Biology subjects

Michikawa, T.

Publications and source records attributed to Michikawa, T..

3 recordsLinked to original sources

bioRxiv2025

Volitional and forced running ability in mice lacking intact primary motor cortex

The coordination of various brain regions achieves both volitional and forced motor control, but the role of the primary motor cortex in proficient running motor control remains unclear. This study trained mice to run at high performance (>10,000 rotations per day or >2,700 rotations per hour) using a running wheel, and then assessed the effects of the removal of bilateral cortical areas including the primary motor cortex on volitional and forced running locomotion. The control sham-operated group revealed a quick recovery of volitional running, reaching half of the maximum daily rotation in 3.9 +/-2.6 days (n = 10). In contrast, the cortical injury group took significantly a longer period (7.0 +/-3.3 days, n = 15) to reach half of the maximum volitional daily rotation, but recovered to preoperative levels in about two weeks. Furthermore, even 3 days after surgery to remove cortical regions, the running time on a treadmill moving at 35.3 cm/sec, which is difficult for naive mice to run on, was not significantly different from that in the sham-operated group. These results suggest that the intact primary motor cortex is not necessarily required to execute trained fast-running locomotion, but rather contributes to the spontaneity of running in mice.

neuroscience↗

bioRxiv2021

A spike-sorting method based on hierarchical clustering to discriminate extracellularly recorded simple spikes and complex spikes from cerebellar Purkinje cells

BackgroundIn the cerebellar cortex, Purkinje cells are the only output neurons and exhibit two types of discharge. Most Purkinje cell discharges are simple spikes, which are commonly appearing action potentials exhibiting a rich variety of firing patterns with a rate of up to 400 Hz. More infrequent discharges are complex spikes, which consist of a short burst of impulses accompanied by a massive increase in dendritic Ca2+ with a firing rate of around 1 Hz. The discrimination of these spikes in extracellular single-unit recordings is not always straightforward, as their waveforms vary depending on recording conditions and intrinsic fluctuations. New MethodTo discriminate complex spikes from simple spikes in the extracellular single-unit data, we developed a semiautomatic spike-sorting method based on divisive hierarchical clustering. ResultsQuantitative evaluation using parallel in vivo two-photon Ca2+ imaging of Purkinje cell dendrites indicated that 96.6% of the complex spikes were detected using our spike-sorting method from extracellular single-unit recordings obtained from anesthetized mice. Comparison with Existing Method(s)No reports have conducted a quantitative evaluation of spike-sorting algorithms used for the classification of extracellular spikes recorded from cerebellar Purkinje cells. ConclusionsOur method could be expected to contribute to research in information processing in the cerebellar cortex and the development of a fully automatic spike-sorting algorithm by providing ground-truth data useful for deep learning. HighlightsO_LIA spike-sorting algorithm on hierarchical clustering was developed. C_LIO_LIIt was applied to extracellular recordings from cerebellar Purkinje cells. C_LIO_LIComplex and simple spikes were discriminated based on their waveforms. C_LIO_LISpike-sorting performance was quantified using in vivo Ca2+ imaging data. C_LIO_LIThe algorithm isolated over 96.6% of complex spikes. C_LI

neuroscience↗

bioRxiv2020

Distributed sensory coding by cerebellar complex spikes in units of cortical segments

Sensory processing is essential for motor control. Climbing fibers from the inferior olive transmit sensory signals to Purkinje cells, but how the signals are represented in the cerebellar cortex remains elusive. We examined the olivocerebellar organization of the mouse brain by optically measuring complex spikes (CSs) evoked by climbing fiber inputs over the entire dorsal surface of the cerebellum. We discovered that the surface was divided into approximately 200 segments each composed of [~]100 Purkinje cells that fired CSs synchronously. Our in vivo imaging of evoked responses revealed that whereas stimulation of four limb muscles individually similar global CS responses across nearly all segments, the timing and location of a stimulus were derived by Bayesian inference from coordinated activation and inactivation of multiple segments on a single trial basis. Our findings suggest that the cerebellum performs segment-based distributed population coding by assembling probabilistic sensory representation in individual segments.

neuroscience↗