[Show abstract][Hide abstract] ABSTRACT: Cognitive assessments after stroke are typically short form tests developed for dementia that generates pass/fail classifications (e.g. the MoCA). The Oxford Cognitive Screen (OCS) provides a domain-specific cognitive profile designed for stroke survivors. This study compared the use of the MoCA and the OCS in acute stroke with respect to symptom specificity and aspects of clinical utility. A cross-sectional study with a consecutive sample of 200 stroke patients within 3 weeks of stroke completing MoCA and OCS. Demographic data, lesion side and Barthel scores were recorded. Inclusivity was assessed in terms of completion rates and reasons for non-completion were evaluated. The incidence of cognitive impairments on both the MoCA and OCS sub-domains was calculated and differences in stroke specificity, cognitive profiles and independence of the measures were addressed. The incidence of acute cognitive impairment was high: 76 % of patients were impaired on MoCA, and 86 % demonstrated at least one impairment on the cognitive domains assessed in the OCS. OCS was more sensitive than MoCA overall (87 vs 78 % sensitivity) and OCS alone provided domain-specific information on prevalent post-stroke cognitive impairments (neglect, apraxia and reading/writing ability). Unlike the MOCA, the OCS was not dominated by left hemisphere impairments but gave differentiated profiles across the contrasting domains. The OCS detects important cognitive deficits after stroke not assessed in the MoCA, it is inclusive for patients with aphasia and neglect and it is less confounded by co-occurring difficulties in these domains.
Journal of Neurology 11/2015; DOI:10.1007/s00415-015-7964-4 · 3.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Previous studies have shown that visual extinction can be reduced if two objects are positioned to " afford " an action. Here we tested if this affordance effect was disrupted by " breaking " the affordance, i.e., if one of the objects actively used in the action had a broken handle. We assessed the effects of broken affordance on recovery from extinction in eight patients with right hemisphere lesions and left-sided extinction. Patients viewed object pairs that were or were not commonly used together and that were positioned for left-or right-hand actions. In the unrelated pair conditions, either two tools or two objects were presented. In line with previous research (e.g., Riddoch et al., 2006), extinction was reduced when action-related object pairs and when unrelated tool pairs were presented compared to unrelated object pairs. There was no significant difference in recovery rate between action-related (object-tool) and unrelated tool pairs. In addition, performance with action-related objects decreased when the tool appeared on the ipsilesional side compared to when it was on the contralesional side, but only when the tool handle was intact. There were minimal effects of breaking the handle of an object rather than a tool, and there was no effect of breaking the handle on either tools or objects on single item trials. The data suggest that breaking the handle of a tool lessens the degree to which it captures attention, with this attentional capture being strongest when the tool appears on the ipsilesional side. The capture of attention by the ipsilesional item then reduces the chance of detecting the contralesional stimulus. This attentional capture effect is mediated by the affordance to the intact tool.
Frontiers in Human Neuroscience 10/2015; 9. DOI:10.3389/fnhum.2015.00515 · 3.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We propose a new account of how self-reference affects information processing. We report evidence that self-reference affects the binding of memory to source, the integration of parts into perceptual wholes, and the ability to switch from a prior association to new associations. Self-reference also influences the integration of different stages of processing, linking attention to decision making, and affects the coupling between brain regions mediating self-representation and attention to the environment. Taken together, the data suggest that self-reference acts as a form of 'integrative glue' which can either enhance or disrupt performance, depending on the task context. We discuss the implications for understanding the self, and future directions for research.
Trends in Cognitive Sciences 10/2015; DOI:10.1016/j.tics.2015.08.015 · 21.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We examined whether self-biases in perceptual matching reflect the positive valence of self-related stimuli. Participants associated geometric shapes with either personal labels (e.g., you, friend, stranger) or faces with different emotional expressions (e.g., happy, neutral, sad). They then judged whether shape-label or shape-face pairs were as originally shown or re-paired. Match times were faster to self-associated stimuli and to stimuli associated with the most positive valence. In addition, both the self-bias and the positive emotion-bias were reliable across individuals in different test sessions. In contrast there was no sign of a correlation between the self-bias and the emotion-bias effects. We argue that self-bias and the bias to stimuli linked to positive emotion are separate and may reflect different underlying processes.
