Selective Attention Deficits Research Articles

Aging and selective attention: an issue of complexity or multiple mechanisms?

Previous studies have shown age-associated deficits in selective attention that vary as a function of task demands. The present study was conducted to dissociate the effect of task complexity on age-related performance differences from qualitative differences in cognitive demands. Twenty-four young and 24 older adults were administered two versions of the Stroop Test (Hartley, 1993). The Color-Block version required identifying the color of a box while ignoring the name of a color printed either above or below the box. The Color-Word version required naming the color of a word while ignoring the semantic meaning of the word (a color name). Each version of the task included a two- and four-color choice condition as a manipulation of task complexity. Old and young adults performed comparably on the Color-Block Task, but older adults were significantly impaired on both conditions of the Color-Word Task, particularly in the four-choice condition. Results suggest age-related differences in the distinct attentional processes demanded by each task are not attributable to general slowing.

The "benefits" of distractibility: mechanisms underlying increased Stroop effects in schizophrenia.

Recent studies of selective attention in schizophrenia patients suggest a particular pattern of single-trial Stroop performance: increased facilitation but not interference in reaction times (RTs), combined with increased error interference. Our Stroop task analysis suggests that this pattern can be explained by a selective attention deficit if one accounts for (1) performance in the congruent condition; (2) the nature of the neutral stimulus; (3) the relationship between accuracy and RT; and (4) response set effects. To test these hypotheses, we examined Stroop performance in 40 DSM-IV schizophrenia patients and 20 healthy control subjects, using a range of neutral stimuli (color patches, noncolor words, color words not in the response set). The findings confirmed several of our predictions and the results were consistent with the hypothesis that abnormal Stroop performance in schizophrenia reflects a failure to adequately attend to the task-appropriate stimulus dimension (color). This inattention affects both the congruent and incongruent conditions and multiple points in the information processing pathway.

420 Visual and auditory event related potentials in amyotrophic lateral sclerosis

In humans, selective attention is assumed to be under control of the frontal lobe. A significant proportion of patients with amyotrophic lateral sclerosis (ALS) shows impairments in various tasks touching frontal lobe function. We, therefore, undertook a study of event-related EEG potentials (ERPs) in eight non-demented ALS patients in order to investigate a possible deficit of auditory selective attention: tones were presented in random sequence to the left or right ear, one of which was to be attended. The negative shift of the ERPs evoked by attended tones in relation to unattended tones (`processing negativity': PN) was smaller in ALS patients than in age-matched healthy control persons. This was true for Fz and Cz and for both a slow and a fast presentation rate of the tones. In the patients, reduced PN amplitude correlated with functional motor impairment. The utility of ERP testing to assess impaired frontal lobe function is shown for the first time in ALS patients. The results of our study fit to recent positron emission tomography (PET) and fMRI data.

The Stroop task and attention deficits in schizophrenia: a critical evaluation of card and single-trial Stroop methodologies.

The Stroop task, considered by many to be a paradigmatic measure of selective attention, has often been employed to investigate attention deficits in schizophrenia. Card and single-trial versions of this task have yielded different results. In this study both card and single-trial versions were administered to healthy controls (n = 24) and patients with schizophrenia (n = 55). No differences in reaction time (RT) interference were found on either version. On the single-trial version, patients showed greater RT facilitation and error rate interference, evidence for a deficit in selective attention. Methodologic and analytic issues that account for the mixed results from earlier card Stroop studies are addressed. It is concluded that single-trial versions provide greater sensitivity to selective attention pathology in schizophrenia.

