The sense of body ownership
is the result of various operations in the neuron system. However, scientists
discovered an illusion that can trick the brain to believe a rubber hand belongs
to them while they disembody their own hand. Gatta, Garbarini, Puglisi,
Leonetti, Berti and Borroni (2016) conducted the current study to investigate how
of the rubber hand illusion can have an effect on physiological mechanisms that
related to sense of body ownership on the real hand. After that, they analyzed
the results and provided an in-depth discussion.
In the current study, Gatta
et al. (2016) hypothesized that the disembodiment effect in the rubber hand
illusion can lower the excitability of motor pathways to the real hand. Therefore,
they expected the first dorsal interosseous muscle motor-evoked potentials
amplitude to decrease in the experimental condition, but not in the control
condition. Gatta et al. (2016) recruited 24 participants for the experimental
condition and 20 participants for the control condition after they met certain
requirements for the study. Gatta et al. (2016) used the rubber hand illusion,
an illusion developed by Botvinick and Cohen (1998) that caused the
participants to feel the rubber hand as their real hand and disembodied their
During the rubber hand
illusion, the researchers collected behavioral measurements by asking the
participants to indicate their unseen index finger location (Gatta et al., 2016).
The participants were also asked about their experience of ownership on the
rubber hand. Besides the behavioral measurements, the researchers also collected
the participants’ physiological measurement. Gatta et al. (2016) measured the
excitability of motor pathways by using a single-pulse of transcranial magnetic
stimulation to elicit motor-evoked potentials over the left primary motor cortex.
According to Gatta et al. (2016), the interpreting of the results is consistent
with the hypothesis that the excitability of motor pathways of the real hand
decreased as the participants experienced rubber hand illusion.
Gatta et al. (2016)
acknowledged that the data from the current study does not allow them to find
the correlation between the participants’ subjective illusion experience and
the decrease in motor-evoked potentials, because the behavioral measurement
date and physiology measurement date were collected in different sessions.
However, they also stated that the results are consistent with the previous studies
that as the exposure time to the illusion increased, the motor cortex
excitability decreased (Lewis & Lloyd, 2010). Besides that, the findings
from the current study are consistent with the previous studies about the
illusionary experience that the motor system and body ownership are interactive
such as the absence of prolonged movement could cause the paralyzed arm to be disowned
easier, while the healthy arm appears to be owned stronger (Burin et al., 2015).
The findings from the
current study can have several implications in the medical field and in technologies.
The current study can help other researchers understand more the relationship
of body ownership with patients with paralysis because of cord injury using the
rubber hand illusion (Gatta et al. 2016). From this, they can find effective treatment
or therapy for those patients. On the other hand, the current study can also be
used to learn more about the amputation illusion during the virtual reality procedure
as it is already reported in other studies.
Overall, Gatta et al. (2016) provided
first physiological evidence that the there is a significant decrease in the excitability
of motor pathways of the real hand as the participants experienced the rubber
hand illusion. Although the current study failed to address the correlation between
the participants’ subjective illusionary experience and the motor-evoked
potential, their results are still consistent with previous research.
Therefore, the findings from Gatta et al. (2016) can provide some implications
in the real world, especially in paralysis treatment and virtual reality.