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PubMed1998

Cortical fMRI activation produced by attentive tracking of moving targets.

Attention can be used to keep track of moving items, particularly when there are multiple targets of interest that cannot all be followed with eye movements. Functional magnetic resonance imaging (fMRI) was used to investigate cortical regions involved in attentive tracking. Cortical flattening techniques facilitated within-subject comparisons of activation produced by attentive tracking, visual motion, discrete attention shifts, and eye movements. In the main task, subjects viewed a display of nine green "bouncing balls" and used attention to mentally track a subset of them while fixating. At the start of each attentive-tracking condition, several target balls (e.g., 3/9) turned red for 2 s and then reverted to green. Subjects then used attention to keep track of the previously indicated targets, which were otherwise indistinguishable from the nontargets. Attentive-tracking conditions alternated with passive viewing of the same display when no targets had been indicated. Subjects were pretested with an eye-movement monitor to ensure they could perform the task accurately while fixating. For seven subjects, functional activation was superimposed on each individual's cortically unfolded surface. Comparisons between attentive tracking and passive viewing revealed bilateral activation in parietal cortex (intraparietal sulcus, postcentral sulcus, superior parietal lobule, and precuneus), frontal cortex (frontal eye fields and precentral sulcus), and the MT complex (including motion-selective areas MT and MST). Attentional enhancement was absent in early visual areas and weak in the MT complex. However, in parietal and frontal areas, the signal change produced by the moving stimuli was more than doubled when items were tracked attentively. Comparisons between attentive tracking and attention shifting revealed essentially identical activation patterns that differed only in the magnitude of activation. This suggests that parietal cortex is involved not only in discrete shifts of attention between objects at different spatial locations but also in continuous "attentional pursuit" of moving objects. Attentive-tracking activation patterns were also similar, though not identical, to those produced by eye movements. Taken together, these results suggest that attentive tracking is mediated by a network of areas that includes parietal and frontal regions responsible for attention shifts and eye movements and the MT complex, thought to be responsible for motion perception. These results are consistent with theoretical models of attentive tracking as an attentional process that assigns spatial tags to targets and registers changes in their position, generating a high-level percept of apparent motion.

Adult↗
PubMed2006

Higher cortical deficits influence attentional processing in dementia with Lewy bodies, relative to patients with dementia of the Alzheimer's type and controls.

BACKGROUND: Attentional dysfunction is believed to be a prominent and distinguishing neuropsychological feature of dementia with Lewy bodies (DLB); yet, the specific nature of the attentional deficit and factors that can potentially influence attentional processing in DLB have not been fully defined. AIMS: To clarify the nature of the attentional deficit in early-stage DLB relative to patients with early-stage dementia of the Alzheimer's type (DAT) and elderly controls, and examine the effect of task complexity and type of cognitive load on attentional processing in DLB. METHODS: Attentional impairment and fluctuating attention were investigated in three groups of subjects--patients with clinical features of early probable DLB (n = 20), a group with early probable DAT (n = 19) and healthy elderly controls (n = 20)--using an experimental computerised reaction time paradigm. RESULTS: Patients with DLB showed greater attentional impairment and fluctuations in attention relative to patients with DAT and elderly controls. The attentional deficit was generalised in nature but increased in magnitude as greater demands were placed on attentional selectivity. Attentional deficits in DLB were most pronounced under task conditions that required more active recruitment of executive control and visuospatial cognitive processes. CONCLUSIONS: Attentional deficits in DLB are widespread and encompass all aspects of attentional function. Deficits in higher cortical function influence the degree of attentional impairment and fluctuating attention, suggesting that attentional processing in DLB is mediated by interacting cortical and subcortical mechanisms. These findings serve to clarify the nature of the attentional deficit in DLB and have potentially important ramifications for our understanding of the neurocognitive underpinnings of fluctuations.

Aged↗
PubMed2006

A presentation of attentional semantics.

