Amygdaloid–Striatal Substrates Underlying Odor Hedonics and Odor-Guided Behaviors

tory tubercle by the amygdala. The olfactory tubercle is a striatal structure with a cortical-like organization which displays odor-evoked activity and may be critical for olfactory perception (Wesson and Wilson, 2011). The anatomical findings by Novejarque et al. (2011) along with those of previous groups (Usunoff et al., 2009) suggest the involvement of the olfactory tubercle (and perhaps the tubercle’s strong connections with the basal ganglia) in the emotional regulation of olfactory perception and the strong hedonic responses evoked by odors (e.g., Herz and Cupchick, 1995). Despite this, without data showing the role of the olfactory tubercle to olfactory processing, little can be inferred regarding the amygdala innervation of the olfactory tubercle. Another major contribution of the present study was the finding that all cortical amygdaloid nuclei (excluding the piriform cortex) innervate the major island of Calleja. This was especially the case for the posteromedial cortical amygdaloid nucleus. The islands of Calleja are dense granule cell clusters residing mostly within layers II and III of the olfactory tubercle in rodents and largely in the nucleus accumbens in humans. However, the function of the islands of Calleja is unknown. Thus while this finding by Novejarque et al. (2011) is difficult to interpret in terms of functional consequences, it is almost undoubted that the amygdala’s dense innervation of the major island of Calleja will be found important to the emotional modulation of odor perception (given their positioning within the olfactory tubercle) and to the regulation of sociosexual behaviors. There are ample future directions to link these anatomical findings by Novejarque et al. (2011) to functional significance. First, and most recently discussed, would elimination or inactivation of the major island of Calleja abolish associative changes in odor hedonics? This of course is based upon the Amygdaloid–striatal substrates underlying odor hedonics and odor-guided behaviors