Temporal Information Entropy of the Blood-Oxygenation Level-Dependent Signals Increases in the Activated Human Primary Visual Cortex

Frontiers in Physics

DiNuzzo, Mauro¹  Maraviglia, Bruno²  Moraschi, Marta³  Mascali, Daniele³  Mangia, Silvia³  Giove, Federico³  Bussu, Giorgia³ 

[1] Division of Glial Disease and Therapeutics, Faculty of Health and Medical Sciences, Center for Basic and Translational Neuroscience, University of Copenhagen, Copenhagen, Denmark;Fondazione Santa Lucia (IRCCS), Rome, Italy;Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Rome, Italy

关键词: fMRI;    BOLD signal distribution;    Shannon information entropy;    visual stimulation;    Visual System;   

DOI  :  10.3389/fphy.2017.00007

学科分类：物理（综合）

来源: Frontiers

【 摘 要 】

Time-domain analysis of blood-oxygenation level-dependent (BOLD) signals allows the identification of clusters of voxels responding to photic stimulation in primary visual cortex (V1). However, the characterization of information encoding into temporal properties of the BOLD signals of an activated cluster is poorly investigated. Here, we used Shannon entropy to determine spatial and temporal information encoding in the BOLD signal within the most strongly activated area of the human visual cortex during a hemifield photic stimulation. We determined the distribution profile of BOLD signals during epochs at rest and under stimulation within small (19-121 voxels) clusters designed to include only voxels driven by the stimulus as highly and uniformly as possible. We found consistent and significant increases (2-4% on average) in temporal information entropy during activation in contralateral but not ipsilateral V1, which was mirrored by an expected loss of spatial information entropy. These opposite changes coexisted with increases in both spatial and temporal mutual information (i.e. dependence) in contralateral V1. Thus, we showed that the first cortical stage of visual processing is characterized by a specific spatiotemporal rearrangement of intracluster BOLD responses. Our results indicate that while in the space domain BOLD maps may be incapable of capturing the functional specialization of small neuronal populations due to relatively low spatial resolution, some information encoding may still be revealed in the temporal domain by an increase of temporal information entropy.

【 授权许可】

CC BY