Luminance and spatial attention effects on early visual processing

Event-related potentials (ERPs) were recorded from healthy subjects in response to unilaterally flashed high and low luminance bar stimuli presented randomly to left and right field locations. Their task was to covertly and selectively attend to either the left or right stimulus locations (separate blocks) in order to detect infrequent shorter target bars of either luminance. Independent of attention, higher stimulus luminance resulted in higher ERP amplitudes for the posterior N95 (80-110 ms), occipital P1 (110-140 ms), and parietal N1 (130-180 ms). Brighter stimuli also resulted in shorter peak latency for the occipital N1 component (135-220 ms); this effect was not observed for the N1 components over parietal, central or frontal regions. Significant attention-related amplitude modulations were obtained for the occipital P1, occipital, parietal and central N1, the occipital and parietal P2, and the parietal N2 components; these components were larger to stimuli at the attended location. In contrast to the relatively short latencies of both spatial attention and luminance effects, the first interaction between luminance and spatial attention effects was observed for the P3 component to the target stimuli (350-750 ms). This suggests that interactions of spatial attention and stimulus luminance previously reported for reaction time measures may not reflect the earliest stages of sensory/perceptual processing. Differences in the way in which luminance and attention affected the occipital P1, occipital N1 and parietal N1 components suggest dissociations among these ERPs in the mechanisms of visual and attentional processing they reflect.(ABSTRACT TRUNCATED AT 250 WORDS)     

ERP effects of intermodal attention and cross-modal links in spatial attention

The function of articular cartilage as a weight-bearing tissue depends on the specific arrangement of collagen types II and IX into a three-dimensional organized collagen network that can balance the swelling pressure of the proteoglycan/water gel. To determine whether cartilage engineered in vitro contains a functional collagen network, chondrocyte-polymer constructs were cultured for up to 6 weeks and analyzed with respect to the composition and ultrastructure of collagen by using biochemical and immunochemical methods and scanning electron microscopy. Total collagen content and the concentration of pyridinium crosslinks were significantly (57% and 70%, respectively) lower in tissue-engineered cartilage that in bovine calf articular cartilage. However, the fractions of collagen types II, IX, and X and the collagen network organization, density, and fibril diameter in engineered cartilage were not significantly different from those in natural articular cartilage. The implications of these findings for the field of tissue engineering are that differentiated chondrocytes are capable of forming a complex structure of collagen matrix in vitro, producing a tissue similar to natural articular cartilage on an ultrastructural scale.     

The retinotopy of visual spatial attention

We used high-field (3T) functional magnetic resonance imaging (fMRI) to label cortical activity due to visual spatial attention, relative to flattened cortical maps of the retinotopy and visual areas from the same human subjects. In the main task, the visual stimulus remained constant, but covert visual spatial attention was varied in both location and load. In each of the extrastriate retinotopic areas, we found MR increases at the representations of the attended target. Similar but smaller increases were found in V1. Decreased MR levels were found in the same cortical locations when attention was directed at retinotopically different locations. In and surrounding area MT+, MR increases were lateralized but not otherwise retinotopic. At the representation of eccentricities central to that of the attended targets, prominent MR decreases occurred during spatial attention.     

The effect of spatial attention on memory scanning.

Examined the influence of spatial attention on the retrieval of items from short term memory. 48 participants (aged 18–40 yrs) responded to probe letters after sets of 2, 4, and 6 letters were memorized (S. Sternberg, 1966, 1969). Spatial attention was controlled by central arrow cues and stimuli were presented in a clear or a visually degraded form. Overall RT was shorter for attended than for unattended locations, and shorter for clear than for degraded stimuli. Even though the function relating RT to memory-set size for stimuli in attended locations had a significantly smaller zero-intercept than the function for unattended locations, the slope was unchanged, which suggests that attention did not influence the memory-scanning stage. Visual quality interacted with attention, which suggests that they influenced the same stage of processing, presumably the early visual-encoding stage of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotional influences on spatial attention.

