The extracranial portion of the pineal complex of the frog (frontal organ) is connected to the pineal, the hypothalamus, the brain stem and the retina.

The central connections of the frontal organ of the frog Rana esculenta were studied by means of the cobalt-filling technique using the cobaltic lysine complex. The results showed that the frontal organ has surprisingly more extended connections than those demonstrated after the application of other techniques. In fact, we found that it is connected to the pineal, the hypothalamus, the brain stem and the retina. These connections, which neuroanatomically have not been reported before, suggest that the frontal organ of the frog participates, in some way, in several different functions, such as neuroendocrine activities, motor responses and lateral eyes photoreception interaction.