1. Task & Stimuli Introduction Conclusions Questions EEG Results
EEG Investigation of Mirror-Neuron Activity Before and After Conscious Perception of Emotion in Faces
Katie T. Singsank & David R. Andresen
University of Puget Sound
Department of Psychology, Neuroscience
Mu-Wave Suppression Aligned to Stimulus Onset
Task & Stimuli
Introduction
Stimulus onset
Mu-wave suppression between 8-13 Hz in the motor cortex has been used an index of Mirror Neuron Activity
Mirror Neurons utilized in action and social understanding, interpretation
No experiments to-date have examined how the MNS functions throughout the process of facial emotion recognition
21 Participants from University of Puget Sound
Faces shown at 100% noise, slowly lifted to 0% over 3 seconds, covered again over an additional 3 seconds back to 100% noise
Participants indicated emotion by pressing either the left (angry), right (sad)
Keypresses occurred between 1-2 s after stimulus presentation
Mu-wave band
Keypress
Mu-wave suppression occurred after stimulus onset, but was not strongly modulated by level of noise in the image.
Conclusions
Questions
Mu-wave suppression is related to conscious perception of face stimuli
Appears to be unrelated to presence of low-level characteristics such as image noise
EEG Results
Does mu-wave suppression vary when recognizing facial emotions?
Mu-Wave Suppression Aligned to Keypress
Does mu-wave suppression vary once one is consciously aware of a face that then disappears?
Future Directions
-2 to -1 s
-1 s to 0 s
0 s to 1 s
1 s to 2 s
Additional emotions could be tested with varying degrees of expressiveness
Faces could be presented to participants starting in the background and brought to the foreground as if approaching or receding from the participant
Experimental Setup
32 channel Biosemi System used on the scalp with reference electrodes placed on left and right mastoids
Acknowledgements
Eye movements monitored using reference electrodes on left temple and orbital
Mu-wave band
W. M. Keck Foundation for Neuroscience Research for funding this research
The University of Puget Sound Enrichment Committee Research Award for funding part of this research
David Andresen for being my faculty mentor
Data processed to remove eye movement and EMG artifacts using principle component analyses in EMSE EEG analysis software. Other artifacts removed using a recursive outlier detection algorithm in EMSE
Response Keypress
References
Keypress (time = 0)
Altschuler, E. L., Vankov, A., Hubbard, E. M., Roberts, E. Ramachandran, V. S., & Pineda, J. A. (2000). Mu wave blocking by observation of movement and its possible use as a tool to study theory of other minds. Society for Neuroscience Abstracts, 26, (Abstr.)
Rizzolatti, G. & Craighero, L. (2004). The Mirror-Neuron System. Annual Review of Neuroscience, 27, doi: /annurev.neuro
Mu-waves were more suppressed as participants became aware of the face appearing out of noise, with maximum suppression around the time they made their response.