Attention, perception & psychophysics, Jan 8, 2016
With two cueing tasks, in the present study we examined output-based inhibitory cueing effects (I... more With two cueing tasks, in the present study we examined output-based inhibitory cueing effects (ICEs) with manual responses to arrow targets following manual or saccadic responses to arrow cues. In all experiments, ICEs were observed when manual localization responses were required to both the cues and targets, but only when the cue-target onset asynchrony (CTOA) was 2,000 ms or longer. In contrast, when saccadic responses were made in response to the cues, ICEs were only observed with CTOAs of 2,000 ms or less-and only when an auditory cue-back signal was used. The present study also showed that the magnitude of ICEs following saccadic responses to arrow cues decreased with time, much like traditional inhibition-of-return effects. The magnitude of ICEs following manual responses to arrow cues, however, appeared later in time and had no sign of decreasing even 3 s after cue onset. These findings suggest that ICEs linked to skeletomotor activation do exist and that the ICEs evoked by...
The neural systems that afford our ability to evaluate rewards and punishments are impacted by a ... more The neural systems that afford our ability to evaluate rewards and punishments are impacted by a variety of external factors. Here, we demonstrate that increased cognitive load reduces the functional efficacy of a reward processing system within the human medial-frontal cortex. In our paradigm, two groups of participants used performance feedback to estimate the exact duration of one second while electroencephalographic (EEG) data was recorded. Prior to performing the time estimation task, both groups were instructed to keep their eyes still and avoid blinking in line with well established EEG protocol. However, during performance of the time-estimation task, one of the two groups was provided with trial-to-trial-feedback about their performance on the time-estimation task and their eye movements to induce a higher level of cognitive load relative to participants in the other group who were solely provided with feedback about the accuracy of their temporal estimates. In line with pr...
Inhibition of return (IOR) is a cognitive phenomenon whereby reaction times (RTs) are slower to c... more Inhibition of return (IOR) is a cognitive phenomenon whereby reaction times (RTs) are slower to cued relative to uncued targets at cue-target onset asynchronies (CTOAs) greater than approximately 300 ms. One important theory of IOR proposes that there are two mutually exclusive forms of IOR, with an attentional/perceptual form arising when the oculomotor system is actively suppressed, and a motoric form arising when it is engaged (Taylor & Klein, 2000). Other theories propose that IOR is the result of multiple, additive neural mechanisms (Abrams & Dobkin, 1994). Here, we have performed computational simulations and empirical investigations in an attempt to reconcile these two competing theories. Using a dynamic neural field (DNF) model of the intermediate layers of the superior colliculus (iSC), we have modeled both a sensory adaptation mechanism of IOR, and a motoric mechanism resulting from the aftereffects of saccadic eye movements. Simulating these mechanisms, we replicated beha...
Inhibition of return (IOR) refers to an increase in reaction times to targets that appeared at a ... more Inhibition of return (IOR) refers to an increase in reaction times to targets that appeared at a previously cued location relative to an uncued location, often investigated using a spatial cueing paradigm. Despite numerous studies that have examined many aspects of IOR, the neurophysiological mechanisms underlying IOR are still in dispute. The objective of the current research is to investigate the plausible mechanisms by manipulating the cue and target types between central and peripheral stimuli in a traditional cue-target paradigm with saccadic responses to targets. In peripheral cueing conditions, we observed inhibitory cueing effects across all cue-target onset asynchronies (CTOAs) with peripheral targets, but IOR was smaller and arose later with central targets. No inhibition was observed in central cueing conditions at any CTOAs. Empirical data were simulated using a two-dimensional dynamic neural field model. Our results and simulations support previous work demonstrating that, at short CTOAs, behavioral inhibition is only observed with repeated stimulation – an effect of sensory adaptation. With longer CTOAs, IOR is observed regardless of target type, when peripheral cueing is used. Our findings suggest that behaviorally exhibited inhibitory cueing effects can be attributed to multiple mechanisms, including both attenuation of visual stimulation and local inhibition in the superior colliculus.
Studies of endogenous and exogenous attentional orienting in spatial cueing paradigms have been u... more Studies of endogenous and exogenous attentional orienting in spatial cueing paradigms have been used to investigate inhibition of return, a behavioral phenomenon characterized by delayed reaction time in response to recently attended locations. When eye movements are suppressed, attention is covertly oriented to central or peripheral stimuli. Overt orienting, on the other hand, requires explicit eye movements to the stimuli. The present study examined the time course of slowed reaction times to previously attended locations when distractors are introduced into overt and covert orienting tasks. In a series of experiments, manual responses were required to targets following central and peripheral cues at three different cue-target intervals, with and without activated oculomotor systems. The results demonstrate that, when eye movements are suppressed, behavioral inhibition is reduced or delayed in magnitude by the presence of a distractor relative to conditions without distractors. However, the time course of behavioral inhibition when eye movements are required remains similar with or without distractors.
