Evolution, Discovery, and Interpretations of Arthropod Mushroom Bodies

Mushroom bodies are prominent neuropils found in annelids and in all arthropod groups except crustaceans. First explicitly identified in 1850, the mushroom bodies differ in size and complexity between taxa, as well as between different castes of a single species of social insect. These differences led some early biologists to suggest that the mushroom bodies endow an arthropod with intelligence or the ability to execute voluntary actions, as opposed to innate behaviors. Recent physiological studies and mutant analyses have led to divergent interpretations. One interpretation is that the mushroom bodies conditionally relay to higher protocerebral centers information about sensory stimuli and the context in which they occur. Another interpretation is that they play a central role in learning and memory. Anatomical studies suggest that arthropod mushroom bodies are predominately associated with olfactory pathways except in phylogenetically basal insects. The prominent olfactory input to the mushroom body calyces in more recent insect orders is an acquired character. An overview of the history of research on the mushroom bodies, as well as comparative and evolutionary considerations, provides a conceptual framework for discussing the roles of these neuropils.     

The Organization of Extrinsic Neurons and Their Implications in the Functional Roles of the Mushroom Bodies in Drosophila melanogaster Meigen

Although the importance of the Drosophila mushroom body in olfactory learning and memory has been stressed, virtually nothing is known about the brain regions to which it is connected. Using Golgi and GAL4–UAS techniques, we performed the first systematic attempt to reveal the anatomy of its extrinsic neurons. A novel presynaptic reporter construct, UAS-neuronal synaptobrevin–green fluorescent protein (n-syb–GFP), was used to reveal the direction of information in the GAL4-labeled neurons. Our results showed that the main target of the output neurons from the mushroom body lobes is the anterior part of the inferior medial, superior medial, and superior lateral protocerebrum. The lobes also receive afferents from these neuropils. The lack of major output projections directly to the deutocerebrum’s premotor pathways discourages the view that the role of the mushroom body may be that of an immediate modifier of behavior. Our data, as well as a critical evaluation of the literature, suggest that the mushroom body may not by itself be a “center” for learning and memory, but that it can equally be considered as a preprocessor of olfactory signals en route to “higher” protocerebral regions.     

Influence of in utero exposure to maternal depression and natural disaster-related stress on infant temperament at 6 months: The children of Superstorm Sandy

This study examined the effects of in utero exposure to maternal depression and Superstorm Sandy, a hurricane that hit metropolitan New York in 2012, on infant temperament at 6 months. Temperament was assessed using the Infant Behavior Questionnaire-Revised. Maternal depression was measured by the Edinburgh Postnatal Depression Scale. The main effects and the interaction of maternal depression and Sandy exposure on infant temperament were examined using a multivariable generalized linear model. Results show that prenatal maternal depression was associated with lower emotion regulation and greater distress. Stratification and interaction analyses suggested that the adverse effects of prenatal maternal depression on problematic temperament were amplified by in utero Sandy exposure. This study underscores the importance of providing prenatal screening and treatment for maternal depression during pregnancy while also identifying high-risk families who may have suffered from disaster-related traumas to provide necessary services. As the frequency of natural disasters may increase due to climate change, it is important to understand the consequences of in utero stress on child development and to formulate plans for early identification.     

A Bayesian Semiparametric Item Response Model with Dirichlet Process Priors

In Item Response Theory (IRT), item characteristic curves (ICCs) are illustrated through logistic models or normal ogive models, and the probability that examinees give the correct answer is usually a monotonically increasing function of their ability parameters. However, since only limited patterns of shapes can be obtained from logistic models or normal ogive models, there is a possibility that the model applied does not fit the data. As a result, the existing method can be rejected because it cannot deal with various item response patterns. To overcome these problems, we propose a new semiparametric IRT model using a Dirichlet process mixture logistic distribution. Our method does not rely on assumptions but only requires that the ICCs be a monotonically nondecreasing function; that is, our method can deal with more types of item response patterns than the existing methods, such as the one-parameter normal ogive models or the two- or three-parameter logistic models.     

On the (non)categorical perception of lexical tones

Identification and discrimination of lexical tones in Cantonese were compared in the context of a traditional categorical perception paradigm. Three lexical tone continua were used: one ranging from low level to high level, one from high rising to high level, and one from low falling to high rising. Identification data showed steep slopes at category boundaries, suggesting that lexical tones are perceived categorically. In contrast, discrimination curves generally showed much weaker evidence for categorical perception. Subsequent investigation showed that the presence of a tonal context played a strong role in the identification of target tones and less of a role in discrimination. The results are consistent with the hypothesis that tonal category boundaries are determined by a combination of regions of natural auditory sensitivity and the influence of linguistic experience.     

