Microstructural characterization and high-temperature strength of hot-pressed silicon nitride ceramics with Lu2O3 additives

The microstructures of two hot-pressed Si₃N₄ ceramics, with 3.33 and 12.51 wt% Lu₂O₃ additive, have been characterized using transmission electron microscopy. The microstructures of both samples consisted of elongated β-Si₃N₄ grains and a secondary phase, contained in pockets surrounded by the grains, with a crystalline or amorphous form. In the 3.33 wt% Lu₂O₃-containing Si₃N₄ ceramic, all the multiple-grain junctions were completely crystalline while, in the 12.51 wt% Lu₂O₃-containing Si₃N₄ ceramic, approximately half the junctions were devitrified. A thin intergranular amorphous film present between the two-grain boundary was common; however, a film-free grain boundary was observed in the 12.51 wt% Lu₂O₃ sample. The film-free grain boundary was determined to be approximately 35%. Both ceramics fractured in four-point flexure between 1200 and 1600°C. Their high-temperature strength is closely associated with the nature of the grain-boundary phase formed during the sintering process.     

The illness concept in adolescent psychiatry

This paper introduces some important views on the clinical entities of the adolescent psychiatry in Japan. Shimizu shows the transitional region between neurosis, schizophrenia and normal. Murakami's new classification tells the relationship among the psychiatric disorders, especially about the borderline disorder. Hatotani's scheme deals with the atypical psychoses very well. According to the idea of Griesinger's "Einheitspsychose" arranges my symptomatic picture several ambiguous symptoms of the adolescent psychiatric disorders. In this picture we can understand the meaning of the borderline disorder. At last I give the catastrophic model of psychiatric disorders.     

The relation between preparatory stance and trunk rotation movements

The influence of preparatory stance on rotation movement reaction time of the trunk by bending of the knee and hip joint(s) was examined in 12 subjects. Four preparatory stances were examined: straight knee and hip extension (STAND), slight flexion of knee joints and hip joint (LIGHT), deep flexion (DEEP), and free initial position, i.e. that felt to be the most comfortable and effective (FREE). There was no significant influence of the preparatory stance on hip latency, but there were significant differences between the preparatory stances on response time (RT) and movement time (MT). Furthermore, using a quadratic curve fitting technique, knee joint angles of 24.8 degrees and a hip joint angle of 23.3 degrees were shown to be the optimum flexion angles in the preparatory stance for the initiation of quick trunk rotation movements. It is proposed that mechanical factors have considerably more effects on trunk rotation movements than does the nervous system.     

Emergence of symmetry in a visual conditional discrimination by chimpanzees (Pan troglodytes)

In Exp. 1, three young chimpanzees were trained to match red to a cross and green to a circle in an arbitrary matching-to-sample task. After acquisition of this task, they were tested for the emergence of associative symmetry of these conditional relations using the trials on which shapes were presented as samples and colors as comparisons. One of the three chimpanzees showed statistically significant accuracy on these test trials. This successful subject served in Exp. 2, in which an auditory-visual stimulus appeared contingent upon red and a cross while another auditory-visual stimulus was contingent upon green and a circle. This subject showed higher accuracies in symmetry tests than in Exp. 1, which suggested the facilitative effects of these events common to sample and correct comparison on the development of symmetry. In Exp. 3, subsequent tests in which only these stimuli were presented as samples indicated that these stimuli might have become the members of equivalence classes.     

Infant responses to maternal still-face at 4 and 9 months

This study investigated developmental changes in infant responses to maternal still-face (SF) situations. Infants (21 males and 25 females) of Japanese mothers were observed in a face-to-face SF paradigm, comprising four phases (normal/SF/normal/SF), at two infant ages (4 and 9 months). The infants' facial expression, gaze direction, and vocalization were coded in both SF and normal interaction conditions. The results indicated that infants at both ages showed a decrease in displaying positive facial expression and gazing at their mothers during SF conditions. The 4-month-old displayed emotional expression and directed their gaze toward their mothers more frequently than the 9-month-old. However, the 9-month-old vocalized more often in SF situations, attempting to elicit responses from their mothers. The "carry-over" effect was observed only in 9-month-old. The results were discussed in the context of developmental changes in infants' social skills to cope with an emotionally stressful situation.     

Orientation dependence of spatial memory acquired from auditory experience

The present study investigated whether memory for a room-sized spatial layout learned through auditory localization of sounds exhibits orientation dependence similar to that observed for spatial memory acquired from stationary viewing of the environment. Participants learned spatial layouts by viewing objects or localizing sounds and then performed judgments of relative direction among remembered locations. The results showed that direction judgments following auditory learning were performed most accurately at a particular orientation in the same way as were those following visual learning, indicating that auditorily encoded spatial memory is orientation dependent. In combination with previous findings that spatial memories derived from haptic and proprioceptive experiences are also orientation dependent, the present finding suggests that orientation dependence is a general functional property of human spatial memory independent of learning modality.     

