Covert Orienting Of Visuospatial Attention Research Articles

Representational coding of overt and covert orienting of visuospatial attention in the frontoparietal network

Orienting of visuospatial attention refers to reallocation of attentional focus from one target or location to another and can occur either with (overt) or without (covert) eye movement. Although it has been demonstrated that both types of orienting commonly involve frontal and parietal brain regions as the frontoparietal network (FPN), the underlying representational coding of these two types of orienting remains unclear. In this functional magnetic resonance imaging study, participants performed a task that elicited overt and covert orienting to endogenously or exogenously cued targets with eye-tracking to monitor eye movement. Although the FPN was commonly activated for both overt and covert orienting, multivariate patterns of the activation of voxels in the FPN accurately predicted whether eye movements were involved or not during orienting. These overt- and covert-preferred voxels were topologically distributed as distinct and interlaced clusters in a millimeter scale. Inclusion of the two types of clusters predicted orienting type more accurately than one type of clusters alone. These findings suggest that overt and covert orienting are represented by interdependent functional clusters of neuronal populations in regions of the FPN, which might reflect a generalizable principle in the nervous system for functional organization of closely associated processes.

Improving the efficacy of ERP-based BCIs using different modalities of covert visuospatial attention and a genetic algorithm-based classifier.

We investigated whether the covert orienting of visuospatial attention can be effectively used in a brain-computer interface guided by event-related potentials. Three visual interfaces were tested: one interface that activated voluntary orienting of visuospatial attention and two interfaces that elicited automatic orienting of visuospatial attention. We used two epoch classification procedures. The online epoch classification was performed via Independent Component Analysis, and then it was followed by fixed features extraction and support vector machines classification. The offline epoch classification was performed by means of a genetic algorithm that permitted us to retrieve the relevant features of the signal, and then to categorise the features with a logistic classifier. The offline classification, but not the online one, allowed us to differentiate between the performances of the interface that required voluntary orienting of visuospatial attention and those that required automatic orienting of visuospatial attention. The offline classification revealed an advantage of the participants in using the “voluntary” interface. This advantage was further supported, for the first time, by neurophysiological data. Moreover, epoch analysis was performed better with the “genetic algorithm classifier” than with the “independent component analysis classifier”. We suggest that the combined use of voluntary orienting of visuospatial attention and of a classifier that permits feature extraction ad personam (i.e., genetic algorithm classifier) can lead to a more efficient control of visual BCIs.

Deficits in the covert orienting of attention in children with Developmental Coordination Disorder: Does severity of DCD count?

Children with Developmental Coordination Disorder (DCD) show deficits in the covert orienting of visuospatial attention, suggesting an underlying issue in attentional disengagement and/or inhibitory control. However, an important theoretical issue that remains unclear is whether the pattern of deficits varies with DCD severity. Fifty-one children with moderate DCD (MDCD), 24 children with severe DCD (SDCD), and 38 typically developing (TD) children participated in the study. Their performance was compared on the covert orienting of visuospatial attention task (COVAT), specifically the voluntary control mode. Results showed that the pattern of performance differed between groups. At a short stimulus-response asynchrony (350 ms), the difference in response times for validly and invalidly cued trials was similar for all three groups. However, at the longer SOA (800 ms), both DCD groups continued to show a relative disadvantage for responses that followed invalid cues. This suggests that a deficit in response inhibition and/or attentional disengagement is manifest in children with both moderate and severe DCD. The implications of these findings for theory and treatment are discussed.

