1. Synchrony & Perception
How consciousness can emerge from land of synchronous waves

2. Topics The beginning of the Brain’s story A neuron, atom of perception
Why we need a Brain?
Collective behavior of neurons: oscillation
Synchrony as the communication line
Some thought provoking experiments

3. The beginning of the Brain’s story
All started from golgi an Cajal ~ 100 years ago
The neuron doctrine
A neuron is a sack of ionic medium pierced with ion channels
The imbalance distribution of ions gives the most important property of a neuron to it:
the membrane potential

4. Membrane potential

5. Action potential

6. What’s special about action potential?
It’s the mere way for communication (millisecond scale)

9. Action potential shapes the collective behavior of neurons in a network

10. Why do we need brains? Why neural systems have evolved?
For movement!
For movement?
Daniel Wolpret

11. Structure of the brain may have evolved based on this property
Main parts of the brain

12. Structure of the brain may have evolved based on this property
Cerebral cortex
100,000 Cortical columns,
1000 to 10, 000 neurons each

13. Thalamus
GIF file
Conectomics
importance

14. Thalamocortical network
The thalamus as an integral part of the brain

15. Neural oscillation Two different scales: Single neuron
Neuronal population

16. Single neuron oscillation
Any neuron is an oscillator when it gets the constant input : I

17. Neural population oscillation (synchronization)
There are many ways for synchrony between neurons
Mutual excitation between pyramidal neurons
Inhibitory interneuronal network
Excitatory-inhibitory feedback loop
Synaptic filtering
Slow negative feedback
Electrical coupling
Correlation-induced stochastic synchrony

18. Mutual excitation
Video

19. Neural population oscillation (synchronization)
Through feedback inhibition

20. Neural population oscillation (synchronization)

21. Neural population oscillation (synchronization)

22. Thalamocortical oscillation(resonance or synchrony)
Just keep in mind, we will discuss it

23. What might be the role of these oscillations. Do they “code” any thing
What might be the role of these oscillations? Do they “code” any thing? Information maybe…?
Neural code

24. the neural code? Can the information theory help? Rate coding
Temporal coding
Phase-of-firing code
Population coding
Sparse coding

25. FM coding in thalamocortical network
What does neuron 1 tell neuron 2?
A simpler question: do neuron 1 and neuron 2 interact? (Izhikevich, 1998)
One approach to the neural code is to find the criterion in which neurons can effect each other
In order to find a neural code or a mean for communication, find the criteria that 2 neurons can effect each other.

26. Lets consider the main parts of our brain

27. Assumptions Weak connections
It is based on the observation that average amplitude of post synaptic potential is smaller than 1 mV, which implies that there must be many (a few hundred) presynaptic neurons firing simultaneously to make a given cell fire (McNaughton et al., 1981).
Autonomous oscillations
We assume that each cortical column can exhibit periodic activity that is not induced by a rhythmic input, but is an endogenous (intrinsic) dynamical property of the column.

28. A canonical model and Equations that govern these oscillators
0.004<𝜀<0.008

29. The criteria for interaction
although the model is simple but …..
What the model cannot do?

30. The nonresonant frequencies always make the second term constant
Neuron 1 and 2 interact only when their frequencies are resonant
We say that a vector of frequencies , is resonant if there is a nonzero integer vector such that

31. Coupled oscillators

32. Role of thalamus

33. Examples and simulations
How to test this Idea?
Perturbation test

34. Frequency match in coupled neurons

35. Neural communication in population of neurons

36. The upshot
Synchrony can be the communication method

37. Summary Neurons Oscillation Thalamocortical network
Izhikeviche’s paper

38. Some considerations Oscillation in population level
Synchrony PDF: sleep, cognitive behavior
Thalamus

39. Thalamus in evolution

40. EEG PDF
Miller KJ, Sorensen LB, Ojemann JG, den Nijs M (2009) Power-Law Scaling in the Brain Surface Electric Potential. PLoS Comput Biol 5(12): e doi: /journal.pcbi

41. EEG PDF in cognitive task

42. Synchronization mechanisms
There are many ways for synchrony between neurons
Mutual excitation between pyramidal neurons
Inhibitory interneuronal network
Excitatory-inhibitory feedback loop
Synaptic filtering
Slow negative feedback
Electrical coupling
Correlation-induced stochastic synchrony

43. Types of neurons One can define 2 types of neurons based on their PRC

44. Synchrony through Mutual excitation type 2 neurons(HH)

45. Synchrony through Mutual Inhibition type 1 neurons

46. Frequency bands Mutual excitation: epilepsy
Inhibitory interneuronal network: Gamma band( Hz)
Excitatory-inhibitory feedback loop: Gamma band ( Hz)(when I-I exists, happens less)
2 mechs for Robustness?

47. So what?
Does this assumption explain anything in the real world?

48. We need to know about the NCC
Neural Correlates of Consciousness

49. Experiments

51. Perception obeys the input signal’s frequency

52. Noisy picture & gamma synchrony

53. Noisy dog picture & gamma synchrony

54. Interhemispheric communication through synchrony a causal relationship

55. a causal relationship…

56. Some contradictory results
1: Feature Binding happens through 12 Hz synchrony, not 40 Hz(Monkey’s visual cortex)

57. Cortical neural populations can guide behavior by integrating inputs linearly, independent of synchrony PNAS
Short pulses provided no behavioral advantage, even when they concentrated evoked spikes into an interval a few milliseconds long. Arranging pulses into trains of varying frequency from beta to gamma also produced no behavioral advantage.

58. Nothing for Conclusion but… some Outstanding questions
What is the neural code?
Can synchrony be the basis of our Consciousness?
What is the benefit of processing in a thalamocortical like network?
Is thalamocortical network a SF network?

59. Don’t Respect Textbook Theories
Vincent Walsh, BCNC, 2013

60. Some contradictory results
2: In monkey’s visual cortex, experiment yielded negative results suggesting that synchrony doesn’t bind features of perceived objects

61. Prerequisits:
Cerebrum + thalamus gif
Cat rivalry article
Ted talk daniel

63. Binocular rivalry and synchrony in Cat visual cortex

64. Neural Communication Through Synchrony