Most visual areas also showed face selectivity under anesthesia, including prefrontal areas. The difference in stimulus size between awake and anesthetized animals did not lead to any differences between awake and anesthetized animals, most likely because faces were contrasted 17-AAG against other categories and because many of the reported areas are size invariant. The areas that showed no consistent activation under anesthesia were the amygdala and the hippocampus. Both awake animals showed bilateral activation in the amygdala, in agreement with earlier studies (Hadj-Bouziane et al., 2008 and Hoffman et al., 2007). Only one animal showed activation

in the amygdala under anesthesia. However, face-selective responses may not have reached significance in the anesthetized monkeys, because faces were contrasted against fruit and the amygdala also showed significant

responses to fruit in awake monkeys (p < 0.05). The amygdala has a high μ-opioid receptor density (Mansour et al., 1988) and it is also possible that binding of remifentanil may have reduced its neural responses. There are two caveats concerning the results from anesthetized monkeys. One is that the results may depend on the type of anesthesia and results may not generalize to other anesthesia regimens because different anesthetics AZD2281 mw affect cognitive processing differently. The other concerns the interpretation of the BOLD signal. It has been shown in V1 that the BOLD signal better represents the input to an area and its local processing than its output and that functional activation can occur in the absence of of spiking (Goense and Logothetis, 2008 and Logothetis et al., 2001). The conservative interpretation of preserved BOLD signal in a brain area would be that this means the activated area receives synaptic input. What types of further neural processes take place, whether

these differ between awake and anesthetized animals, and how they relate to single- or multiunit electrophysiological data (neural output) remains subject to further investigation. Conversely, a lack of BOLD signal could signify a lack of input from an earlier area. The issue of interpretation of the BOLD signal is independent of anesthesia, however, and is also relevant for awake subjects. The importance of the MTL in learning and memory function is well established. Area TE, the perirhinal (Brodmann areas 35 and 36) and parahippocampal cortices, the entorhinal cortex, and the hippocampus have all been shown to be involved in learning and memory (Osada et al., 2008 and Squire et al., 2004) with different structures mediating different (and possibly overlapping) functions, i.e., forming associations between objects, forming associations between objects and locations, or forming memories of scenes or locations. Although face selectivity is usually not explicitly tested, neural and BOLD responses to faces were shown in the human MTL in the context of memory and familiarity (Eichenbaum et al., 2007, Gonsalves et al.