Computer‐based teaching of Kanji construction and writing in a student with developmental disabilities

Students with developmental disabilities often have difficulty with writing skills such as tracing, copying, and dictation writing. A student with writing difficulties participated in the present study, which used computer‐based teaching applied in the home. We examined whether a student could copy Japanese Kanji characters after training with a constructed response matching‐to‐sample (CRMTS) procedure. The procedure was designed to teach identity Kanji construction. The results showed that the student not only acquired the constructed responses through this procedure but also to spelling generalized to copy trained and untrained Kanji characters. The results are discussed in terms of the effect of the CRMTS procedure on the acquisition and transfer of writing characters and the applicability of computer‐based home teaching. Copyright © 2008 John Wiley & Sons, Ltd.     

Testing assumptions of deliberate practice theory relevance, effort, and inherent enjoyment of practice with a novel task: study II

This study examined three assumptions of the theory of deliberate practice: that deliberate practice is perceived as relevant for improving performance and that it requires effort, but that it is not perceived as being inherently enjoyable. Of particular interest was how these perceptions change as practice difficulty changes. 30 college undergraduates practiced two different maze memorization and replication tasks and rated the practice relevance for improving performance on the task, the practice effort, and the inherent enjoyment of practice. The findings for each of the assumptions were consistent with those suggested by the theory and also showed that these perceptions are subject to the current performance on an activity and the difficulty of the practice.     

Computer‐based teaching of word construction and reading in two students with developmental disabilities

Students with developmental disabilities often have difficulty in learning the systematic relations between syllables (auditory stimuli) and characters (visual stimuli) required for reading. Two students with developmental disabilities participated in the present study which used computer‐based teaching applied in the home. We examined whether the students could read individual Japanese Hiragana characters after training with a constructional MTS procedure with differential outcome (DO) that was designed to teach word‐construction for pictured sample stimuli. The DO procedure provided the differential stimulus (in this case spoken syllables) after response selection. The results showed that the students not only acquired appropriate word‐construction responses through this task, they also learned to read Hiragana characters without direct training of this skill. The results are discussed in terms of the effect of the constructional MTS procedure with DO on the acquisition and transfer of reading characters and the applicability of computer‐based home teaching. Copyright © 2007 John Wiley & Sons, Ltd.     

Entorhinal cortical Island cells regulate temporal association learning with long trace period

Temporal association learning (TAL) allows for the linkage of distinct, nonsynchronous events across a period of time. This function is driven by neural interactions in the entorhinal cortical–hippocampal network, especially the neural input from the pyramidal cells in layer III of medial entorhinal cortex (MECIII) to hippocampal CA1 is crucial for TAL. Successful TAL depends on the strength of event stimuli and the duration of the temporal gap between events. Whereas it has been demonstrated that the neural input from pyramidal cells in layer II of MEC, referred to as Island cells, to inhibitory neurons in dorsal hippocampal CA1 controls TAL when the strength of event stimuli is weak, it remains unknown whether Island cells regulate TAL with long trace periods as well. To understand the role of Island cells in regulating the duration of the learnable trace period in TAL, we used Pavlovian trace fear conditioning (TFC) with a 60-sec long trace period (long trace fear conditioning [L-TFC]) coupled with optogenetic and chemogenetic neural activity manipulations as well as cell type-specific neural ablation. We found that ablation of Island cells in MECII partially increases L-TFC performance. Chemogenetic manipulation of Island cells causes differential effectiveness in Island cell activity and leads to a circuit imbalance that disrupts L-TFC. However, optogenetic terminal inhibition of Island cell input to dorsal hippocampal CA1 during the temporal association period allows for long trace intervals to be learned in TFC. These results demonstrate that Island cells have a critical role in regulating the duration of time bridgeable between associated events in TAL.

