11 Sleep and Hypnosis, 15:1-2, 2013 INTRODUCTION H ypnotic amnesia is a temporary forgetting induced by hypnotic suggestions. Amnesia can be engendered selective to a specific target in different sensory modalities. There are very few study focusing on hypnotic disruption of semantic memory and no electrophysiological research, to our knowledge. Evans et al. showed that impairment in semantic memory such as subjects’ number system can be obtained by hypnotic suggestions (1). In contrast, there are numerous electrophysiological studies about effects of hypnosis on event related potentials. Recent studies showed significant amplitude reductions in event-related potentials (P100, P300) during hypnotic blocking of visionand hypnotic numbness (2,3). However some studies observed opposite results: increased P300 amplitude (4). In this paper we present two cases and three additional unsuccessful hypnotic amnesia trials. We used hypnotic alteration of perception for a selected target number “7”which is used in go/no-go task. In other words we erased a number from subjects’ number system temporarily.EEG was recorded from four subjects during the task before and after hypnotic instructions. Our aim was to evaluate electrophysiological changes in ERPs that arise from altered perception during successful and also unsuccessfulforgetting of target number induced by hypnosis. All volunteers provided written informed consent. The study was approved by ethics committee of Istanbul Medical Faculty. Electrophysiological Evaluation of Disruption in Semantic Memory Induced by Hypnosis: Two Case Reports Ezgi Tuna Erdoğan, MD, Ece Kocagöncü, Msc, Adnan Kurt, Önder Uyar, MD, Sacit Karamürsel, MD Abstract: We reported two cases who were induced to forget number “7” by hypnotic suggestions. While subjects were performing a visual go/no-go task which includes number “7”, their electroencephalogram was recorded. Event related potentials in hypnotic state were compared to waking condition.We observed different results in ERPs between two subjectsand then discussed the limits of electrophysiological investigation of the effects of hypnosis on semantic memory (Sleep and Hypnosis 2013;15(1-2):11-15) Key words: Hypnotic amnesia, event related potentials, semantic memory CASE REPORT Address reprint requests to: Ezgi Tuna Erdoğan, MD, Istanbul University, Istanbul Faculty of Medicine, Department of Physiology, Matter and Mind Interactions Laboratory, Fatih, Istanbul 34093 Turkey Adana Numune Training and Research Hospital, Department of Neurology, Serinevler Street Ege Bağtur Boulvard Yüreğir, Adana 01240 Turkey Phone:+905336434749 E-mail: ezgituna.erdogan@gmail.com Accepted March 17, 2013