Biomedical subjects

Richard A Abrams

Publications and source records attributed to Richard A Abrams.

17 recordsLinked to original sources

PubMed2006

Attentional modulation of the gap effect.

The gap effect refers to a reduction in the latency of saccades to peripherally appearing targets when the fixation point disappears a short time before target appearance. The effect has been attributed to a number of potential mechanisms that function to assist in the maintenance of fixation. One such mechanism, attention, has been the focus of some disagreement in the literature regarding the gap effect. In the present study, we had subjects attend to a portion of a complex fixation stimulus. On some trials the attended portion was removed prior to onset of a saccade target whereas on other trials an unattended portion was removed. Subjects were faster to initiate saccades when the attended portion was removed, thus establishing a role of attention in the gap effect. The results have important implications for our understanding of eye movements and the gap effect.

Adolescent↗

PubMed2006

Visual search for change in older adults.

Previous research has demonstrated that younger adults are surprisingly poor at detecting substantial changes to visual scenes. Little is known, however, about age differences in this phenomenon. In the 2 experiments reported here, older adults were slower than younger adults in detecting changes to simple visual stimuli. This age difference was beyond what would be expected given known age-related changes in processing speed. Examination of eye movement behavior during the search for change suggested that age-related changes in the useful field of view and degree of cautiousness play a significant role. Speed of processing and 3 age-related eye movement behaviors explained 85% of the variance in change detection latency, eliminating the effect of age.

Adolescent↗

PubMed2006

Inhibitory control in children with phenylketonuria.

Past studies have reported impairments in children with early-treated phenylketonuria (PKU) in executive abilities such as strategic processing and working memory. Findings have been inconsistent in terms of the integrity of inhibitory control, another executive ability. This study administered 4 inhibitory tasks (flanker, Stroop, go/no-go, antisaccade) to 26 children with PKU and 25 typically developing control children. Children with PKU performed more poorly than typically developing children on the 2 inhibitory tasks with the strongest experimental manipulations (go/no-go and antisaccade) between control and inhibitory conditions. Findings suggest that the inhibitory deficit associated with PKU is subtle and that inconsistent findings in past studies may be largely due to the insensitivity of experimental manipulations in some tasks.

Adolescent↗

PubMed2006

Motion onset captures attention: a rejoinder to Franconeri and Simons (2005).

Recently, we have provided evidence that the onset of motion captures attention (Abrams & Christ, 2003, 2005a, 2005b). In the present article, we clarify the motion onset hypothesis, we discuss recent data (Franconeri & Simons, 2005) that, at least on the surface, seem to challenge the hypothesis, and we present results from a new experiment (Christ & Abrams, 2005). Finally, we conclude that, although motion onset does indeed appear to capture attention, motion in the absence of a motion onset might also attract attention under certain circumstances.

Attention↗

PubMed2006

Just like new: newly segregated old objects capture attention.

Subjects searched for target letters that were either contained in or segregated from a group of distracting letters and were either moving or stationary. Subjects were faster to identify targets that had recently become segregated from the group regardless of whether the segregation was accomplished by (1) the element itself moving away from the group or (2) the group moving away from the segregated element. The results show that attention can be captured by newly apparent objects that are produced by a new grouping of an existing scene.

Attention↗

PubMed2005

An event-related functional magnetic resonance imaging study of voluntary and stimulus-driven orienting of attention.

Attention can be voluntarily directed to a location or automatically summoned to a location by a salient stimulus. We compared the effects of voluntary and stimulus-driven shifts of spatial attention on the blood oxygenation level-dependent signal in humans, using a method that separated preparatory activity related to the initial shift of attention from the subsequent activity caused by target presentation. Voluntary shifts produced greater preparatory activity than stimulus-driven shifts in the frontal eye field (FEF) and intraparietal sulcus, core regions of the dorsal frontoparietal attention network, demonstrating their special role in the voluntary control of attention. Stimulus-driven attentional shifts to salient color singletons recruited occipitotemporal regions, sensitive to color information and part of the dorsal network, including the FEF, suggesting a partly overlapping circuit for endogenous and exogenous orienting. The right temporoparietal junction (TPJ), a core region of the ventral frontoparietal attention network, was strongly modulated by stimulus-driven attentional shifts to behaviorally relevant stimuli, such as targets at unattended locations. However, the TPJ did not respond to salient, task-irrelevant color singletons, indicating that behavioral relevance is critical for TPJ modulation during stimulus-driven orienting. Finally, both ventral and dorsal regions were modulated during reorienting but significantly only by reorienting after voluntary shifts, suggesting the importance of a mismatch between expectation and sensory input.

