With the advent of dense sensor arrays (64–256
channels) in electroencephalography and magnetoencephalography
studies, the probability increases that some recording
channels are contaminated by artifact. If all channels
are required to be artifact free, the number of acceptable
trials may be unacceptably low. Precise artifact screening
is necessary for accurate spatial mapping, for current
density measures, for source analysis, and for accurate
temporal analysis based on single-trial methods. Precise
screening presents a number of problems given the large
datasets. We propose a procedure for statistical correction
of artifacts in dense array studies (SCADS), which (1)
detects individual channel artifacts using the recording
reference, (2) detects global artifacts using the average
reference, (3) replaces artifact-contaminated sensors with
spherical interpolation statistically weighted on the basis
of all sensors, and (4) computes the variance of the signal
across trials to document the stability of the averaged
waveform. Examples from 128-channel recordings and from
numerical simulations illustrate the importance of careful
artifact review in the avoidance of analysis errors.