Attention, Perception, & Psychophysics, Jan 31, 2017
There are thought to be two forms of inhibition of return (IOR) depending on whether the oculomot... more There are thought to be two forms of inhibition of return (IOR) depending on whether the oculomotor system is activated or suppressed. When saccades are allowed, output-based IOR is generated, whereas input-based IOR arises when saccades are prohibited. In a series of four experiments, we mixed or blocked compatible and incompatible trials with saccadic or manual responses to investigate whether cueing effects would follow the same pattern as those observed with more traditional peripheral onsets and central arrows. In all experiments, an uninformative cue was displayed, followed by a cue-back stimulus that was either red or green, indicating whether a compatible or incompatible response was required. The results showed that IOR was indeed observed for compatible responses in all tasks, whereas IOR was eliminated for incompatible trials – but only with saccadic responses. These findings indicate that the dissociation between input- and output-based forms of IOR depends on more than just oculomotor activation, providing further support for the existence of an inhibitory cueing effect that is distinct to the manual response modality.
Background: Event-related potentials (ERPs) may provide a non-invasive index of brain function fo... more Background: Event-related potentials (ERPs) may provide a non-invasive index of brain function for a range of clinical applications. However, as a lab-based technique, ERPs are limited by technical challenges that prevent full integration into clinical settings. New method: To translate ERP capabilities from the lab to clinical applications, we have developed methods like the Halifax Consciousness Scanner (HCS). HCS is essentially a rapid, automated ERP evaluation of brain functional status. The present study describes the ERP components evoked from auditory tones and speech stimuli. ERP results were obtained using a 5-min test in 100 healthy individuals. The HCS sequence was designed to evoke the N100, the mismatch negativity (MMN), P300, the early negative enhancement (ENE), and the N400. These components reflected sensation, perception, attention, memory, and language perception, respectively. Component detection was examined at group and individual levels, and evaluated across both statistical and classification approaches. Results: All ERP components were robustly detected at the group level. At the individual level, nonparametric statistical analyses showed reduced accuracy relative to support vector (SVM) machine classification, particularly for speech-based ERPs. Optimized SVM results were MMN: 95.6%; P300: 99.0%; ENE: 91.8%; and N400: 92.3%. Conclusions: A spectrum of individual-level ERPs can be obtained in a very short time. Machine learning classification improved detection accuracy across a large healthy control sample. Translating ERPs into clinical applications is increasingly possible at the individual level.
Proceedings of the 3rd International Conference on Cognitive and Behavioral Psychology (CBP'14), Feb 24, 2014
Steady-state visual evoked potentials (SSVEPs) are scalp recorded oscillatory brain potentials as... more Steady-state visual evoked potentials (SSVEPs) are scalp recorded oscillatory brain potentials associated with visual stimuli flickering at specific frequencies. These electrophysiological responses originate in primary visual cortex and have a sinusoidal waveform with the same temporal frequency as the stimuli. Previous work has shown that the amplitude of the SSVEP signal associated with a flickering stimulus is substantially increased when the stimulus is being attended. The dynamics of attentional mechanisms can thus be investigated by analyzing the SSVEP signals associated with flickering stimuli presented at different locations on a computer screen in attentional cueing paradigms. To extract the signal, processing of short samples of noisy signal to extract the power at the frequencies of interest is essential. In a clinical context, SSVEPs have proved useful as a diagnostic tool for disorders such as Parkinson’s, epilepsy, and schizophrenia. Furthermore, the attentional modulation of SSVEP signals can be exploited in order to control brain-computer interfaces in various clinical (e.g., to provide ‘locked-in’ patients with amyotrophic lateral sclerosis [ALS] a means of controlling aspects of their environment without muscle movements) and industrial (e.g., remote control of robotics) domains. Here, we have conducted two pilot experiments to investigate the association of SSVEP signals with mechanisms of inhibitory cueing. We propose that this novel technique could be used to examine the temporal dynamics of such inhibitory mechanisms in a manner that is not possible with traditional event-related potential (ERP) techniques and present further experimental designs that continue to investigate this issue.
