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.
Event-related potentials (ERPs) are tiny electrical brain responses in the human electroencephalo... more Event-related potentials (ERPs) are tiny electrical brain responses in the human electroencephalogram that are typically not detectable until they are isolated by a process of signal averaging. Owing to the extremely small size of ERP components (ranging from less than 1 lV to tens of lV), compared to background brain rhythms, statistical analyses of ERPs are predominantly carried out in groups of subjects. This limitation is a barrier to the translation of ERP-based neuroscience to applications such as medical diagnostics. We show here that support vector machines (SVMs) are a useful method to detect ERP components in individual subjects with a small set of electrodes and a small number of trials for a mismatch negativity (MMN) ERP component. Such a reduced experiment setup is important for clinical applications. One hundred healthy individuals were presented with an auditory pattern containing pattern-violating deviants to evoke the MMN. Two-class SVMs were then trained to classify averaged ERP waveforms in response to the standard tone (tones that match the pattern) and deviant tone stimuli (tones that violate the pattern). The influence of kernel type, number of epochs, electrode selection, and temporal window size in the averaged waveform were explored. When using all electrodes, averages of all available epochs, and a temporal window from 0 to 900-ms post-stimulus, a linear SVM achieved 94.5 % accuracy. Further analyses using SVMs trained with narrower, sliding temporal windows confirmed the sensitivity of the SVM to data in the latency range associated with the MMN.
Sensory adaptation and oculomotor inhibition of return (IOR) have been extensively modeled using ... more Sensory adaptation and oculomotor inhibition of return (IOR) have been extensively modeled using a onedimensional dynamic neural field (DNF) model of the superior colliculus (SC). However, a great deal of paradigms are incapable of being simulated in a single dimension, limiting the generality of previous implementations. Here, we expand on previous work by implementing the inhibitory cueing mechanisms underlying IOR in a two-dimensional DNF. With such a model, we were able to reproduce the results reported in our previous work, validating the use of two-dimensional DNF models in future theoretical investigations. We discuss a number of new findings in the literature that should be simulated in two dimensions to further our understanding of inhibitory cueing mechanisms and saccade dynamics, such as the center of gravity effect of IOR.
Inhibition of return (IOR) operationalizes a behavioral phenomenon characterized by slower respon... more Inhibition of return (IOR) operationalizes a behavioral phenomenon characterized by slower responding to cued, relative to uncued, targets. Two independent forms of IOR have been theorized: input-based IOR occurs when the oculomotor system is quiescent, while output-based IOR occurs when the oculomotor system is engaged. EEG studies forbidding eye movements have demonstrated that reductions of target-elicited P1 components are correlated with IOR magnitude, but when eye movements occur, P1 effects bear no relationship to behavior. We expand on this work by adapting the cueing paradigm and recording event-related potentials: IOR is caused by oculomotor responses to central arrows or peripheral onsets and measured by key presses to peripheral targets. Behavioral IOR is observed in both conditions, but P1 reductions are absent in the central arrow condition. By contrast, arrow and peripheral cues enhance Nd, especially over contralateral electrode sites.
We explored the nature and time course of effects generated by spatially uninformative peripheral... more We explored the nature and time course of effects generated by spatially uninformative peripheral cues by measuring these effects with localization responses to peripheral onsets or central arrow targets. In Experiment 1, participants made saccadic eye movements to equiprobable peripheral and central targets. At short cue-target onset asynchronies (CTOAs), responses to cued peripheral stimuli suffered from slowed responding attributable to sensory adaptation while responses to central targets were transiently facilitated, presumably due to cue-elicited oculomotor activation. At the longest CTOA, saccadic responses to central and peripheral targets were indistinguishably delayed, suggesting a common, output/decision effect (inhibition of return; IOR). In Experiment 2, we tested the hypothesis that the generation of this output effect is dependent on the activation state of the oculomotor system by forbidding eye movements and requiring keypress responses to frequent peripheral targets, while probing oculomotor behavior with saccades to infrequent central arrow targets. As predicted, saccades to central arrow targets showed neither the early facilitation nor later inhibitory effects that were robust in Experiment 1. At the long CTOA, manual responses to cued peripheral targets showed the typical delayed responses usually attributed to IOR. We recommend that this late "inhibitory" cueing effect (ICE) be distinguished from IOR because it lacks the cause (oculomotor activation) and effect (response bias) attributed to IOR when it was named by Posner, .
