the neural code problem

A solution to the neural code could, in principle, give us unlimited power over our brains and hence minds. Science fiction—including mind-control, mind-reading, bionic enhancement and even psychic uploading—could become reality.

The Singularity

Most versions of The Singularity involve bionic brain boosting. Eventually, we will abandon our flesh-and-blood selves entirely and upload our digitized psyches into computers.

A typical adult brain contains about 100 billion nerve cells, or neurons. A single neuron can be linked via axons (output wires) and dendrites (input wires) across synapses (gaps between axons and dendrites) to as many as 100,000 other neurons. Run the numbers and you find that a typical human brain has quadrillions of connections among its neurons.

Synaptic connections constantly form, strengthen, weaken, dissolve. Old neurons die and new ones are born throughout our lives. Cells can also be retrained for different jobs, switching from facial expressions to finger flexing, or from seeing red to hearing squeaks.

Neurons display an astounding variety of forms and functions. Neural growth factors and hormones, also ebb and flow through the brain, modulating cognition in manners subtle and profound. The more the brain is studied, the more questions are raised about how it works. We find that the brain doesn’t always work like it supposed to with cases of schizophrenia, bipolar disorder, depression, Alzheimer’s disease, and many other disorders that resist explanation and treatment.

Singularitarians (Singularity enthusiasts) nonetheless insist that brains are just complicated computers, and there is some basis for this analogy. Neurons resemble transistors, absorbing, processing, and reemitting the electrochemical pulses known as action potentials. With an amplitude of one-tenth of a volt and a duration of one millisecond, action potentials are remarkably uniform, and they do not dissipate even when zipping down axons a meter long. Also called spikes, a reference to their appearance on oscilloscopes, action potentials serve, supposedly, as the brain’s basic units of information.

Assume, as many Singularitarians do, that action potentials are equivalent to operations in a computer. If the brain contains one quadrillion synapses processing on average 10 action potentials per second, then the brain performs 10 quadrillion operations per second or 10 petaflops. Some supercomputers have already surpassed that processing rate. Hence Singularitarians’ belief that computers will soon leave us in their cognitive dust–unless we embrace them through bionic convergence or uploading.

Barring our admittance to cyber-paradise, however, is the neural code. That phrase refers to the software, or algorithms, that transform action potentials and other physiological processes into perceptions, memories, meanings, intentions.

The neural code is science’s deepest, most consequential problem. If researchers crack the code, they might solve such ancient philosophical conundrums as the mind-body problem and the riddle of free will. A solution to the neural code could also, in principle, give us unlimited power over our brains and hence minds. Science fiction—including mind-control, mind-reading, bionic enhancement and even psychic uploading—could become reality.

Neuroscientists still have no idea what the neural code is.

Neural codes seem to vary in different species, and even in different sensory modes within the same species. The code for hearing is not the same as that for smelling. Decoding neural signals from an individual brain will always be extraordinarily difficult because each individual’s brain is unique and ever-changing.

Neuroscientists can’t mimic brains because they lack  a basic understanding of how brains work; they don’t know what to include in a simulation and what to leave out. The neural code is often likened to the machine code that underpins the operating system of a digital computer.

Whether or not this analogy holds up is in question. I feel that since the brain is a living organ, the machine code notion won’t work. Scientists may discover a common neural code that every brain has and uses to build other neural codes used in other areas of the brain.


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