The paper presents the two main assumptions of Attentional Semantics--(A) and (B), and its main aim (C). (A) Conscious experience is determined by attention: there cannot be consciousness without attention. Consciousness is explained as the product of attentional activity. Attentional activity can be performed thanks to a special kind of energy: nervous energy. This energy is supplied by the organ of attention. When we perform attentional activity, we use our nervous energy. This activity directly affects the organ of attention, causing a variation in the state of the nervous energy. This variation constitutes the phenomenal aspect of consciousness. (B) Words are tools to pilot attention. The meanings of words isolate, de-contextualize, "freeze" and classify in an articulated system the ever-changing and multiform stream of our conscious experiences. Each meaning is composed of the sequence of invariable elements that, independently of any individual occurrence of a given conscious experience, are responsible for the production of any instance of that conscious experience. The elements composing the meanings of words are attentional operations: each word conveys the condensed instructions on the attentional operations one has to perform if one wants to consciously experience what is expressed through and by it. (C) Attentional Semantics aims at finding the attentional instruction conveyed by the meanings of words. To achieve this goal, it tries: (1) to identify the sequence of the elementary conscious experiences that invariably accompany, and are prompted by, the use of the word being analyzed; (2) to describe these conscious experiences in terms of the attentional operations that are responsible for their production; and (3) to identify the unconscious and non-conscious operations that, directly or indirectly, serve either as the support that makes it possible for the attentional operations to take place, be completed, and occur in a certain way, or as the necessary complement that makes it possible to execute and implement the activities determined and triggered by the conscious experiences. The origins of Attentional Semantics are also presented, and the methodological problems researchers encounter when analyzing meanings in attentional terms are discussed. Finally, a brief comparison with the other kinds of semantics is made.

Attention↗
PubMed1999

Theta synchronization during sustained anticipatory attention in infants over the second half of the first year of life.

The neurophysiological basis of attention control has been investigated in infants during the second half of the first year of life. The marked improvement of voluntary control of attention and action is known to occur during this age period. EEG was registered in 60 infants aged 8-11 months under three experimental conditions: (1) attention to an object in the visual field (externally controlled attention or the 'baseline'); (2) anticipation of the person in the peek-a-boo game (internally controlled attention); and (3) attention to the 'reappeared' person in the peek-a-boo game ('control' condition). Spectral analysis of the data revealed sharp increase of the EEG theta activity (3.6-6.0 Hz) during internally controlled attention as compared to the 'baseline' and the 'control' conditions. The theta1 (3.6-4.8 Hz) increase was maximal at frontal electrode sites. The reactivity of the frontal theta1 during internally controlled attention differentiated subjects with different ability to maintain this type of attention. The theta2 (5.2-6.0 Hz) reactivity was maximal at right temporal electrode site and did not depend on the ability to maintain anticipatory attention. The data point to different functional significance of theta1 and theta2 rhythms in infants. It was suggested that the frontal theta1 synchronization in infants reflects activity of the anterior attention system subserving executive control of attention. The ability to maintain anticipatory attention increased, whereas the frontal theta1 synchronization decreased during the studied age period. There was the direct relationship between frontal theta1 synchronization and persistence of internally controlled attention in 8-month-olds. On the contrary, at 9 and 10 months, these variables were inversely-related. There was no link between theta1 reactivity and persistence of anticipatory attention in 11-month-olds. It was suggested that the age-dependant dynamic of the relationship between frontal theta1 reactivity and attention behaviour reflects the maturational shift in the functioning of anterior attention system. The shift leads to more economic and more efficient functioning of this system.

Age Factors↗
PubMed2003

Attentional ability in children with epilepsy.

Attention problems are frequently seen in children with epilepsy. This review gives an overview of the most used constructs of attention and analyzes the available evidence for attention deficits in children with epilepsy, the effects of epilepsy variables on attention, and the possible pathophysiological mechanisms involved. Children with benign childhood epilepsy with centrotemporal spikes (BCECTS) have sustained attention difficulties. Right (R)-sided interictal epileptiform activity in these children interferes with R hemisphere function including sustained attention. Children with BCECTS also show selective and divided attention deficits if they have epileptiform discharges during sleep. Children with complex partial seizures (CPSs) have sustained attention deficits but no difficulties in selective or divided attention. Cognitive difficulties in children with epilepsy arise more frequently the earlier the onset of the epilepsy, and this could influence attentional ability development. Antiepileptic drug treatment is unlikely to impair attention, but phenobarbital has behavioral side effects similar to those in attention deficit-hyperactivity disorder. Concerning pathophysiology, evidence indicates that interictal epileptiform activity in children with BCECTS impairs sustained attention and that ongoing epileptiform discharges during sleep may impair attention. Further systematic studies of different aspects of attention in children with epilepsy are needed. Attention in children with drug-resistant epilepsy has not been addressed, and prospective studies before and after epilepsy surgery could be a useful model to study the influence of seizures on attentional ability.

