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Treatment of attention deficits in neurological disorders.

PURPOSE OF REVIEW: Recent work has revealed the impact of deficits of attention on patients with neurological disorders. Here we discuss therapeutic interventions that have been used across a range of conditions, highlighting common themes both in the nature of the attention deficits and the strategies employed to treat them. RECENT FINDINGS: Cholinesterase inhibitors improve attention, as well as memory, in several conditions including cortical Lewy body disease, Parkinson's disease dementia, traumatic brain injury and Alzheimer's disease. Recent studies suggest that cholinergic stimulation may boost attention further if more specific nicotinic cholinergic agonists are used, or if cholinesterase inhibitors are combined with other agents. Monoaminergic drugs have been shown to improve attention in traumatic brain injury, attention-deficit hyperactivity disorder and hemispatial neglect following right-hemisphere stroke. New compounds targeting other neurotransmitter systems are currently being tested, while several types of behavioural intervention have shown promise, particularly in stroke patients. SUMMARY: Pharmacological and behavioural interventions can improve attention in neurological patients. In the future, optimum therapy may depend on careful delineation of the components of attention that are impaired as well as assessment of the potential for surviving brain regions to compensate for attention deficits.

Attention↗

Cross-modal links in spatial attention.

A great deal is now known about the effects of spatial attention within individual sensory modalities, especially for vision and audition. However, there has been little previous study of possible cross-modal links in attention. Here, we review recent findings from our own experiments on this topic, which reveal extensive spatial links between the modalities. An irrelevant but salient event presented within touch, audition, or vision, can attract covert spatial attention in the other modalities (with the one exception that visual events do not attract auditory attention when saccades are prevented). By shifting receptors in one modality relative to another, the spatial coordinates of these cross-modal interactions can be examined. For instance, when a hand is placed in a new position, stimulation of it now draws visual attention to a correspondingly different location, although some aspects of attention do not spatially remap in this way. Cross-modal links are also evident in voluntary shifts of attention. When a person strongly expects a target in one modality (e.g. audition) to appear in a particular location, their judgements improve at that location not only for the expected modality but also for other modalities (e.g. vision), even if events in the latter modality are somewhat more likely elsewhere. Finally, some of our experiments suggest that information from different sensory modalities may be integrated preattentively, to produce the multimodal internal spatial representations in which attention can be directed. Such preattentive cross-modal integration can, in some cases, produce helpful illusions that increase the efficiency of selective attention in complex scenes.

Attention↗

Voluntary spatial attention has different effects on voluntary and reflexive saccades.

Although numerous studies have investigated the relationship between saccadic eye movements and spatial attention, one fundamental issue remains controversial. Some studies have suggested that spatial attention facilitates saccades, whereas others have claimed that eye movements are actually inhibited when spatial attention is engaged. However, these discrepancies may be because previous research has neglected to separate and specify the effects of attention for two distinct types of saccades, namely reflexive (stimulus-directed) and voluntary (antisaccades). The present study explored the effects of voluntary spatial attention on both voluntary and reflexive saccades. Results indicate that voluntary spatial attention has different effects on the two types of saccades. Antisaccades were always greatly facilitated following the engagement of spatial attention by symbolic cues (arrows) informing the subject where the upcoming saccade should be directed. Reflexive saccades showed little or no cueing effects and exhibited significant facilitation only when these cues were randomly intermixed with uncued trials. In addition, the present study tested the effects of fixation condition (gap, step, and overlap) on attentional modulation. Cueing effects did not vary due to fixation condition. Thus, voluntary spatial attention consistently showed different effects on voluntary and reflexive saccades, and there was no evidence in these studies that voluntary cues inhibit reflexive saccades, even in a gap paradigm.

Adolescent↗

Trunk orientation induces neglect-like lateral biases in covert attention.

