Alice Witney | Trinity College Dublin (original) (raw)
Papers by Alice Witney
Virtual environments provide a powerful means of experimentally examining object manipulation. In... more Virtual environments provide a powerful means of experimentally examining object manipulation. In object manipulation a key issue is the coor- dination of grip force used to stabilize the object in the presence of load force variation, such as those due to inertia during object movement5. Here we de- scribe the engineering of an application in which the SensAble PHANToM is used to robotically control a hand held object and provide temporally modu- lated force fields that can be varied on a trial-by-trial basis.. Visual display is synchronized with haptic display and the recording of the robotic endeffector?s position. Analog data from two load cells mounted on the endeffector capture the forces and torques generated during interaction with the varying force fields. The system is cuurently being used to study the learning of novel load force functions during object manipulation
![Research paper thumbnail of Neuromodulation - Guiding the Advance of Research and Therapy [Working Title]](https://attachments.academia-assets.com/101699125/thumbnails/1.jpg)
](Larrivee received the Association for Research in Vision and Ophthalmology's first place award fo... more Larrivee received the Association for Research in Vision and Ophthalmology's first place award for studies on photoreceptor degenerative and developmental mechanisms. He is the editor of Brain Computer Interfacing and an editorial board member of the Annals of Neurology and Neurological Sciences (USA) and EC Neurology (UK). He is also the author of more than eight-five papers and book chapters in such varied journals/venues as Neurology and
American Journal of Psychiatry, 2001
Neuroscience Letters, 2017
Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique incr... more Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique increasingly explored for Parkinson's disease (PD). Although evidence is still inconsistent, there are preliminary findings suggesting its efficacy to improve motor function in individuals with PD, as the role of secondary motor areas remains unclear. The goal of this study was to investigate the effects of left dorsolateral prefrontal cortex (DLPFC) tDCS on balance and functional mobility of individuals with PD. Seventeen individuals with PD, on-medication, aged between 40 and 90 years were recruited to enroll in a double-blind, randomized, cross-over trial. Each participant completed two conditions at least 48 hours apart, namely anodal-tDCS and sham-tDCS (placebo).The a-tDCS condition targeted the left DLPC (F3) and was applied during 20 minutes using a 2 mA current intensity. In the sham-tDCS condition, electrode position remained the same but the stimulator was turned off after 30 seconds. Functional mobility and balance were assessed using the Berg Balance Scale, Dynamic Gait Index and Timed Up and Go. There were significant differences between conditions on all outcome measures, as the a-tDCS condition was associated with better performance in comparison to the sham condition (p<0.05). Our findings suggest that a-tDCS on the left DLPFC improves balance and functional mobility in comparison to sham-tDCS. Compensatory mechanisms that support motor function in individuals with PD may have been enhanced by a-tDCS on the DLPFC, leading to improved functional mobility and balance. Future trials should explore left DLPFC stimulation with larger samples and compare t-DCS protocols targeting several brain regions.
To understand brain function it is necessary to characterize both the underlying structural conne... more To understand brain function it is necessary to characterize both the underlying structural connectivity between neurons and the physiological integrity of these connections. Previous research exploring insect brain connectivity has used microscopy techniques, but this methodology is time consuming and cannot be applied to living animals and so cannot be used to understand dynamic physiological processes. The relatively large brain of the desert locust,Schistercera gregaria(Forksȧl) is ideal for exploring a novel methodology; diffusion magnetic resonance imaging (dMRI) for the characterization of neuronal connectivity in an insect brain. The diffusion-weighted imaging (DWI) data were acquired on a preclinical system using a customised multi-shell diffusion MRI scheme. Endogenous imaging contrasts from the averaged DWIs and Diffusion Kurtosis Imaging (DKI) scheme were applied to classify various anatomical features and diffusion patterns in neuropils, respectively. The application of...
