From Discover:
If a signal is ‘space-time separable’, this means in effect that one can hold either space or time constant, and then measure the other.
For instance, in an EEG experiment, we typically consider the signal from one particular electrode (i.e. holding space constant) and plot a graph of how it varies over time. In a task-based fMRI experiment, we hold time constant and plot the spatial extent of activity at that time point.
By doing this, we are assuming that activity in the brain takes the form of standing waves.
However, Alexander et al. say that while we can treat brain activity in this way, we shouldn’t, because brain activity is dominated by travelling waves, activations or deactivations which move through the brain, and in which the temporal and spatial dimensions are therefore not distinct.
We question the very notion that neurological entities are events occur at certain locations and times, rather than being comprised of trajectories that extend over locations and times…
More.
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