Data for: The influence of cognitive load on susceptibility to audio
This data and scripts can be used to replicate the statistics and graphs. ## Verb_fP3.csv ## This... more This data and scripts can be used to replicate the statistics and graphs. ## Verb_fP3.csv ## This file contains the average activation in microvolt at location FCz for each of the 13 participants for 0, 200, 400 ms ISI and baseline Both the separate data for standard and novel (column fP3) and novel - standard (column MINSTD, only calculated for the NOV conditions) time (column time) refers to the time in ms relative to the oddball probe onset. ## Verb_RT.csv ## This file contains the average reaction time noun onset to speech onset for each of the 13 participants for 0, 200, 400 ms ISI both for standard and novel. Each row contains the data of one participant. ## Verb_fP3_Analysis.R ## This is the script for R statistics (https://www.r-project.org) This script reads Verb_fP3.csv and includes sections that run an ANOVA and generate the plots from the paper
Presenting a large optic flow pattern to observers is likely to cause postural sway. However, dir... more Presenting a large optic flow pattern to observers is likely to cause postural sway. However, directional anisotropies have been reported, in that contracting optic flow induces more postural sway than expanding optic flow. Recently, we showed that the biomechanics of the lower leg cannot account for this anisotropy (Holten, Donker, Verstraten, & van der Smagt, 2013, Experimental Brain Research, 228, 117-129). The question we address in the current study is whether differences in visual processing of optic flow directions, in particular the perceptual strength of these directions, mirrors the anisotropy apparent in postural sway. That is, can contracting optic flow be considered to be a perceptually stronger visual stimulus than expanding optic flow? In the current study we use a breaking continuous flash suppression paradigm where we assume that perceptually stronger visual stimuli will break the flash suppression earlier, making the suppressed optic flow stimulus visible sooner. Surprisingly, our results show the opposite, in that expanding optic flow is detected earlier than contracting optic flow.
International journal of human-computer studies, Nov 1, 2019
We review the history of human-automation interaction research, assess its current status and ide... more We review the history of human-automation interaction research, assess its current status and identify future directions. We start by reviewing articles that were published on this topic in the International Journal of Human-Computer Studies during the last 50 years. We find that over the years, automated systems have been used more frequently (1) in time-sensitive or safety-critical settings, (2) in embodied and situated systems, and (3) by non-professional users. Looking to the future, there is a need for human-automation interaction research to focus on (1) issues of function and task allocation between humans and machines, (2) issues of trust, incorrect use, and confusion, (3) the balance between focus, divided attention and attention management, (4) the need for interdisciplinary approaches to cover breadth and depth, (5) regulation and explainability, (6) ethical and social dilemmas, (7) allowing a human and humane experience, and (8) radically different human-automation interaction.
In a recent study, De Haart et al. (Arch Phys Med Rehabil 85:886-895, 2004) investigated the reco... more In a recent study, De Haart et al. (Arch Phys Med Rehabil 85:886-895, 2004) investigated the recovery of balance in stroke patients using traditional analyses of center-of-pressure (COP) trajectories to assess the effects of health status, rehabilitation, and task conditions like standing with eyes open or closed and standing while performing a cognitive dual task. To unravel the underlying control processes, we reanalyzed these data in terms of stochastic dynamics using more advanced analyses. Dimensionality, local stability, regularity, and scaling behavior of COP trajectories were determined and compared with shuffled and phase-randomized surrogate data. The presence of long-range correlations discarded the possibility that the COP trajectories were purely random. Compared to the healthy controls, the COP trajectories of the stroke patients were characterized by increased dimensionality and instability, but greater regularity in the frontal plane. These findings were taken to imply that the stroke patients actively (i.e., cognitively) coped with the stroke-induced impairment of posture, as reflected in the increased regularity and decreased local stability, by recruiting additional control processes (i.e., more degrees of freedom) and/or by tightening the present control structure while releasing non-essential degrees of freedom from postural control. In the course of rehabilitation, dimensionality stayed fairly constant, whereas local stability increased and regularity decreased. The progressively less regular COP trajectories were interpreted to indicate a reduction of cognitive involvement in postural control as recovery from stroke progressed. Consistent with this interpretation, the dual task condition resulted in less regular COP trajectories of greater dimensionality, reflecting a task-related decrease of active, cognitive contributions to postural control. In comparison with conventional posturography, our results show a clear surplus value of dynamical measures in studying postural control.
