The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Paul Sajda - One of the best experts on this subject based on the ideXlab platform.
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decomposing simon task bold activation using a drift diffusion model framework
Scientific Reports, 2020Co-Authors: James Mcintosh, Paul SajdaAbstract:The Simon effect is observed in spatial conflict tasks where the Response time of subjects is increased if stimuli are presented in a lateralized manner so that they are incongruous with the Response information that they represent symbolically. Previous studies have used fMRI to investigate this phenomenon, and while some have been driven by considerations of an underlying model, none have attempted to directly tie model and BOLD Response together. It is likely that this is due to Simon models having been predominantly descriptive of the phenomenon rather than capturing the full spectrum of behavior at the level of individual subjects. Sequential sampling models (SSM) which capture full Response distributions for correct and incorrect Responses have recently been extended to capture conflict tasks. In this study we use our freely available framework for fitting and comparing non-standard SSMs to fit the Simon effect SSM (SE-SSM) to behavioral data. This model extension includes specific estimates of Automatic Response bias and a conflict counteraction parameter to individual subject behavioral data. We apply this approach in order to investigate whether our task specific model parameters have a correlate in BOLD Response. Under the assumption that the SE-SSM reflects aspects of neural processing in this task, we go on to examine the BOLD correlates with the within trial expected decision-variable. We find that the SE-SSM captures the behavioral data and that our two conflict specific model parameters have clear across subject BOLD correlates, while other model parameters, as well as more standard behavioral measures do not. We also find that examining BOLD in terms of the expected decision-variable leads to a specific pattern of activation that would not be otherwise possible to extract.
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decomposing simon task bold activation using a drift diffusion model framework
bioRxiv, 2019Co-Authors: James Mcintosh, Paul SajdaAbstract:The Simon effect is observed in spatial conflict tasks where the Response time of subjects is increased if stimuli are presented in a lateralized manner so that they are incongruous with the Response information that they represent symbolically. Previous studies have used fMRI to investigate this phenomenon, and while some have been driven by considerations of an underlying model, none have attempted to directly tie model and BOLD Response together. It is likely that this is due to Simon models having been predominantly descriptive of the phenomenon rather than capturing the full spectrum of behavior at the level of individual subjects. Sequential sampling models (SSM) which capture full Response distributions for correct and incorrect Responses have recently been extended to capture conflict tasks. In this study we use our freely available framework for fitting and comparing non-standard SSM to fit the Simon effect SSM (SE-SSM) to behavioral data. This model extension includes specific estimates of Automatic Response bias and conflict monitoring based deployment of attention to individual subject behavioral data. We apply this approach in order to investigate whether our task specific model parameters have a correlate in BOLD Response. Under the assumption that the SE-SSM reflects aspects of neural processing in this task, we go on to examine the BOLD correlates with the within trial expected decision-variable. We find that the SE-SSM captures the behavioral data and that our two conflict specific model parameters have clear across subject BOLD correlates, while other model parameters, as well as more standard behavioral measures do not. We also find that examining BOLD in terms of the expected decision-variable leads to a specific pattern of activation that would not be otherwise possible to extract.
Rolf Verleger - One of the best experts on this subject based on the ideXlab platform.
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Validity and boundary conditions of Automatic Response activation in the Simon task.
Journal of Experimental Psychology: Human Perception and Performance, 2001Co-Authors: Edmund Wascher, Ulf Schatz, Thomas Kuder, Rolf VerlegerAbstract:Three experiments were conducted to determine whether spatial stimulus-Response compatibility effects are caused by Automatic Response activation by stimulus properties or by interference between codes during translation of stimulus into Response coordinates. The main evidence against activation has been that in a Simon task with hands crossed, Responses are faster at the Response location ipsilateral to the stimulus though manipulated by the hand contralateral to the stimulus. The experiments were conducted with hands in standard and in crossed positions and electroencephalogram measures showed coactivation of the motor cortex induced by stimulus position primarily during standard hand positions with visual stimuli. Only in this condition did the Simon effect decay with longer Response times. The visual Simon effect appeared to be due to specific mechanisms of visuomotor information transmission that are not responsible for the effects obtained with crossed hands or auditory stimuli.
