3 ms·

Great note Mark. I agree. Action potentials are noisy beasts but much may be hidden in spike time coding that is obscured by averaging. There is an even lower

Great note Mark. I agree. Action potentials are noisy beasts but much may be hidden in spike time coding that is obscured by averaging. There is an even lower level problem that deserves more thought. What timebase do we use to average, or not. There is no handy oscillator or clock embedded in the cortex or thalamus that allows a neuron or module or us to declare “these events are synchronous and in phase”. Our notions of external wall-clock time have been reified and then causally imposed on brain activity. Since most higher order cognitive decisions take more than 20 to 200 milliseconds of wall clock time it is presumptuous to assume any neuron is necessarily working in a single network or module. There could be dozens or hundreds of temporally semi-independent modules spread out over wall clock-time that still manage to produce the right motor output.

RaftPeople 2y ago
> There is no handy oscillator or clock embedded in the cortex or thalamus that allows a neuron or module or us to declare “these events are synchronous and in phase”. Brains waves drive synchronization of groups of neurons, lower frequencies broader, higher frequencies more localized.
- robwwilliams 2y ago
  That is uncertain. They must be a product of underlying processes, but the mechanisms are still opaque. Gamma oscillations only run at about 40 Hz. That is not fast enough to clock neuronal computations or integrations in the 1 to 10 msec range. Oscillations may have role in binding at larger scales. And when we use the word “synchronize” we generally seem to mean “given wall-clock time”. Two neural events separated by 20 msec can be functionally coherent but may neither be in a particular phase relation or concurrent from an observer’s wall-clock perspective. Neuronal activity may not care about the observer’s timebase.

RaftPeople 2y ago

> There is no handy oscillator or clock embedded in the cortex or thalamus that allows a neuron or module or us to declare “these events are synchronous and in phase”. Brains waves drive synchronization of groups of neurons, lower frequencies broader, higher frequencies more localized.

robwwilliams 2y ago
That is uncertain. They must be a product of underlying processes, but the mechanisms are still opaque. Gamma oscillations only run at about 40 Hz. That is not fast enough to clock neuronal computations or integrations in the 1 to 10 msec range. Oscillations may have role in binding at larger scales. And when we use the word “synchronize” we generally seem to mean “given wall-clock time”. Two neural events separated by 20 msec can be functionally coherent but may neither be in a particular phase relation or concurrent from an observer’s wall-clock perspective. Neuronal activity may not care about the observer’s timebase.