The goal was lo identib the contribution of inbiitsic mechanical properties of the muscular-skele... more The goal was lo identib the contribution of inbiitsic mechanical properties of the muscular-skeletal system and the refex gains in controlling balance during standing. The combination of balance perturbations experiments and closed loop identification schemes made it possible to idenrib the refex loop gains and intrinsic mechanical properties in various environmental conditions. Human balance responses were studied by placing subjects on a movable support base while keeping their eyes open or closed. EMG, bodv motion and the ground reaction forces were recorded. From the platform perturbation data the Frequency Response Functions of the controller dynamics and the admittance ofthe balance control system were estimated with a non-parametric closed loop identification technique. Using a parametric model of balance control and afitting procedure the sum of the intrinsic stiffness and neural position feedback gain, the neural time delay, the neural velociv feedback gain and the intrinsic damping were uniquely identified. The results show that subjects balancing on a randomly moving platform in the for%vard-backward direction applied a minimal stifJiness strategv. The required damping to avoid oscillations was main[v due to neural velocip feedback rather than to intrinsic damping
International journal of human-computer studies, Oct 1, 2019
As vehicles of the future take on more of the driving responsibility and the role of the driver t... more As vehicles of the future take on more of the driving responsibility and the role of the driver transitions into more of a monitoring capacity, the traditional notions of interruption and attention management needs to be reconsidered for automated vehicles. We argue that the transfer of control between the automated vehicle and the human driver can be considered as an interruption handling process, and that this process goes through a series of ten explicit stages. Each stage has its own characteristics and implications for practice and future research. Therefore, in this paper we identify for each stage what is known from theory, together with important implications for safety, design, and future research, especially for human-machine interaction. More generally, the framework makes explicit that it is not appropriate to think of transfer of control as a single event or even small set of events. The framework also highlights that it might not be realistic to expect human drivers to immediately respond correctly to a system initiated request to transfer control, given that humans interleave their attention between non-driving and driving tasks, and given that a transition constitutes of multiple stages. These nuances are accounted for in the framework.
1. Cognitieve neurowetenschap: wat is het en waar komt het vandaan? Frank Wijnen & Fr... more 1. Cognitieve neurowetenschap: wat is het en waar komt het vandaan? Frank Wijnen & Frans Verstraten 2. Van neuron tot cortex: de structuur van het brein Richard van Wezel & Serge Dumoulin 3. De gereedschapskist van de cognitieve neurowetenschap Peter Hagoort & Nick ...
This workshop discusses the balance between safety and productivity as automated vehicles turn in... more This workshop discusses the balance between safety and productivity as automated vehicles turn into 'mobile offices': spaces where non-driving activities are performed during one's daily commute. Technological developments reduce the active role of the human driver that might, nonetheless, require occasional intervention. To what extent are drivers allowed to dedicate resources to non-driving work-related activities? To address this critical question, the workshop brings together a diverse community of researchers and practitioners that are interested in questions as follows: what non-driving activities are likely to be performed on one's way to work and back; what is a useful taxonomy of these tasks; how can various tasks be studied in experimental settings; and, what are the criteria to assess human performance in automated vehicles. To foster further dialogue, the outcome of the workshop will be an online blog where attendees can contribute their own thoughts: https://medium.com/the-mobile-office.
