Biology subjects

Shinozaki, T.

Publications and source records attributed to Shinozaki, T..

3 recordsLinked to original sources

bioRxiv2023

Analysis of convolutional neural networks reveals the computational properties essential for subcortical processing of facial expression

Perception of facial expression is crucial in the social life of primates. This visual information is processed along the ventral cortical pathway and the subcortical pathway. Processing of face information in the subcortical pathway is inaccurate, but the architectural and physiological properties that are responsible remain unclear. We analyzed the performance of convolutional neural networks incorporating three prominent properties of this pathway: a shallow layer architecture, concentric receptive fields at the first processing stage, and a greater degree of spatial pooling. The neural networks designed in this way could be trained to classify seven facial expressions with a correct rate of 51% (chance level, 14%). This modest performance was gradually improved by replacing the three properties, one-by-one, two at a time, or all three simultaneously, with the corresponding features in the cortical pathway. Some processing units in the final layer were sensitive to spatial frequencies (SFs) in the retina-based coordinate, whereas others were sensitive to object-based SFs, similar to neurons in the amygdala. Replacement of any one of these properties affected the SF coordinate of units. All three properties constrain the accuracy of facial expression information in the subcortical pathway, and are essential for determining the coordinate of SF representation.

neuroscience↗

bioRxiv2020

Ergothioneine, a metabolite of the gut bacterium Lactobacillus reuteri, protects against stress-induced sleep disturbances

The relationships between depression and gut microbiota, particularly those involving the immune system, have become a major focus of recent research. Here, we analyzed changes in gut microbiota and their sulfur metabolites in the feces of a depression rat model using the modified 14-day social defeat stress (SDS) paradigm. Our results showed that SDS increased fecal Lactobacillus reuteri in correlation with ergothioneine levels at around day 11, which continued for at least one month following SDS administration. In vitro study further revealed that L. reuteri is capable of producing ergothioneine. Although the known anti-inflammatory and anti-oxidative actions of ergothioneine suggested that the increased fecal ergothioneine levels may be related to intestinal anti-inflammatory defense mechanisms, no change was observed in the plasma ergothioneine levels during the same observation period, indicating that the defense mechanisms may not be sufficiently reflected in the body. As ergothioneine is a natural ingredient that is absorbed mainly from the upper gastrointestinal tract, we hypothesized that oral ergothioneine may exert antidepressant effects. As expected, oral administration of ergothioneine prior to and during the SDS paradigm had a preventative effect on SDS-induced depressive behaviors, such as social avoidance and depression-like sleep abnormalities, particularly those of rapid eye movement sleep. These findings indicate that ergothioneine, a metabolite of L. reuteri, may be a common substance in the microbiota-gut-brain axis that prevents stress-induced sleep disturbances, especially those associated with depression.

neuroscience↗

bioRxiv2020

Chronic antidepressant treatments rescue reduced REM sleep theta power in a rat social defeat stress model of depression

Although It is widely recognized that virtually all antidepressants (ADs) suppress rapid eye movement (REM) sleep, the effects of chronic AD treatments on sleep abnormalities, especially those of REM sleep, have rarely been investigated comprehensively in animal models of major depressive disorder (MDD). Here, we show that chronic social defeat stress (SDS) in rats induces prolonged social avoidance and MDD-like alterations in sleep architecture (increased REM sleep durations, bouts, and shortened REM latency) even a month after the last SDS. These abnormalities were associated with changes in electroencephalography (EEG) spectra powers, such as reduced REM sleep theta powers during the light phase. Chronic AD treatments significantly ameliorated these behavioral, sleep, and EEG abnormalities, although in some cases not to control levels. Interestingly, the social interaction ratios a month after the last SDS most strongly correlated with the REM sleep theta powers. These results suggest that chronic AD treatments suppress REM sleep durations and bouts as observed in human MDD patients, but, at the same time, increase REM sleep theta power. The latter is an EEG parameter that has never been directly investigated in humans, and which may be responsible for the therapeutic effects of ADs. Significance StatementDisturbed sleep is one of nine diagnostic criteria for major depressive disorder (MDD), which usually resolves with adequate treatment. However, little is known about how antidepressants (AD) work in MDD animal models. Here, we developed a novel rat social defeat stress model demonstrating long-lasting MDD-like sleep disturbances. We found that chronic AD treatments suppressed REM durations and bouts as reported previously, but, at the same time, increased REM sleep theta power. Interestingly, among several sleep parameters, only REM sleep theta power strongly correlated with depressive symptoms at 1M. Thus, REM sleep theta power, an EEG parameter that has never been investigated directly in humans, could be a novel indicator for MDD and/or AD effects.

neuroscience↗