Biology subjects

Iriki, A.

Publications and source records attributed to Iriki, A..

5 recordsLinked to original sources

bioRxiv2024

Posture-dependent modulation of marmoset cortical motor maps detected via rapid multichannel epidural stimulation

In this study, rapid topographical changes were detected in the forelimb motor maps in the primary motor cortex (M1) of awake marmoset monkeys using our previously developed accurate short-time stimulation mapping procedure (Takemi et al. 2017; Kosugi et al. 2018). The results revealed that although the hotspot (the location in M1 that elicited a forelimb muscle twitch with the lowest stimulus intensity) remained constant across postures, the stimulus intensity required to elicit the forelimb muscle twitch in the perihotspot region and the size of motor representations were posture-dependent. Hindlimb posture was particularly effective in inducing these modulations. The angle of the body axis relative to the gravitational vertical line did not alter the motor maps. These results provide a proof of concept that a rapid stimulation mapping system with chronically implanted cortical electrodes can capture the dynamic regulation of forelimb motor maps in natural conditions. The flexible nature of the motor maps necessitates the reconsideration of the results of motor control and neuroplasticity studies. Neural mechanisms regulating forelimb muscle representations in M1 by the hindlimb sensorimotor state warrant further exploration.

neuroscience↗

bioRxiv2023

Development of a non-invasive novel individual marmoset holder for evaluation by awake functional magnetic resonance brain imaging

BackgroundAlthough functional MRI (fMRI) in awake marmosets (Callithrix jacchus) is fascinating for functional brain mapping and evaluation of brain disease models, it is difficult to launch awake fMRI on scanners with less than 15 cm of bore size. A universal marmoset holder for the small-bore size MRI was designed, and evaluated whether this holder could conduct auditory stimulation fMRI in the awake state. New MethodThe marmoset holder was designed with an outer diameter of 71.9 mm. A holder was designed to allow adjustment according to the individual head shape, enabling to use the holder universally. An awake fMRI study of auditory response was conducted to evaluate the practicality of the new holder. Whole-brain activation was investigated when marmosets heard the marmoset social communication "phee call," an artificial tone sound, music (bossa nova), and reversed of those. ResultsThe prefrontal cortex was significantly activated in response to phee calls, whereas only the auditory cortex was activated in response to pure tones. In response to bossa nova, the marmosets visual and auditory cortices were activated. In contrast, the auditory response was decreased when marmosets heard phee calls and bossa nova music played backward. Their stimulus-specific responses indicated they perceived and differentiated sound characteristics in the fMRI environment. Comparison with Existing MethodsA holder does not require surgical intervention or custom-made helmet to minimize head movement in small space. ConclusionOur newly developed holder made it possible to perform longitudinal fMRI experiments on multiple marmosets in a less invasive manner. HighlightO_LIWe designed a universal marmoset holder for the optimization of small-bore size MRI. We aimed to evaluate whether the data acquired by fMRI with this holder indicated that awake marmosets were likely to recognize sounds during fMRI and whether the brain activity shown as fMRI signals reflected the characteristics of each sound. C_LIO_LIAfter the acclimatization of the marmosets to the holder, an awake fMRI study was conducted to evaluate the practicality of the new holder and successfully acquired the auditory responses to the set of sound stimuli. C_LIO_LIOur newly developed holder does not require surgical intervention to minimize head movement, which allows for less invasive fMRI experiments and makes it easier to conduct longitudinal fMRI for multiple marmosets. C_LI

neuroscience↗

bioRxiv2021

Effects of enhanced insect feeding on the faecal microbiota and transcriptome of a family of captive common marmosets (Callithrix jacchus)

