Bimanual force control strategies in chronic stroke: Finger extension versus power grip

Stroke leads to motor asymmetries in the flexor and extensor muscles of the hand. Typically, the strength deficits in the extensors are greater than the flexors. The impact of differential motor abilities of these muscle groups on the execution of bimanual force control tasks in individuals with stroke is unknown. The primary purpose of this study was to determine the influence of task constraints on visually guided bimanual force control in chronic stroke. Stroke survivors and age-matched individuals performed bimanual isometric contractions for 20s to match target submaximal force levels. Online visual feedback of the total force (sum of the forces produced by both hands) was provided. The task constraints were manipulated by (a) finger extension, and (b) finger flexion (power grip). Force asymmetry was indexed by the proportion of force contributed by the paretic hand to the total force. The stroke group demonstrated task-specific asymmetry in bimanual force control. Specifically, the paretic hand contributed less force than the non-paretic hand in finger extension whereas this relationship was reversed in power grip. Importantly, regardless of the nature of the task, reduction in motor impairments was associated with increased symmetry and coordination in bimanual tasks. Further, bimanual submaximal grip force control revealed asymmetry and coordination deficits that are not identified by investigating bimanual maximal force production alone. The motor control strategy adopted to optimize performance on bimanual tasks revealed the altered force production of the paretic hand due to the combined effect of extensor weakness and enhanced flexor bias following stroke. Bimanual asymmetries in stroke survivors highlight the need for identifying and treating the task-specific impairments for maximizing motor recovery post stroke.     

White matter microstructural organisation of interhemispheric pathways predicts different stages of bimanual coordination learning in young and older adults

The ability to learn new motor skills is crucial for activities of daily living, especially in older adults. Previous work in younger adults has indicated fast and slow stages for motor learning that were associated with changes in functional interactions within and between brain hemispheres. However, the impact of the structural scaffolds of these functional interactions on different stages of motor learning remains elusive. Using diffusion‐weighted imaging and probabilistic constrained spherical deconvolution‐based tractography, we reconstructed transcallosal white matter pathways between the left and right primary motor cortices (M1–M1), left dorsal premotor cortex and right primary motor cortex (LPMd–RM1) and right dorsal premotor cortex and left primary motor cortex (RPMd–LM1) in younger and older adults trained in a set of bimanual coordination tasks. We used fractional anisotropy (FA) to assess microstructural organisation of the reconstructed white matter pathways. Older adults showed lower behavioural performance than younger adults and improved their performance more in the fast but less in the slow stage of learning. Linear mixed models predicted that individuals with higher FA of M1–M1 pathways improve more in the fast but less in the slow stage of bimanual learning. Individuals with higher FA of RPMd–LM1 improve more in the slow but less in the fast stage of bimanual learning. These predictions did not differ significantly between younger and older adults suggesting that, in both younger and older adults, the M1–M1 and RPMd–LM1 pathways are important for the fast and slow stage of bimanual learning, respectively.     

Bimanual coordination in alcohol-exposed children: role of the corpus callosum.

The corpus callosum (CC) is one of several brain structures affected in children prenatally exposed to alcohol. This structure plays a major role in coordinating motor activity from opposite sides of the body, and deficits in bimanual coordination have been documented in individuals with agenesis of or damage to the CC, particularly when the task is performed without visual feedback. The Bimanual Coordination Test was used to assess speed and accuracy on a task where both hands must coordinate to guide a cursor through angled pathways providing measures of interhemispheric interaction or the ability of the two hemispheres to coordinate activity via the corpus callosum. Twenty-one children with fetal alcohol spectrum disorders (FASD) and 17 non-exposed control children (CON), matched closely in age, sex, and ethnicity were tested. For trials with visual feedback (WV), children with FASD were slower than CON children but were equally accurate. Although statistically significant group differences were not observed on most trials completed without visual feedback (WOV), accuracy of the FASD group on WOV trials was highly variable. Group differences in accuracy on WOV angles approached significance after accounting for performance on the WV angles, and children with FASD were significantly less accurate on an individual angle believed to be particularly sensitive to interhemispheric interaction. These results indicate that children with FASD are slower than CON children but equally accurate on basic visuomotor tasks. However, as task complexity and reliance on interhemispheric interaction increases, children with FASD demonstrate variable and inaccurate performance.     

