Audiovisual Mirror Neurons: All About Moving to the Beat

Over the years, I’ve developed an interest in pop culture-based dance-themed movies. I’ve realized the hard way that I can’t dance, so I just choose to vicariously live out my dancer dreams through people—whether or not they’re fictional characters, it doesn’t really matter. I remember that my penchant for such all started with “Bring It On.” Now, it’s reflected in my interest in “So You Think You Can Dance” as well as my excitement to see the UP Pep Squad perform in the much anticipated UAAP Cheerdance Competition.

"Bring It On," the movie that started it all

One of my favorite performances from "So You Think You Can Dance"

What fascinates me most about the performances of a pair or group of dancers is their synchrony—with each other and with the music’s beat and tempo. For such performances, it’s like each dancer is a reflection of the rest—mirroring every movement flawlessly. Dance is motion at its finest. Applying perception principles, it may be that I am able to feel moved by a dance because of mirror neurons. Mirror neurons respond to action. For mirror neurons to fire, actions need not be carried out by the individual himself or herself, they just have to be observed. They function to help an individual understand another person’s actions and react appropriately to them.

It must be considered that in watching a dance, there are two sense modalities involved—vision and hearing. This is most evident in watching a tap dance performance. Each stomp, tap, and click is associated with an observed movement. There’s a specific term applied to mirror neurons that respond to the interaction of auditory and visual signals—audiovisual mirror neurons. In the scientific field of perception, results of psychophysical studies have provided ambiguous results regarding the audiovisual integration involved in mirror neurons. Arrighi, Marini, and Burr (2009) attempted to provide some clarity regarding the process by focusing on the audiovisual integration of mirror neurons for a form of biological motion where both sight and sound provide useful information: tap dancing.

Three subjects were involved in the study. Of the three, two were the authors, Arrighi and Marini. The third subject was a random female participant. All had normal hearing and normal or corrected visual acuity. Experimentation was conducted in two parts: facilitation and summation. All experimental procedures were carried out in a dimly lit, sound attenuated room. For both facilitation and summation, the sensitivity of the subjects for detecting tap dance sequences was measured. Subjects were presented with two three-second sequences, either visual or auditory or both. Subjects were required to identify which of the two sequences contained the tap dance sequence. For visual stimuli, what was used was a light-point tap dance stimuli consisting of six black discs of 1o diameter centered within a monitor screen. For auditory stimuli, the corresponding sound for each associated tap dance motion was used. The aforementioned stimuli were signals in the signal detection experiment. Corresponding visual and auditory noise was also created for each—random dots and arbitrary auditory tap sound sequences (without any predefined beat), respectively.

The facilitation procedure attempted to establish whether auditory information, uninformative in nature, could facilitate visual performance, specifically visual discrimination of tap dancing. Three separate conditions were used to gather results for this. In the first, only visual stimuli was presented, with one of the two three-second intervals containing the tap dance sequence. In the second, the correct auditory tap dance sequence soundtrack was added to both visual stimuli—one with noise alone and the other with the light-point tap dance sequence. This meant that one of the visual stimuli—the one with the light-point tap dance sequence—was synchronized with the soundtrack. This visual stimuli, moved to the beat, so to speak. Researchers rationalized that the auditory sequence was uninformative in nature because it was added to both visual sequences, with the subjects not knowing which of the visual sequences contained the actual light-point tap dance stimuli. In the third condition, the two visual stimuli were presented but with the auditory soundtrack added out of synchrony. For the three subjects, results showed that sensitivity to detecting the light-point tap dance stimuli was greatest when auditory information was present and synchronized with the visual sequence. According to the researchers, this suggests that the perceptual system’s audiovisual mirror neurons use coincident, uninformative auditory information to help disentangle target visual stimulus (the light-point tap dance sequence) from noise.

The second procedure—summation—was designed to investigate integration between auditory and visual signals when both are informative. This portion of the experiment was designed in such a way that for both two three-second sequences presented, the signals for visual and auditory stimuli used were equally detectable. Of the two sequences, one contained only auditory and visual noise. The other sequence contained both the visual and the auditory tap dance sequences. There were two conditions to this summation procedure. In the first, the visual and auditory signals were synchronized. They were presented out of phase for the second. Results showed an increase in sensitivity to detecting the tap dance sequence when the visual and auditory signals were synchronized. According to the researchers’ statistics, based on the Bayesian fusion model, the rate of increase could not be accounted for by the statistical predictions; thus, implying that physiological integration occurred between the synchronized auditory and visual signals.

From the facilitation procedure, it may be inferred that the synchrony of auditory and visual signals reduces temporal uncertainty; hence, facilitating detection of target stimuli. Auditory signals, when in synchrony with the visual stimuli, could serve as temporal references. In signal detection, this narrows the uncertainty of the visual signals and helps individuals ignore noise. The summation experiment strengthens this inference because improvement in detecting the correct tap dance sequence surpassed statistical predictions when stimuli were presented in synchrony with each other.

Upon reading the end of the actual research study, I found myself thinking: “So, what’s the point of all this?” It basically just elaborates on the process of how audiovisual mirror neurons work. It studies a hypothesis that can be extracted out of a simple, logical train of thought. Obviously, in any signal detection experiment, an individual would better detect a signal from noise when there’s another stimulus that could serve as a frame of reference (the synchronized auditory soundtrack to the light-point tap dance figure). But I suppose that in any scientific field, evidence must be provided to establish even ideas of the most logical nature. After all, the study of audiovisual mirror neurons is relatively new; there is much to learn and much to investigate. However, before launching into complicated experiments involving audiovisual mirror neurons’ influence in several aspects of perception, there needs to be a solid scientific understanding and framework of how audiovisual mirror neurons themselves function on the most basic level.  This is the significance of the research of Arrighi, Marini, and Burr (2009).

With regards to improving the study further, I find that the results of the experiment could have been better and less subject to skepticism with the sample size being greater and composed of subjects who are representative of a variety of age groups. With regards to the former, only three subjects were used and two of them were researchers of the study. It may be that others attribute the favorable outcome of the experiment’s results because of the possibly unfair edge researchers had that influenced their respective performances. After all, they have been studying perception for quite some time. It may be that their minds are more sensitive to auditory and visual signals that those who have had less training, exposure, and experience in such a subject. For the latter, measuring the performance of individuals from different age brackets may allow researchers to gain insight as to whether or not audiovisual mirror neurons process information in the same manner across a variety of stages in the human lifespan. Who knows, perhaps the processing power of these neurons may have some age-related component.

Discussing scientific applications of light-point stimuli, tap dancing, and auditory soundtracks has—for some inexplicable reason—led me to develop a hankering to watch “Happy Feet.” Being a Psychology major, I think that actually engaging in this activity has a worthwhile purpose—serving as positive reinforcement for completing this blog entry. And so, I end this blog entry and begin my journey in the land where penguins sing, talk, and dance.

It's "Happy Feet" time for me!

Reference:

Arrighi, R., Marini, F., & Burr, D. (2009). Meaningful auditory information enhances perception of visual biological motion. Journal of Vision, 9(4), 1-7.

Image Sources:

http://www.qwipster.net/bringiton.jpg

http://img.poptower.com/pic-3966/so-you-think-you-can-dance.jpg?d=600

http://www.tamilmask.com/data/images/film/112344.gif

~ by myfivesenseworth on September 15, 2011.

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