16652
Premotor Potential Differences in Autism Spectrum Disorder, ADHD and Neurotypical Children
Motor abnormalities in autism bear the characteristics of precedence and universality that characterize a core symptom. Underlying the motor skill deficits in autism and Asperger syndrome is a dyspraxia that by definition is an inability to plan, organize, and execute movements in the absence of any known physical and/or neurological condition. This deficit is more apparent in autism spectrum disorders when compared to other neurodevelopmental disabilities, i.e., ADHD.
Objectives:
The lateralized readiness potential (LRP) is an index of motor processes and it is assumed that this brain potential is generated by a source within the motor cortex. LRP reflects the response-specific involvement of the left and right cortices of the brain and enables the determination of the point in time at which the activation of the motor cortex controlling one hand surpasses the activation of the motor cortex controlling the other side. The LRP is assumed to be related to selective response activation. It captures the asymmetric portion of the late Bereitschaftspotential (BP) preceding hand or foot movements. It is important for the mental chronometry that LRP helps to determine the exact point in time when sensory information affects motor processing and response execution.
Methods:
Our goal was to compare differences in LRP during cued spatial attention task between group of children with Autism Spectrum Disorder (ASD), Attention Deficit Hyperactivity Disorder (ADHD), and neurotypical (NT) children (N=12/group, mean age 14.6 years). Each study participant performed a Posner spatial attention task with congruent (correctly cued, 75%) and incongruent (incorrectly cued, 25%) trials with dense-array EEG recording (128 channel Electrical Geodesics Inc. EEG system). In our study we used stimulus-locked LRP method of waveform calculation and since S1-S2 interval was set on 1s, we computed mean LRP (in uV) and integrated LRP values for 2 windows (early 600-800 ms post S1 stimulus; and late – 800-1200 ms post-stimulus components of LRP).
Results:
In our sample of ASD, ADHD and NT controls, differences were not significant at the early stage, but became significant at the late stage of the LRP yielding significant Time (early, late) X Group interaction (F=6.77, p=0.012). Post-hoc analysis showed group differences at 1000-1200 ms post stimulus window (F=4.81, p=0.033) between autism and control groups. Autism group also showed more pronounced differences of LRPs in incongruent trials as compared with both ADHD and NT groups.
Conclusions: Our study showed suggests more deficient motor preparation during tasks congruency manipulations in children with ASD as compared to ADHD and neurotypicals manifested in LRP components reflective of abnormal motor preparation processing.