Attention↗
PubMed2001

Determinants and mechanisms of attentional modulation of neural processing.

This review contrasts the most-studied variety of attention, visuospatial attention, with several types of nonspatial visual attention. We: 1) discuss the manner in which spatial and nonspatial varieties of attention are experimentally defined, and the ecological validity of the paradigms in which they are studied, 2) review and compare differing effects of spatial and nonspatial attention on neural processing, 3) discuss the manner in which attention operates within the framework of an anatomical visual hierarchy, as well as 4) how attention relates to the temporal dynamics of visual processing, 5) describe cellular circuits and physiological processes that appear to be involved in attention effects, 6) discuss the relationship of attentional physiology to the perceptual and cognitive effects of attention, and 7) consider the strengths and limitations of several current models of selective attention. Throughout, we attempt to integrate the findings of monkey and human studies whenever possible. We have three main conclusions. First, two models, the Neural Specificity Model of Harter and colleagues and the Feature Similarity Gain Model of Treue and colleagues best incorporate findings in relation to both spatial and nonspatial varieties of attention. Significantly, these models explicitly note that the specific neuronal components used in attentional modulation of processing are flexible and determined by task demands. Second, current evidence also provides strong bases for deriving testable hypotheses about the specific brain mechanisms utilized by attention. Cellular processes, brain circuits and neurotransmitter components can and should be incorporated into our models of attention. Finally, it is increasingly evident that we can and should analyze temporal patterns of attentional modulation, both within and across brain areas. These patterns provide critical information on the dynamics of attention.

Animals↗
PubMed1999

Anxiety and directed attention in women awaiting breast cancer surgery.

PURPOSE/OBJECTIVES: To investigate the relationship between anxiety and directed attention (the ability to focus and concentrate) in women awaiting breast cancer surgery and the potential influence of age and extent of anticipated surgery (breast conservation versus mastectomy) on attentional functioning and anxiety. DESIGN: Descriptive, cross-sectional. SAMPLE AND SETTING: Convenience sample of 45 women newly diagnosed with localized breast cancer at a Midwestern university medical center. METHODS: Subjects were assessed approximately 11 days before surgery using objective measures of attention: Digit Span, the Symbol Digit Modalities Test, the Necker Cube Pattern Control Test, the Attentional Function Index (a subjective measure of effectiveness of attentional functioning), and the Tension-Anxiety subscale of the Profile of Mood States. MAIN RESEARCH VARIABLES: Capacity to direct attention, perceived attentional functioning, anxiety level, age, and extent of anticipated breast surgery. FINDINGS: Level of anxiety was related inversely (r = -0.63, p < 0.01) to perceptions of attentional functioning but not to performance on any objective measures of attention in the pretreatment period. No differences in anxiety level existed in regard to age or extent of anticipated surgery. However, older women (> or = 55 years) showed overall significantly lowered (p < 0.001) performance on the attentional measures than younger women. CONCLUSIONS: Preoperative anxiety is a clinically significant issue in women newly diagnosed with breast cancer regardless of age and extent of anticipated surgery. Higher anxiety requires use of attentional resources and initially may act to reduce perceptions of effectiveness in attentional functioning. Older women who have high anxiety combined with both subjective and objective decline in attentional functioning may be at particularly high risk for attentional fatigue. IMPLICATIONS FOR NURSING PRACTICE: Women newly diagnosed with breast cancer may experience not only increased anxiety and associated perceptions of decreased attentional functioning but also a subsequent depletion of attentional reserves as a result of the onset of attentional fatigue. Nurses can assess anxiety in women during the preoperative period and assist them in coping with the psychological and cognitive demands associated with this highly stressful period.

Adult↗
PubMed2004

Effects of methylphenidate on attention deficits after traumatic brain injury: a multidimensional, randomized, controlled trial.