The relationship between visual orienting and interlimb synchrony in a patient with a superior parietal infarction: A case study

Much work indicates that parietal cortex mediates the transformation of visual information into the motor commands necessary for successful performance of many unimanual tasks. Accumulating evidence suggests that parietal cortex also mediates the coordination of bimanual movements, during which the natural tendency is to couple the limbs temporally. However, the extent to which parietal oculomotor and/or visual processes contribute to temporal coupling of the limbs during bimanual task performance is unknown. In the current study, we monitored the eye movements of a patient with a left parietal infarction as she performed a series of bimanual visuomotor tasks. We demonstrate the impact of an ipsilesional (leftward) orientation bias on her ability to synchronize the onset of bimanual limb movements; the movements were performed in serial fashion, i.e., left limb before right, when the patient was permitted to freely shift saccades and the visual target cuing the left (ipsilesional) limb movement was presented at greater (leftward) eccentricities. Disruption of interlimb synchrony as such was not, however, evident when the patient was required to fixate or when visual targets were presented at lesser ipsilesional eccentricities. Additionally, despite the disruptive influence of oculomotor and visual factors on interlimb synchrony, the patient appeared capable of using visual feedback to straighten the right (contralesional) limb trajectory, thus improving the spatial component of task performance. Results suggest that parietal cortex plays an important role in the coordination of limb movements during performance of bimanual visuomotor tasks. This role appears to involve orienting gaze or attention to the goals of each limb so that the nervous system can synchronize the activity of both limbs and thereby ensure successful task completion.     

Bimanual coordination: neuromagnetic and behavioral data

It has been suggested that bimanual coordination is associated with stronger activation of the left motor cortex in right-handers. The aim of the present study was to investigate whether left motor cortex dominance constitutes a fundamental feature of bimanual coordination. We investigated neuromagnetic responses while subjects performed a bimanual tapping task using a 122-channel whole-head neuromagnetometer. Three neuromagnetic sources localized in the primary sensorimotor cortex of each hemisphere were found. Sources represent neuromagnetic correlates of the motor command and of somatosensory feedback. Since we found no differences of amplitudes or latencies of corresponding sources of both hemispheres, our data suggest that dominance of the left motor cortex is not a fundamental characteristic for bimanual coordination.     

High resolution spatiotemporal analysis of the contingent negative variation in simple or complex motor tasks and a non-motor task.

OBJECTIVES: Since the characteristics of the Bereitschaftspotential (BP) - voluntary movement paradigm of internally-driven movements - have been established recently by our group using high resolution DC-EEG techniques, it was of great interest to apply similar techniques to the other slow brain potential--contingent negative variation (CNV) of externally-cued movements--with the same motor tasks using the same subjects. METHODS: The CNV for simple bimanual sequential movements (task 1), complex bimanual sequential movements (task 2) and a non-motor condition (task 3) was recorded on the scalp using a 64 channel DC-EEG in 16 healthy subjects, and the data were analyzed with high resolution spatiotemporal statistics and current source density (CSD). RESULTS: (1) The CNV was distributed over frontal, frontocentral, central and centroparietal regions; a negative potential was found at the frontal pole and a positive potential was found over occipital regions. (2) CNV amplitudes were higher for task 2 than for task 1, and there was no late CNV for task 3. (3) A high resolution spatiotemporal analysis revealed that during the early CNV component, statistical differences existed between the motor tasks (tasks 1 and 2) and the non-motor task (task 3), which occurred at frontocentral, central, centroparietal, parietal and parieto-occipital regions. During the late CNV component, additional significant differences were found not only between the motor tasks and the non-motor task but also between motor task 1 and task 2 at frontocentral, central and centroparietal regions. (4) Comparison of the CNV between the frontomesial cortex (situated over the supplementary/cingulate areas, SCMA) and both lateral pre-central areas (situated over the primary motor areas, MIs) showed that there was no statistically significant difference between the two cortical motor areas except for the early CNV. (5) Comparison of the CNV between the 3 tasks over the cortical motor areas showed that there were significant differences between the motor tasks and the non-motor task regarding the auditory evoked potential (AEP) and the early CNV component, and between all 3 tasks in the late CNV, the visual evoked potential (VEP(2)) and the N-P component. (6) The ranges and the densities of the CSD maps were larger and higher for complex than for simple tasks. The current sinks of the AEP and the early CNV were located at Fz, the late CNV at FCz and surrounding regions. As to be expected, current sources of the VEPs were located at the occipital lobes. The CNV was a current sink (negative) except for the VEP's main component which was a current source (positive). CONCLUSIONS: (1) The CNV topography over the scalp varied with the complexity of motor tasks and between motor and non-motor conditions. (2) The origin of the early CNV may rest in the frontal lobes, while the late CNV may stem from more extensive cortical areas including SCMA, MIs, etc. (3) The late CNV component is not identical with the BP.     

