Age-related differences in object- and location-based inhibition of return of attention.

Four experiments examined age-related differences in inhibition of return (IOR) of visual attention. Using static stimuli, both young and older adults were slower to detect targets in previously cued objects, showing equivalent IOR. With objects that moved after they had been cued, young adults were slower to detect targets in the cued object (compared with uncued ones), revealing object-based IOR, but older adults were faster to detect targets in such objects, failing to demonstrate object-based IOR. Both age groups were slower to detect targets at the initially cued location (location-based IOR). The results show that age has a differential effect on IOR depending on the frame of reference of the inhibition: Inhibition for objects breaks down with age, but that for location does not. This pattern of results is consistent with the view that there are specific inhibitory deficits in old age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficits and recovery of first- and second-order motion perception in patients with unilateral cortical lesions

Unilateral lesions in the posterior parietal cortex can degrade motion perception in the contralesional visual hemifield. Our aim was to investigate whether deficits caused by cortical lesions may be different for first- and second-order motion perception, and to study the time scale of any potential recovery. In nine patients with circumscribed lesions mainly in the parietal and fronto-parietal cortex, thresholds for direction discrimination were measured for stimuli presented peripherally in their ipsi- and contralesional hemifield. Subjects had to identify the direction of a vertically moving object embedded in a background of dynamic random dot noise. The object consisted of various proportions of signal and noise dots. Signal dots were either (a) coherently moving in the same direction as the object (first-order), (b) stationary (second-order: drift-balanced), or (c) coherently moving in the opposite direction (second-order: theta). Noise dots were flickering. Two patients showed significant threshold elevations for all three types of motion stimuli presented in their contralesional hemifield, while thresholds for ipsilesional targets were unaffected. Neither showed any selective deficit of first- versus second-order motion perception, but second-order motion was more impaired. Their lesions probably included the motion area V5-MT, which was spared in the other seven patients. One of the patients, who was retested several times during a 27-month postlesional period, showed complete recovery for first- and second-order motion direction discrimination, as well as for the detection of speed differences.     

Object-based inhibition of return in patients with posterior parietal damage.

Recent evidence has shown that inhibition of return, IOR, is impaired in patients with parietal damage with or without clinical signs of neglect (Bartolomeo, Sieroff, Decaix, & Chokron, 2001; Vivas, Humphreys, & Fuentes, 2003, respectively). In addition to environment-based IOR, Tipper et al. (1991) showed that IOR could be also associated with dynamic, object-based representations. In our study, we examined four patients with unilateral lesions to the parietal lobe, and a group of healthy controls, in an IOR procedure with moving objects where a pre-cued object could move, clockwise or counterclockwise, 90° in polar coordinates. The group of control participants showed a small but significant object-based IOR effect. In contrast, the patients showed an object-based IOR effect when the objects moved from the contralesional field toward the ipsilesional field, whereas there was no IOR effect when they moved from the ipsilesional to the contralesional field. These findings are discussed in terms of the role of the parietal cortex in implementing attentional biases in both environment-based (Vivas et al., 2003) and object-based frames of reference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial attention and cuing to global and local levels of hierarchical structure.

Five experiments investigated the role of attention in identifying global and local targets in hierarchically structured patterns. Hierarchical patterns were presented at a variable stimulus onset asynchrony (SOA) either after a cue (4 arrows or shaded boxes) or after no cue. Targets occurred at the cued level 80% of the time and at the uncued level 20%. On uncued trials, target level probability was .5. Global cues produced benefits for both global and local targets over SOA on cued trials. Local cues produced benefits only for local targets. For uncued trials, responses favored local targets overall when interspersed with locally cued trials but favored global targets when interspersed with globally cued trials. The role of an attentional window and discrete distribution of attention over global and local levels of hierarchical patterns are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Passover and plague

