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1.  Disconnectivity of the Cortical Ocular Motor Control Network in Autism Spectrum Disorders 
Neuroimage  2012;61(4):1226-1234.
Response inhibition, or the suppression of prepotent but contextually inappropriate behaviors, is essential to adaptive, flexible responding. Individuals with autism spectrum disorders (ASD) consistently show deficient response inhibition during antisaccades. In our prior functional MRI study, impaired antisaccade performance was accompanied by reduced functional connectivity between the frontal eye field (FEF) and dorsal anterior cingulate cortex (dACC), regions critical to volitional ocular motor control. Here we employed magnetoencephalography (MEG) to examine the spectral characteristics of this reduced connectivity. We focused on coherence between FEF and dACC during the preparatory period of antisaccade and prosaccade trials, which occurs after the presentation of the task cue and before the imperative stimulus. We found significant group differences in alpha band mediated coherence. Specifically, neurotypical participants showed significant alpha band coherence between the right inferior FEF and right dACC and between the left superior FEF and bilateral dACC across antisaccade, prosaccade, and fixation conditions. Relative to the neurotypical group, ASD participants showed reduced coherence between these regions in all three conditions. Moreover, while neurotypical participants showed increased coherence between the right inferior FEF and the right dACC in preparation for an antisaccade compared to a prosaccade or fixation, ASD participants failed to show a similar increase in preparation for the more demanding antisaccade. These findings demonstrate reduced long-range functional connectivity in ASD, specifically in the alpha band. The failure in the ASD group to increase alpha band coherence with increasing task demand may reflect deficient top-down recruitment of additional neural resources in preparation to perform a difficult task.
PMCID: PMC3376722  PMID: 22433660
Autism; ASD; Connectivity; Alpha Synchrony; MEG
2.  Neural Processes of Preparatory Control for Stop Signal Inhibition 
Human brain mapping  2011;33(12):2785-2796.
This study investigated the preparatory control of motor inhibition and motor execution using a stop signal task (SST) and functional magnetic resonance imaging (fMRI). In the SST, a frequent “go” signal triggered a prepotent response and a less frequent “stop” signal prompted the inhibition of this response. Preparatory control of motor inhibition and execution in the stop signal trials were examined by contrasting brain activation between stop success and stop error trials during the fore-period, in which participants prepared to respond to go or to stop. Results from 91 healthy adults showed greater activation in the right prefrontal cortex and inferior parietal lobule during preparatory motor inhibition. Preparatory motor execution activated bilateral putamen, primary motor cortices, posterior cingulate cortex, ventromedial prefrontal cortex, and superior temporal/intraparietal sulci. Furthermore, the extents of these inhibition and execution activities were inversely correlated across subjects. On the basis of a median split of the stop signal reaction time (SSRT), subjects with short SSRT showed greater activity in the right orbital frontal cortex during preparatory inhibition. These new findings suggest that the go and stop processes interact prior to target presentation in the SST, in accord with recent computational models of stop signal inhibition.
PMCID: PMC3293936  PMID: 21976392
stop signal; inhibitory control; proactive; prefrontal; race model; go/no-go
3.  The Effect of Three Months of Aerobic Training on Response Preparation in Older Adults 
This study assessed the effects of an aerobic training program on reaction time tasks that manipulated preparatory intervals (PI) to produce temporal preparation effects using short (1, 3, 5 s) and long (5, 7, 9 s) PI. Older adults were assigned to either a 3-month aerobic training group or to a control group. Individuals in the training group participated in an aerobic training program of three 60-min sessions per week. The control group did not receive any training. Results indicated that 12 weeks of aerobic training induced a significant improvement in cardiorespiratory capacity (VO2max estimate). All participants who completed the aerobic program showed improvement after training in the choice RT task, along with enhanced preparation, such that they maintained preparation over time more efficiently after the training program. Moreover, enhanced ability to use the short PI was observed but only in lower fit individuals. Results of the present study suggest that improving aerobic fitness may enhance attentional control mechanisms in older adults.