The purpose of this study was to resolve a paradox in the literature on the effects of body orientation on spatial attention. Neuropsychological studies have found that real or simulated trunk rotation relieves contralesional inattention in patients with unilateral neglect, suggesting that trunk orientation affects how attention is allocated to space. However in two previous studies, trunk orientation did not affect spatial attention in other populations. In this study we investigated the effects of trunk orientation on the performance of a covert attention task by neurologically intact adults. The covert attention task allowed the evaluation of the effects of trunk orientation on both the allocation of attention to space and the ability to shift that attention to new locations. As in previous research, trunk orientation did not affect participants' response times (RTs) to validly cued targets. However rotating participants' trunks to the left increased their RTs to invalidly cued targets on the right and decreased their RTs to invalidly cued targets on the left. These results indicate that trunk orientation induces directional biases in the ability to shift attention. Thus, for intact participants, trunk rotation created lateral biases in the covert attention task similar to those seen in neglect patients.

Adult↗

Exogenous spatial attention influences figure-ground assignment.

In a hierarchical stage account of vision, figure-ground assignment is thought to be completed before the operation of focal spatial attention. Results of previous studies have supported this account by showing that unpredictive, exogenous spatial precues do not influence figure-ground assignment, although voluntary attention can influence figure-ground assignment. However, in these studies, attention was not summoned directly to a region in a figure-ground display. In three experiments, we addressed the relationship between figure-ground assignment and visuospatial attention. In Experiment 1, we replicated the finding that exogenous precues do not influence figure-ground assignment when they direct attention outside of a figure-ground stimulus. In Experiment 2, we demonstrated that exogenous attention can influence figure-ground assignment if it is directed to one of the regions in a figure-ground stimulus. In Experiment 3, we demonstrated that exogenous attention can influence figure-ground assignment in displays that contain a Gestalt figure-ground cue; this result suggests that figure-ground processes are not entirely completed prior to the operation of focal spatial attention. Exogenous spatial attention acts as a cue for figure-ground assignment and can affect the outcome of figure-ground processes.

Attention↗

Associations of motor co-ordination and attention with motor-perceptual development in 3-year-old preterm and full-term children who needed neonatal intensive care.

BACKGROUND: Children who have needed neonatal intensive care (NIC) are considered to be at risk for deficits such as developmental co-ordination disorder and attention-deficit/hyperactivity disorder. By assessing motor-perceptual development, motor co-ordination and attention already at 3 years of age, it might be possible to identify such deficits earlier than they are today. AIM: To investigate the motor-perceptual development in a group of 202 NIC children but had no major impairments, to describe associations of deficits in co-ordination and attention with motor-perceptual delays, and to estimate the prevalence of NIC children with combined deficits together with a motor-perceptual delay. METHOD: Co-ordination and attention in children born very preterm (n = 57), moderately preterm (n = 75) and full-term (n = 70) were observed according to a model for Combined Assessment of Motor Performance and Behaviour while they were assessed using a developmental scale, Motor-Perceptual Development, 0-7 years, MPU. RESULTS: In two out of 14 MPU areas, a larger proportion of very preterm than of moderately preterm and full-term children had marked developmental delay. Overall, the proportion of NIC children having a motor-perceptual delay increased with increasing incoordination and especially increasing lack of attention. Twenty-one (11%) of the NIC children had different motor-perceptual delays combined with pronounced incoordination and pronounced lack of attention. CONCLUSION: Deficits in co-ordination and attention were associated with motor-perceptual delays in areas important for daily living and development of academic skills. Therefore, to find children at risk for developmental co-ordination disorder and attention-deficit/hyperactivity disorder, assessments of co-ordination and attention should be added to assessments of motor-perceptual development in 3-year-old NIC children.

Attention↗

Effects of attention and arousal on early responses in striate cortex.

