Numerous studies indicate that gamma oscillations serve as a mechanism for binding features of an object (feature binding)—for example, the shape and color of an object. Early phase-locked gamma is involved in selective attention and is larger in response to attended stimuli than unattended stimuli, particularly over frontal regions (Basar et al. 1999; Yordanova et al. 2001). Several investigators have reported an association between gamma oscillations and P3 components obtained in response to target stimuli in an oddball task (Basar et al. 1999). One recent study found that alcoholics manifest lower gamma power (29–45 Hz) than control subjects during target processing between 0 and 150 ms in a visual oddball paradigm. This effect was strongest frontally and lateralized to the left side. No group differences in gamma were observed for nontarget and novel stimuli. Control subjects manifested significantly higher gamma power in the processing of the target relative to the processing of the nontarget stimulus, whereas alcoholics did not manifest higher gamma power during target processing. Increased evoked gamma is thought to reflect a matching process between the template in