A study of antecedents of organizational commitment

Various theories of organizational behaviors suggest that there should be significant relationships between the work-related variables and commitment to an organization. This study shows that, for a sample of 203 Japanese industrial workers, four components (attachment, internalization, normative, and continuance) of organizational commitment are predicted by organizational climate, supervisory behavior, organizational tenure, and role clarity. Implications for future research are discussed.     

Development, Reliability, and Validity of the Beliefs Toward Mental Illness Scale

The present study describes the development of a new scale to measure Beliefs toward Mental Illness (BMI), which was designed to measure cross-cultural differences in such beliefs as well as to predict treatment-seeking behavior among different cultural groups. A total of 216 students participated in this study (114 Asian students and 102 American students). A series of factor analyses examining construct validity for the BMI revealed that the BMI has three dimensions, including dangerousness, poor social and interpersonal skills, and incurability. Examination of the reliability estimates for each factor revealed moderate to high internal consistency of the BMI. Comparisons between American and Asian students revealed the expected cultural differences in their beliefs toward mental illness and treatment preference.     

The Relative Contribution of Diagnostic and Psychosocial Variables to Severity of Suicidal Ideation

The present study examined the relative contribution of diagnostic and psychosocial factors to the prediction of severity of suicidal ideation in a sample of 78 college students. Using hierarchical regression analyses to control for each set of factors, psychosocial variables were found to consistently predict level of suicidal ideation. In contrast, diagnostic variables including diagnosis of substance abuse and composite scores for depression and anxiety were unrelated to level of suicidality. An examination of individual diagnoses revealed no predictable relationships with severity of suicidality in this population. The results were discussed from several methodological viewpoints.     

Slow movement execution in event-related potentials (P300)

We examined whether slow movement execution has an effect on cognitive and information processing by measuring the P300 component. 8 subjects performed a continuous slow forearm rotational movement using 2 task speeds. Slow (a 30-50% decrease from the subject's Preferred speed) and Very Slow (a 60-80% decrease). The mean coefficient of variation for rotation speed under Very Slow was higher than that under Slow, showing that the subjects found it difficult to perform the Very Slow task smoothly. The EEG score of alpha-1 (8-10 Hz) under Slow Condition was increased significantly more than under the Preferred Condition; however, the increase under Very Slow was small when compared with Preferred. After performing the task. P300 latency under Very Slow increased significantly as compared to that at pretask. Further, P300 amplitude decreased tinder both speed conditions when compared to that at pretask, and a significant decrease was seen under the Slow Condition at Fz, whereas the decrease under the Very Slow Condition was small. These differences indicated that a more complicated neural composition and an increase in subjects' attention might have been involved when the task was performed under the Very Slow Condition. We concluded that slow movement execution may have an influence on cognitive function and may depend on the percentage of decrease from the Preferred speed of the individual.     

Properties of internal speed control and psychophysiological response during continuous forearm rotation movement.

This study investigated the properties of speed control and psychophysiological response when subjects changed movement speed internally. The task consisted of a continuous forearm rotational movement, which 14 women performed under 3 conditions, namely, (1) Preferred: the subject performed the task at a freely selected speed, (2) Slow: the subject changed the speed in two steps from preferred to a slower pace (slow, then very slow), (3) Fast: the subject changed the speed in two steps from preferred to a faster pace (fast, then very fast). Rotation speed and the coefficient of variation were measured to evaluate within-subject variability. Under the Preferred condition, there were no significant differences in rotation speed or coefficient of variation during the trials. However, under Slow and Fast conditions, the standard variation scores and coefficient of variation indicated different tendencies. Under the Fast condition, although the standard variation increased with the faster speed, the coefficient of variation decreased. On the other hand, the coefficient of variation increased under the Slow condition. Preferred speed had a significant positive relationship to the slow, very slow, fast, and very fast speeds. Heart rate (R-R interval) and EEG spectral intensity measurements showed no significant changes among the three conditions: however, respiration frequency significantly increased during Fast as compared to Preferred and Slow conditions. These results suggest that a preferred speed for continuous movement exists and that it is closely related to internal speed control as a psychological criterion. Furthermore, different movement speeds may reflect different psychophysiological responses.