A preliminary investigation of olfactory function in olfactory and auditory-verbal hallucinators with schizophrenia, and normal controls

Correlation Between Cortical Thickness Abnormalities of the Olfactory Sulcus and Olfactory Identification Disorder and Persistent Auditory Verbal Hallucinations in Chinese Patients With Chronic Schizophrenia

BACKGROUND AND HYPOTHESIS

Persistent auditory verbal hallucinations (pAVHs) and olfactory identification impairment are common in schizophrenia (SCZ), but the neuroimaging mechanisms underlying both pAVHs and olfactory identification impairment are unclear. This study aimed to investigate whether pAVHs and olfactory identification impairment in SCZ patients are associated with changes in cortical thickness.

STUDY DESIGN

In this study, cortical thickness was investigated in 78 SCZ patients with pAVHs (pAVH group), 58 SCZ patients without AVHs (non-AVH group), and 83 healthy controls (HC group) using 3T magnetic resonance imaging. The severity of pAVHs was assessed by the Auditory Hallucination Rating Scale. Olfactory identification deficits were assessed using the Odor Stick Identification Test for Japanese (OSIT-J). In addition, the relationship between the severity of pAVHs and olfactory identification disorder and cortical thickness abnormalities was determined.

STUDY RESULTS

Significant reductions in cortical thickness were observed in the right medial orbital sulcus (olfactory sulcus) and right orbital sulcus (H-shaped sulcus) in the pAVH group compared to both the non-AVH and HC groups (P < .003, Bonferroni correction). Furthermore, the severity of pAVHs was found to be negatively correlated with the reduction in cortical thickness in the olfactory sulcus and H-shaped sulcus. Additionally, a decrease in cortical thickness in the olfactory sulcus showed a positive correlation with the OSIT-J scores (P < .05, false discovery rate correction).

CONCLUSIONS

Cortical thickness abnormalities in the olfactory sulcus may be a common neuroimaging mechanism for pAVHs and olfactory identification deficits in SCZ patients.

The Phenomenology of Visual and Other Nonauditory Hallucinations in Affective and Nonaffective Psychosis: A Mixed Methods Analysis

ABSTRACT

Nonauditory hallucinations in psychosis have not received as much attention relative to voice-hearing experiences. The current paper aimed to document the characteristics of these hallucinations in affective and nonaffective psychosis. Participants were selected from a primary voice-hearing sample, who had endorsed visual, tactile, or olfactory hallucinations ( N = 55-75). A comprehensive, semistructured phenomenological interview was conducted, followed by mixed methods analysis. Visual hallucinations typically occurred daily, for a few minutes per episode, within one's direct line of sight; persons and/or animals were most commonly seen, with low controllability and mostly engendered negative affective outcomes. Tactile and olfactory hallucinations were endorsed by 46.8% and 39.0% of participants, respectively. The affective psychosis group ( n = 33) reported significantly greater awareness and lower functional impairment relative to the nonaffective psychosis group ( n = 42). Qualitative thematic analysis revealed notable themes and subthemes across each of these hallucinations modes. Further phenomenological investigations should be carried out in lesser known hallucination modalities, assisted by the development of appropriate assessment tools.

Differences in olfactory dysfunction and its relationship with cognitive function in schizophrenia patients with and without auditory verbal hallucinations

Olfactory discrimination dysfunction has been observed in patients with schizophrenia (SCZ), but its relationship with cognitive function has not been clarified. The purpose of this study was to examine the differences in olfactory identification function in SCZ patients with and without auditory verbal hallucinations (AVHs) and its relationship with cognitive function. Olfactory identification function was measured in 80 SCZ patients with AVHs, 57 SCZ patients without AVHs, and 87 healthy controls (HC). Clinical symptom scores and neuropsychological measures were also administered to all corresponding subjects. Compared to HC, SCZ patients showed significant deficits in olfactory identification and cognitive function, but there were no differences in olfactory identification dysfunction and cognitive dysfunction between the two subgroups. In the non-AVHs subgroup only, poorer Olfactory Stick Identification Test for Japanese (OSIT-J) scores were significantly and positively correlated with total and delayed recall (Bonferroni correction, p < 0.002). Stepwise regression analysis revealed that factors affecting olfactory identification impairment differed in the two SCZ patient subgroups. In conclusion, this study highlights the commonality of olfactory identification dysfunction in SCZ patients and the importance of olfactory assessment of different subtypes of SCZ patients.