Testing this central prediction requires the simultaneous activation of two competing inputs and the simultaneous recording of the rhythm in the group of neurons providing input and

Tyrosine Kinase Inhibitor Library price the rhythm in their target group. To enable a concrete experimental test of CTC, a strong prediction can be derived about the synchronization among local rhythms in monkey areas V1 and V4 during selective attention to one of two simultaneously presented visual stimuli: if two stimuli activate separate sites in V1, and both activate one V4 site equally strongly, then the V4 site should synchronize selectively to the V1 site driven by the attended stimulus. Here, we test this prediction, assessing local rhythms through electrocorticographic (ECoG) local field potential (LFP) recordings. To quantify synchronization between V1 and V4, we used multisite LFP recordings, which have been shown highly effective in assessing long-range, interareal synchronization (Roelfsema Dasatinib manufacturer et al., 1997; von Stein et al., 2000; Tallon-Baudry et al., 2001, 2004). Multisite LFP recordings are routinely carried out with ECoG grid electrodes implanted onto the brains of epilepsy patients for presurgical focus localization. These unique recordings from the human brain have been used for numerous cognitive and/or systems neuroscience studies (Tallon-Baudry

et al., 2001; Canolty et al., 2006), yet they typically do not include early visual areas. We therefore developed a high-density ECoG grid of electrodes (1 mm diameter platinum discs) and implanted it subdurally onto the brains of two macaque monkeys to obtain simultaneous

recordings from 252 electrodes across large parts of the left hemisphere (Rubehn et al., 2009). Figure 1A shows Rolziracetam the brain of monkey P with the electrode positions superimposed (see Figure S1A, which shows electrode positions for both monkeys, available online). Figure 1B illustrates that a contralateral visual stimulus induced strong gamma-band activity (Gray et al., 1989), while an ipsilateral stimulus did not. Figure S1B shows respective time-frequency analyses, demonstrating that stimulus-induced gamma was sustained as long as the stimulus was presented. The gamma band was within the range of frequencies described in previous studies using drifting gratings in human subjects or awake monkeys (Hoogenboom et al., 2006; Fries et al., 2008; Muthukumaraswamy et al., 2009; Swettenham et al., 2009; Vinck et al., 2010; van Pelt et al., 2012). Within that range, the gamma band found here was relatively high, most likely due to the individual predispositions of the animals and the use of moving stimuli (Swettenham et al., 2009) of high contrast (Ray and Maunsell, 2010).