Journal of Neurophysiology, 1999
Anticipatory responses can minimize the disturbances that result from the action of one part of t... more Anticipatory responses can minimize the disturbances that result from the action of one part of the body on another. Such a predictive response is evident in the anticipatory increase in grip force seen when one hand pulls on an object held in the other hand, thereby preventing the object from slipping. It is postulated that such a response depends on predicting the consequences of the descending motor command, as signaled by efference copy, using an internal model of both one's own body and the object. Here we investigate how the internal model learns the temporal consequences of the motor command. We employed two robots to simulate a virtual object held in one hand and acted on by the other. Delays were introduced between the action of one hand on the object and the effects of this action on the other hand. An initial reactive grip force response to the delayed load decayed with the development of appropriate anticipatory grip force modulation. However, no predictive modulatio...
Journal of Neurophysiology, 2000
Journal of Neurophysiology, 2000
Journal of Neurophysiology, 2003
A key feature of skilled motor behavior is the ability of the CNS to predict the consequences of ... more A key feature of skilled motor behavior is the ability of the CNS to predict the consequences of its actions. Such prediction occurs when one hand pulls on an object held in the other hand; the restraining hand generates an anticipatory increase in grip force, thereby preventing the object from slipping. When manipulating a novel object, the CNS adapts its predictive response to ensure that predictions are accurately tuned to the dynamics of the object. Here we examine whether learning to predict the consequences of an action on a novel object is restricted to the actions performed during manipulation or generalizes to novel actions. A bimanual task in which subjects held an object in each hand and the relationship between actions on one object and the motion of the other could be computer controlled from trial-to-trial was used. In four conditions we varied the spatial relationship between the direction of force subjects applied to the left-hand object and the consequent direction ...
Human Movement Science, 2004
gripping to reduce the consequence of an erroneous estimate of mass. Alternatively, the hand migh... more gripping to reduce the consequence of an erroneous estimate of mass. Alternatively, the hand might initially be moved more slowly than normal to allow more time for feedback-based adjustments to grip force. In this regard, a series of experiments has been designed in order to study the effects of a change in gravity on the dynamics of prehension, on the kinematics of upper limb movements and on eye-hand coordination. This report describes the results of some experiments already performed and the scientific objectives of the experiments that will be carried out in the coming years.
Biography Sophia Karok recently obtained her PhD in Neuroscience and Physiology from Trinity Coll... more Biography Sophia Karok recently obtained her PhD in Neuroscience and Physiology from Trinity College Dublin, where she studied the influence of neurostimulation techniques on human motor control. Dr Alice Witney is an Assistant Professor in Physiology at Trinity College Dublin with research interests in sensorimotor control. Abstract Background: Non-invasive neurostimulation techniques, particularly transcranial direct current stimulation
The use of electricity for analgesic effects has a long history and yet currently neuromodulation... more The use of electricity for analgesic effects has a long history and yet currently neuromodulation devices based on electrical stimulation are typically restricted to being a last resort intervention for pain patients after the failure of pharmacological treatments. Whilst spinal cord stimulation is an established intervention for intractable neuropathic pain, the use of neuromodulation for other forms of pain and targeting different aspects of pain processing is less well established. Non-invasive neuromodulation as part of a standard intervention for pain relief would be ideal for without long term treatment of a chronic pain condition as it would avoid the inevitable side effects associated with long-term use of pharmacological interventions or interactions between different drug treatments. This is particularly relevant as chronic pain can be associated with diseases that would require pharmacological treatment for the primary condition. However, there is currently both a deficit...
Transcranial Magnetic Stimulation in Neuropsychiatry, Sep 12, 2018
Non-invasive brain stimulation (NIBS) is increasingly proposed as a therapeutic intervention for ... more Non-invasive brain stimulation (NIBS) is increasingly proposed as a therapeutic intervention for many neurological and psychiatric disorders, including pain, depression, obsessive compulsive disorder, and anxiety. While neuromodulation as an intervention for pain relief has a well-established scientific basis, evidence is largely restricted to invasive stimulation that targets the spinal cord. Novel non-invasive methodologies instead predominately target cortical processing of pain and thus raise interesting questions about how the most effective pain relief can be achieved. Functional magnetic resonance imaging (fMRI) studies show a widespread and distributed activation of brain areas during pain. This diverse activity is often referred to as the "pain neuromatrix" and can lead to the proposal for different possible target areas for pain relief. Neuromodulation could target brain regions of pain processing areas responsible for sensorimotor processing or alternatively regions responsible for the affective and evaluative aspects of the subjective pain experience. The chapter addresses the different approaches currently taken in the use of non-invasive neuromodulation for altering pain both in an experimental setting and the challenges involved in the translation of these techniques to a diverse range of chronic pain conditions.
