Evoked Response Potential (ERP) and Face Stimuli N170: negative-going potential at 170 ms Largest over the right parietal lobe, also on the left parietal lobe. N170 - distinct negative potential at 170 ms post-stimulus onset fairly early in processing This occurs at T6; smaller effect at T5 T = temporal lobe 5 = left 6 = right right hemisphere specialization From Tanaka and Curran (2001)

An Experiment Show Faces and Words Embedded in Noise: High Contrast Low Contrast Faces Low Contrast Words High Contrast Words Noise Alone

For Noise-Alone Trials: The Important Stuff: For Noise-Alone Trials: * t(9) = 2.74, p = .023 High Contrast Faces High Contrast Words Low Contrast Words Noise Alone Amplitude (V)

Main Result: On noise-alone trials: Larger N170 when observers report seeing a face than when report seeing a word. Occurs in 9 of the 10 subjects. No other differences in any other channel at the P100, N170 or P300 components. Unlikely to just reflect activity for an already-made decision. Relates activity in the perceptual processing areas to the behavioral response. Greater activity in the N170 neurons is associated with ‘face’ responses to the noise-alone stimulus. One interpretation: Greater activity in the face processing region biases the response towards a ‘face’ response. Inside-out gets at the idea that the internal response might be higher for whatever reason on that trial, and this leads observer to think saw a face, and to give an overt 'face' response. Note that our data is just correlational; it could be that the prior trial could have primed our N170 neurons, and that we were thinking about faces for other reasons (maybe frontal cortex was primed as well), and this leads to the correlation in the absence of causality. It might not be that the greater N170 is b/c they saw a face in the noise, but rather seeing a face on the previous trial primed them. In other words, do observers have larger N170 on present trial if a face was shown on the previous trial?