Humans employ attention to facilitate perception of relevant stimuli. Visual attention can bias the selection of a location in the visual field, a whole visual object or any visual feature of an object. Attention draws on both current behavioral goals and/or the saliency of physical attributes of a stimulus, and it influences activity of different brain regions at different latencies. Attentional effect in the striate and extrastriate cortices has been the subject of intense research interest in many recent studies. The consensus emerging from them places the first attentional effects in extrastriate areas, which in turn modulate activity of V1 at later latencies. In this view attention influences activity in striate cortex some 150 ms after stimulus onset. Here we use magnetoencephalography to compare brain responses to foveally presented identical stimuli under the conditions of passive viewing, when the stimuli are irrelevant to the subject and under an active GO/NOGO task, when the stimuli are cues instructing the subject to make or inhibit movement of his/her left or right index finger. The earliest striate activity was identified 40-45 ms after stimulus onset, and it was identical in passive and active conditions. Later striate response starting at about 70 ms and reaching a peak at about 100 ms showed a strong attentional modulation. Even before the striate cortex, activity of the right inferior parietal lobule was modulated by attention, suggesting this region as a candidate for mediating attentional signals to the striate cortex.

Adult↗

The role of joint attention in the development of infants' play with objects.

Year-old infants' play was scored within and outside joint attention with mother and when alone for four levels of maturity: stereotypical, inappropriate relational, appropriate relational, functional. Maternal sensitivity within joint attention was rated on two measures: following infants' interests and scaffolding infants' activities. Infants' play was more advanced with mother than when alone. With mother, infants had more functional and appropriate relational play within joint attention and more stereotypical play outside joint attention, indicating more advanced play within joint attention and more immature play outside joint attention. Functional play within joint attention, but not outside joint attention, correlated with functional play when alone. Mothers' ability to scaffold infants' activities within joint attention may be particularly facilitative to infants' advanced play.

Adult↗

Sensitivity to triadic attention in early infancy.

In Study 1, 54 3-, 6- and 9-month-old infants interacted with an adult stranger who engaged in a face-to-face (dyadic) exchange. Dyadic interaction was halted when the adult turned away to look at an object. In a Joint Attention condition, the adult alternated visual attention between the infant and the object, and in a Look Away condition she looked away at the object only. Infants gazed and smiled more in the Joint Attention condition compared to in the Look Away condition. Infants' gazing to the target object interacted with age and condition. In Study 2, 37 3-, 6- and 9-month old infants interacted with an adult who coordinated visual attention and affect, affect only, visual attention only, or ignored the infant. Infants gazed reliably more at E when she coordinated both affect and attention and smiled reliably more when the adult coordinated affect and attention or attention only. The findings show a sensitivity to triadic attention by 3 months of age.

Adult↗

Visual attention in deaf and hearing infants: the role of auditory cues.

BACKGROUND: Successful communication with profoundly deaf children is heavily dependent on visual attention. Previous research has shown that mothers of deaf children--notably those who are deaf themselves--use a variety of strategies to gain their children's attention. This study compares patterns of visual attention in deaf and hearing children to determine how they are affected by the absence of auditory cues, especially when looking to the mother's face. METHOD: The visual attention of 18-month-old infants to their mothers was examined in two groups of deaf children (6 with deaf mothers and 6 with hearing mothers) and two of hearing children (6 with deaf mothers and 8 with hearing mothers). Dyads were observed in free play and 10 minutes of videorecorded interaction was analysed. All looks to the mother were classified as Spontaneous, Responsive (Child turns in response to something done by mother) or Elicited (Mother actively seeks to gain child's attention by, e.g., tapping or waving). The kind of event that attracted the child's attention in Responsive and Elicited episodes was also determined (e.g., object movement, speech, physical contact), as was the focus of the child's attention (e.g., mother's face, mother's body). RESULTS: Responsive looks to the mother were the most frequent for all groups but on only about 25% of occasions were they directed to her face. Elicited and spontaneous looks occurred less often but were frequently directed to the mother's face. Spontaneous looking occurred in all groups but elicited looking very seldom occurred in Hearing-Hearing dyads. Overall, there were fewer looks to the mother in the two groups where mother and child had congruent hearing status, although the proportion of the looks to the mother's face was similar. CONCLUSIONS: Both spontaneous and elicited looks are likely to involve attention to the mother's face. However, while active elicitation of attention is an important part of successful communication with young deaf children, this does not appear necessary for typically developing hearing children who turn to look at their mother's face on hearing her voice. The implications of these findings for differences in the dynamics of communication with young deaf and hearing children are discussed.

