![]() ![]() The putamen is a structure that has been implicated in the perception of contempt and disgust damage to the putamen and insula apparently compromises a patient’s ability to recognize signals of disgust. In contrast, PAR patients exhibit stronger activation in the thalamus, known to be related to directed attention in relation to the sense of smell, and the putamen. The aim of the present study was to further investigate possible differences in the central processing of hyposmic patients with parosmia compared to hyposmic patients without parosmia. The decreased olfactory bulb volume of patients with parosmia may indicate that there may be a decreased number of bulb interneurons, and therefore, a decreased lateral inhibition, that may allow olfactory activation to produce an irregular pattern, which then results in an altered olfactory perception. ![]() Another hypothesis relates to the idea that parosmias are the result of an aberrant central-nervous processing of odors, e.g., in the olfactory bulb and/or integrative/interpretative centers in the olfactory-eloquent brain structures. One explanation relates to the periphery of the olfactory system where partial dysfunction of olfactory receptor neurons leads to the inability to form a typical, odor-specific pattern of activation in the olfactory bulb. The cause of qualitative olfactory dysfunction is unclear. Discussion: These results are consistent with the hypothesis that there are specific patterns in the central processing of olfactory stimuli which differ in hyposmic patients with and without parosmia. In HYP patients a stronger activation was observed in the medial orbitofrontal cortex, anterior cingulate cortex, and parahippocampal gyrus, whereas in the PAR group stronger activation in the thalamus and putamen was seen. Results: The two groups exhibited different patterns of activation. The olfactory smells used were peach and coffee odors. Both groups were matched with regard to sex and age. Material and Methods: A total of 23 patients were investigated, 12 hyposmic patients without parosmia (HYP group) and 11 hyposmic patients with parosmia (PAR group). The focus of the present study was, using functional MRI, to compare the central processing of olfactory stimulation in patients with qualitative smell disorders. ![]() Qualitative smell disorders have heretofore been poorly investigated. These patients with such a qualitative smell disorder are often more severely affected than patients exhibiting only a quantitative smell disorder. Introduction: A number of patients with a diminished sense of smell also can suffer from parosmia. ![]()
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