Sarah E. MacPherson

Cognitive reserve and cognitive performance of patients with focal frontal lesions

ABSTRACT The Cognitive reserve (CR) hypothesis was put forward to account for the variability in cognitive performance of patients with similar degrees of brain pathology. Compensatory neural activity within the frontal lobes has often been associated with CR. For the first time we investigated the independent effects of two CR proxies, education and NART IQ, on measures of executive function, fluid intelligence, speed of information processing, verbal short term memory (vSTM), naming, and perception in a sample of 86 patients with focal, unilateral frontal lesions and 142 healthy controls. We fitted multiple linear regression models for each of the cognitive measures and found that only NART IQ predicted executive and naming performance. Neither education nor NART IQ predicted performance on fluid intelligence, processing speed, vSTM or perceptual abilities. Education and NART IQ did not modify the effect of lesion severity on cognitive impairment. We also found that age significantly predicted performance on executive tests and the majority of our other cognitive measures, except vSTM and GNT. Age was the only predictor for fluid intelligence. This latter finding suggests that age plays a role in executive performance over and above the contribution of CR proxies in patients with focal frontal lesions. Overall, our results suggest that the CR proxies do not appear to modify the relationship between cognitive impairment and frontal lesions. HIGHLIGHTSEffect of cognitive reserve (CR) proxies in focal unilateral lesions.NART IQ accounts for a larger proportion of variance in executive and naming skills.Age predicts performance on executive, fluid intelligence, speed and perception tests.Education and NART IQ did not modify the effect of lesion severity on cognitive impairment.

Processing speed and the relationship between Trail Making Test-B performance, cortical thinning and white matter microstructure in older adults

Part B of the Trail Making Test (TMT-B) is widely used as a quick and easy to administer measure of executive dysfunction. The current study investigated the relationships between TMT-B performance, brain volumes, cortical thickness and white matter water diffusion characteristics in a large sample of older participants, before and after controlling for processing speed. Four hundred and eleven healthy, community-dwelling older adults who were all born in 1936 were assessed on TMT-B, 5 tests of processing speed, and provided contemporaneous structural and diffusion MRI data. Significant relationships were found between slower TMT-B completion times and thinner cortex in the frontal, temporal and inferior parietal regions as well as the Sylvian fissure/insula. Slower TMT-B completion time was also significantly associated with poorer white matter microstructure of the left anterior thalamic radiation, and the right uncinate fasciculus. The majority of these associations were markedly attenuated when additionally controlling for processing speed. These data suggest that individual differences in processing speed contribute to the associations between TMT-B completion time and the grey and white matter structure of older adults.

Associations between hippocampal morphology, diffusion characteristics, and salivary cortisol in older men

Highlights • Elevated cortisol does not appear to be associated with regional variations in hippocampal shape.• Novel shape morphology analysis applied to study possible effect of cortisol on hippocampus.• Mean diffusivity in hippocampus is associated with reactive cortisol slope in older men.

Theory of mind and the Ultimatum Game in healthy adult aging

ABSTRACT Background: The Ultimatum Game assesses decision-making involved in cooperative interactions with others. However, little is known about the role that the ability to understand other people’s intentions plays in these interactions. Methods: This study examined performance on the Ultimatum Game and theory of mind (ToM) tasks in younger and older adults. Results: Age differences were not found on the ToM tasks, and a lack of variability in performance prevented analyses of the relationships between performance on the Ultimatum Game and ToM. However, age differences were found on the Ultimatum Game, with older adults accepting more unfair offers. Yet, the two age groups did not differ in their appreciation of fairness, as assessed using subjective fairness ratings. Conclusions: These findings suggest that older adults are more rational in their behavior, accepting unfair offers even when they know they are unfair, as it is in their self-interest to accept small monetary values rather than nothing at all.

