We developed a detailed model of spatial memory and imagery, incorporating representations of objects into egocentric parietal and allocentric medial temporal representations to combine the content and context of an experience within flexible representations (Bicanski and Burgess, 2018). This new model offers an account on how the brain stores complex representations in memory, via associating the content of an experience with the surrounding context, and can flexibly use these representations to generate imagery to guide future behaviour. This model also incorporates the provision for imagined movement via connections between grid cells in entorhinal cortex and hippocampal place cells. The model is important in consolidating our understanding and making predictions about how memories are formed, retrieved and updated within a complex system of brain regions.
To investigate and model the interactions between place cells and grid cells to support dynamic imagery and memory representations, we have proposed a model of recognition memory in which grid cells encode translation vectors between features of an attended stimulus and thus guide eye movements between expected features to accumulate evidence to identify experienced stimuli (Bicanski and Burgess, 2019). We also modelled the interactions between place and grid cells for optimally inferring our environmental location (Evans & Burgess, NeurIPS, 2019).
We developed a rich setting (based on Harry Potter’s Hogwarts) in immersive and desk-top virtual reality (VR) to test memory for object-locations in different contexts, and combined this with fMRI to investigate its neural bases. We taught participants routes through a ”memory palace” within this environment to memorise long lists of items in order, and demonstrated a role for grid cells in this process by predicting fMRI activity in entorhinal cortex as a function of the orientation of each participant’s grid-like patterns during navigation relative to the orientation of the routes that they used (Constantinescu, Castegnaro et al., in prep). We also identified the brain regions supporting learning of the spatial context of a fearful stimulus (Suarez-Jimenez et al., 2018), and examined the effects of semantic and temporal similarity in defining the context of list elements and their differential neural bases (Convertino, Geerts & Burgess, in prep), and performed an fMRI experiment to test for grid-coding of semantic and temporal context (Convertino, Constantinescu & Burgess, in prep). We then developed a general model of context-dependent learning and memory in a wide variety of tasks, in collaboration with Sam Gershman and Kim Stachenfeld (Geerts, Gershman, Burgess, Stachenfeld, Psychological Review, in press).
We examined memory for multi-element events, and showed that both retrieval of presented associations and inference of missing ones reflect a process of pattern completion. This process was not affected by repeated presentations of individual associations and was consistent with an attractor network simulation of CA3 (Ihksan et al., 2020). We also showed that overlapping events undergo pattern separation in memory (Zotow & Burgess, 2020), that negative emotional content reduces the coherence of memory for the events (Bisby et al., 2018), and that a long delay it did not impair new items being associated to the previously encoded items and forming a closed loop of associations (Joensen et al., in prep).
We investigated the consolidation into long term memory of episodes (short video clips), showing that deliberate memory for the clips after one week was improved by brief wakeful rest after encoding, whereas intrusive thoughts them during the week were reduced (Horlyck et al., 2019). In this same paradigm, we found that hippocampal activity during the rest period correlates with subsequent deliberate memory whereas activity in the amygdala correlated with intrusive thoughts (Horlyck et al., in prep).
We have developed a model of the consolidation of episodic memories into semantic memory, including how memories are reconstructed or new are imagined, and explaining the nature of gist-based distortions and the effects of hippocampal damage (Spens & Burgess, submitted).