Adult↗

PubMed2005

Onset but not offset of irrelevant motion disrupts inhibition of return.

In seven experiments, subjects were slower to detect targets in cued static objects than in uncued static objects, revealing inhibition of return (IOR). This occurred regardless of the presence or absence of continuous motion of other, task-irrelevant objects in the display. However, if the motion of the irrelevant objects began during the interval between cue and target, the amount of IOR was considerably reduced. Offset of motion during the cue-target interval had no effect. Implications for IOR, object perception, and attentional capture are discussed.

Attention↗

PubMed2005

The onset of receding motion captures attention: comment on Franconeri and Simons (2003).

Franconeri & Simons (2003) reported that some but not all types of motion capture attention in a visual search task, ostensibly because some types of motion are behaviorally significant. In the present article, we argue that a more parsimonious explanation of their results is that the onset of motion, but not motion per se, captures attention. This conclusion helps to resolve inconsistencies between the Franconeri and Simons findings and earlier reports from other investigators and is consistent with results that we have recently reported (Abrams & Christ, 2003). The Franconeri and Simons interpretation rests largely on their failure to find attentional capture by one type of motion-simulated receding motion. We report here the results of two experiments that demonstrate that the onset of receding motion does indeed capture attention when the motion is produced using stereo depth cues. As we have argued elsewhere, the capture of attention in displays containing motion appears to be dependent on the onset of the motion, rather than on the mere presence of specific types of motion as suggested by Franconeri and Simons. One possible explanation is that the onset of motion captures attention because it serves as a strong cue to animacy--and the detection of nearby animals can have important consequences for survival.

Attention↗

PubMed2004

Interference with spatial working memory: an eye movement is more than a shift of attention.

In the present experiments, we examined whether shifts of attention selectively interfere with the maintenance of both verbal and spatial information in working memory and whether the interference produced by eye movements is due to the attention shifts that accompany them. In Experiment 1, subjects performed either a spatial or a verbal working memory task, along with a secondary task requiring fixation or a secondary task requiring shifts of attention. The results indicated that attention shifts interfered with spatial, but not with verbal, working memory, suggesting that the interference is specific to processes within the visuospatial sketchpad. In Experiment 2, subjects performed a primary spatial working memory task, along with a secondary task requiring fixation, an eye movement, or an attention shift executed in the absence of an eye movement. The results indicated that both eye movements and attention shifts interfered with spatial working memory. Eye movements interfered to a much greater extent than shifts of attention, however, suggesting that eye movements may contribute a unique source of interference, over and above the interference produced by the attention shifts that accompany them.

Attention↗

PubMed2004

Hand movements deviate toward distracters in the absence of response competition.

In a series of experiments, participants reached to targets in the presence of visual distracters that were either adjacent to the target or located along the reach path. The reaching movements were affected by the presence of the distracters, with the movement paths deviating toward the distracters. Those deviations were observed under two different conditions: (a) one in which the distracter could potentially have been a movement target; and (b) another in which the distracter never was a possible target. Because the movement was affected by the distracter in both situations, the results suggested that response competition is not necessary for distracter-induced reach-path deviations. Instead, the authors propose that attention to a distracter is sufficient to affect the to-target movement. The movement deviations may reveal an effective mechanism for coping with stimulus-rich environments.

Adult↗

PubMed2004

Illusory gravitational forces affect aimed limb movements.

The authors report on 2 experiments in which participants produced rapid wrist-rotation movements in a clockwise direction to move a cursor from a home position into a target region. The display was constructed such that the target could be depicted above, below, or beside the home position, so that the clockwise wrist rotation could produce upward, downward, or rightward movements of the cursor. By parsing the movements into component submovements, the authors found that upward movements were consistently less forceful, as evidenced by shorter primary submovements, compared with downward and horizontal movements. Those results suggested a new virtual gravity illusion: Participants apparently overcompensated for the absence of the anticipated effects of gravity by adjusting the initial force they used to propel the cursor toward the target.

Adult↗

PubMed2003

Motion onset captures attention.