The cognitive neuroscience of source memory: Moving the ball forward

Think about the last time you had a sudden insight about a new data set. Without consulting others, what made you think that “Aha!” moment represented a unique idea you generated “on the spot” rather than the remembrance of a great idea previously offered by a colleague in a hallway discussion of the data? More generally, how do we determine where a mental experience comes from? Source memory is an umbrella term that refers to the processes involved in encoding, organizing, selectively reviving (e.g., reactivating, retrieving), cumulating, evaluating (e.g., weighting, comparing to expectations), and attributing (i.e., making inferences [judgments, decisions] about the source of) information during remembering. The concept encompasses, but is broader than, the idea of context memory (for reviews and further discussions see, e.g., Johnson, Hashtroudi, & Lindsay, 1993, 2008; Mitchell & Johnson, 2000). We routinely use these processes to solve everyday cognitive puzzles like the one described above or, for example, when remembering which U.S. Presidential candidate offered the tax plan you really like, remembering which pocket of your briefcase you put your keys in, deciding whether you turned off the stove or simply thought about doing so (Brandt, Bergstr€ om, Buda, Henson, & Simons, 2014), or determining whether you actually saw a video of an important news event or only imagined it (Ost, Vrij, Costall, & Bull, 2002). Trivial errors in source memory can be inconvenient, and perhaps a little embarrassing, for example, raving about a new restaurant to a friend when she was the one who told you about it in the first place. But, source errors can sometimes have much more serious consequences, for example, remembering that you took your heart medicine when you only thought about doing so, mistaking a memory of a dream of being sexually abused as a child for amemory of something that actually happened to you (see, e.g., Lindsay, 2014; for a review), believing that a voice is coming from an external source rather than ones own thinking (e.g., hallucinations, see, e.g., Johnson & Raye, 2000; Woodward & Menon, 2013 for reviews), or falsely confessing to having committed a crime (e.g., Shaw & Porter, 2015; see Henkel & Coffman, 2004 for a review). Our understanding of the brain mechanisms associated with source memory has been rapidly accelerating over the past few decades (see, e.g., MacPherson, 2015; Mitchell & Johnson, 2009; Mitchell, 2016 for reviews). Refinements of cognitive theory and advancements in neuroscientific methodology (including imaging techniques and analysis approaches) are affording exciting synergistic progress. This special issue presents some of that progress. We set out to compile cutting-edge papers highlighting how behavioral, patient, and neuroimaging research is advancing our understanding of the brain mechanisms involved in source

Cognitive Estimation in Non-demented Parkinson's Disease

ObjectivenThe Cognitive Estimation Test (CET) is widely used in clinical and research settings to assess the ability to produce reasonable estimates to items that individuals would not know that the exact answer (e.g., How fast do race horses run?). We examined the performance of non-demented Parkinsons disease (PD) patients on the CET, because previous studies reported heterogeneous results about possible cognitive estimation impairments in PD. We also examined whether PD patients improve their performance if given the chance to reconsider their initial CET responses.nnnMethodsnThirty non-demented idiopathic PD patients and 30 healthy controls matched in age, gender and years of education performed the two parallel forms of Italian CET. The estimation scores for initial and final responses as well as the number of times individuals changed their answers were examined. Additional neuropsychological tests, evaluating intellectual, frontal executive, speed of processing, naming and arithmetical abilities, were also administered.nnnResultsnThe PD group were not significantly poorer than healthy controls at estimating the answers to items on either CET versions. Moreover, PD patients did not significantly differ in their initial and final responses or number of response changes. Performance on the CET was significantly related to performance on a global measure of executive function, processing speed and arithmetic. However, PD patients were impaired compared to controls on the component involving mainly, but not exclusively, length-related estimations.nnnConclusionsnNon-demented PD patients have mild impairments in cognitive estimation ability, which may depend on the estimations they are required to provide.

The Edinburgh Social Cognition Test (ESCoT): Examining the effects of age on a new measure of theory of mind and social norm understanding

Current measures of social cognition have shown inconsistent findings regarding the effects of healthy aging. Moreover, no tests are currently available that allow clinicians and researchers to examine cognitive and affective theory of mind (ToM) and understanding of social norms within the same test. To address these limitations, we present the Edinburgh Social Cognition Test (ESCoT) which assesses cognitive and affective ToM and inter- and intrapersonal understanding of social norms. We examined the effects of age, measures of intelligence and the Broader Autism Phenotype (BAP) on the ESCoT and established tests of social cognition. Additionally, we investigated the convergent validity of the ESCoT based on traditional social cognition measures. The ESCoT was administered alongside Reading the Mind in Films (RMF), Reading the Mind in Eyes (RME), Judgement of Preference and Social Norm Questionnaire to 91 participants (30 aged 18–35 years, 30 aged 45–60 years and 31 aged 65–85 years). Poorer performance on the cognitive and affective ToM ESCoT subtests were predicted by increasing age. The affective ToM ESCoT subtest and RMF were predicted by gender, where being female predicted better performance. Unlike the ESCoT, better performance on the RMF was predicted by higher verbal comprehension and perceptual reasoning abilities, while better performance on the RME was predicted by higher verbal comprehension scores. Lower scores on inter-and intrapersonal understanding of social norms were both predicted by the presence of more autism-like traits while poorer interpersonal understanding of social norms performance was predicted by increasing age. These findings show that the ESCoT is a useful measure of social cognition and, unlike established tests of social cognition, performance is not predicted by measures of verbal comprehension and perceptual reasoning. This is particularly valuable to obtain an accurate assessment of the influence of age on our social cognitive abilities.

