Sub-second timing irregularities in a simple motor task in autism spectrum disorder: Preliminary effects of intermittent light stimulation.

Several authors have contributed extensively to the neurocognitive understanding of timing. In Autism Spectrum Disorder (ASD) on the contrary, internal timing and its functioning is not well understood. In this study, we have adapted a simple finger-tapping motor task, with a timing component, as we aim at understanding whether the processing of time is preserved in this population. We have tested a group of people on the autism spectrum without intellectual disabilities and a control sample recruited from the general population, matched for age, sex, schooling and general cognitive abilities on this task with a learning and testing phase. In the testing phase, we have added two exploratory conditions where participants were exposed to intermittent light stimulation of 4 and 8 Hz. Results show that both in the learning and testing phase, besides troubles in the motor component encountered by the people on the spectrum, their timing component performance was also problematic. This reveals to be especially true for time intervals below the 1 s range, as hypothesized, whereas performance in longer intervals is clearly preserved. It was also observed that the exposure to intermittent light stimulation specifically overcomes the difficulties observed in the autistic group, at the timing components at this millisecond time range. The observed timing difficulties in this group seem to be restricted to the system responsible for the processing of time intervals in the milliseconds range, which helps accommodate disparate findings in the literature.

The Distinctive Pattern of Declarative Memories in Autism Spectrum Disorder: Further Evidence of Episodic Memory Constraints.

This study examines declarative memory retrieval in ASD depending on the availability and access to stored conceptual knowledge. Fifteen autistic participants and a matched control group of 18 typically-developed (TD) volunteers completed a Remember-Know paradigm manipulated by encoding-type (categorical, perceptual) and item-typicality (high-typical, low-typical). The autistic group showed worse and slower recognition and less recollection but equivalent familiarity-based memories compared to TDs. Notably, low-typical items did not improve their memories as they did for TDs, likely due to difficulties in matching low-fit information to the stored schema. Results suggest that memory decline in ASD may derive from the episodic system and its dynamics with the semantic system. These findings may inform interventional strategies for enhancing learning abilities in ASD.

Norms for pictures of proper names: contrasting famous people and well-known places in younger and older adults.

Proper names comprise a class of labels that arbitrarily nominate specific entities, such as people and places. Compared to common nouns, retrieving proper names is more challenging. Thus, they constitute good alternative semantic categories for psycholinguistic and neurocognitive research and intervention. The ability to retrieve proper names is known to decrease with aging. Likewise, their retrieval may differ across their different categories (e.g., people and places) given their specific associated knowledge. Therefore, proper names' stimuli require careful selection due to their high dependence on prior experiences. Notably, normative datasets for pictures of proper names are scarce and hardly have considered the influence of aging and categories. The current study established culturally adapted norms for proper names' pictures (N = 80) from an adult sample (N = 107), in psycholinguistic measures (naming and categorization scores) and evaluative dimensions (fame, familiarity, distinctiveness, arousal, and representational quality). These norms were contrasted across different categories (famous people and well-known places) and age groups (younger and older adults). Additionally, the correlations between all variables were examined. Proper names' pictures were named and categorized above chance and overall rated as familiar, famous, distinctive, and of high representational quality. Age effects were observed across all variables, except familiarity. Category effects were occasionally observed. Finally, the correlations between the psycholinguistic measures and all rated dimensions suggest the relevance of controlling for these dimensions when assessing naming abilities. The current norms provide a relevant aging-adapted dataset that is publicly available for research and intervention purposes.

Disentangling response initiation difficulties from response inhibition in autism spectrum disorder: A sentence-completion task.

