Automated cell detection for immediate early gene-expressing neurons using inhomogeneous background subtraction in fluorescent images.

Unlabelled: Although many methods for automated fluorescent-labeled cell detection have been proposed, not all of them assume a highly inhomogeneous background arising from complex biological structures. Here, we propose an automated cell detection algorithm that accounts for and subtracts the inhomogeneous background by avoiding high-intensity pixels in the blur filtering calculation. Cells were detected by intensity thresholding in the background-subtracted image, and the algorithm's performance was tested on NeuN- and c-Fos-stained images in the mouse prefrontal cortex and hippocampal dentate gyrus.

Extracting electromyographic signals from multi-channel LFPs using independent component analysis without direct muscular recording.

Electromyography (EMG) has been commonly used for the precise identification of animal behavior. However, it is often not recorded together with electrophysiology due to the need for additional surgeries and setups and the high risk of mechanical wire disconnection. While independent component analysis (ICA) has been used to reduce noise from field potential data, there has been no attempt to proactively use the removed "noise," of which EMG signals are thought to be one of the major sources.

Systems consolidation induces multiple memory engrams for a flexible recall strategy in observational fear memory in male mice.

Observers learn to fear the context in which they witnessed a demonstrator's aversive experience, called observational contextual fear conditioning (CFC). The neural mechanisms governing whether recall of the observational CFC memory occurs from the observer's own or from the demonstrator's point of view remain unclear. Here, we show in male mice that recent observational CFC memory is recalled in the observer's context only, but remote memory is recalled in both observer and demonstrator contexts.

Dissecting cell-type-specific pathways in medial entorhinal cortical-hippocampal network for episodic memory.

Episodic memory, which refers to our ability to encode and recall past events, is essential to our daily lives. Previous research has established that both the entorhinal cortex (EC) and hippocampus (HPC) play a crucial role in the formation and retrieval of episodic memories. However, to understand neural circuit mechanisms behind these processes, it has become necessary to monitor and manipulate the neural activity in a cell-type-specific manner with high temporal precision during memory formation, consolidation, and retrieval in the EC-HPC networks.

Hippocampal-amygdala memory circuits govern experience-dependent observational fear.

The empathic ability to vicariously experience the other's fearful situation, a process called observational fear (OF), is critical to survive in nature and function in society. OF can be facilitated by both prior similar fear experience in the observer and social familiarity with the demonstrator. However, the neural circuit mechanisms of experience-dependent OF (Exp OF) remain unknown.

Novel nose poke-based temporal discrimination tasks with concurrent in vivo calcium imaging in freely moving mice.

The hippocampus has been known to process temporal information as part of memory formation. While time cells have been observed in the hippocampus and medial entorhinal cortex, a number of the behavioral tasks used present potential confounds that may cause some contamination of time cell observations due to animal movement. Here, we report the development of a novel nose poke-based temporal discrimination task designed to be used with in vivo calcium imaging for the analysis of hippocampal time cells in freely moving mice.

A multichannel magnetic stimulation system using submillimeter-sized coils: system development and experimental application to rodent brain in vivo.

Objective: Single coil-based systems for magnetic stimulation are widely used for neurostimulation in neuroscience research and clinical treatment of neurological diseases. However, parallelization of magnetic stimulation with multiple coils may generate far greater potential than a single coil, and could thus expand the scope of brain area stimulation. Therefore, we examined whether a multiple coil-based system could improve the effectiveness and focality of conventional single coil-based magnetic stimulation.

Hybrid Microdrive System with Recoverable Opto-Silicon Probe and Tetrode for Dual-Site High Density Recording in Freely Moving Mice.

Multi-regional neural recordings can provide crucial information to understanding fine-timescale interactions between multiple brain regions. However, conventional microdrive designs often only allow use of one type of electrode to record from single or multiple regions, limiting the yield of single-unit or depth profile recordings. It also often limits the ability to combine electrode recordings with optogenetic tools to target pathway and/or cell type specific activity.

Micro-coil-induced Inhomogeneous Electric Field Produces sound-driven-like Neural Responses in Microcircuits of the Mouse Auditory Cortex In Vivo.

Magnetic stimulation is widely used in neuroscience research and clinical treatment. Despite recent progress in understanding the neural modulation mechanism of conventional magnetic stimulation methods, the physiological mechanism at the cortical microcircuit level is not well understood due to the poor stimulation focality and large electric artifact in the recording. To overcome these issues, we used a sub-millimeter-sized coil (micro-coil) to stimulate the mouse auditory cortex in vivo.

Micromagnetic Stimulation of the Mouse Auditory Cortex In Vivo Using an Implantable Solenoid System.

Objective: Recent studies have reported that micromagnetic stimulation ( MS), which can activate neurons and neural networks via submillimeter inductors, may address several limitations of conventional magnetic stimulation methods. Previous studies have examined the effects of MS on single neurons, yet little is known about how MS can affect brain tissue including local neural networks. Here, we propose a new, readily available implantable MS system and computationally and experimentally evaluate its validity.

Flavoprotein fluorescence imaging-based electrode implantation for subfield-targeted chronic recording in the mouse auditory cortex.

Background: Chronic neural recording in freely moving animals is important for understanding neural activities of cortical neurons associated with various behavioral contexts. In small animals such as mice, it has been difficult to implant recording electrodes into exact locations according to stereotactic coordinates, skull geometry, or the shape of blood vessels. The main reason for this difficulty is large individual differences in the exact location of the targeted brain area.

Salicylate-induced frequency-map reorganization in four subfields of the mouse auditory cortex.

Salicylate is the active ingredient in aspirin, and in high-doses it is used as an experimental tool to induce transient hearing loss, tinnitus, and hyperacusis. These salicylate-induced perceptual disturbances are associated with tonotopic-map reorganization and neural activity modulation, and such neural correlates have been examined in the central auditory pathway, including the auditory cortex (AC). Although previous studies have reported that salicylate induces increases in noise-burst-evoked neural responses and reorganization of tonotopic maps in the primary AC, little is known about the effects of salicylate on other frequency-organized AC subfields such as the anterior auditory, secondary auditory, and dorsomedial fields.

Transcranial flavoprotein-autofluorescence imaging of sound-evoked responses in the mouse auditory cortex under three types of anesthesia.

The effects of anesthesia on the functional auditory characteristics of cortical neurons, such as spatial and temporal response properties, vary between an anesthetized and an awake subject. However, studies have shown that an appropriate anesthetic method that approaches the awake condition is still useful because of its greater stability and controllability. The present study compared neural response properties from two core fields of the mouse auditory cortex under three anesthetic conditions: urethane; ketamine and xylazine hydrochloride (KX) mixture; and a combination of medetomidine, midazolam, and butorphanol (MMB).

Neural response differences in the rat primary auditory cortex under anesthesia with ketamine versus the mixture of medetomidine, midazolam and butorphanol.

Anesthesia affects central auditory processing. However, it is unclear to what extent the choice of anesthetic agent affects neural responses to sound stimulation. A mixture of three anesthetics (medetomidine, midazolam and butorphanol; MMB) was recently developed as an alternative to ketamine owing to the latter's addictive potential, yet the effect of this combination of anesthetics on neural responses is not known.

A rapid optical clearing protocol using 2,2'-thiodiethanol for microscopic observation of fixed mouse brain.

Elucidation of neural circuit functions requires visualization of the fine structure of neurons in the inner regions of thick brain specimens. However, the tissue penetration depth of laser scanning microscopy is limited by light scattering and/or absorption by the tissue. Recently, several optical clearing reagents have been proposed for visualization in fixed specimens.