The neuropathogenesis of delirium

Delirium is a common and serious complication of acute illness in people admitted to hospital. Recent evidence suggests that delirium is associated with an increased subsequent risk of developing dementia, although it is unclear whether delirium merely serves as a marker of a preexisting risk or whether it may of itself provoke or facilitate development of permanent brain damage (1). Despite the importance of delirium, relatively little is known about the neuropathogenesis of the disorder. The main hypothesis at present is that delirium represents the clinical manifestation of diffuse, reversible impairment of neurotransmission and of cerebral oxidative metabolism. This hypothesis explains the relatively stereotyped nature of the response to a wide range of insults and the characteristic generalized slowing of the EEG trace in most cases of delirium. However, there is little direct evidence of impaired cerebral oxidative metabolism in delirium. The finding of delirium as a feature of some strokes suggests that more focal disturbances can also cause delirium. Conflicting findings have been reported from the few studies using positron emission tomography or single photon emission tomography in delirious patients. Various neurotransmitter systems have been implicated in the pathogenesis of delirium. The cholinergic hypothesis has attracted most attention. This proposes that reduced synthesis of acetylcholine is a final common pathway for development of delirium. Anticholinergic drugs are a potent cause of delirium, and anticholinergic toxicity is an established animal model for delirium at present; also, anticholinergic pathways are involved in regulation of attentiveness, disruption of which is a cardinal feature of delirium. However, there is a wide number of other candidate neurotransmitters including dopamine, serotonin GABA, glutamate, opioids and noradrenaline, and it is unlikely that changes in a single neurotransmitter can explain the protean features and aetiological factors of delirium. The existence of distinct behavioural subtypes may provide additional clues to the pathogenesis of delirium. Two characteristic subtypes are described: an agitated (hyperactive-hyperalert) variant, typified by delirium tremens, and a retarded (hypoactive-hypoalert) variant, typified by the metabolic encephalopathies. However, many patients switch between hypoactivity and hyperactivity and many aetiological factors, such as infection, can cause either variant. Also, although delirium tremens is classically associated with EEG fast wave activity, slow wave activity is more characteristic of agitated delirium due to anticholinergic medications or traumatic brain injury. Nevertheless, different subtypes may involve different neurotransmitter pathways, and require different treatments. It has been proposed that delirium might be a stress reaction in the elderly due to increased levels of glucocorticoids or an increased vulnerability to their effects (2). Hypothalamic-pituitary-adrenal (HPA) activation is related to cognitive impairment in depression and dementia, and increased glucocorticoid levels can cause hippocampal damage. Cushing’s syndrome and exogenous glucocorticoids can cause delirium (as can sudden cessation of glucocorticoid therapy). Glucocorticoids cause prominent deficits in selective attention; such deficits are a characteristic feature of delirium but not usually of dementia. In demented patients, the greatest slow wave EEG activity occurs in patients with highest resting cortisol levels. A number of studies have now demonstrated HPA activation in delirious patients. For example, in stroke patients, post-dexamethasone cortisol levels were associated with delirium, independently of the site and severity of the stroke (3). It remains unclear whether hypercortisolaemia is of pathogenetic significance in delirious patients or is simply a result of the stress of delirium or of the underlying illness. Even if HPA activation results from rather than causes delirium, it is possible that excessive cortisol secretion might mediate damage to hippocampal neurons thereby producing permanent brain damage and cognitive loss. Other interactions between the nervous and immune systems have also been implicated in the pathogenesis of delirium. Interleukin-1 released from macrophages or microglia can induce activation of

Decreased anterior cingulate gyrus metabolic rate in schizophrenia.

This study examined glucose metabolism in the anterior and posterior cingulate cortex in schizophrenia. Fifty unmedicated male schizophrenic patients and 24 normal men were studied with positron emission tomography. Compared with the normal men, the schizophrenic patients had lower relative metabolic rates in the anterior cingulate and higher rates in the posterior cingulate. The findings suggest hypofunction in the anterior cingulate cortex in schizophrenia.

The role of selective attention in driving and dementia of the Alzheimer type.

This paper examines the relationship between cognitive processes and driving in aging and dementia of the Alzheimer type. Several studies that have explored the relationship between neuropsychological test performance and various indicators of driving safety are reviewed. It is argued that deficits in selective attention are specific to impaired driving performance in dementia of the Alzheimer type. Results from a recent study supporting this notion are presented. It is suggested that screening measures that emphasize the ability to selectively attend to relevant information and inhibit irrelevant information should be used to identify mildly demented individuals who are at risk for unsafe driving.

Reality monitoring failure in schizophrenia: The role of selective attention

Reality monitoring and selective attention have been repeatedly shown to be impaired in schizophrenia. Positive symptomatology has been found to be associated with deficits in both reality monitoring and selective attention. Therefore, a direct link between reality monitoring and selective attention was hypothesized. Thirty-two schizophrenic patients and 32 normal controls were administered the Stroop test as a measure of selective attention along with a test of three indices of reality monitoring, involving discrimination of: events vs. non-events, self- vs. externally-generated events, and oral vs. pictorial sources. A global memory test was administered for comparison. Results showed that schizophrenic patients were impaired in both reality monitoring and selective attention, and that these two were significantly correlated with each other in the schizophrenic sample. On the contrary, selective attention was not significantly correlated with memory efficiency in either group. Further, multiple regression analyses in schizophrenic patients showed that only selective attention contributed significantly to the variance in reality monitoring measures. Therefore, the results argue in favor of a specific role of a selective attention deficit in reality monitoring failure in schizophrenia.

