Abstract
Precuneus/posterior cingulate cortex (PCu/PCC) are key components of a midline network, activated during rest but also in tasks that involve construction of scene or situation models. Despite growing interest in PCu/PCC functional alterations in disease and disease risk, the underlying neurochemical modulators of PCu/PCC's task‐evoked activity are largely unstudied. Here, a multimodal imaging approach was applied to investigate whether interindividual differences in PCu/PCC fMRI activity, elicited during perceptual discrimination of scene stimuli, were correlated with local brain metabolite levels, measured during resting‐state 1H‐MRS. Forty healthy young adult participants completed an fMRI perceptual odd‐one‐out task for scenes, objects and faces. 1H‐MRS metabolites N‐acetyl‐aspartate (tNAA), glutamate (Glx) and γ‐amino‐butyric acid (GABA+) were quantified via PRESS and MEGA‐PRESS scans in a PCu/PCC voxel and an occipital (OCC) control voxel. Whole brain fMRI revealed a cluster in right dorsal PCu/PCC that showed a greater BOLD response to scenes versus faces and objects. When extracted from an independently defined PCu/PCC region of interest, scene activity (vs. faces and objects and also vs. baseline) was positively correlated with PCu/PCC, but not OCC, tNAA. A voxel‐wise regression analysis restricted to the PCu/PCC 1H‐MRS voxel area identified a significant PCu/PCC cluster, confirming the positive correlation between scene‐related BOLD activity and PCu/PCC tNAA. There were no correlations between PCu/PCC activity and Glx or GABA+ levels. These results demonstrate, for the first time, that scene activity in PCu/PCC is linked to local tNAA levels, identifying a neurochemical influence on interindividual differences in the task‐driven activity of a key brain hub.
Highlights
The precuneus/posterior cingulate cortex (PCu/PCC) is a key brain hub and component of a core midline system, activated during autobiographical memory, prospection, contextual retrieval, spatial navigation, and mental scene construction (Andrews-Hanna, Saxe, & Yarkoni, 2014; Bar, Aminoff, Mason, & Fenske, 2007; Buckner & Carroll, 2007; Hassabis & Maguire, 2007; van den Heuvel & Sporns, 2013)
There was a significant positive correlation between the blood-oxygenation-level dependent (BOLD) percent signal change for scenes > faces + objects in our a priori PCu/PCC region of interest (ROI) and the concentration of tNAA in the PCu/PCC 1H-MRS voxel (r[33] = 0.41, p = 0.017, Bayes factor (BF)+0 = 6.62, 95% Bayes CI = 0.09 and 0.65; see Figure 3a)
There were no significant correlations between PCu/PCC BOLD for scenes > faces + objects and either PCu/PCC Glx (r[32] = −0.27, p = 0.14, BF01 = 1.62, 95% Bayes CI = −0.54 and 0.09), or PCu/PCC GABA+ (r[24] = 0.27, p = 0.21, BF01 = 1.83, 95% Bayes CI = −0.14 and 0.58; see Figure 3a)
Summary
The precuneus/posterior cingulate cortex (PCu/PCC) is a key brain hub and component of a core midline system, activated during autobiographical memory, prospection, contextual retrieval, spatial navigation, and mental scene construction (Andrews-Hanna, Saxe, & Yarkoni, 2014; Bar, Aminoff, Mason, & Fenske, 2007; Buckner & Carroll, 2007; Hassabis & Maguire, 2007; van den Heuvel & Sporns, 2013). Parahippocampal and entorhinal cortices, plus the hippocampal formation (Hutchison, Culham, Everling, Flanagan, & Gallivan, 2014; Kravitz, Saleem, Baker, & Mishkin, 2011; Parvizi, Van Hoesen, Buckwalter, & Damasio, 2006; Passarelli et al, 2018), a recent proposal maintains that the PCu/PCC anchors a posteromedial or extended navigation system critical for the construction of “scene” or more generally “situation” models (comprising a particular time, place, and context; Ranganath & Ritchey, 2012) Such situation models are argued to support a diverse array of cognitive processes, including episodic memory and future thinking, spatial navigation, and scene imagination (Murray, Wise, & Graham, 2017; Ranganath & Ritchey, 2012). A situation “model” allows the viewer to construct a rich and coherent percept of a “place,” extrapolating beyond the sensory input, critical both for navigation in space as well as for scaffolding episodic memories (Murray et al, 2017; Zeidman & Maguire, 2016)
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