PMCID: PMC2991190  PMID: 21151355
aging; aerobic training; task complexity; response preparation
4.  Oculomotor and Pupillometric Indices of Pro- and Antisaccade Performance in Youth-Onset Psychosis and Attention Deficit/Hyperactivity Disorder 
Schizophrenia Bulletin  2009;36(6):1167-1186.
The goals of the study were to examine inhibitory deficits on the antisaccade task in 8- to 20-year olds with youth-onset psychosis or attention deficit/hyperactivity disorder (ADHD) and healthy controls and to examine if age-related changes in performance differed across groups. In addition to the conventional measures of performance, pupillary dilations were used to obtain estimates of phasic and tonic level of arousal. Results showed that the psychosis, but not the ADHD, group had elevated antisaccade error rates; however, variability of error rates was high in all groups. These inhibitory failures were accompanied by a lower level of momentary cognitive effort (as indexed by pupillary dilations). The largest differences between the control and clinical groups were found not in the expected indices of inhibition but in the probability of correcting inhibitory errors and in variability of antisaccade response times, which were correlated with each other. These findings did not appear to be attributable to a deficit in maintaining task instructions in mind in either disorder or lack of motivation in ADHD. Instead, results point to impairments in both clinical groups in sustaining attention on a trial-by-trial basis, resulting in deficits in self-monitoring. Thus, results show inhibitory deficits in the context of more general attentional impairments in both disorders.
PMCID: PMC2963044  PMID: 19429843
schizophrenia; antisaccades; inhibition; pupillometry; eye movements
5.  Cortical preparatory activity: representation of movement or first cog in a dynamical machine? 
Neuron  2010;68(3):387-400.
The motor cortices are active during both movement and movement preparation. A common assumption is that preparatory activity constitutes a sub-threshold form of movement activity: a neuron active during rightwards movements becomes modestly active during preparation of a rightwards movement. We asked whether this pattern of activity is in fact observed. We found that it was not: at the level of a single neuron, preparatory tuning was weakly correlated with movement-period tuning. Yet somewhat paradoxically, preparatory tuning could be captured by a preferred direction in an abstract ‘space’ that described the population-level pattern of movement activity. In fact, this relationship accounted for preparatory responses better than did traditional tuning models. These results are expected if preparatory activity provides the initial state of a dynamical system whose evolution produces movement activity. Our results thus suggest that preparatory activity may not represent specific factors, and may instead play a more mechanistic role.
PMCID: PMC2991102  PMID: 21040842
6.  Preparatory Allocation of Attention and Adjustments in Conflict Processing 
NeuroImage  2007;35(2):949-958.
Attentional control involves the ability to allocate preparatory attention to improve subsequent stimulus processing and response selection. There is behavioral evidence to support the hypothesis that increased expectancy of stimulus and response conflict may decrease the subsequent experience of conflict during task performance. We used a cued Flanker and event-related fMRI design to separate processes involved in preparation from those involved in resolving conflict, and to identify the brain systems involved in these processes as well as the association between preparatory activity levels and activity related to subsequent conflict processing. Our results demonstrate that preparatory attentional allocation following a cue to the upcoming level of conflict is mediated by a network involving Dorsolateral Prefrontal Cortex (DLPFC) and the Intraparietal Sulcus (IPS). Informed preparation for conflict processing was associated with decreased Anterior Cingulate Cortex/preSupplementary Motor Area (ACC/preSMA) and IPS activity during the flanker target presentation, supporting their roles in conflict processing and visuospatial attention during the flanker task. Ventrolateral Prefrontal Cortex/Orbitofrontal Cortex (VLPFC/OFC) was active when specific strategic task rule and outcome information was available.
