Emotional scene content drives the saccade generation system reflexively.

The authors assessed whether parafoveal perception of emotional content influences saccade programming. In Experiment 1, paired emotional and neutral scenes were presented to parafoveal vision. Participants performed voluntary saccades toward either of the scenes according to an imperative signal (color cue). Saccadic reaction times were faster when the cue pointed toward the emotional picture rather than toward the neutral picture. Experiment 2 replicated these findings with a reflexive saccade task, in which abrupt luminosity changes were used as exogenous saccade cues. In Experiment 3, participants performed vertical reflexive saccades that were orthogonal to the emotional–neutral picture locations. Saccade endpoints and trajectories deviated away from the visual field in which the emotional scenes were presented. Experiment 4 showed that computationally modeled visual saliency does not vary as a function of scene content and that inversion abolishes the rapid orienting toward the emotional scenes. Visual confounds cannot thus explain the results. The authors conclude that early saccade target selection and execution processes are automatically influenced by emotional picture content. This reveals processing of meaningful scene content prior to overt attention to the stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Relationship Between Inhibition of Return and Saccade Trajectory Deviations.

After presentation of a peripheral cue, a subsequent saccade to the cued location is delayed (inhibition of return: IOR). Furthermore, saccades typically deviate away from the cued location. The present study examined the relationship between these inhibitory effects. IOR and saccade trajectory deviations were found after central (endogenous) and peripheral (exogenous) cuing of attention, and both effects were larger with an onset cue than with a color singleton cue. However, a dissociation in time course was found between IOR and saccade trajectory deviations. Saccade trajectory deviations occurred at short delays between the cue and the saccade, but IOR was found at longer delays. A model is proposed in which IOR is caused by inhibition applied to a preoculomotor attentional map, whereas saccade trajectory deviations are caused by inhibition applied to the saccade map, in which the final stage of oculomotor programming takes place. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhanced facilitation of spatial attention in schizophrenia.

Objective: While attentional functions are usually found to be impaired in schizophrenia, a review of the literature on the orienting of spatial attention in schizophrenia suggested that voluntary attentional orienting in response to a valid cue might be paradoxically enhanced. We tested this hypothesis with orienting tasks involving the cued detection of a laterally presented target stimulus. Method: Subjects were chronic schizophrenia patients (SZ) and matched healthy control subjects (HC). In Experiment 1 (15 SZ, 16 HC), cues were endogenous (arrows) and could be valid (100% predictive) or neutral with respect to the subsequent target position. In Experiment 2 (16 SZ, 16 HC), subjects performed a standard orienting task with unpredictive exogenous cues (brightening of the target boxes). Results: In Experiment 1, SZ showed a larger attentional facilitation effect on reaction time than HC. In Experiment 2, no clear sign of enhanced attentional facilitation was found in SZ. Conclusions: The voluntary, facilitatory shifting of spatial attention may be relatively enhanced in individuals with schizophrenia in comparison to healthy individuals. This effect bears resemblance to other relative enhancements of information processing in schizophrenia such as saccade speed and semantic priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Saccade target selection and object recognition: evidence for a common attentional mechanism

The spatial interaction of visual attention and saccadic eye movements was investigated in a dual-task paradigm that required a target-directed saccade in combination with a letter discrimination task. Subjects had to saccade to locations within horizontal letter strings left and right of a central fixation cross. The performance in discriminating between the symbols "E" and "E", presented tachistoscopically before the saccade within the surrounding distractors was taken as a measure of visual attention. The data show that visual discrimination is best when discrimination stimulus and saccade target refer to the same object; discrimination at neighboring items is close to chance level. Also, it is not possible, in spite of prior knowledge of discrimination target position, to direct attention to the discrimination target while saccading to a spatially close saccade target. The data strongly argue for an obligatory and selective coupling of saccade programming and visual attention to one common target object. The results favor a model in which a single attentional mechanism selects objects for perceptual processing and recognition, and also provides the information necessary for motor action.     

Dual-task crosstalk between saccades and manual responses.

Between-task crosstalk has been discussed as an important source for dual-task costs. In this study, the authors examine concurrently performed saccades and manual responses as a means of studying the role of response-code conflict between 2 tasks. In Experiment 1, participants responded to an imperative auditory stimulus with a left or a right key press (manual task), a left or a right saccade (saccade task), or both. In Experiments 2 and 3, participants crossed their hands, and a modest (Experiment 2) or substantial (Experiment 3) degree of between-task response-code conflict through specific instructions was introduced. In Experiment 4, response codes across tasks were compatible, and stimulus–response mappings in both tasks were incompatible. Overall, the results indicate that performance not only in manual responses but also in saccades suffers from dual-task conditions, even though saccades were typically performed first and are usually assumed to be controlled quite independently. Moreover, the systematic introduction of response-code conflict between tasks modulated the pattern of dual-task performance. The authors propose confusability of response codes as an underlying mechanism of the observed effects of between-task crosstalk. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Saccade preparation inhibits reorienting to recently attended locations.