Anterior cingulate gyrus dysfunction and attentional pathology in schizophrenia

Selective attention deficits are a prominent aspect of the cognitive dysfunction seen in schizophrenia. The anterior cingulate gyms (ACG) is often proposed to be a key element in neural systems involved in attentional control. Structural and histopathological studies have suggested neuroanatomical abnormalities in the anterior cingulate 'in schizophrenia (1). The objective of the present study was to test the hypothesis that dysfunction of the ACG in schizophrenia is related to the selective attention deficits seen in this illness.

Stroop interference and disorders of selective attention

Fourteen patients with a right-hemisphere CVA and 8 patients with a left-hemisphere CVA were examined for selective attention deficits using a variant of the Stroop color-word task: the picture-word interference task. Experiments 1 and 2 first compared the performance of the two patient groups and a control group in three tasks of increasing difficulty: picture-word detection, word reading, and picture naming. The results showed that (a) the two patient groups were significantly slower than the control group, but did not differ from each other, and (b) the difference in mean RT between the two patient groups and the control group did not increase with task difficulty. In Experiment 3, the subjects were required to name pictures while ignoring accompanying distractors: nonletter symbols, unrelated words or semantically related words. In this task, the right hemisphere patients showed a much larger semantic interference effect than both the left hemisphere patients and the control group. It is argued that this finding most probably reflects problems in visual selective attention with the right hemisphere patients.

Deficits in selective and sustained attention processes in early treated children with phenylketonuria--result of impaired frontal lobe functions?

Twenty normally intelligent children with early treated phenylketonuria (PKU) (IQ: mean = 101.4, SD = 10.0; age: mean = 10 years 11 months, SD = 1.3 years) and 20 healthy controls, matched for age, sex and IQ, were assessed for their selective (Stroop Task) and sustained attention (Test-d-2). Using positron emission tomography an activation of the frontal lobe during the Stroop task had previously been demonstrated. In addition to the Stroop Task and the Test-d-2, a short-term memory test as a "non-frontal-lobe-function-task" was administered to all subjects. Group comparisons demonstrated that PKU children had specific deficits in selective and sustained attention, which were significantly correlated with the concurrent serum phenylalanine concentration. The results give evidence that even dietary treated children with PKU were suffering from impaired attentional control mechanisms in spite of a normal IQ. The deficits might be the result of impaired frontal lobe functions.

Visual selective attention deficits in patients with Parkinson's disease: A quantitative model-based approach.

Visual selective attention deficits in patients with Parkinson's disease: A quantitative model-based approach.

Visual selective attention deficits in patients with Parkinson's disease: A quantitative model-based approach.

Visual selective attention deficits in patients with Parkinson's disease: A quantitative model-based approach.

Selective impairment of auditory attention following closed head injuries or right cerebrovascular accidents

According to clinical experience a frequent consequence of head injury is an impairment of auditory attention. We investigated the possibility that patients with either closed head injuries (CHI), or cerebrovascular accidents (CVA) of the right hemisphere, would be impaired by comparison to healthy subjects on an objective test of auditory attention. We used an experimental paradigm that consisted of four subtests which comprised strings of auditory digits heard either diotically or dichotically, at either fast or slow presentation rates, respectively. Omission and commission errors were scored for each subtest and combined by an index of errors. The results showed that CHI patients were significantly impaired initially by the fast stimulus presentation conditions, whereas CVA patients made significantly more errors on the dichotic subtests independent of the speed of presentation. It is proposed that the observed selective attention deficits of these patients were due to differential disruptions of an interactive cortical network incorporating prefrontal, anterior cingulate, and temporoparietal structures of the right hemisphere. Statistically significant correlations between the error index scores and subjectively perceived attention deficits suggested that the auditory attention task measured clinically relevant aspects of attention.

Time course of prefrontal lobe dysfunction in severely depressed in-patients: a longitudinal neuropsychological study.

The Stroop Colour-Word Test (SCWT) and the Verbal Fluency Test (VFT), two tests that have been suggested to be particularly sensitive to prefrontal dysfunction, were administered to 23 severely depressed in-patients. Both tests were impaired in patients at inclusion, but only verbal fluency normalized with successful treatment of depression. VFT impairment is consistent with the hypothesis of a left prefrontal cortex dysfunction in depression. Moreover, the persistence of an impaired performance on SCWT in patients at discharge suggests that a selective attention deficit may persist in patients beyond a clear clinical improvement.