It has been proposed that individuals with autism spectrum disorder (ASD) struggle both with response initiation and with response inhibition, both of which are functions of the executive system. Experimental tasks are unlikely pure measures of a single cognitive domain, and in this study we aim at understanding the contributions of response initiation difficulties to possible deficits in inhibitory control in autism. A sample of adults diagnosed with ASD and a control sample participated in this study. To participants it was asked to perform a sentence-completion task with two different condition: Part A-targeting response initiation and Part B-engaging inhibitory processes. Importantly, we have analyzed the B-A latencies that have been proposed for the removal of the response initiation confound effect. Results show that no differences between the groups were found in accuracy measures, either in Part A (ASD: M = 0.78; Controls: M = 0.90) nor Part B (ASD: M = 0.03; Controls: M = 0.02). However, in both conditions autistic participants were significantly slower to respond than the group of participants with typical development (Part A-ASD: M = 2432.5 ms; Controls M = 1078.5 ms; Part B-ASD M = 6758.3 ms; Controls M = 3283.9 ms). Critically, we show that when subtracting the response times of Part A from Part B (B-A latencies) no group differences attributable to inhibitory processes remained (ASD: M = 4325.76; Controls: M = 2205.46). With this study we corroborate the existence of difficulties with response initiation in autism and we question the existence of troubles in inhibition per se.

Is the dolphin a fish? ERP evidence for the impact of typicality during early visual processing in ultra-rapid semantic categorization in autism spectrum disorder.

BACKGROUND: Neurotypical individuals categorize items even during ultra-rapid presentations (20 ms; see Thorpe et al. Nature 381: 520, 1996). In cognitively able autistic adults, these semantic categorization processes may be impaired and/or may require additional time, specifically for the categorization of atypical compared to typical items. Here, we investigated how typicality structures influence ultra-rapid categorization in cognitively able autistic and neurotypical male adults. METHODS: Images representing typical or atypical exemplars of two different categories (food/animals) were presented for 23.5 vs. 82.3 ms (short/long). We analyzed detection rates, reaction times, and the event-related potential components dN150, N1, P2, N2, and P3 for each group. RESULTS: Behavioral results suggest slower and less correct responses to atypical compared to typical images. This typicality effect was larger for the category with less distinct boundaries (food) and observed in both groups. However, electrophysiological data indicate a different time course of typicality effects, suggesting that neurotypical adults categorize atypical images based on simple features (P2), whereas cognitively able autistic adults categorize later, based on arbitrary features of atypical images (P3). CONCLUSIONS: We found evidence that all three factors under investigation - category, typicality, and presentation time - modulated specific aspects of semantic categorization. Additionally, we observed a qualitatively different pattern in the autistic adults, which suggests that they relied on different cognitive processes to complete the task.

Conceptual knowledge modulates memory recognition of common items: The selective role of item-typicality.

This work examines the influence of stored conceptual knowledge (i.e., schema and item-typicality) on conscious memory processes. Specifically, we tested whether item-typicality selectively modulates recollection and familiarity-based memories as a function of the availability of a categorical schema during encoding. Experiment 1 manipulated both encoding type (categorical vs. perceptual) and item-typicality (typical vs. atypical) in a single Remember-Know paradigm. Experiment 2 replicated and extended the previous study with a complementary source-memory task. In both experiments, we observed that typical items led to more Guess responses, while atypical items led to more Remember responses. These findings support the idea that the activation of a congruent categorical schema selectively enhances familiarity-based memories, likely due to the bypassing of the activated mechanisms for novel information. In contrast, atypical items improved recollective-based memories only, suggesting that their lesser fit with the stored prototype might have triggered those novelty processing mechanisms. Moreover, atypical items enhanced memory in the categorical condition for both item recognition and recollection memories only, suggesting an episodic gain due to inconsistency/novelty. The source memory results gave further credence to the argument that "Remember" judgments were based on truly recollective experiences and presented the same interaction between encoding type and item-typicality observed in recollective-based memories. Overall, the results suggest that the supposedly opposite conceptual knowledge effects actually coexist and interact, albeit selectively, in the modulation of recollection and familiarity processes.

RealPic: Picture norms of real-world common items.