[Show abstract][Hide abstract] ABSTRACT: Background:
There are no currently effective cognitive assessment tools for patients who have suffered stroke in the People's Republic of China. The Birmingham Cognitive Screen (BCoS) has been shown to be a promising tool for revealing patients' poststroke cognitive deficits in specific domains, which facilitates more individually designed rehabilitation in the long run. Hence we examined the reliability and validity of a Cantonese version BCoS in patients with acute ischemic stroke, in Guangzhou.
A total of 98 patients with acute ischemic stroke were assessed with the Cantonese version of the BCoS, and an additional 133 healthy individuals were recruited as controls. Apart from the BCoS, the patients also completed a number of external cognitive tests, including the Montreal Cognitive Assessment Test (MoCA), Mini Mental State Examination (MMSE), Albert's cancellation test, the Rey-Osterrieth Complex Figure Test, and six gesture matching tasks. Cutoff scores for failing each subtest, ie, deficits, were computed based on the performance of the controls. The validity and reliability of the Cantonese BCoS were examined, as well as interrater and test-retest reliability. We also compared the proportions of cases being classified as deficits in controlled attention, memory, character writing, and praxis, between patients with and without spoken language impairment.
Analyses showed high test-retest reliability and agreement across independent raters on the qualitative aspects of measurement. Significant correlations were observed between the subtests of the Cantonese BCoS and the other external cognitive tests, providing evidence for convergent validity of the Cantonese BCoS. The screen was also able to generate measures of cognitive functions that were relatively uncontaminated by the presence of aphasia.
This study suggests good reliability and validity of the Cantonese version of the BCoS. The Cantonese BCoS is a very promising tool for the detection of cognitive problems in Cantonese speakers.
[Show abstract][Hide abstract] ABSTRACT: We report 2 experiments to assess the strength of forming and breaking associations to the self, familiar others, and unfamiliar others in a simple shape-label matching task. In each experiment, participants first formed shape-person associations (e.g., triangle-self). Subsequently, they had to relearn the associations with the shapes and labels rearranged (self→stranger in Experiment 1; self→friend in Experiment 2) and they carried out a matching task in which they judged whether shape-label stimuli were as newly instructed or re-paired. There were faster responses and fewer errors on match trials for newly formed self-associated stimuli. In contrast, after switching, reaction times were slower and accuracy was reduced on mismatch trials involving shapes previously associated with the self. The strength of the self-advantage in forming the new association on match trials correlated with the difficulty in switching from the old self-associated shape on mismatch trials. The results indicate that self-reference enhances the binding of associations in memory; this facilitates associations to new stimuli, but there is a cost of interference from old associations. (PsycINFO Database Record
Journal of Experimental Psychology Human Perception & Performance 09/2015; DOI:10.1037/xhp0000125 · 3.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: People tend to respond faster to self-relevant stimuli relative to stimuli associated with other people. There is well-established evidence on the self-bias effect on high level memory and attentional processes, but little evidence for effects on perception. In this study, we test whether the self-bias effect can modulate perception, by focusing on the effect of self-bias on the earliest cortical component C1 which links to activity in the primary visual cortex (V1). Using high-density event-related potential measures, we recorded participants' brain activity when they performed a matching task to personally relevant stimuli. Participants were randomly assigned three sets of geometric shapes (triangle, circle, and square) to three personal labels (self, mother, and stranger). After the associative instruction, they carried out a shape-label matching task. The size of the stimuli was manipulated (large vs. small). The results showed that there were faster responses to the shape associated with the self compared to others, showing the self-bias effect. The effect was modulated by the size of stimuli - participants made faster responses to the large than to the small stimuli in the self association, whereas there were no differences between the large and small stimuli for other associations (mother and stranger associations). The size effect in self-bias was linked to the activity in the C1 component. The amplitude of C1 increased for the large relative to small shapes associated with the self, but the size of stimuli did not affect the amplitude between the large and small stimuli in other associations. The results indicated that self-bias can affect perception by modulating the earliest C1 component generated in the primary visual cortex. The data suggest that the self-bias may automatically facilitate the perceptual encoding of visual stimuli early on just following stimuli onset. Meeting abstract presented at VSS 2015.