We measured manual reaction time in normal human Ss to confirm that an eccentric visual signal has a biphasic effect on covert attention and eye movements. First, it summons attention and biases a saccade toward the signal; a subsequent inhibition of return then slows responses to signals at that location. A temporal hemifield dominance for inhibition of return was shown; this finding coverges with observations (M. I. Posner et al; see record 1986-22316-001) in neurologic patients to suggest that it is mediated by midbrain pathways. Endogenous orienting of attention, from a central arrow cue, did not activate inhibition of return, whereas endogenous saccade preparation did so as effectively as an exogenous signal, even when no saccade was made. Inhibition of return is activated by midbrain oculomotor pathways and may function as a location "tagging" mechanism to optimize efficiency of visual search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early, Involuntary Top-Down Guidance of Attention From Working Memory.

Four experiments explored the interrelations between working memory, attention, and eye movements. Observers had to identify a tilted line amongst vertical distractors. Each line was surrounded by a colored shape that could be precued by a matching item held in memory. Relative to a neutral baseline, in which no shapes matched the memory item, search was more efficient when the memory cue matched the shape containing the target, and it was less efficient when the cued stimulus contained a distractor. Cuing affected the shortest reaction times and the first saccade in search. The effect occurred even when the memory cue was always invalid but not when the cue did not have to be held in memory. There was also no evidence for priming effects between consecutive trials. The results suggest that there can be early, involuntary top-down directing of attention to a stimulus matching the contents of working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory inefficiency and failures of intention activation: Age-related decline in the control of saccadic eye movements.

Young and older adults' control of saccadic eye movements was compared using an antisaccade task, which requires the inhibition of a reflexive saccade toward a peripheral onset cue followed by an intentional saccade in the opposite direction. In 2 experiments, an age-related decline was found in the suppression of reflexive eye movements, as indicated by an increased proportion of saccades toward the cue, and a longer time needed to initiate correct antisaccades. The results from Experiment 2 suggested that older adults' slower antisaccades may be explained partly in terms of increased failures to maintain the cue-action representation at a sufficient activation level. The results suggest that the notion of selective preservation with age of the ability to inhibit spatial responses does not apply to the active inhibition of prepotent spatial responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus–target compatibility for reaching movements.

Reaction time, movement time, and initial direction of reaching movements toward a target in left or right hemispace were measured. In Experiment 1, the target of movement and hand had to be selected; movements toward the imperative stimulus were initiated faster than movements toward the alternate target, and ipsilateral reaches were initiated faster than contralateral reaches. In Experiment 2, the difference between ipsilateral and contralateral reaches disappeared when no selection of the hand had to occur. In Experiment 3, no target had to be selected, and only a stimulus-hand compatibility effect appeared. The results reveal different compatibility effects (stimulus-target, stimulus-hand, target-hand), implying that participants exploit different correspondences, depending on the degrees of freedom of the action. The notion of compatibility effects relating to movement targets offers a new perspective on the negative Simon effect and it questions the general concept of response codes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of the gap paradigm on the latency of human smooth pursuit of eye movement

When a temporal gap is introduced between the extinction of a central fixation target and the illumination of an eccentric target (the gap paradigm), normal human subjects initiate saccadic eye movements towards the eccentric target at lower latency than when there is no gap. The aim of this study was to examine the latency of human smooth pursuit eye movements using a modified gap paradigm. Smooth pursuit latency was reduced in gap tasks, and the magnitude of reduction was related to the duration of the gap. The distribution of smooth pursuit latencies was also altered. It thus appears that human smooth pursuit latency is modulated in a similar manner to saccade latency in gap tasks.     

Interactive Activation in Visual Word Recognition: Constraints Imposed by the Joint Effects of Spatial Attention and Semantics.