OBJECTIVE: To evaluate the effects of methylphenidate on a variety of aspects of attention, ranging from laboratory-based impairment measures to caregiver ratings and work productivity, in individuals after traumatic brain injury. DESIGN: A total of 34 adults with moderate to severe traumatic brain injury and attention complaints in the postacute phase of recovery were enrolled in a 6-wk, double-blind, placebo-controlled, repeated crossover study of methylphenidate, administered in a dose of 0.3 mg/kg/dose, twice a day. A wide range of attentional measures was gathered weekly, including computerized and paper-and-pencil tests of attention, videotaped records of individual work in a distracting environment, real-time observational scoring of attentiveness in a classroom environment, and caregiver and clinician rating scales of attentiveness. Participants also attempted to guess their drug condition each week. Data from the first ten participants were used for pilot purposes, to develop attentional factors for composite scoring, and to identify attentional dimensions suggestive of a treatment effect for independent replication. The remaining 24 participants' results were used to confirm potential treatment effects seen in the pilot sample, using Wilcoxon's signed-ranks test on composite factor scores and individual variables. RESULTS: A total of 54 dependent variables were reduced to 13 composite factors and 13 remaining individual variables. Of the 13 attentional factors, five showed suggestive treatment effects in the pilot sample. Of these, three showed statistically significant treatment effects in the replication sample: speed of information processing (effect sizes, -0.06 to 0.48; P < 0.001), attentiveness during individual work tasks (effect sizes, 0.15-0.62; P = 0.01), and caregiver ratings of attention (effect sizes, 0.44-0.50; P = 0.01). Of the individual variables, four showed suggestive treatment effects in the pilot sample, but only one showed significant treatment effects in the replication sample: reaction time before errors in the Sustained Attention to Response Task (effect size, 0.20; P = 0.03). No treatment-related improvement was seen in divided attention, sustained attention, or susceptibility to distraction. None of the variables showed suggestive or definite negative treatment effects. Effect sizes for those performance measures positively affected by methylphenidate were in the small to medium range and included both impairment and activity level measures. Improvements in processing speed did not seem to come at the expense of accuracy. CONCLUSIONS: Methylphenidate, at 0.3 mg/kg/dose, given twice a day to individuals with attentional complaints after traumatic brain injury, seems to have clinically significant positive effects on speed of processing, caregiver ratings of attention, and some aspects of on-task behavior in naturalistic tasks. Further research is needed to identify the optimal dose and to extend these findings to less carefully selected individuals.

Adult↗
PubMed2001

Combined visual attention and finger movement effects on human brain representations.

Sensory and motor systems interact in complex ways; visual attention modifies behavior, neural encoding, and brain activation; and dividing attention with simultaneous tasks may impede performance while producing specific brain activation patterns. We hypothesized that combining voluntary movement with visual attention would yield unique brain representations differing from those occurring for movement or visual attention alone. Hemodynamic signals in humans were obtained with functional magnetic resonance imaging (MRI) while participants performed one of four tasks that required only a repetitive finger movement, only attending to the color of a visual stimulus, simultaneous finger movement and visual attention, or no movement and no visual attention. The movement-alone task yielded brain activation in structures commonly engaged during voluntary movement, including the primary motor cortex, supplementary motor area, and cerebellum. Visual attention alone resulted in sparse cerebral cortical and substantial bilateral cerebellar activation. Simultaneous performance of visual attention and finger movements yielded widespread cerebral cortical, cerebellar, and other subcortical activation, in many of the same sites activated for the movement or attention tasks. However, the movement-related plus attention-related activation extended beyond the movement-alone or attention-alone activation sites, indicating a novel activation pattern related to the combined performance of attention and movement. Additionally, the conjoint effects of visual attention and movement upon brain activation were probably not simple gain effects, since we found activation-related interactions in the left superior parietal lobule, the right fusiform gyrus, and left insula, indicating a potent combinatory role for visual attention and movement for activation patterns in the human brain. In conclusion, performing visual attention and movement tasks simultaneously, even though the tasks had no specific interrelationship, resulted in novel activation patterns not predicted by performing movements or visual attention alone.

Adult↗
PubMed2004

Age-dependent neuropsychological deficits and effects of methylphenidate in children with attention-deficit/hyperactivity disorder: a comparison of pre- and grade-school children.

OBJECTIVE: Pre-school and grade-school children diagnosed with attention-deficit/hyperactivity disorder (ADHD) were compared in their performance on computerized attention tasks. Depending on the nature of the specified attention deficit, subjects were assigned to groups of cognitive subtypes. The effects of methylphenidate (MPH) were analysed depending on age and cognitive subtype. METHOD: The preschool group comprised 45 children aged 5-7 years; the grade-school group comprised 54 children aged 8-12 years. Children were tested on placebo and on MPH (mean dose: 0.25-0.3 mg/kg body weight) employing tasks of alertness, sustained attention, focused attention, divided attention, and a cognitive conflict task. RESULTS: Both groups showed measurable attention deficits. While preschoolers were especially impaired in supervisory attention functions, grade-schoolers most frequently exhibited deficits in attention intensity and selectivity. Positive MPH effects were documented for sustained attention in both age-groups. Analysis of MPH effects in dependence on the type of attention impairment (supervisory functions vs. attention intensity/selectivity) revealed a positive relation between deficits in a specific attention domain and MPH effects. CONCLUSIONS: Age-dependent differences in attention dysfunctions might be due to brain maturational processes. Performance on computerized attention tasks was particularly improved by MPH in children with objectified attention deficits suggesting that neuropsychological diagnostics can be useful to optimise treatment outcome.

