Previous research suggests that applying anodal transcranial direct-current stimulation (tDCS) to the medial-frontal cortex can improve how quickly subjects learn to make simple discriminations (i.e., red from blue). Here, we tested the idea that this enhanced task learning is attributable to superior encoding of relevant information into visual long-term memory. Thirty subjects completed an anodal stimulation session and a sham session, with order counterbalanced across subjects, before performing recognition-memory tasks using pictures of real-world objects and visually presented words or nonwords. These tasks allowed us to detect potential memory differences across types of memoranda. Contrary to the hypothesis that the medial-frontal cortex helps control encoding fidelity, we found that anodal tDCS delivered over this brain region did not significantly improve subjects' memory for visual stimuli, regardless of stimulus type. Our findings show no evidence that targeting medial-frontal cortex with tDCS changes the fidelity of our visual long-term memories.
The P100, N170, P200, and N250 have been implicated in previous studies on face perception, including perception of own- and other-race faces. The present study examines the potential influence of participants' implicit racial biases as well as that of task demands, as these factors may contribute to the mixed findings in the literature and shed insight on the cognitive mechanisms underlying own- and other-race face perception. White adults completed a face race categorization task and a face identity processing task with White and Asian faces while continuous EEG was recorded. Participants with larger implicit biases favoring their own race tended to show larger N170 to P200 and P200 to N250 peak-to-peak amplitudes in the right hemisphere when categorizing faces by race and when processing own- and other-race face identities. Those with larger implicit racial biases also tended to show longer P200 latencies for own- compared to other-race faces in the left hemisphere in both task conditions. Furthermore, those with relatively smaller implicit biases favoring their own race tended to show larger P100 amplitudes when categorizing other- compared to own-race faces by race and more negative N170 amplitudes when processing other- compared to own-race face identities. Thus, both task demands and implicit racial bias can modulate early face-sensitive responses to own- and other-race faces. Adults with relatively larger implicit biases favoring their own race showed different ERP responses to own- and other-race faces later in their face processing and regardless of task demands. However, among adults with relatively smaller implicit biases favoring their own race, differences in ERP responses to own- and other-race faces occurred earlier and was task dependent.
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