Motor output evoked by subsaccadic stimulation of primate frontal eye fields

In addition to its role in shifting the line of sight, the oculomotor system is also involved in the covert orienting of visuospatial attention. Causal evidence supporting this premotor theory of attention, or oculomotor readiness hypothesis, comes from the effect of subsaccadic threshold stimulation of the oculomotor system on behavior and neural activity in the absence of evoked saccades, which parallels the effects of covert attention. Here, by recording neck-muscle activity from monkeys and systematically titrating the level of stimulation current delivered to the frontal eye fields (FEF), we show that such subsaccadic stimulation is not divorced from immediate motor output but instead evokes neck-muscle responses at latencies that approach the minimal conduction time to the motor periphery. On average, neck-muscle thresholds were approximately 25% lower than saccade thresholds, and this difference is larger for FEF sites associated with progressively larger saccades. Importantly, we commonly observed lower neck-muscle thresholds even at sites evoking saccades <or=5 degrees in magnitude, although such small saccades are not associated with head motion. Neck-muscle thresholds compare well with the current levels used in previous studies to influence behavior or neural activity through activation of FEF neurons feeding back to extrastriate cortex. Our results complement this previous work by suggesting that the neurobiologic substrate that covertly orients visuospatial attention shares this command with head premotor circuits in the brainstem, culminating with recruitment in the motor periphery.

Response-Dependent Contributions of Human Primary Motor Cortex and Angular Gyrus to Manual and Perceptual Sequence Learning

Motor sequence learning on the serial reaction time task involves the integration of response-, stimulus-, and effector-based information. Human primary motor cortex (M1) and the inferior parietal lobule (IPL) have been identified with supporting the learning of effector-dependent and -independent information, respectively. Current neurocognitive data are, however, exclusively based on learning complex sequence information via perceptual-motor responses. Here, we investigated the effects of continuous theta-burst transcranial magnetic stimulation (cTBS)-induced disruption of M1 and the angular gyrus (AG) of the IPL on learning a probabilistic sequence via sequential perceptual-motor responses (experiment 1) or covert orienting of visuospatial attention (experiment 2). Functional effects on manual sequence learning were evident during 75% of training trials in the cTBS M1 condition, whereas cTBS over the AG resulted in interference confined to a midpoint during the training phase. Posttraining direct (declarative) tests of sequence knowledge revealed that cTBS over M1 modulated the availability of newly acquired sequence knowledge, whereby sequence knowledge was implicit in the cTBS M1 condition but was available to conscious awareness in the cTBS AG and control conditions. In contrast, perceptual sequence learning was abolished in the perceptual cTBS AG condition, whereas learning was intact and available to conscious awareness in the cTBS M1 and control conditions. These results show that the right AG had a critical role in perceptual sequence learning, whereas M1 had a causal role in developing experience-dependent functional attributes relevant to conscious knowledge on manual but not perceptual sequence learning.

Neurocognitive dysfunction in antidepressant-free, non-elderly patients with unipolar depression: Alerting and covert orienting of visuospatial attention

Background Cognition is impaired across various domains in young and middle-age adults with unipolar depression. Performance appears in general worse in effortful tasks requiring executive function and attention. Probing specific cognitive operations in depressed patients, such as alerting and covert orienting of visuospatial attention, can better define and characterize the pathophysiology. Methods Nine antidepressant-free, clinically depressed patients and fourteen age-matched healthy subjects performed a Posner task with components of phasic alerting and covert orienting of visuospatial attention. Reaction times were analyzed by repeated-measures ANOVA with DIAGNOSIS as the between-group measure. Visual field (FIELD), stimulus onset asynchrony (SOA), and orienting CUE condition were within-subject, repeated measures. Results ANOVA showed intact attentional orienting in both groups. There were no FIELD differences across groups nor main effects of DIAGNOSIS. Interactions of DIAGNOSIS with SOA and DIAGNOSIS with CUE condition identified a phasic alerting deficit in the depressed patients. There were no significant effects of time-on-task, suggesting adequate vigilance or sustained attention in both groups. Plotting depressed versus control subjects' reaction time for each task condition (Brinley plot) showed linearity with a slope of 1.6 (i.e., patients were 1.6-fold slower) and a correlation coefficient of 0.98 (accounting for 96% of the overall variance). Limitations This study contains a small sample with potential for Type II error. The study addressed depression at the syndrome level. Depressed patients selected on particular symptom dimensions (e.g., anxiety, psychomotor retardation, etc.) could reveal abnormalities in hemisphere asymmetries that were not observed here. Conclusions These data highlight that global slowing is a major cognitive deficit in depression and arises across levels of difficulty. Putative specific deficits in depression need adjustment for the large effects of global slowing which can mimic selective impairments in more effortful task conditions.

