For three decades, Michael Shadlen has been working on a task that seems to have nothing to do with consciousness. A monkey looks at a screen with randomly flickering dots; some of them drift in one direction, and it must decide which one. It is deadly boring. But in the parietal cortex, in the LIP area, neurons were discovered whose firing rate climbs steadily as evidence for one of the options accumulates. Once it reaches a threshold, the animal responds. Roitman and Shadlen described this in 2002, and since then, the accumulation curve has become the workhorse of the entire field. NYU
At the end of May, Shadlen published a text in PNAS where a theory of consciousness is derived from this curve.
It is worth mentioning the genre right away, because it explains a lot here. This is a Perspective, specifically an Inaugural Article—a programmatic piece that those elected to the National Academy of Sciences are entitled to write; Shadlen was elected in 2023. The manuscript arrived at the editorial office in January and was accepted in April; among the reviewers were Michael Graziano and William Newsome. That is, people with their own, quite different views on the subject. The format allows the author to speak more broadly than the data permits, and Shadlen exercises this right. The TransmitterThe Transmitter
The line of reasoning is as follows. Almost everything the brain does is a question posed to the world. It is not passive registration, but interrogation: what is there, is it worth moving, this way or that? Shadlen calls the answers to these questions provisional intentions. These are no longer raw signals, but commitments that incline one toward action, yet they do not enter consciousness. arxiv
Next comes the most interesting part—and the place where it is easy to misrepresent Shadlen. He does not claim that it is absolutely dark inside before a report. On the contrary: some unconscious states, according to him, already carry enough information about the source of knowledge to possess a minimal "felt" character. The light is not turned off there; it is dimmed. A thought becomes conscious when it is restructured into a form suitable for general reference and potential reporting—to another person or to oneself; and this is where the theory of mind and narrative structure come into play. The Transmitterarxiv
An analogy that seems to work: a letter written to oneself. It already exists in the head, with intention and context, but it is raw and private. Once you decide that the letter will go to someone else, the text is restructured. Clarifications, caveats, and considerations for someone else's lack of understanding appear. It is not new content, but a different packaging of the same thing. According to Shadlen, this restructuring is precisely the transition into consciousness.
Hence the clash with competing theories. The Global Workspace Theory bets on "ignition" and broadcasting—the signal flares up and spreads across the cortex, and this is considered the entry into consciousness. In Shadlen's view, nothing is broadcast anywhere; the same decision-making circuit simply begins to be used differently. Higher-order theories fare worse: a meta-representation is needed here, but a narrow one—not "thought about thought" in general, but an accounting for the fact that the interlocutor does not know your context.
The weak point is visible to the naked eye, and the author does not hide it. All three decades of empirical work involve macaques, dots on a screen, and electrodes in the LIP. In none of these experiments does the animal report anything. The closest to what is needed was work with humans, where subjects were asked to note on a clock the moment they felt they had made a decision; the subjective time predicted the accuracy of the choice—Shadlen called this "puncturing consciousness" at the time. It is beautiful, but it is still not a demonstration of the transition itself. An experiment is needed that catches the moment when the brain labels the source of knowledge and makes it suitable for transmission. Such an experiment does not yet exist. Braininspirednih
And there is a question for which the theory has no good answer. If consciousness is a byproduct of social communication, then what happens in creatures that do not talk to anyone? An octopus? A crow solving a problem alone?
Shadlen clearly does not want to concede that there is a void inside them—hence the caveat about the minimal felt character of unconscious states. But then the boundary between "a little bit there" and "already conscious" lies where the theory draws it, not where it can be measured. Which, to be honest, is exactly the problem that has caused the study of consciousness to stall for the last thirty years.