Transportation Research Part F-traffic Psychology and Behaviour, Aug 1, 2019
We investigate how quickly drivers can change lanes in response to a visual in-car warning. Our w... more We investigate how quickly drivers can change lanes in response to a visual in-car warning. Our work is motivated by technological developments, in which beacons along the road can trigger in-car warnings, for example when a driver is approaching a lane closure. What is not known, however, is at what distance such an in-car warning still allows for a timely lane change. We measured how quickly drivers respond to a visual in-car warning in a driving simulator. The driving task was combined with an audio task that provided different levels of cognitive distraction. We found that the initial reaction time to in-car warnings was significantly larger for drivers that were distracted by the audio task. Although the majority of drivers responded in time for a safe lane change, some drivers occasionally missed these signals, pointing at a serious potential hazard. Indeed, the results of a simulation model, used to investigate how this might extrapolate to regular traffic conditions, suggest that around 50% of drivers might not make a timely lane change in response to a last-minute warning. This indicates that these signals might be insufficient on their own when applied in the real world. This work can inform the design and evaluation of safer roads and in-car interfaces.
The authors investigated the effects of velocity (increasing from 0.5 to 5.0 km/hr in steps of 0.... more The authors investigated the effects of velocity (increasing from 0.5 to 5.0 km/hr in steps of 0.5 km/hr) and limb loading on the coordination between arm and leg movements during treadmill walking in 7 participants. Both the consistency of the individual limb movements and the stability of their coordination increased with increasing velocity; the frequency coordination between arm and leg movements was 2:1 at the lower velocities and 1:1 at the higher velocities. The mass manipulation affected the individual limb movements but not their coordination, indicating that a stable walking pattern was preserved. The results differed qualitatively from those obtained in studies on bimanual interlimb coordination, implying that the dynamical principles identified therein are not readily applicable to locomotion.
The influence of attention on the dynamical structure of postural sway was examined in 30 healthy... more The influence of attention on the dynamical structure of postural sway was examined in 30 healthy young adults by manipulating the focus of attention. In line with the proposed direct relation between the amount of attention invested in postural control and regularity of center-of-pressure (COP) time series, we hypothesized that: (1) increasing cognitive involvement in postural control (i.e., creating an internal focus by increasing task difficulty through visual deprivation) increases COP regularity, and (2) withdrawing attention from postural control (i.e., creating an external focus by performing a cognitive dual task) decreases COP regularity. We quantified COP dynamics in terms of sample entropy (regularity), standard deviation (variability), sway-path length of the normalized posturogram (curviness), largest Lyapunov exponent (local stability), correlation dimension (dimensionality) and scaling exponent (scaling behavior). Consistent with hypothesis 1, standing with eyes closed significantly increased COP regularity. Furthermore, variability increased and local stability decreased, implying ineffective postural control. Conversely, and in line with hypothesis 2, performing a cognitive dual task while standing with eyes closed led to greater irregularity and smaller variability, suggesting an increase in the ''efficiency, or ''automaticity'' of postural control''. In conclusion, these findings not only indicate that regularity of COP trajectories is positively related to the amount of attention invested in postural control, but also substantiate that in certain situations an increased internal focus may in fact be detrimental to postural control.
Sensory Influences on Interlimb Coordination During Gait
Springer eBooks, 2004
This chapter addresses the role of afferent feedback and reflexes in the regulation of interlimb ... more This chapter addresses the role of afferent feedback and reflexes in the regulation of interlimb coordination in animals and humans with a focus on locomotion. From the work on cats it is known that the rhythmic muscle activities during gait are generated by specialized neural circuits located in the spinal cord (the so-called central pattern generator, “CPGs”). These CPGs are coordinated by neurons, which interconnect both sides or which transmit information between the cervical and lumbar spine. It is argued that afferent input, especially load-related information, plays a major role in shaping the resulting coordination of these CPGs. Induced changes are seen not only with a general loading of the animal but also with the selective loading of a given limb. Such principles also apply to human locomotion. Studies on infants have shown that basic coordination patterns exist, very similar to those found in the cat. The effects of afferents (notably those related to load and to hip position) play an important role in phase transitions, much as was described in feline models. In adults, the role of proprioceptive afferents was studied by muscle vibration (selective stimulus for la afferents) and by adding load (activating mainly Ib afferents). When applied during gait, tendon vibration has little effect on intra - and interlimb coordination. In contrast, load manipulations produce more profound changes. During gait, the loading of one of the limbs induces adaptations in inter-limb coordination in the 3 remaining limbs, thereby providing rhythm constancy (stable cadence). This is in line with other evidence indicating that the coordination between arm and leg movements is quite robust across various types of locomotion, suggesting a strong coupling between both homologous and non-homologous limbs.