James Mcintosh - One of the best experts on this subject based on the ideXlab platform.
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decomposing simon task bold activation using a drift diffusion model framework
Scientific Reports, 2020Co-Authors: James Mcintosh, Paul SajdaAbstract:The Simon effect is observed in spatial conflict tasks where the Response time of subjects is increased if stimuli are presented in a lateralized manner so that they are incongruous with the Response information that they represent symbolically. Previous studies have used fMRI to investigate this phenomenon, and while some have been driven by considerations of an underlying model, none have attempted to directly tie model and BOLD Response together. It is likely that this is due to Simon models having been predominantly descriptive of the phenomenon rather than capturing the full spectrum of behavior at the level of individual subjects. Sequential sampling models (SSM) which capture full Response distributions for correct and incorrect Responses have recently been extended to capture conflict tasks. In this study we use our freely available framework for fitting and comparing non-standard SSMs to fit the Simon effect SSM (SE-SSM) to behavioral data. This model extension includes specific estimates of Automatic Response bias and a conflict counteraction parameter to individual subject behavioral data. We apply this approach in order to investigate whether our task specific model parameters have a correlate in BOLD Response. Under the assumption that the SE-SSM reflects aspects of neural processing in this task, we go on to examine the BOLD correlates with the within trial expected decision-variable. We find that the SE-SSM captures the behavioral data and that our two conflict specific model parameters have clear across subject BOLD correlates, while other model parameters, as well as more standard behavioral measures do not. We also find that examining BOLD in terms of the expected decision-variable leads to a specific pattern of activation that would not be otherwise possible to extract.
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decomposing simon task bold activation using a drift diffusion model framework
bioRxiv, 2019Co-Authors: James Mcintosh, Paul SajdaAbstract:The Simon effect is observed in spatial conflict tasks where the Response time of subjects is increased if stimuli are presented in a lateralized manner so that they are incongruous with the Response information that they represent symbolically. Previous studies have used fMRI to investigate this phenomenon, and while some have been driven by considerations of an underlying model, none have attempted to directly tie model and BOLD Response together. It is likely that this is due to Simon models having been predominantly descriptive of the phenomenon rather than capturing the full spectrum of behavior at the level of individual subjects. Sequential sampling models (SSM) which capture full Response distributions for correct and incorrect Responses have recently been extended to capture conflict tasks. In this study we use our freely available framework for fitting and comparing non-standard SSM to fit the Simon effect SSM (SE-SSM) to behavioral data. This model extension includes specific estimates of Automatic Response bias and conflict monitoring based deployment of attention to individual subject behavioral data. We apply this approach in order to investigate whether our task specific model parameters have a correlate in BOLD Response. Under the assumption that the SE-SSM reflects aspects of neural processing in this task, we go on to examine the BOLD correlates with the within trial expected decision-variable. We find that the SE-SSM captures the behavioral data and that our two conflict specific model parameters have clear across subject BOLD correlates, while other model parameters, as well as more standard behavioral measures do not. We also find that examining BOLD in terms of the expected decision-variable leads to a specific pattern of activation that would not be otherwise possible to extract.
Douglas P. Munoz - One of the best experts on this subject based on the ideXlab platform.
