Organisation of higher-order cognitive functions in the posterior parietal cortex

2094 

Abstract Submission 

Katrin Karadachka¹, Rogier Mars^1,2, W. Pieter Medendorp¹

¹Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Gelderland, ²Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging Centre, Oxford, United Kingdom

Katrin Karadachka, MSc  
Donders Institute for Brain, Cognition and Behaviour, Radboud University
Nijmegen, Gelderland

Rogier Mars  
Donders Institute for Brain, Cognition and Behaviour, Radboud University|Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging Centre
Nijmegen, Gelderland|Oxford, United Kingdom

W. Pieter Medendorp  
Donders Institute for Brain, Cognition and Behaviour, Radboud University
Nijmegen, Gelderland

Posterior parietal lobe (PPC) expansion can be observed in various branches of the primate phylogenetic tree, with its most dramatic expansion evident in the inferior parietal lobe of the human (Goldring & Krubitzer, 2017). Human PPC and nearby temporoparietal junction have been shown to be involved in a variety of cognitive challenges (Coslett & Schwartz, 2018; Rizzolatti & Rozzi, 2018; Medendorp & Heed, 2019). However, the precise neural loci and mechanisms supporting such, often uniquely human, cognitive functions remains a mystery. In this study, we aim to untangle general principles of overall organisation in the human PPC based on functional and anatomical data.

Data for our preliminary analysis, consist of functional task and anatomical data of 15 adult participants, part of the S1200 subjects release of the Human Connectome Project (HCP) database (Van Essen et al. 2013). We selected contrasts from task fMRI data for each participant provided by the HCP database. We were interested in working memory, language and social comprehension, mathematical computation, and relational processing. We also included motor behavior as a low-level baseline. General linear model analysis was applied on the task fMRI data via FSL's FEAT resulting in individual and averaged activation maps for each contrast per task. Maps of the selected contrasts were then transformed from volumetric to surface space using HCP's neuroimaging analysis toolbox Workbench. In order to understand how these maps relate to each other, we embed functional data projected onto the cortical surface into a 2-D space (Mars et al., 2018a).

Within the whole brain, we find that motor tasks cluster closer together in space but tasks such as relational reasoning, language, mathematical computation and working memory are more spread out overall and across individuals (Figure 1A, Figure 1B). In particular, on the right hemisphere mathematical computation, working memory and relational reasoning are situated closer together in space, whereas language and social comprehension are situated further away (Figure 1B). These patterns can be reflected on the cortical surface with mathematical computation, relational reasoning and working memory activating lateral and dorsal prefrontal cortex, anterior cingulate and inferior parietal lobe (Figure 1C). On the other hand, language and social comprehension mainly activate the temporal lobe with some activity in the orbitofrontal cortex.

We then examine the 2D embedding of the higher cognitive tasks within the PPC. We defined a region of interest enclosing several posterior parietal areas, following the multi-modal parcelation by Glasser et al., 2013 (Figure 2C). Preliminary results show that maths, relational reasoning and working memory cluster closer together, indicating an underlying similarity based on their functional connectivity profiles. On the other hand language and social comprehension are further away from the other tasks across both hemispheres (Figure 2A, Figure 2B). In sum, it seems that higher cognitive functions, although not entirely separate, largely rely on different neural underpinnings in PPC.

We plan to further push this concept by examining functional connectivity embedding within the superior and inferior division of the parietal lobe. The superior and inferior division of the parietal lobe differ according to their functional and cytoarcitectonic profiles (Caspers & Zilles, 2018), thus we think we might uncover unique patterns of organization. In addition, we aim to relate this 2D functional embedding to the underlying anatomy of the PPC by examining the white matter tracts that form the connectional pattern of this region following Warrington et al. (2020). We are interested in exploring how well structure and function map to each other in the posterior parietal cortex. Lastly, our preliminary results presented here are based only on 15 subjects but we plan expand our sample size for our full analysis.

Anatomy and Functional Systems ¹

Cortical Anatomy and Brain Mapping ²

ADULTS

Cognition

Cortex

FUNCTIONAL MRI

MRI

STRUCTURAL MRI

Structures

Tractography

White Matter

WHITE MATTER IMAGING - DTI, HARDI, DSI, ETC