Chapter 17. Sensorimotor deficits' following stroke Results: At their PWS patients walked on aver... more Chapter 17. Sensorimotor deficits' following stroke Results: At their PWS patients walked on average for 120m, controls 374 m (P < 0.05), with no statistical difference at the matched pace. Discussion: Studies have assessed the aerobic capacity of stroke patients'; few have investigated overground walking. A 360% increase in VO2UDW is required for patients PWS over controls PWS. At the matched pace the patients require 169% VO2UDW over controls. Conclusion: The increased cost of walking in stroke survivors has significant functional implications. References [1] Wade DT, Hewer RL. Functional abilities after stroke: measurement, natural history and prognosis. Journal of Neurology, Neurosurgery and Psychiatry 1987; 50:177 182. [2] Corcoran PJ. Brengelmann GL. Oxygen uptake in normal and handicapped subjects, in relation to speed of walking beside velocity-controlled cart. Archives of Physical Medicine & Rehabilitation 1970; 51(2): 78 87.
Affect is basic to many if not all psychological phenomena. This article examines 2 of the most f... more Affect is basic to many if not all psychological phenomena. This article examines 2 of the most fundamental properties of affective experience-valence and arousal-asking how they are related to each other on a moment to moment basis. Over the past century, 6 distinct types of relations have been suggested or implicitly presupposed in the literature. We critically review the available evidence for each proposal and argue that the evidence does not provide a conclusive answer. Next, we use statistical modeling to verify the different proposals in 8 data sets (with Ns ranging from 80 to 1,417) where participants reported their affective experiences in response to experimental stimuli in laboratory settings or as momentary or remembered in natural settings. We formulate 3 key conclusions about the relation between valence and arousal: (a) on average, there is a weak but consistent V-shaped relation of arousal as a function of valence, but (b) there is large variation at the individual level, so that (c) valence and arousal can in principle show a variety of relations depending on person or circumstances. This casts doubt on the existence of a static, lawful relation between valence and arousal. The meaningfulness of the observed individual differences is supported by their personality and cultural correlates. The malleability and individual differences found in the structure of affect must be taken into account when studying affect and its role in other psychological phenomena.
In this study we evaluate how cognitive load affects susceptibility to auditory signals. Previous... more In this study we evaluate how cognitive load affects susceptibility to auditory signals. Previous research has used the frontal P3 (fP3) event related potential response to auditory novel stimuli as an index for susceptibility to auditory signals. This work demonstrated that tasks that induce cognitive load such as visual and manual tasks, reduced susceptibility. It is however unknown whether cognitive load without visual or manual components also reduces susceptibility. To investigate this, we induced cognitive load by means of the verb generation task, in which participants need to think about a verb that matches a noun. The susceptibility to auditory signals was measured by recording the event related potential in response to a successively presented oddball probe stimulus at 3 different inter-stimulus intervals, 0 ms, 200 ms or 400 ms after the offset of the noun from the verb generation task. An additional control baseline condition, in which oddball response was probed without a verb generation task, was also included. Results show that the cognitive load associated with the verb task reduces fP3 response (and associated auditory signal susceptibility) compared to baseline, independent of presentation interval. This suggests that not only visual and motor processing, but also cognitive load without visual or manual components, can reduce susceptibility to auditory signals and alerts. 1.2. Measuring auditory susceptibility As an alternative, the load of one task might also be measured
Data for: The influence of cognitive load on susceptibility to audio
This data and scripts can be used to replicate the statistics and graphs. ## Verb_fP3.csv ## This... more This data and scripts can be used to replicate the statistics and graphs. ## Verb_fP3.csv ## This file contains the average activation in microvolt at location FCz for each of the 13 participants for 0, 200, 400 ms ISI and baseline Both the separate data for standard and novel (column fP3) and novel - standard (column MINSTD, only calculated for the NOV conditions) time (column time) refers to the time in ms relative to the oddball probe onset. ## Verb_RT.csv ## This file contains the average reaction time noun onset to speech onset for each of the 13 participants for 0, 200, 400 ms ISI both for standard and novel. Each row contains the data of one participant. ## Verb_fP3_Analysis.R ## This is the script for R statistics (https://www.r-project.org) This script reads Verb_fP3.csv and includes sections that run an ANOVA and generate the plots from the paper
