Abstract
In visual selection, stimulus uniqueness (oddity) is a key factor; an object with a feature contrast to the neighbor objects pops out and draws attention automatically. Although a natural scene may contain multiple objects odd in different stimulus dimensions, if we have knowledge about in what dimension the relevant objects are odd, we more easily detect them by attending to that dimension. Here, we investigated how visual responses were modulated by attention to the feature contrast in a particular dimension. In the present experiment, two odd stimuli, each unique in color and shape dimension, were presented with other identical stimuli. Monkeys were trained to search for the target stimulus that was odd in the relevant search dimension, while the search dimension was switched between shape and color dimension. Neuronal recording was made from area V4 and the frontal eye field (FEF). We found that, on average, V4 neurons showed the response enhancement when the relevant odd (target) stimulus fell in the receptive filed. However, the significant response enhancement occurred only when one particular odd stimulus became the target, suggesting that this neural modulation was exerted as the result of an interaction between the types of stimulus oddity and the search dimension. In contrast, FEF neurons showed the significant response enhancement for the target, irrespective of the types of stimulus oddity. [Jpn J Physiol 54 Suppl:S35 (2004)]
