TY  - JOUR
AU  - Reber, T. P.
AU  - Do Lam, A. T. A.
AU  - Axmacher, N.
AU  - Elger, C. E.
AU  - Helmstaedter, C.
AU  - Henke, K.
AU  - Fell, J.
TI  - Intracranial EEG correlates of implicit relational inference within the hippocampus.
JO  - Hippocampus
VL  - 26
IS  - 1
SN  - 1050-9631
CY  - New York, NY [u.a.]
PB  - Wiley
M1  - DZNE-2020-04686
SP  - 54-66
PY  - 2016
AB  - Drawing inferences from past experiences enables adaptive behavior in future situations. Inference has been shown to depend on hippocampal processes. Usually, inference is considered a deliberate and effortful mental act which happens during retrieval, and requires the focus of our awareness. Recent fMRI studies hint at the possibility that some forms of hippocampus-dependent inference can also occur during encoding and possibly also outside of awareness. Here, we sought to further explore the feasibility of hippocampal implicit inference, and specifically address the temporal evolution of implicit inference using intracranial EEG. Presurgical epilepsy patients with hippocampal depth electrodes viewed a sequence of word pairs, and judged the semantic fit between two words in each pair. Some of the word pairs entailed a common word (e.g., 'winter-red,' 'red-cat') such that an indirect relation was established in following word pairs (e.g., 'winter-cat'). The behavioral results suggested that drawing inference implicitly from past experience is feasible because indirect relations seemed to foster 'fit' judgments while the absence of indirect relations fostered 'do not fit' judgments, even though the participants were unaware of the indirect relations. A event-related potential (ERP) difference emerging 400 ms post-stimulus was evident in the hippocampus during encoding, suggesting that indirect relations were already established automatically during encoding of the overlapping word pairs. Further ERP differences emerged later post-stimulus (1,500 ms), were modulated by the participants' responses and were evident during encoding and test. Furthermore, response-locked ERP effects were evident at test. These ERP effects could hence be a correlate of the interaction of implicit memory with decision-making. Together, the data map out a time-course in which the hippocampus automatically integrates memories from discrete but related episodes to implicitly influence future decision making.
KW  - Adult
KW  - Decision Making: physiology
KW  - Drug Resistant Epilepsy: physiopathology
KW  - Drug Resistant Epilepsy: psychology
KW  - Drug Resistant Epilepsy: surgery
KW  - Electrocorticography
KW  - Epilepsy, Temporal Lobe: physiopathology
KW  - Epilepsy, Temporal Lobe: psychology
KW  - Epilepsy, Temporal Lobe: surgery
KW  - Evoked Potentials
KW  - Female
KW  - Hippocampus: physiology
KW  - Hippocampus: physiopathology
KW  - Hippocampus: surgery
KW  - Humans
KW  - Judgment: physiology
KW  - Language Tests
KW  - Male
KW  - Memory: physiology
KW  - Middle Aged
KW  - Neuropsychological Tests
KW  - Photic Stimulation
KW  - Reaction Time
KW  - Reading
KW  - Semantics
KW  - Visual Perception: physiology
KW  - Young Adult
LB  - PUB:(DE-HGF)16
C6  - pmid:26136107
DO  - DOI:10.1002/hipo.22490
UR  - https://pub.dzne.de/record/138364
ER  -