The End Point of the Sylvian Fissure is Higher on the Right than the Left in Cat Brain as in Human Brain

Abstract

The height of the end point of the sylvian fissure (SF) was analyzed in the right and left brains of male and female adult cats. A corrected SF asymmetry coefficient (AC) was computed for each brain. An AC larger than zero (AC+) showed a rightward asymmetry, and an AC smaller than zero (AC-) a leftward asymmetry. In the total sample, ACs fit a normal distribution with a mean significantly larger than zero. Of these brains, 75% had ACs larger than zero median; 23.4% had ACs smaller than zero median. Of 11 right-pawed cats, 90.9% had ACs larger than zero. Of 13 left-pawed male cats, there was no significant difference between AC+ and AC- brains. In right-pawed female cats, the right SF was also higher in most animals, but the difference did not reach the 5% significance level. In left-pawed female cats, the number of AC+ brains significantly exceeded that of AC-brains. Thus, the brains of the left-pawed male cats resembled those of the right-pawed female cats; right-pawed male cats resembled left-pawed female cats with regard to asymmetries in SF height. It was concluded that the human brain is not unique in SF asymmetries, which may be linked to manual asymmetry and sex hormones.