Activating the Medial Temporal Lobe during Oddity Judgment for Faces and Scenes

Abstract

Impairments in visual discrimination beyond long-term declarative memory have been found in amnesic individuals, with hippocampal lesions resulting in deficits in scene discrimination and perirhinal cortex damage affecting object discrimination. To complement these findings, the present functional magnetic resonance imaging study found that in healthy participants oddity judgment for novel trial-unique scenes, compared with face or size oddity, was associated with increased posterior hippocampus and parahippocampal cortex activity. In contrast, perirhinal and anterior hippocampus activity was observed during unfamiliar trial-unique face oddity judgment, when contrasted with scene or size oddity tasks. Activity in all of these regions decreased as the stimuli were repeated across trials, reflecting the participants' increasing familiarity with the stimuli. This change was significant in all areas, with the exception of the perirhinal cortex, right anterior hippocampus, and to a lesser extent the left anterior hippocampus during face oddity judgment. One possibility is that the activity in these regions may not reflect entirely episodic memory encoding but, in part, processes beyond the mnemonic domain. Thus, the perirhinal cortex, and possibly anterior hippocampus, may play a more generic role in the discrimination and processing of objects.

Evidencing a place for the hippocampus within the core scene processing network

“…Unlike several previous studies that have looked at HC responses during scene perception [Barense et al, 2010; Lee et al, 2008; Lee and Rudebeck, 2010b; Mundy et al, 2012; Zeidman et al, 2015], we found stronger group‐level (bilateral) activation in the anterior, rather than posterior, HC (although see Lee et al, 2013). As has been discussed elsewhere, spatial smoothing of EPI data can lead to “blurring” between adjacent anatomical ROIs, such as between PHG and posterior HC [Reber et al, 2002].…”

“…Overall, the results of our group‐level analyses were consistent with previous studies that observed strong scene‐sensitivity in these regions during standard localiser tasks [Bettencourt and Xu, 2013; Epstein, 2008; Epstein and Kanwisher, 1998; Lee et al, 2008; Spiridon et al, 2006]. Our main scene‐selective contrast revealed significant bilateral activity in each tested ROI at the whole brain level, including HC and TOS.…”

“…Critically, this one‐back localiser task, which involved rapidly presented scenes with minimal mnemonic demand, yielded strong ( Z  > 7) bilateral activation in the HC bilaterally, supporting a task‐independent role of the HC in complex scene processing [Barense et al, 2010; Lee et al, 2008; Lee and Rudebeck, 2010b]. Unlike several previous studies that have looked at HC responses during scene perception [Barense et al, 2010; Lee et al, 2008; Lee and Rudebeck, 2010b; Mundy et al, 2012; Zeidman et al, 2015], we found stronger group‐level (bilateral) activation in the anterior, rather than posterior, HC (although see Lee et al, 2013).…”

“…We provide, therefore, the first detailed investigation of scene‐sensitivity within a large sample and across a range of regions. While we evaluate the response properties of the “core” scene processing network—namely PHG, RSC, and TOS—a novel aspect of this study was the inclusion of the HC as a component of this network, given its purported role in the representation of complex and conjunctive scenes [Barense et al, 2010; Lee et al, 2008; Mundy et al, 2013] and contributions to scene construction [Maguire and Mullally, 2013; Zeidman et al, 2015]. …”

“…An important question, therefore, is whether the HC also responds preferentially and consistently to scenes, as seen in these other “core” scene processing regions. As previous fMRI studies investigating scene perception and memory in the HC have used anatomical or group‐defined regions‐of‐interest (ROIs), rather than functional ROIs defined within individual subjects [Barense et al, 2010; Lee et al, 2008; Mundy et al, 2013], it is currently unclear whether this is the case.…”