“experimental results published last year, from a lab at Lund University in Sweden, hint that we need to change our approach. They suggest the brain learns in a way more analogous to that of a computer: It encodes information into molecules inside neurons and reads out that information for use in computational operations.”
“A computer does not learn by rewiring itself; it learns by encoding facts into sequences of ‘0s’ and ‘1s’ called bit strings, which it stores in addressable registers. Registers are strings of tiny switches. When a switch is set one way, it physically represents ‘1’; when set the other way, it physically represents ‘0’. The registers in a computer’s memory are numbered, and the numbers constitute addresses. The computer stores a bit string by choosing an available address and setting the switches in accord with the string to be stored there.”
“From a computational point of view, directions and distances are just numbers. And numbers, rendered in binary form, are just bit strings. It’s a profound truth of computer science that there is no such thing as information that is not in a deep sense numerical. Claude Shannon’s famous 1948 paper, which founded the field of information theory, used a symphony concert as an example of an information-transmission problem that could be treated numerically. A consequence is that it does not make sense to say that something stores information but cannot store numbers.”
“Brains routinely remember the durations of intervals—a piece of simple numerical information if ever there was one. The Swedish research worked with the giant Purkinje cells in the cerebellum that learned the interval between the onset of stimulation to one of their inputs, and a subsequent brief stimulation of another of their inputs. The results strongly implied that the interval-duration memory was stored inside the Purkinje cell, not in its synaptic inputs. Input arriving at the synapses caused the learned information inside the cell to be read out into a nerve signal that we know controls the timing of a simple learned behavior.”
“Inside neurons are molecules. Many molecules make excellent switches, and storing information in molecular switches is much more energy efficient than doing it in synapses. Learning may involve putting something like bit strings into banks of molecular switches found inside individual neurons—rather than rewiring the neural circuits. That is a profoundly different conception of learning and memory than the one currently entertained.”