David A. Gonzalez

The role of vision for online control of manual aiming movements in persons with autism spectrum disorders

Recent studies suggest motor skills are not entirely spared in individuals with an autism spectrum disorder (ASD). Previous reports demonstrated that young adults with ASD were able to land accurately on a target despite increased temporal and spatial variability during their movement. This study explored how a group of adolescents and young adults with an ASD used vision and proprioception to land successfully on one of two targets. Participants performed eye movements and/or manual reaching movements, either with or without vision. Although eye movements were executed in a similar timeframe, participants with ASD took longer to plan and execute manual reaching movements. They also exhibited significantly greater variability during eye and hand movements, but were able to land on the target regardless of the vision condition. In general, individuals with autism used vision and proprioception. However, they took considerably more time to perform movements that required greater visual-proprioceptive integration.

Extending end-state comfort effect: Do we consider the beginning state comfort of another?

Sharing a drink or passing a tool to another person is frequently done in our daily lives. However, a second thought is rarely given about how the object should be handed; instead we pay attention to other factors (e.g., the company). This interaction (handing a tool to someone) is interesting, since it may give insight to how motor intentions are predicted. Research has demonstrated that individuals exhibit an end-state comfort effect when manipulating objects, and it is of interest to determine how this is applied to a joint-action paradigm. The purpose of this experiment was to determine if participants would anticipate the confederates postural requirements and pass tools in a manner that allowed the confederate to have beginning state comfort and thus facilitate the motion sequence as a whole. That is, would the participant incur the cost of the movement by adopting an awkward posture to facilitate the use of the tool by the confederate? The results demonstrated that participants allowed the confederate to adopt a comfortable beginning state comfort on 100% of the trials for all the tools. However, the participants did not sacrifice end-state comfort, demonstrating that the participants were able to plan ahead to both maximize their own end-state comfort and the beginning state comfort of the confederate.

Motor interactions with another person: do individuals with Autism Spectrum Disorder plan ahead?

Interpersonal motor interactions (joint-actions) occur on a daily basis. In joint-action situations, typically developing (TD) individuals consider the end-goal of their partner and adjust their own movements to accommodate the other person. The movement planning processes required for joint-action may, however, be difficult for individuals with an Autism Spectrum Disorder (ASD) given documented difficulties in performance on theory of mind (ToM) and motor tasks. The goal of this experiment was to determine if individuals with ASD exhibit end-state comfort behaviors similar to their TD peers in joint-action situations. Participants were asked to either pass, place, or use three common tools: a wooden toy hammer, a stick, or a calculator. These tools were selected because the degree of affordance they offer (i.e., the physical characteristics they posses to prompt proper use) ranges from direct (hammer) to indirect (calculator). Participants were asked to pass the tool to a confederate who intended to place the tool down, or use the tool. Variables of interest included beginning and end-state grip orientations of the participant and confederate (comfortable or uncomfortable) as a function of task goal, and the side to which the tool was placed or passed. Similar to Gonzalez et al. (2011), some individuals with ASD maximized their partners beginning-state comfort by adopting personally uncomfortable postures. That said, their performance was more variable than their TD peers who consistently passed tools in a manner that facilitated comfortable use by the confederate. Therefore, the movement planning processes used to prepare to pass a tool are not stereotypical across all individuals with ASD. We propose that the novel joint-action task described herein provides the basis for testing an important link between motor performance and more complex social and communication behaviors.

The effects of monocular viewing on hand-eye coordination during sequential grasping and placing movements

The contribution of binocular vision to the performance of reaching and grasping movements has been examined previously using single reach-to-grasp movements. However, most of our daily activities consist of more complex action sequences, which require precise temporal linking between the gaze behaviour and manual action phases. Many previous studies found a stereotypical hand-eye coordination pattern, such that the eyes move prior to the reach initiation. Moving the eyes to the target object provides information about its features and location, which can facilitate the predictive control of reaching and grasping. This temporal coordination pattern has been established for the performance of sequential movements performed during binocular viewing. Here we manipulated viewing condition and examined the temporal hand-eye coordination pattern during the performance of a sequential reaching, grasping, and placement task. Fifteen participants were tested on a sequencing task while eye and hand movements were recorded binocularly using a video-based eyetracker and a motion capture system. Our results showed that monocular viewing disrupted the temporal coordination between the eyes and the hand during the place-to-reach transition phase. Specifically, the gaze shift was delayed during monocular compared to binocular viewing. The shift in gaze behaviour may be due to increased uncertainty associated with the performance of the placement task because of increased vergence error during monocular viewing, which was evident in all participants. These findings provide insight into the role of binocular vision in predictive control of sequential reaching and grasping movements.

Spatial Properties of Perceived Pitch: Influence on Reaching Movements

We present three experiments that show a clear influence of pitch on reaching movements. The first experiment shows that when there are incompatibilities between the spatial representations of target coordinates and perceived pitches, response times are longer than when spatial representations are congruous. The second experiment shows that pitch can influence motor responses, biasing their direction. The third experiment shows that in the absence of any other spatial cues, tones are assigned spatial coordinates based on frequency. Our results suggest that pitch may indeed have inherent spatial properties, and that these properties may affect movement planning and execution.

Limb Apraxia: Types, Neural Correlates, and Implications for Clinical Assessment and Function in Daily Living

Apraxia is a neurological disorder of learned movements that cannot be explained on the basis of deficits in basic sensory or motor functions, verbal comprehension, or recognition of tools or objects [1]. While apraxia frequently arises in concert with other impairments such as ataxia, aphasia, and dementia in conditions such as stroke and Alzheimer’s disease, apraxia can be dissociated from these deficits. Apraxia most often arises from left hemisphere damage (LHD) but can also occur with right hemisphere damage (RHD), with incidences ranging between 28–57 % for LHD and 0–34 % for RHD [2].

