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Papers by Ryosuke O Tachibana

The Journal of Neuroscience, 2022

Motor skills learned through practice are consolidated at later time, which can include nighttime... more Motor skills learned through practice are consolidated at later time, which can include nighttime, but the time course of motor memory consolidation and its underlying mechanisms remain poorly understood. We investigated neural substrates underlying motor memory consolidation of learned changes in birdsong, a tractable model system for studying neural basis of motor skill learning. Previous studies in male zebra finches and Bengalese finches have demonstrated that adaptive changes in adult song structure learned through a reinforcement paradigm are initially driven by a cortical-basal ganglia circuit, and subsequently consolidated into downstream cortical motor circuitry. However, the time course of the consolidation process, including whether it occurs offline during nighttime or online during daytime, remains unclear and even controversial. Here, we provide in both species experimental evidence of virtually no consolidation of learned vocal changes during nighttime. We demonstrate...

Dataset for USVSEG performance test

PLOS Computational Biology, 2021

Context dependency is a key feature in sequential structures of human language, which requires re... more Context dependency is a key feature in sequential structures of human language, which requires reference between words far apart in the produced sequence. Assessing how long the past context has an effect on the current status provides crucial information to understand the mechanism for complex sequential behaviors. Birdsongs serve as a representative model for studying the context dependency in sequential signals produced by non-human animals, while previous reports were upper-bounded by methodological limitations. Here, we newly estimated the context dependency in birdsongs in a more scalable way using a modern neural-network-based language model whose accessible context length is sufficiently long. The detected context dependency was beyond the order of traditional Markovian models of birdsong, but was consistent with previous experimental investigations. We also studied the relation between the assumed/auto-detected vocabulary size of birdsong (i.e., fine- vs. coarse-grained syl...

Scientific Programming, 2014

Scientific Programming, 2006

IBRO Reports, 2019

As we ascent to high altitude, partial pressure of oxygen reduces, causing insufficient supply of... more As we ascent to high altitude, partial pressure of oxygen reduces, causing insufficient supply of oxygen from air to body tissues which leads to oxidative stress and this reduces the availability of oxygen to different body parts. This pathophysiological condition is known as hypobaric hypoxia. Brain is predominantly susceptible to oxidative stress during hypobaric hypoxia, and therefore undergoes neurodegeneration due to energy crisis predominantly in hippocampus which causes memory dysfunction is reported in neurodegenerative disorders in humans but the mechanism is still unknown. Hypobaric hypoxia is an interest for researchers because the accidents occur with military personnel, mountain rescue teams and aviators since its neurological effects impair their mental performance. The present study is to delineate the mechanistic pathway involved in hypobaric hypoxia causing neuronal loss and neuroinflammation in male Balb/C mice. The work done so far involves behavioral assessment to check the cognitive deficits in mice after exposing them to hypobaric hypoxia. The behavioral test involves passive avoidance task test to see the cognitive impairment. The histo-pathological analysis of mice brain using Hematoxylin & Eosin staining has been done to observe the morphological changes occur in hippocampus region after exposing them to hypobaric hypoxia. Further the molecular interactions involved with hypoxia inducible factors will be evaluated to delineate the mechanism involved in pathogenesis of hypobaric hypoxia. So far the data depicts the neurodegenerative effects of hypobaric hypoxia in Balb/c mice. Further work is in progress to validate the results.

Scientific Reports

Initiation and execution of complex learned vocalizations such as human speech and birdsong depen... more Initiation and execution of complex learned vocalizations such as human speech and birdsong depend on multiple brain circuits. In songbirds, neurons in the motor cortices and basal ganglia circuitry exhibit preparatory activity before initiation of song, and that activity is thought to play an important role in successful song performance. However, it remains unknown where a start signal for song is represented in the brain and how such a signal would lead to appropriate vocal initiation. To test whether neurons in the midbrain ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) show activity related to song initiation, we carried out extracellular recordings of VTA/SNc single units in singing juvenile male zebra finches. We found that a subset of VTA/SNc units exhibit phasic activity precisely time-locked to the onset of the song bout, and that the activity occurred specifically at the beginning of song. These findings suggest that phasic activity in the VTA/SNc r...

