By Scott Grafton, M.D., and Emily Cross, M.S., University of California at Santa Barbara
Summary
The
ubiquity of dance across cultures, ages, and history make it an
“embedded” art form. Most of us already have significant dance
experience by adulthood. This commonality of dance, therefore, shifted
our research away from normative studies that attempt to show that dance
is good for a person or their brain, that it makes one smarter, is
worth learning, or that some types of dance make one smarter than
others.
Instead, our studies concerned the
mechanisms that allow us to learn to dance, and the concurrent
learning-related changes in the brain. Prior behavioral research on
observational learning suggests that physical and observational learning
share many common features. Neuroimaging research on action observation
has identified brain regions, including premotor, inferior parietal,
and temporal regions, that are similarly active when performing actions
and when watching others perform the same actions. The present study
investigated the sensitivity of this “action observation network” (AON)
to learning that is based on observation, compared to physical
rehearsal.
Participants were trained for
five consecutive days on dance sequences that were set to music videos
in a popular video game context. They spent half of daily training
physically rehearsing one set of sequences, and the other half passively
watching a different set of sequences. Participants were scanned with
fMRI (functional magnetic resonance imaging) prior to, and immediately
following, the week of training.
Results
indicate that premotor and parietal components of the AON responded more
to trained, relative to untrained, dance sequences. These results
suggest that activity in these brain regions represents the neural
resonance between observed and embodied actions. Viewing dance sequences
that were only watched (and not danced) also was associated with
significant activity in the brain’s premotor areas, inferior parietal
lobule, and basal ganglia. These imaging data, combined with behavioral
data on a post-scanning dance test, demonstrate the emergence of action
resonance processes in the human brain that are based on purely
observational learning, and identify commonalities in the neural
substrates for physical and observational learning.
A
critical outcome of our research is that learning by observing leads to
action resonance and prediction that is the same as occurs with
physical learning. This strong link between learning by doing and
learning by observing at the neural level might benefit from early
exposure to dance, where the consistencies between training methods
could be acquired.
Introduction
Many
avenues exist for learning dance. For example, learning how to flamenco
dance could be achieved in several different ways. One could learn the
steps by following a verbal description of where, when, and how to move
through space, by following step patterns traced on the floor, by trial
and error, or by observing a dancer who knows the movements and
performing the movements alongside this individual.
Behavioral
research on action learning conducted during the past half-century
suggests that the final option, learning from observing and
simultaneously reproducing another individual’s movements, results in
the quickest and most accurate learning (e.g., (Sheffield, 1961;
Schmidt, 1975; Bandura, 1977, 1986; Blandin et al., 1999; Blandin and
Proteau, 2000; Badets et al., 2006).
This
past research has demonstrated that not only is observation of a model
helpful for learning (Blandin et al., 1999), but also that physical
practice is more beneficial than mere observation of new movements
(Badets et al., 2006). The current research was directed at exploring
the separate and combined contributions that observing and practicing
have on acquiring a novel movement sequence. Additionally, using
functional neuroimaging, we characterized the neural underpinnings of
observational learning, with or without the added benefit of physical
practice.
Early behavioral investigations by
Sheffield (1961) led to the proposal that observation of a model
improved motor learning by means of providing a “perceptual blueprint,”
or a standard of reference for how the task to be learned should be
performed. Carroll and Bandura elaborated upon these ideas by proposing
that this “perceptual blueprint” improves learning by providing a means
for detecting and correcting performance errors as well (Carroll and
Bandura, 1987, 1990). Behavioral studies that compare observational and
physical learning support this idea (Zelaznik and Spring, 1976; Doody et
al., 1985; Carroll and Bandura, 1990; Lee et al., 1990; Blandin and
Proteau, 2000) (for a review, see Hodges, 2007).
In
one such study, Blandin and Proteau (2000) asked participants to
perform a task that involved executing a speeded out-and-back movement
pattern with the right arm while avoiding obstacles. Participants either
physically rehearsed without observing a model perform the action,
observed a novice performing the task before attempting to perform the
task themselves, or observed an expert performing the task before
attempting the task themselves. Observation of either type of model
enabled participants to develop error detection and correction skills as
effectively as physical practice.
Other
work by Blandin and colleagues (1999) establishes that the quality of
the model matters. Beneficial learning comes from observation of an
expert model and not a novice model during the acquisition of a novel
motor task (Blandin, Lhuisset, & Proteau, 1999). Recent data from
psychophysics and EMG (electromyography) data lend additional evidence
in support of observational learning, as reported in a study by Mattar
and Gribble (2005). They demonstrated that participants’ learning
performance of a novel, complex motor task was facilitated after they
observed another individual learning to perform that same task, compared
to watching another individual perform the task without learning, or
learning to perform a different task (Mattar and Gribble, 2005).
