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Critical Brain Networks Why do we need a brain at all? Why the brain should be critical?

Critical Brain Networks Why do we need a brain at all? Why the brain should be critical?. Dante R. Chialvo. Physiology, Northwestern University, Chicago. d-chialvo@northwestern.edu Reprints: www.chialvo.net. Reading. Articles:

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Critical Brain Networks Why do we need a brain at all? Why the brain should be critical?

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  1. Critical Brain Networks • Why do we need a brain at all? • Why the brain should be critical? Dante R. Chialvo Physiology, Northwestern University, Chicago. d-chialvo@northwestern.edu Reprints: www.chialvo.net

  2. Reading • Articles: • Eguiluz V, Chialvo DR, Cecchi G, Baliki M, AV Apkarian. Scale-free brain functional networks. Phys. Rev. Letters 92, 018102 (2005). • Chialvo DR. Critical brain networks. Physica A, 340,4,756-765 (2004). • Beggs J. & Plenz D, Neuronal Avalanches in Neocortical Circuits J. of Neuroscience, 3 23(35):11167 (2003). • Review: • Sporns O, Chialvo DR, Kaiser M, and Hilgetag CC. Organization, Development and Function of Complex Brain Networks. Trends in Cognitive Sciences, 8 (9): 387-433 (2004). • Books : • How Nature Works. (Per Bak) • Things that think. (Chialvo, 2006)

  3. Roadmap “Brainome”Project • Why do we need a brain at all • How to extract brain networks using fMRI (experimental results) • Is anything ever new? (experimental results) • Outlook

  4. Second: What is special about being critical? Recall Ferromagnetic-paramagnetic Phase-Transition T<TC T~TC T>TC Critical Temperature Snapshots of spins states in a model system (Ising) SubCritical Critical SuperCritical Long Range Correlations Only at the Critical state! 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  5. Why the brain should be Critical? • Why do we need a brain at all? • In a sub-critical world everything would be simple and uniform - there would be nothing to learn. • In a supercritical world, everything would be changing all the time - it would be impossible to learn. • The brain is necessary to navigate in a complex, critical world . • A brain not only have to remember, but also to forget and adapt. • In a sub-critical brain memories would be frozen. • In a supercritical brain, patterns change all the time so no long term memory would be possible. • To be highly susceptible, the brain itself has to be in the in-between critical state. 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  6. What one can observe? • Brain dynamics can be described in similar terms as thermodynamic systems at the critical point including: • At large scale1: • Cortical Long range correlations in space and time (scale-free) • At smaller scale2: • “Neuronal avalanches” is the normal homeostatic state of neocortical circuits. ( “cortical-quakes” ). 1Eguiluz V, et al Phys. Rev. Letters (2005); Chialvo DR. Physica A, (2004). 2Beggs J. & Plenz D, J. Neuroscience (2003). 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  7. Can we extract functional brain networks with fMRI? 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  8. fMRI How to extract functional brain networks with fMRI (I) (III) (II) 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  9. Undirected Degree (k) fMRI Indicate “airports” My brain’s network (finger tapping) Nodes spatial location Colors indicate the number of links (or “degree”) of each node. yellow=1, green 2, red=3, blue=4, etc 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  10. fMRI Brain’s degree distribution (i.e., how many links each node have) Scale-free k-gwithg ~2 From Eguiluz et al, Phys. Rev. Letters (2005). 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  11. g =2 fMRI Average Degree Distribution n=22 from 7 subjects Few but very well connected brain sites From Eguiluz et al, Phys. Rev. Letters (2005). 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  12. fMRI Average Links Length Distribution Probability of finding a link between two nodes separated by a distance x < D k(D)~1/x2 “~ Brain radius” Voxel length From Eguiluz et al, Phys. Rev. Letters (2005). 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  13. fMRI Average Links Length Distribution agrees with recent results (in resting condition) PC(D)~1/x2 Functional connectivity vs. anatomical distance. ( Symmetric interhemispheric) From Salvador et al, Cerebral Cortex 2005. 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  14. fMRI Average Links Length Distribution in line with recent proposals Buzsaki et al, TRENDS in Neurosciences, 2004. Petermann and De los Rios, 2005. Hypothetical connection scheme of cortical interneurons and relationship between coverage and number of neurons in each class. 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  15. fMRI Something that bother us: Degree vs Clustering Clustering relatively independent of connectivity Clustering estimates the proportion of nodes forming “triangles”. Assortative From Eguiluz et al, Phys. Rev. Letters (2005). 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  16. fMRI Group statistics Brain networks are small-word and scale-free fMRI-results “Small-world” • C >> Crand • L ~ Lrand Previous related results From Eguiluz et al, Phys. Rev. Letters (2005). 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  17. L ~ 5 predicted LONG AGO by Szentagothai 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  18. fMRI Networks are scale free across tasks! Finger tapping vs. Music • Different tasks • Different networks • Similar scaling From Eguiluz et al, Phys. Rev. Letters (2005). 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  19. Is anything ever new? 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  20. Percival Bailey Gerhardt von Bonin Warren McCulloch Ever new? 1940 McCulloch Chemical Neuronography... Recording cortical activity after local Strychninization Illinois Neuropsychiatric Institute (Chicago). J. Neurophysiology, 1941. J. G. Dusser de Barenne, Garol and McCulloch FUNCTIONAL ORGANIZATION OF SENSORY AND ADJACENT CORTEX OF THE MONKEY. 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  21. Ever new? 1940 McCulloch Chemical Neuronography... Adjacency matrix of cortico-cortical “functional” connectivity, after McCulloch (1940) 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  22. Ever new? 1940 McCulloch Chemical Neuronography... Network analysis of 1940 Chemical Neuronography • Non-homogeneous degree • Similar scaling Chimpanzee’ Degree and Link Length distribution (calculated from McCullock ,1940 data) 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  23. Blah-Blah-logy We have seen: • “In vivo” brain activity lacks a characteristic scale (“scale-free” networks).Theory, consequences… • Assortative features …? theory?. Similar analysis for MEG? • The fMRI method allows, in principle, to study the brain “in a dance” rather than “in a pose” and to address dynamical states as emotion, pain, pleasure, uncooperative patients, coma etc). • Realizing Brodman’s dream: towards the “Brainome” Integrating the cognitive picture by looking at a list of the 100 most relevant behavior as the “phenotype” and to the 100 or so cortical areas a the “genotype”. ( I.E., equating “activated cortical areas” with “gene expression” and “behavior” with “functional genomics”.) 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  24. Brain are critical “Per, the brain for me is critical”… “Yes, for me too Dante!” Brookhaven N. Lab. 1991

