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Kasper Vinken, Hans Op de Beeck, Rufin Vogels; Face repetition probability does not affect repetition suppression in macaque middle lateral face patch.. Journal of Vision 2017;17(10):257. doi: https://doi.org/10.1167/17.10.257.
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It has been proposed that repetition suppression (i.e. a reduced neural activity when stimuli are repeated) results from a fulfilled expectation of repetition or a reduced prediction error (Summerfield et al., 2008). This implies that repetition suppression should increase when a repetition is expected and decrease when it is unexpected. While this prediction is supported by human functional imaging (fMRI) studies (e.g. Summerfield et al., 2008), no evidence was found in macaque inferior temporal cortex (IT) spiking activity (Kaliukhovich & Vogels, 2011). Here, we tested three possible explanations for this discrepancy by recording spiking activity in macaque IT. First, we performed recordings in face patch ML instead of outside of a face-selective region. Second, we used faces as stimuli. Third, we required our monkeys to perform a task instead of passive fixation. In two experiments, we manipulated the probability of a face repetition (75% or 25%) between blocks of 40 trials. A trial consisted of two face presentations that were either a repetition (same face identity) or an alternation, followed by a saccade response by the monkey to receive a reward. In a first experiment, we included target trials where one face was inverted. The task (did the trial contain an inverted face?) was orthogonal to the manipulation of repetition probability. We observed repetition suppression, but there was no effect of repetition probability on its magnitude (face-selective cells in 2 monkeys). In a further experiment, we made a face repetition relevant to the task (i.e. was the face repeated?). There was a clear performance bias dependent on the probability of a face repetition, but again no effect on the responses (face-selective cells in 1 monkey). In conclusion, regardless of whether a face repetition is explicitly relevant for the monkey, we see no evidence of a prediction error response in ML.
Meeting abstract presented at VSS 2017
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