PMCID: PMC2859823  PMID: 17258912
7.  The maturation of task-set related activation supports late developmental improvements in inhibitory control 
The ability to voluntarily inhibit a single response is evident early in development, even as the ability to maintain an inhibitory “task set” continues to improve. To date, functional neuroimaging studies have detailed developmental changes in systems supporting inhibitory control exerted at the single-trial level, but changes underlying the ability to maintain an inhibitory task set remain little understood. Here we present findings from a functional magnetic resonance imaging (fMRI) study that characterizes the development of systems supporting both transient (trial-related) and sustained (task-set-related) activation during performance of the antisaccade (AS) task—an oculomotor test of inhibitory control (Hallett, 1978). Transient activation decreased from childhood to adolescence in regions known to support inhibitory processes and oculomotor control, likely reflecting less effortful response production. In contrast, sustained activation increased to adulthood in regions implicated in control. Our results suggest that development of the ability to maintain a task set is primary to the maturation of inhibitory control, and further, that this ability is still immature in adolescence.
PMCID: PMC2788337  PMID: 19812330
Development; Cognition; Inhibition; Control; Eye movement; Oculomotor; Prefrontal cortex; fMRI
8.  Costs of a Predictable Switch Between Simple Cognitive Tasks Following Severe Closed-Head Injury 
Neuropsychology  2006;20(6):675-684.
The authors used a predictable, externally cued task-switching paradigm to investigate executive control in a severe closed-head injury (CHI) population. Eighteen individuals with severe CHI and 18 controls switched between classifying whether a digit was odd or even and whether a letter was a consonant or vowel on every 4th trial. The target stimuli appeared in a circle divided into 8 equivalent parts. Presentation of the stimuli rotated clockwise. Participants performed the switching task at both a short (200 ms) and a long (1,000 ms) preparatory interval. Although the participants with CHI exhibited slower response times and greater switch costs, similar to controls, additional preparatory time reduced the switch costs, and the switch costs were limited to the 1st trial in the run. These findings indicate that participants with severe CHI were able to take advantage of time to prepare for the task switch, and the executive control processes involved in the switch costs were completed before the 1st trial of the run ended.
PMCID: PMC1779821  PMID: 17100512
closed-head injury; traumatic brain injury; executive functions; task switching; set shifting
9.  Immaturities in Reward Processing and Its Influence on Inhibitory Control in Adolescence 
Cerebral Cortex (New York, NY)  2009;20(7):1613-1629.
The nature of immature reward processing and the influence of rewards on basic elements of cognitive control during adolescence are currently not well understood. Here, during functional magnetic resonance imaging, healthy adolescents and adults performed a modified antisaccade task in which trial-by-trial reward contingencies were manipulated. The use of a novel fast, event-related design enabled developmental differences in brain function underlying temporally distinct stages of reward processing and response inhibition to be assessed. Reward trials compared with neutral trials resulted in faster correct inhibitory responses across ages and in fewer inhibitory errors in adolescents. During reward trials, the blood oxygen level–dependent signal was attenuated in the ventral striatum in adolescents during cue assessment, then overactive during response preparation, suggesting limitations during adolescence in reward assessment and heightened reactivity in anticipation of reward compared with adults. Importantly, heightened activity in the frontal cortex along the precentral sulcus was also observed in adolescents during reward-trial response preparation, suggesting reward modulation of oculomotor control regions supporting correct inhibitory responding. Collectively, this work characterizes specific immaturities in adolescent brain systems that support reward processing and describes the influence of reward on inhibitory control. In sum, our findings suggest mechanisms that may underlie adolescents’ vulnerability to poor decision-making and risk-taking behavior.
PMCID: PMC2882823  PMID: 19875675
adolescence; antisaccade; fMRI; response inhibition; reward
10.  Action-specific Cognitions of Planned and Preparatory Behaviors of Condom Use among Dutch Adolescents 
Archives of Sexual Behavior  2008;37(4):626-640.
Many adolescents fail to use condoms, even when they are motivated to do so. An important reason for their failure to use condoms is that they do not prepare themselves for potential sexual encounters. The present study examined the circumstances under which Dutch adolescents were likely to prepare themselves for condom use (buying and carrying). In a sample of 399 secondary school students, including students with and without sexual experience, it was found that intended condom use was not sufficient to ensure that adolescents plan and prepare for condom use. It was found that having the goal of condom use did not necessarily result in preparatory behavior, such as condom buying and condom carrying. The data showed that action-specific social-cognitive factors of preparatory behavior explained preparatory behavior, beyond the decision to use condoms. This suggests that interventions aimed at promoting condom use should focus not only on condom use itself, but should also motivate and encourage adolescents to buy and carry condoms.