Presenting a large optic flow pattern to observers is likely to cause postural sway. However, dir... more Presenting a large optic flow pattern to observers is likely to cause postural sway. However, directional anisotropies have been reported, in that contracting optic flow induces more postural sway than expanding optic flow. Recently, we showed that the biomechanics of the lower leg cannot account for this anisotropy (Holten, Donker, Verstraten, & van der Smagt, 2013, Experimental Brain Research, 228, 117-129). The question we address in the current study is whether differences in visual processing of optic flow directions, in particular the perceptual strength of these directions, mirrors the anisotropy apparent in postural sway. That is, can contracting optic flow be considered to be a perceptually stronger visual stimulus than expanding optic flow? In the current study we use a breaking continuous flash suppression paradigm where we assume that perceptually stronger visual stimuli will break the flash suppression earlier, making the suppressed optic flow stimulus visible sooner. Surprisingly, our results show the opposite, in that expanding optic flow is detected earlier than contracting optic flow.
International journal of human-computer studies, Nov 1, 2019
We review the history of human-automation interaction research, assess its current status and ide... more We review the history of human-automation interaction research, assess its current status and identify future directions. We start by reviewing articles that were published on this topic in the International Journal of Human-Computer Studies during the last 50 years. We find that over the years, automated systems have been used more frequently (1) in time-sensitive or safety-critical settings, (2) in embodied and situated systems, and (3) by non-professional users. Looking to the future, there is a need for human-automation interaction research to focus on (1) issues of function and task allocation between humans and machines, (2) issues of trust, incorrect use, and confusion, (3) the balance between focus, divided attention and attention management, (4) the need for interdisciplinary approaches to cover breadth and depth, (5) regulation and explainability, (6) ethical and social dilemmas, (7) allowing a human and humane experience, and (8) radically different human-automation interaction.
In a recent study, De Haart et al. (Arch Phys Med Rehabil 85:886-895, 2004) investigated the reco... more In a recent study, De Haart et al. (Arch Phys Med Rehabil 85:886-895, 2004) investigated the recovery of balance in stroke patients using traditional analyses of center-of-pressure (COP) trajectories to assess the effects of health status, rehabilitation, and task conditions like standing with eyes open or closed and standing while performing a cognitive dual task. To unravel the underlying control processes, we reanalyzed these data in terms of stochastic dynamics using more advanced analyses. Dimensionality, local stability, regularity, and scaling behavior of COP trajectories were determined and compared with shuffled and phase-randomized surrogate data. The presence of long-range correlations discarded the possibility that the COP trajectories were purely random. Compared to the healthy controls, the COP trajectories of the stroke patients were characterized by increased dimensionality and instability, but greater regularity in the frontal plane. These findings were taken to imply that the stroke patients actively (i.e., cognitively) coped with the stroke-induced impairment of posture, as reflected in the increased regularity and decreased local stability, by recruiting additional control processes (i.e., more degrees of freedom) and/or by tightening the present control structure while releasing non-essential degrees of freedom from postural control. In the course of rehabilitation, dimensionality stayed fairly constant, whereas local stability increased and regularity decreased. The progressively less regular COP trajectories were interpreted to indicate a reduction of cognitive involvement in postural control as recovery from stroke progressed. Consistent with this interpretation, the dual task condition resulted in less regular COP trajectories of greater dimensionality, reflecting a task-related decrease of active, cognitive contributions to postural control. In comparison with conventional posturography, our results show a clear surplus value of dynamical measures in studying postural control.
