Cheryl M. Glazebrook

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.

Movement Planning and Reprogramming in Individuals with Autism.

Two experiments explored how individuals with and without autism plan and reprogram movements. Participants were given partial or complete information regarding the location of the upcoming manual movement. In Experiment 1, direct information specified the hand or direction of the upcoming movement. These results replicated previous reports that participants with autism utilize advance information to prepare their movements in the same manner as their chronologically age matched peers. Experiment 2 examined how individuals respond to an unexpected change in the movement requirements. Participants received advance information about the hand and direction of the upcoming movement. On 20% of the trials participants needed to adjust either the hand or direction they had prepared. Overall, the individuals with autism had difficulty reprogramming already planned movements, particularly if a different effector was required.

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.

Perception-action and the Müller-Lyer illusion: amplitude or endpoint bias?

Over the past decade there has been a great deal of controversy regarding the relative impact of visual illusions on cognitive judgments and the control of goal-directed action. We report the results of two experiments indicating that perceptual biases associated with the Müller-Lyer illusion involve a misjudgment of amplitude/extent while aiming biases involve error in the specification of a movement endpoint. This dissociation of perception and action is consistent with some aspects of Milner and Goodale’s two visual system model, but not others.

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.

Measuring advanced motor skills in children with cerebral palsy: further development of the Challenge module.

Purpose: Since previous testing of the Challenge Module revealed that response scales should assess performance speed as well as skill accomplishment, this study sought to develop empirically based dual-criterion (accomplishment and time) response options. Methods: Challenge items were tested with a convenience sample of 34 children who were typically developing (4-10 years) to obtain time cut-points that could be applied to children/youth with cerebral palsy. Median/lower quartile item performance times were calculated within younger (<7.5 years) and older child (≥7.5 years) groups, and used as benchmarks for response option cut-points. Childrens scores were recalculated using these cut-points to verify that differences in younger and older childrens abilities and times were captured. Results: Mean scores were 48.9% and 87.2% for younger and older groups, reflecting expected developmental progression. Further response revision captured high-level movement control older children exhibited. Conclusion: The revised Challenge measures skill accomplishment, speed, and quality.

Influence of Endogenous and Exogenous Orientations of Attention on Inhibition of Return in a Cross-Modal Target—Target Aiming Task

The authors conducted 2 experiments in which participants (N = 16 in each) executed successive unimanual aiming movements to target locations that were indicated by the onset of either an auditory or a visual stimulus. In Experiment 1 (exogenous orientation), inhibition of return (IOR) effects were observed, with reliable reaction time (RT) costs associated with movements returning to the same target and a trend toward larger IOR effects in left than in right space. There was no influence of stimulus modality on the magnitude of IOR. IOR was also observed in Experiment 2 (endogenous orientation), except the influence of stimulus modality reliably mediated those effect. In that case, IOR was evident only when the previous modality was visual and the current modality was auditory. Together, the results of those 2 experiments suggest that in situations in which 2 paired movements constitute the response criteria, IOR is both supramodal and lateralized to contralateral space.

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.

Fitts’s Law using lower extremity movement: Performance driven outcomes for degenerative lumbar spinal stenosis

A paucity of objective outcome measures exists for assessing movement disorders, including degenerative lumbar spinal stenosis (LSS). Fittss Law provides a novel approach to clinical outcome measurement since performance is resistant to learning, and task difficulty can be altered. The objective of the present study was to compare, using a Fittss task, movement performance of individuals with and without LSS to determine if motor difficulties that arise with LSS impede the planning, initiation, or execution of deliberate lower limb movements. Twelve pre-surgical LSS patients and twelve control participants from the community performed a Fittss Law (foot reaching) task, while LSS participants also completed pain and disability questionnaires. Fittss Law was evident for both groups, however the LSS groups movements were more adversely impacted as task difficulty increased. Specifically, the LSS groups movement time and time to peak velocity (ttPV) increased as task index of difficulty increased, while peak velocity decreased. Correlations between ttPV and leg pain, and with stenosis impairment severity respectively, provided evidence that less support leg pain and less stenosis impairment severity yield faster ttPV in the moving leg at the highest index of difficulty. Therefore a lower extremity Fittss Law task captured differences in the planning and execution of leg movements between healthy and LSS populations.

The effect of response uncertainty on illusory biases of perception and action

When task requirements were known in advance, Glazebrook et al. [C.M. Glazebrook, V.P. Dhillon, K.M. Keetch, J. Lyons, E. Amazeen, D.J. Weeks, D. Elliott, Perception-action and the Müller-Lyer illusion: amplitude or endpoint bias?, Exp. Brain Res. 160 (2005) 71-78.] demonstrated that perceptual biases associated with the Müller-Lyer illusion resulted from a misperception of figure extent, while manual aiming biases resulted from a misperception of vertex position. In this study, we examined the degree to which prior knowledge of task requirements influenced how participants coded visual-spatial information associated with Müller-Lyer configurations. Specifically, we investigated how illusory biases are affected when uncertainty exists as to whether participants will be required to make a perceptual-cognitive decision about the length of a figure or complete a rapid aiming movement to a figure vertex. Although aiming movements were completed in a similar manner regardless of the prior knowledge condition, perceptual biases were associated with a misperception of extent when the task was known and a misperception of both extent and position when the task was unknown. These findings indicate that people are flexible in the manner in which they code visual-spatial information.