The Influence of Fluid Intelligence, Executive Functions and Premorbid Intelligence on Memory in Frontal Patients

Objective: It is commonly thought that memory deficits in frontal patients are a result of impairments in executive functions which impact upon storage and retrieval processes. Yet, few studies have specifically examined the relationship between memory performance and executive functions in frontal patients. Furthermore, the contribution of more general cognitive processes such as fluid intelligence and demographic factors such as age, education, and premorbid intelligence has not been considered. Method: Our study examined the relationship between recall and recognition memory and performance on measures of fluid intelligence, executive functions and premorbid intelligence in 39 frontal patients and 46 healthy controls. Results: Recall memory impairments in frontal patients were strongly correlated with fluid intelligence, executive functions and premorbid intelligence. These factors were all found to be independent predictors of recall performance, with fluid intelligence being the strongest predictor. In contrast, recognition memory impairments were not related to any of these factors. Furthermore, age and education were not significantly correlated with either recall or recognition memory measures. Conclusion: Our findings show that recall memory in frontal patients was related to fluid intelligence, executive functions and premorbid intelligence. In contrast, recognition memory was not. These findings suggest that recall and recognition memory deficits following frontal injury arise from separable cognitive factors. Recognition memory tests may be more useful when assessing memory functions in frontal patients.

Definition: Dual-tasking and multitasking

Dual-tasking is the ability to perform two tasks simultaneously. Dual-tasking measures a component of executive function as participants are required to coordinate their attention to both tasks while they are being performed. Dualtasking is differentiated from serial multitasking paradigms where individuals focus on and perform one task at a time, switching between those tasks. However, concurrent multitasking can be used synonymously with dual-tasking as the tasks are performed in parallel (e.g., talking on the phone while stirring a pan on the stove). In dual-tasking, the difference between performance on each of the tasks performed individually and simultaneously provides an index of dual-tasking cost. To accurately assess dual-tasking, the chosen tasks should not tap the same input modalities or response mechanisms (e.g., manual versus oral responses). Additionally, the two tasks should involve different cognitive contents (e.g., visual tracking with a word or digit task) to ensure the tasks do not interfere with one another. The tasks administered during dual task assessment may include digit, word or pattern recall, various monitoring tasks (e.g., box crossing or E-checking), tracking a target or continuous choice reaction-time tasks. Real life behaviours such as walking and talking have also been used. To provide a dual-task measure of the ability to coordinate attention between the two tasks, single-task performance is often titrated or calibrated for each participants own single-task ability. This can be done by assessing and administering the tasks at an individuals own span or single-task ability levels or statistically controlling for single-task performance. Dual-tasking can be measured in terms of accuracy or response times with dual-task costs reflecting less accurate or slower performance when the two tasks are performed together compared to individually. Some studies consider dual task costs on the primary but not the secondary task while other studies consider any trade-off between the two tasks and assess overall dual task costs. Dual-task impairments are reported in Alzheimers disease, where performance declines with disease progression, but deficits have also been found in Parkinsons disease, vascular dementia and traumatic brain injury. However, dual-task impairments are not found in depression and less consistently in mild cognitive impairment and healthy aging, especially when the tasks are titrated for individual ability levels.

Cognitive estimation: Performance of patients with focal frontal and posterior lesions

ABSTRACT The Cognitive Estimation Test (CET) is a widely used test to investigate estimation abilities requiring complex processes such as reasoning, the development and application of appropriate strategies, response plausibility checking as well as general knowledge and numeracy (e.g., Shallice and Evans, 1978; MacPherson et al., 2014). Thus far, it remains unknown whether the CET is both sensitive and specific to frontal lobe dysfunction. Neuroimaging techniques may not represent a useful methodology for answering this question since the complex processes involved are likely to be associated with a large network of brain regions, some of which are not functionally necessary to successfully carry out the CET. Instead, neuropsychological studies may represent a more promising investigation tool for identifying the brain areas necessary for CET performance. We recently developed two new versions of the CET (CET‐A and CET‐B; MacPherson et al., 2014). We investigated the overall performance and conducted an error analysis on CET‐A in patients with focal, unilateral, frontal (n = 38) or posterior (n = 22) lesions and healthy controls (n = 39). We found that frontal patients’ performance was impaired compared to healthy controls on CET. We also found that frontal patients generated significantly poorer estimates than posterior patients on CET‐A. This could not be explained by impairments in fluid intelligence. The error analyses suggested that for CET‐A, extreme and very extreme responses are impaired following frontal lobe damage. However, only very extreme responses are significantly more impaired following frontal lobe than posterior damage and so represent a measure restricted to frontal “executive” impairment, in addition to overall CET performance. HIGHLIGHTSThe prefrontal cortex (PFC) is critical for performance on the CET.CET‐A overall scores and very extreme responses are affected and restricted to PFC damage.CET‐A is an ‘executive’ task for which impairment cannot be accounted by fluid intelligence.