Biology subjects

Chiken, S.

Publications and source records attributed to Chiken, S..

5 recordsLinked to original sources

bioRxiv2026

Left-right asymmetry of the microminipig brain.

Left-right asymmetry of the brain is well recognized in various animals including C. elegans, drosophila and zebrafish. In primates, most of the brain studies describe side of the brain. However, in spite of huge amounts of accumulating rodent studies on neuroscience, most of rodent studies do not distinguish the brain side. The pig brain is considered to occupy an intermediate position between primates and rodents in terms of structural complexity and brain function. Moreover, the numbers of studies using genetic manipulation of pigs are drastically increasing. So, we investigated microminipig (MMP) brain mesoscopic anatomy focusing on left-right differences of its morphology. Here, we show the anterior cingulate cortex, perirhinal cortex, and cerebellum of male and female MMPs, are structurally asymmetrical. The cerebellar vermis, paravermis is tilted from the midline and the consequently the cerebellar cortex exhibits asymmetrical morphology. The anterior cingulate gurus exhibited protrusion and invagination toward the midline on the right and left side, respectively. The left perirhinal lobe exhibited distinct patterns of cortical gyration between left and right side. These data demonstrate that MMPs are one of the suitable model animals for investigating cerebral and cerebellar asymmetry.

neuroscience↗

bioRxiv2024

Distinct roles of two thalamostriatal systems in learning processes of visual discrimination in common marmosets

The thalamostriatal projections arising from the intralaminar thalamic nuclei (ILN) constitute the principal source of input information to specified subregions of the striatum, a key structure of the cortico-basal ganglia circuitry. However, the roles of primate ILN in cortico-basal ganglia circuit functions remain unclear. Here, we performed immunotoxin-induced selective targeting of two representative structures of the ILN, the parafascicular nucleus (Pf) and centre median nucleus (CM) projecting to the caudate nucleus (Cd) and putamen (Pu), respectively, in common marmosets. Elimination of Pf-Cd neurons resulted in impaired reversal learning of a two-choice visual discrimination task, whereas removal of CM-Pu neurons disturbed the task acquisition. No marked impact of such manipulations was observed on either motor skill learning or spontaneous locomotor activity. Our findings reveal that the two thalamostriatal systems play distinct roles in the learning processes of external cue-dependent decision-making in nonhuman primates.

neuroscience↗

bioRxiv2021

Subthalamic nucleus stabilizes movements by reducing neural spike variability in monkey basal ganglia: chemogenetic study

AbstractsThe subthalamic nucleus (STN) projects to the external pallidum (GPe) and internal pallidum (GPi), the relay and output nuclei of the basal ganglia (BG), respectively, and plays an indispensable role in controlling voluntary movements. To elucidate the neural mechanism by which the STN controls GPe/GPi activity and movements, we utilized a chemogenetic method to reversibly suppress the motor subregion of the STN in three macaque monkeys (Macaca fuscata, both sexes) engaged in reaching tasks. Systemic administration of chemogenetic ligands prolonged movement time and increased spike train variability in the GPe/GPi, but only slightly affected firing rate modulations. Across-trial analyses revealed that the irregular discharge activity in the GPe/GPi coincided with prolonged movement time. STN suppression also induced excessive abnormal movements in the contralateral forelimbs, which was preceded by STN and GPe/GPi phasic activity changes. Our results suggest that the STN stabilizes spike trains in the BG and achieves stable movements.

neuroscience↗

bioRxiv2021

Transient response of basal ganglia network in healthy and low-dopamine state

The basal ganglia (BG) are crucial for a variety of motor and cognitive functions. Changes induced by persistent low-dopamine (e.g. in Parkinsons disease), result in aberrant changes in steady-state population activity ({beta}-band oscillations) and transient response of the BG. Typically, brief cortical stimulation results in a triphasic response in the substantia nigra pars reticulata (SNr, output of the BG). The properties of the triphasic responses are shaped by dopamine levels. While it is relatively well understood how changes in BG result in aberrant steady state activity, it is not clear which BG interactions are crucial for the aberrant transient responses in the BG. Moreover, it is also not clear whether the same or different mechanisms underlie the aberrant changes in steady-state activity and aberrant transient response. Here we used numerical simulations of a network model of BG to identify the key factors that determine the shape of the transient responses. We show that an aberrant transient response of the SNr in low-dopamine state, involves changes in both, the direct pathway and the recurrent interactions within the globus pallidus externa (GPe) and between GPe and sub-thalamic nucleus. We found that the connections from D2-type spiny projection neurons to GPe are most crucial in shaping the transient response and by restoring them to their healthy level, we could restore the shape of transient response even in low-dopamine state. Finally, we show that the changes in BG that result in aberrant transient response are also sufficient to generate pathological oscillatory activity. Significance statementTo understand how changes induced by low-dopamine (e.g. in Parkinsons disease, PD) affect basal ganglia (BG) function, we need to identify the factors that determine the shape of BG responses to brief cortical stimuli. We show that transient response of the BG is also affected by recurrent interactions within the subnuclei of the BG, and not just feedforward pathways. We found that input and local connectivity within the globus pallidus externa are crucial for shaping the transient response. We also show that the same network changes may underlie both, pathological {beta}-band oscillations and aberrant transient responses. Our results highlight the importance of the recurrent connectivity within the BG and provide a coherent view of emergence of pathological activity in PD.

neuroscience↗

bioRxiv2019

Forelimb movements evoked by optogenetic stimulation of the macaque motor cortex

Optogenetics has become an indispensable tool for investigating brain functions. Although non-human primates are particularly useful models for understanding the functions and dysfunctions of the human brain, application of optogenetics to non-human primates is still limited. In the present study, we generated an effective adeno-associated viral vector serotype DJ to express channelrhodopsin-2 (ChR2) under the control of a strong ubiquitous CAG promoter and injected into the somatotopically identified forelimb region of the primary motor cortex in macaque monkeys. ChR2 was strongly expressed around the injection sites, and optogenetic intracortical microstimulation (oICMS) through a homemade optrode induced prominent cortical activity: Even single-pulse, short duration oICMS evoked long-lasting repetitive firings of cortical neurons. In addition, oICMS elicited distinct forelimb movements and muscle activity, which were comparable to those elicited by conventional electrical ICMS. The present study removed obstacles to optogenetic manipulation of neuronal activity and behaviors in non-human primates.

neuroscience↗