Age Factors↗
PubMed2003

Are there sub-types of attentional deficits in patients with persisting post-concussive symptoms? A cluster analytical study.

AIM: The present study aimed to examine attentional deficits in patients with persisting post-concussive symptoms using a multi-componential framework of attention. DESIGN: A cross-sectional investigation using standardized tests and questionnaires of attention including 92 patients. METHOD: Participants were administered comprehensive measures of attention assessing sustained attention (Sustained Attention Response to Task, Backward Digit Span), selective attention (Stroop Word-Colour Test, Colour Trails Test), divided attention (Paced Auditory Serial Addition Test, Symbol Digit Modalities Test), and attentional control (Tower of Hanoi, Six Elements Test). Ecological tests of attention were used to validate the cluster solution. MAIN OUTCOME: Three clusters of patients with different combinations of attentional deficits were identified. They were 'mild sustained attentional deficits', 'selective and divided attentional deficits', and 'general attentional deficit'. A MANOVA indicated that these three clusters were statistically and clinically different from one another in terms of different attentional components proposed. CONCLUSION: This study provides preliminary evidence suggesting that sub-types of attentional impairments exit in patients with post-concussive symptoms.

Adult↗
PubMed1995

Asymmetries in the covert orienting of visual spatial attention to spatial and non-spatial cues in Alzheimer's disease.

The ability to direct covert visual spatial attention to the left (LVF) and right visual field (RVF) was examined in 15 patients with mild to moderate Alzheimer's disease and 15 age- and education-matched controls using the covert orienting of visual spatial attention task (COVAT) modified to include both spatial and non-spatial cues. Subjects responded with a button press when they detected a target at a location 8 degrees to either the left or right of fixation. On 70% of trials a spatial cue was flashed at the target location before the target appeared. On 15% of trials the spatial cue was flashed at the location contralateral to where it would appear and on the remaining 15% of trials non-spatial diffuse cue preceded targets. The cue to target interval (CTI) varied between 150 and 550 ms. Mean reaction times for each cuetype in the RVF and LVF were calculated. Compared with controls, the percentage of trials excluded because of very slow reaction times was significantly greater in the Alzheimer's disease group for the 550 ms CTI. Analysis of the symmetry of reaction times to LVF and RVF targets for the 150 ms CTI enabled us to classify Alzheimer's disease subjects into three subgroups based on the hemifield of abnormally slow attentional biases. The first subgroup showed a significant slowing of reaction time to all LVF targets, the second showed a significant slowing of reaction time to all RVF targets and the third showed a significant slowing of reaction time to both LVF and RVF targets. Patients with Alzheimer's disease who showed an abnormal attentional bias performed significantly better on neuropsychological tests of memory, language and executive function than Alzheimer's disease patients with no attentional bias. Eight of the Alzheimer's disease subjects were assessed serially on at least six occasions over a 12-month period. The initial classification of abnormal attentional bias or no attentional bias was reliable for seven Alzheimer's disease subjects. One Alzheimer's disease subject, initially classified as having a slowed rightward attentional bias, in subsequent testing over the 12-month period was more consistent with symmetrical COVAT performance. Control subjects showed no attentional biases over the 12-month period and the magnitude of asymmetric attentional slowing over the 12-month period was significantly more variable in individual Alzheimer's disease subjects than in controls. The presence of subgroups of patients with Alzheimer's disease with qualitatively different COVAT performance indicates a large between-subject variability in attentional deficits in Alzheimer's disease. The presence of asymmetric attentional slowing and milder neuropsychological deficits in a subgroup of patients with Alzheimer's disease suggests that in these patients there is functional impairment of attentional areas in only one hemisphere rather than an asymmetric impairment of both hemispheres and that the neurodegenerative disease process may have been less advanced or in an earlier stage than that present in Alzheimer's disease patients with symmetric attentional performance and bilateral COVAT impairment. The preservation of asymmetric attentional slowing over time, together with the increased intra-subject variability in the magnitude of these asymmetries, suggests that asymmetrical COVAT performance represents a reliable reflection of underlying hemispheric function in Alzheimer's disease, although designation of asymmetrical attentional biases should be made on the basis of two or more sequential testing sessions.

