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PubMed1991

Attentional focussing and spatial stimulus-response compatibility.

The relative functional significance of attention shifts and attentional zooming for the coding of stimulus position in spatial compatibility tasks is demonstrated by proposing and testing experimentally a tentative explanation of the absence of a Simon effect in Experiment 3 of Umiltà and Liotti (1987). It is assumed that the neutral point of the spatial frame of reference for coding spatial position is at the position where attention is focussed immediately before exposition of the stimulus pattern. If a stimulus pattern is exposed to the right or the left of this position a spatial compatibility effect can be observed when the stimulus-response pairing is incompatible. Generalizing from this, one can say that a spatial compatibility effect will be observed if the last step in attentional focussing of the stimulus attribute specifying the response is a horizontal or a vertical attention shift. If the last step in focussing is attentional zooming (change in the representational level attended to), the stimulus pattern is localized at the horizontal and the vertical positions where the last attention shift had positioned the focus. In this case the spatial code is neutral on these dimensions and so no spatial compatibility effect should result. To test this model we conducted two experiments. Experiment 1 replicated the finding of Umiltà and Liotti that there is no Simon effect in the condition with no delay between a positional cue (two small boxes on the left or right of a fixation cross) and the imperative stimulus, whereas in the condition with a delay of 500 ms a Simon effect was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Visual attention orienting in liver cirrhosis without overt hepatic encephalopathy.

The attention system in patients with liver cirrhosis has not yet been fully investigated. We therefore studied visual attention orienting in cirrhotic patients without overt hepatic encephalopathy. Seventy cirrhotic patients without overt hepatic encephalopathy (aged 57 +/- 10 yr., mean +/- s.d.) and 55 controls (aged 49 +/- 12 yr.) were enrolled. Visual attention orienting was evaluated by a computerized neuropsychological test. The Reitan A test, commonly used to detect subclinical hepatic encephalopathy, was used to evaluate mental performance. Psychometric test scores were reduced in cirrhotics compared to controls (attention test: neutral condition = 495 +/- 149 vs. 401 +/- 98 msec; valid condition = 434 +/- 110 vs. 398 +/- 84 msec; invalid condition = 485 +/- 146 vs. 392 +/- 110 msec; p < 0.001; Reitan A test = 52 +/- 20 vs. 35 +/- 11 sec., p < 0.001). The attention effect of the cue was found both in controls and cirrhotics; however, it was significantly higher in cirrhotics than in controls (61 +/- 111 vs. 33 +/- 41 msec; p < 0.002). The attention effect was directly correlated with Reitan A test (r = 0.23, p = 0.05) in cirrhotics. In conclusion, in cirrhotic patients without overt hepatic encephalopathy, visual attention orienting was present and focusing to an indexed location had a higher effect on reaction time compared to controls, possibly because of reduced basal arousal.

Aging↗
PubMed2002

Nicotine-induced enhancement of attention in the five-choice serial reaction time task: the influence of task demands.

RATIONALE: Beneficial effects of nicotine on cognitive processes including attention have potential therapeutic uses and have been proposed as incentives for tobacco smoking. OBJECTIVES: To establish task conditions under which the effects of nicotine on attention are obtained reliably and to characterise such effects further. METHODS: Rats were trained in a modified version of the five-choice serial reaction time task (5-CSRTT) to detect 1-s light stimuli with greater than 70% accuracy and fewer than 20% omission errors. Nicotine was tested under different task requirements by varying signal event rate, stimulus duration and stimulus predictability, and by introducing white-noise distractors. RESULTS: Nicotine (0.05-0.2 mg/kg, s.c.) repeatedly improved accuracy and reduced omission errors and reaction times, leading to increases in numbers of reinforcers earned. Anticipatory responding was increased. Parametric modifications intended to increase demands on sustained attention did not affect performance in a manner suggesting that this subtype of attention was being taxed, and the effects of nicotine were not more marked under such conditions. Shorter stimulus durations impaired performance, but this manipulation weakened the effect of nicotine on accuracy. In contrast, the presence of noise distractors facilitated the effects of nicotine to the extent that distractor-induced impairments were abolished by the drug. CONCLUSIONS: The 5-CSRTT can provide a sensitive rodent model for the attention-enhancing effects of nicotine. Changes made to the procedure may have increased its sensitivity to nicotine, particularly with respect to accuracy. There were indications that the effects of nicotine were largest on processes of selective attention or on disengaging attention from irrelevant events and shifting it to behaviourally significant stimuli.

