The gap effect during visual and auditory stimulation using manual responses

The gap effect reduces both manual and saccadic inhibition of return (IOR)

Inhibition of return (IOR) is the effect of slower responses to validly than invalidly cued targets. The discovery of IOR raised controversy as to whether it has two “flavors”, i.e., attentional/perceptual and motoric, or whether it is a homogeneous visual-motor phenomenon that should be understood in terms of the preparation of different effectors (mainly eye movement). Since manipulation of fixation offset (0 and 200 ms gap) is believed to affect the latency of saccades, we measured its influence on saccadic and manual IOR with a simple keypress response when eye movements were forbidden. In the two experiments which we carried out, the fixation offset decreased IOR in both the saccadic and the manual conditions. The results suggest the limitations of the attentional hypothesis, which assumes that manual IOR is independent of the motoric component; they are also in line with the tenets of the oculomotor hypothesis of IOR.

Are there right hemisphere contributions to visually-guided movement? Manipulating left hand reaction time advantages in dextrals

Many studies have argued for distinct but complementary contributions from each hemisphere in the control of movements to visual targets. Investigators have attempted to extend observations from patients with unilateral left- and right-hemisphere damage, to those using neurologically-intact participants, by assuming that each hand has privileged access to the contralateral hemisphere. Previous attempts to illustrate right hemispheric contributions to the control of aiming have focussed on increasing the spatial demands of an aiming task, to attenuate the typical right hand advantages, to try to enhance a left hand reaction time advantage in right-handed participants. These early attempts have not been successful. The present study circumnavigates some of the theoretical and methodological difficulties of some of the earlier experiments, by using three different tasks linked directly to specialized functions of the right hemisphere: bisecting, the gap effect, and visuospatial localization. None of these tasks were effective in reducing the magnitude of left hand reaction time advantages in right handers. Results are discussed in terms of alternatives to right hemispheric functional explanations of the effect, the one-dimensional nature of our target arrays, power and precision given the size of the left hand RT effect, and the utility of examining the proportions of participants who show these effects, rather than exclusive reliance on measures of central tendency and their associated null hypothesis significance tests.

What happens during the stimulus onset asynchrony in the dot-probe task? Exploring the role of eye movements in the assessment of attentional biases

The dot-probe paradigm is one of the most often used paradigms to investigate attentional biases towards emotional information. However, a large number of the dot-probe studies so far used a long stimulus onset asynchrony allowing for eye movements to occur, which might increase the error variance. This study aimed at addressing this methodological issue by varying the instructions with regard to the gaze behavior and calculating the reaction time (RT) bias score (i.e., RTs for targets presented at the location of the emotional compared to the neutral stimulus) separately for trials with eye movements and trials without eye movements. Results of Experiment 1 (using typical instructions, i.e., instructions that are lenient with regard to eye movements) showed an RT bias, but only in the trials without eye movements The overall RT bias (calculated "blind" for eye movements) was non-significant. In Experiment 2, stricter instructions and small changes in the procedure led to a sharp decrease in the number of eye movements, such that both the RT bias in the trials without eye movements as well as the RT bias across all trials was significant.

Cortical dynamics during the preparation of antisaccadic and prosaccadic eye movements in humans in a gap paradigm

To compare the cortical dynamics of different oculomotor tasks, EEG and eye movements were recorded in 21 volunteers. Using a comprehensive approach, subjects were asked to perform saccadic tasks, which included a saccadic eye movement to a peripheral target (prosaccadic), a movement to the opposite side (antisaccadic), or maintain the gaze fixed (no-go). In mixed trials, prosaccadic, antisaccadic and no-go tasks were indicated by a color square (S1) present for 1900-2500 ms (instructive period). S1 disappeared for 370 ms (gap) and a black dot at 8 deg at right or left indicated the beginning of the task. Reaction times, amplitude of eye movements and number of errors were greatest in antisaccadic tasks, suggesting a greater difficulty. The EEG showed a contingent negativity variation (CNV) that increased progressively along the instructive period and suddenly during the gap: higher in antisaccadic, followed by prosaccadic and no-go tasks. Principal component analysis (PCA) disentangled fronto-central and occipital CNV-related and fronto-central gap-related components. The instructive period was characterized by fronto-central and occipital beta desynchronization (ERD) higher in antisaccadic than in no-go and parieto-occipital alpha synchronization higher in no-go than in antisaccadic tasks. During the gap, parieto-occipital beta and alpha ERD were higher in antisaccadic compared to no-go. The gap was further characterized by a fronto-central increase of inter-trial coherence in theta: highest during antisaccadic, followed by prosaccadic and no-go tasks. This phase locking in theta was also accompanied by theta ERS, which was significantly higher in antisaccadic than in the other two tasks. In PCA of spectral power two main components had dynamics similar to those extracted from voltage data, suggesting cross-frequency coupling. These results suggest that the more difficult saccadic tasks are associated with top-down control mediated by frontal cortex, while simpler tasks rely more on bottom-up control mediated by posterior cortices.

The time course of attentional disengagement from angry faces in social anxiety

While impaired attentional disengagement from threatening stimuli is thought to enhance social anxiety, it is unclear when the impaired disengagement occurs accurately. We used a gap task (Experiment 1) and an overlap task (Experiment 2) to reveal the impaired attentional disengagement from angry faces in socially anxious people with non-treatment seeking undergraduates. High (N = 17 in Experiments 1 and 2) and low socially anxious people (N = 17 in Experiment 1 and 19 in Experiment 2) were asked to fixate on an angry or neutral face presented at the center of a screen. Then, they discriminated the peripheral target stimuli. When there was a temporal gap between the face and target in Experiment 1 (gap task), the reaction times (RTs) for angry and neutral faces did not differ for all participants. However, when there was no gap and the face continued to appear in Experiment 2 (overlap task), the RTs for angry faces in high socially anxious people were longer than those for neutral faces after presentation times of 300 ms or longer. In low socially anxious people, the RTs following the angry and neutral faces did not differ. These results suggest that high socially anxious people face difficulty in disengaging attention from angry faces after recognizing them.

