Article

Mirror Neuron Activity Associated with Social Impairments but not Age in Autism Spectrum Disorder

Monash Alfred Psychiatry Research Centre, School of Psychology and Psychiatry, Monash University and the Alfred, Melbourne, Australia.
Biological psychiatry (Impact Factor: 9.47). 03/2012; 71(5):427-33. DOI: 10.1016/j.biopsych.2011.09.001
Source: PubMed

ABSTRACT The neurobiology of autism spectrum disorder (ASD) is not particularly well understood, and biomedical treatment approaches are therefore extremely limited. A prominent explanatory model suggests that social-relating symptoms may arise from dysfunction within the mirror neuron system, while a recent neuroimaging study suggests that these impairments in ASD might reduce with age.
Participants with autism spectrum disorder (i.e., DSM-IV autistic disorder or Asperger's disorder) (n = 34) and matched control subjects (n = 36) completed a transcranial magnetic stimulation study in which corticospinal excitability was assessed during the observation of hand gestures.
Regression analyses revealed that the ASD group presented with significantly reduced corticospinal excitability during the observation of a transitive hand gesture (relative to observation of a static hand) (p < .05), which indicates reduced putative mirror neuron system activity within ventral premotor cortex/inferior frontal gyrus. Among the ASD group, there was also a negative association between putative mirror neuron activity and self-reported social-relating impairments, but there was no indication that mirror neuron impairments in ASD decrease with age.
These data provide general support for the mirror neuron hypothesis of autism; researchers now must clarify the precise functional significance of mirror neurons to truly understand their role in the neuropathophysiology of ASD and to determine whether they should be used as targets for the treatment of ASD.