Aged↗
PubMed2006

The impact of attention deficit hyperactivity disorders on brainstem dysfunction in nocturnal enuresis.

PURPOSE: In a specialized university setting the prevalence of attention deficit hyperactivity disorder in general and particularly the inattentive subtype attention deficit hyperactivity disorder of the predominantly inattentive subtype is highly increased. We replicated previous research findings that enuresis is associated with a brainstem deficit and investigated the impact of attention deficit hyperactivity disorder on this brainstem deficit in enuresis. MATERIALS AND METHODS: Electromyography recorded startle eye blink modification with and without attentional modulation was used to measure brainstem functioning in 158 children between 6 and 12 years old. Performance in 3 enuresis groups, including children with enuresis, enuresis plus attention deficit hyperactivity disorder of the predominantly inattentive subtype and enuresis plus attention deficit hyperactivity disorder combined, respectively, was compared with that in normally developing controls and in children with attention deficit hyperactivity disorder subtypes without enuresis. RESULTS: In an automatic attentional task the enuresis groups showed decreased brainstem inhibition compared to that in the control and attention deficit hyperactivity disorder groups (p <0.006). In a controlled attentional task children with and without enuresis who had attention deficit hyperactivity disorder of the predominantly inattentive subtype were unable to show attentional modulation in all age groups (p <0.02). CONCLUSIONS: Startle eye blink modification research reveals a brainstem inhibition deficit in children with enuresis, which could explain why they are unable to remain dry at night. When additional attention is allocated to specific trials in the task, children with attention deficit hyperactivity disorder of the predominantly inattentive subtype fail to optimize sensory gating. With respect to enuresis, this could result in an identification problem of bladder signals, leading to an inadequate or absent arousal effect in attention deficit hyperactivity disorder of the predominantly inattentive subtype.

Attention Deficit Disorder with Hyperactivity↗
PubMed1999

Attention and executive deficits in Alzheimer's disease. A critical review.

In this review we summarize the progress that has been made in the research on attentional and executive deficits in Alzheimer's disease. Like memory, attention is now recognized as consisting of subtypes that differ in their function and anatomical basis. We base our review upon a classification of three subtypes of attention: selective, sustained and divided. This model derives from lesion studies, animal electrophysiological recordings and functional imaging. We examine how these subcomponents of attention can be reconciled with neuropsychological models of attentional control, particularly the Supervisory Attentional System and the Central Executive System of Shallice and Baddeley, respectively. We also discuss the relationship of attention to the concept of executive function. Current evidence suggests that after an initial amnesic stage in Alzheimer's disease, attention is the first non-memory domain to be affected, before deficits in language and visuospatial functions. This is consistent with the possibility that difficulties with activities of daily living, which occur in even mildly demented patients, may be related to attentional deficits. It appears that divided attention and aspects of selective attention, such as set-shifting and response selection, are particularly vulnerable while sustained attention is relatively preserved in the early stages. The phenomenon of cognitive slowing in Alzheimer's disease and normal ageing emphasizes the need to discriminate quantitative changes in attention dysfunction from qualitative changes which may be specifically related to the disease process. The neuropathological basis of these attentional deficits remains unsettled, with two competing hypotheses: spread of pathology from the medial temporal to basal forebrain structures versus corticocortical tract disconnection. Finally we discuss the difficulties of comparing evidence across studies and look at the implications for the design of future studies and future directions that may be fruitful in the research on attention in Alzheimer's disease.