Common marmosets have been widely used in biomedical research for years. Nutritional control is an important factor in managing their health, and insect intake would be beneficial for that purpose because common marmosets frequently feed on insects in natural habitats. Here, we examined the effect of enhanced insect feeding on the gut by analysing the faecal microbiota and transcripts of captive marmosets. A family consisting of six marmosets was divided into two groups. During the seven-day intervention period, one group (the insect feeding group, or Group IF) was fed one cricket and one giant mealworm per marmoset per day, while the other (the control group, or Group C) was not fed these insects. RNA was extracted from faecal samples to evaluate the ecology and transcripts of the microbiota, which were then compared among time points before (Pre), immediately after (Post), and two weeks after intervention (After) by total RNA sequencing. The gut microbiota of marmosets showed Firmicutes, Actinobacteria, Bacteroidetes, and Proteobacteria as dominant phyla. Linear discriminant analysis showed differential characteristics of microbiota with and without insect feeding treatment. Further analysis of differentially expressed genes revealed increases and decreases in Bacteroidetes and Firmicutes, respectively, corresponding to the availability of insects under both Post and After conditions. Significant changes specific to insect feeding were also detected within the transcriptome, some of which were synchronized with the fluctuations in the microbiota, suggesting a functional correlation or interaction between the two. The rapid changes in the microbiota and transcripts may be deeply connected to the original microbiota community shaped by marmoset feeding ecology in the wild. The results were informative for identifying the physiological impact of insect feeding to produce a better food regimen and for detecting transcripts that are currently unidentifiable.

physiology↗

bioRxiv2018

A High-throughput Neurohistological Pipeline for Brain-Wide Mesoscale Connectivity Mapping of the Common Marmoset

Understanding the connectivity architecture of entire vertebrate brains is a fundamental but difficult task. MRI based methods offer whole brain coverage, but remain indirect in the approach to connectivity mapping. Recent progress has been made in directly mapping whole-brain connectivity architecture in the mouse at the mesoscopic scale. The basic approach uses tracer injections systematically placed on a grid of locations spanning the brain and computational analysis of the resulting whole brain data sets. Scaling this approach to bigger primate brains poses nontrivial technical challenges. Here we present an integrated neurohistological pipeline as well as a grid-based tracer injection strategy for systematic mesoscale connectivity mapping in the common Marmoset (Callithrix jacchus). Individual brains are sectioned into [~]1700 20{micro}m sections using the tape transfer technique, permitting high quality 3D reconstruction of a series of histochemical stains (Nissl, myelin) interleaved with tracer labelled sections. Combining the resulting 3D volumes, containing informative cytoarchitectonic markers, with in-vivo and ex-vivo MRI, and using an integrated computational pipeline, we are able to overcome the significant individual variation exhibited by Marmosets to obtain routine and high quality maps to a common atlas framework. This will facilitate the systematic assembly of a mesoscale connectivity matrix together with unprecedented 3D reconstructions of brain-wide projection patterns in a primate brain. While component instruments or protocols may be available from previous work, we believe that this is the first detailed systems-level presentation of the methodology required for high-throughput neuroanatomy in a model primate.

neuroscience↗

bioRxiv2017

The Brain/MINDS 3D digital marmoset brain atlas

We present a new 3D digital brain atlas of the non-human primate, common marmoset monkey (Callithrix jacchus), with MRI and coregistered Nissl histology data. To the best of our knowledge this is the first comprehensive digital 3D brain atlas of the common marmoset having normalized multi-modal data, cortical and sub-cortical segmentation, and in a common file format (NIfTI). The atlas can be registered to new data, is useful for connectomics, functional studies, simulation and as a reference.\n\nThe atlas was based on previously published work but we provide several critical improvements to make this release valuable for researchers. Nissl histology images were processed to remove illumination and shape artifacts and then normalized to the MRI data. Brain region segmentation is provided for both hemispheres. The data is in the NIfTI format making it easy to integrate into neuroscience pipelines, whereas the previous atlas was in an inaccessible file format. We also provide cortical, mid-cortical and white matter boundary segmentations useful for visualization and analysis.

neuroscience↗