Background: Children with autism experience sensory processing difficulties which may be at the core of their learning and behavioral deficits.  The nature of these deficits, especially in the tactile domain, remains unclear.  M50 sensory evoked fields (SEF) collected in response to familiar and novel finger taps reflect the early processing of somatosensory information.
Objectives: This study aims to compare early unimodal cortical processing in children with high functioning autism (AS) and matched healthy controls (HC). 
Methods: Responses were recorded for the AS group (N=7, mean age=9.6) and the HC group (N=6, mean age=8.9) using a 275-sensor MEG. The stimuli were pneumatic finger taps (140 ms, ~17 PSI, and ISI 330 ms).  Taps to the right index finger (deviant) occurred every 3 -7 taps to the middle finger (standard). The amplitude and latency averages of the M50 were compared between AS and HC for deviant taps, pre-deviant standard taps and post-deviant standard taps.
Results: Reliable parietal M50 was elicited to all tactile stimuli and exhibited a characteristic latency and waveform in the HC group.  The HC group demonstrated the expected latency delay and amplitude increase to the deviant stimuli.  By contrast, the AS group showed considerable variability in their waveforms, with M50 peak amplitude to deviant stimuli being significantly lower than HC. 
Conclusions: Our results suggest an atypical processing of novel tactile information in autism that can be detected as early as the M50 waveform.  While this may represent primary sensory cortical dysfunction, we cannot exclude the contribution of disrupted top-down modulation to novel stimuli.