Differential emotional experience leads to pruning of dendritic spines in the forebrain of domestic chicks.

Auditory filial imprinting induces quantitative changes of synaptic density in the forebrain area mediorostral neostriatum/hyperstriatum ventrale of the domestic chick. The aim of the present study was to examine the time window and the extent and quality of experience that is required for the induction of these synaptic changes. We found that a brief (30 min) experience with the imprinting situation (tone stimulus + mother surrogate) is sufficient to induce spine elimination, which is detectable on postnatal day 7, but not 80 min after the presentation of the imprinting stimuli. This synaptic reorganization requires the association of the acoustic imprinting tone with an emotional reward (mother surrogate); acoustic stimulation alone does not lead to detectable synaptic changes. The results of the present study provide further evidence that juvenile emotional learning events, such as filial imprinting, lead to a selective synaptic reorganization.