Patients with unilateral neglect following right hemisphere damage may have difficulty in moving towards contralesional targets. To test the hypothesis that this impairment arises from competing motor programs triggered by irrelevant ipsilesional stimuli, we examined 16 right hemisphere patients, eight with left visual neglect and eight without, in addition to eight healthy control subjects. In experiment 1 subjects performed sequences of movements using their right hand to targets on the contralesional or ipsilesional side of the responding limb. The locations of successive targets in each sequence were either predictable or unpredictable. In separate blocks of trials, targets appeared either alone or with a simultaneous distractor located at the immediately preceding target location. Neglect patients were significantly slower to execute movements to contralesional targets, but only for unpredictable movements and in the presence of a concurrent ipsilesional distractor. In contrast, healthy controls and right hemisphere patients without neglect showed no directional asymmetries of movement execution. In experiment 2 subjects were required to interrupt a predictable, reciprocating sequence of leftward and rightward movements in order to move to an occasional, unpredictable target that occurred either in the direction opposite to that expected, or in the same direction but twice the extent. Neglect patients were significantly slower in reprogramming the direction and extent of movements towards contralesional versus ipsilesional targets, and they also made significantly more errors when executing such movements. Right hemisphere patients without neglect showed a similar bias in reprogramming direction (but not extent) for contralesional targets, whereas healthy controls showed no directional asymmetry in either condition. On the basis of these findings we propose that neglect involves a competitive bias in favour of motor programs for actions directed towards ipsilesional versus contralesional events. We suggest that programming errors and increased latencies for contralesional movements arise because the damaged right hemisphere can no longer effectively inhibit the release of inappropriate motor programs towards ipsilesional events.     

Object- and location-based inhibition of return in younger and older adults.

When a cued object moves to new spatial coordinates, inhibition of return (IOR) with younger adults is found at the original cued location (location-based IOR) and at the current location of the object (object-based IOR). Older adults, however, show only location-based IOR. To determine whether this pattern of results represents a general age-related deficit in object-based IOR, the authors used static displays in which the placeholders (i.e., objects) were either present (location-based IOR + object-based IOR) or absent (location-based IOR only). Both age groups showed location-based IOR, but the older adults failed to show object-based IOR, consistent with age-related differences in visual pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object-based attentional selection and aging.

The authors conducted 2 studies which examined potential age-related differences in object-based attentional selection. Participants were briefly presented with pairs of wrenches and were asked to make 1 response if both target properties (i.e., an open end and a hexagonal end) were present and another response if only a single target property was present in the display. The critical manipulation was whether the target properties were present on 1 wrench or distributed between 2 wrenches. Space-based models of selective attention predict no difference in performance between these conditions. However, object-based attentional selection models predict better performance when both target properties appear on a single object. The results from both of the studies were consistent with object-based models of attentional selection. Furthermore, both young and old adults showed similar performance effects, suggesting the object-based attentional selection is insensitive to normal aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of Return to an Occluded Object Depends on Expectation.

Inhibition of return (IOR) is indexed by slower reaction times to targets presented at previously attended locations or objects. If a moving object is occluded, some studies find IOR, others do not. Four experiments examined whether this inconsistency hinges on the observer's expectation as to whether the object continues to exist at the end of its motion sequence. Results showed that observer expectation is a powerful determining factor: IOR occurs only if the observer expects the object to continue to exist. In contrast, if the object is not occluded, IOR occurs only if the object remains on view immediately before the target is presented. It was concluded that 2 factors, object continuity and observer expectation, mediate both location- and object-based IOR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mixed reference frames for dynamic inhibition of return.

Reference frames mediating inhibition of return (IOR) in dynamic displays were investigated by comparing the effects of a cue in simple versus extended objects. Experiment 1 replicated S. P. Tipper, B. Weaver, L. M. Jerreat, and A. L. Burak's (1994) finding of location- and object-based IOR for boxes rotating about fixation. In Experiments 2 and 3, the boxes were replaced by two boomerang-shaped objects. Response times were slowed to all target locations across a cued object. They were also slowed to locations vacated by the uncued region of the cued object-evidence for a representation the authors call the "perceptual footprint." Whereas an object served as the medium for location-based IOR for B. S. Gibson and H. Egeth (1994), the environment served as the medium for object- and location-based IOR in Experiments 2 and 3. This suggests that (a) frames of reference may be considered hierarchically and (b) nesting of frames is context dependent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired orienting of attention in left unilateral neglect: A componential analysis.

Twenty-six patients suffering from damage to the right side of the brain, 19 of whom exhibited signs of left neglect, as well as 32 matched controls, ran 3 spatial cuing tasks. Patients were also tested with 2 cancellation tests, a line-bisection test, the copy of a complex drawing, and a visual extinction procedure. Results first showed correlations between extinction and cancellation tests performance on one hand, and between line bisection and copy on the other hand. Second, results demonstrated that an engagement deficit toward contralesional targets appeared to be the most striking feature of neglect, and the engagement score was correlated with the cancellation score and extinction. Most patients with neglect also presented a deficit in disengagement, a deficit of inhibition of return, and probably a deficit of alertness. Deficits in engagement and in disengagement, as well as poor scores in cancellation tests, seemed to be related with posterior cortical and subcortical lesions. Most important, even if an endogenous deficit (frequently related with a thalamic lesion) could aggravate the neglect behavior, neglect syndrome was mainly explained by a deficit of exogenous attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Limitations of object-based feature encoding in visual short-term memory.

