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A category of teder interaction is proposed as the main source of (mutual) mild touch stimuli in higher vertebrates. The somatosensory circuits for the perception of these stimuli in mammals and birds are discussed using data from the literature. In addition to the usual somatosensory areas of the brain, in mammals mild touch signals are also conducted to the insula, which is closely connected to the limbic system. This separate processing of mild touch stimuli lends more substance to the category of teder behaviour. The comparable neuroanatomy in birds is more difficult to interpret. There are some intriguing parallels between the relevant circuits of mammals and birds, though in the telencephalic parts in particular, conclusions are limited by uncertainties as to the homologies of the mammalian and avian brains. [ABSTRACT FROM AUTHOR]

The optic tectum in birds receives visual informationfrom the contralateral retina. This information is passed through to otherbrain areas via the deep layers of the optic tectum. In the present studythe crossed tectobulbar pathway is described in detail. This pathway formsthe connection between the optic tectum and the premotor area of craniocervicalmuscles in the contralateral paramedian reticular formation. It originatespredominantly from neurons in the ventromedial part of stratum griseum centraleand to a lesser extent from stratum album centrale. The fibers leave the tectumas a horizontal fiber bundle, and cross the midline through the caudal radixoculomotorius and rostral nucleus oculomotorius. On the contralateral sidefibers turn to ventral and descend caudally in the contralateral paramedianreticular formation to the level of the obex. Labeled terminals are foundin the ipsilateral medial mesencephalic reticular formation lateral to theradix and motor nucleus of the oculomotor nerve, and in the contralateralparamedian reticular formation, along the descending tract. Neurons in themedial mesencephalic reticular formation in turn project to the paramedianreticular formation. Through the crossed tectobulbar pathway visual informationcan influence the activity of craniocervical muscles via reticular premotorneurons. [ABSTRACT FROM AUTHOR]