Volitional activation of remote place representations with a hippocampal brain-machine interface.

The hippocampus is critical for recollecting and imagining experiences. This is believed to involve voluntarily drawing from hippocampal memory representations of people, events, and places, including maplike representations of familiar environments. However, whether representations in such "cognitive maps" can be volitionally accessed is unknown. We developed a brain-machine interface to test whether rats can do so by controlling their hippocampal activity in a flexible, goal-directed, and model-based manner. We found that rats can efficiently navigate or direct objects to arbitrary goal locations within a virtual reality arena solely by activating and sustaining appropriate hippocampal representations of remote places. This provides insight into the mechanisms underlying episodic memory recall, mental simulation and planning, and imagination and opens up possibilities for high-level neural prosthetics that use hippocampal representations.

Analysis of changes in the microbial community structure and physicochemical properties during the fermentation of sand crab juice.

The structure of the microbial community during sand crab juice fermentation was analyzed using culture-based methods and high-throughput 16S rRNA gene sequencing. Additionally, the changes in amino acid nitrogen (AAN) and total volatile basic nitrogen (TVB-N) were evaluated. Staphylococcus equorum, Staphylococcus arlettae, Staphylococcus saprophyticus, Salinicoccus amylolyticus and Bacillus cereus were isolated by traditional culture isolation technique. The Good's coverage obtained by high-throughput sequencing was over 99.5%, and the Chao1 and Simpson indices showed small fluctuations, indicating that the species abundance and diversity did not change significantly during the fermentation process, although the abundance decreased. Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria were the dominant bacterial phyla observed during fermentation, whereas Aquabacterium, Roseovarius, Muribaculaceae, and Silicimonas were the dominant bacterial genera. The AAN content increased from 0.15 to 0.43 g/100 mL during the 15-day fermentation, indicating the production of small peptides and amino acids during fermentation. The TVB-N content (25.2 mg/100 mL) on day 15 indicated slight spoilage of sand crab juice, although the freshness conformed to the production standard. These results provide a theoretical basis for improving the quality and optimizing the production process of sand crab juice.

Multimodal in vivo brain electrophysiology with integrated glass microelectrodes.

Electrophysiology is the most used approach for the collection of functional data in basic and translational neuroscience, but it is typically limited to either intracellular or extracellular recordings. The integration of multiple physiological modalities for the routine acquisition of multimodal data with microelectrodes could be useful for biomedical applications, yet this has been challenging owing to incompatibilities of fabrication methods. Here, we present a suite of glass pipettes with integrated microelectrodes for the simultaneous acquisition of multimodal intracellular and extracellular information in vivo, electrochemistry assessments, and optogenetic perturbations of neural activity. We used the integrated devices to acquire multimodal signals from the CA1 region of the hippocampus in mice and rats, and show that these data can serve as ground-truth validation for the performance of spike-sorting algorithms. The microdevices are applicable for basic and translational neurobiology, and for the development of next-generation brain-machine interfaces.

Disrupted Cortical State Regulation in a Rat Model of Fragile X Syndrome.

Children with Fragile X syndrome (FXS) have deficits of attention and arousal. To begin to identify the neural causes of these deficits, we examined juvenile rats lacking the Fragile X mental retardation protein (FMR-KO) for disruption of cortical activity related to attention and arousal. Specifically, we examined the switching of visual cortex between activated and inactivated states that normally occurs during movement and quiet rest, respectively. In both wild-type and FMR-KO rats, during the third and fourth postnatal weeks cortical activity during periods of movement was dominated by an activated state with prominent 18-52 Hz activity. However, during quiet rest, when activity in wild-type rats became dominated by the inactivated state (3-9 Hz activity), FMR-KO rat cortex abnormally remained activated, resulting in increased high-frequency and reduced low-frequency power during rest. Firing rate correlations revealed reduced synchronization in FMR-KO rats, particularly between fast-spiking interneurons, that developmentally precede cortical state defects. Together our data suggest that disrupted inhibitory connectivity impairs the ability of visual cortex to regulate exit from the activated state in a behaviorally appropriate manner, potentially contributing to disrupted attention and sensory processing observed in children with FXS by making it more difficult to decrease cortical drive by unattended stimuli.