Proceedings of the 6th International Symposium on Attention in Cognitive Systems (ISACS’13), Aug 2013
When the interval between a transient flash of light (a “cue”) and a second visual response signa... more When the interval between a transient flash of light (a “cue”) and a second visual response signal (a “target”) exceeds at least 200 ms, responding is slowest in the direction indicated by the first signal. This phenomenon is commonly referred to as inhibition of return (IOR). The dynamic neural field model (DNF) has proven to have broad ex- planatory power for IOR, effectively capturing many empirical results. Previous work has used a short-term depression (STD) implementation of IOR, but this approach fails to explain many behavioral phenomena observed in the literature. Here, we explore a variant model of IOR in- volving a combination of STD and delayed direct collicular inhibition. We demonstrate that this hybrid model can better reproduce established behavioural results. We use the results of this model to propose several experiments that would yield particularly valuable insight into the nature of the neurophysiological mechanisms underlying IOR.
Attention, perception & psychophysics, Jan 8, 2016
With two cueing tasks, in the present study we examined output-based inhibitory cueing effects (I... more With two cueing tasks, in the present study we examined output-based inhibitory cueing effects (ICEs) with manual responses to arrow targets following manual or saccadic responses to arrow cues. In all experiments, ICEs were observed when manual localization responses were required to both the cues and targets, but only when the cue-target onset asynchrony (CTOA) was 2,000 ms or longer. In contrast, when saccadic responses were made in response to the cues, ICEs were only observed with CTOAs of 2,000 ms or less-and only when an auditory cue-back signal was used. The present study also showed that the magnitude of ICEs following saccadic responses to arrow cues decreased with time, much like traditional inhibition-of-return effects. The magnitude of ICEs following manual responses to arrow cues, however, appeared later in time and had no sign of decreasing even 3 s after cue onset. These findings suggest that ICEs linked to skeletomotor activation do exist and that the ICEs evoked by...
The neural systems that afford our ability to evaluate rewards and punishments are impacted by a ... more The neural systems that afford our ability to evaluate rewards and punishments are impacted by a variety of external factors. Here, we demonstrate that increased cognitive load reduces the functional efficacy of a reward processing system within the human medial-frontal cortex. In our paradigm, two groups of participants used performance feedback to estimate the exact duration of one second while electroencephalographic (EEG) data was recorded. Prior to performing the time estimation task, both groups were instructed to keep their eyes still and avoid blinking in line with well established EEG protocol. However, during performance of the time-estimation task, one of the two groups was provided with trial-to-trial-feedback about their performance on the time-estimation task and their eye movements to induce a higher level of cognitive load relative to participants in the other group who were solely provided with feedback about the accuracy of their temporal estimates. In line with pr...
Inhibition of return (IOR) is a cognitive phenomenon whereby reaction times (RTs) are slower to c... more Inhibition of return (IOR) is a cognitive phenomenon whereby reaction times (RTs) are slower to cued relative to uncued targets at cue-target onset asynchronies (CTOAs) greater than approximately 300 ms. One important theory of IOR proposes that there are two mutually exclusive forms of IOR, with an attentional/perceptual form arising when the oculomotor system is actively suppressed, and a motoric form arising when it is engaged (Taylor & Klein, 2000). Other theories propose that IOR is the result of multiple, additive neural mechanisms (Abrams & Dobkin, 1994). Here, we have performed computational simulations and empirical investigations in an attempt to reconcile these two competing theories. Using a dynamic neural field (DNF) model of the intermediate layers of the superior colliculus (iSC), we have modeled both a sensory adaptation mechanism of IOR, and a motoric mechanism resulting from the aftereffects of saccadic eye movements. Simulating these mechanisms, we replicated beha...
Inhibition of return (IOR) refers to an increase in reaction times to targets that appeared at a ... more Inhibition of return (IOR) refers to an increase in reaction times to targets that appeared at a previously cued location relative to an uncued location, often investigated using a spatial cueing paradigm. Despite numerous studies that have examined many aspects of IOR, the neurophysiological mechanisms underlying IOR are still in dispute. The objective of the current research is to investigate the plausible mechanisms by manipulating the cue and target types between central and peripheral stimuli in a traditional cue-target paradigm with saccadic responses to targets. In peripheral cueing conditions, we observed inhibitory cueing effects across all cue-target onset asynchronies (CTOAs) with peripheral targets, but IOR was smaller and arose later with central targets. No inhibition was observed in central cueing conditions at any CTOAs. Empirical data were simulated using a two-dimensional dynamic neural field model. Our results and simulations support previous work demonstrating that, at short CTOAs, behavioral inhibition is only observed with repeated stimulation – an effect of sensory adaptation. With longer CTOAs, IOR is observed regardless of target type, when peripheral cueing is used. Our findings suggest that behaviorally exhibited inhibitory cueing effects can be attributed to multiple mechanisms, including both attenuation of visual stimulation and local inhibition in the superior colliculus.
