Papers by Stephan P Swinnen
Within the field of cognitive neuroscience, it has become widely accepted to distinguish between ... more Within the field of cognitive neuroscience, it has become widely accepted to distinguish between declarative and nondeclarative memory, with different neurobiological substrates subserving these memory structures. This distinction has been inferred from the study of amnesic patients, including those suffering from Korsakoff's syndrome. It is commonly agreed that Korsakoff patients demonstrate intact memory for motor and perceptual skills (nondeclarative) whereas memory of various forms of factual knowledge (declarative) is severely impaired. In the present study, Korsakoff patients and a group of age-matched controls learned a new bimanual motor skill whereby performance was assessed in the presence and absence of augmented visual information feedback. Findings demonstrated that Korsakoff patients were able to learn and retain this skill when directive augmented information feedback was provided while no learning occurred at all in the absence of this information. These observations shed new light on the conditions required for preserved memory in amnesic patients and challenge the classic view that nondeclarative memory is invariably preserved. Instead, the quality of memory across both motor and cognitive dimensions appears to depend on the availability of task-specific information to guide performance, presumably allowing amnesic patients to bypass affected brain areas. This prompts for a reevaluation of current notions about procedural memory capacity in Korsakoff patients.
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The acquisition of a new bimanual skill depends on several motor coordination constraints. To dat... more The acquisition of a new bimanual skill depends on several motor coordination constraints. To date, coordination constraints have often been tested relatively independently of one another, particularly with respect to isofrequency and multifrequency rhythms. Here, we used a new paradigm to test the interaction of multiple coordination constraints. Coordination constraints that were tested included temporal complexity, directionality, muscle grouping, and hand dominance. Twenty-two healthy young adults performed a bimanual dial rotation task that required left and right hand coordination to track a moving target on a computer monitor. Two groups were compared, either with or without four days of practice with augmented visual feedback. Four directional patterns were tested such that both hands moved either rightward (clockwise), leftward (counterclockwise), inward or outward relative to each other. Seven frequency ratios (3:1, 2:1, 3:2, 1:1, 2:3. 1:2, 1:3) between the left and right hand were introduced. As expected, isofrequency patterns (1:1) were performed more successfully than multifrequency patterns (non 1:1). In addition, performance was more accurate when participants were required to move faster with the dominant right hand (1:3, 1:2 and 2:3) than with the non-dominant left hand (3:1, 2:1, 3:2). Interestingly, performance deteriorated as the relative angular velocity between the two hands increased, regardless of whether the required frequency ratio was an integer or non-integer. This contrasted with previous finger tapping research where the integer ratios generally led to less error than the non-integer ratios. We suggest that this is due to the different movement topologies that are required of each paradigm. Overall, we found that this visuomotor task was useful for testing the interaction of multiple coordination constraints as well as the release from these constraints with practice in the presence of augmented visual feedback.
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Neuropsychologia, 1996
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Behavioural Brain Research, 1998
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Journal of Cognitive Neuroscience, 1997
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Successfully switching between tasks is critical in many daily activities. Age-related slowing of... more Successfully switching between tasks is critical in many daily activities. Age-related slowing of this switching behavior has been documented extensively, but the underlying neural mechanisms remain unclear. The current paper investigated the contribution of brain white matter changes associated with myelin alterations to age-related slowing of switching performance. Diffusion tensor imaging derived radial diffusivity (RD) and magnetization transfer imaging derived magnetization transfer ratio (MTR) were selected as myelin sensitive measures. These metrics were related to mixing cost (i.e., the increase in reaction time during task blocks that require task switching) on a local-global switching task in young (n=24) and older (n=22) adults. Results showed that higher age was associated with widespread increases in RD and decreases in MTR, indicative of white matter deterioration possibly due to demyelination. Older adults also showed a higher mixing cost, implying slowing of switching performance. Finally, mediation analyses demonstrated that decreases in MTR of the bilateral superior corona radiata contributed to the observed slowing of switching performance with increasing age. These findings provide evidence for a role of cortico-subcortical white matter changes in task switching performance deterioration with healthy aging.
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Declines in both cortical grey matter and bimanual coordination performance are evident in health... more Declines in both cortical grey matter and bimanual coordination performance are evident in healthy aging. However, the relationship between aging, bimanual performance and grey matter loss remains unclear, particularly across the whole adult life span. Therefore, participants (N=93, range 20-80 years) performed a complex Bimanual Tracking Task and structural brain images were obtained using magnetic resonance imaging. Analyses revealed that age correlated negatively with task performance. Voxel-based-morphometry analysis revealed that age was associated with grey matter declines in task relevant cortical areas and that grey matter in these areas was negatively associated with task performance. However, no evidence for a mediating effect of grey matter in age-related bimanual performance decline was observed. We propose a new hypothesis that functional compensation may account for the observed absence of mediation, which is in line with the observed pattern of increased inter-individual variance in performance with age.