Virtual environments provide a powerful means of experimentally examining object manipulation. In... more Virtual environments provide a powerful means of experimentally examining object manipulation. In object manipulation a key issue is the coor- dination of grip force used to stabilize the object in the presence of load force variation, such as those due to inertia during object movement5. Here we de- scribe the engineering of an application in which the SensAble PHANToM is
Neuroscience letters, Jan 8, 2013
Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (... more Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) of primary motor cortex (M1) modulate cortical excitability. Both techniques have been demonstrated to modulate chronic pain and experimental pain thresholds, but with inconsistent effects. Preconditioning M1 with weak tDCS (1mA) standardizes the effects of subsequent stimulation via rTMS on levels of cortical excitability. Here we examine whether 1Hz rTMS, primed with tDCS, could effectively standardize the modulation of pain thresholds. Thermal pain thresholds were determined using quantitative sensory testing (QST) of the palmar thenar of both hands in 12 healthy males pre and post tDCS - 1Hz rTMS over the hand area of the left M1. Cathodal tDCS preconditioning of 1Hz rTMS successfully reversed the normal suppressive effect of low frequency rTMS and effectively modulated cold and heat pain thresholds. Conversely, anodal tDCS - 1Hz rTMS led to a decrease in cold pain thresholds. ...
Rheumatology (Oxford, England), 2004
Education and information are important components of the management of chronic disease, though p... more Education and information are important components of the management of chronic disease, though provision of these in the routine clinic setting may be suboptimal. We carried out a corporate needs assessment, both to evaluate stakeholders' perceived usefulness of potential facilities that could be offered by a community-based arthritis resource centre in Birmingham and to compare the views of patients with rheumatological conditions and health professionals. Rheumatology patients (n = 201 responders/309 contacted) and health professionals (n = 232/430) were asked to complete a questionnaire to assess both current rheumatology service provision and perceived needs for further information that could be offered within the proposed resource centre. Views of patients and professionals were compared using odds ratios. Logistic regression analysis determined patient characteristics associated with perceived usefulness of various information types. The overall response rate was 58%. Mos...
Virtual environments provide a powerful means of experimentally examining object manipulation. In... more Virtual environments provide a powerful means of experimentally examining object manipulation. In object manipulation a key issue is the coor- dination of grip force used to stabilize the object in the presence of load force variation, such as those due to inertia during object movement5. Here we de- scribe the engineering of an application in which the SensAble PHANToM is used to robotically control a hand held object and provide temporally modu- lated force fields that can be varied on a trial-by-trial basis.. Visual display is synchronized with haptic display and the recording of the robotic endeffector?s position. Analog data from two load cells mounted on the endeffector capture the forces and torques generated during interaction with the varying force fields. The system is cuurently being used to study the learning of novel load force functions during object manipulation
Larrivee received the Association for Research in Vision and Ophthalmology's first place award fo... more Larrivee received the Association for Research in Vision and Ophthalmology's first place award for studies on photoreceptor degenerative and developmental mechanisms. He is the editor of Brain Computer Interfacing and an editorial board member of the Annals of Neurology and Neurological Sciences (USA) and EC Neurology (UK). He is also the author of more than eight-five papers and book chapters in such varied journals/venues as Neurology and
American Journal of Psychiatry, 2001
Neuroscience Letters, 2017
Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique incr... more Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique increasingly explored for Parkinson's disease (PD). Although evidence is still inconsistent, there are preliminary findings suggesting its efficacy to improve motor function in individuals with PD, as the role of secondary motor areas remains unclear. The goal of this study was to investigate the effects of left dorsolateral prefrontal cortex (DLPFC) tDCS on balance and functional mobility of individuals with PD. Seventeen individuals with PD, on-medication, aged between 40 and 90 years were recruited to enroll in a double-blind, randomized, cross-over trial. Each participant completed two conditions at least 48 hours apart, namely anodal-tDCS and sham-tDCS (placebo).The a-tDCS condition targeted the left DLPC (F3) and was applied during 20 minutes using a 2 mA current intensity. In the sham-tDCS condition, electrode position remained the same but the stimulator was turned off after 30 seconds. Functional mobility and balance were assessed using the Berg Balance Scale, Dynamic Gait Index and Timed Up and Go. There were significant differences between conditions on all outcome measures, as the a-tDCS condition was associated with better performance in comparison to the sham condition (p<0.05). Our findings suggest that a-tDCS on the left DLPFC improves balance and functional mobility in comparison to sham-tDCS. Compensatory mechanisms that support motor function in individuals with PD may have been enhanced by a-tDCS on the DLPFC, leading to improved functional mobility and balance. Future trials should explore left DLPFC stimulation with larger samples and compare t-DCS protocols targeting several brain regions.
