Task-dependent functional organizations of the visual ventral stream

Han-Gue Jo,Conrad Baumann,Barbara Schulte Holthausen,Junji Ito,Sonja Grün,Thilo Kellermann,Ute Habel

doi:10.1038/s41598-019-45707-w

Han-Gue Jo, Conrad Baumann + Show 5 more

Open Access

https://doi.org/10.1038/s41598-019-45707-w

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Abstract

The visual hierarchy of the ventral stream has been widely studied. However, it remains unclear how the hierarchical system organizes its functional coupling during top-down cognitive process. The present fMRI study investigated task-dependent functional connectivity along the ventral stream, while twenty-eight participants performed object recognition tasks that required different types of visual processing: i) searching or ii) memorizing visual objects embedded in natural scene images or iii) free viewing of the same images. Utilizing a seed-based approach that explicitly compared task-specific BOLD time-series, we identified task-dependent functional connectivity of the visual ventral stream, demonstrating different correlation structures. Searching for a target object manifested both correlated and anti-correlated structures, separating the visual areas V1 and V4 from the posterior part of the inferior temporal cortex (PIT). In contrast, the ventral stream structure remained correlated during memorizing objects, but increased the correlation between the right V4 and PIT. On the other hand, V1 and V4 showed task-dependent activation, whereas PIT was deactivated. These results highlight the context-dependent nature of the visual ventral stream and shed light on how the visual hierarchy is selectively organized to bias object recognition toward features of interest.

Highlights

The visual ventral stream is a series of hierarchical processing stages from the primary visual cortex V1 to inferior temporal cortex IT, in which neural interactions along this hierarchy enable us to recognize visual objects[1,2]
As significant activation clusters were observed beyond the visual areas, we further examined the interactions with these clusters, i.e., the left and right supramarginal gyri, left and right frontal poles, and the right precentral gyrus
The connectivity across the identified regions of interests (ROIs) was organized into correlated and anti-correlated structures according to the context of visual cognition

Summary

Introduction

The visual ventral stream is a series of hierarchical processing stages from the primary visual cortex V1 to inferior temporal cortex IT, in which neural interactions along this hierarchy enable us to recognize visual objects[1,2]. The ventral stream requires different functional properties of the hierarchy to incorporate visual features of interest into object recognition[3,4], which may alter the functional coupling of the visual hierarchy according to task-goals To address this hypothesis, here we examine task-dependent functional connectivity of the ventral stream, utilizing a seed-based approach investigating task-specific functional correlations of BOLD time-series. Since memory-related neural activation is feature-selective in the ventral stream[9,10], the hierarchy system has been suggested to play a significant role in memorizing objects[11,12,13,14] The rationale behind this view is that if visual perception emerges via the hierarchical system, the hierarchical process might be crucial for storing visual information into memory. We show to which extent task-dependent connectivity strengths across the identified ROIs increases or decreases during each of the visual search, memory, and free view condition

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