Pictures are often used as stimuli in several fields, such as psychology and neuroscience. However, co-occurring image-related properties might impact their processing, emphasizing the importance of validating such materials to guarantee the quality of research and professional practices. This is particularly relevant for pictures of common items because of their wide applicability potential. Normative studies have already been conducted to create and validate such pictures, yet most of them focused on stimulus without naturalistic elements (e.g., line drawings). Norms for real-world pictures of common items are rare, and their normative examination does not always simultaneously assess affective, semantic and perceptive dimensions, namely in the Portuguese context. Real-world pictures constitute pictorial representations of the world with realistic details (e.g., natural color or position), thus improving their ecological validity and their suitability for empirical studies or intervention purposes. Consequently, the establishment of norms for real-world pictures is mandatory for exploring their ecological richness and to uncover their impact across several relevant dimensions. In this study, we established norms for 596 real-world pictures of common items (e.g., tomato, drum) selected from existing databases and distributed into 12 categories. The pictures were evaluated on nine dimensions by a Portuguese sample. The results present the norms by item, by dimension and their correlations as well as cross-cultural analyses. RealPic is a culturally based dataset that offers systematic and flexible standards and is suitable for selecting stimuli while controlling for confounding effects in empirical tasks and interventional applications.

The update of semantic memories in amnestic mild cognitive impairment.

It is still controversial to what extent neocortical consolidated memories are susceptible of change by processes of reconsolidation and transformation throughout experience, and whether the medial temporal lobes are necessary for this update of semantic consolidated memories, as they are for episodic remembering. We hypothesize that patients with amnestic mild cognitive impairment (aMCI) who have deficits in episodic memory may also have difficulties in updating information on added new features of objects. Sixteen participants with aMCI and 20 healthy control participants performed a semantic word-to-picture task, in which they were asked to identify as belonging to a given semantic category NEW objects, that have incorporated novel features, as well as OLD items, semantically and visually SIMILAR items and UNRELATED items. Patients with aMCI made a greater percentage of errors than healthy controls. Participants globally made greater percentages of errors in difficult types of items, namely NEW and SIMILAR, as compared to easier ones, OLD and UNRELATED. Importantly, an item by diagnostic group interaction effect was observed, and post hoc analysis showed that patients with aMCI made a higher percentage of errors than controls in NEW items only. In conclusion, patients with aMCI had a particular difficulty in identifying the NEW items of the word-to-picture task as compared to the control participants, supporting the concept of a flexible and dynamic conceptual knowledge system, involving the update of semantic memories and the integration of new attributes in a constant transformation process, which is impaired in these patients.

A Systematic Review of Normative Studies Using Images of Common Objects.

Common objects comprise living and non-living things people interact with in their daily-lives. Images depicting common objects are extensively used in different fields of research and intervention, such as linguistics, psychology, and education. Nevertheless, their adequate use requires the consideration of several factors (e.g., item-differences, cultural-context and confounding correlated variables), and careful validation procedures. The current study presents a systematic review of the available published norms for images of common objects. A systematic search using PRISMA guidelines indicated that despite their extensive use, the production of norms for such stimuli with adult populations is quite limited (N = 55), particularly for more ecological images, such as photos (N = 14). Among the several dimensions in which the items were assessed, the most commonly referred in our sample were familiarity, visual complexity and name agreement, illustrating some consistency across the reported dimensions while also indicating the limited examination of other potentially relevant dimensions for image processing. The lack of normative studies simultaneously examining affective, perceptive and semantic dimensions was also documented. The number of such normative studies has been increasing in the last years and published in relevant peer-reviewed journals. Moreover, their datasets and norms have been complying with current open science practices. Nevertheless, they are still scarcely cited and replicated in different linguistic and cultural contexts. The current study brings important theoretical contributions by characterizing images of common objects stimuli and their culturally-based norms while highlighting several important features that are likely to be relevant for future stimuli selection and evaluative procedures. The systematic scrutiny of these normative studies is likely to stimulate the production of new, robust and contextually-relevant normative datasets and to provide tools for enhancing the quality of future research and intervention.

We see the orange not the lemon: typicality effects in ultra-rapid categorization in adults with and without autism spectrum disorder.