Analysis of Variance↗

Joint attention and symbolic play in young children with autism: a randomized controlled intervention study.

BACKGROUND: Delays and deficits in joint attention and symbolic play constitute two important developmental problems in young children with autism. These areas of deficit have been well studied in autism but have rarely been the focus of treatment efforts (see Kasari, Freeman, & Paparella, 2001). In this study, we examine the efficacy of targeted interventions of joint attention and symbolic play. METHODS: Participants were 58 children with autism aged 3 and 4 years (46 boys). Children were randomized to a joint attention intervention, a symbolic play intervention, or control group. Interventions were conducted 30 minutes daily for 5-6 weeks. Both structured assessments of joint attention and play skills and mother-child interactions were collected pre and post intervention by independent assessors. RESULTS: Results indicate that both intervention groups improved significantly over the control group on certain behaviors. Children in the joint attention intervention initiated significantly more showing and responsiveness to joint attention on the structured joint attention assessment and more child-initiated joint attention in the mother-child interaction. The children in the play group showed more diverse types of symbolic play in interaction with their mothers and higher play levels on both the play assessment and in interaction with their mothers. CONCLUSIONS: This randomized controlled trial provides promising data on the specificity and generalizability of joint attention and play interventions for young children with autism. Future studies need to examine the long-term effects of these early interventions on children's development.

Adult↗

Human brainstem auditory evoked potentials fail to provide evidence of efferent modulation of auditory input during attentional tasks.

Efferent modulation of auditory input at the level of the brainstem during attention-demanding tasks has been described in animal studies. Attempts to demonstrate these effects in humans have produced conflicting results, however. These studies are reviewed with particular reference to those animal experiments that have demonstrated peripheral effects. The human experiments have used a number of attentional conditions which have not been related either to each other or to the successful animal work. Two of the most important conditions in these studies--the use of an intermodal attention task and the manipulation of attentional states--have been examined rarely or not at all in the human research. Two experiments were conducted to investigate the possibility of attention-related effects on the human brainstem auditory evoked potential. These experiments were designed to examine experimental conditions common to both successful and unsuccessful attempts to demonstrate attention-driven efferent modulation at the periphery in humans. Also examined was the gradation of attention effects on efferent modulation demonstrated in animals but never studied in humans. No significant changes in either the latency or the amplitude of the brainstem auditory evoked potential were found in any of the attention-demanding conditions. Results are discussed in terms of psychophysiological theories of attention. Also, the interpretation of the most recent animal work is questioned.

Adolescent↗

Time course of attention for alcohol cues in abstinent alcoholic patients: the role of initial orienting.

OBJECTIVE: Addicted people are characterized by enhanced attention for drug cues leading to drug use. However, there is little research on the component processes of attention in individuals with alcoholism. Here, we examine 2 distinct components of attention in abstinent alcohol-dependent individuals and social drinkers of alcohol, that is to say, the initial orienting to alcohol-related cues, and the maintenance of attention to them. METHOD: The present study used an "alcohol" version of the visual probe detection task with alcohol-related or neutral pictures being presented briefly (i.e., 50 ms), to assess initial orienting, or longer (i.e., 500 and 1,250 ms), to assess the maintenance of attention. RESULTS: Only alcoholic patients were faster in detecting a probe displayed immediately after pictures related to alcohol presented for 50 ms than in detecting the same probe replacing non-alcohol-related pictures. However, when pictures were presented for 500 ms, only social alcohol drinkers were faster in detecting the probe replacing alcohol scenes. At a stimulus of 1,250 ms duration, no group showed attentional bias toward alcohol cues. In addition, the severity of alcoholism measured by the total number of prior detoxification treatments was positively correlated with the attentional bias (or "attraction") for alcohol pictures presented for 50 ms. CONCLUSIONS: These results show that, subsequent to initial visual orienting to alcohol-related cues, abstinent patients' attention was disengaged from these stimuli, thus suggesting a visual approach-disengagement attentional pattern. The influence of these findings on relapse was discussed.