Two lexical-decision experiments investigated the effects of semantic priming and stimulus intensity when target location varied and was cued by an abrupt onset. In Experiment 1, the spatial cue was a good predictor of target location, and in Experiment 2 it was not. The results indicate that word recognition processes were postponed until spatial attention was focused on the target and that whether attention further affected word recognition depended on cue validity. The joint effects of cue validity and priming interacted when cue validity was high but were additive when cue validity was low. The joint effects of stimulus intensity and semantic priming also varied according to cue validity (i.e., interactive when high and additive when low). The results are discussed in terms of their implications for visual word recognition, the distinction between exogenous and endogenous spatial attention, and how attention is affected by visual word recognition processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Switching in the cocktail party: Exploring intentional control of auditory selective attention.

Using a novel variant of dichotic selective listening, we examined the control of auditory selective attention. In our task, subjects had to respond selectively to one of two simultaneously presented auditory stimuli (number words), always spoken by a female and a male speaker, by performing a numerical size categorization. The gender of the task-relevant speaker could change, as indicated by a visual cue prior to auditory stimulus onset. Three experiments show clear performance costs with instructed attention switches. Experiment 2 varied the cuing interval to examine advance preparation for an attention switch. Experiment 3 additionally isolated auditory switch costs from visual cue priming by using two cues for each gender, so that gender repetition could be indicated by a changed cue. Experiment 2 showed that switch costs decreased with prolonged cuing intervals, but Experiment 3 revealed that preparation did not affect auditory switch costs but only visual cue priming. Moreover, incongruent numerical categories in competing auditory stimuli produced interference and substantially increased error rates, suggesting continued processing of task-relevant information that often leads to responding to the incorrect auditory source. Together, the data show clear limitations in advance preparation of auditory attention switches and suggest a considerable degree of inertia in intentional control of auditory selection criteria. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Nucleotide sequences and functional characterization of two tobacco UAG suppressor tRNA(Gln) isoacceptors and their genes

The hypothesis was tested that peak velocity of saccadic eye movements in visual motor tasks varies with variables related to energy regulation. The hypothesis is based on the cognitive-energetical performance model of Sanders. An experimental paradigm was developed in which saccadic peak velocity of task-relevant eye movements is measured while a choice reaction task is carried out. Confounding factors of saccadic amplitude and movement direction were controlled. The task was designed in such a way that in each trial subjects performed a target saccade towards an imperative stimulus and a return saccade after the manual response back to the centre of the screen. For both types of saccades the experimental variables were foreperiod duration (short versus long), knowledge of results (with versus without), postsaccadic demand (low versus high) and time on task (five 30-min intervals). In two experiments, there are main and interaction effects of the task variables on peak saccadic velocity. Return saccades are slower than target saccades, but not in the case of high postsaccadic demand. Knowledge of results increases peak saccadic velocity, but more so for return than for target saccades. Time on task leads to a decrease in peak saccadic velocity, which is much stronger for return than for target saccades; furthermore this effect is more pronounced after short than after long foreperiods. Peak saccadic velocity is changed within seconds. The results support the hypothesis. Peak saccadic velocity of task related eye movements reflects energy regulation during task performance. The paradigm will be developed as a diagnostic tool in workload measurement.     

Bilateral interactions in saccade programming. A saccade-latency study

Subjects were required to make a saccade to a target appearing randomly 4 degree to the left or right of the current fixation position (1280 trials per experiment). Location cues were used to direct visual attention and start saccade preparation to one of the two locations before target onset. When the cue indicated the target location (valid trials), the generation of express saccades (visually guided saccades with latencies around 100 ms) was strongly facilitated. When the opposite location was cued (invalid trials), express saccades were abolished and replaced by a population of mainly fast-regular saccades (latencies around 150 ms). This was found with a peripheral cue independently of whether the fixation point was removed before target onset (gap condition; experiment 1) or remained on throughout the trial (overlap condition; experiment 2). The same pattern also was observed with a central cue that did not involve any visual stimulation at a peripheral location (experiment 3). In the case where the primary saccade was executed in response to the cue and the target appeared at the opposite location, continuous amplitude transition functions were observed: starting at about 60-70 ms from target onset onward, the amplitude of the cue-elicited saccades continuously decreased from 4 degree to values below 1 degree. The results are explained by a fixation-gating model, according to which the antagonism between fixation and saccade activity gives rise to multimodal distributions of saccade latencies. It is argued that allocation of visual attention and saccade preparation to one location entails a successive disengagement of the fixation system controlling saccade preparation within the hemifield to which the saccade is prepared and a partial engagement of the opposite fixation system.     

