Successful interaction within the environment is contingent upon one's ability to accurately perceive the extent over which they can successfully perform actions, known as action boundaries. Healthy young adults are accurate in estimating their action boundaries and can flexibly update them to accommodate stable changes in their action capabilities. However, there are conditions in which motor abilities are subject to variability over time such as in Parkinson's disease (PD). PD impairs the ability to perform actions and can lead to variability in perceptual-motor experience, but the effect on the perceptions of their action boundaries remains unknown. This study investigated the influence of altered perceptual-motor experience during PD, on the perceptions of action boundaries for reaching, grasping, and aperture passing. Thirty participants with mild-to-moderate idiopathic PD and 26 healthy older adults provided estimates of their reaching, grasping, and aperture-passing ability. Participants' estimates were compared with their actual capabilities. There was no evidence that individuals with PD's perceptions were less accurate than those of healthy controls. Furthermore, there was some evidence for more conservative estimates than seen in young healthy adults in reaching (both groups) and aperture passing (PD group). This suggests that the ability to judge action capabilities is preserved in mild to moderate PD.
Abstract Selective attention to a sensory modality has been observed experimentally in studies of the modality-shift effect – a relative performance benefit for targets preceded by a target in the same modality, compared to a different modality. Differences in selective attention are commonly observed in autism and we investigated whether exogenous (automatic) shift costs between modalities are increased. Autistic adults and neurotypical controls made speeded discrimination responses to simple visual, tactile and auditory targets. Shift costs were observed for each target modality in participant response times and were largest for auditory targets, reflective of fast responses on auditory repeat trials. Critically, shift costs were similar between the groups. However, integrating speed and accuracy data using drift-diffusion modelling revealed that shift costs in drift rates (reflecting the quality of information extracted from the stimulus) were reduced for autistic participants compared with neurotypicals. It may be that, unlike neurotypicals, there is little difference between attention within and between sensory modalities for autistic people. This finding also highlights the benefit of combining reaction time and accuracy data using decision models to better characterise selective attention in autism.
James Parkinson was the first to report six cases with symptoms of a disease he called ‘paralysis agitans’ in 1817, later to be renamed Parkinson's disease by Jean-Marie Charcot 50 or so years later. In Parkinson's 66 page work, titled An Essay on the Shaking Palsy, he describes the insidious onset and progressive nature of the increasing immobility; and his astute description of its clinical presentation at the time ‘(the) involuntary tremulous motion, with lessened muscular power, in parts not in action and even when supported; with a propensity to bend the trunk forward…’ has a clear overlap with the typical description of Parkinson's disease that is in use today, bradykinesia, or slowed movement, tremor, and rigidity (Gleb, Oliver, & Gilman, 1999). James Parkinson also noted of ‘the senses and intellects being uninjured’, a view we now know to be far from being accurate. The last 10–20 years have witnessed a sharp rise in the number of publications on cognition in Parkinson's disease. One reason for this increase is the availability of exciting new technology such as high-resolution structural MRI investigations of white and grey matter integrity, functional MRI examining changes in neural activation, and PET imaging investigating metabolic and neurochemical changes. These have led to an improved understanding of the brain regions or networks that might be dysfunctional and contribute to changes in cognition, notably action representation, memory and executive processes, behaviour, such as apathy and impulse control disorders, and phenotype. Another contributory factor is the growing awareness of the complex interaction between genetic polymorphisms (catechol-O-methyltransferase, COMT), dopaminergic state, and the development of abnormal behaviours. Moreover, moving beyond simple accounts of the nature and extent of cognitive impairments in Parkinson's disease, there has been a greater focus on and awareness of the implications for clinical management and real-life functioning for people with Parkinson's disease. In addition to these important aspects, understanding the cognitive effects of Parkinson's disease can illuminate normal function. Indeed, there has been growing interest in the cognitive neuroscience literature on the role of dopamine in reward, learning, and decision-making. This special issue covers several of the different paradigms that have been brought to bear on cognition and Parkinson's disease including psychiatry and clinical psychology, cognitive neuropsychology and cognitive neuroscience. The special issue is organized broadly thematically, but there is no strict organization as interesting new ideas will arise from the convergence of empirical and review articles. The first set of three papers present new research on memory in medicated patients and, moreover, illustrate the continued importance of cognitive neuropsychological research in furthering knowledge of the effects of Parkinson's disease on cognition. Some of the new insights provided in these papers include Costa, Peppe, Caltagirone, and Carlesimo's (2013) evidence that the already accepted general prospective memory deficit in Parkinson's disease is not modulated by the manipulation of retrospective memory load and complexity of the ongoing prospective memory element. This is a particularly timely paper as it challenges the prevailing view that retrospective memory processes do not interfere with prospective memory deficits in Parkinson's disease. Souchay and Smith (2013) examine autobiographical memory retrieval in Parkinson's disease, using an unusual and innovative design with patients being initially asked to retrieve as many memories as possible using the autobiographical fluency task. Later recall of their memories is then examined using 3 phases – free recall, lifetime period cued recall, and self-generated titles cued recall. Remaining with the theme of memory, Davidson, Cook, McGhan, Bouchard, and Camicioli (2013) combined a series of investigations of item and source memory, executive function, and structural imaging of the hippocampus in young and older healthy adults, and Parkinson's disease patients. Their findings are introduced in the framework of Parkinson's disease being underlain by speeded ageing, which is hypothesized to be caused by deterioration of prefrontal functioning. The next set of four review articles in this special issue provide timely overviews of the state of knowledge of executive functions, action representation, and the various aspects of decision making that lead to impulsivity and impulse control disorders in Parkinson's disease. The topics of these reviews are of considerable importance, given the considerable impact changes in these processes