DISCRIMINATION-TRAINING IN A GO NOGO-PROCEDURE ALTERS THE 2-DEOXYGLUCOSE PATTERN IN THE STARLINGS FOREBRAIN/

European starling's (Sturnus vulgaris L.) were used to measure differe nces in the glucose metabolism in the auditory forebrain between birds performing an auditory discrimination task and birds habituated to th e same acoustic stimuli. One group (n = 5) of individuals was trained in an operant GO/NOGG-procedure to report 1-kHz tone signals in a back ground of 4-kHz stimuli. The other group (n=5) was habituated to the e xperimental set-up and to the same sequence of tones presented to the trained birds. [C-14]2-deoxyglucose (2DG) uptake was determined in the caudal auditory telencephalon and the nucleus ovoidalis of well train ed and habituated birds by autoradiography of brain sections. The tiss ue areas having grey values above predefined threshold values of label ling were determined in every brain section of each bird and then comb ined to volumes of labelled tissue. No significant differences of the 2DG uptake in the nucleus ovoidalis were found between the two experim ental groups. In the caudal auditory telencephalon, however, significa nt differences in 2DG-labelling were found. In the trained birds, the labelling in the caudal auditory telencephalon was confined to smaller brain regions than in the habituated birds. These results suggest a d ifferential processing of sounds in the trained and habituated birds w hich is discussed in the context of sharpening of the frequency repres entation by GABAergic inhibition and processes of attention.