Asymmetrical Relationships Between the Right and Left Heights of the Sylvian End Points in Right- and Left-Pawed Male and Female Cats: Similarities with Planum Temporale Asymmetries in Human Brain

Asymmetry in the height of the right (R) and left (L) Sylvian end points was studied in right- (RH) and left-pawed (LH) male and female cats. Sylvian height was described relatively to brain weight. An asymmetry coefficient (AC) was estimated (R - L/.5*R + L). There was no significant relationship between R + L Sylvian height and AC, in the total sample and in AC- (leftward asymmetry) brains. In AC+ brains (rightward asymmetry), R + L Sylvian height showed an inverse correlation with AC in RH cats, and a direct correlation in LH cats. There was an inverse correlation between left Sylvian height and AC in RH cats, but no correlation in LH cats. There was a direct correlation between right and left Sylvian height and AC. In AC- brains, left Sylvian height had no relation to AC, but there was a direct correlation between right Sylvian height and AC. In AC+ brains, left Sylvian height showed an inverse correlation with AC in RH males and females; a direct correlation only in LH male cats. Right Sylvian height showed a direct relation to AC+ values in RH and LH males and LH females (no correlation in RH females). The results supported the generalization that a brain symmetrical in a given region has more combined cortex than a brain that is asymmetrical for this region, only for RH cats, however (Galaburda et al., 1987).