Functional connectome beyond fMRI: methodology and application

The human brain is a highly complex and integrative system wherein ongoing signaling, information exchange and processing occur in dynamic response to a wide variety of endogenous neurophysiological processes and external cognitive demands. The integrative nature depends largely upon neural synchronization across multiple distributed regions and systems, therefore forming dynamic, organized large-scale networks (i.e., functional connectome). To date, the blood-oxygen-level-dependent (BOLD) functional MRI remains the dominant technique for characterizing functional brain connectome in vivo with well-established methodology and considerable applications in health and disease. Recently, several studies have demonstrated the feasibility of other neuroimaging modalities in the mapping and characterization of functional brain networks, such as arterial spin labeling (ASL) perfusion MRI, functional near infrared spectroscopy (fNIRS) and positron emission tomography (PET). These methodological advances expand current framework of functional connectome studies and more importantly make a more in-depth and comprehensive understanding of functional network organization possible in both typical and atypical populations. However, there still lacks a systematic evaluation of reproducibility, temporal stability and test-retest reliability for these relatively new methods. Moreover, little is known regarding how brain networks derived from these techniques reorganize in response to diverse pharmacological conditions, different emotional and cognitive states and various brain disorders. All these relevant research topics are vitally important for evaluating these techniques as reliable and meaningful tools to functional brain connectome studies.

The focus of this Research Topic is thus on the most recent developments in analytical methods and models for functional brain networks based on ASL, PET or fNIRS, and their applications in different cognitive and physiological states or neuropsychic diseases. Studies aiming to elucidate cross-modality relationships between brains networks derived from the abovementioned techniques and those from fMRI, DTI and/or T1 are also within the scope of this Research Topic. Researchers, technicians and clinicians engaged in this field are warmly welcomed to contribute an original article, technical and methodological report, or review article to this Research Topic.