.

Rat Models of Upper Extremity Impairment in Stroke

Stroke remains the leading cause of adult disability, with upper extremity motor impairments being the most prominent functional deficit in surviving stroke victims. The development of animal models of upper extremity dysfunction after stroke has enabled investigators to examine the neural mechanisms underlying rehabilitation-dependent motor recovery as well as the efficacy of various adjuvant therapies for enhancing recovery. Much of this research has focused on rat models of forelimb motor function after experimentally induced ischemic or hemorrhagic stroke. This article provides a review of several different methods for inducing stroke, including devascularization, photothrombosis, chemical vasoconstriction, and hemorrhagia. We also describe a battery of sensorimotor tasks for assessing forelimb motor function after stroke. The tasks range from measures of gross motor performance to fine object manipulation and kinematic movement analysis, and we offer a comparison of the sensitivity for revealing motor deficits and the amount of time required to administer each motor test. In addition, we discuss several important methodological issues, including the importance of testing on multiple tasks to characterize the nature of the impairments, establishing stable baseline prestroke motor performance measures, dissociating the effects of acute versus chronic testing, and verifying lesion location and size. Finally, we outline general considerations for conducting research using rat models of stroke and the role that these models should play in guiding clinical trials.

Stress affects hedonic responses but not reaching-grasping in Parkinson's disease

Stress can transiently increase motor symptoms of Parkinson's disease (PD), but it is unclear whether other behavioural changes associated with PD are also affected. We found that reaching-grasping was impaired in 19 PD patients compared with 19 matched controls, but these impairments were not amplified by stress. However, patients showed a stress-induced reduction of hedonic responses. Stress may amplify those impairments in PD that are not accessible to cognitive control.

Snakes as agents of evolutionary change in primate brains

Current hypotheses that use visually guided reaching and grasping to explain orbital convergence, visual specialization, and brain expansion in primates are open to question now that neurological evidence reveals no correlation between orbital convergence and the visual pathway in the brain that is associated with reaching and grasping. An alternative hypothesis proposed here posits that snakes were ultimately responsible for these defining primate characteristics. Snakes have a long, shared evolutionary existence with crown-group placental mammals and were likely to have been their first predators. Mammals are conservative in the structures of the brain that are involved in vigilance, fear, and learning and memory associated with fearful stimuli, e.g., predators. Some of these areas have expanded in primates and are more strongly connected to visual systems. However, primates vary in the extent of brain expansion. This variation is coincident with variation in evolutionary co-existence with the more recently evolved venomous snakes. Malagasy prosimians have never co-existed with venomous snakes, New World monkeys (platyrrhines) have had interrupted co-existence with venomous snakes, and Old World monkeys and apes (catarrhines) have had continuous co-existence with venomous snakes. The koniocellular visual pathway, arising from the retina and connecting to the lateral geniculate nucleus, the superior colliculus, and the pulvinar, has expanded along with the parvocellular pathway, a visual pathway that is involved with color and object recognition. I suggest that expansion of these pathways co-occurred, with the koniocellular pathway being crucially involved (among other tasks) in pre-attentional visual detection of fearful stimuli, including snakes, and the parvocellular pathway being involved (among other tasks) in protecting the brain from increasingly greater metabolic demands to evolve the neural capacity to detect such stimuli quickly. A diet that included fruits or nectar (though not to the exclusion of arthropods), which provided sugars as a neuroprotectant, may have been a required preadaptation for the expansion of such metabolically active brains. Taxonomic differences in evolutionary exposure to venomous snakes are associated with similar taxonomic differences in rates of evolution in cytochrome oxidase genes and in the metabolic activity of cytochrome oxidase proteins in at least some visual areas in the brains of primates. Raptors that specialize in eating snakes have larger eyes and greater binocularity than more generalized raptors, and provide non-mammalian models for snakes as a selective pressure on primate visual systems. These models, along with evidence from paleobiogeography, neuroscience, ecology, behavior, and immunology, suggest that the evolutionary arms race begun by constrictors early in mammalian evolution continued with venomous snakes. Whereas other mammals responded by evolving physiological resistance to snake venoms, anthropoids responded by enhancing their ability to detect snakes visually before the strike.

Behavioral recovery from unilateral photothrombotic infarcts of the forelimb sensorimotor cortex in rats: Role of the contralateral cortex

During sensorimotor recovery following stroke ipsi- and contralesional alterations in brain function have been characterized in patients as well as animal models of focal ischemia, but the contribution of these bilateral processes to the functional improvement is only poorly understood. Here we examined the role of the homotopic contralateral cortex for sensorimotor recovery after focal ischemic infarcts at different time periods after the insult. One group of animals received a unilateral single photothrombotic infarct in the forelimb sensorimotor cortex, while four additional groups received a second lesion in the contralateral homotopic cortex either immediately or 2 days, 7 days, or 10 days after the first infarct. The time course of functional recovery of the impaired forelimbs was assessed using different sensorimotor scores: forelimb-activity during exploratory behavior and frequency of forelimb-sliding in the glass cylinder as well as forelimb misplacement during grid walking. Focal infarcts in the forelimb sensorimotor cortex area significantly impaired the function of the contralateral forelimb in these different behavioral tests. The subsequent damage of the contralateral homotopic forelimb sensorimotor cortex only affected the forelimb opposite to the new lesion but did not reinstate the original deficit. The time course of sensorimotor recovery after bilateral sequential cortical infarcts did not significantly differ from animals with unilateral single lesions. These data indicate that following small ischemic cortical infarcts in the forelimb sensorimotor cortex the contralateral cortex homotopic to the lesion plays only a minor role for functional recovery.

