Recruitment of ineffective synapses after injury.

This paper describes three ways in which cells may expand their receptive fields with no concurrent change of morphology. (a) The subliminal fringe. Classical physiology described the presence of excitatory inputs that were not sufficiently strong to raise the cells above its firing threshold unless there was a decrease of inhibition or a summation of excitatory inputs. (b) Receptive-field expansion triggered by the arrival of impulses but sustained by central mechanisms. (c) Receptive-field expansion following a change in the transport of substances into the region of synapses.