Japanese Journal of Animal Psychology

Song learning of songbirds provides us a unique opportunity to study detailed mechanisms for voca... more Song learning of songbirds provides us a unique opportunity to study detailed mechanisms for vocal learning in various species, including humans. Recent studies in the behavioral neuroscience field have shown accumulated evidence indicating that their song learning is based on reinforcement via the auditory feedback of their own voice. The present review introduces an experimental paradigm that can elicit additional learning in bird's songs as a response to perturbations in the auditory feedback with noise presentation. This paradigm, named the noise-avoidance (NA) experiment, is quite useful for understanding the mechanism for song learning. Here I summarize findings obtained from the NA experiments, and review the current understanding of behavioral and neuroscientific mechanisms for feedback-based vocal learning. Additionally, I discuss computational aspects of the NA behavior in light of the reinforcement learning framework, and how the NA paradigm can be associated with the operant conditioning.

Trends in Cognitive Sciences

Frontiers in Neuroscience

Our motor system uses sensory feedback to keep behavioral performance in desired status. From thi... more Our motor system uses sensory feedback to keep behavioral performance in desired status. From this view, motor fluctuation is not simply ‘noise’ inevitably caused in the nervous system, but should provide a role in generating variations to explore better outcomes via their sensory feedback. Vocal control system offers a good model to investigate such adaptive sensory-motor interactions. The pitch, or fundamental frequency (FF), of voice is adaptively regulated by hearing its auditory feedback to compensate FF deviations. Animal studies, particularly for songbirds, have demonstrated that the variability in vocal features contributes to the adaptive control, although the same issue in human vocalizations has remained unclear. Here, we tested whether and how the motor variability contributes to adaptive control of vocal FF in humans. We measured the amount of compensatory vocal responses against FF shifts in the auditory feedback, and quantified the motor variability as amplitudes of s...

The meter is one of the core features of music perception, which is the cognitive grouping of reg... more The meter is one of the core features of music perception, which is the cognitive grouping of regular sound sequences, typically for every 2, 3, or 4 beats. Previous studies have suggested that we can not only passively perceive the meter from acoustic cues such as loudness, pitch, and duration of sound elements, but also actively perceive it by controlling own attention to isochronous sound events without any acoustic cues. Studying the interaction of top-down and bottom-up processing in meter perception leads to understanding our cognitive system for perceiving the entire structure of music. The present study demonstrated that the meter perception requires the top-down process which maintains and switches attention to the cues as well as the bottom-up process for discriminating acoustic cues. For this aim, we newly created a sound stimulus consisted of successive tone sequences that was designed to provide cues for either the triple or quadruple meter by differentiating two sound ...

The production of grammatically and semantically appropriate human language requires reference to... more The production of grammatically and semantically appropriate human language requires reference to non-trivially long history of past utterance, which is referred to as the context dependency of human language. Similarly, it is of particular interest to biologists how much effect past behavioral records of individual animals have on their future behavioral decisions. In particular, birdsong serves a representative case to study context dependency in sequential signals produced by animals. Previous studies have suggested that the songs of Bengalese finches (Lonchura striata var. domestica) exhibited a long dependency on previous outputs, while their estimates were upper-bounded by methodological limitations at that time. This study newly estimated the context dependency in Bengalese finch’s song in a more scalable manner using a neural network-based language model, Transformer, whose accessible context length reaches 900 tokens and is thus nearly free from model limitations, unlike th...

PLOS ONE

Rodents' ultrasonic vocalizations (USVs) provide useful information for assessing their social be... more Rodents' ultrasonic vocalizations (USVs) provide useful information for assessing their social behaviors. Despite previous efforts in classifying subcategories of time-frequency patterns of USV syllables to study their functional relevance, methods for detecting vocal elements from continuously recorded data have remained sub-optimal. Here, we propose a novel procedure for detecting USV segments in continuous sound data containing background noise recorded during the observation of social behavior. The proposed procedure utilizes a stable version of the sound spectrogram and additional signal processing for better separation of vocal signals by reducing the variation of the background noise. Our procedure also provides precise time tracking of spectral peaks within each syllable. We demonstrated that this procedure can be applied to a variety of USVs obtained from several rodent species. Performance tests showed this method had greater accuracy in detecting USV syllables than conventional detection methods.