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.

Odor habituation can modulate very early olfactory event-related potential.

Odor habituation is a phenomenon that after repeated exposure to an odor, is characterized by decreased responses to it. The central nervous system is involved in odor habituation. To study odor habituation in humans, measurement of event-related potentials (ERPs) has been widely used in the olfactory system and other sensory systems, because of their high temporal resolution. Most previous odor habituation studies have measured the olfactory ERPs of (200-800) ms. However, several studies have shown that the odor signal is processed in the central nervous system earlier than at 200 ms. For these reasons, we studied whether when odors were habituated, olfactory ERP within 200 ms of odors could change. To this end, we performed an odor habituation behavior test and electroencephalogram experiments. In the behavior test, under habituation conditions, odor intensity was significantly decreased. We found significant differences in the negative and positive potentials within 200 ms across the conditions, which correlated significantly with the results of the behavior test. We also observed that ERP latency depended on the conditions. Our study suggests that odor habituation can involve the olfactory ERP of odors within 200 ms in the brain.

Cross-cultural beliefs about memory and aging for self and others: South Korea and Canada.

Young adults in Canada (N = 161) and South Korea (N = 165) rated either themselves or typical others at target ages 25, 45, and 65 years. In both countries, poorer memory was anticipated with each increase in age on all 3 memory belief factors: capacity, change, and locus. Both groups demonstrated a self-protective bias about age-related decline, with Koreans showing a greater effect. These findings demonstrate the cross-cultural generality of negative memory stereotypes of middle and old age and the importance of self-other distinctions in age biases.

Communication beliefs about youth and old age in Asia and Canada.

Two cross-cultural studies compared beliefs in Asia and Canada about communication in later life. With an expanded version of the Language in Adulthood Questionnaire, respondents rated a young or old adult target on communication skills selected to elicit both negative and positive stereotypes. Chinese, Chinese-Canadian, and Canadian participants were compared in Study 1 while younger and older respondents from South Korea and Canada were contrasted in Study 2. All groups showed negative beliefs about hearing and memory in old age. Positive communication beliefs were also evident for empathy, storytelling and social skills. Participants in Asia showed less stereotyping overall, for both negative and positive beliefs. Significant age interactions in Study 2 reflected positive communication beliefs only for the older participants. In line with recent investigations of the multidimensional impact of Eastern traditions, greater positivity toward older adults was not observed in Asia. This work highlights the importance of assessing both positive and negative age beliefs in cross-cultural comparisons.