The relationships between the anterior-posterior and left-right regions of the brain have been characterized as mutually inhibitory. Whereas the left hemisphere attends to right proximal hemispace and is associated with positive emotions, the right hemisphere attends to left distal hemispace and is associated with negative emotions. Because of the excitatory and inhibitory influences between the left and right frontal and posterior regions of the brain, the expression of emotion will result in an ipsilateral attentional bias. Given these functional systems, we hypothesized that positive emotions would be associated with a bias for left distal hemispace and negative emotions would be associated with a bias for right proximal hemispace. We tested these hypotheses by having 138 undergraduate students place emotionally labeled pegs on a large board. Our results indicated that the positively labeled pegs were placed in left distal hemispace and the relative placement of negatively labeled pegs was rightward and proximally. Whereas numerous research investigations have examined how attention is biased for emotional stimuli, ours is the first investigation to provide evidence that emotions can bias attentional allocation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cross-modal links in spatial attention

A great deal is now known about the effects of spatial attention within individual sensory modalities, especially for vision and audition. However, there has been little previous study of possible cross-modal links in attention. Here, we review recent findings from our own experiments on this topic, which reveal extensive spatial links between the modalities. An irrelevant but salient event presented within touch, audition, or vision, can attract covert spatial attention in the other modalities (with the one exception that visual events do not attract auditory attention when saccades are prevented). By shifting receptors in one modality relative to another, the spatial coordinates of these cross-modal interactions can be examined. For instance, when a hand is placed in a new position, stimulation of it now draws visual attention to a correspondingly different location, although some aspects of attention do not spatially remap in this way. Cross-modal links are also evident in voluntary shifts of attention. When a person strongly expects a target in one modality (e.g. audition) to appear in a particular location, their judgements improve at that location not only for the expected modality but also for other modalities (e.g. vision), even if events in the latter modality are somewhat more likely elsewhere. Finally, some of our experiments suggest that information from different sensory modalities may be integrated preattentively, to produce the multimodal internal spatial representations in which attention can be directed. Such preattentive cross-modal integration can, in some cases, produce helpful illusions that increase the efficiency of selective attention in complex scenes.     

Figural aftereffects and spatial attention

Distracting attention away from the location of an adaptation figure reduces the positional shift of a displaced test figure in the figural aftereffect (FAE). Participants performed an alignment task after adaptation involving various manipulations of spatial attention. In 1 condition, participants counted how often numbers occurred in an alphanumeric sequence presented during adaptation. (The sequence also appeared in a comparison condition, but no attention was required.) The FAE was reduced when the alphanumeric sequence attended to was in the center of the display while the adaptation figure was 3 degrees eccentric but not when the pattern was superimposed on the adaptation figure. Forced attention to 1 feature of the adaptation figure, its orientation, did not reduce the FAE (Experiment 3). To obtain a maximum FAE, the span of attention must cover the adaptation figure.     

Graded effects of spatial and featural attention on human area MT and associated motion processing areas

Functional magnetic resonance imaging was used to quantify the effects of changes in spatial and featural attention on brain activity in the middle temporal visual area and associated motion processing regions (hMT+) of normal human subjects. When subjects performed a discrimination task that directed their spatial attention to a peripherally presented annulus and their featural attention to the speed of points in the annulus, activity in hMT+ was maximal. If subjects were instead asked to discriminate the color of points in the annulus, the magnitude and volume of activation in hMT+ fell to 64 and 35%, respectively, of the previously observed maximum response. In another experiment, subjects were asked to direct their spatial attention away from the annulus toward the fixation point to detect a subtle change in luminance. The response magnitude and volume dropped to 40 and 9% of maximum. These experiments demonstrate that both spatial and featural attention modulate hMT+ and that their effects can work in concert to modulate cortical activity. The high degree of modulation by attention suggests that an understanding of the stimulus-driven properties of visual cortex needs to be complemented with an investigation of the effects of task-related factors on visual processing.     

The influence of alertness on spatial and nonspatial components of visual attention.

Three experiments investigated whether spatial and nonspatial components of visual attention would be influenced by changes in (healthy, young) subjects’ level of alertness and whether such effects on separable components would occur independently of each other. The experiments used a no-cue/alerting-cue design with varying cue-target stimulus onset asynchronies in two different whole-report paradigms based on Bundesen’s (1990) theory of visual attention, which permits spatial and nonspatial components of selective attention to be assessed independently. The results revealed the level of alertness to affect both the spatial distribution of attentional weighting and processing speed, but not visual short-term memory capacity, with the effect on processing speed preceding that on the spatial distribution of attentional weighting. This pattern indicates that the level of alertness influences both spatial and nonspatial component mechanisms of visual attention and that these two effects develop independently of each other; moreover, it suggests that intrinsic and phasic alertness effects involve the same processing route, on which spatial and nonspatial mechanisms are mediated by independent processing systems that are activated, due to increased alertness, in temporal succession. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of spatial attention in visual word processing.