Analysis of Variance↗
PubMed2002

Salivary cotinine levels in human tobacco smokers predict the attentional validity effect size during smoking abstinence.

RATIONALE: The link between attention and brain cholinergic neurotransmission is widely accepted. Human chronic tobacco smokers maintain high levels of nicotine in plasma and body tissues and show enhanced attentional orienting and other attentional tasks. OBJECTIVE: We wished to test whether abstinence from smoking caused levels of the nicotine metabolite cotinine to decline and attentional enhancement to be reduced in a correlated manner. METHODS: The levels of salivary cotinine and behavioral performance on a cued target detection task were measured in chronic, adult tobacco smokers over a 5-day abstinence period. Control groups assessed over the same time period include non-smokers, smokers that did not abstain from tobacco, and smokers that abstained for 4 days and smoked on the last day. RESULTS: In all groups with tobacco exposure, the levels of cotinine declined steadily with time after abstinence, reaching near zero levels at day 5. During this period, reaction times declined as well for all groups, due in part to task practice effects. In contrast, the validity effect, which indexes attentional allocation, increased with abstinence and was inversely related to cotinine levels in groups exposed to tobacco. CONCLUSIONS: We conclude that 1) nicotine abstinence increases the attentional validity effect, and 2) this increase is indexed by salivary cotinine, and 3) that control levels of attentional performance are achieved after 3-4 days of tobacco abstinence.

Adult↗
PubMed2003

Reversal of visual attention dysfunction after AMPA lesions of the nucleus basalis magnocellularis (NBM) by the cholinesterase inhibitor donepezil and by a 5-HT1A receptor antagonist WAY 100635.

RATIONALE: Degeneration of the cholinergic magnocellular neurons in the basal forebrain and their cortical projections is a major feature of the neuropathology of Alzheimer's disease (AD). In addition to memory dysfunction, attentional functions are also impaired in AD. OBJECTIVE: We investigated the extent to which the cholinesterase inhibitor donepezil reversed the attentional performance deficit in nucleus basalis magnocellularis (NBM) lesioned rats. We also examined the effects of a selective and potent 5-HT(1A) receptor antagonist, WAY 100635, on the attentional deficit of NBM lesioned rats. METHODS: We injected alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) into the NBM to selectively destroy cholinergic neurons projecting to the neocortex. Attentional functions were examined using the 5-CSRT task, in which hungry rats were required to locate brief visual targets presented randomly in one of five locations in a specially designed chamber. RESULTS. AMPA lesions of the NBM caused marked reductions in choline acetyltransferase activity (ChAT) ranging from 30 to 46% in medial areas of the cortex (medial-frontal and cingulate) and from 58 to 72% in more lateral areas (anterior-dorso-lateral and parietal). AMPA lesioned rats made fewer correct responses (choice accuracy), longer latency to correct response and an increase in the number of premature and perseverative responses. These impairments showed some recovery over the next 12 weeks. Reducing the duration of the visual stimulus reinstated the impairments in choice accuracy. The anticholinesterase inhibitor donepezil at 1.0 mg/kg but not 0.5 mg/kg reversed the impairments in choice accuracy and correct response latency. The premature and perseverative over-responding of AMPA lesioned rats remained unchanged. A dose of 0.1 mg/kg WAY 100635 to AMPA-lesioned rats improved their choice accuracy but did not shorten correct response latencies. The number of premature responses was reduced by WAY 100635 but perseverative over-responding was not affected. CONCLUSIONS: The attentional impairments induced due to cortical cholinergic dysfunction may be ameliorated by cholinergic treatments such as cholinesterase inhibitors. In addition, 5-HT(1A) receptors and the cortical cholinergic system exert balanced opposition in regulating attentional performance in the rat. Blockade of 5-HT(1A) receptors may be useful to treat some aspects of attentional dysfunction in AD.