Adult↗

Effects of spatial attention on contrast response functions in macaque area V4.

Previous single-unit studies of visual cortex have reported that spatial attention modulates responses to different orientations and directions proportionally, such that it does not change the width of tuning functions for these properties. Other studies have suggested that spatial attention causes a leftward shift in contrast response functions, such that its effects on responses to stimuli of different contrasts are not proportional. We have further explored the effects of attention on stimulus-response functions by measuring the responses of 131 individual V4 neurons in two monkeys while they did a task that controlled their spatial attention. Each neuron was tested with a set of stimuli that spanned complete ranges of orientation and contrast during different states of attention. Consistent with earlier reports, attention scaled responses to preferred and nonpreferred orientations proportionally. However, we did not find compelling evidence that the effects were best described by a leftward shift of the contrast response function. The modulation of neuronal responses by attention was well described by either a leftward shift or proportional scaling of the contrast response function. Consideration of differences in experimental design and analysis that may have contributed to this discrepancy suggests that it was premature to exclude a proportional scaling of responses to different contrasts by attention in favor of a leftward shift of contrast response functions. The current results reopen the possibility that the effects of attention on stimulus-response functions are well described by a single proportional increase in a neuron's response to all stimuli.

Animals↗

Effect of spatial attention on the responses of area MT neurons.

This study examines the influence of spatial attention on the responses of neurons in the middle temporal visual area (MT or V5) of extrastriate cortex. Two monkeys were trained to perform a direction-discrimination task. On each trial, two apertures of random-dot stimuli appeared simultaneously at two spatially separated locations; the monkeys were required to discriminate the direction of stimulus motion at one location while ignoring the stimulus at the other location. After extensive training, we recorded the responses of MT neurons in two configurations: 1) Both apertures placed "within" the neuron's receptive field (RF) and 2) one aperture covering the RF while the other was presented at a "remote" location. For each unit we compared the responses to identical stimulus displays when the monkey was instructed to attend to one or the other aperture. The responses of MT neurons were 8.7% stronger, on average, when the monkey attended to the spatial location that contained motion in the "preferred" direction. Attentional effects were equal, on average, in the within RF and remote configurations. The attentional modulations began approximately 300 ms after stimulus onset, gradually increased throughout the trial, and peaked near stimulus offset. An analysis of the neuronal responses on error trials suggests that the monkeys failed to attend to the appropriate spatial location on these trials. The relatively weak attentional effects that we observed contrast strikingly with recent results of Treue and Maunsell, who demonstrated very strong attentional modulations (median effect >80%) in MT in a task that shares many features with ours. Our results suggest that spatial attention alone is not sufficient to induce strong attentional effects in MT even when two competing motion stimuli appear within the RF of the recorded neuron. The difference between our results and those of Treue and Maunsell suggests that the magnitude of the attentional effects in MT may depend critically on how attention is directed to a particular stimulus and on the precise demands of the task.

Animals↗

Foveal attention modulates responses to peripheral stimuli.