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Human Movement Science, 2003
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Spine, 2000
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Neurorehabilitation and neural repair, Jan 13, 2015
Handwriting is often impaired in Parkinson's disease (PD). Several studies have shown that wr... more Handwriting is often impaired in Parkinson's disease (PD). Several studies have shown that writing in PD benefits from the use of cues. However, this was typically studied with writing and drawing sizes that are usually not used in daily life. This study examines the effect of visual cueing on a prewriting task at small amplitudes (≤1.0 cm) in PD patients and healthy controls to better understand the working action of cueing for writing. A total of 15 PD patients and 15 healthy, age-matched controls performed a prewriting task at 0.6 cm and 1.0 cm in the presence and absence of visual cues (target lines). Writing amplitude, variability of amplitude, and speed were chosen as dependent variables, measured using a newly developed touch-sensitive tablet. Cueing led to immediate improvements in writing size, variability of writing size, and speed in both groups in the 1.0 cm condition. However, when writing at 0.6 cm with cues, a decrease in writing size was apparent in both groups (...
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PloS one, 2015
Recent studies show that besides freezing of gait (FOG), many people with Parkinson's disease... more Recent studies show that besides freezing of gait (FOG), many people with Parkinson's disease (PD) also suffer from freezing in the upper limbs (FOUL). Up to now, it is unclear which task constraints provoke and explain upper limb freezing. To investigate whether upper limb freezing and other kinematic abnormalities during writing are provoked by (i) gradual changes in amplitude or by (ii) sustained amplitude generation in patients with and without freezing of gait. Thirty-four patients with PD, including 17 with and 17 without FOG, performed a writing task on a touch-sensitive writing tablet requiring writing at constant small and large size as well as writing at gradually increasing and decreasing size. Patients of both groups were matched for disease severity, tested while 'on' medication and compared to healthy age-matched controls. Fifty upper limb freezing episodes were detected in 10 patients, including 8 with and 2 without FOG. The majority of the episodes occurr...
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Neurorehabilitation and neural repair, Jan 23, 2015
Traumatic brain injury (TBI) has been associated with altered microstructural organization of whi... more Traumatic brain injury (TBI) has been associated with altered microstructural organization of white matter (WM) and reduced gray matter (GM). Although disrupted WM organization has been linked to poorer motor performance, the predictive value of GM atrophy for motor impairments in TBI remains unclear. Here, we investigated TBI-induced GM volumetric abnormalities and uniquely examined their relationship with bimanual motor impairments. 22 moderate to severe TBI patients (mean age = 25.9 years, standard deviation [SD] = 4.9 years; time since injury = 4.7 years, SD = 3.7 years) and 27 age- and gender-matched controls (mean age = 23.4 years; SD = 3.8 years) completed bimanual tasks and a structural magnetic resonance imaging scan. Cortical and subcortical GM volumes were extracted and compared between groups using FreeSurfer. The association between bimanual performance and GM volumetric measures was investigated using partial correlations. Relative to controls, patients performed signi...
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European Journal …, Jan 1, 2010
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Brain Connectivity, 2015
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Human Brain Mapping, 2011
Language and certain aspects of motor control are typically served by the left hemisphere, wherea... more Language and certain aspects of motor control are typically served by the left hemisphere, whereas visuospatial and attentional control are lateralized to the right. Here a (visuo)motor tracing task was used to identify hemispheric lateralization beyond the general, contralateral organization of the motor system. Functional magnetic resonance imaging (fMRI) was applied in 40 male right-handers (19-30 yrs) during line tracing with dominant and nondominant hand, with and without visual guidance. Results revealed a network of areas activating more in the right than left hemisphere, irrespective of the effector. Inferior portions of frontal gyrus and parietal lobe overlapped largely with a previously described ventral attention network responding to unexpected or behaviourally relevant stimuli. This demonstrates a hitherto unreported functionality of this circuit that also seems to activate when spatial information is continuously exploited to adapt motor behaviour. Second, activation of left dorsal premotor and postcentral regions during tracing with the nondominant left hand was more pronounced than that in their right hemisphere homologues during tracing with the dominant right hand. These activation asymmetries of motor areas ipsilateral to the moving hand could not be explained by asymmetries in skill performance, the degree of handedness, or interhemispheric interactions. The latter was measured by a double-pulse transcranial magnetic stimulation paradigm, whereby a conditioning stimulus was applied over one hemisphere and a test stimulus over the other. We propose that the left premotor areas contain action representations strongly related to movement implementation which are also accessed during movements performed with the left body side.
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Frontiers in Human Neuroscience, 2015
Perceiving human motion, recognizing actions, and interpreting emotional body language are tasks ... more Perceiving human motion, recognizing actions, and interpreting emotional body language are tasks we perform daily and which are supported by a network of brain areas including the human posterior superior temporal sulcus (pSTS). Here, we applied transcranial direct current stimulation (tDCS) with anodal (excitatory) or cathodal (inhibitory) electrodes mounted over right pSTS (target) and orbito-frontal cortex (reference) while healthy participants performed a bodily emotion recognition task using biological motion point-light displays (PLDs). Performance (accuracy and reaction times) was also assessed on a control task which was matched to the emotion recognition task in terms of cognitive and motor demands. Each subject participated in two experimental sessions, receiving either anodal or cathodal stimulation, which were separated by one week to avoid residual effects of previous stimulations. Overall, tDCS brain stimulation did not affect the recognition of emotional states from PLDs. However, when emotions with a negative or positive-neutral emotional valence were analyzed separately, effects of stimulation were shown for recognizing emotions with a negative emotional valence (sadness and anger), indicating increased recognition performance when receiving anodal (excitatory) stimulation compared to cathodal (inhibitory) stimulation over pSTS. No stimulation effects were shown for the recognition of emotions with positive-neutral emotional valences. These findings extend previous studies showing structure-function relationships between STS and biological motion processing from PLDs and provide indications that stimulation effects may be modulated by the emotional valence of the stimuli.
