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Cerebral Spectral Perturbation during Upper Limb Diagonal Movements
DOI: http://dx.doi.org/10.5772/intechopen.88337
In fact, we observed first a decrease of alpha power immediately after the start
of the comeback period and, consequently, an increase in the same frequency band
tied to the end of the movement.
The decreased alpha activity observed immediately after the end of the second
movement could reflect a decrease in internalized attention.
The decrease in alpha is classically related to a decrease of focusing on internal
states and an amplified processing of information from the environment through
sensorial inputs, especially from the visual system [17, 50].
Thus, this alpha decrease supports an increased attentional focus on the environment and a contextual decrease of internalized attention. Probably, after the
forward period, subjects consider the movement ended, and this could represent an
attentional disengagement related to the movement performance.
For those reasons, vertical movements in the comeback period do not require
particular cognitive effort, but, immediately before the next trial, subjects must
re-engage cognitive resources and focus on the internal state causing the significant
increase of alpha observed at the end of the whole trial.
Klimesch [51] suggested that alpha is not a unitary frequency band but it would
be better described as a union of two sub-bands named lower and upper alpha.
These two sub-bands seem to support different functions: lower alpha would be
more modulated by general attentional processes, while upper alpha would be more
sensitive to perceptual and semantic processing during task performance.
Our result suggests that during vertical movement, Alpha1 and Alpha2 were significantly different in Peak2 and approached significance in Peak1. This means that
during vertical movements, in Peak1, Alpha2 is slightly lower than Alpha1 and vice
versa and in Peak2 Alpha2 is higher than Alpha1. Since Alpha2 has been associated
with perceptual processing during task performance [51], we can hypothesize that
the activity pattern observed over alpha power could reflect not a pure movementrelated attentional engagement/disengagement but rather an inhibition/enhancement of environmental sensory input processing.
4.3 Beta
In the beta band, we observed a desynchronization during comeback period only
in vertical movements, around 1300 ms after the start of the trial. The timing and
the shape of the time course follow as observed in Peak1 in the alpha band. Contrary
to our expectations, we did not find a similar desynchronization during diagonal
movements. Probably, higher attentional demand during diagonal movement could
address this issue, but further research will be performed.
Between consecutive trials (from 1900 to 100 ms of the next trial), we can
observe a small increase in beta activity both in diagonal and vertical movements.
This enhanced beta activity represents the post-movement beta rebound [35]. The
presence of this activity suggests that subjects perceive the end of the trial as the
conclusion of the movement, indexing the new trial as a new movement.
4.4 Source localization
A theta generator during the first stage of diagonal movements has been located in
the middle frontal gyrus of the left hemisphere. The location of this generator supports
the aforementioned frontal midline theta hypothesis in which the increase of theta
during diagonal movement could increase internalized attention and integration of
information from different regions such as frontal, sensorimotor, and parietal cortices.
Alpha generators during Peak1 and Peak2 in comeback period were found to
be located in the posterior cingulate cortex and the left inferior parietal lobule,
Cerebral Spectral Perturbation during Upper Limb Diagonal Movements
DOI: http://dx.doi.org/10.5772/intechopen.88337
In fact, we observed first a decrease of alpha power immediately after the start
of the comeback period and, consequently, an increase in the same frequency band
tied to the end of the movement.
The decreased alpha activity observed immediately after the end of the second
movement could reflect a decrease in internalized attention.
The decrease in alpha is classically related to a decrease of focusing on internal
states and an amplified processing of information from the environment through
sensorial inputs, especially from the visual system [17, 50].
Thus, this alpha decrease supports an increased attentional focus on the environment and a contextual decrease of internalized attention. Probably, after the
forward period, subjects consider the movement ended, and this could represent an
attentional disengagement related to the movement performance.
For those reasons, vertical movements in the comeback period do not require
particular cognitive effort, but, immediately before the next trial, subjects must
re-engage cognitive resources and focus on the internal state causing the significant
increase of alpha observed at the end of the whole trial.
Klimesch [51] suggested that alpha is not a unitary frequency band but it would
be better described as a union of two sub-bands named lower and upper alpha.
These two sub-bands seem to support different functions: lower alpha would be
more modulated by general attentional processes, while upper alpha would be more
sensitive to perceptual and semantic processing during task performance.
Our result suggests that during vertical movement, Alpha1 and Alpha2 were significantly different in Peak2 and approached significance in Peak1. This means that
during vertical movements, in Peak1, Alpha2 is slightly lower than Alpha1 and vice
versa and in Peak2 Alpha2 is higher than Alpha1. Since Alpha2 has been associated
with perceptual processing during task performance [51], we can hypothesize that
the activity pattern observed over alpha power could reflect not a pure movementrelated attentional engagement/disengagement but rather an inhibition/enhancement of environmental sensory input processing.
4.3 Beta
In the beta band, we observed a desynchronization during comeback period only
in vertical movements, around 1300 ms after the start of the trial. The timing and
the shape of the time course follow as observed in Peak1 in the alpha band. Contrary
to our expectations, we did not find a similar desynchronization during diagonal
movements. Probably, higher attentional demand during diagonal movement could
address this issue, but further research will be performed.
Between consecutive trials (from 1900 to 100 ms of the next trial), we can
observe a small increase in beta activity both in diagonal and vertical movements.
This enhanced beta activity represents the post-movement beta rebound [35]. The
presence of this activity suggests that subjects perceive the end of the trial as the
conclusion of the movement, indexing the new trial as a new movement.
4.4 Source localization
A theta generator during the first stage of diagonal movements has been located in
the middle frontal gyrus of the left hemisphere. The location of this generator supports
the aforementioned frontal midline theta hypothesis in which the increase of theta
during diagonal movement could increase internalized attention and integration of
information from different regions such as frontal, sensorimotor, and parietal cortices.
Alpha generators during Peak1 and Peak2 in comeback period were found to
be located in the posterior cingulate cortex and the left inferior parietal lobule,