Spatial patterns in the control of human arm movement

Generalized Procrustes analysis was used to investigate the spatial paths of pointing movements. In Experiment 1, 3 participants produced similar spatial paths of the hand when repeating a pointing movement many times, despite variability in the position and orientation of the movements. The average spatial path indicates a fundamental spatial pattern of the motor system, or motor primitive. This pattern varied across the workspace. Anterioposterior movements were straight, but repeated movements had variable spatial patterns. Lateral movements were curved away from the body but had regular spatial patterns. Experiment 2 extended these results to movements of different amplitudes in 7 participants. The motor primitive seems to be abandoned at the end of the movement in favor of final adjustments to bring the hand to the target position. In Experiment 3, the same participants produced similar motor primitives both with and without vision.     

Eye-hand interactions during goal-directed pointing movements

Saccadic eye and hand movements made to step displacements in target position were measured under conditions designed to dissociate the output of the ocular and manual motor systems. This was accomplished by having subjects look and point, either with or without vision of the hand (closed or open loop, respectively) at peripheral targets starting from independent initial positions. The results showed that the amplitude of open loop pointing responses increased in size when accompanied by saccades that were larger than the required hand movement. Providing the subject with visual feedback of the hand during the response or asking them to visually fixate caused this effect to disappear. Taken together, this pattern of results suggests that when vision of the hand is unavailable the programming of saccade metrics influences the control of simultaneously produced pointing movements in an on-line manner.     

Protection from latent inhibition provided by a conditioned inhibitor.

Two conditioned suppression experiments with rats investigated the influence on latent inhibition of compounding a Pavlovian conditioned inhibitor with the target cue during preexposure treatment. Results were compared with those of subjects that received conventional latent inhibition training, no preexposure, or preexposure to the target cue in compound with a neutral stimulus. In Experiment 1, greater attenuation of the latent inhibition effect was observed in subjects that received target preexposure in compound with a Pavlovian conditioned inhibitor relative to subjects that received preexposure with a neutral stimulus or to the target alone. In Experiment 2, this protection from latent inhibition was attenuated if the excitor that was used to train the conditioned inhibitor was extinguished between preexposure and target training. The results are consistent with an account offered by the extended comparator hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Can monkeys (Macaca mulatta) represent invisible displacement?

Four experiments were conducted to assess whether or not rhesus macaques (Macaca mulatta) could represent the unperceived movements of a stimulus. Subjects were tested on 2 computerized tasks, HOLE (monkeys) and LASER (humans and monkeys), in which subjects needed to chase or shoot at, respectively, a moving target that either remained visible or became invisible for a portion of its path of movement. Response patterns were analyzed and compared between target-visible and target-invisible conditions. Results of Experiments 1, 2, and 3 demonstrated that the monkeys are capable of extrapolating movement. That this extrapolation involved internal representation of the target's invisible movement was suggested but not confirmed. Experiment 4, however, demonstrated that the monkeys are capable of representing the invisible displacements of a stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Presaccadic attention allocation and express saccades

Express saccades are visually-guided saccades that are characterized by an extremely short latency of about 100 ms. The present experiments tested the hypothesis that a disengagement of visual attention is necessary for the generation of express saccades. All subjects produced large numbers of express saccades in the gap paradigm, in which the fixation stimulus is removed 200 ms before target onset (Exp. 1), but not in the overlap paradigm, in which the fixation stimulus remained on during the entire trial (Exp. 2). By means of peripheral cues (Exps. 3-5) and central cues (Exps. 6-7), visual attention was directed at the target location for the saccade before the actual appearance of the saccade target. In all experiments, the location cues facilitated rather than abolished express saccades. The generation of express saccades was facilitated even when the currently fixated visual stimulus was not removed before target onset (fixation-overlap; Exps. 5-7). The results are explained by the hypothesis that a disengagement of a separate fixation system is necessary for the generation of express saccades, a hypothesis that is in line with current neurobiological findings.     

Attentional orienting within visual field in a lexical decision task.

The influence of spatial attention on lexical decisions to lateralized target letter-strings appearing either along with a distractor (Experiment 1) or in an otherwise empty field (Experiments 2–6) was examined. Attentional orienting was controlled by peripheral (Experiments 1, 2, 3, and 6) and central (Experiments 4–5) cuing methods. Manipulations of spatial attention, including cue validity and cue–target stimulus onset asynchrony, were combined with manipulations of word frequency in Experiments 3-6. All the attentional manipulations were effective, but they did not modify the right visual field advantage in word performance, In addition, the attentional effects did not interact with either the presence or absence of distractors or with stimulus familiarity. Implications of these results regarding the influence of spatial attention (the posterior attention system) on word processing are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)