Asymmetric transcallosal conduction delay leads to finer bimanual coordination

It has been theorized that hemispheric dominance and more segregated information processing have evolved to overcome long conduction delays through the corpus callosum (transcallosal conduction delay - TCD) but that this may still impact behavioral performance, mostly in tasks requiring high timing accuracy. Nevertheless, a thorough understanding of the temporal features of interhemispheric communication is lacking.Here, we aimed to assess the relationship between TCD and behavioral performance with a noninvasive directional cortical measure of TCD obtained from transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) in the motor system.Twenty-one healthy right-handed subjects were tested. TEPs were recorded during an ipsilateral silent period (iSP) paradigm and integrated with diffusion tensor imaging (DTI) and an in-phase bimanual thumb-opposition task. Linear mixed models were applied to test relationships between measures.We found TEP indexes of transcallosal communication at ∼15 ms both after primary motor cortex stimulation (M1-P15) and after dorsal premotor cortex stimulation (dPMC-P15). Both M1-and dPMC-P15 were predicted by mean diffusivity in the callosal body. Moreover, M1-P15 was positively related to iSP. Importantly, M1-P15 latency was linked to bimanual coordination with direction-dependent effects, so that asymmetric TCD was the best predictor of bimanual coordination.Our findings support the idea that transcallosal timing in signal transmission is essential for interhemispheric communication and can impact the final behavioral outcome. However, they challenge the view that a short conduction delay is always beneficial. Rather, they suggest that the effect of the conduction delay may depend on the direction of information flow.     

Dual-task interference during initial learning of a new motor task results from competition for the same brain areas

Cerebral patterns of activity elicited by dual-task performance throughout the learning of a complex bimanual coordination pattern were addressed. Subjects (N = 12) were trained on the coordination pattern and scanned using fMRI at early (PRE) and late (POST) learning stages. During scanning, the coordination pattern was performed either as a single task or in concurrence with a simultaneous visual search task (i.e. dual task). Kinematics data revealed a significant performance improvement as a result of learning. In PRE-scanning, the dual-task condition induced deterioration of motor performance, relative to the single-task condition. Activity in lateral frontal and parietal regions involved in both visual search and motor coordination tasks (i.e. ‘overlapping’ regions) was reduced when the tasks were performed simultaneously. In POST-scanning, kinematics performance was equivalent under single- and dual-task conditions, suggesting automaticity of the coordination pattern. Furthermore, overlap between regions involved in visual search and motor tasks was reduced, and dual-task performance was no longer associated with reduction of frontal and parietal activity. Our results suggest that behavioral interference between a complex motor coordination task and a simple simultaneous visual search task occurs when both tasks recruit overlapping regions in the frontal and parietal cortices. This may provide a neural basis for dissipation of dual-task interference following extensive motor practice, which is a traditional behavioral marker of motor automaticity.     

Bimanual coordination deficits in attention deficit/hyperactivity disorder (ADHD)

Although motor difficulties have been implicated in ADHD, studies investigating bimanual coordination have been few and their results inconsistent. This study examined the performance of 12 boys with ADHD combined type and their matched controls on a simple in-phase bimanual movement task (requiring symmetrical hand movements) and a complex out-of-phase bimanual movement task (requiring asymmetrical hand movements), at different designated speeds (1 and 2 Hz). Compared to controls, ADHD children were significantly more variable in both velocity and coordination, and less accurate in coordination, with the in-phase movements. For out-of-phase movements, the ADHD children were significantly more variable in velocity and coordination. These findings suggest a problem of bimanual coordination in the syndrome.     

Reversal of handedness effects on bimanual coordination in adults with Down syndrome

Background Research on unimanual tasks suggested that motor asymmetries between hands may be reduced in people with Down syndrome. Our study examined handedness (as assessed by hand performance) and perceptual–motor integration effects on bimanual coordination. Methods Adults with Down syndrome (13 non‐right‐handed, 22 right‐handed), along with comparison groups of adults (16 non‐right‐handed, 21 right‐handed) and children (15 non‐right‐handed, 22 right‐handed) without Down syndrome, drummed with auditory, verbal and visual instructions. Results In contrast to handedness effects in the children and adults without Down syndrome, right‐handed participants with Down syndrome led more with the left hand, and had lower coordination stability than non‐right‐handed participants with Down syndrome. Conclusions The reversed handedness effect during bimanual coordination suggests a complex relationship between handedness and task requirements in adults with Down syndrome.     