Journal of Vision 09/2015; 15(12):611. DOI:10.1167/15.12.611 · 2.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Traditionally, response selection is considered to reflect a separate stage of processing to visual perception. An alternative view proposes action and perception to be closely linked; however the processing stage where any cross-modal interaction would then occur remains unclear. In this study, we investigated the influence of response-mapping on a simple classification task. We presented an array of eight frames arranged in a square around a fixation point, followed by a brief presentation of an arrow in one of them (varying SOAs of 10,30,50,80 and 100ms masked). The arrow could appear in a congruent, incongruent or a neutral location with respect to its direction. Participants indicated the direction of the arrow using a response-box organized in a corresponding configuration: eight response-buttons, arranged in a square; an arrow appeared on each button. In Exp 1, the directions of the buttons matched their locations (e.g., arrow pointing right appearing on the right side); In Exp 2, the arrows and the locations were mismatched (arrow appearing on the left side, pointing right). Subsequently we manipulated the response-mapping between the locations and directions of the arrows. We changed the task to respond to locations instead of direction, in a single (Exp 3) and a dual task (Exp 5); and replicated our original experiment with different exposure times (Exp 4). In our first experiment, we observed a robust congruency effect on accuracy for arrows appearing in their matching locations. Crucially, in our following experiments, we managed to invert and manipulate this effect by changing the motor-response mapping. Using mathematical modelling according to the Theory of Visual Attention, we demonstrate that motor-mapping modulates two low-level processes independently: perceptual threshold and stimulus processing speed. We discuss the implications of multi-modal integration within a general framework of attention as a proactive cognitive function, which predicts and formulates visual percepts. Meeting abstract presented at VSS 2015.
Journal of Vision 09/2015; 15(12):985. DOI:10.1167/15.12.985 · 2.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Left neglect is traditionally reported to be much more common and more severe than right neglect. Often this is taken as support for a right hemispheric specialisation of visuo-spatial attention. Here, we explore the incidence and severity of ego-and allocentric neglect in a consecutive acute stroke sample (N=298) and compare left versus right neglect recovery 6 months post stroke (N=121). Patients completed the hearts cancellation task from the Oxford Cognitive Screen on average after 6 days and again 6 months post-stroke. The results demonstrated that egocentric and allocentric neglect are separable subtypes with egocentric and allocentric neglect occurring in isolation in 46 and 27% of the acute neglect patients, respectively. In addition, we found that in participants with only allocentric neglect there was no egocentric spatial laterality to the false positive errors made. Though left egocentric neglect was more prevalent (67%) in right hemisphere patients, the severity was not significantly different from that in left hemisphere cases (in terms of the absolute asymmetry scores). In addition, there was an equal incidence of left and right allocentric neglect (51% vs 49%). However, in terms of recovery, at 6 months post stroke, right neglect was much more likely to recover (only 2 patients still demonstrated right neglect at follow up). There were no differences in recovery rates for ego- vs allocentric neglect. The lack of an effect of egocentric spatial bias to allocentric errors provides strong evidence that these disorders are independent. In addition, the greater likelihood of left neglect continuing at 6 months, despite it having the same severity for left and right hemisphere patients, is consistent with right hemisphere patients (and patients with chronic neglect) having disorders additional to a bias in spatial orienting. Meeting abstract presented at VSS 2015.
Journal of Vision 09/2015; 15(12):179. DOI:10.1167/15.12.179 · 2.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Participants show a perceptual bias favoring stimuli associated with the participants themselves over stimuli associated with other people. A major account of this self-bias effect is that self-related information is intrinsically rewarding, and that high-reward stimuli have enhanced perceptual processing. Here we used redundancy gains to examine the relations between self bias and reward, and whether self and reward biases modulate common levels of stimulus integration. We demonstrated that the self-association bias increases when more than one exemplar of the stimulus is presented (i.e., when participants are exposed to redundant stimuli). The larger self-bias effects for redundant than for single stimuli arose at both perceptual and conceptual levels of representation (respectively, for identical and nonidentical stimuli associated with the same category). In contrast, high-reward stimuli did not affect perceptual redundancy gains with identical shapes, but they did affect redundancy gains with nonidentical stimuli associated with the same category. The strong redundancy effects with self-related stimuli are consistent with self associations modulating stimulus integration at both perceptual and conceptual levels, whereas reward only modulated higher-level conceptual processes (with nonidentical stimuli). The data provide two novel theoretical advances, by showing that (i) self association modulates both early perceptual coding and higher-level conceptual coding, whereas reward only affects the higher-level process, and (ii) self bias can not be reduced simply to differential effects of reward.