Acetylcholine↗
PubMed2004

Transient disruption of attentional performance following escalating amphetamine administration in rats.

RATIONALE: Attentional deficits are thought to be critically involved in the development of positive symptoms in schizophrenia. The present experiment tests the general hypothesis that sensitization of the mesolimbic dopaminergic system contributes to the attentional deficits in schizophrenia. OBJECTIVES: The present study assessed attentional performance following administration of an escalating amphetamine regimen and subsequent "challenge" amphetamine administration in rats. METHODS: Rats were trained to perform a two-lever sustained attention task that involved discrimination of visual signals and no signal presentation. After reaching criterion, subjects were assigned to receive escalating amphetamine or saline. Attentional performance was assessed immediately following escalating amphetamine, following "challenge" amphetamine administration (1.0 mg/kg) to amphetamine-pretreated rats, and for 3 days after the challenge session. At the end of this experiment, a dose-response study was conducted with saline-pretreated rats to confirm the appropriateness of the challenge dose. RESULTS: Amphetamine-pretreated animals demonstrated a transient increase in errors on nonsignal trials following escalating amphetamine administration. The latency to press a lever was decreased during and after challenge amphetamine administration. Administration of 1.0 mg/kg amphetamine did not alter accuracy of amphetamine-pretreated animals or of saline-pretreated animals in the dose-response experiment. CONCLUSIONS: Prior escalating amphetamine administration transiently disrupted attention, increasing incorrect "claims" for a signal on trials when no signal was presented. The present data support the existing literature that escalating amphetamine regimens may be useful to model the attentional deficits that contribute to the psychotic symptoms in schizophrenia.

Amphetamine↗
PubMed2004

The priming effect of alcohol pre-load on attentional bias to alcohol-related stimuli.

BACKGROUND: Previous research has shown attentional bias toward alcohol-related stimuli in non-dependent social drinkers. The aim of this study was to investigate whether attentional bias towards alcohol-related stimuli would increase after priming with either one of two doses of alcohol (0.3 or 0.6 g/kg) or placebo. METHODS: Questionnaires were used to measure alcohol use, mood states, craving for alcohol and alcohol outcome expectancies. Attentional bias was assessed using a dot-probe detection task and a modified Stroop task. RESULTS: Mood ratings showed dose dependent increases in positive mood after the alcohol pre-load. In the dot-probe task, all subjects showed an attentional bias towards the alcohol-related stimuli over neutral stationery-related items, although the attentional bias was significantly positive only at the low alcohol dose. In addition, a negative correlation was found between the attentional bias under the high alcohol dose and the alcohol use questionnaire score. In the Stroop task, a dose related effect of alcohol was found, with subjects making more errors for alcohol-related words under the high alcohol dose. CONCLUSIONS: These data support ideas derived from the incentive learning theories of drug addiction. Furthermore, these data suggest that history of alcohol exposure may influence the priming effects of an alcohol pre-load on attentional bias.

Adolescent↗
PubMed2005

Attentional bias for caffeine-related stimuli in high but not moderate or non-caffeine consumers.