Studies of endogenous and exogenous attentional orienting in spatial cueing paradigms have been u... more Studies of endogenous and exogenous attentional orienting in spatial cueing paradigms have been used to investigate inhibition of return, a behavioral phenomenon characterized by delayed reaction time in response to recently attended locations. When eye movements are suppressed, attention is covertly oriented to central or peripheral stimuli. Overt orienting, on the other hand, requires explicit eye movements to the stimuli. The present study examined the time course of slowed reaction times to previously attended locations when distractors are introduced into overt and covert orienting tasks. In a series of experiments, manual responses were required to targets following central and peripheral cues at three different cue-target intervals, with and without activated oculomotor systems. The results demonstrate that, when eye movements are suppressed, behavioral inhibition is reduced or delayed in magnitude by the presence of a distractor relative to conditions without distractors. However, the time course of behavioral inhibition when eye movements are required remains similar with or without distractors.
Attention, Perception, & Psychophysics, Jan 31, 2017
There are thought to be two forms of inhibition of return (IOR) depending on whether the oculomot... more There are thought to be two forms of inhibition of return (IOR) depending on whether the oculomotor system is activated or suppressed. When saccades are allowed, output-based IOR is generated, whereas input-based IOR arises when saccades are prohibited. In a series of four experiments, we mixed or blocked compatible and incompatible trials with saccadic or manual responses to investigate whether cueing effects would follow the same pattern as those observed with more traditional peripheral onsets and central arrows. In all experiments, an uninformative cue was displayed, followed by a cue-back stimulus that was either red or green, indicating whether a compatible or incompatible response was required. The results showed that IOR was indeed observed for compatible responses in all tasks, whereas IOR was eliminated for incompatible trials – but only with saccadic responses. These findings indicate that the dissociation between input- and output-based forms of IOR depends on more than just oculomotor activation, providing further support for the existence of an inhibitory cueing effect that is distinct to the manual response modality.
Background: Event-related potentials (ERPs) may provide a non-invasive index of brain function fo... more Background: Event-related potentials (ERPs) may provide a non-invasive index of brain function for a range of clinical applications. However, as a lab-based technique, ERPs are limited by technical challenges that prevent full integration into clinical settings. New method: To translate ERP capabilities from the lab to clinical applications, we have developed methods like the Halifax Consciousness Scanner (HCS). HCS is essentially a rapid, automated ERP evaluation of brain functional status. The present study describes the ERP components evoked from auditory tones and speech stimuli. ERP results were obtained using a 5-min test in 100 healthy individuals. The HCS sequence was designed to evoke the N100, the mismatch negativity (MMN), P300, the early negative enhancement (ENE), and the N400. These components reflected sensation, perception, attention, memory, and language perception, respectively. Component detection was examined at group and individual levels, and evaluated across both statistical and classification approaches. Results: All ERP components were robustly detected at the group level. At the individual level, nonparametric statistical analyses showed reduced accuracy relative to support vector (SVM) machine classification, particularly for speech-based ERPs. Optimized SVM results were MMN: 95.6%; P300: 99.0%; ENE: 91.8%; and N400: 92.3%. Conclusions: A spectrum of individual-level ERPs can be obtained in a very short time. Machine learning classification improved detection accuracy across a large healthy control sample. Translating ERPs into clinical applications is increasingly possible at the individual level.
