This has led researchers to classify the top-down attentional modulation of visual neurons response into feature-based (Treue and Martínez Trujillo, 1999), spatial (McAdams and Maunsell, 1999), and a third type called object-based attention (Roelfsema et al., 1998). One controversial topic in attentional research has been whether the two former types of attention share similar neural mechanisms. In this issue of Neuron, two different electrophysiological studies using advanced Adriamycin price methodologies in behaving monkeys yield novel, complementary insights into this topic. In the first study,

Zhou and Desimone (2011) conducted simultaneous recordings from areas V4 and the frontal eye fields (FEF) of macaque monkeys during a visual

search task that selleckchem required the animals to memorize a visual cue presented at the beginning of a trial and then search, in a display composed of an array of different objects, for the one that matches the cue by directing gaze to single items (Figure 1A). Area V4 is located at a relatively early stage in the visual processing pathways and contains neurons selective for the color and shape of visual stimuli (Desimone and Schein, 1987). The FEF is located in the prefrontal cortex and contains neurons that encode the position of a visual stimulus, as well as the intended gaze position (Tehovnik et al., 2000). Some degree of shape selectivity has been reported in FEF neurons (Peng et al., 2008). Over the last decade, some studies have supported the role of the FEF as a source of top-down spatial attention signals that reach neurons in area V4 and modulate their sensitivity to visual inputs (Gregoriou et al., 2009 and Moore

and Armstrong, 2003). So far, the FEF role in feature-based attention has remained unclear. Zhou and Desimone (2011) found that during the visual search task, neurons in V4 and the FEF respond more strongly to the target stimulus or Methisazone to stimuli sharing the target features than to other stimuli. The authors discarded the possible role of spatial attention by analyzing trials in which saccades were made to a stimulus away from the receptive fields of the recorded neurons. Because in these trials the focus of spatial attention was not on the stimulus inside the neurons’ receptive fields but instead elsewhere at the position of the future saccadic eye movement, the authors conclude that the increase in response to stimuli matching the attended features was due to feature-based attention. Essential to their findings was that (1) the latency of this effect was shorter in FEF than in V4 neurons, and (2) the intensity of the response modulation was predictive of the efficiency of the visual search—as quantified by the number of saccades needed to find the target. This demonstrates that the FEF is a potential source of top-down signals during tasks that require feature-based attention.