Semantic meaning can be extracted from pictures presented very briefly, in the order of tens of milliseconds. This ultra-rapid categorization processing appears to respect a coarse-to-fine path where lower level representations of concepts, or more detailed information, need additional time. We question whether variations in the levels of typicality of the target-item would implicate additional processing for correct classification, both in neurotypical (NT) individuals and with autism spectrum disorder (ASD). Previous research in ASD points out that atypical exemplars of a category might be abnormally processed (e.g., longer times in identifying a penguin as a bird), an observation that we further tested with a rapid serial visual presentation (RSVP) task. In this study, we applied a RSVP task, with four different presentation times (13, 27, 50, and 80 ms) and with typical and atypical exemplars to a group of NT individuals and a sample of individuals with ASD. We found, overall, a strong effect of typicality with a higher detection rate for typical items. In addition, we observed a group × typicality × duration interaction. We interpret these findings in the light of the competences of the feedforward sweep of information through our visual system.

Brief Report: Testing the Impairment of Initiation Processes Hypothesis in Autism Spectrum Disorder.

In the present study we aim at providing further evidences for the validity of an initiation processes impairment in autism spectrum disorder (ASD). We applied different verbal fluency tasks designed to decrease or enhance this limitation. A group of high-functioning individuals with ASD and a group of typically developed individuals matched for -age, -IQ and -education, were tested in three verbal fluency tasks. In task 1, we replicated previous findings of an initiation impairment. In tasks 2 and 3, with simple manipulations, we observed that the differences between the groups were respectively eliminated or enhanced. We have not only provided further evidence of impairments in the initiation of a response, but we remarkably show how to circumvent them.

Effects of categorical representation on visuospatial working memory in autism spectrum disorder.

We tested whether individuals with autism spectrum disorder (ASD) are impaired in visuospatial working memory or in the use of the semantic system, in particular in categorization processes at the service of working memory. The performance of high-functioning individuals with ASD (N = 21) in a visual same-different task adapted from Lachmann and van Leeuwen [e.g., Lachmann, T., & van Leeuwen, C. (2010). Representational economy, not processing speed, determines preferred processing strategy of visual patterns. Acta Psychologica, 134(3), 290-298] was compared to those of typically developed controls (N = 25). In a categorical identity task, two successive patterns had to be judged as the same if they belonged to the same equivalence set (cf. Garner, W. R., & Clement, D. E. (1963). Goodness of pattern and pattern uncertainty. Journal of Verbal Learning and Verbal Behavior, 2, 446-452), including all possible rotation and reflection transformations (R&R category), and as different otherwise. In a physical identity task, only patterns that matched in both shape and orientation had to be responded to as the same; all others, including category matches, had to be classified as different. Equivalence sets had different sizes (ESS). Earlier studies showed an increase in reaction time (RT) with increasing ESS and, for the physical identity task, a response conflict for category matching. Both of these effects were interpreted as evidence for a categorical code by which individual patterns are mentally represented. Assuming that categorization processes are deficient in individuals with ASD, we expected no ESS effects and, in the physical identity task, absence of a response conflict for these individuals. In contrast, we found individuals with ASD to be generally as sensitive to ESS as controls, and they showed a response conflict in the physical identity task. Thus, categorical processing seems to be intact in ASD. However, a strong overall group effect was found in RTs: Individuals with ASD are considerably slower than controls.

Preserved Proactive Interference in Autism Spectrum Disorder.

In this study, we aimed to evaluate further the functioning and structuring of the semantic system in autism spectrum disorders (ASD). We analyzed the performance of 19 high-functioning young adults with ASD and a group of 20 age-, verbal IQ- and education-matched individuals with the Proactive Interference (PI) Paradigm to evaluate semantic functioning in ASD (Experiment 1). In Experiment 2, we analyzed the performances of both groups in a PI paradigm with manipulation of the level of typicality. In both experiments, we observed significant effects of trial and group but no trial by group interactions, which we interpreted as robust evidence of preserved PI (build up effect) that indicated the preservation of semantic mechanisms of encoding and retrieval.

Verbal fluency as a function of time in autism spectrum disorder: An impairment of initiation processes?

