When dissimilar images are presented to the two eyes, binocular rivalry (BR) occurs, and perception alternates spontaneously between the images. Although neural correlates of the oscillating perception during BR have been found in multiple sites along the visual pathway, the source of BR dynamics is unclear. Psychophysical and modeling studies suggest that both low- and high-level cortical processes underlie BR dynamics. Previous neuroimaging studies have demonstrated the involvement of high-level regions by showing that frontal and parietal cortices responded time locked (...) to spontaneous perceptual alternation in BR. However, a potential contribution of early visual areas to BR dynamics has been overlooked, because these areas also responded to the physical stimulus alternation mimicking BR. In the present study, instead of focusing on activity during perceptual switches, we highlighted brain activity during suppression periods to investigate a potential link between activity in human early visual areas and BR dynamics. We used a strong interocular suppression paradigm called continuous flash suppression to suppress and fluctuate the visibility of a probe stimulus and measured retinotopic responses to the onset of the invisible probe using functional MRI. There were ∼130-fold differences in the median suppression durations across 12 subjects. The individual differences in suppression durations could be predicted by the amplitudes of the retinotopic activity in extrastriate visual areas (V3 and V4v) evoked by the invisible probe. Weaker responses were associated with longer suppression durations. These results demonstrate that retinotopic representations in early visual areas play a role in the dynamics of perceptual alternations during BR. (shrink)

(First paragraphs.) — The notion of “mental time” refers to the experience and awareness of time, including that of past, present, and future, and that of the passing of time. This experience and awareness of time raises a number of puzzling questions. How do we experience time? What exactly do we experience when we experience time? Do we actually experience time? Or do we infer time from something in, or some aspect of our experience? And so forth. These and many (...) related questions in the “philosophy of mental time”, the topic of this special issue of the Annals of the Japan Association for Philosophy of Science, are not purely philosophical questions. Or at least, they are not likely to be satisfactorily answered by philosophers alone. Rather, they also need the input of neuroscientists, psychologists, physicists, linguists, and others. And conversely, answers to these questions may have implications outside the scope of philosophy. The papers in this special issue illustrate this inherent multi- or interdisciplinarity of the philosophy and science of mental time. In this theme introduction, we want to give a few more examples to illustrate this interdisciplinarity, but also to point out that much of the field is still wide open—that is, these illustrations raise more questions than answers. (shrink)

There are some objects of perception that are either too far from us to touch or that cannot be touched at all. Typical examples are the sky and the various phenomena that appear in the sky such as rainbows and sunsets. This paper is concerned with the ontological status of the rainbow. Does it exist when it is not actually perceived? Does it exist even when it is not possibly perceived? My conclusion is that a rainbow is a physical event, (...) and that, although it is recognized as a rainbow by its characteristic visual appearance, it should not be identified with that appearance. I suggest that the case of the rainbow might give us useful hints for the analysis of secondary qualities like colors and sounds. (shrink)

There is a widely shared account of the distinction between types and tokens, which might be termed the standard account. However, it has some surprising consequences that are not always realized. According to the standard account, a type is a contingent abstract object that can be created by us, but it does not allow any change and can never be destroyed once it is created, because it is an abstract object. I would like to present an alternative account of types (...) and tokens, according to which types are concrete objects that are located in space and time. This new account is based on a concept that I call a "token generator", which is something that specifies in detail how to produce the tokens. (shrink)