- Università di Firenze e INO:CNR, Firenze
Friday, March 14, 2014
14:45 rinfresco; 15:00 inizio seminario
Life consists of reacting to environmental stimuli , based on built-in programmes. Already, paramecium acts its cilia in order to climb up a chemical gradient.
In brainy animals, a collection of algorithms (either innate or built in early age) is stored in the long term memory. In the presence of a sensory stimulus (bottom up ) that engenders a range of interpretive hypotheses, the algorithm intervenes (top-down) as a conditional probability in a Bayes inference, selecting the most plausible hypothesis that fits the sensory data ,whereby an adequate motor reaction is activated .This Bayesian procedure ensures survival. Its recursive implementation is the basis of the active life of the animal. We call perception this interpreted stimulation. In humans, a perception requires a time from hundreds of milliseconds up to 1 sec.
The associated awareness –often called consciousness-can be measured (NRC= neural correlates of consciousness) and some associated parameters are put in correspondence to specific decisions.This is the basis of a recent fashion referred to as neuro-... (neuro-economy, neuro-aesthetics, etc).
Machine learning and expert systems are based on this Bayesian procedure.
In humans, a cognitive revolution occurred. By coding the perceptions in a suitable language, one can compare a piece of a discourse with the previous piece, recalled by the short-term memory (1-3 sec). From this comparison ,the most adequate interpretation emerges. The procedure is based on the inversion of Bayes formula. Indeed, the most adequate interpretation does not require an apriori algorithm, but it is built a-posteriori.
Let us compare two successive verses (1° and 2°) of a poem. Searching the possible meanings of 1°,in order to fit it to 2°, may take long times. For example, if 1° is made of 10 words, each having acquired 100 different meanings in the course of our life, we must explore a table of N=1000 meanings, and the task takes a commensurate time, that we label by N. A quantum search – in which all meanings are entangled rather than being explored sequentially- would require a time N1/2≈30, that is, 30 times shorter.
In fact, an average interval of 3 sec between two successive pieces,characterizes all linguistic endeavours (literary, musical, figurative) as a universal human feature.
The following facts provide the necessary background to justify what said above.
a quantum mechanism,with a constant different from Planck’s, rules the synchronization of trains of electrical spikes of different neurons, thus driving the communication of different brain areas;
due to environmental disturbances, the quantum aspect is lost (decoherence) after 3 sec;
Self-consciousness means that the same judge compares the two pieces 1° and 2°; we hypothesize that self-consciousness blocks the long term memory access and the consequent Bayes formulation, triggering instead the quantum comparison.