Introduction

1. L R L L L L L L R L L L R General > Specific L R Specific > General R R L Attribute-based modulation in medial temporal activation during recollection of personal experiences D. R. Addis1,2, M. Moscovitch1, A. P. Crawley2, and M. P. McAndrews1,2 1 Department of Psychology, University of Toronto, Toronto, Ontario; 2 Toronto Western Research Institute, University Health Network, Toronto, Ontario Methods Participants • 6 male and 6 female participants (20 – 40 years) Pre-Scan Interview • Participants retrieved and described20 specific and 20 general AMs. • A “title” was provided for each memory, to be later used as a cue in the scanner. • Each memory was rated on a five – point scale for level of detail, emotionality and personal significance. Scanning Protocol • AM tasks: General and Specific AMs • Retrieve a general or specific AM in response to a visually presented AM title (6 sec) • Rate AM for either level of detail, emotionality or personal significance (4 sec) • Rest (6 sec) • Control task: Sentence completion • Complete a visually presented sentence (4 sec) • Rate for task difficulty (4 sec) • Rest (8 sec) • Control task: Size discrimination • Decide which of two named objects is larger (4 sec) • Rate for task difficulty (4 sec) • Rest (8 sec) • All tasks presented in a random order • Ten of each task presented in each run • Subjects completed two runs Post-Scan Interview • Participants retrospectively rated AMs for detail, emotionality and personal significance. • Correlated significantly with in-scan ratings (r = .80). Analyses • Direct contrasts: random effects analyses (AFNI) • AMs (General + Specific) – Control tasks • General Events – Specific Events • Parametric Modulation Analyses (SPM99) • Level of Detail • Level of Emotionality • Level of Personal Significance • Post-scan ratings used Results Contrast 1: AMs (general + specific) – Control tasks • AM retrieval resulted in increased activation of a predominantly medial and left – lateralised memory network. Introduction • Recent neuroimaging studies of memory retrieval have reported the activation of a medial and left – lateralised memory network that includes hippocampus, parahippocampus, posterior cingulate, precuneus, and medial frontal regions1. • The retrieval of autobiographical memories (AMs) appears to preferentially activate the hippocampus as part of this network1. • It remains unclear why the hippocampus exhibits preferential activation during AM retrieval. • Maguire & Mummery1 found that temporally specific AMs activated the hippocampus to a greater extent than personal facts. A more direct test of temporal specificity would be to compare unique, specific AMs to general, repeated AMs. • Maguire et al.2 reported that remembered AMs elicited greater left hippocampal activation than known AMs. Thus, attributes contributing to the re – experiencing of AMs, such as detail, emotionality and personal significance, may modulate hippocampal engagement. • We conducted an event – related fMRI study, testing three hypotheses: • That AM retrieval would result in the activation of a medial and left – lateralized network. • That specific AM retrieval should be associated with greater hippocampal activation than general AM retrieval if temporal specificity is a key modulator. • That hippocampal engagement should vary with the level of detail, emotionality and personal significance if re – experiencing is an important determinant. Parametric Modulation: Level of Emotionality • Level of Emotionality modulated activation of hippocampus bilaterally, bilateral anterior cingulate, L thalamus, L precuneus and L inferior parietal lobule. Parametric Modulation: Level of Personal Significance • Level of Personal Significance modulated activation of the L hippocampus, L medial frontal lobe, L superior frontal gyrus, R anterior cingulate, L parahippocampal gyrus, R temporal pole and bilateral parietal lobules. Contrast 2: General AMs – Specific AMs • No differences in hippocampal activation evident. • Retrieval of General AMs resulted in increased activation of R insula and R parahippocampal gyrus. • Retrieval of Specific AMs resulted in increased activation of the R ventrolateral prefrontal cortex and R temporal pole. Conclusions • We replicated previous findings of a predominantly medial and left – lateralised memory retrieval network. • There were no differences in hippocampal activation between the retrieval of memories for repeated, general AMs and temporally specific AMs, suggesting that this is not an important determinant of the level of hippocampal activation. • Hippocampal activation was modulated by the level of detail, emotionality and personal significance. This indicates that attributes of AMs contributing to re – experiencing are significant predictors of hippocampal activation. • Other brain regions also correlated with the level of re – experiencing, though the regions differed depending on the particular attribute, suggesting the activation of different memory networks of which the hippocampus is a key structure. Parametric Modulation: Level of Detail • Level of detail modulated activation of R hippocampus, bilateral medial frontal lobe, bilateral anterior cingulate, L superior/middle temporal gyrus, bilateral precuneus and R supramarginal gyrus. References 1 Maguire, E.A., & Mummery, C.J. (1999). Differential modulation of a common memory network revealed by PET. Hippocampus, 9, 54 – 61. 2 Maguire, E.A., Vharga-Khadem, F. & Mishkin, M. (2001). The effects of bilateral hippocampal damage on fMRI regional activations and interactions during memory retrieval. Brain, 124, 1156 – 1170.