טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAnat Dahan
SubjectFMRI BOLD Response of the Mirror Neuron System to Recognized
and Unrecognized Gestures
DepartmentDepartment of Biomedical Engineering
Supervisors Professor Gur Moshe
Professor Reiner Miriam
Full Thesis textFull thesis text - English Version


Abstract

Gestures are complex visual stimuli involving form (a hand/ head/finger), kinesthetics (movement in a certain rate and angle), semantic meaning (Hi/bye/what..) and social implication. Accordingly, understanding gestures involves several brain regions with different connections and interactions between them.

We created stimuli of gestures with varying levels of recognition difficulty by videotaping gestures composed of point light display. The level of difficulty was controlled by varying the number of point lights lit.

We examined the brain areas active in the process of gesture recognition when there were not enough cues for complete gesture identification and compared them to brain areas active when gestures were recognized.

We examined brain regions that had a specific response to biologically originated points of light, and preferred such stimuli to a stimuli of coherent moving dots or of random moving dots. Identifying areas that respond to biological movement, even when no meaning can be understood is a novel finding that breaks down action understanding to its basic components.

The mirror neuron system (MNS) network has been shown to respond to visual stimuli of actions and gestures. In this research we show different MNS activation patterns for partial cues that do not allow successful identification and for full cues when gesture identification is possible.

Strong activation of the parietal MNS was seen even when there was no successful identification. This activation indicates an involvement of the MNS in the process of gesture identification, rather than it being active as an epi-phenomenon of gesture recognition. The frontal Mirror Neuron system and areas of the prefrontal cortex were active only when there was actual gesture identification. This finding indicates possible different roles of the parietal and frontal MNS. The parietal MNS seems to be involved in identification gesture kinestheics - or in "How" the gesture is conveyed, and the frontal MNS in the gesture as a whole - or "What" the gesture is.

Accordingly, it seems there are two levels of gestures recognition:

The first -  recognition of the kinesthetic elements of the movement, by resonance of premotor cells responsible for similar biological movement.

The second - recognition of the meaning of the gesture such as bye bye / come etc. by frontal premotor cells responsible for recognition and activation of complete actions.