The goal was lo identib the contribution of inbiitsic mechanical properties of the muscular-skele... more The goal was lo identib the contribution of inbiitsic mechanical properties of the muscular-skeletal system and the refex gains in controlling balance during standing. The combination of balance perturbations experiments and closed loop identification schemes made it possible to idenrib the refex loop gains and intrinsic mechanical properties in various environmental conditions. Human balance responses were studied by placing subjects on a movable support base while keeping their eyes open or closed. EMG, bodv motion and the ground reaction forces were recorded. From the platform perturbation data the Frequency Response Functions of the controller dynamics and the admittance ofthe balance control system were estimated with a non-parametric closed loop identification technique. Using a parametric model of balance control and afitting procedure the sum of the intrinsic stiffness and neural position feedback gain, the neural time delay, the neural velociv feedback gain and the intrinsic damping were uniquely identified. The results show that subjects balancing on a randomly moving platform in the for%vard-backward direction applied a minimal stifJiness strategv. The required damping to avoid oscillations was main[v due to neural velocip feedback rather than to intrinsic damping
International journal of human-computer studies, Oct 1, 2019
As vehicles of the future take on more of the driving responsibility and the role of the driver t... more As vehicles of the future take on more of the driving responsibility and the role of the driver transitions into more of a monitoring capacity, the traditional notions of interruption and attention management needs to be reconsidered for automated vehicles. We argue that the transfer of control between the automated vehicle and the human driver can be considered as an interruption handling process, and that this process goes through a series of ten explicit stages. Each stage has its own characteristics and implications for practice and future research. Therefore, in this paper we identify for each stage what is known from theory, together with important implications for safety, design, and future research, especially for human-machine interaction. More generally, the framework makes explicit that it is not appropriate to think of transfer of control as a single event or even small set of events. The framework also highlights that it might not be realistic to expect human drivers to immediately respond correctly to a system initiated request to transfer control, given that humans interleave their attention between non-driving and driving tasks, and given that a transition constitutes of multiple stages. These nuances are accounted for in the framework.
1. Cognitieve neurowetenschap: wat is het en waar komt het vandaan? Frank Wijnen &amp;amp; Fr... more 1. Cognitieve neurowetenschap: wat is het en waar komt het vandaan? Frank Wijnen &amp;amp; Frans Verstraten 2. Van neuron tot cortex: de structuur van het brein Richard van Wezel &amp;amp; Serge Dumoulin 3. De gereedschapskist van de cognitieve neurowetenschap Peter Hagoort &amp;amp; Nick ...
This workshop discusses the balance between safety and productivity as automated vehicles turn in... more This workshop discusses the balance between safety and productivity as automated vehicles turn into 'mobile offices': spaces where non-driving activities are performed during one's daily commute. Technological developments reduce the active role of the human driver that might, nonetheless, require occasional intervention. To what extent are drivers allowed to dedicate resources to non-driving work-related activities? To address this critical question, the workshop brings together a diverse community of researchers and practitioners that are interested in questions as follows: what non-driving activities are likely to be performed on one's way to work and back; what is a useful taxonomy of these tasks; how can various tasks be studied in experimental settings; and, what are the criteria to assess human performance in automated vehicles. To foster further dialogue, the outcome of the workshop will be an online blog where attendees can contribute their own thoughts: https://medium.com/the-mobile-office.
