Many neurons in V1 respond selectively to visual stimuli with specific orientations, spatial frequencies, and directions of motion (R. L. De Valois & De Valois,
1988; Hubel & Wiesel,
1962), but whether the above multiple-color channels also exhibit selectivity to these spatiotemporal properties as well as to chromatic hues remains to be investigated. Psychophysical studies have revealed orientation and spatial frequency selectivity of chromatic channels using isoluminant red-green stimuli (Bradley, Switkes, & De Valois,
1988; K. K. De Valois & Switkes,
1983; Losada & Mullen,
1994; Medina & Mullen,
2009). Single-cell recordings have also shown that some color-sensitive neurons in V1 are selective for orientation and spatial frequency (Johnson, Hawken, & Shapley,
2001,
2008) but that other neurons in cytochrome oxidase (CO) blob regions are not (Livingstone & Hubel,
1984; H. D. Lu & Roe,
2008; Yoshioka & Dow,
1996). However, these studies have only examined chromatic stimuli modulated along a particular hue angle as defined by red-green stimuli, and it remains unclear if the same holds true for stimuli modulated along the other intermediate hue angles to which multiple-color channels are specifically sensitive. Indeed, previous psychophysical analyses based on adaptation and masking (Hansen & Gegenfurtner,
2006,
2013; Webster & Mollon,
1991) have examined selectivity to intermediate hues; these studies involved stimuli such as disks (Webster & Mollon,
1991) and block noise (Hansen & Gegenfurtner,
2006,
2013) that, owing to their broadband energy profiles, make it difficult to reveal the joint space–time selectivity of multiple-color channels. Hansen and Gegenfurtner (
2006,
2013) showed hue-selective masking for the detection of a rectangular texture region using an orientation discrimination task (vertical vs. horizontal), but the fact that observers can discriminate a particular attribute does not always demonstrate the existence of channels selectively sensitive for that attribute.