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The Future of Brain Biofeedback and Imaging
Summary of EEG findings
The intent of the EEG
monitoring was to see which characteristics of this individual’s brain activity
are unique. The subject was monitored
continuously, using 19 channels of EEG.
The sensors were attached manually, avoiding the need for a cap. EEG was measured referenced to the left ear,
and also included the right ear as channel 20.
Recordings were then referenced to linked ears for waveform, map, and sLORETA analysis. Recordings
started 15 minutes before the procedure began, and continued for several
minutes afterward, as well. Recordings
were reviewed using three basic methods: (1) visual inspection of raw waveforms,
(2) surface maps using a normative database (John, Prichep, Fridman,
& Eastman, 1998), and (3) sLORETA (Pascual-Marqui,
2002) images using the same normative database.
When using comparison with a
normative database, the individual’s EEG is compared with what is regarded as
typical for any individual of that age.
Therefore, this approach can be used to answer the question, “what is
unusual in this particular EEG at this time?”
By inspecting raw EEG waveforms and maps, it is possible to identify magnitudes
and locations of prominent EEG activity.
When a statistical comparison with a normative sample is used, the
results pinpoint the frequencies and locations in which the observed activity
is notable, that is, it diverges significantly from typical activity. In this way, it is now possible to identify
what is unusual about the recording, because any activity at normal levels is
disregarded due to its having a nonsignificant (at or
near zero) z-score.
The following segment shows
the EEG at the beginning of the procedure.
This reflects the time that the participant is planning the piercing,
and is in a state of rest and composure.
Between sections contaminated with EMG, there is a brief moment of clean
EEG that can be viewed and analyzed.
This segment, which occurs 15 seconds before the piercing begins, is
remarkably normal, considering the impending procedure. In particular, significant amounts of alpha
are present generally. Despite the fact
that the individual’s eyes were open, this looks like an eyes-closed EEG.
When processed using the normative
database producing z-scores, what is most evident is that the amount of
activity in all bands is remarkably normal, with the exception of a relative
excess of alpha and beta in the left frontal region. That is, while the alpha source is clearly
largest posteriorly, the z-scores show that the amount of alpha is at a normal
level in these regions. Where the alpha
exceeds typical levels is in the left frontal areas, being pronounced at F3 and
F7. It is highly asymmetric, and little
alpha is evident on the right side, i.e. at F4 and F8, where it is essentially
absent. This is interesting in light of
the fact that the left frontal area is responsible for assessing safe
situations, and mediating approach behaviour (Davidson & Begley, 2012). There is also an evident hypercoherence
in alpha, reflected in the waveforms in the extreme synchrony of the alpha
waves. In addition, there is some hypocoherence in theta involving the frontal areas.
This activity can be imaged in raw power
using sLORETA, showing the abundance of posterior
alpha.
When the sLORETA
image is rendered using z-scores, it is evident that most of the cortical
activity is at a normal level (for an eyes-closed condition), and that the
excess is frontal:
An even more interesting
picture emerges when inspecting the activity in the gamma (35-50 Hz)
range. This rhythm is associated with
perceptual binding, and is related to phenomena that give rise to conscious
awareness, and has been observed in instances of clairvoyance and advanced
meditation (Collura & Don, 2004; Lutz, Greischar, Rawlings, Ricard,
& Davidson, 2004). Therefore, the
locations and patterns of gamma in this subject would be expected to provide
information relevant to the experience and its mental attributes.
The gamma from the current
sample of EEG is shown in the following graph.
The evident waxing and waning gamma bursts are clear, as well as their
being most prominent in the temporal leads (T3 and T4).
Although the surface maps
show these excesses clearly both as raw and as z-scores, the sLORETA analysis provides significant additional detail. When analyzing the gamma, two significant
patterns emerge. One is that there is a
prominent excess of gamma in the mesial regions of the temporal lobes. This is shown in the figure below
A particularly interesting pattern
emerges, however when the areas of least gamma activity, that is gamma
deficits, are imaged. The initial
evidence for a gamma deficit is seen when the z-scores for gamma are
displayed. In this case, several
“pockets” of hypoactivity are evident as darker
areas:
Seeing these areas of hypoactivity, it becomes of interest to image these areas
specifically, and look for the spatial pattern that they define. This would reveal areas that are
systematically de-activated in concert, suggesting a functional collection of
areas. The method to see them is to
alter the display thresholds so that only these areas are shown. This relatively uncommon technique consists
of selecting only those voxels with z-scores below a certain level. In this case, when only voxels with gamma
z-scores below -1.2 are imaged, a clear pattern emerges defining a possible
functional hub:
The areas of gamma deficit reside in the
occipital and to a lesser extent the parietal lobes (Brodmann
areas 17, 18, and 19), , the motor strip (Brodmann Areas 2, 3, and 4), and the frontal lobes (Brodmann Areas 8 and 9).
This may also be related to Raichle’s Dorsal
Attention Network. Laird’s ICN 2 Network.
Another interesting view of the brain
state is shown when the image is set to show the areas of maximal alpha
activation. Alpha represents a state of
rest and disengagement with active processing.
When the subject’s brain is examined in this way, the following image
emerged:
This image shows a strip of
de-activation that includes parts of the sensory cortex, but which extends
laterally, to include the temporal lobes, and wraps around to the inferior, and
then the mesial, temporal areas. This
suggests that there is a selective de-activation of regions that involve
integration of sensory information with memory, particularly short-term memory
binding. It is therefore possible that
this type of de-activation is involved in the individual shutting down the
interactions between body sensation and the immediate storage of sensory
information. When this information is
viewed in light of, for example, the views of Gerald Edelman (1989), the idea
emerges that the sufi has
shut down the interactions that lead to short-term storage of information, so
that the potentially painful experience does not even enter the possibility of
being perceived, because it does not enter even into short-term memory.
At 340 seconds into the record, the
lances are completely inserted. At this time, alpha is even more evident, along
with delta waves that are focal to the right central
regions. These sites are along the motor
strip, contralateral to the piercing sites.
It is evident that the extreme alpha activity is even more prominent,
indicating a continued state of cortical relaxation. Analysis of this portion showed patterns of
alpha and gamma activity similar to those observed before the piercing.
During this period, the alpha becomes
even more prononunced and is accompanied by
significant beta activity as well. The hypocoherence in theta also becomes much more
significant. Thus, the deviations seen
in the recording preceding the piercing become more pronounced and more
extreme.
As a final example the
following segment occurred after the lances were completely removed. The preponderance of alpha
remains, showing that the individual was capable of maintaining this state
throughout the procedure, including the aftermath.
At this stage, the extreme amounts of
alpha become even more prominent, and the hypercoherence
in alpha becomes even more notable.
Theta activity has become more normal, however.
Overall, the following observations can
be made regarding the unique characteristics of this individual’s EEG:
Before the procedure, his EEG shows a
preponderance of alpha waves, which are maximal posteriorly, but are most
notable for their amplitude in the anterior regions. The alpha is also hypercoherent. There is also a moderate amount of hypocoherence in theta, particularly in the frontal
regions. There is also evidence that
particular regions including Brodman areas 2, 3, 4,
8, 9, 17, 18, and 19 undergo a significant decrease in activation, suggesting
that this functional hub is being de-activated.
During the procedure, these deviations become even more pronounced. After the procedure, the alpha preponderance
becomes diffuse, and is accompanied by a bilateral posterior excess of beta as
well. The findings are consistent with
the interpretation that this individual is able to achieve an extreme state of
relaxation despite this process, and is also able to selectively disengage a broadly
based brain network that may be related to attention.
References
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