Bimanual coordination dysfunction in early, untreated Parkinson's disease

Bimanual coordination involves the simultaneous performance of either symmetrical (in-phase) or asymmetrical (anti-phase) movements with both hands and is known to be impaired in Parkinson's disease (PD). At present, it is unclear whether this aspect of motor function is already impaired in early stage, untreated PD patients. Therefore, we investigated the accuracy of bimanual coordination in 13 early stage, untreated PD patients and 13 age- and sex-matched healthy controls. Each subject performed bimanual coordination tasks at two different movement frequencies (1 and 1.75 Hz) and with two different phase relationships (in-phase and anti-phase). The percentage of unsuccessful trials (as a measure of overall task performance) in PD patients was significantly higher than in healthy subjects. PD patients performed high frequency in-phase and anti-phase bimanual coordination tasks less accurately with their non-dominant hand than healthy subjects. Furthermore, PD patients had more difficulty than healthy subjects in maintaining a constant phase relationship between the hands in the anti-phase condition at low movement frequency. This study demonstrates that bimanual coordination dysfunction is a very early sign of PD. Bimanual coordination tasks, in particular those involving high frequency anti-phase movements, might prove useful in the early diagnosis of PD.     

Motor skill performance of school-age children with visual impairments

The aim of this study was to examine the performance of children with visual impairments (VI) aged 7 to 10 years on different types of motor skills. Furthermore, the association between the degree of the VI and motor performance was examined. The motor performance of 48 children with VI (32 males, 16 females; mean age 8y 10mo [SD 1y 1mo]) was assessed using the Movement Assessment Battery for Children (MABC). Their performance was compared with 48 children without VI (33 males, 15 females; mean age 8y 9mo [SD 1y 1mo]). Children with VI showed the poorest performance compared with peers without VI on unimanual speed, eye-hand coordination, catching, static balance, and dynamic balance while moving slowly. There was no significant difference between children with moderate and severe VI, except for bimanual coordination in 7- to 8-year-olds and eye-hand coordination in both the 7- to 8-year-olds and 9- to 10-year-olds, favouring the children with moderate VI. The poor performance compared with children without VI is related to vision, but the degree of the VI does not appear to relate to motor performance, except when associated with bimanual and eye-hand coordination. For children with VI, it seems very important to adjust the environmental context and task to enhance motor performance.     

Early stages in the acquisition of a bimanual motor skill

Children and adults were trained and tested on a coordinated bimanual task that required them to rotate both hands either at the same or at different angular velocities in order to move the pen of an X-Y recorder along three angles of slant (45, 67 and 22 degrees), and to rotate both hands in the same clockwise direction rather than as mirror image movements. Initially both groups exhibited a tendency to rotate both hands at the same angular velocity even when the task required differential motor output from the two hands. With visual feedback, the tendency toward synchronization, such that both hands moved at the same angular velocity, was asymmetrically distributed, but under blindfolded conditions such asymmetries disappeared. Accuracy of performance increased with practice; and visual feedback enhanced accuracy of performance. The findings suggest that during early stages in the acquisition of a bimanual skill, unintended bilateral coactivation occurs at multiple levels of motor organization; mirror associated movements are only one simple subset of unintentional intermanual synergies.     

Cerebellar mediation of the complexity of bimanual compared to unimanual movements.

OBJECTIVE: To study rapidly alternating movements under fMRI in order to identify the brain regions that mediate increased complexity in bimanual vs unimanual movements and to verify the localization of a clinical test of limb ataxia (diadochokinesis). METHODS: Unimanual and bimanual movements, that is, palm(s) pronated then supinated, served as stimulation in a block design fMRI investigation at 1.5 T. Analyses compared bimanual movements and rest for each hand separately and the unimanual conditions combined. A pronation/supination task was chosen as it provides the same objective motor output during unimanual and bimanual formats. The increased coordination demand of the bimanual format (phase/antiphase movements) was expected to result in distinct activation in supplementary motor, primary motor, prefrontal, and cerebellar regions. RESULTS: The bimanual task uniquely elicited responses in specific anterior medial and posterior (vermal) cerebellar regions. CONCLUSIONS: The study corroborated clinical use of diadochokinesis tasks to test for aspects of cerebellar integrity. The data do not support the literature emphasizing basal ganglia mediation of this type of coordinated movement. Cerebellar medial and vermal regions (in connection with central nuclei) are proposed as the locus within the cerebellum for mediating complexity, that is, the effective integration of separate limb movements that proceed in an asynchronous but systematic fashion.     

