Metacontrast is a visual illusion in which the visibility of a target stimulus is virtually lost when immediately followed by a nonoverlapping mask stimulus. For a colored target, metacontrast is color-selective, with target visibility markedly reduced when the mask and target are the same color, but only slightly reduced when the colors differ. This study investigated neural correlates of color-selective metacontrast for cone-opponent red and green stimuli in the human V1, V2, and V3 using functional magnetic resonance imaging. Neural activity (...) was suppressed when the target was rendered less visible by the same-colored mask, and the suppression was localized in the cortical region retinotopically representing the target, correlating with the perceptual topography of visibility/invisibility rather than the physical topography of the stimulus. Retinotopy-based group analysis found that activity suppression was statistically significant for V2 and V3 and that its localization to the target region was statistically significant for V2. These results suggest that retinotopic color representations in early visual areas, especially in V2, are closely linked to the visibility of color. (shrink)

*Presented at the Western Canadian Philosophical Association Conference 2019 at the University of Lethbridge in Lethbridge, Alberta.* -/- This paper discusses some issues that arise when applying structural realism to biology. I begin by reviewing Katherine Brading’s version of structural realism with a hierarchy with proliferation of models.1 I then attempt to apply Brading’s structural realism to a biological example. This biological example suggests an issue with the use of shared structure. In response, I suggest the use of relevant relations (...) instead of shared structure. I then discuss Steven French’s use of eliminativist ontic structural realism in biology. Additionally, I consider John Dupré and Maureen A. O’Malley’s discussion of metagenomics and claim that biological entities are better described as self-sustaining biological processes.2 These metagenomic insights suggest an eliminativist view is preferable in biology. I conclude with an attempt to combine Brading’s and French’s approaches into an eliminativist relevant relationalism that retains the structuralist flavor and is applicable to the fluid, constantly changing entities found in biology. -/- 1. Katherine Brading, “Structuralist Approaches to Physics: Objects, Models and Modality,” chap. 3 in Scientific Structuralism, ed. Alisa Bokulich and Peter Bokulich, vol. 281, Boston Studies in the Philosophy of Science (Dordrecht: Springer Netherlands, 2011), 43–65, isbn: 9789048195978, doi:10.1007/978-90-481-9597-8_3. 2. John Dupré and Maureen A. O’Malley, “Metagenomics and biological ontology,” Studies in History and Philosophy of Biological and Biomedical Sciences 38 (2007): 84. (shrink)

The causes of prehistoric inter-group violence have been a subject of long-standing debate in archaeology, an- thropology, and other disciplines. Although population pressure has been considered as a major factor, due to the lack of available prehistoric data, few studies have directly examined its effect so far. In the present study, we used data on skeletal remains from the middle Yayoi period of the Japanese archipelago, where archaeologists argued that an increase of inter-group violence in this period could be explained (...) by a population-pressure hy- pothesis. We quantitatively examine the effect of population pressure on the frequency of inter-group violence by compiling an exhaustive data set. We collected demographic information based on burial jars (kamekan) and the frequency of violence based on the ratio of injured individuals. The results are consistent with the hypothesis, i. e., high population density can promote inter-group violence. (shrink)

It has been commonly claimed that prehistoric warfare in Japan began in the Yayoi period. Population increases due to the introduction of agriculture from the Korean Peninsula to Japan resulted in the lack of land for cultivation and resources for the population, eventually triggering competition over land. This hypothesis has been supported by the demographic data inferred from historical changes in Kamekan, a burial system used especially in the Kyushu area in the Yayoi period. The present study aims to examine (...) the previous claim by using an expanded dataset of human skeletal remains and Kamekan. First, in order to quantify the intensity of warfare, we developed a database of injured individuals found in the middle phase of the Yayoi period in two large populations in the northern Kyushu area, the Fukuoka plain and the upperand middle-stream of the Homan River. Second, we collected Kamekan data from site reports published after 1990 and constructed a comprehensive database to infer the demography in these areas. Finally, we compared the frequency of injured individuals and the inferred demography. The results suggest that the frequency of injured individuals and the population increase tended to be higher at the upper- and middle-stream of the Homan River than on the Fukuoka plain. Different assumptions of the lifetime of each type of Kamekan can produce mixed results on the relationship between demography and the frequency of injured individuals. They were positively correlated under the traditional assumption of constant time intervals, while there was no correlation using time intervals based on carbon dating by the National Museum of Japanese History. Thus, our results are partially consistent with the previous claim that the population increase and the lack of land and resources due to the introduction of agriculture were causes of warfare in the northern Kyushu area in the middle phase of the Yayoi period. (shrink)

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)