Neuroanatomical and behavioural factors associated with the effectiveness of two weekly sessions of prism adaptation in the treatment of unilateral neglect.

Among the different interventions to alleviate the symptoms of unilateral neglect, prism adaptation (PA) appears especially promising. To elucidate the contribution of some neuroanatomical and behavioural factors to PA's effectiveness, we conducted a study combining neuropsychological and lesion mapping methods on a group of 19 neglect patients who underwent two sessions of PA during one week and assessed their improvement relative to the baseline until the following week (7-8 days later). Correlation analyses revealed a significant positive relationship between the magnitude of the proprioceptive after-effect and the improvement at the follow-up session in two perceptual tasks requiring motor responses. Conversely, no correlation was found between the proprioceptive after-effect and the improvement in a perceptual task with no motor involvement. This finding suggests that patients' potential to show a prism-related improvement in motor-related tasks might be indicated by the strength of their proprioceptive response (proprioceptive after-effect). As for the neuroanatomical basis of this relationship, subtraction analyses suggested that patients' improvement in perceptual tasks with high motor involvement might be facilitated by the integrity of temporo-parietal areas and the damage of frontal and subcortical areas.

Designing rehabilitation programs for neglect: could 2 be more than 1+1?

Unilateral neglect is a multimodal neuropsychological disorder that has puzzled scientists for a long time. Many interventions have been developed, but only a handful has proven to be effective. This review examines whether applying different therapeutic techniques in combination will increase therapeutic benefits. Studies were reviewed where therapies are applied sequentially or in combination with other techniques. The results indicate that combining different interventions leads to increased general improvement compared with other noncombined designs, even when the number of treatment sessions is not constant. Practical and theoretical aspects of different treatments are discussed. The combined approach to treatment may have direct relevance to disorders other than neglect. This report introduces a new classification scheme for different interventions with the aim of facilitating more focused therapy. Finally, suggestions are made as to what the focus of future studies of neglect therapy should be and how therapeutic benefits might be maximized.

Strength in numbers: combining neck vibration and prism adaptation produces additive therapeutic effects in unilateral neglect.

Unilateral neglect is a multifaceted disorder. Many authors have, for this reason, speculated that the best treatment for neglect will involve combinations of different therapeutic techniques. Two well-known interventions, neck vibration (NV) and prism adaptation (PA), have often been considered to be among the most effective treatments for neglect. Here, two experiments were performed to explore possible additive benefits when these interventions are used in combination to treat chronic neglect. Both experimental groups received NV for 20 minutes, while the second group received simultaneous PA. The effects of treatment were measured with a time-restricted and feedback-based visual search task, which has previously been found to abolish the beneficial effects of PA, and with standard neglect tests. Baseline and intervention measures were performed on separate days. Findings for both groups indicated improved visual search following intervention, but the patients that underwent the combined intervention (NVPA) showed clear improvements on visual search paper and pencil neglect tests unlike the NV-only group. Overall, our results suggest that PA strengthens the effects of NV and that feedback-based tasks do not abolish the beneficial effects of PA, when NV is applied simultaneously. The results support the view that the most effective treatment for neglect will involve the combination of different treatments.

Prism adaptation improves visual search in hemispatial neglect.

Visuomotor prism adaptation has been found to induce a lateral bias of spatial attention in chronic hemispatial neglect patients. Here, two experiments were conducted to explore the effects of 10 degrees prism adaptation on visual search tasks and standard visual inattention tests. Baselines and intervention effects were measured on separate days for all patients. The first experiment explored whether prism adaptation affects performance on a time restricted visual search task (maximum 3500ms presentation followed by visual and auditory feedback). No positive effects of prism adaptation were found on accuracy in visual search nor on traditional neglect tests. These results accord well with previous studies showing that increased cognitive load can lead to prism de-adaptation or unchanged performance following prism adaptation. Response times in visual search became faster following intervention but this was not the case for the standard neglect tests. In the second experiment, the same single-featured search task was used, but the participants had unlimited search time and received no feedback on their response. This time, the patients showed accuracy improvements in visual search and all four on regular neglect tests. Therapeutic effects lasted for at least 90-120min. Response times on all tasks became faster after prism adaptation. The results are consistent with studies showing effects of prism adaptation on neuropsychological neglect tests and other attentional tasks that are not speeded or time restricted, where feedback is not provided, or are performed following non-feedback-based tasks. The current findings show that prism adaptation improves visual search in neglect and that these beneficial effects can disappear with feedback.

