Neurofunctional Segmentation Shifts in the Hippocampus

Jennifer L Robinson; Xinyu Zhou; Ryan T Bird; Mackenzie J Leavitt; Steven J Nichols; Sara K Blaine; Gopikrishna Deshpande

doi:10.3389/fnhum.2021.729836

Neurofunctional Segmentation Shifts in the Hippocampus

Front Hum Neurosci. 2021 Nov 1:15:729836. doi: 10.3389/fnhum.2021.729836. eCollection 2021.

Authors

Jennifer L Robinson^{1

2

3

4}, Xinyu Zhou^{2

5}, Ryan T Bird¹, Mackenzie J Leavitt¹, Steven J Nichols¹, Sara K Blaine^{1

3

4}, Gopikrishna Deshpande^{1

2

3

4

6

7

8}

Affiliations

¹ Department of Psychological Sciences, Auburn University, Auburn, AL, United States.
² Department of Electrical and Computer Engineering, Auburn University Magnetic Resonance Imaging Research Center, Auburn University, Auburn, AL, United States.
³ Center for Neuroscience Initiative, Auburn University, Auburn, AL, United States.
⁴ Alabama Advanced Imaging Consortium, Birmingham, AL, United States.
⁵ Quora Inc., Mountain View, CA, United States.
⁶ Key Lab for Learning and Cognition, School of Psychology, Capital Normal University, Beijing, China.
⁷ Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bengaluru, India.
⁸ Center for Brain Research, Indian Institute of Science, Bengaluru, India.

Abstract

The hippocampus is one of the most phylogenetically preserved structures in the mammalian brain. Engaged in a host of diverse cognitive processes, there has been increasing interest in understanding how the hippocampus dynamically supports these functions. One of the lingering questions is how to reconcile the seemingly disparate cytoarchitectonic organization, which favors a dorsal-ventral layering, with the neurofunctional topography, which has strong support for longitudinal axis (anterior-posterior) and medial-lateral orientation. More recently, meta-analytically driven (e.g., big data) approaches have been employed, however, the question remains whether they are sensitive to important task-specific features such as context, cognitive processes recruited, or the type of stimulus being presented. Here, we used hierarchical clustering on functional magnetic resonance imaging (fMRI) data acquired from healthy individuals at 7T using a battery of tasks that engage the hippocampus to determine whether stimulus or task features influence cluster profiles in the left and right hippocampus. Our data suggest that resting state clustering appears to favor the cytoarchitectonic organization, while task-based clustering favors the neurofunctional clustering. Furthermore, encoding tasks were more sensitive to stimulus type than were recognition tasks. Interestingly, a face-name paired associate task had nearly identical clustering profiles for both the encoding and recognition conditions of the task, which were qualitatively morphometrically different than simple encoding of words or faces. Finally, corroborating previous research, the left hippocampus had more stable cluster profiles compared to the right hippocampus. Together, our data suggest that task-based and resting state cluster profiles are different and may account for the disparity or inconsistency in results across studies.

Keywords: 7T; clustering; connectivity; fMRI; hierarchical clustering; memory; topography.