Biomedical subjects

S P Tipper

Publications and source records attributed to S P Tipper.

34 records · Page 2Linked to original sources

PubMed1997

Externally cued and internally generated selection: differences in distractor analysis and inhibition.

In most studies of selective attention, the experimenter informs the participant what the target is and what action is required. For example, participants may be told to name the red drawing. The present study shows that under such conditions of external selection, distractor inhibition is used to ensure that selection is efficient. In external selection, analysis of distractors is limited, causing later recognition of distractor items to be poor. In contrast, during real-world selection a person may be confronted with a number of potential targets and may have to decide what will be the target for action. Under these conditions of internal selection, inhibition of distracting information does not occur. Moreover, distractors are more fully analyzed and thus better recognized at a later test.

Analysis of Variance↗

PubMed1996

Inhibitory mechanisms of neural and cognitive control: applications to selective attention and sequential action.

This paper discusses the role of inhibition in neural and cognitive control, in particular its role in selective processes in perception and action. We first review neuroanatomical and physiological evidence that cortical control is mediated by a variety of local-circuit inhibitory neurons, distributed throughout all layers and areas of the cortex. We then consider the use of inhibition in control processes in behavioral neural network models, focusing on two areas: selective attention and sequential action. Relations between the architecture and dynamics of these models and relevant neurological findings are discussed. We conclude that a full understanding of inhibitory control of mental functioning will require the integration of data from both the behavioral and neural levels, and that formal neural network models can play an important role in bridging this epistemological divide.

Attention↗

PubMed1996

Representational momentum and memory for luminance.

Representational momentum (RM) is a distortion in memory for the final position of an object in the direction implied by a set of discrete inducing displays (J.J. Freyd, 1987; J.J. Freyd & R.A. Finke, 1984). The effect has been shown under a wide variety of circumstances, which has led to assertions that it is a general enough phenomenon to extend to virtually any dimension of change. It is reported here that decisions about luminance seem not to be subject to RM. Instead, a robust effect in the direction opposite to that predicted by the RM hypothesis was observed. It is argued that RM might be more usefully considered limited to dimensions of change correlated with motion in the real world, and some initial hypotheses as to the nature of the mechanism underlying this new luminance effect are presented.

Adult↗

PubMed1996

Object-centered not scene-based visual neglect.

Whether visuospatial attention accesses object-centered representations, in addition to location-based coordinates, was investigated in patients with hemispatial neglect who detected a target on the left or right of a single object (2 connected circles or barbell) or of 2 objects (2 unconnected circles). The object or objects either remained static (left circle in left space) or rotated by 180 degrees (left circle now in right space). Relative to the static condition, in the rotating condition, detection times are facilitated on the left (contralateral) and inhibited on the right (ipsilateral) of space even when eye movements are controlled. This modulation of neglect was only observed for the single object, but not for the 2-object displays. The findings suggest that attention operates on object-centered as well as on location-based representations, and thus accesses multiple reference frames.

Aged↗

PubMed1996

Inhibition of return to successively cued spatial locations: commentary on Pratt and Abrams (1995).

J. Pratt and R.A. Abrams (1995) reported that the inhibition of return of attention is found only for the most recently attended of 2 cued locations. This study does not dispute their findings, but suggests that a more ecologically valid experiment would have more than 2 possible target locations. Twelve male students participated in an experiment in which the target may occur in 1 of 4 possible locations, after 3 of those locations have been cued exogenously in sequence. Inhibition of return was found for each of the cued locations. This result suggests that inhibition may be an important mechanism for aiding visual search in complex environments.

Adult↗

PubMed1994

Object-based and environment-based inhibition of return of visual attention.

Efficient search for an object often requires that attention be prevented from returning to recently examined environmental loci. M. I. Posner and Y. A. Cohen (1984) proposed that inhibition of return (IOR) of visual attention is a search mechanism that prevents such attentional perservation. The internal representations upon which IOR functions were examined and the following conclusions were drawn: First, IOR mechanisms have access to both object- and environment-based representations. Second, environment-based inhibition can be associated with a featureless environmental location, whereas the object-based mechanism requires that attention be oriented to a visible object. These findings are discussed in terms of physiological pathways that may mediate location- and object-based effects.