PMCID: PMC2480510  PMID: 18193348
Adolescents; Condom use; Preparatory action; Action-specific cognitions; Planned behavior
11.  Attention, intention, and strategy in preparatory control 
Neuropsychologia  2009;47(7):1670-1685.
The neural mechanisms underlying different forms of preparatory control were examined using event-related fMRI. Preparatory brain activation was monitored in relation to different types of advance information: (1) random task cues indicating which of two possible tasks to perform upon subsequent target presentation, (2) task-ambiguous target stimuli, or 3) targets for which the correct response could be pre-determined. Three types of activation pattern were observed in different brain regions. First, more posterior regions of lateral prefrontal cortex (LPFC) and parietal cortex were activated by both advance task cues and advance targets, but with increased and more sustained activation for the latter. Second, more anterior regions of LPFC and parietal cortex were selectively activated by advance targets. Importantly, in these regions preparatory activation was not further modulated by the availability of advance response information. In contrast, preparatory activation in a third set of brain regions, including medial frontal cortex, reflected the utilization of advance response information, but by only a subset of participants. These results suggest three types of preparatory control: attentional (stimulus-oriented), intentional (action-oriented), and a possibly strategic component that might determine inter-individual differences in response readiness. Notably, the absence of regions selectively or even preferentially activated during cue-based preparation argues against certain conceptualizations of task-selective attention under cued task switching conditions.
PMCID: PMC2674875  PMID: 19397862
12.  Distributed representations of the "preparatory set" in the frontal oculomotor system: a TMS study 
BMC Neuroscience  2008;9:89.
The generation of saccades is influenced by the level of "preparatory set activity" in cortical oculomotor areas. This preparatory activity can be examined using the gap-paradigm in which a temporal gap is introduced between the disappearance of a central fixation target and the appearance of an eccentric target.
Ten healthy subjects made horizontal pro- or antisaccades in response to lateralized cues after a gap period of 200 ms. Single-pulse transcranial magnetic stimulation (TMS) was applied to the dorsolateral prefrontal cortex (DLPFC), frontal eye field (FEF), or supplementary eye field (SEF) of the right hemisphere 100 or 200 ms after the disappearance of the fixation point. Saccade latencies were measured to probe the disruptive effect of TMS on saccade preparation. In six individuals, we gave realistic sham TMS during the gap period to mimic auditory and somatosensory stimulation without stimulating the cortex.
TMS to DLPFC, FEF, or SEF increased the latencies of contraversive pro- and antisaccades. This TMS-induced delay of saccade initiation was particularly evident in conditions with a relatively high level of preparatory set activity: The increase in saccade latency was more pronounced at the end of the gap period and when participants prepared for prosaccades rather than antisaccades. Although the "lesion effect" of TMS was stronger with prefrontal TMS, TMS to FEF or SEF also interfered with the initiation of saccades. The delay in saccade onset induced by real TMS was not caused by non-specific effects because sham stimulation shortened the latencies of contra- and ipsiversive anti-saccades, presumably due to intersensory facilitation.
Our results are compatible with the view that the "preparatory set" for contraversive saccades is represented in a distributed cortical network, including the contralateral DLPFC, FEF and SEF.
PMCID: PMC2564971  PMID: 18801205
13.  Saccadic Preparation in the Frontal Eye Field Is Modulated by Distinct Trial History Effects as Revealed by Magnetoencephalography 
Cerebral Cortex (New York, NY)  2010;21(2):245-253.
Optimizing outcomes involves rapidly and continuously adjusting behavior based on context. While most behavioral studies focus on immediate task conditions, responses to events are also influenced by recent history. We used magnetoencephalography and a saccadic paradigm to investigate the neural bases of 2 trial history effects that are well characterized in the behavioral eye movement literature: task-switching and the prior-antisaccade effect. We found that switched trials were associated with increased errors and transient increases in activity in the frontal eye field (FEF) and anterior cingulate cortex early in the preparatory period. These activity changes are consistent with active reconfiguration of the task set, a time-limited process that is triggered by the instructional cue. Following an antisaccade versus prosaccade, there was increased activity in the FEF and prefrontal cortex that persisted into the preparatory period of the subsequent trial, and saccadic latencies were prolonged. We attribute these effects to persistent inhibition of the ocular motor response system from the prior antisaccade. These findings refine our understanding of how trial history interacts with current task demands to adjust responses. Such dynamic modulations of neural activity and behavior by recent experience are at the heart of adaptive flexible behavior.