can have on patients’ daily functioning. In the first paper, Dirnberger and Jahanshahi (2013) provide a comprehensive overview of the current state of knowledge of executive dysfunction in Parkinson's disease, the classical tests used to assess executive dysfunction together with their limitations. A welcome addition to their review is the authors’ inclusion of heterogeneity in the Parkinson's disease phenotype, postural instability, gait, freezing, apathy, and olfaction. In the second article, Christopher and Strafella (2013) bring together recent structural and functional brain imaging studies, which have led to an improved understanding of the brain regions or networks associated with executive dysfunction in Parkinson's disease without dementia and the newly emerging concept of mild cognitive impairment in Parkinson's disease. One of the exciting pieces of new research reviewed is the imaging study by Rowe et al. (2010) that found that the COMT genotype influenced neural structure as well as function in some brain areas. In the third review paper, Poliakoff (2013) tackles the topic of action representation in Parkinson's disease and considers the implications of Parkinson's disease on imagining, observing, and naming actions for understanding both the symptoms of Parkinson's disease and the cognitive representation of actions in the healthy system. The fourth review by Sinha, Manohar, and Husain (2013) adopts a conceptual approach to impulsivity, apathy, and underlying dopaminergic state. The authors fractionate decision making into various cognitive aspects, which entail dopaminergic modulation along singular axes, and review the consequences of changes of dopamine state with apathy and impulsivity as two extremes on a multi-faceted spectrum of decision-making processes. One of the important conclusions to come out of this review is that apathy probably results from a dopamine deficit, whereas impulse control disorders can be seen as a result of a hyperdopaminergic state. The next three papers consider, in different ways, the impact of dopaminergic state on cognition and behaviour. Shepherd, Edelstyn, Mayes, and Ellis (2013) focus on memory and show, for the first time, that when medicated with a particular dopamine agonist (pramipexole), patients show a selective decline in the recollection of episodic details compared with matched patients on a different dopamine agonist (ropinirole) and healthy controls. This study picks up the more general theme already considered in previous articles of phenotypic heterogeneity in Parkinson's disease, and the potential interaction between phenotype and medication. Leroi et al.'s (2013) study of executive function in patients with and without impulse control disorders suggests that pharmacological differences in dopaminergic state may affect impulsive decision making in impulse control disorders, and furthermore, that genotypic differences in dopaminergic state may differentially affect aspects of attention, verbal fluency, and perseveration. The final paper in this special issue by Barnes, Connelly, Boubert, and Maravic (2013) provides insights into the role of cognitive behavioural approaches when dealing with visual hallucinations. This paper reports the results of a questionnaire survey of patients attending a local Parkinson's disease support group. Respondents were divided into those who have frequent visual hallucinations and those who did not have visual hallucinations. The former group was followed up with a further questionnaire to determine what spontaneous coping strategies participants used to deal with their hallucinations. One aspect of particular interest is the qualitative description of coping strategies and the potential for the findings to form the basis for developing therapeutic interventions. Versions of the articles included in this special issue by Barnes, Husain, Poliakoff, Leroi, Dimberger, and Shepherd were first delivered at a Parkinson's UK-sponsored symposium at the British Psychological Society Cognitive Section Meeting in 2011, whereas the remaining articles by Costa, Christopher, Davidson, and Souchay came from a call for papers and invited submissions over the past 18 months. This special issue offers a set of 10 engaging papers, each of which addresses in its own way the theme of this issue: Cognition and Parkinson's disease. We thank the Journal of Neuropsychology editorial team for their commitment to the project over the past 18 months, the many reviewers whose individual work remains unacknowledged, and finally, and most importantly, the researchers whose work is published here.
Abstract Action perception, execution, and imagery share motor-cognitive processes. Given prevalent motor coordination difficulties in autism, the processes of action perception and imagery may also be altered. This study investigated whether autistic adults can engage in motor imagery by testing differences in executing, perceiving, and imagining hand movements between autistic and non-autistic adults. Twenty autistic individuals and twenty age- and IQ-matched controls completed execution, imagination, and perception tasks using a Fitts’ Law paradigm in an online session. For the execution and imagination tasks, participants performed or imagined making aiming movements between two targets. For the action perception task, participants indicated whether they could perform as accurately as the movements in presented videos. Target size and distance were manipulated into three difficulty levels and systematically varied across all tasks. Results showed a similar Fitts’ Law relationship for both groups, with significant positive correlations between movement times and difficulty level. Movement times were longest in the imagination task and shortest in the perception task for both groups. These findings suggest motor imagery processes are relatively intact in autistic adults, opening the possibility of using motor imagery as a therapy for motor coordination difficulties in autistic individuals.
Inhibition of return (IOR) is an attentional effect that has been much researched in the spatial domain, whereby people are slower to respond to stimuli presented in a previously attended location. Recently, Chao (2010) reported that participants were slower to respond to a negative schematic facial target compared with a positive facial target if they had previously viewed a cue with a negative expression, which he interpreted as IOR in the purely emotional domain. That is, once their attention is drawn away, people are slower to reattend to negative emotions. Here, we investigated whether this effect could be observed when controlling for the valence of the target and when using a more naturalistic human facial expression as a cue. We replicated Chao's findings using real face cues, observing slower responses for negative cues followed by negative versus positive targets, and faster responses for positive cues followed by positive versus negative targets. However, our reanalysis indicates that these effects are better accounted for by the valence (positive/negative) of the target, with responses being slower to negative compared with positive facial expressions regardless of the preceding cue. In conclusion, orienting in the emotional domain could not be measured using a cue-target task, as the effect of responding to emotional targets eclipsed any potential emotional cuing effect.
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