Previous research has demonstrated that people are faster at making a manual response with the ha... more Previous research has demonstrated that people are faster at making a manual response with the hand that is aligned with the handle of a manipulable object compared to its functional end. According to theories of embodied cognition (ETC), the presentation of a manipulable object automatically elicits sensorimotor simulations of the respective hand and these simulations facilitate the response. However, an alternative interpretation of these data is that handles preferentially attract visual attention, since attended stimuli and locations typically elicit faster responses. We investigated attentional biases elicited by manipulable and non-manipulable objects using event-related-potentials (ERPs). On each trial, a picture of a manipulable object was followed by a target dot that participants had to make a button-press to. The dot was located at either the handle or functional end of the object. Consistent with previous attentional cuing paradigms, we showed that the P1 ERP component was greater in response to targets cued by handles than by functional ends. These results suggest that object handles automatically bias covert attentional processes. These attentional biases may account for earlier behavioural findings, without any recourse to ETC. Crown
Inhibition of return (IOR) most often describes the finding of increased response times to cued a... more Inhibition of return (IOR) most often describes the finding of increased response times to cued as compared to uncued targets in the standard covert orienting paradigm. A perennial question in the IOR literature centers on whether the effect of IOR is on motoric/decision-making processes (outputbased IOR), attentional/perceptual processes (input-based IOR), or both. Recent data converge on the idea that IOR is an output-based effect when eye movements are required or permitted whereas IOR is an input-based effect when eye movements are monitored and actively discouraged. The notion that the effects of IOR may be fundamentally different depending on the activation state of the oculomotor system has been challenged by several studies demonstrating that IOR exists as an output-, or output-plus inputbased effect in simple keypress tasks not requiring oculomotor responses. Problematically, experiments in which keypress responses are required to visual events rarely use eye movement monitoring let alone the active discouragement of eye movement errors. Here, we return to an experimental method implemented by Ivanoff and Klein whose results demonstrated that IOR affected output-based processes when, ostensibly, only keypress responses occurred. Unlike Ivanoff and Klein, however, we assiduously monitor and discourage eye movements. We demonstrate that actively discouraging eye movements in keypress tasks changes the form of IOR from output-to input-based and, as such, we strongly encourage superior experimental control over or consideration of the contribution of eye movement activity in simple keypress tasks exploring IOR.
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.
When the interval between a spatially uninformative arrow and a visual target is short (<500 ms),... more When the interval between a spatially uninformative arrow and a visual target is short (<500 ms), response times (RTs) are fastest when the arrow points to the target. When this interval exceeds 500 ms, there is a near-universal absence of an effect of the arrow on RTs. Contrary to this expected pattern of results, Taylor and Klein (J Exp Psychol Hum Percept Perform 26:1639-1656 observed that RTs were slowest when a tobe-localized visual target occurred in the direction of a fixated arrow presented 1 s earlier (i.e., an "inhibitory" Cueing effect; ICE). Here we examined which factor(s) may have allowed the arrow to generate an ICE. Our experiments indicated that the ICE was a side effect of subthreshold response activation attributable to a task-induced association between the arrow and a keypress response. Because the cause of this ICE was more closely related to subthreshold keypress activation than to oculomotor activation, we considered that the effect might be more similar to the negative compatibility effect (NCE) than to inhibition of return (IOR). This similarity raises the possibility that classical IOR, when caused by a spatially uninformative peripheral onset event and measured by a keypress response to a subsequent onset, might represent, in part, another instance of an NCE. Serendipitously, we discovered that context (i.e., whether an uninformative peripheral onset could occur at the time of an uninformative central arrow) ultimately determined whether the "inhibitory" aftermath of automatic response activation would affect output or input pathways.