The present study investigated object-based feature encoding in visual short-term memory for 2 features within the same dimension that occur on different parts of an object. Using the change-detection paradigm, this experiment studied objects with 2 colors and objects with 2 orientations. Participants found it easier to monitor 1 rather than both features of such objects, even when decision noise was properly controlled for. However, no object-based benefit was observed for encoding the 2 features of each object that were of the same dimension. When similar stimuli were used but the 2 features of each object were from different dimensions (color and orientation), an object-based benefit was observed. These results thus impose a major constraint on object-based feature encoding theories by showing that only features from different dimensions can benefit from object-based encoding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory for duration: role of hippocampus and medial prefrontal cortex

In this task rats had to learn that a three-dimensional object stimulus (a rectangle) that was visible for 2 s would result in a positive (go) reinforcement for one object (a ball) and no reinforcement (no go) for a different object (a bottle). However, if the rectangle stimulus was visible for 8 s then there would be no reinforcement for the ball (no go), but a reinforcement for the bottle (go). After rats learned this conditional discrimination by responding differentially in terms of latency to approach the object, they received large (dorsal and ventral) lesions of the hippocampus, lesions of the medial prefrontal cortex (anterior cingulate and precentral cortex), lesions of the cortex dorsal to the dorsal hippocampus, or served as sham-operated controls. Following recovery from surgery they were retested. The results indicate that there were major impairments following hippocampal lesions, in contrast to cortical control and medial prefrontal cortex lesions, as indicated by smaller latency differences between positive and negative trials on postsurgery tests. In order to ensure that the deficits observed with hippocampal lesions were not due to a discrimination problem, new rats were trained in an object (gray cylinder) duration discrimination task. In this go/no go procedure, the rats were reinforced for a 2-s exposure (duration) of the gray cylinder, but not a 10-s duration, or vice versa. The results indicate that after hippocampal lesions, there was an initial deficit followed by complete recovery. There were no significant changes for the medial prefrontal, cortical control, or sham-operated animals. It appears that the hippocampus, but not the medial prefrontal cortex, is actively involved in representing in short-term memory temporal attribute information based on the use of markers for the beginning and end of the presence (duration) of a stimulus (object).     

Is object-based attention mandatory? Strategic control over mode of attention.

Is object-based attention mandatory or under strategic control? In an adapted spatial cuing paradigm, participants focused initially on a central arrow cue that was part of a perceptual group (Experiment 1) or a uniformly connected object (Experiment 2), encompassing one of the potential target locations. The cue always pointed to an opposite, different-object location. By varying cue validity, the strategic incentive to prevent the spread of attention to the entire cue object, and consequently to the same-object location, was manipulated: With invalid cuing and (consequently) equal probability of targets at same-object and different-object locations, a same-object target identification advantage was observed. With highly valid cuing and targets much more probable at the different-object location than at the same-object location, the same-object advantage disappeared. Object-based attention appears to be a default mode that may be ecologically adaptive but can be overridden by strategic control when there is a strong immediate benefit in doing so. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shifts of visual attention to multiple simultaneous location cues.

Conducted 2 experiments to examine the effects of adjacent double cueing on target identification response times (Exp 1) and to determine whether similar results would be obtained with nonadjacent double cueing (Exp 2). For 14 observers, single and simultaneous multiple location cues were presented a brief period of time before the onset of targets that they were required to identify. Single and multiple cueing effects were similar, even when targets were presented at locations "in between" pairs of cues. The increase in response times that occurred when a target was presented at uncued locations in between a pair of cued locations suggests that pairs of cued locations are encoded independently by an operation called spatial indexing. A multiple indexing proposal and its role in mediating visual attention shifts initiated by direct cueing is described. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Goal-directed selective attention and response competition monitoring: Evidence from unilateral parietal and anterior cingulate lesions.