Animals↗
PubMed1998

4 T-fMRI study of nonspatial shifting of selective attention: cerebellar and parietal contributions.

Regional blood oxygenation in the cerebellum and posterior cerebral cortices was monitored with functional magnetic resonance imaging (fMRI) at four Tesla while 16 normal subjects performed three tasks with identical visual stimulation: fixation; attention focused upon either stimulus shape or color and sustained during blocks of trials (sustained attention); and rapid, serial shifts in attention between stimulus shape or color within blocks of trials (shifting attention). The stimuli were displayed centrally for 100 ms followed by a central fixation mark for 900 ms. Each stimulus was either a circle or a square displayed in either red or green. Attention shifting required switching between color and shape information after each target detection and occurred on average once every three seconds. Subjects pressed a response key upon detecting the target; reaction time and response accuracy were recorded. Two protocols for T2*-weighted echo-planar imaging were optimized, one with a surface coil for the cerebellum alone and the other with a volume coil for imaging both cerebellum and posterior brain structures (parietal, occipital, and part of temporal cortices). Because fMRI of the cerebellum is particularly susceptible to cardiac and respiratory fluctuations, novel techniques were applied to isolate brain activation signals from physiological noise. Functional activation maps were generated for contrasts of 1) sustained attention to color minus fixation; 2) sustained attention to shape minus fixation; and 3) shifting attention minus sustained attention (to color and shape; i.e., summed across blocks of trials). Consistent with the ease of these tasks, subjects performed with >80% accuracy during both sustained attention and shifting attention. Analysis of variance did not show significant differences in false alarms or true hits across either attentional condition. A subgroup of subjects whose performance data were recorded during ten minutes of continuous practice did not show significant changes over time. Both contrasts between the conditions of sustained attention to color or to shape as compared with the fixation condition showed significant bilateral activation in occipital and inferior temporal regions (Brodmann areas 18, 19, and 37). The anterior medial cerebellum was also significantly activated ipsilateral to the finger used for responding. The principal comparison of interest, the contrast between the condition of shifting attention and the condition of sustained attention produced significant and reproducible activation: lateral cerebellar hemisphere (ansiform lobule: Crus I Anterior and Crus I Posterior; left Crus I Posterior); cerebellar folium; posterior superior parietal lobule (R and L); and cuneus and precuneus (R and L).

Adult↗
PubMedDate not supplied

[Influence of attention on an auditory-verbal learning test in schizophrenic patients].

Schizophrenic patients are known to feature alterations in their cognitive performances, principally in executive functions, attention and memory. In this last domain, studies have shown a relatively severe and global deficit, which can be assessed in chronic and first episode patients. It seems that the memory dysfunction is independent of age and intellectual level, but does correlate with negative psychopathology and global functioning. In the study of memory dysfunction, attentional capacities, information processing and symptomatology have to be considered as determining factors. It has been shown that patients with schizophrenia perform poorly in selective attention tasks and that this deficit may interfere with learning. In the same way, the slowing of information processing contributes to a superficial and incomplete learning. The impact of symptomatology has also to be considered, as negative and depressive symptoms are linked to mnesic performances. The majority of studies bearing on working memory and schizophrenia show an alteration of performances, but studies on long term memory are more equivocal. Procedural memory seems to be preserved, while declarative memory is impaired. These results support the hypothesis that in schizophrenia, memory processes that are consciously controlled are impaired, contrary to implicit learning which may be intact. Nevertheless, studies bearing on semantic memory and episodic memory show controversial results. Still, many authors argue that schizophrenic patients have difficulties in recalling learned material, specially when a delay or a interfering task are introduced in the test. Besides, the schizophrenic subjects do not use the semantic properties of the words, as well as the control subjects, when they have to learn a words list for example. The main goal of the present study was to examine the auditory-verbal learning capacities of 31 schizophrenic patients (20 men and 11 women, 19-56 years old), compared to 27 healthy subjects (11 men and 16 women, 23-56 years old). All subjects received an evaluation including the Rey Auditory-Verbal Learning Test, used to study the progressive acquisition of 15 disyllabic words which are successively orally presented five times to the subject. About forty-five minutes after the last of the five immediate recalls, the delayed recall is assessed and a percentage of retention is also calculated. Visual reasoning and attention capacities were studied with the Progressive Matrix and the d2 encumbrance test respectively. Global psychiatric symptomatology of the patients group was assessed with the Brief Psychiatric Rating Scale. Considering the literature existing on the verbal learning capacities of schizophrenic patients, it was expected that the patients would perform poorly and learn slower than controls. The initial learning of the material, which is a critical stage for schizophrenic patients, was studied with particular attention as well as the effect of the introduction of a delay upon the recall of the words list. A secondary objective of the study was to investigate the role of visual reasoning and attention upon auditory-verbal learning process. According to published studies, it is expected that schizophrenic patients manifest some impairment in the domains of visual reasoning and attention. The question is to know whether it alters performances in the auditory-verbal learning test or not. Finally, the links between clinical characteristics of the patients, like age and illness duration, and their learning performances were explored. Statistical analysis included first a descriptive analysis of data to examine differences between the two groups. Second, ANCOVAs were used in order to control the respective impact of educational level, attention capacities and verbal reasoning capacities upon learning performances. Third, Spearman's correlations were used to detect links between clinical characteristics of the patients and learning performances. The comparisons between patients and controls confirmed that schizophrenic patients scored less in the attentional and visual reasoning tasks. They also featured a lower educational level compared to the healthy subjects. In the auditory-verbal learning test, the patients showed altered performances in the five recalls, as well as in the delayed recall and for the retention percentage. In order to control the impact of educational level, attentional and visual reasoning capacities, these parameters were introduced in the statistical analyses. Educational level did not influence memory alterations in the schizophrenic group. However, attention and, to a lesser extend, visual reasoning had an impact on the comparison of memory scores: when controlling attention, almost no significant group effect remained. Finally, the exploratory analyses of links between clinical characteristics and memory only revealed the presence of a significant negative correlation between illness duration and learning performances. Thus, the analyze of data showed that schizophrenic subjects featured poor performances in the domains of attention, verbal reasoning and auditory-verbal memory. Further analyses taking into account group differences on attention suggest that the impairment featured by schizophrenic patients in the domain of verbal memory strongly relies on an attentional deficit. These results are discussed according to the existing literature and methodological limitations. Clinical implications are also discussed.