Taylor and Klein (Journal of Experimental Psychology: Human Perception and Performance 26: [1639]... more Taylor and Klein (Journal of Experimental Psychology: Human Perception and Performance 26: [1639][1640][1641][1642][1643][1644][1645][1646][1647][1648][1649][1650][1651][1652][1653][1654][1655][1656] 2000) discovered two mutually exclusive "flavors" of inhibition of return (IOR): When the oculomotor system is "actively suppressed," IOR affects input processes (the perception/attention flavor), whereas when the oculomotor system is "engaged," IOR affects output processes (the motor flavor). Studies of brain activity with ignored cues have typically reported that IOR reduces an early sensory event-related potential (ERP) component (i.e., the P1 component) of the brain's response to the target. Since eye movements were discouraged in these experiments, the P1 reduction might be a reflection of the perception/attention flavor of IOR. If, instead of ignoring the cue, participants made a prosaccade to the cue (and then returned to fixation) before responding to the target, the motor flavor of IOR should then be generated. We compared these two conditions while monitoring eye position and recording ERPs to the targets. If the P1 modulation is related to the perceptual/ attentional flavor of IOR, we hypothesized that it might be absent when the motoric flavor of IOR was generated by a prosaccade to the cue. Our results demonstrated that targetrelated P1 reductions and behavioral IOR were similar, and significant, in both conditions. However, P1 modulations were significantly correlated with behavioral IOR only when the oculomotor system was actively suppressed, suggesting that P1 modulations may only affect behaviorally exhibited IOR when the attentional/perceptual flavor of IOR is recruited.
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.
Event-related potentials (ERPs) are tiny electrical brain responses in the human electroencephalo... more Event-related potentials (ERPs) are tiny electrical brain responses in the human electroencephalogram that are typically not detectable until they are isolated by a process of signal averaging. Owing to the extremely small size of ERP components (ranging from less than 1 lV to tens of lV), compared to background brain rhythms, statistical analyses of ERPs are predominantly carried out in groups of subjects. This limitation is a barrier to the translation of ERP-based neuroscience to applications such as medical diagnostics. We show here that support vector machines (SVMs) are a useful method to detect ERP components in individual subjects with a small set of electrodes and a small number of trials for a mismatch negativity (MMN) ERP component. Such a reduced experiment setup is important for clinical applications. One hundred healthy individuals were presented with an auditory pattern containing pattern-violating deviants to evoke the MMN. Two-class SVMs were then trained to classify averaged ERP waveforms in response to the standard tone (tones that match the pattern) and deviant tone stimuli (tones that violate the pattern). The influence of kernel type, number of epochs, electrode selection, and temporal window size in the averaged waveform were explored. When using all electrodes, averages of all available epochs, and a temporal window from 0 to 900-ms post-stimulus, a linear SVM achieved 94.5 % accuracy. Further analyses using SVMs trained with narrower, sliding temporal windows confirmed the sensitivity of the SVM to data in the latency range associated with the MMN.
Sensory adaptation and oculomotor inhibition of return (IOR) have been extensively modeled using ... more Sensory adaptation and oculomotor inhibition of return (IOR) have been extensively modeled using a onedimensional dynamic neural field (DNF) model of the superior colliculus (SC). However, a great deal of paradigms are incapable of being simulated in a single dimension, limiting the generality of previous implementations. Here, we expand on previous work by implementing the inhibitory cueing mechanisms underlying IOR in a two-dimensional DNF. With such a model, we were able to reproduce the results reported in our previous work, validating the use of two-dimensional DNF models in future theoretical investigations. We discuss a number of new findings in the literature that should be simulated in two dimensions to further our understanding of inhibitory cueing mechanisms and saccade dynamics, such as the center of gravity effect of IOR.