Covert orienting of visuospatial attention in the early stages of aging.

Electrophysiological and behavioral responses were recorded in healthy young (19-23 years) and older (56-66 years) subjects during the execution of a visuospatial attention task. The objective was to test whether covert orienting of visuospatial attention (COVAT) is sensitive to the early stages of aging. All subjects responded faster to targets following valid than invalid cues. The amplitude of the P1 component of visual event-related potentials (ERP) was larger to targets following central valid cues at all SOAs. Subtle age-related changes were observed in P1 amplitude under peripheral cueing. Furthermore, older subjects presented longer reaction times (RTs) and lower P1 amplitudes regardless of the attention condition.

Peripheral oculomotor palsy affects orienting of visuospatial attention.

Patients affected by VI cranial nerve palsy were required to orient their attention in monocular vision and to detect a stimulus appearing either in attended or in unattended locations. Results showed that while during non-paretic eye vision stimulus detection in the attended location was faster than that in the unattended one, during paretic eye vision no difference in detection speed was present. However, in this latter condition, detection speed in both attended and un attended locations were as fast as that measured during non-paretic eye vision in attended location. Demonstration that peripheral oculomotor impairment influences monocular covert orienting of visuospatial attention strongly support the idea that visuospatial attention and oculomotor mechanisms share similar cortical networks.

Focusing of Visuospatial Attention

Abstract In the present study we explored the focusing of visuospatial attention in subjects practicing and not practicing activities with high attentional demands. Similar to the studies of Castiello and Umiltà (e. g., 1990) , our experimental procedure was a variation of Posner's (1980) basic paradigm for exploring covert orienting of visuospatial attention. In a simple RT-task, a peripheral cue of varying size was presented unilaterally or bilaterally from a central fixation point and followed by a target at different stimulus-onset-asynchronies (SOAs). The target could occur validly inside the cue or invalidly outside the cue with varying spatial relation to its boundary. Event-related brain potentials (ERPs) and reaction times (RTs) were recorded to target stimuli under the different task conditions. RT and ERP findings showed converging aspects as well as dissociations. Electrophysiological results revealed an amplitude modulation of the ERPs in the early and late Nd time interval at both anterior and posterior scalp sites, which seems to be related to the effects of peripheral informative cues as well as to the attentional expertise. Results were: (1) shorter latency effects confirm the positive-going amplitude enhancement elicited by unilateral peripheral cues and strengthen the criticism against the neutrality of spatially nonpredictive peripheral cueing of all possible target locations which is often presumed in behavioral studies. (2) Longer latency effects show that subjects with attentional expertise modulate the distribution of the attentional resources in the visual space differently than nonexperienced subjects. Skilled practice may lead to minimizing attentional costs by automatizing the use of a span of attention that is adapted to the most frequent task demands and endogenously increases the allocation of resources to cope with less usual attending conditions.

Spatial Attention Deficits in Patients with Acquired or Developmental Cerebellar Abnormality

Recent imaging and clinical studies have challenged the concept that the functional role of the cerebellum is exclusively in the motor domain. We present evidence of slowed covert orienting of visuospatial attention in patients with developmental cerebellar abnormality (patients with autism, a disorder in which at least 90% of all postmortem cases reported to date have Purkinje neuron loss), and in patients with cerebellar damage acquired from tumor or stroke. In spatial cuing tasks, normal control subjects across a wide age range were able to orient attention within 100 msec of an attention-directing cue. Patients with cerebellar damage showed little evidence of having oriented attention after 100 msec but did show the effects of attention orienting after 800-1200 msec. These effects were demonstrated in a task in which results were independent of the motor response. In this task, smaller cerebellar vermal lobules VI-VII (from magnetic resonance imaging) were associated with greater attention-orienting deficits. Although eye movements may also be disrupted in patients with cerebellar damage, abnormal gaze shifting cannot explain the timing and nature of the attention-orienting deficits reported here. These data may be consistent with evidence from animal models that suggest damage to the cerebellum disrupts both the spatial encoding of a location for an attentional shift and the subsequent gaze shift. These data are also consistent with a model of cerebellar function in which the cerebellum supports a broad spectrum of brain systems involved in both nonmotor and motor function.