Although visual motion may seem salient, motion per se does not automatically attract attention. We show here, however, that the onset of motion does indeed attract attention. In three experiments, subjects identified target letters in displays that contained targets and distractors. There was no advantage for moving letters among static ones, but there was an advantage for objects that had recently started to move despite the fact that the motion was uninformative. If some additional time was allowed to elapse after motion onset, inhibition of return slowed responding to the item that had started to move-a further sign that the motion onset had captured attention. Finally, detection of target letters was found to be independent of the number of distractors in the display if the target had undergone motion onset, also indicative of attentional capture. We discuss the adaptive significance of sensitivity to onsets in the presence of a relative insensitivity to ongoing motion.

Adult↗

PubMed2003

Inhibitory control following perinatal brain injury.

Evidence from developmental, lesion, and neuroimaging studies indicates that the prefrontal cortex plays a major role in executive abilities, including inhibitory control. Proficient executive performance, however, relies not only on the integrity of the prefrontal cortex but also on its interactions with other brain regions. In the current study, the authors focused on the effect that early damage to the white matter tracts interconnecting prefrontal and other brain regions has on inhibitory control. Data were collected from 13 children with bilateral spastic cerebral palsy and from a control group of 20 children with no history of neurologic compromise. Converging evidence from 3 separate paradigms is presented that strongly suggests these children experience impairments in inhibitory control. Findings are discussed within the context of current cognitive and neuroanatomical models of inhibition.

Adolescent↗

PubMed2003

A comparison of private and public dental students' perceptions of extramural programming.

This project was undertaken to compare the opinions of private and public dental school students' perceptions concerning extramural programming, which is defined as any aspect of the curriculum in which undergraduate dental students provide dental care outside the main dental facility. A survey instrument was used to collect data from undergraduate students at a private (N = 267; 88.4 percent response rate) and at a public (N = 213; 67.2 percent response rate) dental school. When asked to rate the value of various extramural sites in making them a better dentist, both groups rated private dental offices the most valuable and prisons the least valuable. When questioned about the amount of time students should spend each year in extramural programming, private students, overall, desired 34 percent more time than did public students. When asked what percentage of the total time spent in extramural programming students should spend providing various categories of dental care, public school students thought 26 percent more time should be spent rendering preventive services/health education than did the private students. The private students indicated a stronger desire (13 percent more) for rendering clinical services than did public students. Both private and public students were most likely to enter group private practice after graduation. The increasing interest in community-based programs makes the information gained from this study useful for future curriculum planning.

Community Dentistry↗

PubMed2002

Object-based selection within and beyond the focus of spatial attention.

In a series of experiments, we examined the effect of perceptual objects on visual attentional processing in the presence of spatially cued attentional selection. Subjects made speeded judgments about two visual elements that were either both on the same object or on two different objects. Judgments were faster when the elements were on the same object than when they were on different objects, revealing an object advantage. Importantly, the object advantage remained even when either exogenous or endogenous spatial cues were used to direct the subjects' attention to a part of the display, contrary to earlier findings of other researchers. The object advantage, however, did disappear when the stimulus duration was shortened substantially. The results show that object-based selection is pervasive and is not diminished by the act of selective attention. The results are discussed in terms of their implications for the mechanisms that underlie attentional selection.

Attention↗

PubMed2002

Inhibition of return in static and dynamic displays.

Inhibition of return (IOR) causes people to be slower to return their attention to a recently attended object (object-based IOR) or location (location-based IOR). In attempts to separately measure the two components, moving stimuli have been used that permit the dissociation of the attended object from its location when it was attended. The implicit assumption has been that both object- and location-based components of IOR will operate whenever the cued object and cued location are identical. We show here that although this assumption may be true in a static display, it appears to be unwarranted when moving stimuli are involved: Very little IOR is observed when a cued object moves away from, and then subsequently returns to, its initial location. Thus, the processes that underlie IOR operate very differently in static versus dynamic scenes.

Eye Movements↗

PubMed2001

Random visual noise impairs object-based attention.

Object-based visual attention is observed when the benefit of attending to one element in a display extends to other elements that are part of the same perceptual object. Apperceptive agnosia is an object identification deficit in which spatial attention is preserved but object-based attention is impaired. Some debate exists regarding the extent to which the object-based impairment can be attributed to perceptual mechanisms that are specifically involved in grouping and segmentation of a scene, as opposed to early sensory processes. In the present paper we show that random visual noise is sufficient to eliminate the object benefit, a result inconsistent with the view that grouping mechanisms are responsible for the effect. The results have implications for an understanding of apperceptive agnosia, and for an understanding of object-based attention more generally.

Adult↗