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    • "First, it has been demonstrated that socialcognition is associated with activity in this mirror neuron network in healthy individuals (Baird et al., 2011; Enticott et al., 2008b; Pineda and Hecht, 2009). Secondly, abnormal activation of the mirror system has been demonstrated in schizophrenia (Enticott et al., 2008a; Kato et al., 2011; McCormick et al., 2012; Mehta et al., 2013, 2014; Schurmann et al., 2007) and autism (Dapretto et al., 2006; Enticott et al., 2012; Martineau et al., 2010), although concerns have been raised about consistency of these findings (Dinstein et al., 2010; Hamilton, 2013; Horan et al., 2014; Theoret et al., 2005). Virtual-lesion or transient functional disruption studies (Pascual-Leone et al., 2000) using inhibitory low-frequency magnetic pulses over the inferior frontal gyrus (IFG) (Avenanti et al., 2007; Jacquet and Avenanti, 2013; Keuken et al., 2011) have yielded further clues regarding the spatial and functional properties of this mirror neuron network. "
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    ABSTRACT: Virtual lesions in the mirror neuron network using inhibitory low-frequency (1Hz) transcranial magnetic stimulation (TMS) have been employed to understand its spatio-functional properties. However, no studies have examined the influence of neuro-enhancement by using excitatory high-frequency (20Hz) repetitive transcranial magnetic stimulation (HF-rTMS) on these networks. We used three forms of TMS stimulation (HF-rTMS, single and paired pulse) to investigate whether the mirror neuron system facilitates the motor system during goal-directed action observation relative to inanimate motion (motor resonance), a marker of putative mirror neuron activity. 31 healthy individuals were randomized to receive single-sessions of true or sham HF-rTMS delivered to the left inferior frontal gyrus - a component of the human mirror system. Motor resonance was assessed before and after HF-rTMS using three TMS cortical reactivity paradigms: (a) 120% of resting motor threshold (RMT), (b) stimulus intensity set to evoke motor evoked potential of 1-millivolt amplitude (SI1mV) and (c) a short latency paired pulse paradigm. Two-way RMANOVA showed a significant group (true versus sham) X occasion (pre- and post-HF-rTMS motor resonance) interaction effect for SI1mV [F(df)=6.26 (1, 29), p=0.018] and 120% RMT stimuli [F(df)=7.01 (1, 29), p=0.013] indicating greater enhancement of motor resonance in the true HF-rTMS group than the sham-group. This suggests that HF-rTMS could adaptively modulate properties of the mirror neuron system. This neuro-enhancement effect is a preliminary step that can open translational avenues for novel brain stimulation therapeutics targeting social-cognition deficits in schizophrenia and autism. Copyright © 2015 Elsevier B.V. All rights reserved.
    07/2015; DOI:10.1016/j.ajp.2015.06.014
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    • "For the TMS component , trials exhibiting tonic muscle activity within 200 ms before TMS pulse administration were removed prior to analysis ( 3 . 2% of all trials ) . Median MEP readings for static and transitive hand conditions were utilized to calculate Motor evoked potential percentage change ( MEP - PC ) values , as done previously ( Enticott et al . , 2012a ) . This provides a relative IMR index , with larger MEP - PCs indicative of greater responses in active compared to static hand conditions . MEP - PC was calculated as : MEP - PC = ["
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    ABSTRACT: The human mirror neuron system (MNS) is hypothesized to be crucial to social cognition. Given that key MNS-input regions such as the superior temporal sulcus are involved in biological motion processing, and mirror neuron activity in monkeys has been shown to vary with visual attention, aberrant MNS function may be partly attributable to atypical visual input. To examine the relationship between gaze pattern and interpersonal motor resonance (IMR; an index of putative MNS activity), healthy right-handed participants aged 18-40 (n = 26) viewed videos of transitive grasping actions or static hands, whilst the left primary motor cortex received transcranial magnetic stimulation. Motor-evoked potentials recorded in contralateral hand muscles were used to determine IMR. Participants also underwent eyetracking analysis to assess gaze patterns whilst viewing the same videos. No relationship was observed between predictive gaze and IMR. However, IMR was positively associated with fixation counts in areas of biological motion in the videos, and negatively associated with object areas. These findings are discussed with reference to visual influences on the MNS, and the possibility that MNS atypicalities might be influenced by visual processes such as aberrant gaze pattern.
    Frontiers in Human Neuroscience 07/2015; 9:396. DOI:10.3389/fnhum.2015.00396 · 2.90 Impact Factor
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    • "Mirror systems have been studied in autism, a neurodevelopmental disorder characterised by social difficulties. Some studies have found evidence of reduced mirror system activity in autism (Oberman et al., 2005; Theoret et al., 2005), and others have found that mirror system dysfunction was associated with increased symptoms of social relating (Dapretto et al., 2006; Enticott et al., 2012). Other studies of mirror systems in autism, however, have not found evidence for reduced mirror systems (Dinstein et al., 2010; Enticott et al., 2013; Fan et al., 2010; Oberman et al., 2008). "
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    ABSTRACT: Dysfunctional mirror neuron systems have been proposed to contribute to the social cognitive deficits observed in schizophrenia. A few studies have explored mirror systems in schizophrenia using various techniques such as TMS (levels of motor resonance) or EEG (levels of mu suppression), with mixed results. This study aimed to use a novel multimodal approach (i.e. concurrent TMS and EEG) to further investigate mirror systems and social cognition in schizophrenia. Nineteen individuals with schizophrenia or schizoaffective disorder and 19 healthy controls participated. Single-pulse TMS was applied to M1 during the observation of hand movements designed to elicit mirror system activity. Single EEG electrodes (C3, CZ, C4) recorded brain activity. Participants also completed facial affect recognition and theory of mind tasks. The schizophrenia group showed significant deficits in facial affect recognition and higher level theory of mind compared to healthy controls. A significant positive relationship was revealed between mu suppression and motor resonance for the overall sample, indicating concurrent validity of these measures. Levels of mu suppression and motor resonance were not significantly different between groups. These findings indicate that in stable outpatients with schizophrenia, mirror system functioning is intact, and therefore their social cognitive difficulties may be caused by alternative pathophysiology. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
    06/2015; DOI:10.1016/j.psychres.2015.05.067
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