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age related prefrontal compensatory mechanisms for inhibitory control in the antisaccade task
NeuroImage, 2018Co-Authors: Juan Fernandezruiz, Nadia Alahyane, Donald C Brien, Alicia Peltsch, Angeles Garcia, Douglas P. MunozAbstract:Abstract Cognitive decline during aging includes impairments in frontal executive functions like reduced inhibitory control. However, decline is not uniform across the population, suggesting individual brain Response variability to the aging process. Here we tested the hypothesis, within the oculomotor system, that older adults compensate for age-related neural alterations by changing neural activation levels of the oculomotor areas, or even by recruiting additional areas to assist with cognitive performance. We established that the observed changes had to be related to better cognitive performance to be considered as compensatory. To probe this hypothesis we used the antisaccade paradigm and analyzed the effect of aging on brain activations during the inhibition of prepotent Responses to visual stimuli. While undergoing a fMRI scan with concurrent eye tracking, 25 young adults (21.7 y/o ± 1.9 SDM) and 25 cognitively normal older adults (66.2 y/o ± 9.8 SDM) performed an interleaved pro/antisaccade task consisting of a preparatory stage and an execution stage. Compared to young adults, older participants showed a larger increase in antisaccade reaction times, while also generating more antisaccade direction errors. BOLD signal analyses during the preparatory stage, when Response inhibition processes are established to prevent an Automatic Response, showed decreased activations in the anterior cingulate and the supplementary eye fields in the older group. Moreover, older adults also showed additional recruitment of the frontal pole not seen in the younger group, and larger activations in the dorsolateral prefrontal cortex during antisaccade preparation. Additional analyses to address the performance variability in the older group showed distinct behavioral-BOLD signal correlations. Larger activations in the saccade network, including the frontal pole, positively correlated with faster antisaccade reaction times, suggesting a functional recruitment of this area. However, only the activation in the dorsolateral prefrontal cortex during the antisaccade events showed a negative correlation with the number of errors across older adults. These findings support the presence of two dissociable age-related plastic mechanisms that result in different behavioral outcomes. One related to the additional recruitment of neural resources within anterior pole to facilitate modulation of cognitive Responses like faster antisaccade reaction times, and another related to increased activation of the dorsolateral prefrontal cortex resulting in a better inhibitory control in aging.
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deficits in saccadic eye movement control in parkinson s disease
Neuropsychologia, 2005Co-Authors: Florence Chan, Irene T Armstrong, Giovanna Pari, Richard J Riopelle, Douglas P. MunozAbstract:In contrast to their slowed limb movements, individuals with Parkinson's disease (PD) produce rapid Automatic eye movements to sensory stimuli and show an impaired ability to generate voluntary eye movements in cognitive tasks. Eighteen PD patients and 18 matched control volunteers were instructed to look either toward (pro-saccade) or away from (anti-saccade) a peripheral stimulus as soon as it appeared (immediate, gap and overlap conditions) or after a variable delay; or, they made sequential saccades to remembered targets after a variable delay. We found that PD patients made more express saccades (correct saccades in the latency range of 90-140 ms) in the immediate pro-saccade task, more direction errors (Automatic pro-saccades) in the immediate anti-saccade task, and were less able to inhibit saccades during the delay period in all delay tasks. PD patients also made more directional and end-point errors in the memory-guided sequential task. Their inability to plan eye movements to remembered target locations suggests that PD patients have a deficit in spatial working memory which, along with their deficit in Automatic saccade suppression, is consistent with a disorder of the prefrontal-basal ganglia circuit. Impairment of this pathway may release the Automatic saccade system from top-down inhibition and produce deficits in volitional saccade control. Parallel findings across various motor, cognitive and oculomotor tasks suggest a common mechanism underlying a general deficit in Automatic Response suppression.
Edmund Wascher - One of the best experts on this subject based on the ideXlab platform.
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Validity and boundary conditions of Automatic Response activation in the Simon task.
Journal of Experimental Psychology: Human Perception and Performance, 2001Co-Authors: Edmund Wascher, Ulf Schatz, Thomas Kuder, Rolf VerlegerAbstract:Three experiments were conducted to determine whether spatial stimulus-Response compatibility effects are caused by Automatic Response activation by stimulus properties or by interference between codes during translation of stimulus into Response coordinates. The main evidence against activation has been that in a Simon task with hands crossed, Responses are faster at the Response location ipsilateral to the stimulus though manipulated by the hand contralateral to the stimulus. The experiments were conducted with hands in standard and in crossed positions and electroencephalogram measures showed coactivation of the motor cortex induced by stimulus position primarily during standard hand positions with visual stimuli. Only in this condition did the Simon effect decay with longer Response times. The visual Simon effect appeared to be due to specific mechanisms of visuomotor information transmission that are not responsible for the effects obtained with crossed hands or auditory stimuli.