Attention↗

PubMed1992

Selective reaching: evidence for action-centered attention.

Most studies of selective attention briefly present static 2-dimensional stimuli and require arbitrary responses such as verbal naming or a keypress. Many of our perceptual-motor interactions with the environment, however, require reaching directly toward an object while ignoring other objects in the scene. A series of experiments examines selective attention in the latter reaching situation. Effects previously observed in the traditional experimental procedures were obtained, suggesting that the models developed (which propose inhibitory mechanisms, e.g.) apply to ecologically valid situations. Attention accesses action-centered internal representations during such tasks.

Adult↗

PubMed1991

Inhibitory mechanisms of attention in identification and localization tasks: time course and disruption.

It has been proposed that 1 component of the mechanism of visual selective attention is active inhibition of distracting information. A series of studies examines the time course of inhibition and the possible interfering effects of other task demands. Results demonstrate that inhibition can last at least 7 s after selection processes and that it is unaffected by predictable, unrelated intervening events. However, intervening events that are less predictable, or are the same as the inhibited stimulus, disrupt inhibition. Such results motivate a reconsideration of the previous view of distractor inhibition as a transient, fragile phenomenon.

Adolescent↗

PubMed1991

Object-centred inhibition of return of visual attention.

Our response to visual events can be delayed at positions we have recently examined attentively. Such inhibition could organize visual search through static scenes by suppressing those loci already searched, but this mechanism would fail in moving scenes as objects' locations then change during search. We cued attention to a moving object and found subsequent inhibition at the locus the object later occupied. This implies that previously examined objects are suppressed. Such object-centred inhibition would be highly adaptive, but would require a sophisticated neural implementation for a mechanism held to be sub-cortical.

Adult↗

PubMed1991

Inhibitory mechanisms of attention: locus, stability, and relationship with distractor interference effects.

This paper examines three properties of attentional inhibition mechanisms. First, previous research has suggested that the inhibitory mechanism of selective attention has a central locus between perception and action. We attempt to confirm the locus of this inhibition. Second, the processing of an unattended stimulus has been observed via the effects of the stimulus on a concurrent target (interference), and on a subsequent target (negative priming). The former effect demonstrates that distractors interfere with the processing of the target, and the latter negative priming effect implies that distractors are inhibited during selection. We demonstrate that these two measures of unattended processing can be dissociated. Third, we reveal that inhibition appears to be a stable mechanism of selection, in that effects do not decline after a large number of experimental trials.

Attention↗

PubMed1990

Selection of moving and static objects for the control of spatially directed action.

Research studying visual selective attention has largely examined filtering tasks in which stationary targets are selected from stationary distractors by a physical cue such as location and identity is the reported attribute. During many interactions with the visual environment however, target stimuli are selected by what they are, whereas action is controlled by where the stimulus is located. This study demonstrates that the interference and negative priming effects observed in standard filtering tasks, which suggest that distractors are analyzed and subsequently inhibited during selection, are also observed when targets are selected on the basis of identity and spatial location is the reported attribute. Furthermore, experimental results suggest that inhibition associated with distracting objects in this new task is object-centered, so that if the object is moving through space, inhibition moves with it.

Adult↗

PubMed1989

Mechanisms of attention: a developmental study.

A model of selective attention is proposed which contains a number of properties. First, stimuli which are irrelevant to the subjects' task can be analyzed to semantic levels automatically, and such stimuli can produce intrusion/interference effects. Second, two mechanisms by which selection is achieved are habituation to, and inhibition of, these irrelevant stimuli. A series of studies demonstrates that both the ability to process automatically irrelevant stimuli and the habituation mechanisms of attention are observable by Grade 2, whereas the inhibitory mechanism is not always evident at this stage. It is suggested that the greater distractability of children in certain situations may be due in part to the underutilization of this inhibitory mechanism. We further propose that children may be able to employ inhibitory mechanisms in more familiar perceptual-motor tasks.

Adolescent↗

PubMed1988