Mirror visual feedback induces lower neuromuscular activity in children with spastic hemiparetic cerebral palsy

The study examined the effects of mirror feedback information on neuromuscular activation during bimanual coordination in eight children with spastic hemiparetic cerebral palsy (SHCP) and a matched control group. The ‘mirror box’ creates a visual illusion, which gives rise to a visual perception of a zero lag, symmetric movement between the two arms. The study incorporated two additional visual feedback conditions by placing a glass or opaque screen between the arms. During bilateral symmetric circular arm movements mirror visual feedback induced lower neuromuscular intensities in the shoulder muscles of the less impaired arm of children with SHCP compared to the other visual conditions. In addition, the mirror lead to shorter relative durations of eccentric and concentric activity in the elbow muscles of the more impaired arm, whereas no effects of visual feedback were found in a matched control group. These results suggest that replacing veridical visual information of the more impaired arm with a mirror reflection of the less impaired arm improves the motor control of children with SHCP during interlimb coupling. The effects of the availability of visual feedback in individuals with hemiparesis are discussed with reference to: (1) increase ipsilateral motor cortex excitability and (2) congruence between afferent (visual) feedback and the internal copy of the motor commands.     

Learned control of inter‐hemispheric connectivity: Effects on bimanual motor performance

Bimanual movements involve the interactions between both primary motor cortices. These interactions are assumed to involve phase‐locked oscillatory brain activity referred to as inter‐hemispheric functional coupling. So far, inter‐hemispheric functional coupling has been investigated as a function of motor performance. These studies report mostly a negative correlation between the performance in motor tasks and the strength of functional coupling. However, correlation might not reflect a causal relationship. To overcome this limitation, we opted for an alternative approach by manipulating the strength of inter‐hemispheric functional coupling and assessing bimanual motor performance as a dependent variable. We hypothesize that an increase/decrease of functional coupling deteriorates/facilitates motor performance in an out‐of‐phase bimanual finger‐tapping task. Healthy individuals were trained to volitionally regulate functional coupling in an operant conditioning paradigm using real‐time magnetoencephalography neurofeedback. During operant conditioning, two discriminative stimuli were associated with upregulation and downregulation of functional coupling. Effects of training were assessed by comparing motor performance prior to (pre‐test) and after the training (post‐test). Participants receiving contingent feedback learned to upregulate and downregulate functional coupling. Comparing motor performance, as indexed by the ratio of tapping speed for upregulation versus downregulation trials, no change was found in the control group between pre‐ and post‐test. In contrast, the group receiving contingent feedback evidenced a significant decrease of the ratio implicating lower tapping speed with stronger functional coupling. Results point toward a causal role of inter‐hemispheric functional coupling for the performance in bimanual tasks. Hum Brain Mapp 38:4353–4369, 2017. © 2017 Wiley Periodicals, Inc.     

Callosal degeneration topographically correlated with cognitive function in amnestic mild cognitive impairment and alzheimer's disease dementia

Degeneration of the corpus callosum (CC) is evident in the pathogenesis of Alzheimer's disease (AD). However, the correlation of microstructural damage in the CC on the cognitive performance of patients with amnestic mild cognitive impairment (aMCI) and AD dementia is undetermined. We enrolled 26 normal controls, 24 patients with AD dementia, and 40 single‐domain aMCI patients with at least grade 1 hippocampal atrophy and isolated memory impairment. Diffusion tensor imaging (DTI) with fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (DA), and radial diffusivity (DR) were measured. The entire CC was parcellated based on fiber trajectories to specific cortical Brodmann areas using a probabilistic tractography method. The relationship between the DTI measures in the subregions of the CC and cognitive performance was examined. Although the callosal degeneration in the patients with aMCI was less extended than in the patients with AD dementia, degeneration was already exhibited in several subregions of the CC at the aMCI stage. Scores of various neuropsychological tests were correlated to the severity of microstructural changes in the subregional CC connecting to functionally corresponding cortical regions. Our results confirm that CC degeneration is noticeable as early as the aMCI stage of AD and the disconnection of the CC subregional fibers to the corresponding Brodmann areas has an apparent impact on the related cognitive performance. Hum Brain Mapp 35:1529–1543, 2014. © 2013 Wiley Periodicals, Inc.     