Inhibition of return (IOR) operationalizes a behavioral phenomenon characterized by slower respon... more Inhibition of return (IOR) operationalizes a behavioral phenomenon characterized by slower responding to cued, relative to uncued, targets. Two independent forms of IOR have been theorized: input-based IOR occurs when the oculomotor system is quiescent, while output-based IOR occurs when the oculomotor system is engaged. EEG studies forbidding eye movements have demonstrated that reductions of target-elicited P1 components are correlated with IOR magnitude, but when eye movements occur, P1 effects bear no relationship to behavior. We expand on this work by adapting the cueing paradigm and recording event-related potentials: IOR is caused by oculomotor responses to central arrows or peripheral onsets and measured by key presses to peripheral targets. Behavioral IOR is observed in both conditions, but P1 reductions are absent in the central arrow condition. By contrast, arrow and peripheral cues enhance Nd, especially over contralateral electrode sites.
We explored the nature and time course of effects generated by spatially uninformative peripheral... more We explored the nature and time course of effects generated by spatially uninformative peripheral cues by measuring these effects with localization responses to peripheral onsets or central arrow targets. In Experiment 1, participants made saccadic eye movements to equiprobable peripheral and central targets. At short cue-target onset asynchronies (CTOAs), responses to cued peripheral stimuli suffered from slowed responding attributable to sensory adaptation while responses to central targets were transiently facilitated, presumably due to cue-elicited oculomotor activation. At the longest CTOA, saccadic responses to central and peripheral targets were indistinguishably delayed, suggesting a common, output/decision effect (inhibition of return; IOR). In Experiment 2, we tested the hypothesis that the generation of this output effect is dependent on the activation state of the oculomotor system by forbidding eye movements and requiring keypress responses to frequent peripheral targets, while probing oculomotor behavior with saccades to infrequent central arrow targets. As predicted, saccades to central arrow targets showed neither the early facilitation nor later inhibitory effects that were robust in Experiment 1. At the long CTOA, manual responses to cued peripheral targets showed the typical delayed responses usually attributed to IOR. We recommend that this late "inhibitory" cueing effect (ICE) be distinguished from IOR because it lacks the cause (oculomotor activation) and effect (response bias) attributed to IOR when it was named by Posner, .
Previous research has demonstrated that people are faster at making a manual response with the ha... more Previous research has demonstrated that people are faster at making a manual response with the hand that is aligned with the handle of a manipulable object compared to its functional end. According to theories of embodied cognition (ETC), the presentation of a manipulable object automatically elicits sensorimotor simulations of the respective hand and these simulations facilitate the response. However, an alternative interpretation of these data is that handles preferentially attract visual attention, since attended stimuli and locations typically elicit faster responses. We investigated attentional biases elicited by manipulable and non-manipulable objects using event-related-potentials (ERPs). On each trial, a picture of a manipulable object was followed by a target dot that participants had to make a button-press to. The dot was located at either the handle or functional end of the object. Consistent with previous attentional cuing paradigms, we showed that the P1 ERP component was greater in response to targets cued by handles than by functional ends. These results suggest that object handles automatically bias covert attentional processes. These attentional biases may account for earlier behavioural findings, without any recourse to ETC. Crown
Inhibition of return (IOR) most often describes the finding of increased response times to cued a... more Inhibition of return (IOR) most often describes the finding of increased response times to cued as compared to uncued targets in the standard covert orienting paradigm. A perennial question in the IOR literature centers on whether the effect of IOR is on motoric/decision-making processes (outputbased IOR), attentional/perceptual processes (input-based IOR), or both. Recent data converge on the idea that IOR is an output-based effect when eye movements are required or permitted whereas IOR is an input-based effect when eye movements are monitored and actively discouraged. The notion that the effects of IOR may be fundamentally different depending on the activation state of the oculomotor system has been challenged by several studies demonstrating that IOR exists as an output-, or output-plus inputbased effect in simple keypress tasks not requiring oculomotor responses. Problematically, experiments in which keypress responses are required to visual events rarely use eye movement monitoring let alone the active discouragement of eye movement errors. Here, we return to an experimental method implemented by Ivanoff and Klein whose results demonstrated that IOR affected output-based processes when, ostensibly, only keypress responses occurred. Unlike Ivanoff and Klein, however, we assiduously monitor and discourage eye movements. We demonstrate that actively discouraging eye movements in keypress tasks changes the form of IOR from output-to input-based and, as such, we strongly encourage superior experimental control over or consideration of the contribution of eye movement activity in simple keypress tasks exploring IOR.