The linkage of temporally discontiguous events, called temporal association learning (TAL), is an essential function for episodic memory formation; for animals, when an event took place, and in what order a series of events occurred is directly linked to adaptation to continuous changes in the environment (Eichenbaum 2000; Tulving 2002a,b; Kitamura et al. 2015a; Kitamura 2017; Pilkiw and Takehara-Nishiuchi 2018). The entorhinal cortical–hippocampal (EC-HPC) network in particular is currently considered to bridge the temporal discontinuity between events (Solomon et al. 1986; Moyer et al. 1990; Wallenstein et al. 1998; McEchron et al. 1999; Eichenbaum 2000; Huerta et al. 2000; Ryou et al. 2001; Takehara et al. 2003; Chowdhury et al. 2005; Esclassan et al. 2009; Morrissey et al. 2012; Suter et al. 2013; Sellami et al. 2017; Wilmot et al. 2019).Two major excitatory inputs to HPC arise from the superficial layers of the EC (Fig. 1A), forming the direct (monosynaptic), and indirect (trisynaptic) pathways (Amaral and Witter 1989; Amaral and Lavenex 2007; Kitamura 2017; Kitamura et al. 2017). While pyramidal cells in EC layer III (ECIII cells) project directly to CA1 (Kohara et al. 2014; Kitamura et al. 2015b), the trisynaptic pathway originates from excitatory Reelin⁺ stellate cells in EC layer II (ECII) projecting directly to DG, CA3, and CA2 (Fig. 1B; Tamamaki and Nojyo 1993; Varga et al. 2010). CalbindinD-28K⁺/Wolfram syndrome 1 (Wfs1)⁺ pyramidal cells, another excitatory neural population in EC layer II called “Island cells,” form cell clusters along the ECII/ECI border (Alonso and Klink 1993; Fujimaru and Kosaka 1996; Klink and Alonso 1997; Kawano et al. 2009; Varga et al. 2010; Kitamura et al. 2014; Ray et al. 2014) and directly project to the GABAergic interneurons of stratum lacunosum (SL-INs) in HPC CA1 and drive feedforward inhibition to HPC CA1 pyramidal cells (Fig. 1B; Kitamura et al. 2014; Surmeli et al. 2016; Kitamura 2017; Ohara et al. 2018; Yang et al. 2018; Zutshi et al. 2018).Open in a separate windowFigure 1.Circuit schematic diagram of the medial entorhinal cortex (MEC)–hippocampal (HPC) circuit. (A) Major projections in the entorhinal cortical (EC)-HPC network. ECIII neurons (green) project directly to CA1. ECII Ocean cells (ECIIo, purple) project to the dentate gyrus (DG) (light blue)/CA3 (pink) initiating the trisynaptic pathway. ECII Island cells (ECIIi, blue) project directly into CA1. (B) ECIII projections (green) excite the distal portions of CA1 pyramidal cell (yellow) dendrites in the stratum moleculare. Island cells (ECIIi, blue) excite the interneurons of stratum lacunosum (SL-INs, red), which in turn inhibit the distal dendrites of CA1 pyramidal cells in SL.Trace fear conditioning (TFC) has been established as one suitable animal model for TAL (Fendt and Fanselow 1999; Maren 2001; Kim and Jung 2006) that can be also used as a translational bridge between animal and human learning (Clark and Squire 1998; Buchel and Dolan 2000; Delgado et al. 2006). Lesion, pharmacological, molecular, and optogenetic manipulation, as well as disease models in medial entorhinal cortex (MEC), demonstrate that MEC is crucial for TFC and temporal learning (Ryou et al. 2001; Woodruff-Pak 2001; Runyan et al. 2004; Esclassan et al. 2009; Gilmartin and Helmstetter 2010; Suh et al. 2011; Morrissey et al. 2012; Shu et al. 2016; Hales et al. 2018; Yang et al. 2018; Heys et al. 2020). Specifically, MECIII inputs into the HPC CA1 pyramidal cells are essential for the formation of TFC (Yoshida et al. 2008; Suh et al. 2011; Kitamura et al. 2014; Kitamura 2017). However, the temporal association function driven by MECIII neurons must be regulated for optimal adaptive memory formation, as too strong an association of a particular pair of events may interfere with associations of other useful pairs, whereas too weak an association for a given pair of events, in terms of weaker impact of events or longer duration of temporal gap between events, would not result in an effective memory (Kitamura et al. 2015a; Marks et al. 2020). In a naturalistic context, this would mean that more distant/quieter sounds, less intense somatic sensations (e.g., pain), or increased temporal distance between any two events would signal that the events are less likely to be causally associated, therefore less relevant, and less likely to be stored and recalled. In fact, successful TFC depends on the strength of event stimuli and duration of temporal gap between events (Stiedl and Spiess 1997; Misane et al. 2005; Kitamura et al. 2014; Kitamura 2017). However, the underlying regulatory mechanism for TAL remains hidden. Previously we demonstrated that feedforward inhibition by Island cells acts as a gating controller for the MECIII inputs to the distal dendrites of HPC CA1 pyramidal cells in stratum moleculare (SM) (Kitamura et al. 2014) to control TFC when weaker (in this case diminished footshock intensity) unconditioned stimuli were delivered for TFC, indicating that Island cell activity controls the temporal association when the strength of two discontinuous events are relatively weaker. However, the way in which the EC-HPC network regulates TFC with a longer trace period still remains unknown. Because the activation of Island cells would result in a net inhibitory effect on the local network in CA1, imposing a tight and specific regulation on associations of events across the temporal gap in TAL (Crestani et al. 2002; Moore et al. 2010; Kitamura et al. 2014, 2015b), we hypothesized that the length of the temporal gap between events would also be modulated by this mechanism. In this study, we examined the role of the regulatory input to this circuit arising specifically from the Island cells in the MECII using apoptotic elimination of Island cells, chemogenetic neural inhibition, and optogenetic terminal inhibition methods within an L-TFC protocol to give a thorough and complete assessment of the circuit involvement while considering each technique''s unique features.