To understand brain function it is necessary to characterize both the underlying structural conne... more To understand brain function it is necessary to characterize both the underlying structural connectivity between neurons and the physiological integrity of these connections. Previous research exploring insect brain connectivity has used microscopy techniques, but this methodology is time consuming and cannot be applied to living animals and so cannot be used to understand dynamic physiological processes. The relatively large brain of the desert locust,Schistercera gregaria(Forksȧl) is ideal for exploring a novel methodology; diffusion magnetic resonance imaging (dMRI) for the characterization of neuronal connectivity in an insect brain. The diffusion-weighted imaging (DWI) data were acquired on a preclinical system using a customised multi-shell diffusion MRI scheme. Endogenous imaging contrasts from the averaged DWIs and Diffusion Kurtosis Imaging (DKI) scheme were applied to classify various anatomical features and diffusion patterns in neuropils, respectively. The application of...
Journal of Neurophysiology, 1999
Anticipatory responses can minimize the disturbances that result from the action of one part of t... more Anticipatory responses can minimize the disturbances that result from the action of one part of the body on another. Such a predictive response is evident in the anticipatory increase in grip force seen when one hand pulls on an object held in the other hand, thereby preventing the object from slipping. It is postulated that such a response depends on predicting the consequences of the descending motor command, as signaled by efference copy, using an internal model of both one's own body and the object. Here we investigate how the internal model learns the temporal consequences of the motor command. We employed two robots to simulate a virtual object held in one hand and acted on by the other. Delays were introduced between the action of one hand on the object and the effects of this action on the other hand. An initial reactive grip force response to the delayed load decayed with the development of appropriate anticipatory grip force modulation. However, no predictive modulatio...
Journal of Neurophysiology, 2000
Journal of Neurophysiology, 2000
Journal of Neurophysiology, 2003
A key feature of skilled motor behavior is the ability of the CNS to predict the consequences of ... more A key feature of skilled motor behavior is the ability of the CNS to predict the consequences of its actions. Such prediction occurs when one hand pulls on an object held in the other hand; the restraining hand generates an anticipatory increase in grip force, thereby preventing the object from slipping. When manipulating a novel object, the CNS adapts its predictive response to ensure that predictions are accurately tuned to the dynamics of the object. Here we examine whether learning to predict the consequences of an action on a novel object is restricted to the actions performed during manipulation or generalizes to novel actions. A bimanual task in which subjects held an object in each hand and the relationship between actions on one object and the motion of the other could be computer controlled from trial-to-trial was used. In four conditions we varied the spatial relationship between the direction of force subjects applied to the left-hand object and the consequent direction ...
Human Movement Science, 2004
gripping to reduce the consequence of an erroneous estimate of mass. Alternatively, the hand migh... more gripping to reduce the consequence of an erroneous estimate of mass. Alternatively, the hand might initially be moved more slowly than normal to allow more time for feedback-based adjustments to grip force. In this regard, a series of experiments has been designed in order to study the effects of a change in gravity on the dynamics of prehension, on the kinematics of upper limb movements and on eye-hand coordination. This report describes the results of some experiments already performed and the scientific objectives of the experiments that will be carried out in the coming years.