When attending to a visual object, peripheral stimuli must be monitored for appropriate redirection of attention and gaze. Earlier work has revealed precentral and posterior parietal activation when attention has been directed to peripheral vision. We wanted to find out whether similar cortical areas are active when stimuli are presented in nonattended regions of the visual field. The timing and distribution of neuromagnetic responses to a peripheral luminance stimulus were studied in human subjects with and without attention to fixation. Cortical current distribution was analyzed with a minimum L1-norm estimate. Attention enhanced responses 100-160 ms after the stimulus onset in the right precentral cortex, close to the known location of the right frontal eye field. In subjects whose right precentral region was not distinctly active before 160 ms, focused attention commonly enhanced right inferior parietal responses between 180 and 240 ms, whereas in the subjects with clear earlier precentral response no parietal enhancement was detected. In control studies both attended and nonattended stimuli in the peripheral visual field evoked the right precentral response, whereas during auditory attention the visual stimuli failed to evoke such response. These results show that during focused visual attention the right precentral cortex is sensitive to stimuli in all parts of the visual field. A rapid response suggests bypassing of elaborate analysis of stimulus features, possibly to encode target location for a saccade or redirection of attention. In addition, load for frontal and parietal nodi of the attentional network seem to vary between individuals.

Adult↗

Transcranial magnetic stimulation of the human frontal eye field: effects on visual perception and attention.

When looking at one object, human subjects can shift their attention to another object in their visual field without moving the eyes. Such shifts of attention activate the same brain regions as those involved in the execution of eye movements. Here we investigate the role of one of the main cortical oculomotor area, namely, the frontal eye field (FEF), in shifts of attention. We used transcranial magnetic stimulation (TMS), a technique known to disrupt transiently eye-movements preparation. We hypothesized that if the FEF is a necessary element in the network involved in shifting attention without moving the eyes, then#10; TMS should also disrupt visuospatial attention. For each volunteer, we positioned the TMS coil over the probabilistic anatomical location of the FEF, and we verified that single pulses delayed eye movements. We then applied TMS during a visuospatial attention task. In this task, a central arrow directed shifts of attention and the subject responded by a keypress to a subsequent visual peripheral target without moving the eyes from the central fixation point. In a few trials, the cue was invalid or uninformative, yielding slower responses than when the cue was valid. We delivered single pulses either 53 msec before or 70 msec after target onset. Contrary to our prediction, the main effect of the stimulation was a decrease in reaction time when it was applied 53 msec before target onset. TMS over the left hemisphere facilitated responses to targets in the right hemifield only and for all cueing conditions, whereas TMS over the right hemisphere had a bilateral effect for valid and neutral but not invalid cueing. Thus, TMS interfered with shift of attention only in the case of right hemisphere stimulation: it increased the cost of invalid cueing. Our results suggest that TMS over the FEF facilitates visual detection, and thereby reduces reaction time. This finding provides new insights into the role of the human FEF in processing visual information. The functional asymmetry observed for both facilitation of visual detection and interference with shifts of attention provides further evidence for the dominance of the right hemisphere for those processes. Our results also underline that the disruptive or facilitative effect of TMS over a given region depends upon the behavioral context.

Adult↗

Visual search and dual tasks reveal two distinct attentional resources.

Most theories of visual processing assume that a target will "pop out" from an array of distractors ("parallel" visual search, e.g., color or orientation discrimination) if targets and distractors can be discriminated without attention. When the discrimination requires attention (e.g., rotated L vs. T or red-green vs. green-red bisected disks), "serial" examination is needed in visual search. Attentional requirements are also frequently assessed by measuring interference from a concurrently performed attentionally demanding task. It is commonly believed that attention acts equivalently in dual-task and visual search paradigms, based on the implicit assumption that visual attentional requirements can be defined along a single dimension. Here we show that there is no such equivalence: We report on targets that do not trigger pop-out, even though they can be discriminated from distractors with attention occupied elsewhere (natural scenes, color-orientation conjunctions); conversely, we show that certain targets that pop out among distractors need undivided attention to be effectively discriminated from distractors when presented in isolation (rotated L vs. +, depth-rotated cubes). In other words, visual search and dual-task performance reveal attentional resources along two independent dimensions. We suggest an interpretation of these results in terms of neuronal selectivities and receptive field size effects.

Attention↗