Perceived and mentally rotated contents are differentially represented in cortical depth of V1

Polina Iamshchinina,Daniel Kaiser,Nikolaus Weiskopf,Oliver Speck,Radoslaw Martin Cichy,Alessandro Sciarra,Daniel Haenelt,Emrah Duezel,Hendrik Mattern,Renat Yakupov,Falk Luesebrink

doi:10.1038/s42003-021-02582-4

Abstract

Primary visual cortex (V1) in humans is known to represent both veridically perceived external input and internally-generated contents underlying imagery and mental rotation. However, it is unknown how the brain keeps these contents separate thus avoiding a mixture of the perceived and the imagined which could lead to potentially detrimental consequences. Inspired by neuroanatomical studies showing that feedforward and feedback connections in V1 terminate in different cortical layers, we hypothesized that this anatomical compartmentalization underlies functional segregation of external and internally-generated visual contents, respectively. We used high-resolution layer-specific fMRI to test this hypothesis in a mental rotation task. We found that rotated contents were predominant at outer cortical depth bins (i.e. superficial and deep). At the same time perceived contents were represented stronger at the middle cortical bin. These results identify how through cortical depth compartmentalization V1 functionally segregates rather than confuses external from internally-generated visual contents. These results indicate that feedforward and feedback manifest in distinct subdivisions of the early visual cortex, thereby reflecting a general strategy for implementing multiple cognitive functions within a single brain region.

Highlights

Primary visual cortex (V1) in humans is known to represent both veridically perceived external input and internally-generated contents underlying imagery and mental rotation
Harnessing the fine-grained resolution of 7 T fMRI, we were able to resolve the functional segregation of signals underlying mentally rotated and perceived contents in V1: perceptual signals were dominant at the middle depth of V1, whereas mentally rotated contents were found in the superficial and deep bins
While our results are consistent with the previous fMRI studies at the standard resolution showing that V1 houses representations of both perceived and mentally rotated contents[4,5] (Supplementary Fig. 1B), our findings provide the first functional explanation for externally induced and internally generated representations during mental rotation overlapping on a 2D map of cortex, yet functionally distinct in a 3D cortical model

Summary

Introduction

Primary visual cortex (V1) in humans is known to represent both veridically perceived external input and internally-generated contents underlying imagery and mental rotation. At the same time perceived contents were represented stronger at the middle cortical bin These results identify how through cortical depth compartmentalization V1 functionally segregates rather than confuses external from internallygenerated visual contents. The perceived contents were strongest at the middle cortical depth bins, while mentally rotated contents dominated in the superficial and deep cortical bins These results show how the perceived and mentally rotated contents are mediated by functionally distinct neural representations, explain why externally induced and internally generated contents are not confused, and supports the view of V1 as a dynamic ‘blackboard’ updated through connections from higher-order areas rather than a low-level stage of hierarchical processing

Methods

Results

Conclusion