The Episodic Nature of Experience: A Dynamical Systems Analysis

Abstract

Context is an important construct in many domains of cognition, including learning, memory, and emotion. We used dynamical systems methods to demonstrate the episodic nature of experience by showing a natural separation between the scales over which within-context and between-context relationships operate. To do this, we represented an individual's emails extending over about 5 years in a high-dimensional semantic space and computed the dimensionalities of the subspaces occupied by these emails. Personal discourse has a two-scaled geometry with smaller within-context dimensionalities than between-context dimensionalities. Prior studies have shown that reading experience (Doxas, Dennis, & Oliver, 2010) and visual experience (Sreekumar, Dennis, Doxas, Zhuang, & Belkin, 2014) have a similar two-scaled structure. Furthermore, the recurrence plot of the emails revealed that experience is predictable and hierarchical, supporting the constructs of some influential theories of memory. The results demonstrate that experience is not scale-free and provide an important target for accounts of how experience shapes cognition.

Criticality in the brain: A synthesis of neurobiology, models and cognition

“…Indeed it has been shown that reaction times between sequential trials show long-range correlations across a wide diversity of tasks (Palva and Palva, 2011;Thornton and Gilden, 2005). This is perhaps not surprising, given that, outside the scanner, human activity (Sreekumar et al, 2016;Sreekumar et al, 2014) and memory (Nielson et al, 2015) show a complex temporal structure that scales across many orders of magnitude. Detailed analyses of reaction time data in typical psychophysics experiments support the presence of a power law structure (Van Orden et al, 2005).…”

Hippocampal Activity Patterns Reflect the Topology of Spaces: Evidence from Narrative Coding

“…Some studies have reported that the hippocampus is not involved in representing unitary items (e.g., Ross et al, 2017). Milivojevic et al (2016) suggested that the character and location hippocampal representations in their study may be abstracted versions of those items across multiple experiences over the course of the movie and therefore may behave more like a gist or lower-level context for those items.…”

“…Most characters and locations are shared between the two narratives, and the narratives are interleaved in the movie, reducing confounds relating to temporal co-occurrence and visual similarity (both of which were further controlled for by statistical analyses). A whole-brain searchlight using representational similarity analysis (Kriegeskorte et al, 2008) revealed that hippocampal activity patterns differentiated between overall narrative contexts, as well as individual people and locations within those contexts. Furthermore, hippocampal activity corresponding to the two narratives gradually became more distinct over time.…”

“…There are neuroanatomical differences between the posterior and anterior parts of the hippocampus (pHPC and aHPC, respectively) in terms of both proportions of CA1-CA3 and DG subfields as well as their long-range connections to other parts of the brain that have led to hypotheses regarding functional specialization along the hippocampal long axis (for review, see Poppenk et al, 2013). The DG plays an important role in pattern separation and CA3 in pattern completion (for a recent review, see Knierim and Neunuebel, 2016); and given the higher ratio of DG/CA in the pHPC and lower ratio in the aHPC, Poppenk et al (2013) proposed that the pHPC codes for events with sharper lowlevel detail via pattern separation whereas the aHPC codes at a broader scale for high-level gist by abstracting over multiple experiences via pattern completion. If this proposal is correct, one would expect higher-level narrative contexts as well as abstractions over multiple experiences of characters and locations to eventually be represented in the aHPC, whereas more specific location and characters to be represented in the pHPC.…”

“…The perirhinal cortex (PRC) exhibits preferential connectivity with the aHPC, whereas the parahippocampal cortex (PHC) shows preferential connectivity with the pHPC (Libby et al, 2012). Under conditions that remove the strong inhibition of inputs from these cortical regions to the hippocampal formation (de Curtis and Paré, 2004), this pattern of connectivity suggests that the aHPC receives fine-grained local configurational information (such as items and the associations between them) from the PRC, which gets bound to the relevant broad level context representation.…”