Ocular dominance and perceptual asymmetry

Two experiments were performed to determine the relation of sighting and acuity dominance to tachistoscopic recognition. In both, single-letter material was exposed binocularly to either the left or right of fixation at brief durations. In Exp. I ( N = 32) visual field differences in recognition were unrelated to sighting dominance. The results of Exp. II ( N = 24) suggested that both acuity dominance and cerebral dominance affect visual field differences. While all were strongly right-handed (and presumably left cerebral-dominant), right acuity-dominant Ss displayed a large right-field superiority, whereas left acuity-dominant Ss exhibited no visual field difference. These results suggest an interaction between acuity dominance and cerebral dominance which may be mediated by the relative superiority of the crossed optic pathways.

Reactivities of actin as a contractile protein

The molecular basis for the mechanism of contraction in striated muscle, with primary emphasis on the interaction between the thick and thin filaments and the role of the thin (actin) filaments, is the theme presented. Recent information relating to actin-myosin interaction points up the fact that definitive statements cannot be made regarding the molecular interaction(s) that lead to contraction. Nevertheless, the properties of actin indicate that (a) actin in the monomeric state has properties differing markedly from actin in the polymer (filament) state; (b) these property differences may be significant in the contractile process, for they include changes in the reactivity of the bound nucleotide and actin-myosin complex formation; (c) the bound nucleotide seems to be required in the contraction process. For these, and other, reasons discussed, the tentative hypothesis is advanced that the contraction reaction involves local changes in the actin filament providing local monomer or monomer-like actin units in the reaction with myosin.