Firstly, the present study estimated IHTT on the basis of P1 latency, in addition to N1 latency which was used in the aforementioned studies. The advantage of estimating IHTT on the basis of P1 latency is that the P1 represents an earlier stage of visual processing, likely to be closer to the point of initial interhemispheric transfer than the N1 (Saron and Davidson, 1989). The N1 reflects a later stage of visual processing that is sensitive to object categorization, unlike the P1 (e.g., Bentin et al., 1996). Furthermore, a recent study demonstrated that the hemispheric asymmetry of the N1 can reflect the relative rather than the retinotopic position of objects (Wascher et al., 2009). Thus, the P1 may be a better component with which to estimate IHTT than the N1.
