In a Wada test a single hemisphere is sedated with sodium amobarbital. While the sedated hemisphere is unresponsive, a cognitive examination is conducted on the other hemisphere. This test is done to determine whether performing an ablative surgery on a given hemisphere is a viable treatment for epileptic seizures. By using the Wada test, one can avoid creating irreversible damage in areas of the brain crucial for modern day life, such as language production regions.
The Generalized Wada Test
The thought of targeting an isolated brain region for drug therapy is very stimulating. But do we have to sedate it? Sodium amobarbital may have useful properties that makes it a good fit for the Wada test. But it is unlikely to be the only substance that can be used. More broadly, there seem to be a variety of compounds that can be used for intracarotid drug delivery.
In all likelihood there must be a number of psychedelic compounds that could selectively affect brain regions via intracarotid delivery. One thought is to inject 2C-B (or whichever psychedelic has the desired pharmacological properties) on one hemisphere so that a person can compare the two sides of her visual field. This way, she would be able to compare side-by-side the features and patterns highlighted by the algorithms of her visual system (which would, presumably, be different on each side). In turn, this will enable us to catalogue more precisely the specific differences in visual experience under the influence of several drugs.
Even more generally, one could also make use of additional brain interventions such as tDCS, ultrasound, optogenetcs, etc. For example, imagine using ketamine and tDCS on the right hemisphere while the left receives ultrasound stimulation. We have a combinatorial explosion. A good one. I call this the Generalized Wada Test (WGT).
Philosophical Applications of the Generalized Wada Test
This technique presents a striking possibility: approaching philosophical problems empirically. More specifically, this technique might be used to:
- Test the properties of phenomenal binding, and
- Allow “incommensurable” experiences to “experience each other” as the halves of a unitary consciousness
Phenomenal binding can be put under a microscope by using a GWT to infer the necessary chemical properties that brain regions require in order to enable the integration of phenomenal features into unitary experiential wholes. The speed at which binding takes place between the hemispheres could also be quantified. If phenomenal binding is not possible between two given states of consciousness, that would also be very valuable information for consciousness research.
With regards to the second possibility…
Is there a Total Order of Subjective Preferences?
Take two states of consciousness A and B. Suppose we use a GWT to make A manifest in the left hemisphere, while B does so in the right. The subject as a whole is asked to decide which of the two states of consciousness is subjectively preferable. If A is preferred over B, then a directed edge from B to A is added to the graph (with a weight proportional to the certainty/degree of preference). By adding the corresponding weighted edge between every pair of states of consciousness inducible on a GWT we would map a large portion of the state-space of consciousness available to humans. Let’s call this graph the directed network of subjective preferences.
Now, once we have fully populated such graph… would it actually be a directed acyclic graph (DAG)? Could we extract a Total Order? In other words, does the directed network of subjective preferences reveal a proper order of experiences from least to most preferred?
Can we make a universal scale of subjective preferability? Is it possible to infer a scale that, as David Pearce would call it, shows us the utility function of the universe?
But what if we find cycles?
Hedonic Tone
Even though there is a very close relationship between bliss and activity in the outer shell of the nucleus accumbens (and various other nearby hedonic hot-spots), it is not yet clear whether all pleasurable, blissful or otherwise subjectively valuable states are triggered by the activation of this area. We know that classic psychedelics, for example, do not have pharmacological dopaminergic or opiodergic action, and thus don’t activate the nucleus accumbens directly. And yet, people do report ecstatic and blissful states of consciousness on LSD…
It is not yet clear whether that bliss is mediated by hedonic hot-spot activity (thankfully, we may soon find out). If psychedelic bliss is fundamentally dissociated from dopaminergic and opiodergic activity, what would that say about the nature of pleasure? Could there be higher levels of bliss that are unrelated to current neurobiological models of subjective reward? What if everyone on acid bliss says that acid bliss is better than heroine bliss, while everyone on heroine bliss says the opposite? What do we make of Dostoevsky’s epileptic bliss?
For several instants I experience a happiness that is impossible in an ordinary state, and of which other people have no conception. I feel full harmony in myself and in the whole world, and the feeling is so strong and sweet that for a few seconds of such bliss one could give up ten years of life, perhaps all of life.
I felt that heaven descended to earth and swallowed me. I really attained god and was imbued with him. All of you healthy people don’t even suspect what happiness is, that happiness that we epileptics experience for a second before an attack.
Nothing short of a Generalized Wada Test would be able to approach these questions.
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