RATIONALE: Attentional bias for drug-related cues has been reported with a wide range of drugs, but to date the extent to which caffeine consumers show similar biases for caffeine-related stimuli has not been tested. The present study therefore examined this issue in terms of differences in attentional bias for caffeine-related words in High, Moderate and Non-caffeine consumers using a dot-probe word task following overnight caffeine abstinence. OBJECTIVES: This study was conducted to test whether caffeine consumers show an attentional bias for caffeine-related words, and whether such biases relate to habitual levels of caffeine use. METHODS: Sixteen High, Moderate and Non-consumers of caffeine were asked to complete a modified dot-probe task in order to measure attentional bias for caffeine-related relative to neutral control word groups. The task was completed following overnight caffeine abstinence, and participants also completed mood and caffeine-craving measures. RESULTS: The High consumer group showed a significant attentional bias for the caffeine-related words, but no such bias was seen in Moderate or Non-consumer groups. As expected, craving for caffeine was strongest in the High consumers and weakest in the Non-consumers. Attentional bias in the High group correlated with self-reported caffeine consumption and with craving for caffeine, but neither effect was significant in the Moderate group. CONCLUSIONS: These data confirm that High caffeine consumers show attentional bias for caffeine-related stimuli, consistent with current theories of drug addiction.

Adolescent↗
PubMed2003

The allocation of attention during locomotion is altered by anxiety.

We tested the hypotheses that: (1) anxiety regarding the possibility of falling alters the attentional demands of gait; and (2) this alteration in the attentional requirements of gait occurs independently of gait pattern accommodations. Sixteen younger and 15 older adults participated in this study. Subjects walked at a self-determined velocity along a 7.2-m walkway under four conditions of postural threat; the walking conditions varied depending on the width constraints of the walkway (60 cm vs 15 cm) and the height of the walking surface (0 cm vs 60 cm). Attentional demands of locomotion in each condition of testing were assessed using the dual-task methodology, in which participants verbally responded to an auditory cue as quickly as possible while continuing to walk. Our findings revealed that: (1) participants were successful in verbally responding to the auditory cue without modifying their gait pattern; (2) reaction times increased for all subjects when walking in the condition of greatest postural threat; (3) the attentional demands for locomotion varied with the phase of the gait cycle for younger adults but not for older adults; (4) the phase-dependent effect for younger adults disappeared in the condition of greatest postural threat, while reaction time scores for older adults systematically increased; and (5) increases in reaction time persisted despite significant changes in gait kinematics. Our findings confirm that anxiety increases the attentional demands for locomotion and provide further explanation for age-dependent increases in the attentional demands of gait. Furthermore, our findings confirm that fall-related anxiety predicates an increase in the allocation of attention to locomotor control that is independent of gait pattern adjustments.

Adult↗
PubMed2005

Control mechanisms mediating shifts of attention in auditory and visual space: a spatio-temporal ERP analysis.

The neural systems that mediate voluntary shifts of attention to visual and auditory stimuli were investigated by examining the patterns of human brain electricity elicited by attention-directing cues in auditory and visual tasks. Several lateralized event-related potential (ERP) components were observed when participants shifted attention in expectation of visual targets (experiment 1). One component was focused over frontal cortex and a second was focused primarily over the occipital-temporal cortex but also spread to parietal regions of the scalp. Previous work has indicated that the frontal component reflects supramodal processes involved in the executive control of attention and that the posterior component reflects either spatial attentional control processes in the posterior parietal lobe or modulation of processes in visual cortex. Here, the posterior component was observed when participants shifted attention in expectation of auditory targets (experiments 2-4), but the frontal component was found only in the visual task. The posterior component seemed to be generated in parietal and occipital areas even when there was no visual information about the to-be-attended locations. These results are consistent with the view that voluntary shifts of attention are mediated by supramodal processes in the parietal lobe and that the spatial coordinates of the to-be-attended location are based on visual representations of space.

Acoustic Stimulation↗
PubMed2004

Attentional, emotional and hormonal data in subjects of different ages.