  25. Open Parenthesis

  26. 1. Introduction2. Complex Networks3. Catalogue 4. fMRI nets 5. Ever New? 6. Cortical Cultures 7. Conclusion It takes little to listen... Functional Magnetic Resonance Imaging of Female and Males listening the same story (Mean of 6 Brains, each) Male Female # of SD away from mean

  27. 1. Introduction2. Complex Networks3. Catalogue 4. fMRI nets 5. Ever New? 6. Cortical Cultures 7. Conclusion It takes more to talk... “PET Studies of Memory: Novel versus Practiced Free Recall of Word Lists” NeuroImage (1995)Andreasen et al.

  28. 1. Introduction2. Complex Networks3. Catalogue 4. fMRI nets 5. Ever New? 6. Cortical Cultures 7. Conclusion It takes a whole network for other things ... “Areas of brain activation in males and females during viewing of erotic film excerpts” Human Brain Mapping (2002) Karama et al. • Females • (Left and Right ) • Medial prefrontal cortex • Orbitofrontal • Cingulate gyrus • Thalamus • Insula • Ventral striatum • Amygdala • Occipitotemporal cortex • Males: • All of the above plus • Hypothalamus Females Males

  29. “Behavior”(usually bursty, complex, intermittent) Brains are networks producing behavior ... at various scales… Large scale Small scale

  30. 0101 0011 0010 Brains are networks producing behavior ... Current technology already allows, in principle, to get data towards constructing the “Brainome”… it will looks like this: Sneeze 1011001000000000000000000000000 Anger 1011001000000011000000000000000 Walk 1001001010000110011000000000000 Smile 1110001110111010001000000000000 Talk 1011001011100000000000000000000 Angry talk 1011001011100000000110000000000 Listening 1000000000000100001000000100000 . . . . . . . . . . . . . . . . … Brain Node’ State cry Music 100101 Lecture 010111 Children 011011 …… Behaviours

  31. A few conflictive demands ... As a collective the brain have a few conflictive demands: • “Integrated” but “segregated”. (Sporns, Edelman,Tononi1; Pietronero2) • Q: how different is this from being posed at a phase transition? • “Robust” (structurally stable attractors) but “flexible” (today’s good behavior is not tomorrow anymore) • Q: Which structure and dynamics we know of could satisfy that? (Per Bak3 ) • Brain are Complex but obviously Self-organized, Darwin Darwin Darwin... • Q: how is it done? (Per Bak, D. Plenz4, others) • 1) O. Sporns, et al, Cerebral Cortex, (2000); 10(2): 127 2) M. De Lucia et al, Physical Review E 71, 016114 (2005) • 3) Per Bak, How Nature Works, Oxford Univ. Press, 1997 4) Beggs J. & Plenz D. J. of Neuroscience, 3 23(35):11167 (2003). 1. Complex2. Critical3. Networks 4. fMRI nets 5. Ever New? 6. Conclusion

  32. Close Parenthesis

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