Transportation Research Part F-traffic Psychology and Behaviour, Aug 1, 2019
We investigate how quickly drivers can change lanes in response to a visual in-car warning. Our w... more We investigate how quickly drivers can change lanes in response to a visual in-car warning. Our work is motivated by technological developments, in which beacons along the road can trigger in-car warnings, for example when a driver is approaching a lane closure. What is not known, however, is at what distance such an in-car warning still allows for a timely lane change. We measured how quickly drivers respond to a visual in-car warning in a driving simulator. The driving task was combined with an audio task that provided different levels of cognitive distraction. We found that the initial reaction time to in-car warnings was significantly larger for drivers that were distracted by the audio task. Although the majority of drivers responded in time for a safe lane change, some drivers occasionally missed these signals, pointing at a serious potential hazard. Indeed, the results of a simulation model, used to investigate how this might extrapolate to regular traffic conditions, suggest that around 50% of drivers might not make a timely lane change in response to a last-minute warning. This indicates that these signals might be insufficient on their own when applied in the real world. This work can inform the design and evaluation of safer roads and in-car interfaces.
The authors investigated the effects of velocity (increasing from 0.5 to 5.0 km/hr in steps of 0.... more The authors investigated the effects of velocity (increasing from 0.5 to 5.0 km/hr in steps of 0.5 km/hr) and limb loading on the coordination between arm and leg movements during treadmill walking in 7 participants. Both the consistency of the individual limb movements and the stability of their coordination increased with increasing velocity; the frequency coordination between arm and leg movements was 2:1 at the lower velocities and 1:1 at the higher velocities. The mass manipulation affected the individual limb movements but not their coordination, indicating that a stable walking pattern was preserved. The results differed qualitatively from those obtained in studies on bimanual interlimb coordination, implying that the dynamical principles identified therein are not readily applicable to locomotion.
The influence of attention on the dynamical structure of postural sway was examined in 30 healthy... more The influence of attention on the dynamical structure of postural sway was examined in 30 healthy young adults by manipulating the focus of attention. In line with the proposed direct relation between the amount of attention invested in postural control and regularity of center-of-pressure (COP) time series, we hypothesized that: (1) increasing cognitive involvement in postural control (i.e., creating an internal focus by increasing task difficulty through visual deprivation) increases COP regularity, and (2) withdrawing attention from postural control (i.e., creating an external focus by performing a cognitive dual task) decreases COP regularity. We quantified COP dynamics in terms of sample entropy (regularity), standard deviation (variability), sway-path length of the normalized posturogram (curviness), largest Lyapunov exponent (local stability), correlation dimension (dimensionality) and scaling exponent (scaling behavior). Consistent with hypothesis 1, standing with eyes closed significantly increased COP regularity. Furthermore, variability increased and local stability decreased, implying ineffective postural control. Conversely, and in line with hypothesis 2, performing a cognitive dual task while standing with eyes closed led to greater irregularity and smaller variability, suggesting an increase in the ''efficiency, or ''automaticity'' of postural control''. In conclusion, these findings not only indicate that regularity of COP trajectories is positively related to the amount of attention invested in postural control, but also substantiate that in certain situations an increased internal focus may in fact be detrimental to postural control.
Sensory Influences on Interlimb Coordination During Gait
Springer eBooks, 2004
This chapter addresses the role of afferent feedback and reflexes in the regulation of interlimb ... more This chapter addresses the role of afferent feedback and reflexes in the regulation of interlimb coordination in animals and humans with a focus on locomotion. From the work on cats it is known that the rhythmic muscle activities during gait are generated by specialized neural circuits located in the spinal cord (the so-called central pattern generator, “CPGs”). These CPGs are coordinated by neurons, which interconnect both sides or which transmit information between the cervical and lumbar spine. It is argued that afferent input, especially load-related information, plays a major role in shaping the resulting coordination of these CPGs. Induced changes are seen not only with a general loading of the animal but also with the selective loading of a given limb. Such principles also apply to human locomotion. Studies on infants have shown that basic coordination patterns exist, very similar to those found in the cat. The effects of afferents (notably those related to load and to hip position) play an important role in phase transitions, much as was described in feline models. In adults, the role of proprioceptive afferents was studied by muscle vibration (selective stimulus for la afferents) and by adding load (activating mainly Ib afferents). When applied during gait, tendon vibration has little effect on intra - and interlimb coordination. In contrast, load manipulations produce more profound changes. During gait, the loading of one of the limbs induces adaptations in inter-limb coordination in the 3 remaining limbs, thereby providing rhythm constancy (stable cadence). This is in line with other evidence indicating that the coordination between arm and leg movements is quite robust across various types of locomotion, suggesting a strong coupling between both homologous and non-homologous limbs.