The differences in attentional style among subjects of different ages and the influence of emotionality on the attentional components were studied for a limited experimental period. Variation in the hormonal data and its relation to behavioural parameters were also evaluated. The subjects enrolled in the study were divided into four age groups (A 18-29, B 30-45, C 46-59, D 60-77 years). The attentional tests involved different types of attention: alert, go/no-go, divided attention and working memory. Emotionality was assessed on the basis of skin conductance, heart rate and frontalis muscle tone. Testosterone (T), free testosterone (fT), non-specifically bound testosterone (NST), sex hormone binding globulin (sHBG), oestradiol, cortisol and adrenocorticotrophic hormone were determined in the plasma. The data were analysed to identify endocrine and behavioural differences related to sex and age. The results showed an influence of age on reaction time (RT) and RT variability. This was particularly evident for groups C and D with respect to A in the simple (alert) and complex RT tests (go/no-go and working memory). Divided attention, with the highest RT, showed a clear distinction between group A and the other groups. The difference in frontalis electromyography (EMG) (test vs control) increased with age, while the autonomic responses (skin conductance and heart rate) did not vary. In most attentional tests, the age-related reduction of RT was associated with increased T, fT and NST and decreased cortisol.

Adolescent↗
PubMed2002

Facilitation of local information processing in the attentional blink as indexed by the shooting line illusion.

Perception of the second of two rapidly sequential targets is impaired if the temporal lag between them is relatively short. This attentional blink (AB) is said to occur because the first target preoccupies attentional resources, leading to a shortage of attention for, and subsequent failure of judgement of, the second target. In the present study, we examined whether the attention which is preoccupied by the first target carries the common characteristic of spatial attention, that is local facilitation of information processing. To index the facilitation, we presented an attention-sensitive probe known as the shooting line illusion in which observers see a progressively drawn line from the attended end to the other. We found that illusory motion was perceived to emanate from the end where the first target was presented. This result demonstrates the inherently spatial nature of attention, even when it is defined by temporal and symbolic variables.

Adult↗
PubMed2004

Foreground-background segmentation and attention: a change blindness study.

One of the most debated questions in visual attention research is what factors affect the deployment of attention in the visual scene? Segmentation processes are influential factors, providing candidate objects for further attentional selection, and the relevant literature has concentrated on how figure-ground segmentation mechanisms influence visual attention. However, another crucial process, namely foreground-background segmentation, seems to have been neglected. By using a change blindness paradigm, we explored whether attention is preferentially allocated to the foreground elements or to the background ones. The results indicated that unless attention was voluntarily deployed to the background, large changes in the color of its elements remained unnoticed. In contrast, minor changes in the foreground elements were promptly reported. Differences in change blindness between the two regions of the display indicate that attention is, by default, biased toward the foreground elements. This also supports the phenomenal observations made by Gestaltists, who demonstrated the greater salience of the foreground than the background.

Adult↗
PubMed2001

Focused attention reduces the effect of lateral interference in multi-element arrays.

Lateral interference of nearby irrelevant flankers may be reduced when attention is already focused at a relevant position. This hypothesis was tested in three experiments with multi-element arrays consisting of one target and several neutral flankers with reaction time (RT) and proportion of errors (PE) as dependent variables. The arrays were preceded by peripheral cues that varied in size to induce different levels of focused attention. In a first experiment, the eccentricity effect was shown to be affected by attention, but no support was found for a reduction of lateral interference in the case of focused attention. However, these results may be due to an attentional bias for central elements. Two additional experiments were performed in which target-flanker distance was manipulated. RTs and PEs showed that the effect of target-flanker distance was smaller when the precise target position was indicated by a peripheral precue. Thus, focused attention seems to reduce the effect of lateral interference. These results can be explained most easily by a model in which attention already affects early perceptual processing.

Adult↗
PubMed2003

Are readers of our face readers of our minds? Dogs (Canis familiaris) show situation-dependent recognition of human's attention.