What
follows from these and other studies (Barzouka et al., 2007; Bouquet et
al., 2007) is the idea that observational and physical learning have
similar outcomes on behavior, as evidenced by the outcome of training.
However, as Blandin and colleagues note (1999), “this does not mean that
all cognitive processes involved during physical practice are also
taking place during observation or that observation does not engage
participants in some unique processes not taking place during physical
practice” (p. 977).
The work presented above
provides a behavioral foundation for exploring areas of overlap and
divergence between observational and physical learning. However, it is
difficult to determine with only behavioral procedures the degree of
correspondence of cognitive processes subserving these two types of
learning. Behavioral and EMG (electromyography) studies (study of
electrical activity of both muscle and nerve) alone cannot
satisfactorily address the underlying neural mechanisms, whereas the
addition of functional neuroimaging enables us to determine whether
observational and physical learning modify the same, or different,
neural substrates.
Research Design
In
the current research, we investigated this hypothesized overlap of
cognitive mechanisms for observational and physical learning through
concurrent use of behavioral and neuroimaging procedures. If we found
that both types of learning engage the same areas of the brain, then we
can infer that both observational and physical learning engage
comparable cognitive processes. Conversely, the emergence of different
areas of neural activity based on learning would imply that distinct
cognitive processes underlie each of these two types of learning.
We
investigated observational learning by training novice dancers to
perform complex dance movement sequences while manipulating training
elements. Specifically, we determined whether observational and physical
learning resulted in quantitatively similar or different behavioral
performance and patterns of neural activity, and examined how adding an
expert model to the training procedure influenced behavior and neural
activity. Due to the complexity and unfeasibility of having participants
actually perform dance sequences in the scanner (but see Brown et al.,
2006), we instead chose to train participants to perform the movement
sequences with videos outside the scanner, and then asked them to
observe the training videos during the scanning sessions, as shown in
Figure 1.
A
growing body of evidence indicates that action observation during
imaging can be used as a surrogate marker for studying the neural
systems involved in physical skill. Numerous studies have demonstrated
that action observation models can be used to characterize the neural
substrates for action understanding and action learning (e.g., Decety
and Grezes, 1999; Brass et al., 2000; Buccino et al., 2001; Grezes and
Decety, 2001; Rizzolatti and Craighero, 2004). These experiments
identify a distinct set of brain regions that are active both when
observing and when performing actions, referred to as the “mirror neuron
system” or, more broadly, the “action observation network”(AON).
For
the purposes of this research, we use the term “action observation
network” over “mirror neuron system,” since this latter term is more
general and encompasses all of the brain regions involved in action
observation processes, not simply the two main mirror neuron regions
(inferior parietal and premotor cortices). The brain regions that are
generally included in the AON include the supplementary motor area
(SMA), the ventral premotor cortex (PMv), the inferior parietal lobule
(IPL), and posterior superior temporal sulcus/middle temporal gyrus
(pSTS/pMTG) (Stephan et al., 1995; Decety, 1996; Grafton et al., 1996;
Rizzolatti et al., 1996; Binkofski et al., 2000).
In
line with the present experiment, several past studies have
demonstrated the feasibility of using dance learning and observation as a
paradigm for investigating the properties of the AON (Calvo-Merino et
al., 2005; Calvo-Merino et al., 2006; Cross et al., 2006). The first
such study was conducted by Calvo-Merino and colleagues. They
investigated the specificity of the AON to observing one’s own movement
repertory, compared to an unfamiliar and untrained movement repertory
(Calvo-Merino et al., 2005). In this study, expert ballet dancers,
capoeira dancers, and non-dancer control participants passively viewed
ballet and capoeira dance clips while undergoing fMRI scanning.
The
authors reported significantly greater activity within the AON,
including bilateral PMv and IPL activity, right superior parietal lobe,
and left STS, when dancers observed the movement style of which they
were expert. From this, Calvo-Merino and colleagues concluded that the
AON is able to integrate one’s own movement repertoire with observed
actions of others, thus facilitating action understanding.
A
related study from our laboratory investigated the possibility of
creating an action simulation de novo in a group of expert modern
dancers and exploring how this new learning might be reflected within
AON activity (Cross et al., 2006). For this study, we measured patterns
of neural activity within 10 dancers as they learned a complex new
modern dance work over a six-week period. While being scanned, the
dancers observed short clips of the new dance work they were learning,
and of non-rehearsed, kinematically similar control dance sequences.
