Observations upon Conduct of a Thalamic Dog. ∗ Hearing and Vision in Decorticated Animals. †

Abstract

Some time ago one of us observed conditioned visceral responses in rabbits with extensive pallial destruction. 1 Acting upon this evidence and with the knowledge that the cortex was considered the usual if not only locus of the conditioning process by Pavlov 2 on the basis of work by Zeliony 3 we attempted to secure a decorticated animal higher in the evolutionary scale, and here describe the behavior of a decorticated dog with intact thalamus. Almost a hundred animals were utilized in this work which extended over a period of nearly 3 years.

A detailed record of the behavior of the animal was kept beginning with the time of operation (done in 2 stages). The day after operation the animal was able to stand rigidly on its feet when put in that position (extensor hypertonia) but slowly sank to the floor under its own weight without moving. Rigidity of the extremities with clasp-knife reflexes (Creed 4 ) was observed until its death. In 3 days, the animal was able to move with difficulty (which is exactly the time Goltz gives), in 5, it would stand for hours without motion but when in motion moved in a straight line. For 8 days no reaction to pistol shots nor a flash lamp beam was discerned, but on the ninth day a pupillary reflex was present and on the tenth the animal reacted to sound (same day Rothmann's dog registered). It grew to use its muzzle sensibility for purposes of directing its locomotion (Rothmann 5 ) keeping its head low to the floor. The animal reacted to olfactory sensations on the ninth day but never ate or drank spontaneously. On the tenth day circus movements appeared and grew stronger with occasional convulsions and somatic weakening until killed on the 19th day. During its life it showed marked resistance to impressed movements, was unable to respond promptly to stimulation nor could it cease its own activity until this wore off gradually. (Efforts were made to observe sympathetic excitation and phenomena which might be considered sham rage.)