Competing visual stimuli lead to slower responses to targets. This response competition must be resolved before correct responses are executed. Neuroimaging suggests that response competition monitoring may be subserved by an integrated neural network including the anterior cingulate cortex (ACC). In this study, 1 patient with a parietal lesion (Patient J.S.) and 1 with an ACC lesion (Patient G.M.) were presented with 2 flanker tasks; 1 required verbal identification of color targets, and the other required an opposite response to targets (e.g., see red and say "green"); a control group was also tested. For controls, perceptually incongruent flankers interfered with the ability to inhibit prepotent responses to targets. Patient J.S. performed in a similar manner, even when flankers appeared in the neglected field. Patient G.M. demonstrated reduced interference effects for contralesional flankers. Results are discussed in terms of goal-directed selective attention and response competition monitoring. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective attention and performance with a multidimensional visual display.

Studied selective attention, using data from 63 adult Ss collected in 4 experiments in which stimuli varied in both spatial location and visual form. In Exp I, the likely location and likely form of targets were both precued. An advantage was found for cued over uncued forms at both cued and uncued locations. In Exps II, III, and IV, different forms tended to occur at different locations. Regardless of whether a location was cued or uncued, form selective effects were found in accordance with form probability for that location. It was not the case that selective attention simply favored certain locations or certain stimulus forms in preference to others. Rather, selective attention was sensitive to precise combinations of form and location. It is concluded that these results can not be reconciled with mental spotlight notions of spatial selectivity. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The time to detect targets at inhibited and noninhibited locations: Preliminary evidence for attentional momentum.

Inhibition of return refers to the finding that response latencies are longer for targets appearing at previously attended (cued) locations than at novel (uncued) locations. The present research was designed to examine the pattern of detection latencies that occurred for targets appearing at various uncued locations. The first 2 experiments showed that responses were fastest when the target occurred at a location directly opposite the cue. Experiment 3 showed that latencies were related to the angle between the target and the direction in which attention was being oriented. Experiments 4 and 5 showed that manipulating the direction of attentional orientation affected inhibition of return. Overall, the results suggest that inhibition of return may be due to the difference between orienting attention to locations along the path of attention versus orienting attention to those off the path of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual attention and objects: Evidence for hierarchical coding of location.

In 5 experiments, it was found that judging the relative location of 2 contours was more difficult when they belonged to 2 objects rather than 1. This was observed even when the 1- and 2-object displays were physically identical, with perceptual set determining how many objects they were seen to contain. Such a 2-object cost is consistent with object-based views of attention and with a hierarchical scheme for position coding, whereby object parts are located relative to the position of their parent object. In further experiments, it was shown that in accord with this hierarchical scheme, the relative location of objects could disrupt judgments of the relative location of object parts, but the reverse did not occur. This was found even when the relative position of the parts could be judged more quickly than that of the objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correspondence effects for objects with opposing left and right protrusions.

Choice reactions to a property of an object stimulus are often faster when the location of a graspable part of the object corresponds with the location of a keypress response than when it does not, a phenomenon called the object-based Simon effect. Experiments 1–3 examined this effect for variants of teapot stimuli that were oriented to the left or right. Whether keypress responses were made with fingers within the same hand or between different hands was also manipulated. Experiment 1 showed that, for judgments of stimulus color and upright-inverted orientation, the Simon effect for intact teapots occurred in the direction of the spout location and was larger for within- than between-hand response modes. In Experiments 2 and 3, teapots with the handle or spout removed showed separate contributions of each component to the Simon effect. In Experiment 4, we clarified a discrepancy between our findings of object-based Simon effects and a previously reported absence of effect with color judgments for door-handle stimuli. We obtained an object-based Simon effect with respect to handle position when the bases of the door handles were centered but not when the handles were centered. The findings that object-based Simon effects occur with color judgments and when responses are fingers on the same hand are in closer agreement with a location coding account than with a grasping affordance account. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The development of perceptual completion abilities: infants' perception of stationary, partially occluded objects

We explored infants' ability to perceive stationary, partially occluded objects as connected units (Experiments 1 and 2) with specific appearances (Experiment 3). In each experiment, the infants saw 2 test events involving what appeared to adults to be a tall rectangular object whose middle portion was hidden behind a narrow screen. During the test events, the screen alternately uncovered and covered the object. In Experiments 1 and 2, removal of the screen revealed either a single, connected rectangle (complete object event) or an interrupted rectangle with a gap where the screen had been (broken object event). In Experiment 3, removal of the screen revealed either a rectangle (rectangle event) or a cross-shaped object (cross-shape event). The pattern of infants' looking times at these events suggest that they perceive the unity of the partially occluded object by 6.5 months of age but did not perceive the form of the hidden part of the object until 8 months. The results of baseline control conditions support this interpretation.