Data from: Eye coding mechanisms in early human face event-related potentials

In humans, the N170 event-related potential (ERP) is an integrated measure
of cortical activity that varies in amplitude and latency across trials.
Researchers often conjecture that N170 variations reflect cortical
mechanisms of stimulus coding for recognition. Here, to settle the
conjecture and understand cortical information processing mechanisms, we
unraveled the coding function of N170 latency and amplitude variations in
possibly the simplest socially important natural visual task: face
detection. On each experimental trial, 16 observers saw face and noise
pictures sparsely sampled with small Gaussian apertures.
Reverse-correlation methods coupled with information theory revealed that
the presence of the eye specifically covaries with behavioral and neural
measurements: the left eye strongly modulates reaction times and lateral
electrodes represent mainly the presence of the contralateral eye during
the rising part of the N170, with maximum sensitivity before the N170
peak. Furthermore, single-trial N170 latencies code more about the
presence of the contralateral eye than N170 amplitudes and early latencies
are associated with faster reaction times. The absence of these effects in
control images that did not contain a face refutes alternative accounts
based on retinal biases or allocation of attention to the eye location on
the face. We conclude that the rising part of the N170, roughly 120–170 ms
post-stimulus, is a critical time-window in human face processing
mechanisms, reflecting predominantly, in a face detection task, the
encoding of a single feature: the contralateral eye.