[Show abstract][Hide abstract] ABSTRACT: We assessed the effects of pairing a target object with its familiar color on eye movements in visual search, under conditions where the familiar color could or could not be predicted. In Experiment 1 participants searched for a yellow- or purple-colored corn target amongst aubergine distractors, half of which were yellow and half purple. Search was more efficient when the color of the target was familiar and early eye movements more likely to be directed to targets carrying a familiar color than an unfamiliar color. Experiment 2 introduced cues which predicted the target color at 80 % validity. Cue validity did not affect whether early fixations were to the target. Invalid cues, however, disrupted search efficiency for targets in an unfamiliar color whilst there was little cost to search efficiency for targets in their familiar color. These results generalized across items with different colors (Experiment 3). The data are consistent with early processes in selection being automatically modulated in a bottom-up manner to targets in their familiar color, even when expectancies are set for other colors.
[Show abstract][Hide abstract] ABSTRACT: There are biases in perceptual matching between shapes and labels referring to familiar others, compared with when the labels refer to unfamiliar people. We assessed whether these biases could be affected by differential feedback (using the differential outcomes procedure [DOP]) compared with when feedback is provided using a nondifferential outcomes procedure (NOP). Participants formed associations between simple geometric shapes and labels referring to people the participant did or did not know (self, best friend, other). Subsequently, the task was to match a label to one of two shapes shown on a trial. When feedback for correct responses was given following the NOP condition, matches were faster to known people (self and friend) compared with those to an unknown person (stranger). However, this advantage for known personal relations was eliminated when participants were given feedback for correct responses following the DOP condition. The data are consistent with prior work showing that the DOP can facilitate the learning of taxing associations (for the stranger stimuli relative to the familiar self and friend stimuli). In addition, the results suggest that the facilitated perceptual matching for stimuli associated to individuals known personally may reflect better individuation of the association between the shape stimulus and the label, a process enhanced by using a DOP for associations with unfamiliar people.
[Show abstract][Hide abstract] ABSTRACT: The ability to search efficiently for visual targets among distractors can break down after a variety of brain lesions, but the specific processes affected by the lesions are unclear. We examined search over space (conjunction search) and over time plus space (preview search) in a consecutive series of patients with acquired brain lesions. We also assessed performance on standard neuropsychological measures of visuospatial STM (Corsi Block), sustained attention and memory updating (the contrast between forward and backward digit span), and visual neglect. Voxel-based morphometry analyses revealed regions in the occipital (middle occipital gyrus), posterior parietal (angular gyrus), and temporal cortices (superior and middle temporal gyri extending to the insula), along with underlying white matter pathways, associated with poor search. Going beyond standard voxel-based morphometry analyses, we then report correlation measures of structural damage in these regions and the independent neuropsychological measures of other cognitive functions. We find distinct patterns of correlation in areas linked to poor search, suggesting that the areas play functionally different roles in search. We conclude that neuropsychological disorders of search can be linked to necessary and distinct cognitive functions, according to the site of lesion.
[Show abstract][Hide abstract] ABSTRACT: Evidence from experiments with single objects indicates that perceiving objects leads to automatic extraction of affordances. Here we examined the influence of implied between-object actions on affordance processing. Images of task-irrelevant object pairs (e.g., a spoon and a bowl) were followed by imperative central targets. Participants made speeded left/right responses to targets, and the responses randomly aligned with the affordance of one of the objects. The orientation of one object was manipulated across trials, leaving the colocation between objects correct or incorrect for potential interaction. Four experiments demonstrated that positioning the objects correctly for between-object actions led to a prioritization of the object active in the action (e.g., the spoon) over the passive (e.g., the bowl) object. Moreover, there was an inhibitory effect on responses to the passive object: responses congruent with the passive object were slower when pairs of objects were shown as if in interaction, compared with when they were not. The effects did not change in the single-hand response task but disappeared when the passive objects were absent-though an affordance should still have been presented by the active object. These results present evidence for affordance selection in action-related object pairs, and suggest inhibition of the action afforded by the passive objects under conditions of affordance competition. (PsycINFO Database Record
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Journal of Experimental Psychology Human Perception & Performance 05/2015; 41(4). DOI:10.1037/xhp0000059 · 3.36 Impact Factor