Abnormal processing of irrelevant information in attention deficit hyperactivity disorder

The presence of a selective attention deficit in children with attention deficit hyperactivity disorder (ADHD) was investigated by administering a trial-by-trial version of the Stroop Color-Naming Task to children, aged 9–12, with ADHD ( n = 19) and age-matched normal control children ( n = 19). Performance was evaluated on both interference and facilitation components of the task. On the standard version of the task, with equal numbers of color words and neutral words, children with ADHD showed increased Stroop interference (prolongation of color-naming times by color-incongruent stimuli) but normal amounts of facilitation (speeding of color naming by color-congruent stimuli). This finding suggests that children with ADHD show increased disruption of color-naming performance by taskirrelevant information, probably secondary to decreased attentional control over the interference process. In contrast to findings of studies in adults, both groups of children failed to use an attentional strategy to reduce interference when they were administered blocks of trials that varied their expectancy for color word trials. This precluded a direct test of the diminished control hypothesis. There were no significant correlations between abnormal Stroop performance and impairment on the Continuous Performance Test or the Wisconsin Card Sorting Test or measures of IQ or reading performance. The implications of these findings for our understanding of information-processing deficits in children with ADHD and of the neurobiological underpinnings of these deficits are discussed.

Selective attention deficits in persons with autism: Preliminary evidence of an inefficient attentional lens.

Selective attention deficits in persons with autism: Preliminary evidence of an inefficient attentional lens.

An artificial neural network analogue of learning in autism

An artificial neural network is simulated that shares formal qualitative with the selective attention and generalization deficits seen in people with autism.The model is based on neruopathological studies which suggest that affected individuals have either too few or too many neuronal connections in various regions of the brain. In simulations where the model was taught to discriminate children with autism from children with mental retardation, having too few simulated neuronal connections led to relatively inferior discrimination of the two groups in a training set and, consequently, relatively inferior generalization of the discrimination to a novel test set. Too many connections produced excellent discrimination but inferior generalization because of overemphasis on details unique to the training set. It is concluded that, within the context of the current model, the neuropathological observations that have been described in the literature are sufficient to explain some of the unique pattern recognition and discrimination learning abilities seen in some people with autism as well as their problems with generalization and concept acquisition. The model generates testable hypothesis that have implications for understanding the pathogenesis, treatment, and phenomenology of autism.

Effects of the neuroleptic α-flupenthixol on latent inhibition in aversively- and appetitively-motivated paradigms: evidence for dopamine-reinforcer interactions

Three experiments examined the influence of the dopamine (DA) D1/D2 receptor antagonist alpha-flupenthixol on the latent inhibition (LI) effect. LI is a phenomenon which is manifest when non-reinforced pre-exposure to a stimulus retards subsequent conditioning to that stimulus, and has been proposed as an animal model of the selective attentional processes that are disrupted in acute schizophrenia. Experiment 1 extended previous findings that neuroleptics enhance the LI effect in conditioned suppression paradigms in rats to alpha-flupenthixol (0.23 mg/kg). Experiment 2 demonstrated that this enhancement of the LI effect was also seen in a parallel appetitively-motivated conditioning paradigm at the same dose. In both Experiment 1 and Experiment 2, the enhancement of the LI effect by alpha-flupenthixol appeared to be accompanied by a decrease in the impact of the reinforcer (be it appetitive or aversive). Experiment 3 investigated the possible role of the reinforcer in the effect of alpha-flupenthixol on the LI effect in the aversive, conditioned suppression paradigm by increasing the intensity of footshock in rats treated with alpha-flupenthixol. Increasing the intensity of the footshock completely abolished the enhancement of LI found following injection of alpha-flupenthixol, a result which could not be attributed to a floor effect. The results provide no support for interpretations of the influence of DA manipulations on the LI effect that draw parallels with deficits in selective attention observed in acute schizophrenia.

Sustained and selective attention in boys with attention deficit hyperactivity disorder

Attempted to claim the nature of the sustained and selective attention deficits implicated in attention deficit hyperactivity disorder (ADHD). Specifically, performance on the Continuous Performance Test (CPT; Sergeant & van der Meere, 1990) and speeded classification task was assessed for a group of7- to 12-year-old ADHD boys and their same-aged normal peers. Results of the CPT indicated that both perceptual sensitivity and omission errors increased over time for the ADHD boys to a greater degree than for the control boys, findings indicative of a sustained (attention deficit. Results of the speeded classification task indicated that ADHD children's performance was not as efficient as normal children. However, there was no evidence for a selective attention deficit. Findings are discussed in terns of a process-energy model of attention.