Repetition of distractor sets improves visual search performance in hemispatial neglect.

Priming from repeated distractor sets, or search context, in conjunctive visual search was examined in four patients with hemispatial neglect. In the first experiment overall context was either changed or repeated while the target was always the same to control for any modulatory effect of target priming. Considerable priming was seen from repeated context. In the second experiment the context was either repeated on the left side, on the right side, on both sides, or the context was new. Priming from repeated context was found to arise from the left visual field, as well as the right visual field, as well as when overall context was repeated. Brief masked displays were used in experiment 3, the results again showing strong priming from repeated overall context. The results of the three experiments suggest that visual grouping, or perceptual organization, of distractor sets is relatively intact in the affected hemifield of parietal neglect patients. Furthermore, repetition of context may even temporarily ameliorate neglect symptoms in search. These findings are consistent with claims that grouping is distinct from attentional processing and that it operates at lower levels of the perceptual hierarchy.

Repetitive TMS in right sensorimotor areas affects the selection and completion of contralateral movements.

Although the existence of directional motor deficits (DMD) associated with movement planning and/or execution seems to be widely recognized, neglect and single cell studies examining their neuroanatomical foundation have produced contradictory and inconclusive findings. The present study assessed the occurrence of DMD following the application of repetitive transcranial magnetic stimulation (rTMS) over two regions, as commonly reported in the neglect literature, namely the right middle frontal gyrus (rMFG) and the right angular gyrus (rAG). Fourteen healthy subjects underwent rTMS while performing an auditory choice task, involving pointing toward two laterally located targets, under internally (i.e., pointing side freely selected) and externally guided conditions (i.e., pointing side guided by spatial auditory cues). In order to examine whether subjects compensated for induced deficits with the help of vision, visual feedback was occluded at movement onset in half of the trials. rTMS applied to the rAG significantly increased reaction times (RTs) for leftward internally-guided movements. In contrast, rTMS applied to the rMFG reduced the likelihood to complete leftward internally-guided movements under blindfolded conditions. These effects suggest that DMD might involve cognitive processes contributing to the different stages of motor control, such as movement selection and goal maintenance.

Motor Response Deficits of Unilateral Neglect: Assessment, Therapy, and Neuroanatomy.

The clinical impact of the motor deficits of unilateral neglect is indisputable. The diagnosis criteria are confusing and complicated, and assessment has been extended and modified gradually during the last few decades, which has led to inconsistency and confusion. Many different attempts have been made to overcome various assessment shortcomings. In this article, different examinations of previous studies and analyses are discussed in a systematic and critical way. Research databases were used to identify 254 reports, including 26 different empirical studies on motor neglect and 44 studies on premotor neglect. Most of the studies address the gross neuroanatomical location of lesions. The main findings indicate that frontal lesions are more common in motor neglect than in premotor neglect, and parietal lesions are more common in premotor neglect than in motor neglect. Few studies have evaluated therapeutic programs for the motor deficits of neglect. Unfortunately, most studies suffer from various diagnostic problems that result in inconsistent and controversial findings. Different assessment issues need to be addressed systematically in future studies in light of current findings to increase our understanding and awareness of these important neuropsychological motor deficits. Implications of and possible solutions to the current assessment shortcomings are discussed.

The boundary conditions of priming of visual search: from passive viewing through task-relevant working memory load.

Priming of visual search has a dominating effect upon attentional shifts and is thought to play a decisive role in visual stability. Despite this importance, the nature of the memory underlying priming remains controversial. To understand more fully the necessary conditions for priming, we contrasted passive versus active viewing of visual search arrays. There was no priming from passive viewing of search arrays, while it was strong for active search of the same displays. Displays requiring no search resulted in no priming, again showing that search is needed for priming to occur. Finally, we introduced working memory load during visual search in an effort to disrupt priming. The memorized items had either the same colors as or different colors from the visual search items. Retaining items in working memory inhibited priming of the working memory task-relevant colors, while little interference was observed for unrelated colors. The picture that emerges of priming is that it requires active attentional processing of the search items in addition to the operation of visual working memory, where the task relevance of the working memory load plays a key role.

