Goal‐directed interaction of stimulus and task demand in the parahippocampal region

Abstract

The hippocampus and parahippocampal region are essential for representing episodic memories involving various spatial locations and objects, and for using those memories for future adaptive behavior. The "dual-stream model" was initially formulated based on anatomical characteristics of the medial temporal lobe, dividing the parahippocampal region into two streams that separately process and relay spatial and nonspatial information to the hippocampus. Despite its significance, the dual-stream model in its original form cannot explain recent experimental results, and many researchers have recognized the need for a modification of the model. Here, we argue that dividing the parahippocampal region into spatial and nonspatial streams a priori may be too simplistic, particularly in light of ambiguous situations in which a sensory cue alone (e.g., visual scene) may not allow such a definitive categorization.Upon reviewing evidence, including our own, that reveals the importance of goaldirected behavioral responses in determining the relative involvement of the parahippocampal processing streams, we propose the Goal-directed Interaction of Stimulus and Task-demand (GIST) model. In the GIST model, input stimuli such as visual scenes and objects are first processed by both the postrhinal and perirhinal corticesthe postrhinal cortex more heavily involved with visual scenes and perirhinal cortex with objects-with relatively little dependence on behavioral task demand. However, once perceptual ambiguities are resolved and the scenes and objects are identified and recognized, the information is then processed through the medial or lateral entorhinal cortex, depending on whether it is used to fulfill navigational or nonnavigational goals, respectively. As complex sensory stimuli are utilized for both navigational and non-navigational purposes in an intermixed fashion in naturalistic settings, the hippocampus may be required to then put together these experiences into a coherent map to allow flexible cognitive operations for adaptive behavior to occur.

Reunification of Object and View-Center Background Information in the Primate Medial Temporal Lobe

“…We hypothesize that in addition to a figure, which is processed as an object, the ventral pathway would process a background, which might have been observed as a scene-selective response in previous studies ( Epstein and Kanwisher, 1998a ; Kornblith et al, 2013 ; Vaziri et al, 2014 ). Consistent with this idea, recent rodent studies have reported that the PRC of the ventral pathway-MTL stream contributes to spatial or visual scene processing as well as conventional item processing ( Fiorilli et al, 2021 ; Lee et al, 2021 ).…”

The fasciola cinereum subregion of the hippocampus is important for the acquisition of visual contextual memory

“…Our findings do not fit the traditional model and suggest that modifications of the model are in order. Specifically, recent studies have raised the possibility that parahippocampal region areas may not be as sharply segregated as once thought (Hunsaker et al, 2013, Knierim et al, 2014, Park et al, 2017, Yoo and Lee, 2017, Lee et al, 2021. Furthermore, a recent study suggested that the POR also projects heavily to the LEC and that the connectivity between the POR and MEC is not as prominent as previously thought (Doan et al, 2019).…”

Content-specific vulnerability of recent episodic memories in Alzheimer's disease

“…Hence the involved functional architecture differs for multimodal objects and scene memories due to biased pathways of information processing (cf. Fiorilli et al, 2021 ; Lee et al, 2021 ; but note the described profound overlap as well). Under healthy conditions, multimodal representations may enhance memorability because a memory can be accessed via multiple ways (e.g.…”

“…In Alzheimer's disease particularly multimodal representation areas like the perirhinal cortex (cf. Fiorilli et al, 2021 ; Bussey et al, 2005 ; Lee et al, 2021 ) are affected early on, presumably leading to an increased vulnerability for certain object memories. Another appealing mechanism that may determine differential memorability effects in Alzheimer's disease are attentional and perceptual mechanisms.…”