PMCID: PMC3020577  PMID: 20522539
antisaccade; frontal eye field; magnetoencephalography; saccade; task-switching
14.  Evidence for two concurrent inhibitory mechanisms during response preparation 
Inhibitory mechanisms are critically involved in goal-directed behaviors. To gain further insight into how such mechanisms shape motor representations during response preparation, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) and H-reflexes were recorded from left hand muscles during choice reaction time tasks. The imperative signal, which indicated the required response, was always preceded by a preparatory cue. During the post-cue delay period, left MEPs were suppressed when the left hand had been cued for the forthcoming response, suggestive of a form of inhibition specifically directed at selected response representations. H-reflexes were also suppressed on these trials, indicating that the effects of this inhibition extend to spinal circuits. In addition, left MEPs were suppressed when the right hand was cued, but only when left hand movements were a possible response option before the onset of the cue. Notably, left hand H-reflexes were not modulated on these trials, consistent with a cortical locus of inhibition that lowers the activation of task-relevant, but non-selected responses. These results suggest the concurrent operation of two inhibitory mechanisms during response preparation: one decreases the activation of selected responses at the spinal level, helping to control when selected movements should be initiated by preventing their premature release; a second, upstream mechanism helps to determine what response to make during a competitive selection process.
PMCID: PMC2852647  PMID: 20220014
cognitive control; competition; corticospinal excitability; decision-making; response selection; transcranial magnetic stimulation; H-reflex
15.  Antisaccade performance in schizophrenia: a neural model of decision making in the superior colliculus 
Antisaccade performance deficits in schizophrenia are generally interpreted as an impaired top–down inhibitory signal failing to suppress the erroneous response. We recorded the antisaccade performance (error rates and latencies) of healthy and schizophrenia subjects performing the mirror antisaccade task. A neural rise-to-threshold model of antisaccade performance was developed to uncover the biophysical mechanisms giving rise to the observed deficits in schizophrenia. Schizophrenia patients displayed greater variability in the antisaccade and corrected antisaccade latency distributions, increased error rates and decreased corrected errors, relative to healthy participants. Our model showed that (1) increased variability is due to a more noisy accumulation of information by schizophrenia patients, but their confidence level required before making a decision is unaffected, and (2) competition between the correct and erroneous decision processes, and not a third top-down inhibitory signal suppressing the erroneous response, accounts for the antisaccade performance of healthy and schizophrenia subjects. Local competition further ensured that a correct antisaccade is never followed by an error prosaccade.
PMCID: PMC3920187  PMID: 24574953
antisaccade performance; rise-to-threshold model; neural model; superior colliculus; eye movements; schizophrenia
16.  Preparatory neural activity predicts performance on a conflict task 
Brain research  2007;1176:92-102.
Advance preparation has been shown to improve the efficiency of conflict resolution. Yet, with little empirical work directly linking preparatory neural activity to the performance benefits of advance cueing, it is not clear whether this relationship results from preparatory activation of task-specific networks, or from activity associated with general alerting processes. Here, fMRI data were acquired during a spatial Stroop task in which advance cues either informed subjects of the upcoming relevant feature of conflict stimuli (spatial or semantic) or were neutral. Informative cues decreased reaction time (RT) relative to neutral cues, and cues indicating that spatial information would be task-relevant elicited greater activity than neutral cues in multiple areas, including right anterior prefrontal and bilateral parietal cortex. Additionally, preparatory activation in bilateral parietal cortex and right dorsolateral prefrontal cortex predicted faster RT when subjects responded to spatial location. No regions were found to be specific to semantic cues at conventional thresholds, and lowering the threshold further revealed little overlap between activity associated with spatial and semantic cueing effects, thereby demonstrating a single dissociation between activations related to preparing a spatial versus semantic task-set. This relationship between preparatory activation of spatial processing networks and efficient conflict resolution suggests that advance information can benefit performance by leading to domain-specific biasing of task-relevant information.
