CMOS-based bio-image sensor spatially resolves neural activity-dependent proton dynamics in the living brain

Hiroshi Horiuchi,Dennis Lawrence Cheung,Masakazu Agetsuma,Junko Ishida,Junichi Nabekura,Shin Nanasaki,Tatsuya Iwata,Yusuke Nakamura,Yasuyuki Kimura,Kazuaki Sawada,Kazuhiro Takahashi

doi:10.1038/s41467-020-14571-y

Abstract

Recent studies have shown that protons can function as neurotransmitters in cultured neurons. To further investigate regional and neural activity-dependent proton dynamics in the brain, the development of a device with both wide-area detectability and high spatial-ltemporal resolution is necessary. Therefore, we develop an image sensor with a high spatial-temporal resolution specifically designed for measuring protons in vivo. Here, we demonstrate that spatially deferent neural stimulation by visual stimulation induced distinct patterns of proton changes in the visual cortex. This result indicates that our biosensor can detect micrometer and millisecond scale changes of protons across a wide area. Our study demonstrates that a CMOS-based proton image sensor with high spatial and temporal precision can be used to detect pH changes associated with biological events. We believe that our sensor may have broad applicability in future biological studies.

Highlights

1, Yusuke Nakamura[3, 3], Tatsuya Iwata 3, Kazuhiro Takahashi[3], Recent studies have shown that protons can function as neurotransmitters in cultured neurons
We demonstrate that our proton image sensor can make sensitive and accurate pH measurements at a high spatial–temporal resolution and subsequently use it to measure localized pH changes in the brains of live mice, in the primary visual cortex (V1) area, while they undergo a visual experience task
These inter-pixel variations were relatively small when compared to the value (SD = 0.027) shown in the previous report[8]. These results suggest that our sensor has low inter-pixel variation. These results suggest that the modifications incorporated into our present proton image sensor had no adverse impact on functionality, compared to our previous pH sensor[7]

Summary

Introduction

1, Yusuke Nakamura[3, 3], Tatsuya Iwata 3, Kazuhiro Takahashi[3], Recent studies have shown that protons can function as neurotransmitters in cultured neurons. While the homeostatic importance of pH regulation has long been appreciated, more recent studies have shown that protons can directly participate in neurotransmission[2] This suggests an added dimension in terms of the relevance of pH changes to brain function under both physiological and pathological conditions[3]. The spatial and temporal resolutions of MRI are limited to ~4 mm and ~6 s6, respectively, which are too broad to study pH changes relevant to neurotransmission as these changes occur at spatial and temporal scales of micrometers and milliseconds To overcome these limitations, we develop a special proton image sensor device that is based on our previous 128 × 128 pixel CMOS-based proton image sensor[7], but optimized for in vivo brain analyses. Because we are able to measure pH changes at micrometer and millisecond scales of resolution, we are able to correlate distinct spatial patterns of pH changes in the V1 with different visual stimulus patterns, suggesting that our device may be useful in gaining a deeper insight into the relationship between pH changes and computation in neural circuits

Methods

Results

Conclusion