, 2001; Banerjee et al., 2011). Experiments examining attentional allocation to contiguous parts of visual space have revealed topographically specific

increases in Selleck AZD9668 the visual cortex ipsilateral to the attended visual hemifield (e.g. Worden et al., 2000; Kelly et al., 2006; Thut et al., 2006). Under the divided spotlight of attention account, it follows that the number of topographic foci of alpha should increase from the undivided to the divided attention condition, as an additional stimulus needs to be ignored. This is exactly what we found in the current study. On the basis of the description of the blinking spotlight model of attention (VanRullen et al., 2007), we derived three possible predictions for suppression of the to-be-ignored stimuli. As the spotlight is thought to constantly move between all possible target stimuli, the first prediction is that all unattended stimuli are suppressed individually. That is, we assume that a similar mechanism exists for both suppression and excitation. For the current experimental paradigm, such a mechanism would result in two peaks of suppression for both the divided attention condition and the undivided attention condition. The second prediction is that there will be no suppression of to-be-ignored stimuli, as the blinking spotlight of

attention can be focused selectively on possible targets. Obviously, this should result in alpha topographies without Transmembrane Transporters modulator peaks over occipito-parietal brain areas. The results of the current study are not in line with either of these possible predictions of the blinking spotlight model. A third prediction refers to the possibility that, while the attentional focus switches rhythmically between all possible target locations, suppression is static, as for the divided spotlight account. Such a prediction fits with the current STK38 results, but would indicate that at least attentional suppression behaves according to the divided attention hypothesis. Taken together, the

current results provide evidence that humans are able to divide spatial attention across two locations for a considerable amount of time, if the task requires them to do so. A very interesting observation can be made for the alpha topographies in the divided attention conditions. For the undivided conditions, where participants try to suppress a whole visual hemifield, we find a large increase in alpha amplitude ipsilateral to the attended hemifield. However, in the divided attention conditions, alpha amplitudes show a large peak over the contralateral visual cortex. For example, in the ‘split right’ conditions, in which the inner left and outer right stimuli are attended to, we find a large alpha peak over the left occipito-parietal cortex. This peak has higher amplitude and a larger extent than the alpha peak over the right visual cortex. A very similar pattern holds for the ‘split left’ condition.