Proceedings of the 3rd International Conference on Cognitive and Behavioral Psychology (CBP'14), Feb 24, 2014
Steady-state visual evoked potentials (SSVEPs) are scalp recorded oscillatory brain potentials as... more Steady-state visual evoked potentials (SSVEPs) are scalp recorded oscillatory brain potentials associated with visual stimuli flickering at specific frequencies. These electrophysiological responses originate in primary visual cortex and have a sinusoidal waveform with the same temporal frequency as the stimuli. Previous work has shown that the amplitude of the SSVEP signal associated with a flickering stimulus is substantially increased when the stimulus is being attended. The dynamics of attentional mechanisms can thus be investigated by analyzing the SSVEP signals associated with flickering stimuli presented at different locations on a computer screen in attentional cueing paradigms. To extract the signal, processing of short samples of noisy signal to extract the power at the frequencies of interest is essential. In a clinical context, SSVEPs have proved useful as a diagnostic tool for disorders such as Parkinson’s, epilepsy, and schizophrenia. Furthermore, the attentional modulation of SSVEP signals can be exploited in order to control brain-computer interfaces in various clinical (e.g., to provide ‘locked-in’ patients with amyotrophic lateral sclerosis [ALS] a means of controlling aspects of their environment without muscle movements) and industrial (e.g., remote control of robotics) domains. Here, we have conducted two pilot experiments to investigate the association of SSVEP signals with mechanisms of inhibitory cueing. We propose that this novel technique could be used to examine the temporal dynamics of such inhibitory mechanisms in a manner that is not possible with traditional event-related potential (ERP) techniques and present further experimental designs that continue to investigate this issue.
Proceedings of the 6th International Symposium on Attention in Cognitive Systems (ISACS’13), Aug 2013
When the interval between a transient flash of light (a “cue”) and a second visual response signa... more When the interval between a transient flash of light (a “cue”) and a second visual response signal (a “target”) exceeds at least 200 ms, responding is slowest in the direction indicated by the first signal. This phenomenon is commonly referred to as inhibition of return (IOR). The dynamic neural field model (DNF) has proven to have broad ex- planatory power for IOR, effectively capturing many empirical results. Previous work has used a short-term depression (STD) implementation of IOR, but this approach fails to explain many behavioral phenomena observed in the literature. Here, we explore a variant model of IOR in- volving a combination of STD and delayed direct collicular inhibition. We demonstrate that this hybrid model can better reproduce established behavioural results. We use the results of this model to propose several experiments that would yield particularly valuable insight into the nature of the neurophysiological mechanisms underlying IOR.
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range of clinical applications. However, as a lab-based technique, ERPs are limited by technical challenges
that prevent full integration into clinical settings.
New method: To translate ERP capabilities from the lab to clinical applications, we have developed methods
like the Halifax Consciousness Scanner (HCS). HCS is essentially a rapid, automated ERP evaluation
of brain functional status. The present study describes the ERP components evoked from auditory tones
and speech stimuli. ERP results were obtained using a 5-min test in 100 healthy individuals. The HCS
sequence was designed to evoke the N100, the mismatch negativity (MMN), P300, the early negative
enhancement (ENE), and the N400. These components reflected sensation, perception, attention, memory,
and language perception, respectively. Component detection was examined at group and individual
levels, and evaluated across both statistical and classification approaches.
Results: All ERP components were robustly detected at the group level. At the individual level, nonparametric
statistical analyses showed reduced accuracy relative to support vector (SVM) machine
classification, particularly for speech-based ERPs. Optimized SVM results were MMN: 95.6%; P300: 99.0%;
ENE: 91.8%; and N400: 92.3%.
Conclusions: A spectrum of individual-level ERPs can be obtained in a very short time. Machine learning
classification improved detection accuracy across a large healthy control sample. Translating ERPs into
clinical applications is increasingly possible at the individual level.
range of clinical applications. However, as a lab-based technique, ERPs are limited by technical challenges
that prevent full integration into clinical settings.
New method: To translate ERP capabilities from the lab to clinical applications, we have developed methods
like the Halifax Consciousness Scanner (HCS). HCS is essentially a rapid, automated ERP evaluation
of brain functional status. The present study describes the ERP components evoked from auditory tones
and speech stimuli. ERP results were obtained using a 5-min test in 100 healthy individuals. The HCS
sequence was designed to evoke the N100, the mismatch negativity (MMN), P300, the early negative
enhancement (ENE), and the N400. These components reflected sensation, perception, attention, memory,
and language perception, respectively. Component detection was examined at group and individual
levels, and evaluated across both statistical and classification approaches.
Results: All ERP components were robustly detected at the group level. At the individual level, nonparametric
statistical analyses showed reduced accuracy relative to support vector (SVM) machine
classification, particularly for speech-based ERPs. Optimized SVM results were MMN: 95.6%; P300: 99.0%;
ENE: 91.8%; and N400: 92.3%.
Conclusions: A spectrum of individual-level ERPs can be obtained in a very short time. Machine learning
classification improved detection accuracy across a large healthy control sample. Translating ERPs into
clinical applications is increasingly possible at the individual level.