PMCID: PMC2288660  PMID: 17889835
attention; cognitive control; advance preparation; feature biasing; conflict; Stroop
17.  Cognitive-electrophysiological indices of attentional and inhibitory processing in adults with ADHD: familial effects 
Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that starts in childhood and frequently persists in adults. In a comparison of adults with ADHD and a matched control sample, we previously showed that abnormal inhibitory processing is typically preceded or accompanied by other processing deficits in adult ADHD. We now compare these data further to additional data from first-degree relatives (fathers) of children with ADHD to identify whether this pattern of abnormal processing shares familial influences with ADHD in adults.
Using a family design, we compared 20 fathers of children with the combined subtype of ADHD with 21 adults with ADHD combined subtype and 20 controls in event-related potential indices of preparatory states and subsequent response inhibition processing as elicited by a cued continuous performance task.
Fathers of children with ADHD exhibited significantly weaker orienting attention to cues and inhibitory processing than the controls but not the ADHD sample.
These findings provide evidence for the familial association of attentional orienting and response inhibition processes with ADHD in adults and indicate a familial and neurobiological link between ADHD in children and adults.
PMCID: PMC3168399  PMID: 21752266
18.  Strengthening of Top-Down Frontal Cognitive Control Networks Underlying the Development of Inhibitory Control: An fMRI Effective Connectivity Study 
The ability to voluntarily inhibit responses to task irrelevant stimuli, which is a fundamental component of cognitive control, has a protracted development through adolescence. Prior human developmental imaging studies have found immaturities in localized brain activity in children and adolescents. However, little is known about how these regions integrate with age to form the distributed networks known to support cognitive control. In the present study, we used Granger Causality analysis to characterize developmental changes in effective connectivity underlying inhibitory control (antisaccade task) compared to reflexive responses (prosaccade task) in human participants. By childhood few top-down connectivity were evident with increased parietal interconnectivity. By adolescence connections from prefrontal cortex increased and parietal interconnectivity decreased in number. From adolescence to adulthood there was evidence of increased number and strength of frontal connections to cortical regions as well as subcortical regions. Taken together, results suggest that developmental improvements in inhibitory control may be supported by age related enhancements in top-down effective connectivity between frontal, oculomotor and subcortical regions.
PMCID: PMC2995693  PMID: 21084608
Development; Cognitive Control; Oculomotor; connectivity; fMRI
19.  Effects of brief yoga exercises and motivational preparatory interventions in distance runners: results of a controlled trial 
To examine the efficacy of two preparatory interventions on one mile run performance in 90 high school long distance runners.
After participants had completed a one mile baseline run, they were randomly assigned to participate in either one of two interventions (brief yoga exercises, motivational shouting exercises) or a no intervention control condition. Experimental conditions were implemented one week after the baseline run about 20 minutes before a second one mile trial.
Participants assigned to the motivational intervention improved their running performance significantly more than those assigned to the other two conditions. Although the magnitude of the effect was small, participants assigned to yoga exercises showed significant improvements in running performance relative to control condition participants. Consumer satisfaction ratings indicated that participants who were assigned to the motivational and yoga exercise groups liked their interventions more than those assigned to the control group.
Motivational and yoga interventions designed to improve long distance running performance were equally acceptable to the participants, but the former had a greater effect.
PMCID: PMC2491926  PMID: 16371493
psychology; yoga; intervention; control; motivation
20.  Failing to Forget: Prospective Memory Commission Errors Can Result from Spontaneous Retrieval and Impaired Executive Control 
Prospective memory (PM) research typically examines the ability to remember to execute delayed intentions but often ignores the ability to forget finished intentions. We had participants perform (or not perform; control group) a PM task and then instructed them that the PM task was finished. We later (re)presented the PM cue. Approximately 25% of participants made a commission error, the erroneous repetition of a PM response following intention completion. Comparisons between the PM groups and control group suggested that commission errors occurred in the absence of preparatory monitoring. Response time analyses additionally suggested that some participants experienced fatigue across the ongoing task block, and those who did were more susceptible to making a commission error. These results supported the hypothesis that commission errors can arise from the spontaneous retrieval of finished intentions and possibly the failure to exert executive control to oppose the PM response.