In the present study, we aimed to evaluate the hypothesis that the reported discrepancy in the performance of verbal fluency in individuals with autism spectrum disorder (ASD), characterized by an overall word productivity impairment with normal clustering and switching abilities, may be due to an initiation deficit. In the present study, we evaluated the temporal dynamics of both letter and semantic verbal fluency tasks in a sample of 20 young adults with high-functioning ASD compared with a sample of 20 gender-, age-, education-, and verbal-IQ-matched participants. We first compared both the word productivity and the qualitative analysis of clustering and switching abilities during the entire task to replicate the discrepancy reported in the literature. Importantly, we next analyzed both word productivity and clustering and switching abilities in two time intervals (0-30 s and 31-60 s), as it was our primary interest to evaluate the functioning of the initial component of word retrieval. Directly supporting the idea that the discrepancy found between an impairment in global word productivity combined with normal clustering and switching strategies is due to an activation and initiation deficit, we observed an abnormal performance for the ASD group in the first time period only. We interpreted these results to be preliminary findings of deficits in initiation processes in ASD.

Preserved imitation of known gestures in children with high-functioning autism.

It has been suggested that children with autism are particularly deficient at imitating novel gestures or gestures without goals. In the present study, we asked high-functioning autistic children and age-matched typically developing children to imitate several types of gestures that could be either already known or novel to them. Known gestures either conveyed a communicative meaning (i.e., intransitive) or involved the use of objects (i.e., transitive). We observed a significant interaction between gesture type and group of participants, with children with autism performing known gestures better than novel gestures. However, imitation of intransitive and transitive gestures did not differ across groups. These findings are discussed in light of a dual-route model for action imitation.

Understanding and imitating unfamiliar actions: distinct underlying mechanisms.

The human "mirror neuron system" has been proposed to be the neural substrate that underlies understanding and, possibly, imitating actions. However, since the brain activity with mirror properties seems insufficient to provide a good description for imitation of actions outside one's own repertoire, the existence of supplementary processes has been proposed. Moreover, it is unclear whether action observation requires the same neural mechanisms as the explicit access to their meaning. The aim of this study was two-fold as we investigated whether action observation requires different processes depending on 1) whether the ultimate goal is to imitate or understand the presented actions and 2) whether the to-be-imitated actions are familiar or unfamiliar to the subject. Participants were presented with both meaningful familiar actions and meaningless unfamiliar actions that they had to either imitate or discriminate later. Event-related Potentials were used as differences in brain activity could have been masked by the use of other techniques with lower temporal resolution. In the imitation task, a sustained left frontal negativity was more pronounced for meaningless actions than for meaningful ones, starting from an early time-window. Conversely, observing unfamiliar versus familiar actions with the intention of discriminating them led to marked differences over right centro-posterior scalp regions, in both middle and latest time-windows. These findings suggest that action imitation and action understanding may be sustained by dissociable mechanisms: while imitation of unfamiliar actions activates left frontal processes, that are likely to be related to learning mechanisms, action understanding involves dedicated operations which probably require right posterior regions, consistent with their involvement in social interactions.

Neuropsychological perspectives on the mechanisms of imitation.

Cognitive neuroscientists have contributed to the understanding of imitation according to their expertise. Neuropsychologists first established over a century ago that lesions to the left hemisphere of right-handed individuals lead to a dramatic reduction of their ability to imitate gestures. In contrast, after frontal lobe damage, patients may experience severe difficulties in inhibiting their imitative tendency. These findings suggested that our tendency to imitate is mostly sustained by the left hemisphere and that we normally manage successfully to keep it under control. Neuropsychologists went on investigating other aspects of gesture imitation. These include the existence of putative mechanisms involved in imitating different types of gestures (e.g. meaningful and meaningless or transitive and intransitive), the strategic control over these mechanisms and whether there are differences in imitation depending on the action goal or the body part used. Based on neuropsychological findings, some cognitive models of gesture imitation have been forwarded, the most influential of which will be reviewed here. In particular, reference will be made to the dual route model and to accounts that associate the imitative deficit to putative degraded body representations.

Imitation of transitive and intransitive actions in healthy individuals.

A handful of patients have been described as being impaired in performing transitive gestures, despite being still able to perform intransitive gestures. This impairment need not be explained by assuming different mechanisms; rather, it can be due to transitive actions being more difficult. In this study we tested whether neurologically healthy participants had greater difficulties in imitating transitive actions with respect to intransitive actions. Consistent with the prediction, subjects imitated intransitive better than transitive gestures. The ease of imitation of intransitive actions supports the complexity account of apraxic impairments.