P300 in neglect.

OBJECTIVE: Attentional deficits have been thought to underlie hemispatial neglect. The present study investigates this using the P300 component of the event-related potential, which is assumed to reflect the allocation of attention. METHODS: We recorded the P300 and oddball detection performance from patients with neglect. Infrequent targets appeared either in the affected contralesional or the unaffected ipsilesional visual hemifield. RESULTS: Contralesional targets produced weaker average P300 responses than ipsilesional ones, but stronger responses than when only distractors were presented. In the affected hemifield, the difference in P300 amplitude between identified and missed targets was correlated with the miss rate. The number of missed contralesional targets for a given participant was positively correlated with the time required for completion of standard neglect tests. CONCLUSIONS: The P300 not only reflects a general attentional impairment in neglect, but also varies as a function of the participants' awareness of individual stimuli. SIGNIFICANCE: The findings reflect an important link between attentional dysfunction and impaired stimulus processing in neglect and extinction.

Neural correlates of inter-trial priming and role-reversal in visual search.

Studies of priming of visual perception demonstrate that observers respond more quickly to targets in a field of distractors when relevant features are repeated versus novel or role-reversed. In a recent brain imaging study by Kristjánsson et al. (2007), participants were presented with two items of one color and a single item in a different color with the task of reporting the orientation of the uniquely colored item. Consistent with previous behavioral reports, they found that observers were faster to respond when the target and distractor colors were identical to the previous trial than when they were reversed. They found reduced BOLD activity in brain areas linked with attentional control on trials where the target and distractor colors were repeated relative to reversed, which they interpreted as reflecting response suppression (decreased BOLD signal for repeated stimuli). However, since their design only compared repeated versus reversed task demands, it is logically possible that this pattern reflects increased BOLD signal for role-reversed stimuli: activity required to inhibit previously facilitated information and select previously inhibited information. We explored this possibility with a task where we contrasted the signal generated by repeated, reversed, and novel features. Our data suggest that the majority of the change in neural signal elicited by priming of pop-out reflects increased activation when selection criteria are reversed.

[Unilateral spatial neglect: a review of symptoms, frequency diagnosis and prognosis]. / Gaumstol--yfirlit--einkenni, tídni, greining og horfur.

Unilateral spatial neglect is a disorder commonly encountered after hemisphere stroke, most often in the right hemisphere. Neglect patients fail to attend and respond to stimuli presented on the side of space opposite to the brain lesion. Neglect implies a complex dysfunction in the co-action between perception, motor behavior and the environment where the patients attentive capacities and the environmental space are of special importance. Patients difficulties can be seen in that they do not eat from the left side of the plate or omit words to the left when asked to read. Commonly patients do not have a complete insight into their neglect problems. Neglect in stroke patients has been associated with poor outcome on functional activities. Signs of neglect are not always obvious but can be explored and assessed quickly by bedside neuropsychological testing. Neglect is often more unclear to an observer than, e.g. if a patient suffers from paresis or aphasia. Education for patients, their relatives and others are therefore important.

Hypomanic trait is associated with a hypovigilant automatic attentional response to social cues of danger.

OBJECTIVES: Hypomania in bipolar disorders is characterized by disinhibited, fearless and reward-seeking behavior. This behavioral pattern suggests that early and automatic responding to socio-emotional cues such as facial expressions might be aberrant in hypomania. The present study tested the predictions that participants selected on hypomania-like trait would show hypovigilant responses to facial cues of danger and increased responses to facial cues of reward. METHODS: From a group of 513, the 16 most trait-hypomanic individuals were selected by use of a shortened version of an established self-report instrument, the General Behavior Inventory (GBI). Their spatial-attentional responses after perception of dynamic fearful and happy facial gaze cues were compared with those of 12 controls. RESULTS: The group difference for full GBI hypomania scores was reliable (p=0.000). Individuals with elevated hypomanic traits clearly demonstrated attentional hypovigilance after perception of fearful, laterally gazing faces (p=0.009). In addition, unlike controls, they demonstrated reliable attentional responding to happy gaze cues (p=0.007). CONCLUSIONS: These data provide the first experimental evidence that hypomania-like trait is associated with hypovigilant, fearless responding to the social cue of an emotionally expressive gaze.