Review article by terry.
"Gain modulation is revealed when one input, the modulatory one, affects the gain or the sensitivity of the neuron to the other input, without modifying its selectivity or receptive field properties."
Neurons in parietal area are gain modulated by eye and head position. This creates a "gain-field". The receptive field selectivity is the same -- based on retinal location, but is modulated based on gaze direction.
"Note that although gain-modulated parietal neurons carry information about stimulus location and gaze angle, the response of a single neuron, no matter how reliable, is not enough to determine these quantities; several neurons need to be combined. This is an example of a population code (Pouget and others 2000)."
Dendrites as mechanism for gain modulation: Mel (1993), Mel (1999). Invertebrates: Gabbiani et al (1999).
Recurrent network for gain: Salinas and Abbot (1996)
Synchrony for gain: Salinas and Sejnowski (2000)
Driving and Balanced inputs: Chance and Abbott (2000)
Zipser and Andersen (1988) were first to show computational power of gain modulation. Showed that after learning a coordinate transform hidden units appeared to respond like gain modulated neurons seen in parietal cortex. Xing and Andersen (2000a, 2000b) furthered work to auditory localization. Used gain model of Salinas and Abbot 1996.
Pouget and Sejnowski (1997b) extended results of Salinas and Abbott (1995) by showing that gain modulated neurons could form a "complete set" and create any nonlinear function from a set of synapses.
Information about location originates in eye-centered representation. gain modulation always seems to mediate the generation of the new coordinate representations.
Gain modulation could be used for invariant object recognition. Neurons in V4 are gain modulated by attention. Gain modulation used for size constancy, and motion processing.
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