Mushy brains, mushy people
As a trained psychologist, I cannot avoid being in love with neuroscience. Long time ago, I used to do research in brain imaging and decoding (i.e., mind reading). Here below is the abstract of the only paper I wrote on this subject. Feel free to skip to the next ^^^ line.
Abstract. Recent evidence of unconscious working memory challenges the notion that only visible stimuli can be actively maintained over time. In the present study, we investigated the neural dynamics underlying the maintenance of variably visible stimuli using magnetoencephalography. Subjects had to detect and mentally maintain the orientation of a masked grating. We show that the stimulus is fully encoded in early brain activity independently of visibility reports. However, the presence and orientation of the target are actively maintained throughout the brief retention period, even when the stimulus is reported as unseen. Source and decoding analyses revealed that perceptual maintenance recruits a hierarchical network spanning the early visual, temporal, parietal, and frontal cortices. Importantly, the representations coded in the late processing stages of this network specifically predicted visibility reports. These unexpected results challenge several theories of consciousness and suggest that invisible information can be briefly maintained within the higher processing stages of visual perception.
Highlights
- The link between working memory and visual awareness has recently been challenged
- We here study the mechanism of unconscious maintenance with MEG & machine learning
- Unseen stimuli can be partially and maintained within high cortical assemblies
- We show how to revise awareness theories to account for the maintenance of unseen stimuli
Since then, one idea stuck with me and still doesn't let go. People, like neurons, are selective filters on their input. Some things activate us (read, "produce observable behaviour"), some don't.
Each of us is activated by different stimuli and the same stimuli produce very different reactions in you and me (e.g., contrary to most, I have very strong opinions about The Departed).
The collective pattern of activation of populations of neurons produces detectably different percepts (a pear or an apple), each closely covarying with events in the physical external world outside our heads.
Our brain does not have access to the pear or the apple, but only to the activity of its neurons. So the only thing it can do is some inverse inference. In Bayesian terms, your brain is constantly trying to update this quantity:
$$p(S|X) \sim p(S)p(X|S)$$
namely the probability of a stimulus S, given the internal sensory activity X.
The infinite beauty of information is that once you know how to manipulate it, you can apply the same trick in any medium, substrate or hardware. In X, substitute the spikes and chemicals with opinions and likes and boom! you have a whole new level of investigation.
Today, people would probably call this Computational Social Science, a field that has even its own conference.
The sustained pattern of activation of our collective behaviour tells us about the representations of our collective cultural world. What are the thoughts of our society? What collective behaviour enables and maintains them? How is information, piped, transferred and transformed by our daily interactions, our century-old institutions, our deeds and our mishaps?
Let psycho-history begins.