Is neuronal encoding of subject-object distance dependent on learning?

Recordings were made in the intermediate and medial part of the hyperstriatum ventrale of behaving domestic chicks which had been imprinted (trained) by being exposed to a training stimulus. Neurons were tested for responsiveness to the training stimulus and to an alternative stimulus at each of three distances (d = 0.5 m, 1 m, 2 m) from the chick. For responses to the training stimulus 24/78 (31%) responsive neurons were d-sensitive, i.e. responses changed with distance. For responses to the alternative stimulus, a similar proportion of neurons was d-sensitive (16/57, 28%). Six d-invariant neurons responded similarly at each distance: four to the training and two to the alternative stimulus. Thus no effect of learning on d-sensitive or d-invariant neuronal responsiveness was found.