Adult↗
PubMedDate not supplied

[The theta rhythm of the infant EEG and the development of the mechanisms of voluntary control of attention in the 2nd half of the first year of life].

The neurophysiological basis of attention control was studied in infants at the second half-year of life, i.e. in the period when the capability for voluntary control over behavior fundamentally improves. EEG was recorded in 60 infants aed 8-11 months in three experimental conditions: 1) attention to an object in the visual field (externally controlled attention, or the baseline state), 2) anticipation of a person in the peek-a-boo game (internally controlled attention), 3) attention to the reappeared person in the peek-a-boo game (control condition). The spectral analysis of the EEG data revealed a sharp increase in the EEG theta (3.6-6.0 Hz) during internally controlled attention as compared to the baseline and control conditions. The theta1 (3.6-4.8 Hz) increase was maximal in the frontal derivations. The reactivity of the frontal theta1 during internally controlled attention discriminated infants with different abilities to maintain this type of attention. The reactivity of the theta2 (5.2-6.0 Hz) was maximal in the right temporal derivation (T6) and did not depend on stability of the anticipatory attention. The findings point to different functional significance of the theta1 and theta2 rhythms in infants. It is suggested that synchronization of the frontal theta1 rhythm in infants reflects the activity of the anterior attention system which realizes the executive attention control. The ability to maintain anticipatory attention increased with age, whereas the frontal theta1 synchronization decreased and totally disappeared at the age of 11 months. At the age of 8 months there was a positive correlation between the frontal theta1 synchronization and behavioral index of stability of the internally controlled attention. On the contrary, this correlation was negative at the age of 9 and 10 months. It is suggested that the age-dependent dynamics of the relationship between the frontal theta1 reactivity and attention reflects a leap in maturation of the anterior attention system resulting in its more economic and efficient functioning.

Aging↗
PubMed2003

Startle magnitude and prepulse inhibition: effects of alcohol and attention.

BACKGROUND: Previous studies of the effects of attention on prepulse inhibition (PPI) have not accounted for the effects of attention on control (i.e. pulse alone) trials. In addition, there have been no studies of the effects of alcohol on the attentional modulation of PPI, even though alcohol putatively influences attentional mechanisms. The objective of the present study was to examine the effects of alcohol on the attentional modulation of PPI, using an experimental paradigm that controlled for the effects of attention on control trials. METHODS: Participants completed two experimental sessions spaced 1 week apart and consumed either three alcoholic drinks (target BAL=0.06) or three non-alcoholic drinks. Participants were exposed to a series of prepulse and pulse alone stimuli and were instructed to either listen or ignore prior to each stimulus. RESULTS: Repeated measures ANOVAs suggested that attention increased PPI and startle magnitude on pulse alone control trials. Alcohol decreased both startle magnitude and PPI. There was no significant interaction between attention and alcohol. CONCLUSIONS: These findings suggest that both startle magnitude and PPI are increased by attention and that failure to control for the effects of attention on control trials may result in an underestimation of the effect of attention on PPI. Furthermore, the effect of alcohol on attention does not appear to generalize to the voluntary attentional processes involved in the attentional modulation of PPI.

Adult↗