Stimulus-specific expectations induced corresponding response biases during odor sampling: subjects misclassified a given stimulus more often when preceded by an incongruent target cue, for example, mistaking odor B for odor A when searching for A. Similarly, reaction times were slower when subjects expected one odor

but received another. By comparison, selleck chemicals llc in PPC, target-related ensemble codes before odor onset gave way to stimulus-specific codes after odor onset, whereby activity patterns more closely resembled what was delivered rather than what was being expected (Figure 3 and Figure 4). This response profile implies that PPC plays a highly dynamic role at the interface between sensation, expectation, and perception. Insofar as the pre-stimulus target patterns (e.g., odor A target) and the poststimulus odor patterns (e.g., odor A stimulus) shared significant pattern overlap in PPC (Figure 5), our findings directly show that predictive “templates” or “search images” are represented here. That the robustness of predictive coding in PPC facilitated odor perception in a stimulus-specific manner (compare to Figure 6) further underscores the key involvement of this brain area in generating spatially distributed templates with literal functional correspondence to the actual odor patterns, in accordance with longstanding anatomical and computational models of piriform function (Freeman and Schneider,

1982, Haberly, 2001, Hasselmo et al., 1990, Ojima et al., 1984 and Wilson and Stevenson, 2003). Curiously, the relevance of persisting target LBH589 solubility dmso patterns in APC and OFC to odor perception is unclear given that these patterns (unlike those in PPC) did not correlate with behavior.

It is important to note that the subjects in our study performed relatively GABA Receptor slowly on this task, taking between 3 and 4 s on average to make a decision. Therefore, it is plausible that within this postsniff time frame, an ongoing trace in APC may have helped optimize the attentional search, without itself correlating directly with perceptual performance. Ultimately, how these prestimulus codes in APC and OFC influence odor perception remains unresolved. Human psychophysical and neuroimaging studies increasingly indicate that olfactory perception benefits from odor imagery and cognitive modulation. For example, imagination of a specific smell alters sniffing behavior, enhances odor detection accuracy, and elicits fMRI activations in anterior (frontal) piriform cortex and posterior OFC (Bensafi et al., 2007, Bensafi et al., 2003, Djordjevic et al., 2004 and Djordjevic et al., 2005). Similarly, contextual presentation of nonolfactory semantic information, such as pictures or word labels, modifies both odor perception and OFC response profiles in a stimulus-specific manner (de Araujo et al., 2005, Gottfried and Dolan, 2003, Herz and von Clef, 2001 and Herz, 2003).