“Can touch this”: Cross‐modal shape categorization performance is associated with microstructural characteristics of white matter association pathways

Previous studies on visuo‐haptic shape processing provide evidence that visually learned shape information can transfer to the haptic domain. In particular, recent neuroimaging studies have shown that visually learned novel objects that were haptically tested recruited parts of the ventral pathway from early visual cortex to the temporal lobe. Interestingly, in such tasks considerable individual variation in cross‐modal transfer performance was observed. Here, we investigate whether this individual variation may be reflected in microstructural characteristics of white‐matter (WM) pathways. We first trained participants on a fine‐grained categorization task of novel shapes in the visual domain, followed by a haptic categorization test. We then correlated visual training‐performance and haptic test‐performance, as well as performance on a symbol‐coding task requiring visuo‐motor dexterity with microstructural properties of WM bundles potentially involved in visuo‐haptic processing (the inferior longitudinal fasciculus [ILF], the fronto‐temporal part of the superior longitudinal fasciculus [SLF_ft] and the vertical occipital fasciculus [VOF]). Behavioral results showed that haptic categorization performance was good on average but exhibited large inter‐individual variability. Haptic performance also was correlated with performance in the symbol‐coding task. WM analyses showed that fast visual learners exhibited higher fractional anisotropy (FA) in left SLF_ft and left VOF. Importantly, haptic test‐performance (and symbol‐coding performance) correlated with FA in ILF and with axial diffusivity in SLF_ft. These findings provide clear evidence that individual variation in visuo‐haptic performance can be linked to microstructural characteristics of WM pathways. Hum Brain Mapp 38:842–854, 2017. © 2016 Wiley Periodicals, Inc.     

Alpha band power changes in unimanual and bimanual sequential movements, and during motor transitions.

OBJECTIVE: To investigate the cortical activation during execution of unimanual and bimanual synchronous and asynchronous finger sequences, as well as during transitions between those sequences. METHODS: Task-related power (TRPow) analysis of multichannel surface EEG was used to examine the regional oscillatory brain activity in the lower (7.8-9.8 Hz) and upper (10.8-11.8 Hz) alpha band. Unimanual to bimanual, bimanual to unimanual, and unimanual to unimanual transitions, prompted by visual cues, were studied in 10 right handed subjects. RESULTS: (1) Execution of unimanual and bimanual movements was accompanied by a bilateral activation over the central regions. (2) The 7.8-9.8 Hz TRPow decrease was more prominent for left and bimanual movements, suggesting sensitivity of the lower alpha band to task difficulty. (3) No difference in alpha oscillatory activity was found between bimanual synchronous and asynchronous sequences. (4) Transitions between motor sequences were invariably accompanied by a mesioparietal TRPow decrease in the lower alpha band. (5) This mesioparietal activation was contingent to the change of motor program, and could not be accounted for by the change of visual cue, or related attentional processes. CONCLUSION: The 7.8-9.8 Hz mesioparietal activation most likely reflects a posterior parietal motor command initiating transition between motor programs.     

Scopolamine alters rhesus monkey performance on a novel neuropsychological test battery.

Rhesus monkeys (6) were trained on a test battery including cognitive tests adapted from a human neuropsychological assessment battery (CANTAB; CeNeS, Cambridge, UK) as well as a bimanual motor skill task. The complete battery included tests of memory (delayed non-match to sample, DNMS; self-ordered spatial search, SOSS), reaction time (RT), motivation (progressive ratio; PR) and fine motor coordination (bimanual). The animals were trained to asymptotic performance in all tasks and then were administered two of the four CANTAB tasks on alternate weekdays (PR/SWM; DNMS/RT) with the bimanual task being administered on each weekday. The effect of acute administration of scopolamine (3-24 microg/kg, i.m.) on performance was then determined. Although performance on DNMS was impaired there was no interaction of drug treatment with retention interval, suggesting that scopolamine does not increase the rate of forgetting in this task. Scopolamine administration produced a decrement in SOSS performance that was dependent on task difficulty as well as dose. Scopolamine also impaired motor responses, resulting in increased time required to complete the bimanual motor task and increased movement time in the RT task. Performance in the PR task was decreased in a dose-dependent fashion by scopolamine. The results suggest that scopolamine interferes with memory storage and motor responses but not memory retention/retrieval or vigilance. The findings demonstrate that the test battery is useful for distinguishing the effects of neuropharmacological manipulation on various aspects of cognitive performance in monkeys.