Chapter 17. Sensorimotor deficits' following stroke Results: At their PWS patients walked on aver... more Chapter 17. Sensorimotor deficits' following stroke Results: At their PWS patients walked on average for 120m, controls 374 m (P < 0.05), with no statistical difference at the matched pace. Discussion: Studies have assessed the aerobic capacity of stroke patients'; few have investigated overground walking. A 360% increase in VO2UDW is required for patients PWS over controls PWS. At the matched pace the patients require 169% VO2UDW over controls. Conclusion: The increased cost of walking in stroke survivors has significant functional implications. References [1] Wade DT, Hewer RL. Functional abilities after stroke: measurement, natural history and prognosis. Journal of Neurology, Neurosurgery and Psychiatry 1987; 50:177 182. [2] Corcoran PJ. Brengelmann GL. Oxygen uptake in normal and handicapped subjects, in relation to speed of walking beside velocity-controlled cart. Archives of Physical Medicine & Rehabilitation 1970; 51(2): 78 87.
Affect is basic to many if not all psychological phenomena. This article examines 2 of the most f... more Affect is basic to many if not all psychological phenomena. This article examines 2 of the most fundamental properties of affective experience-valence and arousal-asking how they are related to each other on a moment to moment basis. Over the past century, 6 distinct types of relations have been suggested or implicitly presupposed in the literature. We critically review the available evidence for each proposal and argue that the evidence does not provide a conclusive answer. Next, we use statistical modeling to verify the different proposals in 8 data sets (with Ns ranging from 80 to 1,417) where participants reported their affective experiences in response to experimental stimuli in laboratory settings or as momentary or remembered in natural settings. We formulate 3 key conclusions about the relation between valence and arousal: (a) on average, there is a weak but consistent V-shaped relation of arousal as a function of valence, but (b) there is large variation at the individual level, so that (c) valence and arousal can in principle show a variety of relations depending on person or circumstances. This casts doubt on the existence of a static, lawful relation between valence and arousal. The meaningfulness of the observed individual differences is supported by their personality and cultural correlates. The malleability and individual differences found in the structure of affect must be taken into account when studying affect and its role in other psychological phenomena.
In this study we evaluate how cognitive load affects susceptibility to auditory signals. Previous... more In this study we evaluate how cognitive load affects susceptibility to auditory signals. Previous research has used the frontal P3 (fP3) event related potential response to auditory novel stimuli as an index for susceptibility to auditory signals. This work demonstrated that tasks that induce cognitive load such as visual and manual tasks, reduced susceptibility. It is however unknown whether cognitive load without visual or manual components also reduces susceptibility. To investigate this, we induced cognitive load by means of the verb generation task, in which participants need to think about a verb that matches a noun. The susceptibility to auditory signals was measured by recording the event related potential in response to a successively presented oddball probe stimulus at 3 different inter-stimulus intervals, 0 ms, 200 ms or 400 ms after the offset of the noun from the verb generation task. An additional control baseline condition, in which oddball response was probed without a verb generation task, was also included. Results show that the cognitive load associated with the verb task reduces fP3 response (and associated auditory signal susceptibility) compared to baseline, independent of presentation interval. This suggests that not only visual and motor processing, but also cognitive load without visual or manual components, can reduce susceptibility to auditory signals and alerts. 1.2. Measuring auditory susceptibility As an alternative, the load of one task might also be measured
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Papers by Stella Donker