Action Fluency in Parkinson’s Disease: A Mini-Review and Viewpoint

Increasing evidence shows that the typical motor symptoms of Parkinson’s disease (PD) are often accompanied, if not preceded, by cognitive dysfunctions that are potentially linked to further complications of the disease. Notably, these cognitive dysfunctions appear to have a significant impact in the domain of action processing, as indicated by specific impairments for action-related stimuli in general, and verbs in particular. In this mini-review, we focus on the use of the action fluency test as a tool to investigate action processing, in PD patients. We discuss the current results within the embodied cognition framework and in relation to general action-related impairments in PD, while also providing an outlook on open issues and possible avenues for future research. We argue that jointly addressing action semantic processing and motor dysfunctions in PD patients could pave the way to interventions where the motor deficits are addressed to improve both motor and communicative skills since the early disease stages, with a likely significant impact on quality of life.

Strong conceptual ability reduces the effect of lexical impairments on verb retrieval in aphasia

Verb-retrieval impairments are pervasive deficits that can negatively impact communicative function for individuals living with aphasia. Unfortunately, the neurocognitive basis of these deficits remains poorly understood. One open question is the degree to which verb-retrieval impairments might be rooted in lexical- versus conceptual-processing deficits. These deficits can be co-present and correlated in people with aphasia, but they have also been found to be dissociated in patients with a variety of acquired brain injuries. This study examined the degree to which conceptual versus lexical action-processing abilities are impaired and may contribute to verb-retrieval impairments in adults with chronic aphasia due to left-hemisphere stroke. The results indicate that conceptual action processing can be impaired in aphasia and may contribute to verb-retrieval impairments. Furthermore, relatively unimpaired conceptual processing can ameliorate the influence of lexical impairments on verb-retrieval impairments. These findings are consistent with models in which conceptual representations play a key role in language processing and may be leveraged to improve verb retrieval in adults with chronic aphasia.

Motoric Understanding and Aesthetic Appreciation

Standard philosophical studies on picture perception usually investigated the peculiar nature of pictorial experience and the way aesthetic appreciation can be generated during this experience. Recently, however, the philosophical literature has also focused on a new aspect of picture perception: the possible involvement that the visual states related to action processing may actually play in pictorial experience. But this role has been studied only in relation to the understanding of the nature of pictorial experience, qua visual experience. This paper offers some preliminar speculation, which may guide future research, on the role of action in aesthetic appreciation of pictures.

Implicit agency is related to gamma power changes in an automatic imitation task

Often we have a feeling that we can control effects in the external world through our actions. The role of action processing associated with this implicit form of agency is still not clear. In this study, we used automatic imitation and electroencephalography to investigate neural oscillations associated with action processing and its possible contribution to implicit agency. Brain activity was recorded while participants performed actions (congruent or incongruent with a displayed finger movement) which subsequently triggered an outcome (a tone). We used a time estimation task to measure intentional binding (an index of implicit agency). We observed a decrease of alpha, beta and gamma power for congruent compared to incongruent actions and increased theta power for incongruent compared to congruent actions. Crucially, participants who showed greater intentional binding for congruent versus incongruent actions also presented greater gamma power differences. Alpha, beta and theta power were modulated by congruency but were unrelated to intentional binding. Our study suggests that an increased implicit agency for facilitated actions is associated with changes in gamma power. Our study also contributes to a characterization of neural oscillations in automatic imitation.

Behavioral and Neural Representations en route to Intuitive Action Understanding

When we observe another person's actions, we process many kinds of information -- from how their body moves to the intention behind their movements. What kinds of information underlie our intuitive understanding about how similar actions are to each other? To address this question, we measured the intuitive similarities among a large set of everyday action videos using multi-arrangement experiments, then used a modeling approach to predict this intuitive similarity space along three hypothesized properties. We found that similarity in the actors' inferred goals predicted the intuitive similarity judgments the best, followed by similarity in the actors' movements, with little contribution from the videos' visual appearance. In opportunistic fMRI analyses assessing brain-behavior correlations, we found evidence for an action processing hierarchy, in which these three kinds of action similarities are reflected in the structure of brain responses along a posterior-to-anterior gradient on the lateral surface of the visual cortex. Altogether, this work joins existing literature suggesting that humans are naturally tuned to process others' intentions, and that the visuo-motor cortex computes the perceptual precursors of the higher-level representations over which intuitive action perception operates.

The prehistory of speech and language is revealed in brain damage

The aim of this paper is to develop further the idea that symptoms that emerge in speech and language processing following brain damage can make a contribution to discussions of the early evolution of language. These diverse impairments are called aphasia, and this paper proposes that the recovery of a non-fluent aphasia syndrome following stroke could provide insights into the course of the pre-history of human language evolution. The observable symptoms emerge during recovery, crucially enabled by (dis)inhibition in parallel with a range of impairments in action processing (apraxias), including apraxia of speech. They are underpinned by changes in cortical and subcortical status following brain damage. It is proposed that the observed recovery mimics ontogenic and phylogenic processes in human speech and language. The arguments put forward provide insights tending to support the motor-gestural model of speech and language evolution. This article is part of the theme issue ‘Reconstructing prehistoric languages’.

Confidence in action: differences between perceived accuracy of decision and motor response

Each of our decisions is associated with a degree of confidence. This confidence can change once we have acted as we might start doubting our choice or even become convinced that we made a mistake. In this study, we explore the relations between action and our confidence that our decision was correct or erroneous. Fifty-six volunteers took part in a perceptual decision task in which their decisions could either lead to action or not. At the end of each trial, participants rated their confidence that their decision was correct, or they reported that they had made an error. The main results showed that when given after a response, confidence ratings were higher and more strongly related to decision accuracy, and post-response reports of errors more often indicated actual errors. The results support the view that error awareness and confidence might be partially based on post-action processing.