After each clip concluded, participants rated their ability to perform
each movement sequence. The critical contribution of this study was
that, as the dancers’ expertise with the rehearsed dance sequences
increased, activity within the brain’s PMv and IPL tracked
parametrically with their perceived expertise.
A
second study by Calvo-Merino and colleagues (Calvo-Merino et al., 2006)
examined the influence of visual, compared to motor, experience on AON
activity during action observation. In order to parse visual familiarity
from physical experience, expert men and women ballet dancers observed
videos of movements learned only by their sex, only by the opposite sex,
or moves that are performed by all dancers. The motivation behind this
procedure was to determine whether equally robust action resonance
processes may be elicited by observation of movements that are equally
visually familiar, because men and women dancers train together, but
unequal in terms of physical experience.
The
authors reported that when effects of visual familiarity are controlled
for (i.e., when dancers watched moves from their own movement
repertoire, compared to moves that they frequently saw, but never
physically performed), evidence for action resonance based on pure motor
experience was found in inferior parietal, premotor, and cerebellar
brain cortices. The authors conclude that actual physical experience is a
necessary prerequisite for robust activation in these areas of the AON.
This study provides an excellent point of departure for the present
study, as we also are interested in measuring how purely observational
experience is represented in the AON.
Taken
together, these prior dance studies provide robust evidence for changes
within the AON with the presence (or emergence) of execution competency.
The current study built upon this foundation by addressing open
questions about the sensitivity of this network to real and
observational learning.
To that end, the
objectives of this study were to determine how movement training
influences activity within the AON, and how observational learning (such
as when one simply watches the dance instructor without imitating the
movements) is represented within the AON. By addressing these questions
through the use of both behavioral and neuroimaging measures, we aim to
better characterize the processes that underlie the various ways that
people acquire new movements.
Results
Behavioral Training
Participants’
performance on the rehearsed dance sequences improved across days,
F(2.15, 29.97) = 45.1, p < 0.0001. In terms of behavioral performance
for training with videos that included an expert human model,
participants performed better when a model was present, F(1, 15) =
10.16, p < 0.003.
Behavioral Retest
Results
from the post-scanning dance retest—where participants performed three
songs they had trained on during the week, three that they had passively
watched, three untrained songs, and three entirely novel
songs—demonstrated a main effect of training experience, F(3, 39) = 4.6,
p = 0.008. Pairwise comparisons revealed statistically significant
differences between trained and untrained sequences (p = 0.001) and
between trained and novel sequences (p = 0.002). Because performance was
so similar between the untrained and novel sequences, our discussion
for the post-scan dancing data focus only on differences between stimuli
that were danced, watched, and untrained. Between these stimuli types,
there was a linear trend of experience, with participants performing the
best on sequences they danced, an intermediate level on those they
passively observed, and the poorest on untrained sequences, F(1, 13) =
29.85, p < 0.0001.
Imaging Effects of Dance Training
The
first set of imaging data analyses focused on locating brain regions
within the action observation network that demonstrated a significant
main effect of training during the post-training scan session. In order
to assess the response of the AON to actions that have been rehearsed,
whole-brain analyses were performed comparing the relative BOLD fMRI
imaging responses while participants watched and listened to the set of
videos that they had danced for five days (“danced”), and another set of
videos for which they had received no training (“untrained”).
A
t-test revealed a main effect of training, regardless of cue type, in
several areas of the action observation network, including bilateral
ventral premotor cortex, left inferior parietal lobule, supplementary
motor area/pre-SMA, and mid STS. These results indicate that premotor
and parietal components of the AON responded more to trained, relative
to untrained dance sequences, suggesting that activity in these regions
represents the neural resonance between observed and embodied actions.
Imaging Effects of Observational Learning
A
separate set of imaging analyses focused on locating brain regions
within the action observation network that demonstrated dissociable
responses with respect to training type (whether the sequences were
physically rehearsed, passively observed, or untrained). Viewing dance
sequences that were only watched (and not danced) also was associated
with significant activity in premotor areas, inferior parietal lobule,
and basal ganglia, as shown in Figure 2.
Concluding Comments
Overall,
our results indicate that at the neural level, learning by observing
and physical learning lead to the same action resonance and prediction.
This strong link between learning by doing and by observing suggests
that early exposure to dance might enhance this link, through
consistencies between the training methods.
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