Motor Deficits in Parkinsonian Reaching: Dopa-Sensitivity Influenced by Real-World Task Constraint

Parkinson's disease (PD) patients can perform many daily activities, but movement deficits are evident. Those deficits may be increased when the required movement is constrained in accuracy. Variable improvements in performance with PD medication have been demonstrated, and sensitivity to task constraint has been evident in some studies. The authors quantified both specific movement deficits and improvements for PD patients in a reaching task. PD patients (N=8) both on and off medication showed a need for greater ongoing control in movements with higher task-accuracy constraints. Increased task-accuracy constraints further compromised movement timing and structure among PD patients who were off medication, suggesting that unmedicated PD patients may typically compensate by using more conscious control of movement, resulting in increased slowing and segmentation of components when higher task accuracy is required.

Dietary restriction alters fine motor function in rats

A number of standard behavioral tasks in animal research utilize food rewards for positive reinforcement. In order to enhance the motivation to participate in these tasks, animals are usually placed on a restricted diet. While dietary restriction (DR) has been shown to have beneficial effects on recovery after brain injury, life span and aging processes, it might also represent a stressor. Since stress can influence a broad range of behaviors, the purpose of this study was to assess whether DR may have similar effects on skilled movement. Adult male Long-Evans rats were trained and tested in a skilled reaching task both prior to and during a mild food restriction regimen that maintained their body weights at 90-95% of baseline weight for eight days. The observations revealed that DR decreased reaching success and increased the number of attempts to grasp a single food pellet. The animals appeared to be more frantic when attempting to reach for food pellets, and the time taken to reach for 20 pellets decreased following the onset of DR. A second experiment investigating behaviors that do not require food rewards, including a ladder rung walking task and an open field test, confirmed that rats on DR display deficits in skilled movements and are hyperactive. These findings suggest that results obtained in motor tasks using food rewards need to be interpreted with caution. The findings are discussed with respect to stress associated with DR.

The unilateral 6-OHDA rat model of Parkinson's disease revisited: an electromyographic and behavioural analysis

The characteristic locomotor disturbances of Parkinson's disease (PD) include shuffling gait, short steps and low walking velocity. In this study we investigated features of walking and turning in a rat model of PD caused by unilateral infusion of the neurotoxin 6-hydroxydopamine (6-OHDA). We assessed gait and electromyographic (EMG) patterns of the ankle flexor tibialis anterior and the knee extensor vastus lateralis of the hindlimb, and triceps brachii of the forelimb, during overground locomotion, spontaneous rotation (turning) and apomorphine-induced rotation. When compared with control rats, rats with unilateral dopamine depletion displayed a shuffling gait and short stride lengths. This locomotor pattern was accompanied by prolonged ankle flexor activity on the ipsilateral side, and prolonged activity of knee extensors on the contralateral side. The dopamine depletion also led to enhanced contraversive rotations after an apomorphine challenge. The EMG recordings during drug-induced rotation suggested that hindlimb stepping was a reflective response to an active drive produced by forelimbs. The EMG recordings of the contralateral side during rotation were marked by reduced ankle flexor activity and increased knee extensor activity. Furthermore, EMG recordings indicated that dopamine-agonists induce rotational bias by altering the coupling between ipsi- and contralateral hindlimbs, and between forelimbs. In straight walking, however, the gait of 6-OHDA lesion animals reflected normal, coupled hindlimb stepping as controlled by spinal pattern generators. The data suggest that the unilateral rat model of PD resembles key features of human parkinsonian gait, and that asymmetric descending input may underlie the observed changes in gait patterns.

Pallidal deep brain stimulation and L-dopa do not improve qualitative aspects of skilled reaching in Parkinson's disease

OBJECTIVE

To determine effects of dopaminergic medication and pallidal deep brain stimulation (DBS) on skilled reach in Parkinson's disease (PD).

BACKGROUND

PD is a neurodegenerative disorder affecting motor control. While speed and execution of movements are improved by L-dopa, not all motor symptoms are alleviated. Little is known about the effects of DBS or medication on reaching.

DESIGN METHOD

Eight PD patients with unilateral pallidal DBS reached with the contra-lateral hand for a piece of food, placing it in the mouth, and returning to starting position. Testing was performed on no treatment, medication only, DBS only, and combined treatment. Reaches were digitally recorded and analyzed on a 21 point scale adapted from Eshkol-Wachman Notation. Analysis was blinded, with patients compared to age-matched controls.

