Implicit learning: A way to improve visual search in spatial neglect?

Studies have shown that neglect patients are able to use stimulus regularities to orient faster toward the neglected side, without necessarily being aware of that information, or at the very least without being able to verbalize their knowledge. In order to better control for the involvement of explicit processes, the present study sought to test neglect patients' ability to detect more complex associations between stimuli using tasks similar to those used in implicit learning studies. Our results demonstrate that neglect patients had difficulties implicitly learning complex associations, contrary to what we found with controls. The possible influence of attentional and working memory impairments are discussed.

Studying self-awareness in children: validation of the Questionnaire of Executive Functioning (QEF).

OBJECTIVE: People with accurate representations of their own cognitive functioning (i.e. cognitive self-awareness) tend to use appropriate strategies to regulate their behavior. Due to the lack of appropriate instruments, few studies have examined the development of this ability among children. METHOD: This study tested the measurement properties of the self-rating and other-rating forms of the Questionnaire of Executive Functioning (QEF), designed to tap children's knowledge of their executive functioning. Specifically, the construct, convergent, and discriminant validities were investigated and a self-other discrepancy score was computed to assess children's executive self-awareness. Participants were 317 children aged 7-14 years old. RESULTS: Confirmatory factor analyses carried out on the QEF confirmed the eight-factor structure of both versions. There were significant correlations between the QEF and the parent versions of the Behavior Rating Inventory of Executive Function, the Dysexecutive Questionnaire for Children, and the Childhood Executive Functioning Inventory. Both forms of the QEF were able to distinguish between children who had sustained a traumatic brain injury (TBI) and control participants. A statistical difference was observed between the TBI and control groups on this score, suggesting that TBI may trigger self-awareness impairments in children. CONCLUSION: The good psychometric properties of the two forms of the QEF were established. Furthermore, results of the analyses carried out on the different discrepancy scores seem to indicate that the QEF could help clinicians to detect patients with self-awareness deficits.

Shedding new light on representational neglect: The importance of dissociating visual and spatial components.

Over the last decade, many studies have demonstrated that visuospatial working memory (VSWM) can be divided into two subsystems, dealing respectively with spatial and visual information. A similar dissociation has been observed in brain-damaged patients without neglect for mental imagery skills. The first aim of the present study was to examine whether performance dissociations between spatial and visual mental imagery can be observed in unilateral neglect. The second objective was to further investigate the role of spatial and visual working memory subsystems in the mental representation abilities of neglect patients and healthy controls, and their dependence on the nature of the mental imagery tasks performed. The results showed that spatial and visual imagery processes can be selectively impaired in unilateral neglect. Spatial working memory skills were also found to strongly predict spatial imagery score in the two experimental groups. However, contrary to what was observed in healthy controls, visual working memory did not appear to predict performance on visual imagery tasks in neglect patients. Overall, these findings highlight the importance of investigating both visual and spatial components of working memory and mental imagery in neglect patients.

Procedural learning, consolidation, and transfer of a new skill in Developmental Coordination Disorder.

The aim of this study was to explore the differences in procedural learning abilities between children with DCD and typically developing children by investigating the steps that lead to skill automatization (i.e., the stages of fast learning, consolidation, and slow learning). Transfer of the skill to a new situation was also assessed. We tested 34 children aged 6-12 years with and without DCD on a perceptuomotor adaptation task, a form of procedural learning that is thought to involve the cerebellum and the basal ganglia (regions whose impairment has been associated with DCD) but also other brain areas including frontal regions. The results showed similar rates of learning, consolidation, and transfer in DCD and control children. However, the DCD children's performance remained slower than that of controls throughout the procedural task and they reached a lower asymptotic performance level; the difficulties observed at the outset did not diminish with practice.

Support for distinct subcomponents of spatial working memory: a double dissociation between spatial-simultaneous and spatial-sequential performance in unilateral neglect.

Over the last decade, many studies have demonstrated that visuospatial working memory (VSWM) can be divided into separate subsystems dedicated to the retention of visual patterns and their serial order. Impaired VSWM has been suggested to exacerbate left visual neglect in right-brain-damaged individuals. The aim of this study was to investigate the segregation between spatial-sequential and spatial-simultaneous working memory in individuals with neglect. We demonstrated that patterns of results on these VSWM tasks can be dissociated. Spatial-simultaneous and sequential aspects of VSWM can be selectively impaired in unilateral neglect. Our results support the hypothesis of multiple VSWM subsystems, which should be taken into account to better understand neglect-related deficits.

Can the exploration of left space be induced implicitly in unilateral neglect?

The purpose of the present study was to explore the ability of neglect patients to detect and exploit the predictive value of a cue to respond more quickly and accurately to targets on their contralesional side in a Posner spatial cueing task. The majority of the cues (i.e. 80%) were invalid, indicating that the target would appear on the opposite side, although patients were not informed of this bias. Our results demonstrate that some neglect patients were able to extract the cue's predictability and use it to orient faster toward the left. This cueing effect was present even in patients who were subsequently unable to describe the predictive character of the cues, and thus was not modulated by reportable awareness of the cue-target relation.

Cortical and subcortical contributions to state- and strength-based perceptual judgments.

UNLABELLED: Perceptual judgments can be made on the basis of different kinds of information: state-based access to specific details that differentiate two similar images, or strength-based assessments of relational match/mismatch. We explored state- and strength-based perception in eleven right-hemisphere stroke patients, and examined lesion overlap images to gain insight into the neural underpinnings of these different kinds of perceptual judgments. Patients and healthy controls were presented with pairs of scenes that were either identical or differed in that one scene was slightly expanded or contracted relative to the other. Same/different confidence judgments were used to plot receiver-operating characteristics and estimate the contributions of state- and strength-based perception. The patient group showed a significant and selective impairment of strength-based, but not state-based, perception. This finding was not an artifact of reduced levels of overall performance, because matching perceptual discriminability levels between controls and patients revealed a double dissociation, with higher state-based, and lower strength-based, perception in patients vs. CONTROLS: We then conducted exploratory follow-up analyses on the patient group, based on the observation of substantial individual differences in state-based perception - differences that were masked in analyses based on the group mean. Patients who were relatively spared in state-based perception (but impaired in strength-based perception) had damage that was primarily in temporo-parietal cortical regions. Patients who were relatively impaired in both state- and strength-based perception had overlapping damage in the thalamus, putamen, and adjacent white matter. These patient groups were not different in any other measure, e.g., presence of spatial neglect symptoms, age, education, lesion volume, or time since stroke. These findings shed light on the different roles of right hemisphere regions in high-level perception, suggesting that the thalamus and basal ganglia play a critical role in state- and strength-based perception, whereas temporo-parietal cortical regions are important for intact strength-based perception.

Visual neglect: is there a relationship between impaired spatial working memory and re-cancellation?

In visual search tasks, neglect patients tend to explore and repeatedly re-cancel stimuli on the ipsilesional side, as if they did not realize that they had previously examined the rightward locations favoured by their lateral bias. The aim of this study was to explore the hypothesis that a spatial working memory deficit explains these ipsilesional re-cancellation errors in neglect patients. For the first time, we evaluated spatial working memory and re-cancellation through separate and independent tasks in a group of patients with right hemisphere damage and a diagnosis of left neglect. Results showed impaired spatial working memory in neglect patients. Compared to the control group, neglect patients cancelled fewer targets and made more re-cancellations both on the left side and on the right side. The spatial working memory deficit appears to be related to re-cancellations, but only for some neglect patients. Alternative interpretations of re-exploration of space are discussed.