PMCID: PMC3598897  PMID: 22799284
Prospective memory; commission errors; spontaneous retrieval; fatigue; forgetting; executive control
21.  ERP correlates of shared control mechanisms involved in saccade preparation and in covert attention 
Brain Research  2007;1135(8-3):154-166.
We investigated whether attention shifts and eye movement preparation are mediated by shared control mechanisms, as claimed by the premotor theory of attention. ERPs were recorded in three tasks where directional cues presented at the beginning of each trial instructed participants to direct their attention to the cued side without eye movements (Covert task), to prepare an eye movement in the cued direction without attention shifts (Saccade task) or both (Combined task). A peripheral visual Go/Nogo stimulus that was presented 800 ms after cue onset signalled whether responses had to be executed or withheld. Lateralised ERP components triggered during the cue–target interval, which are assumed to reflect preparatory control mechanisms that mediate attentional orienting, were very similar across tasks. They were also present in the Saccade task, which was designed to discourage any concomitant covert attention shifts. These results support the hypothesis that saccade preparation and attentional orienting are implemented by common control structures. There were however systematic differences in the impact of eye movement programming and covert attention on ERPs triggered in response to visual stimuli at cued versus uncued locations. It is concluded that, although the preparatory processes underlying saccade programming and covert attentional orienting may be based on common mechanisms, they nevertheless differ in their spatially specific effects on visual information processing.
PMCID: PMC2248222  PMID: 17198687
Spatial attention; Eye movements; Attentional control; Vision; Event-related brain potentials
22.  ERP correlates of shared control mechanisms involved in saccade preparation and in covert attention 
Brain research  2007;1135(1):154-166.
We investigated whether attention shifts and eye movement preparation are mediated by shared control mechanisms, as claimed by the premotor theory of attention. ERPs were recorded in three tasks where directional cues presented at the beginning of each trial instructed participants to direct their attention to the cued side without eye movements (Covert task), to prepare an eye movement in the cued direction without attention shifts (Saccade task), or both (Combined task). A peripheral visual Go/Nogo stimulus that was presented 800 ms after cue onset signalled whether responses had to be executed or withheld. Lateralised ERP components triggered during the cue-target interval, which are assumed to reflect preparatory control mechanisms that mediate attentional orienting, were very similar across tasks. They were also present in the Saccade task, which was designed to discourage any concomitant covert attention shifts. These results support the hypothesis that saccade preparation and attentional orienting are implemented by common control structures. There were however systematic differences in the impact of eye movement programming and covert attention on ERPs triggered in response to visual stimuli at cued versus uncued locations. It is concluded that although the preparatory processes underlying saccade programming and covert attentional orienting may be based on common mechanisms, they nevertheless differ in their spatially specific effects on visual information processing.
PMCID: PMC2248222  PMID: 17198687
Spatial attention; Eye movements; Attentional control; Vision; Event-related brain potentials
23.  Pre-cue Fronto-Occipital Alpha Phase and Distributed Cortical Oscillations Predict Failures of Cognitive Control 
The Journal of Neuroscience  2012;32(20):7034-7041.