RESULTS

Patients were tested 6-13 months after surgery. All showed significant improvement clinically and in UPDRS (III) scores. The following data were obtained on the reaching scale: normal controls 16.5-21.0 (mean 18.3), no treatment 3.0-12.5 (mean 7.4), medication only 7.0-14.0 (mean 10.3), DBS only 4.5-16.0 (mean 9.2), combined treatment 4.0-15.0 (mean 9.5). The difference between controls and all treatment groups was statistically significant (P<0.005). All aspects of reach were compromised. No significant differences were found among the four conditions.

CONCLUSIONS

This study is consistent with accumulating evidence that some aspects of motor performance in PD patients, such as reaching, are resistant to L-dopa. Also, pallidal DBS does not improve those parameters that are resistant to L-dopa, either alone or in combination with medication.

Age-dependent motor deficits and dopaminergic dysfunction in DJ-1 null mice

Mutations in the DJ-1 gene were recently identified in an autosomal recessive form of early-onset familial Parkinson disease. Structural biology, biochemistry, and cell biology studies have suggested potential functions of DJ-1 in oxidative stress, protein folding, and degradation pathways. However, animal models are needed to determine whether and how loss of DJ-1 function leads to Parkinson disease. We have generated DJ-1 null mice with a mutation that resembles the large deletion mutation reported in patients. Our behavioral analyses indicated that DJ-1 deficiency led to age-dependent and task-dependent motoric behavioral deficits that are detectable by 5 months of age. Unbiased stereological studies did not find obvious dopamine neuron loss in 6-month- and 11-month-old mice. Neurochemical examination revealed significant changes in striatal dopaminergic function consisting of increased dopamine reuptake rates and elevated tissue dopamine content. These data represent the in vivo evidence that loss of DJ-1 function alters nigrostriatal dopaminergic function and produces motor deficits.

Preserved ipsilateral-to-lesion motor map organization in the unilateral 6-OHDA-treated rat model of Parkinson's disease

The classic view of dopamine (DA) loss in Parkinson's disease is that it produces a functional deafferentation in striatal-cortical circuitry that, in turn, contributes to sensorimotor deficits. The present study examines this view in the rat by assessing how DA-depletion affects the intracortical microstimulation (ICMS) topographic representation of movement in the rostral and caudal motor areas of the motor cortex. The ICMS map is used as an index of motor cortex function because it has been shown to reflect motor function and experience. Groups of rats received no training or skilled reach training and were then given unilateral 6-hydroxydopamine (6-OHDA) or sham lesions of the nigrostriatal bundle to deplete nigrostriatal DA. Lesion success was confirmed by abnormalities in skilled reaching, by apomorphine-induced rotation, and by loss of DA neurons in the substantia nigra. The size and threshold of the motor map in naive and skilled reach trained DA-depleted rats were preserved. In addition, there was an increase in distal limb representation in the caudal forelimb area (CFA) in the DA-depleted rats suggesting a possible plastic response to the behavioral effects of DA-depletion. The presence of preserved size and modified map organization in DA-depleted rats is discussed in relation to the hypothesis that preserved motor cortex functionality despite DA loss underlies the spared motor abilities of DA-depleted rats.

Precision grasps of children and young and old adults: individual differences in digit contact strategy, purchase pattern, and digit posture

The evolutionary origins and variations of the precision grip, in which an object is held between the thumb and other digits, are poorly understood. This is surprising because the neural basis of this grasp pattern, including the motor cortex and pyramidal tract have received extensive study. Most previous work has shown that features of an object to be grasped (external factors) determine grasp patterns. The objective of the present study was to investigate individual differences (central factors) in use of the pincer and other precision grips. The grasping patterns of male and female young adults, older adults and children were examined as they reached (with both left and right hand) for five small beads (3-16 mm diameter). Frame-by-frame analysis of grasping indicated a high degree of variability in digit contact strategies, purchase patterns and digit posture both within and between subjects. (1) The contact strategies consisted of five variations, depending on whether the thumb or the index finger dragged or stabilized the bead for grasping. (2) Purchase patterns consisted of seven different types of precision grips, involving the thumb and various combinations of other digits. (3) There were four variations stemming from the posture of the non-grasping digits. Grip patterns of the left and right hands were correlated in individual subjects, as were strategies used for different bead sizes. Females displayed slightly more variability in grasp patterns than did males, and digit width (obtained from photocopies of the subjects' hands) was weakly correlated with the grasp patterns used. Although it was expected that the pincer would be used for all objects, it was preferentially used for only the smallest object except for older adults who used the pincer grasp on most objects. The variability in digit contact strategies, purchase patterns, and posture of the non-grasping digits indicates that central factors (innate or learning-induced architecture of the left parietal cortex) make important contributions to the selection of a grasping pattern. These individual differences are discussed in relation to the neural control of grasping and its potential contribution to understanding the evolution, development, and pathology of the precision grip.