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Local Hjorth Laplacian of Geodesic Sensor Net (128-channel) montage for targets in tonal and phonetic oddball tasks. Right-handed, healthy adults (N=17) responded to targets with a left or right button press, or silently counted targets. Hjorth computation used radial neighbors approximating distances in a previous study (Tenke et al 1998). Response-related source (red/orange) asymmetries are prominent in frontocentral regions by 300 ms. Task-related source asymmetries are more subtle, and are seen in centroparietal regions (eg., compare left press maps for both tasks at 400 ms). Task-related differences are also evident for the current sinks (blue/green) underlying N100 and N200 (70-250 ms).

Surface Potentials - Targets GSN128 - Task x Response (gif animation 2.82 MB)previous animation  

 

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