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.
When the interval between a spatially uninformative arrow and a visual target is short (<500 ms),... more When the interval between a spatially uninformative arrow and a visual target is short (<500 ms), response times (RTs) are fastest when the arrow points to the target. When this interval exceeds 500 ms, there is a near-universal absence of an effect of the arrow on RTs. Contrary to this expected pattern of results, Taylor and Klein (J Exp Psychol Hum Percept Perform 26:1639-1656 observed that RTs were slowest when a tobe-localized visual target occurred in the direction of a fixated arrow presented 1 s earlier (i.e., an "inhibitory" Cueing effect; ICE). Here we examined which factor(s) may have allowed the arrow to generate an ICE. Our experiments indicated that the ICE was a side effect of subthreshold response activation attributable to a task-induced association between the arrow and a keypress response. Because the cause of this ICE was more closely related to subthreshold keypress activation than to oculomotor activation, we considered that the effect might be more similar to the negative compatibility effect (NCE) than to inhibition of return (IOR). This similarity raises the possibility that classical IOR, when caused by a spatially uninformative peripheral onset event and measured by a keypress response to a subsequent onset, might represent, in part, another instance of an NCE. Serendipitously, we discovered that context (i.e., whether an uninformative peripheral onset could occur at the time of an uninformative central arrow) ultimately determined whether the "inhibitory" aftermath of automatic response activation would affect output or input pathways.
Taylor and Klein (Journal of Experimental Psychology: Human Perception and Performance 26: [1639]... more Taylor and Klein (Journal of Experimental Psychology: Human Perception and Performance 26: [1639][1640][1641][1642][1643][1644][1645][1646][1647][1648][1649][1650][1651][1652][1653][1654][1655][1656] 2000) discovered two mutually exclusive "flavors" of inhibition of return (IOR): When the oculomotor system is "actively suppressed," IOR affects input processes (the perception/attention flavor), whereas when the oculomotor system is "engaged," IOR affects output processes (the motor flavor). Studies of brain activity with ignored cues have typically reported that IOR reduces an early sensory event-related potential (ERP) component (i.e., the P1 component) of the brain's response to the target. Since eye movements were discouraged in these experiments, the P1 reduction might be a reflection of the perception/attention flavor of IOR. If, instead of ignoring the cue, participants made a prosaccade to the cue (and then returned to fixation) before responding to the target, the motor flavor of IOR should then be generated. We compared these two conditions while monitoring eye position and recording ERPs to the targets. If the P1 modulation is related to the perceptual/ attentional flavor of IOR, we hypothesized that it might be absent when the motoric flavor of IOR was generated by a prosaccade to the cue. Our results demonstrated that targetrelated P1 reductions and behavioral IOR were similar, and significant, in both conditions. However, P1 modulations were significantly correlated with behavioral IOR only when the oculomotor system was actively suppressed, suggesting that P1 modulations may only affect behaviorally exhibited IOR when the attentional/perceptual flavor of IOR is recruited.
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Papers by Jason Satel
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.