Pretrigeminal cat as an instrument for cerebral investigations.

The pretrigeminal cat is obtained by sectioning the brain stem in front of the trigeminal roots (Batini et al. 1959). During the day of transection the isolated cerebrum of the pretrigeminal cat is continuously awake, and during the following days it remains alternatively in the states of wakefulness and synchronized sleep (Slosarska and Zernicki 197 1). The integrative abilities of the isolated cerebrum are essentially retained. For example, to visual stimuli the ocular and EEG conditioned reflexes (both positive and differentiated) can be easily elaborated (for references see Zernicki 1968). The pretrigeminal cat is obviously a unique instrument for investigations concerning the functions of an awake cerebrum; however, it has been used unsatisfactorily for such purposes. From hte methodical point of view two features of the pretrigeminal cat are of first importance: (i) pain input to the cerebrum is eliminated, and (ii) neural input to the cerebrum is dramatically reduced. 1. Due to the lack of pain the head of the animal can be restrained in a holder. As it is well known this is essential in research on visual perception, in which the precise location of the stimulus in the visual field is usually needed. In this context two lines of investigations will be mentioned. a) The microelectrode study of units at higher levels of the visual system. To satisfy the demand of the head restraining, such investigations have been done mostly on animals under narcosis. In consequence, the data collected so far are relatively simple, and perhaps the hypercomplex cells are those of utmost complexity which can be detected under narcosis. In the experiments on the pretrigeminal cat the visual stimuli can