Deficits in the endogenous control of covert visuospatial attention in children with developmental coordination disorder

Deficits in the covert orienting of visuospatial attention have been reported in children with Developmental Coordination Disorder (DCD). Using two new versions of the covert orienting of visuospatial attention task (COVAT), the study presented here sought to investigate how generalised deficits are in this domain by using longer time intervals between cue and imperative stimulus. Twenty children with DCD and 20 controls were tested on two different COVATs with the interval between cue and peripheral imperative stimulus (or stimulus onset asynchrony, SOA) of 150 and 850 ms presented in a random sequence: the first used peripheral cues and no probability information (exogenous mode) and the second used central cues and an 80% probability that imperative stimuli would appear at the cued location (endogenous mode). Results showed that the time course of covert orienting to peripheral cues was normal in both groups. For central cues, however, children with DCD were more disadvantaged by invalid cues compared with controls, regardless of SOA; this finding was consistent with a deficit in the disengage operation of directing covert attention. These results confirm and extend our earlier finding that impairments in the endogenous control of covert visuospatial attention exist in children with DCD. PsycINFO classification: 2820; 2330; 2346; 3250

Modulation of the Spatial Extent of the Attentional Focus in High-level Volleyball Players

In this study, we explored the ability of first league professional volleyball players to modulate the allocation of attentional resources in the visual space by adapting the size of the attentional focus. Like Castiello and Umilta (1990), we employed an experimental procedure that is a variation of Posner's (1980) paradigm for exploring covert orienting of visuospatial attention. In a signalled reaction time task, a peripheral cue of varying size was presented unilaterally or bilaterally of a central fixation point, followed by a target at different stimulus onset asynchronies. The target could occur validly inside the cue or invalidly outside it with varying spatial relation to its boundary. Our results suggest that volleyball players are better able than controls to modulate the distribution of attentional resources within and around peripherally cued areas. Moreover, volleyball players seem to be able to flexibly adapt the gradient of attentional resources around the cued area, as would be expected from their sport practice.

Covert orienting of visuospatial attention in children with developmental coordination disorder.

It is still unclear whether impairments in visuospatial processing in children with developmental coordination disorder (DCD) are a consequence of their motor deficits or are independent of them. In two experiments, 20 children with DCD and 20 matched controls were tested on the covert orienting of a visuospatial attention task (COVAT). Experiment 1 used a COVAT with peripheral cues and an 80% probability that targets would appear at the cued location. While the results suggested a deficit in the disengage operation of orienting covert attention for the DCD group, they were difficult to reconcile with models of covert orienting and the results of past research. Experiment 2 tested subjects on two new versions of the COVAT: the first used peripheral cues and no probability information (exogenous mode), and the second used central cues and an 80% probability that targets would appear at the cued location (endogenous mode). The DCD group displayed attentional orienting deficits only for the endogenous mode. These results suggest that impairments in the endogenous control of visuospatial attention are independent of motor deficits in DCD.

Inhibition of return and visuospatial attention in healthy older adults and individuals with dementia of the Alzheimer type.

Covert orienting of visuospatial attention in response to peripherally presented cues was assessed in healthy younger and older adults and those with dementia of the Alzheimer type (DAT) during a simple detection task. The results yield both an age-related increase (Experiments 1 and 2) and a DAT-related increase (Experiment 2) in the facilitatory effect of a single peripheral cue on detection. By contrast, equivalent inhibition of return (i.e., a slowing of target detection at previously cued locations) was observed for all 3 groups when a 2nd cue was presented at central fixation. Results suggest that both healthy older adults and individuals with DAT experience changes in the posterior attention system thought to subserve visuospatial attention. Results also suggest limitations on the generality of inhibitory deficits in healthy aging and DAT.