Humans can extract statistical regularities of the environment to predict upcoming events. Previous research recognized that implicitly acquired statistical knowledge remained persistent and continued to influence behavior even when the regularities were no longer present in the environment. Here, in an fMRI experiment, we investigated how the persistence of statistical knowledge is represented in the brain. Participants ( n = 32) completed a visual, four-choice, RT task consisting of statistical regularities. Two types of blocks constantly alternated with one another throughout the task: predictable statistical regularities in one block type and unpredictable ones in the other. Participants were unaware of the statistical regularities and their changing distribution across the blocks. Yet, they acquired the statistical regularities and showed significant statistical knowledge at the behavioral level not only in the predictable blocks but also in the unpredictable ones, albeit to a smaller extent. Brain activity in a range of cortical and subcortical areas, including early visual cortex, the insula, the right inferior frontal gyrus, and the right globus pallidus/putamen contributed to the acquisition of statistical regularities. The right insula, inferior frontal gyrus, and hippocampus as well as the bilateral angular gyrus seemed to play a role in maintaining this statistical knowledge. The results altogether suggest that statistical knowledge could be exploited in a relevant, predictable context as well as transmitted to and retrieved in an irrelevant context without a predictable structure.

In our everyday life, we continuously get to know people, dominantly through their faces. Several neuroscientific experiments showed that familiarization changes the behavioral processing and underlying neural representation of faces of others. Here, we propose a model of the process of how we actually get to know someone. First, the purely visual familiarization of unfamiliar faces occurs. Second, the accumulation of associated, nonsensory information refines person representation, and finally, one reaches a stage where the effortless identification of very well-known persons occurs. We offer here an overview of neuroimaging studies, first evaluating how and in what ways the processing of unfamiliar and familiar faces differs and, second, by analyzing the fMRI adaptation and multivariate pattern analysis results we estimate where identity-specific representation is found in the brain. The available neuroimaging data suggest that different aspects of the information emerge gradually as one gets more and more familiar with a person within the same network. We propose a novel model of familiarity and identity processing, where the differential activation of long-term memory and emotion processing areas is essential for correct identification.

The perception of facial gender has been found to be adaptively recalibrated: adaptation to male faces causes participants to perceive subsequent faces as more feminine and vice versa [Webster, M. A., Kaping, D., Mizokami, Y., & Duhamel, P. Adaptation to natural facial categories. Nature, 428, 557–561, 2004]. In an event-related brain potential (ERP) study, Kovács et al. [Kovács, G., Zimmer, M., Banko, E., Harza, I., Antal, A., & Vidnyanszky, Z. Electrophysiological correlates of visual adaptation to faces and body parts in humans. Cerebral Cortex, 16, 742–753, 2006] reported reduced N170 amplitudes and increased latencies for test faces following female gender adaptation compared to control stimulus (a phase randomized face) adaptation. We examined whether this N170 attenuation to test faces was related to the adaptor's gender, or to adaptation to face exposure in general. We compared N170 effects after adaptation to either male or androgynous faces. Additionally, we investigated cross-modal adaptation for the same test faces following male or androgynous voice adaptors. Visual adaptation to face gender replicated previously reported aftereffects in classifying androgynous faces, and a similar trend was observed following adaptation to voice gender. Strikingly, N170 amplitudes were dramatically reduced for faces following face adaptors (relative to those following voice adaptors), whereas only minimal gender-specific adaptation effects were seen in the N170. By contrast, strong gender-specific adaptation effects appeared in a centroparietal P3-like component (∼400–600 msec), which in the context of adaptation may reflect a neural correlate of the detection of perceptual novelty.