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Presents:
Ayahuasca, Brain and Consciousness
XXVII Reunion of FeSBE, in the XXXVI Brazilian Congress of Neuroscience and Behavior (SBNEC)
Seeing with the eyes shut: mental imagery after ayahuasca ingestion
I'd also like to thank Dr. Tiago Arruda Sanchez
M. Sc. and Ph.D in Medical Physics from Unifesp
And professor in UFRJ's School of Medicine
in Rio De Janeiro
Whose area of expertise is neuroimaging
applied to psychophysiology and psychiatry
Thank you Tiago and welcome
I thank Eduardo for the invitation to come to Fesbe
The research I'll present has been published
last year in the literature
Released by Prof. Dráulio of the Federal University of Rio Grande do Norte
And it's based on the research we've done
on mental imagery after ayahuasca ingestion
Specifically mental imagery with the eyes shut
The title of the article is similar to this one
Why study this? Well precisely due to the alterations in perception
due to ayahuasca, the main one being changes in visual patterns
and mental imagery generated by them
These images are cyclical and fantastical, even similar to ones of lucid dreams
Of a person who also has their eyes closed and has a visual pattern
as a normal physiological experience
And through ayahuasca we can elucidate these mechanisms in the human brain
The images are generated internally, without light coming from the retina
A topic of debate, specially regarding primary cortical areas
Little is known regarding the mechanisms involving the expression of these images with ayahuasca
Our objective was to observe and try to understand through neuroimaging
the underlying neural mechanisms, focusing mainly in areas of the visual cortex
We did a whole brain analysis, to have a global notion of the patterns
And in regards to the visual areas, we looked for relations with other areas associated with these phenomena
of visions and mental imagery
Reviewing how we can establish these patterns with fMRI
The basis is a neurovascular coupling
In which a neural activation leads to vascular changes in hemoglobyn and oxyhemoglobyn concentrations
in the metabolism of associated tissues
And this leads to changes in pixel brightness, which are computationally processed
as a variation of the signal
And the image is nothing more than a signal with many pixels, with many channels as in EEG
We can then study these activations, based of this coupling, and perform an statistical analysis
The final result ultimately is an statistical analysis
that comes from these signals of the neurovascular coupling
And in the case of connectivity, the temporal analysis of these signals allows to infer
the relationship between two active areas in the whole brain map
The protocol involves basically stimulating the subject and processing the raw data
Which will give us the statistical map
from the active cortical region
And in our case ayahuasca accompanies the stimuli;
we were interested as well in cases without the stimuli.
We have thus three experimental conditions:
The first one is seeing a figure with open eyes - and just to point out that subjects were in the scanner
and had two sessions, one before ayahuasca and one 40 minutes after the ingestion of the substance, with
10 subjects and nine minutes left for analysis.
This is the natural image which we used for comparison of the state before and after ayahuasca intake
The instruction was for the eyes to be kept closed, although the experiment was done in a closed, dark room
This was the mental imagery condition, for besides closing their eyes, the instructions were for the subjects
to attempt to imagine the previous presented image,
or to maintain any image that came to their mind, associated or not to the previous image.
And lastly we utilized a random image as baseline, being also a visual stimulus.
Thus we have a temporal sequence in which these events occurred,
first the natural image, second the mental imagery and lastly the baseline, the random image.
The results we observed were in three main regions, frontal, temporal and occipital.
From these observations we started to focus on the whole brain, and not only in a single region.
The variations due to ayahuasca, of mental imagery, in the pre and post condition, minus the effect of the natural image,
gave us a control over the effects of ayhausca in the imagery, our contrast.
This showed us primary visual areas, 17 and others,
which are related to REM sleep and psychopathological cases of hallucinations,
Although it is still a topic of debate in the literature if the primary visual area responds, even in mental imagery.
We also observed activity in temporal areas related to episodic memory and contextual association.
And lastly in the pre-frontal cortex, related to mental imagery and executive cognitive functions, associated
to the imagination of future events and self-awareness, in the Brodmann area 10, mainly.
So here we have the two hemispheres, left and right, in a posterior view of the occipital region
Here a marking in Broadmann 19, in a medial view to allow us to see some temporal structures, such as area 37
And here a view of Broadmann 10, the fronto-polar region
From these images, from this cerebral global analysis,
we extracted these main regions, which confirmed a priori hypotheses of active areas in mental imagery
From these three regions we extracted the signal to evaluate its temporal dynamics
and compare its amplitude in regards to all conditions
A very similar mechanism appeared in which the mental image before the ayahuasca intake is reduced
For in the case of the visual cortex, we expect it not to have a very large amplitude, so its signal is smaller
So here the blue image, before ayahuasca, has a smaller amplitude
and what stands out is the imagery after the ingestion of ayahuasca
And here stressing the activity in the primary visual cortex, the image in red
the mental imagery after the ingestion of ayahuasca, ends up having an amplitude similar to the natural image
Before and after the ayahuasca intake
Thus in seeing with the eyes closed, the visual cortex has an amplitude that shows an activity
similar to the condition in which the person has their eyes open.
