Patterns of activity in pigeon brain's visual relays as revealed by the [¹⁴C]2-deoxyglucose method

The [¹⁴C]2-deoxyglucose method was used for autoradiographic mapping of functional activity in the pigeon visual system. In awake animals with one eye covered heavy labeling occurred in most of the known areas receiving projections from the exposed eye. In both the retino-tecto-rotundo-ectostriatal pathway and the retino-thalamo-hyperstriatal pathway higher centers were asymmetrically labeled. Labeling was more symmetrical, however, in the hyperstriatum which receives a bilateral projection from the visual dorsolateral thalamus. The activity was higher in the rostral hyperstriatum contralaterally, in the caudal hyperstriatum ipsilaterally to the exposed eye. The density within the labeled area was patchy in the rostral part. Heavy symmetrical labeling was observed in animals with both eyes exposed. In pigeons with both eyes covered some visual centers were still heavily labeled. Centers of the auditory system were labeled too. Plugging of one ear resulted in asymmetrical labeling in auditory projections. The results are largely consistent with what is known about neuronal pathways from the retina and so it seems to be justified to interpret the patterns of labeling in terms of local energy metabolism that reflects functional activity.