Cognitive control is required for correct performance on antisaccade tasks, including the ability to inhibit an externally driven ocular motor repsonse (a saccade to a peripheral stimulus) in favor of an internally driven ocular motor goal (a saccade directed away from a peripheral stimulus). Healthy humans occasionally produce errors during antisaccade tasks, but the mechanisms associated with such failures of cognitive control are uncertain. Most research on cognitive control failures focuses on post-stimulus processing, although a growing body of literature highlights a role of intrinsic brain activity in perceptual and cognitive performance. The current investigation used dense array electroencephalography and distributed source analyses to examine brain oscillations across a wide frequency bandwidth in the period prior to antisaccade cue onset. Results highlight four important aspects of ongoing and preparatory brain activations that differentiate error from correct antisaccade trials: (i) ongoing oscillatory beta (20–30Hz) power in anterior cingulate prior to trial initiation (lower for error trials), (ii) instantaneous phase of ongoing alpha-theta (7Hz) in frontal and occipital cortices immediately before trial initiation (opposite between trial types), (iii) gamma power (35–60Hz) in posterior parietal cortex 100 ms prior to cue onset (greater for error trials), and (iv) phase locking of alpha (5–12Hz) in parietal and occipital cortices immediately prior to cue onset (lower for error trials). These findings extend recently reported effects of pre-trial alpha phase on perception to cognitive control processes, and help identify the cortical generators of such phase effects.
PMCID: PMC3404822  PMID: 22593071
antisaccades; alpha; phase; frontal; parietal; EEG
24.  Effects of Magnitude and Magnitude Predictability of Postural Perturbations on Preparatory Cortical Activity in Older Adults with and without Parkinson’s Disease 
The goal of this study was to identify whether impaired cortical preparation may relate to impaired scaling of postural responses of people with Parkinson’s disease (PD). We hypothesized that impaired scaling of postural responses in participants with PD would be associated with impaired set-dependent cortical activity in preparation for perturbations of predictable magnitudes. Participants performed postural responses to backward surface translations. We examined the effects of perturbation magnitude (predictable small vs. predictable large) and predictability of magnitude (predictable vs. unpredictable-in-magnitude) on postural responses (center-of-pressure (CoP) displacements) and on preparatory electroencephalographic (EEG) measures of contingent negative variation (CNV) and alpha and beta event-related desynchronization (ERD). Our results showed that unpredictability of perturbation magnitude, but not the magnitude of the perturbation itself, was associated with increased CNV amplitude at the CZ electrode in both groups. While control participants scaled their postural responses to the predicted magnitude of the perturbation, their condition-related changes in CoP displacements were not correlated with condition-related changes in EEG preparatory activity (CNV or ERD). In contrast, participants with PD did not scale their postural responses to the predicted magnitude of the perturbation, but they did demonstrate greater beta ERD in the condition of predictably small-magnitude perturbations and greater beta ERD than the control participants at the CZ electrode. In addition, increased beta ERD in PD was associated with decreased adaptability of postural responses, suggesting that preparatory cortical activity may have a more direct influence on postural response scaling for people with PD than for control participants.
PMCID: PMC3472959  PMID: 22936099
Parkinson’s disease; electroencephalography; contingent negative variation; event related desynchronization; posture; preparation
25.  Oculomotor Performance Identifies Underlying Cognitive Deficits in Attention-Deficit/Hyperactivity Disorder 
To evaluate cognitive control in children with attention-deficit/hyperactivity disorder (ADHD) using oculomotor tests of executive function.
Cross-sectional study of children aged 8 to 13 years with ADHD (n = 26) and controls (n = 33) used oculomotor tasks to assess sensorimotor function (visually guided saccades), resistance to peripheral distractors (fixation), response inhibition (antisaccades), and spatial working memory (memory-guided saccades).
All children had intact sensorimotor function and working memory. Children with ADHD showed susceptibility to peripheral distractors and deficits in response inhibition. Increased interstimulus (IS) fixation periods on the antisaccade task were associated with improved performance and decreased reaction times on correct trials for controls but not for children with ADHD. Attention-deficit/hyperactivity disorder–combined and inattentive subtypes showed different patterns of reaction time as a function of IS periods.
Response inhibition deficits in ADHD on oculomotor tasks are consistent with other studies. The failure of children with ADHD to use IS time to decrease response inhibition errors and reaction time suggests that IS time is not used to prepare a response. These findings highlight the importance of considering cognitive processing components affected by ADHD in addition to core behavioral symptoms, particularly in designing new treatment strategies.
PMCID: PMC3045710  PMID: 19238098
ADHD; oculomotor; antisaccade; response inhibition; response preparation

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