Abstract
The response to an upcoming salient event is accelerated when the event is expected given the preceding events – i.e. a temporal context effect. For example, naming a picture following a strongly constraining temporal context is faster than naming a picture after a weakly constraining temporal context. We used sentences as naturalistic stimuli to manipulate expectations on upcoming pictures without prior training. Here, using intracranial recordings from the human hippocampus we found more power in the high-frequency band prior to high-expected pictures than weakly expected ones. We applied pattern similarity analysis on the temporal pattern of hippocampal high-frequency band activity in single hippocampal contacts. We found that greater similarity in the pattern of hippocampal field potentials between pre-picture interval and expected picture interval in the high-frequency band predicted picture-naming latencies. Additional pattern similarity analysis indicated that the hippocampal representations follow a semantic map. The results suggest that hippocampal pre-activation of expected stimuli is a facilitating mechanism underlying the powerful contextual behavioral effect.
Highlights
The response to an upcoming salient event is accelerated when the event is expected given the preceding events – i.e. a temporal context effect
Single-unit activity[16] and local field potential (LFP) in the high frequency band (HFB, 50–250 Hz)[17, 18] indicate that picture concepts are represented in the hippocampus approximately 0.2 s after picture onsets (Fig. 2A)
We focused on the high-frequency band (HFB) activity at 0.2 s from the picture onset to the response times (RT) for the picture intervals
Summary
The response to an upcoming salient event is accelerated when the event is expected given the preceding events – i.e. a temporal context effect. We tested if the response times (RT) could be predicted by hippocampal pre-activation of expected stimuli. We tested if the similarity between the pattern of hippocampal LFP power in HFB during the pre-picture intervals and the picture intervals predicted the RTs for high-expected stimuli.
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