The mental image assumes a character of reality, of a real object.
It's also important to point out that besides this increase in the activity of visual areas
Here I'm showing Broadmann 17, primary visual area
Others such as 18, 19 and 7
It's worth noting that this amplification also occurs in other areas
In detail this temporal area, Broadmann 30, associated to episodic memory
And in the case of frontal regions, evoked by imagery
We should expect that imagery even without ayahuasca should increase in relation to the natural image
As the person needs the pre-frontal cortex, their executive functions to evoke mental imagery
So we have three great clusters, occipital, temporal and frontal
And functions that make sense in regards to the evocation of these images
Visual functions for the occipital areas, memory functions, for this content could emerge from episodic memory,
from past events that bring forth these contents that subjects experience in visions
And lastly the control from frontal areas, in order to evoke the images, in the pre-frontal and fronto-polar regions
What we observed with greater attention, doing an analysis of connectivity of all regions,
but what stood out was area 17, the primary visual area, and the frontal area,
in relationship to the temporal areas
How did the relation between occipital, frontal and temporal areas change before and after the ingestion of ayahuasca
Reviewing that the analysis of connectivity reveals the dynamics of the system from the delays
between the signals and the correlations
As well as a statistical analysis to ascribe significance to these correlations,
that give us the idea of connectivity.
In regards to the primary visual cortex, comparing mental imagery before and after ayahuasca,
we observe not only a superposition but a change in the pattern between
the primary visual area and other regions.
With mental imagery it showed a leader pattern, being the origin of the signal to other areas
and in mental imagery after ayahuasca ingestion it becomes a leader in other areas as well
such as area 7 and area 37, which I stress, being related to episodic memory,
and that it's influenced by the primary visual area after ayahuasca intake
Moreover this superposition seems to be a combination between the pattern of relation
in the primary visual cortex with the natural image with the pattern of this visual area in imagery without ayahuasca
This condition, mental imagery without ayahuasca is a superposition of these two states,
natural visual pattern with mental imagery pattern.
to give the experience of mental imagery after ayahuasca
at least in regards to connectivities in the primary visual area
Here appeared the first change of the primary visual cortex to temporal areas
And in the frontal area, Broadmann 10,
showed a leader change, of signal origin
in the connection to other areas, of a leader pattern to a follower pattern
Before it received the signal, it was the leader of area 30
and area 7 and started to receive signals from area 30 and area 7
So in mental imagery, the temporal cortex, in Broadmann's 30,
associated to episodic memory, changed its relation with the frontal cortex
and maybe taking processed information from episodic memory to the frontal area
having a role in mental imagery that might integrate other connections
So there is a change in connectivity, that might reflect this change of pattern in the visual cortex
We thus concluded that besides a visual change there are other transformations associated to the condition
of mental imagery to characterize the phenomena, involving memory, vision and intention
There is also the amplification of signal as we saw in the analysis
that gives reality to objects to become real or more real even with the eyes closed
There is also a discussion of the role of the primary visual cortex on mental imagery,
Which I believed was culturally selected in indigenous cultures
Having a role, and I think that visual function may be related to this social role in xamanic and ritualistic contexts
Sidarta, one of the co-authors of the paper, says that it could be and "indian cinema",
that gives the indian the possibility of seeing very creative things
besides the question of self-knowledge and spiritual cure, very much associated to these cultures
I thank Dráulio, the leader and manager of this research
Q: So I was wondering, all of your images were in black and white?
R: No, that was and old picture of their master
Q: So there were color pictures then
R: There were color pictures
Q: I was curious, what did you do in regards to the "purging" process? Noboby vomited inside the machine?
R: We took a certain care, we we liberal in regards to the quantity; we established a maximum, but the subject didn't have to take the maximum
He could judge how much he needed to produce effects
So the quantity was 200ml but they could take less
We were worried about time, but kept the 40 minutes, instead of waiting for the maximum of activity
We thought of choosing the maximum of visual and sensory response for us to include in our setup
But we decided to keep the 40 minutes as a minimum even if we had to have a certain variabilty in the sample
Some had more effects in the machine than others
There was a person who didn't feel well afterwards
After leaving the machine she wasn't well emotionally for she had more effects and didn't feel at home
She didn't feel comfortable, and she is an extremely experienced person
So it was an effect that we wanted to avoid and in a certain way we did; for she was already going home at that time
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