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Brain Connectivity, 2015
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Background: Our previous study (Caeyenberghs et al., 2012) provided some evidence for the
relatio... more Background: Our previous study (Caeyenberghs et al., 2012) provided some evidence for the
relationship between abnormal structural connectivity and poor balance performance in young
traumatic axonal injury (TAI) patients. An enhanced understanding of the functional
connectivity following TAI may allow for targeted treatments geared towards improving brain
function and postural control.
Methods: 12 patients with TAI and 28 normally developing children (aged 9-19 years)
performed the Sensory Organisation Test (SOT) protocol of the EquiTest (Neurocom). All
participants were scanned using resting state fMRI (rs-fMRI) series along with anatomical
scans. We applied ‘functional connectivity density mapping’ (FCDM), a voxel-wise data-
driven method that calculates individual functional connectivity maps to obtain both short-
range and long-range FCD.
Results: Findings revealed that the TAI group scored generally lower than the control group
on the SOT, especially when proprioceptive feedback was compromised. Between-group
maps noted significantly decreased long-range FCD in the TAI group in frontal and
subcortical regions and significantly increased short-range FCD in frontal regions, left inferior
parietal and cerebellar lobules. Moreover, lower balance levels in TAI patients were
associated with a lower long-range FCD in left putamen and cerebellar vermis.
Conclusion: These findings suggest that long-range connections may be more vulnerable to
TAI than short-range connections. Moreover, higher values of short-range FCD may suggest
adaptive mechanisms in the TAI group. Finally, this study supports the view that FCDM is a
valuable tool for selectively predicting functional motor deficits in TAI patients.
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Papers by Stephan P Swinnen
relationship between abnormal structural connectivity and poor balance performance in young
traumatic axonal injury (TAI) patients. An enhanced understanding of the functional
connectivity following TAI may allow for targeted treatments geared towards improving brain
function and postural control.
Methods: 12 patients with TAI and 28 normally developing children (aged 9-19 years)
performed the Sensory Organisation Test (SOT) protocol of the EquiTest (Neurocom). All
participants were scanned using resting state fMRI (rs-fMRI) series along with anatomical
scans. We applied ‘functional connectivity density mapping’ (FCDM), a voxel-wise data-
driven method that calculates individual functional connectivity maps to obtain both short-
range and long-range FCD.
Results: Findings revealed that the TAI group scored generally lower than the control group
on the SOT, especially when proprioceptive feedback was compromised. Between-group
maps noted significantly decreased long-range FCD in the TAI group in frontal and
subcortical regions and significantly increased short-range FCD in frontal regions, left inferior
parietal and cerebellar lobules. Moreover, lower balance levels in TAI patients were
associated with a lower long-range FCD in left putamen and cerebellar vermis.
Conclusion: These findings suggest that long-range connections may be more vulnerable to
TAI than short-range connections. Moreover, higher values of short-range FCD may suggest
adaptive mechanisms in the TAI group. Finally, this study supports the view that FCDM is a
valuable tool for selectively predicting functional motor deficits in TAI patients.
relationship between abnormal structural connectivity and poor balance performance in young
traumatic axonal injury (TAI) patients. An enhanced understanding of the functional
connectivity following TAI may allow for targeted treatments geared towards improving brain
function and postural control.
Methods: 12 patients with TAI and 28 normally developing children (aged 9-19 years)
performed the Sensory Organisation Test (SOT) protocol of the EquiTest (Neurocom). All
participants were scanned using resting state fMRI (rs-fMRI) series along with anatomical
scans. We applied ‘functional connectivity density mapping’ (FCDM), a voxel-wise data-
driven method that calculates individual functional connectivity maps to obtain both short-
range and long-range FCD.
Results: Findings revealed that the TAI group scored generally lower than the control group
on the SOT, especially when proprioceptive feedback was compromised. Between-group
maps noted significantly decreased long-range FCD in the TAI group in frontal and
subcortical regions and significantly increased short-range FCD in frontal regions, left inferior
parietal and cerebellar lobules. Moreover, lower balance levels in TAI patients were
associated with a lower long-range FCD in left putamen and cerebellar vermis.
Conclusion: These findings suggest that long-range connections may be more vulnerable to
TAI than short-range connections. Moreover, higher values of short-range FCD may suggest
adaptive mechanisms in the TAI group. Finally, this study supports the view that FCDM is a
valuable tool for selectively predicting functional motor deficits in TAI patients.