Ss made lexical decisions on a target letter string presented above or below fixation. In Exps 1 and 2, target location was cued 100 msec in advance of target onset. Responses were faster on validly than on invalidly cued trials. In Exp 3, the target was sometimes accompanied by irrelevant stimuli on the other side of fixation; in such cases, responses were slowed (a spatial filtering effect). Both cuing and filtering effects on response time were additive with effects of word frequency and lexical status (words vs nonwords). These findings are difficult to reconcile with claims that spatial attention is less involved in processing familiar words than in unfamiliar words and nonwords. The results can be reconciled with a late-selection locus of spatial attention only with difficulty but are easily explained by early selection models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lorazepam on the distribution of spatial attention

A left persistent primitive sciatic artery was observed in a Japanese male cadaver. The sciatic artery arose from the internal iliac artery and perforated the ventral division of the sacral plexus. The sciatic artery did not anastomose with the perforating arteries nor the popliteal artery. The left femoral artery was incompletely developed, attenuating and terminating as the saphenous artery. Instead of the femoral artery, direct continuation of the profunda femoris artery, which probably corresponded to the fourth perforating artery, became the popliteal artery. Other vessel anomalies were observed in various regions. They included; (1) the retroesophageal right subclavian artery; (2) the left vertebral artery entering the transverse foramen of the 4th cervical vertebra; (3) bilateral occurrence of the superficial brachial artery; (4) the left gastric artery independently arising from the abdominal aorta; (5) a hepatolienomesenteric trunk; (6) three accessory renal arteries; (7) double testicular arteries; (8) the arteria intermesenterica; (9) a venous ring termed the 'renal collar', and (10) paired thoracic ducts. The present cadaver was considered to be a very rare case in which many primitive vascular systems had extensively persisted in various parts of the body.     

Dissociation of covert and overt spatial attention during prehension movements: selective interference effects

In four experiments, the influence of distractor objects on the temporal evolution of the reach-to-grasp movement toward a target object (an apple) was examined. In the first experiment, the distractor was another apple, which moved laterally behind the target and occasionally changed direction toward the target, thus becoming the to-be-grasped object. In the second and third experiments, the distractor was a stationary piece of fruit, which sometimes became the to-be-grasped object because of a change in illumination. The fourth experiment was a combination of the first two experiments. In all cases, selective interference effects on the transport and manipulation components were observed only when attention to the distractor was covert rather than overt. It is proposed that covert visuospatial attention selects information about distracting but potentially important stimuli, such that a registration of significance is accomplished without the need to process all available information.     

The effects of text-based interest on attention and recall.

Attentional demands and recall for stories that differed in rated interest were examined. More interesting stories required fewer attentional resources for comprehension than did less interesting stories (Experiment 1). Overall recall did not differ across story interest, but story interest did interact with type of encoding in terms of recall levels (Experiment 2). Relational encoding improved recall for low-interest stories but not high-interest stories; the reverse pattern was obtained with a manipulation encouraging extensive processing of the individual propositions. We suggest that interesting stories free up resources for relatively optional organizational processing of the text elements, thereby rendering additional relational processing redundant (for recall). Less interesting stories require more resources to keep attention focused on encoding the individual propositions, thereby rendering additional proposition-specific processing redundant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivation sharpens exogenous spatial attention.

[Correction Notice: An erratum for this article was reported in Vol 7(4) of Emotion (see record 2007-17748-024). The supplemental materials link is as follows: http://dx.doi.org/10.1037/1528-3542.7.3.668.supp.] Although both attention and motivation affect behavior, how these 2 systems interact is currently unknown. To address this question, 2 experiments were conducted in which participants performed a spatially cued forced-choice localization task under varying levels of motivation. Participants were asked to indicate the location of a peripherally cued target while ignoring a distracter. Motivation was manipulated by varying magnitude and valence (reward and punishment) of an incentive linked to task performance. Attention was manipulated via a peripheral cue, which correctly predicted the presence of a target stimulus on 70% of the trials. Taken together, our findings revealed that the signal detection measure, reflecting perceptual sensitivity, increased as a function of incentive value during both valid and invalid trials. In addition, trend analyses revealed a linear increase in detection sensitivity as a function of incentive magnitude for both reward and punishment conditions. Our results suggest that elevated motivation leads to improved efficiency in orienting and reorienting of exogenous spatial attention and that one mechanism by which attention and motivation interact involves the sharpening of attention during motivationally salient conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When cross-modal spatial attention fails.

