Abstract
Several studies indicate the functional importance of the motor cortex for higher cognition, language and semantic processing, and place the neural substrate of these processes in sensorimotor action-perception circuits linking motor, sensory and perisylvian language regions. Interestingly, in individuals with autism spectrum disorder (ASD), semantic processing of action and emotion words seems to be impaired and is associated with hypoactivity of the motor cortex during semantic processing. In this study, the relationship between semantic processing, fine motor skills and clinical symptoms was investigated in 19 individuals with ASD and 22 typically-developing matched controls. Participants completed two semantic decision tasks involving words from different semantic categories, a test of alexithymia (the Toronto Alexithymia Scale), and a test of fine motor skills (the Purdue Pegboard Test). A significant Group × Word Category interaction in accuracy (p < 0.05) demonstrated impaired semantic processing for action words, but not object words in the autistic group. There was no significant group difference when processing abstract emotional words or abstract neutral words. Moreover, our study revealed deficits in fine motor skills as well as evidence for alexithymia in the ASD group, but not in neurotypical controls. However, these motor deficits did not correlate significantly with impairments in action-semantic processing. We interpret the data in terms of an underlying dysfunction of the action-perception system in ASD and its specific impact on semantic language processing.
Highlights
Neuroscientific research on ‘‘embodied cognition’’ postulates that higher cognitive processes, such as language, thought and reasoning, are functionally interwoven with lower-level sensory and motor functions (Gallese and Lakoff, 2005; Barsalou, 2010)
Semantic processing of words associated with actions and motor movements activate the motor cortex somatotopically (Hauk et al, 2004; Pulvermüller and Fadiga, 2010; Moseley et al, 2012), Semantic-Motor Impairments in Autism which may be explained on the basis of the formation and activation of sensorimotor action-perception circuits comprising neurons in the motor cortex, in sensory cortices and in perisylvian language areas (Pulvermüller and Fadiga, 2010; Pulvermüller, 2012; Pulvermüller et al, 2014)
Specific impairments in actionsemantic processing have been reported in individuals with autism spectrum disorder (ASD), a neurodevelopmental syndrome characterized by problems with social interaction, communication and language, and, importantly, by dysfunction in motor behavior [American Psychiatric Association (APA), (2000)]
Summary
Neuroscientific research on ‘‘embodied cognition’’ postulates that higher cognitive processes, such as language, thought and reasoning, are functionally (and possibly structurally) interwoven with lower-level sensory and motor functions (Gallese and Lakoff, 2005; Barsalou, 2010). To this end, recent empirical evidence from behavioral and neuroimaging studies demonstrate that the motor cortex serves an important function for language processing, during semantic processing (Pulvermüller, 1999; Pulvermüller et al, 2005; Moseley et al, 2013). Abnormalities in structural and functional connectivity have been reported within and between primary motor cortex and other cortical regions in ASD (Mostofsky et al, 2007, 2009; McCleery et al, 2013; Floris et al, 2016; Thompson et al, 2017), as have differences in gray matter volume (Duffield et al, 2013; Mahajan et al, 2016), suggesting that the action-semantic deficit in this group is comparable to that seen in other populations with disease or damage to the motor system
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