The hippocampal formation (hippocampus proper and the parahippocampal cortex) plays a fundamental role in episodic memory - the ability to learn, store and retrieve information [43] - and hippocampus dysfunction has been consistently reported in schizophrenia [44]. Surprisingly, episodic memory studies in healthy relatives of patients with schizophrenia so far have failed to report abnormal hippocampal activation [14], though one study reported abnormal parahippocampal activity [45 ·] (Supplementary Table 1.C). Many studies have explored the role of risk genes in hippocampus modulation during episodic memory tasks in healthy volunteers [8, 9, 11, 28, 30, 46–50] (Supplementary Table 2.C) (Figure 2.C). Since the status of hippocampus function during episodic memory as an intermediate phenotype related to risk for schizophrenia has not been convincingly demonstrated, the link between the neurophysiological effect of these genes on HF and their mechanism for increasing the risk of schizophrenia is unclear.
