1. The phi complex: a dual-EEG study of social coordination
Human Brain and Behavior Laboratory
Center for Complex Systems & Brain Sciences
Florida Atlantic University
The phi complex: a dual-EEG study of social coordination
E. Tognoli, G.C. De Guzman, J. Lagarde, J.A.S. Kelso

2. A neurobehavioral view on social coordination
A very important discovery for the recently growing field of Social Neuroscience is that of mirror neurons in Here we see one monkey manipulating a piece of food. The other monkey is watching. In cortical areas having motor function, everything happens as if the observer-monkey was handling the food himself, except that the limbs do not actuate the movements.
This mirror neuron system has been found in human, implicated in higher social functions such as action understanding and intention understanding.
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When we behave in a social setting, our motor preparation system is connected to our motor system. Our mirror neuron system is also connected to our motor system. An important question is “what happens in situation during which both are trying to affect the motor system simultaneously”.

4. Our approach: Coordination Dynamics (Kelso, 1995)
Social neurosciences: ways to measure how A’s behavior affects B’s brain and behavior
Our approach: Coordination Dynamics (Kelso, 1995)
A theoretical framework for understanding informationally coupled self-organizing systems
Social behavior: emergent property of a group of people.
Assessment of individuals one at a time
Focus on the outcome of the interaction → no dynamics
Temporal evolution is information-rich (mechanisms)
There are 2 important properties of social behavior:
It is the emergent property of a group of people
a lot of information about mechanisms is hidden in its dynamics
However, classically social Neuroscience only consider one single subject (paradigms of action observation; delayed imitation).
The dynamics is typically collapsed and only the outcome of the behavior is considered.
To take into account the nature of social behavior, we designed a paradigm in which it is possible to measure CONTINUOUSLY how the subjects’ behaviors change owing to the social interaction.
This approaches derives from CD…
Measure how social interaction continuously affects the ongoing flow of behavior produced by each individual

6. Brain? identification of neuromarkers in the spectral domain
How is coupling manipulated? Visual information exchange
What real time behavior is studied? Spontaneously uncoordinated and coordinated rhythmic finger movements
Dual-EEG recording
Very briefly for the methods, we recorded the dual-EEG of subjects during the performance of rhythmic finger flexion-extensions. Trials were divided in 3 periods before vision, during vision and after vision.
No vision
Vision
No vision
Brain? identification of neuromarkers in the spectral domain

7. We analyzed the EEG spectrum in the 10 Hz range using an adaptive segmentation method.
Frequency (Hz)

8. Effect of social interaction, effect of social coordination
Comparison of EEG spectra before and during vision: SOCIAL INTERACTION
Comparison of EEG spectra in coordinated and uncoordinated trials: SOCIAL COORDINATION
We analyzed changes in the EEG during vision, and more importantly, differences between synchronized and unsynchronized trials. Here you see the relative phase, before during and after vision. When it becomes horizontal, it means that the movements are phase locked. When it is warping, it suggests that the movements are independent.

9. Comparing before and during vision, we observed a desynchronization of mu and alpha rhythms. Very briefly, mu is related to sensorimotor awareness and alpha to visual attention. But those were not different depending on the coordination.
-20.1%
-30.44%

10. Phi2, coordinated trials: +9.6% Social behavior
We also identified a new rhythm above right centroparietal cortex we called phi. A closer look showed it was made of 2 components, phi1 and phi2. Phi 1 was specifically enhanced during unsynchronized trials and phi2 was specifically enhanced during synchronized trials.
Phi1, uncoordinated trials: +12.1%
Intrinsic behavior

12. Coordination Behavior
Intrinsic Behavior
Coordination Behavior
Dorsal
visual
pathway
Dorsal
visual
pathway a↓ a↓ m↓
Somato-
Sensory
(reafference) m↓
Somato-
Sensory
(endogenous activity
from observed action)
Intrinsic
motor
preparation
Mirror neuron
activity
On the left is a description of the mechanisms engaged when subjects retain their intrinsic behaviors (‘social neglect’) and do not synchronize with the other. That is, the behavior of the other has no impact on one's ongoing behavior which is realized using the following functional loop: the subject moves his/her finger thereby eliciting somatosensory reafference, which feeds to areas of intrinsic motor preparation then on to the executive motor cortex (M1). This loop supports and sustains a person’s “intrinsic dynamics”.
On the right is a description of the mechanisms engaged when people coordinate with each other. The informational coupling in the task is based on vision of the other’s hand movements. When a subject perceives the other's movement, the dorsal visual pathway distributes information to the mirror neuron system both directly and indirectly through the somatosensory cortex (the latter is known to be activated by a range of real and endogenously generated input including action imagination and action observation). The mirror neuron system is functionally connected to the executive motor cortex. As a result of this 'social loop', a person’s intrinsic behavior shifts toward the other's behavior and coordination is achieved.
From the electroencephalographic point of view, mu and alpha are depressed both during intrinsic and coordinated behavior. Phi however, is differentially recruited, its first component facilitating the connectivity between the intrinsic motor preparation system and the motor cortex whereas phi 2 facilitates the connectivity between the mirror neuron system and the motor cortex.
f2↑
f1↑ M1 M1
Behaviors
Behaviors

14. Positive effect of social interactions
Cognitive integrity
(eg. Bassuk et al., 1999;
Holtzman et al., 2004;
Glei et al., 2005;
Béland et al., 2005)
Neuroprotection
(Rose, 1985;
Saczynski et al., 2006;
Bennett et al., 2006)
Social behavior is implicated into several benefits for the elderly individual: it is correlated with the prevention of cognitive decline, of diseases in general and of structural alterations of neural tissue, in possible relation with the concept of cognitive reserve. The paths and directions of those correlations are poorly understood or controversial. Today, we are presenting an experimental paradigm we developed to measure social behavior and the results of a dual-EEG experiment conducted in a sample of young adult. We will conclude with some questions regarding the profile of elderly individuals with respect to our model of social behavior and is EEG neuromarkers.
Health
(Seeman, 1996;
Seeman & Crimmins, 2001)

15. Loss of social coordination competencies in elderly ?
Future directions
Loss of social coordination competencies in elderly ?
Increase allocation of resources to intrinsic motor function
Decrease informational coupling mediated by sensory loss
What about the mirror neuron system? m a
A question arising now is “What are the competences of elderly subjects in social coordination? Is there a loss of social competencies? Is it due to an increased allocation of resources to intrinsic motor function (which could be seen as increase mu ERD); a decreased informational coupling mediated by sensory loss (alpha). What about the mirror neuron system? Is it affecting by the processus of ageing, (phi). f1 f2