A Specific Role for the Human Amygdala in Olfactory Memory

Abstract

The medial temporal lobe is known to play a role in the processing of olfaction and memory. The specific contribution of the human amygdala to memory for odors has not been addressed, however. The role of this region in memory for odors was assessed in patients with unilateral amygdala damage due to temporal lobectomy (n = 20; 11 left, 9 right), one patient with selective bilateral amygdala damage, and in 20 age-matched normal controls. Fifteen odors were presented, followed 1 h later by an odor-name matching test and an odor-odor recognition test. Signal detection analyses showed that both unilateral groups were impaired in their memory for matching odors with names, these patients were not significantly impaired on odor-odor recognition. Bilateral amygdala damage resulted in severe impairment in both odor-name matching as well as in odor-odor recognition memory. Importantly, none of the patients were impaired on an auditory verbal learning task, suggesting that these findings reflect a specific impairment in olfactory memory, and not merely a more general memory deficit. Taken together, the data provide neuropsychological evidence that the human amygdala is essential for olfactory memory.Considerable research has illustrated a role for the anteromesial temporal lobes in several aspects of olfactory processing, including odor detection (Rausch and Serafetinides 1975;Eichenbaum et al. 1983), discrimination (Abraham and Mathai 1983), and memory (Rausch et al. 1977;Martinez et al. 1993;Dade et al. 2002). Some authors have suggested a preferential role of the right temporal cortex in olfactory memory (Rausch et al. 1977)-in line with a material-specific advantage of the left hemisphere for verbal memory and the right hemisphere for nonverbal memory (Dobbins et al. 1998;Buchanan et al. 2001). In contrast, Henkin and colleagues described a study in which left temporal excision resulted in greater impairment in olfactory recognition than did right-sided damage (Henkin et al. 1977). However, more recent work has shown that both the right and the left temporal lobes are likely involved in odor memory. Dade et al. (2002) demonstrated the participation of both the right and left temporal lobes in olfactory memory both in a lesion study in patients with temporal lobe damage as well as in a functional neuroimaging experiment using normal participants.The temporal lobes contain several areas known to be involved in olfactory processing, including the piriform cortex, which is located at the frontotemporal junction, the entorhinal cortex, the periamygdaloid cortex, and anterior cortical nucleus of the amygdala (Eslinger et al. 1982;West and Doty 1995;Savic 2001). The specific role of the human amygdala in olfactory processing has been the focus of several studies in lesion patients (Babinsky et al. 1993;Markowitsch et al. 1994), and using the techniques of functional neuroimaging ( (1993) and Markowitsch et al. (1994) showed impaired odor-paired associate learning in two patients with selective bilateral amygdala damage. Fu...

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Combined Application of Behavior Genetics and Microarray Analysis to Identify Regional Expression Themes and Gene–Behavior Associations

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