There is now convincing evidence that an involuntary shift of spatial attention to a stimulus in one modality can affect the processing of stimuli in other modalities, but inconsistent findings across different paradigms have led to controversy. Such inconsistencies have important implications for theories of cross-modal attention. The authors investigated why orienting attention to a visual event sometimes influences responses to subsequent sounds and why it sometimes fails to do so. They examined visual-cue-on-auditory-target effects in two paradigms--implicit spatial discrimination (ISD) and orthogonal cuing (OC)--that have yielded conflicting findings in the past. Consistent with previous research, visual cues facilitated responses to same-side auditory targets in the ISD paradigm but not in the OC paradigm. Furthermore, in the ISD paradigm, visual cues facilitated responses to auditory targets only when the targets were presented directly at the cued location, not when they appeared above or below the cued location. This pattern of results confirms recent claims that visual cues fail to influence responses to auditory targets in the OC paradigm because the targets fall outside the focus of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric asymmetries of near-far spatial attention.

Although most of the visual cognitive activities performed by the left hemisphere take place close to the body (peripersonal space), most visual cognitive activities mediated by the right hemisphere take place in extrapersonal space. The left hemisphere, therefore, may have a propensity to direct attention toward the body and the right hemisphere away from the body. Because attentional bias influences judgments of spatial magnitude, the authors tested this hypothesis. Normal participants were asked to compare the size of horizontal lines presented in the sagittal plane in either right or left hemispace. When participants looked leftward, lines appeared shorter than when participants looked rightward. These results are consistent with the hypothesis that the right hemisphere directs attention toward visual extrapersonal space and the left hemisphere directs attention toward visual peripersonal space. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The combined effect of gaze direction and facial expression on cueing spatial attention.

Empirical evidence shows an effect of gaze direction on cueing spatial attention, regardless of the emotional expression shown by a face, whereas a combined effect of gaze direction and facial expression has been observed on individuals' evaluative judgments. In 2 experiments, the authors investigated whether gaze direction and facial expression affect spatial attention depending upon the presence of an evaluative goal. Disgusted, fearful, happy, or neutral faces gazing left or right were followed by positive or negative target words presented either at the spatial location looked at by the face or at the opposite spatial location. Participants responded to target words based on affective valence (i.e., positive/negative) in Experiment 1 and on letter case (lowercase/uppercase) in Experiment 2. Results showed that participants responded much faster to targets presented at the spatial location looked at by disgusted or fearful faces but only in Experiment 1, when an evaluative task was used. The present findings clearly show that negative facial expressions enhance the attentional shifts due to eye-gaze direction, provided that there was an explicit evaluative goal present. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The emergence of spatial rotation deficits in dementia and normal aging.

The mental rotation required in the Road Map Test of Direction Sense (the "Road Map Test"; J. Money, 1976; J. Money, D. Alexander, & H. T. Walker, 1965) has been thought to be impaired as a function of age, but not dementia. However, spatial rotation in dementia has not been investigated in reference to spatial coordinate systems. Patients with dementia (Alzheimer's and ischemic vascular dementias) and elderly control participants were administered the Road Map Test. The authors analyzed whether the geocentric or egocentric coordinate system determined rotation of Road Map Test turns and predicted impairment in dementia patients. They found equivalent impairment in both types of dementia, greater angulation effect in the geocentric system in patients relative to normal controls, and no egocentric effect. Results also suggest early emergence of spatial rotation deficit in dementia. Spatial rotation is most often associated with working memory, which predicts the correlations found. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of labeling and pointing on children's selective attention.

20 boys and 20 girls at each of 3 grade levels (3rd, 5th, and 7th) were tested in an incidental learning task designed to clarify the role of labeling on children's selective learning. Half the Ss labeled the central stimuli, and half pointed to them as they were exposed. Central learning increased and incidental learning decreased from 3rd to 5th to 7th grade. Labeling facilitated central learning, but pointing did not. Both labeling and pointing reduced incidental learning. Results indicate that labeling has both attention focusing and encoding effects but that the latter are more important for central learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)