Time Course of Odor Categorization Processing.

The brain's mechanisms for categorizing different odors have long been a research focus. Previous studies suggest that odor categorization may involve multiple neurological processes within the brain with temporal and spatial neuronal activation. However, there is limited evidence regarding temporally mediated mechanisms in humans, especially millisecond odor processing. Such mechanisms may be important because different brain areas may play different roles at a particular activation time during sensory processing. Here, we focused on how the brain categorizes odors at specific time intervals. Using multivariate electroencephalography (EEG) analysis, we found that similarly perceived odors induced similar EEG signals during 50-100, 150-200, and 350-400 ms at the theta frequency. We also found significant activation at 100-150 and 350-400 ms at the gamma frequency. At these two frequencies, significant activation was observed in some olfactory-associated areas, including the orbitofrontal cortex. Our findings provide essential evidence that specific periods may be related to odor quality processing during central olfactory processing.

Regulation of habenular G-protein gamma 8 on learning and memory via modulation of the central acetylcholine system.

Guanine nucleotide binding protein (G protein) gamma 8 (Gng8) is a subunit of G proteins and expressed in the medial habenula (MHb) and interpeduncular nucleus (IPN). Recent studies have demonstrated that Gng8 is involved in brain development; however, the roles of Gng8 on cognitive function have not yet been addressed. In the present study, we investigated the expression of Gng8 in the brain and found that Gng8 was predominantly expressed in the MHb-IPN circuit of the mouse brain. We generated Gng8 knockout (KO) mice by CRISPR/Cas9 system in order to assess the role of Gng8 on cognitive function. Gng8 KO mice exhibited deficiency in learning and memory in passive avoidance and Morris water maze tests. In addition, Gng8 KO mice significantly reduced long-term potentiation (LTP) in the hippocampus compared to that of wild-type (WT) mice. Furthermore, we observed that levels of acetylcholine (ACh) and choline acetyltransferase (ChAT) in the MHb and IPN of Gng8 KO mice were significantly decreased, compared to WT mice. The administration of nAChR α4ß2 agonist A85380 rescued memory impairment in the Gng8 KO mice, suggesting that Gng8 regulates cognitive function via modulation of cholinergic activity. Taken together, Gng8 is a potential therapeutic target for memory-related diseases and/or neurodevelopmental diseases.

EEG Revealed That Fragrances Positively Affect Menopausal Symptoms in Mid-life Women.

During mid-life, women experienced not only physical but also neurological transition. Because of this, many women suffer from physiological and/or psychological menopausal symptoms. Although hormone therapy (HT) was broadly used to alleviate menopausal symptoms, HT showed inconsistent effects in case of psychological symptoms. Moreover, mid-life women's brains have distinct characteristics than in other periods of life, it is needed to study psychological symptoms in shifted brain network of mid-life women. As an alternative, inhalation of fragrances may alleviate psychological menopausal symptoms. To characterize the alleviation mechanism by fragrances, we tested the effect of fragrances on menopausal symptoms using electroencephalographic (EEG) methods. We hypothesized that fragrance could restore mid-life women's brain response to stressful situations. We tested six fragrance conditions, including no-odor condition (solvent only) in twenty-eight mid-life women (49.75 years±3.49). Our results showed that fragrances increased alpha power and decreased ß/α ratio depending on the severity of menopausal symptoms in a stressful situation. Our study would be helpful in psychological menopausal symptom alleviation as well as fragrance screening for well-being in mid-life.