Patterns of recovery from hemiplegia following stroke

Lost in Time: Temporal Monitoring Elicits Clinical Decrements in Sustained Attention Post-Stroke

OBJECTIVES

Mental fatigue, 'brain fog', and difficulties maintaining engagement are commonly reported issues in a range of neurological and psychiatric conditions. Traditional sustained attention tasks commonly measure this capacity as the ability to detect target stimuli based on sensory features in the auditory or visual domains. However, with this approach, discrete target stimuli may exogenously capture attention to aid detection, thereby masking deficits in the ability to endogenously sustain attention over time.

METHODS

To address this, we developed the Continuous Temporal Expectancy Task (CTET) where individuals continuously monitor a stream of patterned stimuli alternating at a fixed temporal interval (690 ms) and detect an infrequently occurring target stimulus defined by a prolonged temporal duration (1020 ms or longer). As such, sensory properties of target and non-target stimuli are perceptually identical and differ only in temporal duration. Using the CTET, we assessed stroke survivors with unilateral right hemisphere damage (N = 14), a cohort in which sustained attention deficits have been extensively reported.

RESULTS

Stroke survivors had overall lower target detection accuracy compared with neurologically healthy age-matched older controls (N = 18). Critically, stroke survivors performance was characterised by significantly steeper within-block performance decrements, which occurred within short temporal windows (˜3 ½ min), and were restored by the break periods between blocks.

CONCLUSIONS

These findings suggest that continuous temporal monitoring taxes sustained attention processes to capture clinical deficits in this capacity over time, and outline a precise measure of the endogenous processes hypothesised to underpin sustained attention deficits following right hemisphere stroke.

Examining the relationship between fatigue and cognition after stroke: A systematic review

Many stroke survivors experience fatigue, which is associated with a variety of factors including cognitive impairment. A few studies have examined the relationship between fatigue and cognition and have obtained conflicting results. The aim of the current study was to review the literature on the relationship between fatigue and cognition post-stroke. The following databases were searched: EMBASE (1980-February, 2014), PsycInfo (1806-February, 2014), CINAHL (1937-February, 2014), MEDLINE (1946-February, 2014), Ethos (1600-February, 2014) and DART (1999-February, 2014). Reference lists of relevant papers were screened and the citation indices of the included papers were searched using Web of Science. Studies were considered if they were on adult stroke patients and assessed the following: fatigue with quantitative measurements (≥ 3 response categories), cognition using objective measurements, and the relationship between fatigue and cognition. Overall, 413 papers were identified, of which 11 were included. Four studies found significant correlations between fatigue and memory, attention, speed of information processing and reading speed (r = -.36 to .46) whereas seven studies did not. Most studies had limitations; quality scores ranged from 9 to 14 on the Critical Appraisal Skills Programme Checklists. There was insufficient evidence to support or refute a relationship between fatigue and cognition post-stroke. More robust studies are needed.

Right hemisphere role in cognitive reserve

High levels of education, occupational complexity, and/or premorbid intelligence are associated with lower levels of cognitive impairment than would be expected from a given brain pathology. This has been observed across a range of conditions including Alzheimer's disease (Roe et al., 2010), stroke (Ojala-Oksala et al., 2012), traumatic brain injury (Kesler et al., 2003), and penetrating brain injury (Grafman, 1986). This cluster of factors, which seemingly protect the brain from expressing symptoms of damage, has been termed "cognitive reserve" (Stern, 2012). The current review considers one possible neural network, which may contribute to cognitive reserve. Based on the evidence that the neurotransmitter, noradrenaline mediates cognitive reserve's protective effects (Robertson, 2013) this review identifies the neurocognitive correlates of noradrenergic (NA) activity. These involve a set of inter-related cognitive processes (arousal, sustained attention, response to novelty, and awareness) with a strongly right hemisphere, fronto-parietal localization, along with working memory, which is also strongly modulated by NA. It is proposed that this set of processes is one plausible candidate for partially mediating the protective effects of cognitive reserve. In addition to its biological effects on brain structure and function, NA function may also facilitate networks for arousal, novelty, attention, awareness, and working memory, which collectively provide for a set of additional, cognitive, mechanisms that help the brain adapt to age-related changes and disease. It is hypothesized that to the extent that the lateral surface of the right prefrontal lobe and/or the right inferior parietal lobe maintain structural (white and gray matter) and functional integrity and connectivity, cognitive reserve should benefit and behavioral expression of pathologic damage should thus be mitigated.

