Biology subjects

Koumura, T.

Publications and source records attributed to Koumura, T..

4 recordsLinked to original sources

bioRxiv2022

Human-like Modulation SensitivityEmerging through Optimization to Natural Sound Recognition

Natural sounds contain rich patterns of amplitude modulation (AM), which is one of the essential sound dimensions for hearing perception. The sensitivity of human hearing to AM measured by psychophysics takes diverse forms, from low-pass to high-pass, depending on the experimental conditions. Here, we address with a single framework the questions of why such patterns of AM sensitivity have emerged in the human auditory system and how they are realized by our neural mechanisms. Assuming that optimization for natural sound recognition has taken place during human evolution and development, we examined its effect on the formation of AM sensitivity by optimizing a computational model, specifically, a multi-layer (or deep) neural network, for natural sound recognition and simulating psychophysical experiments in which the models AM sensitivity was measured. Relatively higher layers in the optimized model exhibited qualitatively and quantitatively similar AM sensitivity to that of humans, even though the model was not designed to reproduce human-like AM sensitivity. The similarity of the models AM sensitivity to humans correlated with its sound recognition accuracy. Optimization of the model to degraded sounds revealed the necessity of natural AM patterns for the emergence of human-like AM sensitivity. Consistent results were observed from optimizations to two different types of natural sound. Moreover, simulated neurophysiological experiments on the same model revealed a correspondence between the model layers and the auditory brain regions that is based on the similarity of their neural AM tunings. The layers in which human-like psychophysical AM sensitivity emerged exhibited substantial neurophysiological similarity with the auditory midbrain and higher regions. These results suggest that the behavioral AM sensitivity of human hearing has emerged as a result of optimization for natural-sound recognition in the course of our evolution and/or development and that it is based on a stimulus representation encoded in the neural firing rates in the auditory midbrain and higher regions.

neuroscience↗

bioRxiv2019

Deep, soft, and dark sounds induce autonomous sensory meridian response

There has been a growing interest in the autonomous sensory meridian response (ASMR). The ASMR is characterized by a tingling sensation around the scalp and neck and often induces a feeling of relaxation and a reduction of a negative mood. However, it is still unknown what factors affect the ASMR. The present study focused on stimulus characteristics and individuals mood states and personality traits. Participants filled out self-reported questionnaires (the Profile of Mood States, Beck Depression Inventory, and Big Five Inventory) and reported ASMR estimates throughout a 17-min experiment while listening to binaural tapping and brushing sounds. Cross-correlation results showed that the ASMR estimates were strongly associated with the acoustic features of auditory stimuli, such as their amplitude, spectral centroid, and spectral bandwidth. This indicates that low-pitched sounds with dark timbre trigger the ASMR. The maximum ASMR was observed around 2 s after the acoustic features changed, suggesting that the sluggishness of multisensory integration may lead to the ASMR experience. In addition, individual differences in the ASMR experience were closely linked to participants mood states, such as anxiety, but not to their personality traits. Our results provide important clues to understand the mechanisms of auditory-somatosensory interactions. Significant StatementsThe autonomous sensory meridian response (ASMR) is characterized by a tingling, electrostatic-like sensation across the scalp and back of the neck. This phenomenon can be triggered by a variety of audiovisual stimuli, and many people seek out the ASMR via the internet to receive a feeling of relaxation and reduce a negative mood. We show that the ASMR is induced about 2 s after acoustic features, such as the amplitude, spectral centroid, and spectral bandwidth are changed. This suggests that low-pitched sounds with dark timbre lead to the ASMR experience. The stimulus-driven ASMR effect is found regardless of the personality traits or mood states of participants. Our findings provide a critical clue to understand the mechanisms of auditory-somatosensory interactions.

neuroscience↗

bioRxiv2019

Visual discrimination of optical material properties: a large-scale study

Complex visual processing involved in perceiving the object materials can be better elucidated by taking a variety of research approaches. Sharing stimulus and response data is an effective strategy to make the results of different studies directly comparable and can assist researchers with different backgrounds to jump into the field. Here, we constructed a database containing several sets of material images annotated with visual discrimination performance. We created the material images using physically-based computer graphics techniques and conducted psychophysical experiments with them in both laboratory and crowdsourcing settings. The observers task was to discriminate materials on one of six dimensions (gloss contrast, gloss distinctness-of-image, translucent vs. opaque, metal vs. plastic, metal vs. glass, and glossy vs. painted). The illumination consistency and object geometry were also varied. We used a non-verbal procedure (an oddity task) applicable for diverse use-cases such as cross-cultural, cross-species, clinical, or developmental studies. Results showed that the material discrimination depended on the illuminations and geometries and that the ability to discriminate the spatial consistency of specular highlights in glossiness perception showed larger individual differences than in other tasks. In addition, analysis of visual features showed that the parameters of higher-order color texture statistics can partially, but not completely, explain task performance. The results obtained through crowdsourcing were highly correlated with those obtained in the laboratory, suggesting that our database can be used even when the experimental conditions are not strictly controlled in the laboratory. Several projects using our dataset are underway.

neuroscience↗

bioRxiv2018

Cascaded Processing of Amplitude Modulation for Natural Sound Recognition

Temporal variation of sound envelope, or amplitude modulation (AM), is essential for auditory perception of natural sounds. Neural representation of stimulus AM is successively transformed while processed by a cascade of brain regions in the auditory system. Here we sought the functional significance of such cascaded transformation of AM representation. We modelled the function of the auditory system with a deep neural network (DNN) optimized for natural sound recognition. Neurophysiological analysis of the DNN revealed that AM representation similar to the auditory system emerged during the optimization. The better-recognizing DNNs exhibited larger similarity to the auditory system. The control experiments suggest that the cascading architecture, the data structure, and the optimization objective may be essential factors for the lower, middle and higher regions, respectively. The results were consistently observed across independent datasets. These results suggest the emergence of AM representation in the auditory system during optimization for natural sound recognition.

neuroscience↗