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- P. Adorjan, L. Schwabe,
G. Wenning, and K. Obermayer. Fast Adaptation as a Cortical Coding
Strategy.
.
NeuroReport, 13:337-342, 2002.
(FTP Gzipped PDF, 120 kb)
Adaptation is a prominent feature of biological neuronal systems. A
common interpretation of adaptation in terms of function is that it provides
flexibility for a neuronal system to perform well under varying external
conditions, for example by adjusting the input/output relation of a sensory
system w.r.t. the ensemble of stimuli the organism currently perceives. This
interpretation, however, only applies if the time-scale of adaptation is
slower than the time-scale at which the environment changes. Experimentally
it is observed, however, that adaptation can be very rapid. Spike-frequency
adaptation of cortical neurons, for example, occurs on a time-scale of 100
ms. Here we show that those rapid adaptation processes can also be understood
within the framework of information theory. We start with the hypothesis that
neuronal codes are designed to optimize the information a neuronal
representation conveys about an input stimulus for any increasing time window
beginning with stimulus onset, and we show that this implies a rapid
adaptation of the neuronal code on the time-scale of stimulus presentation.
Adaptation, however, does not occur because the state of the environment
changes. Rather it is a reaction to changes of the organisms own internal
state, e.g. the level of noise in the neuronal representation. We apply this
approach to a model of an orientation hypercolumn in the primary visual
cortex, and predict that inter-columnar interactions should adapt on the
time-scale of a typical fixation period ( 300 ms).
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