End-State Comfort Across the Lifespan: A Cross-Sectional Investigation of How Movement Context Influences Motor Planning in an Overturned Glass Task

Young adults plan actions in advance to minimize the cost of movement. This is exemplified by the end-state comfort (ESC) effect. A pattern of improvement in ESC in children is linked to the development of cognitive control processes, and decline in older adults is attributed to cognitive decline. This study used a cross-sectional design to examine how movement context (pantomime, demonstration with image/glass as a guide, actual grasping) influences between-hand differences in ESC planning. Children (5- to 12-year-olds), young adults, and two groups of older adults (aged 60-70, and aged 71 and older) were assessed. Findings provide evidence for adult-like patterns of ESC in 8-year-olds. Results are attributed to improvements in proprioceptive acuity and proficiency in generating and implementing internal representations of action. For older adults early in the aging process, sensitivity to ESC did not differ from young adults. However, with increasing age, differences reflect challenges in motor planning with increases in cognitive demand, similar to previous work. Findings have implications for understanding lifespan motor behavior.

The effects of task-relevant saccadic eye movements performed during the encoding of a serial sequence on visuospatial memory performance

Visuospatial working memory (VSWM) is a set of cognitive processes used to encode, maintain and manipulate spatial information. One important feature of VSWM is that it has a limited capacity such that only few items can be actively stored and manipulated simultaneously. Given the limited capacity, it is important to determine the conditions that affect memory performance as this will improve our understanding of the architecture and function of VSWM. Previous studies have shown that VSWM is disrupted when task-irrelevant eye movements are performed during the maintenance phase; however, relatively fewer studies examined the role of eye movements performed during the encoding phase. On one hand, performing eye movements during the encoding phase could result in a stronger memory trace because the memory formation is reinforced by the activation of the motor system. On the other hand, performing eye movements to each target could disrupt the configural processing of the spatial array because the spatial representation has to be updated with each movement to maintain perceptual stability. Therefore, this work was conducted to examine whether task-relevant saccadic eye movements performed during the encoding phase of a visuospatial working memory task affect the recall of serially presented targets. Results from two experiments showed that average recall accuracy was significantly higher when the spatial array (set size ≥ 7) was encoded using a covert strategy—that is, while participants fixated on a central target, in comparison to an overt strategy—that is, while participants moved their eyes to fixate on each target. Furthermore, the improvement in accuracy was evident only for targets presented in the first half of the sequence, suggesting that the primacy effect is modulated by the presence of eye movements. We propose that executing saccades during encoding could interfere with the ability to use a chunking strategy or disrupt active visualization of the configuration. In conclusion, this is the first study to show that task-relevant saccadic eye movements performed during encoding may actually reduce the spatial span of VSWM. These results extend the current knowledge about the role of eye movements in VSWM, and have implications for future studies investigating the VSWM.

What Are the Circumstances of Falls and Fractures in Long-Term Care?

RÉSUMÉ: Cette étude prospective d’observation rend compte des circonstances qui ont conduit à des chutes des résidents dans des établissements de soins de longue durée (SLD) et les caractéristiques des résidents qui ont subi des fractures suite à une chute. Le personnel a enregistré l’emplacement de la chute, le moment de la journée, l’activité dans laquelle un participant a été engagé avant l’incident et si une blessure a été soutenue. Les statistiques descriptives ont été utilisées pour décrire les chutes, et un modèle linéaire généralisé a été utilisé pour déterminer les différences entre les circonstances. Parmi les 101 résidents SLD qui ont participé, 41 pour cent ont eu au moins une chute. Les résidents étaient beaucoup plus susceptibles d’être tombés dans la chambre et tout en marchant. Parmi les 17 chutes entraînant des fractures, la plupart se sont produites dans la chambre à coucher et la salle de bains, tôt le matin; la plupart des résidents qui ont subi des fractures étaient des femmes ayant une déficience cognitive. Pour surveiller les chutes globalement, la surveillance ambulatoire, qui évite les problèmes de confidentialité dans les chambres à coucher ou les salles de bains, peuvent être nécessaires. Les interventions devraient cibler la marche à pied ou l’organisation de la chambre. This prospective, observational study characterizes the circumstances that led to falls in long-term care (LTC) residents and describes the characteristics of residents who fractured following a fall. Staff recorded the location of the fall, time of day, activity the participant was doing prior, and if an injury occurred. Descriptive statistics were used to describe the falls, and a generalized linear model was used to determine differences between the circumstances. Of the 101 LTC residents who participated, 41 per cent experienced at least one fall. Residents were significantly more likely to have fallen in the bedroom and while walking. Of the 17 falls resulting in fractures, most occurred in the bedroom and bathroom, during the early morning; most residents who fractured were female with cognitive impairment. To monitor falls comprehensively, ambulatory monitoring that avoids privacy issues in bedrooms or bathrooms may be needed. Interventions should target walking or the bedroom setting.

The use of action phrases in individuals with Autism Spectrum Disorder.

Previous research has shown that individuals with Autism Spectrum Disorder (ASD) may be able to perceive the intentions of another individual through tool use (e.g., Aldridge et al., 2000; Gonzalez et al., 2013). However, it is not well understood how individuals with ASD respond to an indirect connection between an extrapolated action and the required object. To address this question, we employed action phrases that indirectly provided the contextual information about which object to use. Individuals with ASD, and sex and age matched typically developing peers, were asked to pick which object would be needed to complete the task described in a sentence displayed on a computer screen. Although individuals with ASD exhibited slower response times overall, their accuracy scores were comparable to typically developing individuals. The longer response times support the notion that individuals with ASD may have a harder time disengaging their initial perceived use for the object before considering other inherent action possibilities afforded by the object.