Reliability and validity of the Cantonese version of the Test of Everyday Attention among normal Hong Kong Chinese: a preliminary report

OBJECTIVE

To validate the translated Cantonese version of an ecologically valid clinical test of attention - the Test of Everyday Attention (TEA).

DESIGN

A cross-sectional study was conducted on a sample of 49 healthy participants with a mean age of 25.9 years in the Hong Kong Chinese setting.

OUTCOME MEASURES

These included the Color Trails Test, Stroop Colour-Word Test, Symbol Digit Modalities Test, Word Fluency Test, Design Fluency Test, Digits Backward Span Test and Modified Six Elements Test. In addition, the Cognitive Failures Questionnaire and Dysexecutive Questionnaires were also administered to the participants.

RESULTS

The TEA was found to have a good range of test-retest reliability. The convergent validity of the instrument was established by correlation of the TEA with various measurements of attention, whereas the divergent validity was demonstrated by the insignificant correlation with tests of other cognitive functioning. Factor analysis of the TEA subtests replicated the major factor structure of the original version.

CONCLUSION

The present study indicates that the translated TEA represents a culturally appropriate tool for measuring everyday life attention performance among the healthy Hong Kong Chinese.

A pilot study of attention deficits, balance control and falls in the subacute stage following stroke

OBJECTIVES

To (1) identify and monitor changes in deficits of attention and balance in the subacute stage following stroke, (2) investigate fall events, (3) explore relationships between deficits of attention, balance and falling post stroke.

DESIGN

A prospective observational study.

SETTING

Hospitalized patients with stroke were recruited from a rehabilitation ward.

SUBJECTS

Fourteen subjects were recruited, 13 subjects (age 21-80 years) completed all assessments. Ten had right and three had left hemispheric lesions. Eight subjects were male.

MAIN OUTCOME MEASURES

Subjects were assessed on two occasions during a six-week period. Standardized tests were used to measure unilateral visual neglect, sustained and selective attention and balance. Fall histories were collected by chart review and semi-structured interview.

RESULTS

At the initial assessment six subjects had sustained auditory attention deficit, eight had deficits of auditory selective attention, 12 had visual selective attention deficits and seven subjects presented with visual inattention. Scores for visual inattention and visual selective attention improved over time (p = 0.006, p = 0.026 respectively) as did scores for balance control (p = 0.001). Auditory selective attention scores at the first assessment were found to correlate with measures of balance (p < 0.01), subjects with normal attention scores achieved better balance scores. Four subjects fell at least once during the six weeks. Scores for attention and balance of fallers were not found to be significantly different from the scores of nonfallers.

CONCLUSIONS

The sample size was small but high levels of attention deficit were identified. Findings suggest a weak or no relationship between attention deficits and falls. Further studies are required to explore the extent of attention deficits post stroke and its impact on balance control and falling.

Attentional deficits in patients with closed head injury: a further study to the discriminative validity of the test of everyday attention

This study aimed to explore the attentional performance of patients with closed head injury (CHI) and to examine the discriminative validity of the Test of Everyday Attention (TEA) in this clinical population. A sample of 21 patients with CHI was recruited for this study. Another sample of matched controls was also recruited for comparison. In addition, other clinical tests of attention and questionnaires on everyday life cognitive failures were also given to the participants during the assessment session. The results showed that patients with CHI exhibited significant differences in most of the TEA subtests, as well as clinical tests of attention, as compared with the matched controls. These findings suggest that the majority of the TEA subtests are able to discriminate out those patients with attentional deficits from the normal population in terms of sustained attention, selective attention, divided attention, and attentional switching.

The structure of normal human attention: The Test of Everyday Attention

A range of tests of everyday attention is described, based on ecologically plausible activities such as searching maps, looking through telephone directories, and listening to lottery number broadcasts. An age-, sex- and IQ-stratified sample of 154 normal participants was given these tests, along with a number of existing tests of attention. The factor structure revealed by this data set matched well contemporary evidence for a set of functionally independent attentional circuits in the brain, and included factors for sustained attention, selective attention, attentional switching and auditory-verbal working memory. The Test of Everyday Attention (TEA), which was developed and standardized on the basis of these subtests, has three parallel forms, high test-retest reliability, and correlates significantly with existing measures of attention. Furthermore, selected subtests successfully discriminate among a number of brain-impaired groups, including closed head injury versus age-matched controls, minimal versus mild Alzheimer's disease, and progressive supranuclear palsy patients versus age-matched controls.