Preattentional processes and disorganization in schizophrenia: Influence of a 6-week risperidone treatment

INTRODUCTION

Visual orientation and attention are impaired in schizophrenia. Engagement and disengagement of attention and the ability to prompt responses to a stimulus in patients before and after six weeks of risperidone were compared to controls.

METHODS

Ten unmedicated (nine naïve) schizophrenic patients, and eleven controls performed 1) A visual orienting task, the Cued Target Detection task (CTD), with the detection of a visual stimulus in valid, invalid, no cue and double cue trials, two conditions for fixation offset for a modulation of visual fixation: Gap: 200 ms before target; No Gap: simultaneous with target, 2) Choice Reaction Time (CRT 0.5 and 2 s delays).

RESULTS

At baseline, patients showed longer RT than controls in CRT, but not in CTD, with in CTD, no facilitation of RT with the gap procedure. The alertness index was almost null in CTD-Gap and comparable to controls in CTD-No Gap. Efficiency to detect attended stimuli (CTD-No Gap) and warning effect (CRT 0.5 s) were negatively correlated to disorganization. After treatment, readiness to act in CRT had decreased. In CTD-No Gap, change in PANSS disorganization was correlated to an increased validity index, change in negative sub-score was correlated to decreased attention cost.

CONCLUSION

Untreated patients displayed a deficit of Gap effect and a slowing in sustained attention. Disorganization interfered with warning and visual detection. After treatment, its improvement and negative symptoms improvement were associated with better visual detection. These alterations in visual orienting provide new evidence for an oculomotor dysregulation of attentional engagement in schizophrenia.

Attention and visual orienting in siblings, schizophrenic patients, and controls: impairment in attentional disengagement

Visual orienting tasks reveal an impaired disengagement of attention in schizophrenia. We explored visual orientation in 20 schizophrenia patients (SZ), 20 full siblings (FS), and 20 controls (C) using a cued target detection (gap vs. no gap) and a choice reaction time task. SZ but not FS had longer reaction time with comparable reactions to warning. In contrast to C, SZ and FS did not display a significant gap effect. The disengagement deficit in schizophrenia patients and their siblings provides arguments for altered early attention mechanisms (in schizophrenic patients and their nonpsychotic relatives).

Specific pattern of attentional changes in impulsive individuals

INTRODUCTION

Although impulsivity is recognised as a major psychopathological feature, its cognitive correlates remain controversial. We evaluated readiness to act induced by a warning signal and attentional engagement in healthy impulsive participants.

METHODS

People with high impulsivity scores (HI) and low impulsivity (LI) scores on Barratt's Impulsivity Scale (BIS) were selected among 1250 students from top and bottom deciles. Subjects with personal or family of lifetime Axis I disorders were excluded. Motor preparation was evaluated by a Choice Reaction Time task (CRT) with a randomly presented warning signal with a delay before target of 500 ms or 2000 ms depending on the trial block. Attentional engagement and maintenance of fixation was evaluated by a Cued Target Detection task (CTD) comparing cued (valid, invalid, or double cue) and uncued trials and contrasting fixation offset (gap) or maintenance (overlap) conditions.

RESULTS

HI, but not LI participants had a shortened reaction time in the 2000 ms condition of CRT with warning signal, indicating a persistent readiness to act. In contrast to LI, HI showed a decreased reinforcement of attention in the overlap condition of CTD with a hyperreactivity to all types of visual stimuli.

CONCLUSIONS

Impulsivity per se appears to be associated with hyperreactivity to warning or cue signals and on inability to maintain attentional fixity.

Effects of disorganization on choice reaction time and visual orientation in untreated schizophrenics

Several preattentive mechanisms have proved to be sensitive markers of clinical change in schizophrenia. Two related studies of visuospatial orientation used cued target detection combined with choice reaction time, short/long preparation, with or without a signal/target interval ("gap"/ "no-gap," to detect attentional disengagement difficulty in schizophrenia). End points were reaction times, alertness scores, attentional cost/benefit, and validity scores. Study 1, in 13 schizophrenics receiving second-generation antipsychotics and 13 controls, found the same impairment of disengagement as with neuroleptics, but intact reaction times and processing speed, with no hemispheric asymmetry. Study 2, in 12 untreated acute schizophrenics and 12 controls, showed slower reaction times, near-zero alertness in the fixation release condition, and impaired valid/invalid discrimination versus Syndrome Scale disorganization subscore (r = -0.81; P < 0.01). Early deficits in the preattentive orientation and visual. Early deficits in the preattentive orientation and visual detection phases are useful for assessing response to psychotropic treatment and establishing clinical correlates in acute schizophrenia.

Alternate response preparation in a visuomotor serial task

The preparation of a particular motor pattern is related to the information available that enables the actor to predict the correct response to a forthcoming stimulus. In many situations, however, prediction is not possible. In such cases, the individual can guess the probable parameters of the next stimulus. The authors attempted to establish the bias in the motor intention for movement and its interaction with a possible memory trace of the stimulus-response mapping produced by the preceding stimulus. Two letters were presented bilaterally, and participants (N=21) had to discriminate the target letter and respond with the compatible hand. The present findings support the existence of a memory trace of the previous stimulus-response mapping.