Neural correlates of encoding pictures into long-term memory: the influence of advance information Danying Wang A dissertation submitted for the degree of Doctor of Philosophy of the University College London. Institute of Cognitive Neuroscience University College London 2015 1 Declaration I, Danying Wang, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. 2 Abstract It has been shown that neural activity before an event influences the likelihood that the event will later be remembered. This doctoral thesis aimed to clarify the functional role of anticipatory activity in long-term memory by manipulating the amount of advance information that is available about an upcoming pictorial encoding event. The first three studies employed scalp-recorded electrical brain activity. Experiment 1 investigated how advance information about the physical form of an object (a perceptually impoverished outline or detailed photograph) affects encoding-related processes. In the temporal domain, event-related potentials (ERPs) showed encoding-related differences regardless of type of advance information. In the frequency domain, decreases in theta and alpha power predicted later memory, but only for photographs. Experiment 2 addressed how preparation time (1.5 or 3 s) affects the encoding of photographs. Only when the preparatory interval was long did anticipatory ERP activity predict encoding success. Experiment 3 aimed to induce a brain state conducive to effective encoding by asking participants to prepare for a delayed match-to-sample task known to involve the hippocampus. A memory probe during the anticipation period suggested that encoding was indeed better before an episodic, rather than control, version of the task. Finally, Experiments 4 and 5 used behavioural measures to address the relationship between encoding-related anticipatory processes and overall memory performance. Experiment 4 compared retrieval under full and divided attention conditions. When retrieval resources were limited by a secondary task, memory performance was better following longer preparation times during encoding. This pattern was not seen in Experiment 5, which contrasted easy and difficult secondary task conditions. Together, the doctoral thesis suggests that the more information is available to guide preparation, the more likely it is that anticipatory activity influences encoding. Individuals may be able to actively employ preparatory processes to strengthen memory under certain circumstances. 3 Acknowledgements First, I would like to express my sincere gratitude to my supervisor, Dr Leun Otten, who has been always supportive during the past four years. Leun has always been motivating when I wanted to try out things like new experimental paradigms or analyses. She is also the most insightful one to guide me when some of my ideas did not work. I cannot imagine how I can finish my PhD works without her invaluable dedication. In addition, I would like to thank the past and current lab members of the cognitive electrophysiological group. I want to say thank you especially to Drs Eva Bauch, Giulia Galli and Matthias Gruber, for their kind supports, patience and help when I did not know anything about EEG. I still remember what they taught me in details when I was writing up my works in this thesis. I want to thank Jiangyi Xia for being supportive throughout my time in London. I think of Jiangyi as a best friend, a big sister and someone I really want to talk to when I have difficulties in research or life. I also would like to thank my friends from the ICN, Chen and Wenjing for the fun discussions on research. I thank the ICN administrative staff for their cares and efforts to make things a lot easier. I thank all my friends in the UK and China for helping me be less stressful. Most importantly, I want to say thank you to all my family members especially my parents. Because of their supports and love, I started to pursue a PhD in such a faraway country. My dad and mom always believe in me even when I felt difficult. Thank you both for always being there for me. I will always love you both unconditionally. 4 Contents Chapter 1: Introduction ······················································· 18 1.1 Long-term Memory ········································································ 19 1.1.1 General introduction to episodic memory ··········································· 19 1.1.2 Neural models of episodic memory··················································· 21 1.1.3 Recollection and familiarity ··························································· 23 1.2 Measuring the neural pattern of successful memory formation: The subsequent memory paradigm ··············································································· 28 1.3 Encoding-related brain activity after an event ······································· 30 1.3.1 Brain regions correlated with encoding success ···································· 30 1.3.2 Encoding-related electrical brain activity ············································ 32 1.3.3 Encoding-related activity and encoding manipulations ···························· 34 1.3.4 Encoding-related activity and retrieval manipulations ····························· 41 1.4 How brain activity before an event influences processing on the event ········· 43 1.5 Encoding-related brain activity before an event ····································· 48 1.6 Neural correlates of retrieval ····························································· 55 1.7 Research aims ················································································ 58 1.8 Summary of introduction ································································· 64 Chapter 2: General methods ·················································· 66 2.1 Studying the relationship between the brain and cognitive processes with electroencephalography ········································································ 66 2.2 Event-related potentials ··································································· 68 2.3 Time-frequency analyses ·································································· 73 2.4 Behavioural analyses of recognition memory ········································· 80 Chapter 3: Does amount of advance information influence pre- stimulus encoding-related activity? ·········································· 82 5 3.1 Experiment 1: The influence of graded perceptual preparation on pre-stimulus encoding-related activity ······································································· 82 3.1.1 Introduction ·············································································· 82 3.1.2 Methods ··················································································· 84 Participants ·············································································································· 84 Stimulus Material ····································································································· 84 Procedure················································································································· 88 EEG acquisition ······································································································· 89 EEG analyses ··········································································································· 89 3.1.3 Results ···················································································· 91 Task Performance ···································································································· 91 Summary of behavioural findings ············································································ 94 Encoding-related activity preceding pictures ·························································· 95 Encoding-related activity after pictures ································································ 100 Cue-related activity preceding pictures irrespective of subsequent memory ········ 105 3.1.4 Discussion ··············································································· 106 3.2 Experiment 2: The influence of amount of time available before an event on pre-stimulus encoding-related activity ····················································· 112 3.2.1 Introduction ············································································· 112 3.2.2 Methods ·················································································· 114 Participants ············································································································ 114 Stimulus Material ··································································································· 114 Procedure··············································································································· 115 EEG acquisition ····································································································· 117 EEG analyses ········································································································· 117 3.2.3 Results ··················································································· 119 6 Task Performance ·································································································· 119 Summary of behavioural findings ··········································································