The ability of animals to use behavioral/facial cues in detection of human attention has been widely investigated. In this test series we studied the ability of dogs to recognize human attention in different experimental situations (ball-fetching game, fetching objects on command, begging from humans). The attentional state of the humans was varied along two variables: (1) facing versus not facing the dog; (2) visible versus non-visible eyes. In the first set of experiments (fetching) the owners were told to take up different body positions (facing or not facing the dog) and to either cover or not cover their eyes with a blindfold. In the second set of experiments (begging) dogs had to choose between two eating humans based on either the visibility of the eyes or direction of the face. Our results show that the efficiency of dogs to discriminate between "attentive" and "inattentive" humans depended on the context of the test, but they could rely on the orientation of the body, the orientation of the head and the visibility of the eyes. With the exception of the fetching-game situation, they brought the object to the front of the human (even if he/she turned his/her back towards the dog), and preferentially begged from the facing (or seeing) human. There were also indications that dogs were sensitive to the visibility of the eyes because they showed increased hesitative behavior when approaching a blindfolded owner, and they also preferred to beg from the person with visible eyes. We conclude that dogs are able to rely on the same set of human facial cues for detection of attention, which form the behavioral basis of understanding attention in humans. Showing the ability of recognizing human attention across different situations dogs proved to be more flexible than chimpanzees investigated in similar circumstances.

Animals↗
PubMed1993

Internal attentional switching: effects of predictability, complexity and practice.

The present research studies the effects that predictability, complexity and practice have on internal switching of attention; that is, on the reorienting of attention to different phases of task processing. To verify these effects we used a task that produces attentional switching through a combination of two kinds of trials. Although these ask the subjects to make a final 'same-different' judgement, they are different in their way of displaying the stimuli and impose different partial requirements. This combined presentation forces subjects to reorientate their attention. The experimental results point to a clear influence of practice that favours internal attentional switching when necessary. Neither predictability nor complexity show significant main effects. However, interaction between them is significant in the sense that with low levels of complexity the ease or difficulty with which attentional switching is carried out is unaffected by the predictability of the switching. By contrast, with a greater level of complexity, predictability was seen to favour the switching of attention.

Adult↗
PubMed1987

Mechanisms of visual attention revealed by saccadic eye movements.

This paper summarizes recent data on the initiation of saccadic eye movement in relation to the mechanisms of visual attention. In particular, the occurrence of express saccades, defined by their extremely short reaction times, is discussed on the basis of the observation that these saccades do not occur when the subjects (man or monkey) are attending to either a fixation point or to any other visual stimulus in the periphery of their field of view including the "future" saccade target location. It is concluded that the system of visual attention can be in two states: engaged or disengaged. In order to generate a saccade or to move attention from one point to another visual attention must be in the disengaged state. The disengagement takes some time which is or is not included in the saccadic reaction time depending on whether or not visual attention is engaged at the time of the onset of the saccade target. During engaged visual attention saccades are inhibited thereby providing steady central fixation or the absence of saccades during directed peripheral attention.

Attention↗
PubMed1988

Attentional factors in the occurrence of stimulus-response compatibility effects.

Two major hypotheses have been advanced to account for stimulus-response compatibility effects in the situation in which the location of the target is irrelevant for choosing the correct response. According to the attentional hypothesis, compatibility effects reflect a response bias, favoring the effector on the same side as the stimulus. According to the coding hypothesis, compatibility effects result from a correspondence between the spatial codes of the stimulus and effector. In the present study, two components of attention--selective attention and intention--were independently manipulated by providing selective preparatory information before onset of a target stimulus. Attentional information indicated where the target stimulus would occur; intentional information indicated which hand would have to be used to respond. Compatibility effects were observed only in the condition in which intentional information, but no attentional information, was provided. These findings support the attentional hypothesis and indicate that a specific aspect of attention, namely a selective readiness to respond to the stimulus, is a necessary condition for compatibility effects to occur.

Adolescent↗