Consistency-based thresholding of the human connectome.
Densely seeded probabilistic tractography yields weighted networks that are nearly fully connected, hence containing many spurious fibers. It is thus necessary to prune spurious connections from probabilistically-derived networks to obtain a more reliable overall estimate of the connectivity. A standard method is to threshold by weight, keeping only the strongest edges. Here, by measuring the consistency of edge weights across subjects, we propose a new thresholding method that aims to reduce the rate of false-positives in group-averaged connectivity matrices. Close inspection of the relationship between consistency, weight, and distance suggests that the most consistent edges are in fact those that are strong for their length, rather than simply strong overall. Hence retaining the most consistent edges preserves more long-distance connections than traditional weight-based thresholding, which penalizes long connections for being weak regardless of anatomy. By comparing our thresholded networks to mouse and macaque tracer data, we also show that consistency-based thresholding exhibits the species-invariant exponential decay of connection weights with distance, while weight-based thresholding does not. We also show that consistency-based thresholding can be used to identify highly consistent and highly inconsistent subnetworks across subjects, enabling more nuanced analyses of group-level connectivity than just the mean connectivity.
Systems Neuroscience Group, QIMR Berghofer Medical Research Institute, Herston, QLD 4006, Australia; Centre for Integrative Brain Function, QIMR Berghofer Medical Research Institute, Herston, QLD 4006, Australia. Electronic address: james.roberts@qimrberghofer.edu.au.
James A
JA
Roberts
Systems Neuroscience Group, QIMR Berghofer Medical Research Institute, Herston, QLD 4006, Australia; Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; School of Psychiatry, University of New South Wales, Sydney, NSW 2052, Australia.
Alistair
A
Perry
School of Psychiatry, University of New South Wales, Sydney, NSW 2052, Australia; Black Dog Institute, Prince of Wales Hospital, Hospital Road, Randwick, NSW 2031, Australia.
Gloria
G
Roberts
School of Psychiatry, University of New South Wales, Sydney, NSW 2052, Australia; Black Dog Institute, Prince of Wales Hospital, Hospital Road, Randwick, NSW 2031, Australia.
Philip B
PB
Mitchell
Systems Neuroscience Group, QIMR Berghofer Medical Research Institute, Herston, QLD 4006, Australia; Centre for Integrative Brain Function, QIMR Berghofer Medical Research Institute, Herston, QLD 4006, Australia; Metro North Mental Health Service, Royal Brisbane and Women's Hospital, Brisbane, QLD, Australia.
Michael
M
Breakspear
D000293:Adolescent; D000328:Adult; D000818:Animals; D063132:Connectome / Q000379:methods*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D009415:Nerve Net / Q000000981:diagnostic imaging*; D009434:Neural Pathways / Q000000981:diagnostic imaging; D066127:White Matter / Q000000981:diagnostic imaging*; D055815:Young Adult