The relationship between cyclic changes in thyroid function and behavior of cats with brain stem lesions

Behavioral and thyroid-states were monitored in sixteen cats for 20 months. Six of the cats had stereotaxic lesions of the ventro-lateral parts of the brain stem; these six cats exhibited periodically an abnormal behavioral state that consisted of the tactile elicitability of 'grooming fragments'. The onsets of the abnormal behavioral state occurred at variable intervals after the surgery, appearing mostly in the fall of the year. The other ten cats were controls and never exhibited the abnormal behavioral state. The thyroid-state was monitored during the 20-month period by determining the percentage urinary excretion of an injected dose of 131I. Lesioned cats retained more 131I during their abnormal behavioral state. The 20 months of 131I-retention data were fitted with a Fourier curve, and an analysis of variance was made of the fit. An annual cycle as well as higher frequencies were found for both control and lesioned cats, with the lesioned cats exhibiting more fluctuations than the normals. The main reason for the higher 131I-retention of the lesioned cats during their abnormal behavioral state was the occurrence of the abnormal behavioral state in the fall during the principal maximum of the thyroid-cycle. The difficulties in interpreting data obtained on periodic variables are discussed, and possible mechanisms whereby brain stem lesions bring about changes in thyroid-function are briefly reviewed. The results are compared to some data on periodic catatonia, and the importance of understanding the mechanisms of control and regulation of periodic variables in understanding behavior is noted.