Biography Sophia Karok recently obtained her PhD in Neuroscience and Physiology from Trinity Coll... more Biography Sophia Karok recently obtained her PhD in Neuroscience and Physiology from Trinity College Dublin, where she studied the influence of neurostimulation techniques on human motor control. Dr Alice Witney is an Assistant Professor in Physiology at Trinity College Dublin with research interests in sensorimotor control. Abstract Background: Non-invasive neurostimulation techniques, particularly transcranial direct current stimulation
The use of electricity for analgesic effects has a long history and yet currently neuromodulation... more The use of electricity for analgesic effects has a long history and yet currently neuromodulation devices based on electrical stimulation are typically restricted to being a last resort intervention for pain patients after the failure of pharmacological treatments. Whilst spinal cord stimulation is an established intervention for intractable neuropathic pain, the use of neuromodulation for other forms of pain and targeting different aspects of pain processing is less well established. Non-invasive neuromodulation as part of a standard intervention for pain relief would be ideal for without long term treatment of a chronic pain condition as it would avoid the inevitable side effects associated with long-term use of pharmacological interventions or interactions between different drug treatments. This is particularly relevant as chronic pain can be associated with diseases that would require pharmacological treatment for the primary condition. However, there is currently both a deficit...
Transcranial Magnetic Stimulation in Neuropsychiatry, Sep 12, 2018
Non-invasive brain stimulation (NIBS) is increasingly proposed as a therapeutic intervention for ... more Non-invasive brain stimulation (NIBS) is increasingly proposed as a therapeutic intervention for many neurological and psychiatric disorders, including pain, depression, obsessive compulsive disorder, and anxiety. While neuromodulation as an intervention for pain relief has a well-established scientific basis, evidence is largely restricted to invasive stimulation that targets the spinal cord. Novel non-invasive methodologies instead predominately target cortical processing of pain and thus raise interesting questions about how the most effective pain relief can be achieved. Functional magnetic resonance imaging (fMRI) studies show a widespread and distributed activation of brain areas during pain. This diverse activity is often referred to as the "pain neuromatrix" and can lead to the proposal for different possible target areas for pain relief. Neuromodulation could target brain regions of pain processing areas responsible for sensorimotor processing or alternatively regions responsible for the affective and evaluative aspects of the subjective pain experience. The chapter addresses the different approaches currently taken in the use of non-invasive neuromodulation for altering pain both in an experimental setting and the challenges involved in the translation of these techniques to a diverse range of chronic pain conditions.
Virtual environments provide a powerful means of experimentally examining object manipulation. In... more Virtual environments provide a powerful means of experimentally examining object manipulation. In object manipulation a key issue is the coor- dination of grip force used to stabilize the object in the presence of load force variation, such as those due to inertia during object movement5. Here we de- scribe the engineering of an application in which the SensAble PHANToM is
Neuroscience letters, Jan 8, 2013
Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (... more Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) of primary motor cortex (M1) modulate cortical excitability. Both techniques have been demonstrated to modulate chronic pain and experimental pain thresholds, but with inconsistent effects. Preconditioning M1 with weak tDCS (1mA) standardizes the effects of subsequent stimulation via rTMS on levels of cortical excitability. Here we examine whether 1Hz rTMS, primed with tDCS, could effectively standardize the modulation of pain thresholds. Thermal pain thresholds were determined using quantitative sensory testing (QST) of the palmar thenar of both hands in 12 healthy males pre and post tDCS - 1Hz rTMS over the hand area of the left M1. Cathodal tDCS preconditioning of 1Hz rTMS successfully reversed the normal suppressive effect of low frequency rTMS and effectively modulated cold and heat pain thresholds. Conversely, anodal tDCS - 1Hz rTMS led to a decrease in cold pain thresholds. ...
Rheumatology (Oxford, England), 2004
Education and information are important components of the management of chronic disease, though p... more Education and information are important components of the management of chronic disease, though provision of these in the routine clinic setting may be suboptimal. We carried out a corporate needs assessment, both to evaluate stakeholders' perceived usefulness of potential facilities that could be offered by a community-based arthritis resource centre in Birmingham and to compare the views of patients with rheumatological conditions and health professionals. Rheumatology patients (n = 201 responders/309 contacted) and health professionals (n = 232/430) were asked to complete a questionnaire to assess both current rheumatology service provision and perceived needs for further information that could be offered within the proposed resource centre. Views of patients and professionals were compared using odds ratios. Logistic regression analysis determined patient characteristics associated with perceived usefulness of various information types. The overall response rate was 58%. Mos...