Repository Collection: null

The hippocampal CA3 area implements sequence learning of discontinuous episodes

2026-08-21T00:10:20Z

Title: The hippocampal CA3 area implements sequence learning of discontinuous episodes Author(s): Eom, Kisang; Kim, Yujin; Lee, Hyoung-Ro; Lee, Yolguk; Han, Young-Eun; Shin, Jiwoo; Lee, Jae Sung; Hyun, Jung Ho; Park, Alan J.; Lee, Suk-Ho Abstract: Sequence learning requires linking memories of adjacent events by sharing ensemble cells. It remains unclear how the hippocampal CA3 links non-overlapping memory representations in sequence learning. High frequency mossy fiber inputs to a CA3 pyramidal cell downregulate Kv1.2 in distal apical dendrites to enhance its voltage response to perforant pathway inputs, and the high excitability is restored by subsequent perforant pathway inputs. Consistent with this notion, we found that CA3 ensemble cells activated by a novel context display high excitability, and their high excitability state is restored by re-activation during the second visit to a similar but distinct context. Computational modeling suggests that this bi-directional excitability regulation enables ordered association of orthogonal neuronal ensembles representing sequential events. Supporting this, CA3-specific Kcna2 + /- mice, which lack synaptic regulation of excitability, exhibited impaired sequence learning. These findings reveal the synaptic mechanisms by which the CA3 network encodes sequential memories.

Ultrasound localization microscopy lite (ULM lite): ultrasound localization microscopy with resource-efficient signal processing scheme

2026-02-18T13:40:10Z

Title: Ultrasound localization microscopy lite (ULM lite): ultrasound localization microscopy with resource-efficient signal processing scheme Author(s): Seong, Hyojin; Jung, Jinhwan; Jung, Dongkyu; Guezzi, Nizar; Nam, Sangwoo; Lee, Sangheon; Noman, Muhammad; Her, Taehoon; Cho, Eungyeong; Yoon, Heechul; Lee, Taeyoung; Hyun, Jung Ho; Yu, Jaesok Abstract: Ultrasound localization microscopy (ULM) is a groundbreaking, non-invasive imaging tool for monitoring vascular hemodynamics and neuronal activities in rodent models with exceptional spatial resolution. Despite its potential, the extensive data size required by the current ULM framework poses significant limitations to its broader applications. This study addresses these challenges by introducing sub-Nyquist sampling of the bandlimited radio-frequency (RF) signals, a method designed to reduce resource demands while preserving image quality. In this study, we experimentally demonstrate the in vivo feasibility of the proposed method. Our results show that 67 % of band-limited signal images achieve a high signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), comparable to those of conventional 200 % bandwidth signals. Even under stringent data reduction conditions, the proposed approach reduces the data size by approximately one-third without compromising image quality. These results highlight the potential of the proposed approach holds significant promise for enhancing the efficiency and practicality of ULM, facilitating the non-invasive visualization of deep neuronal activities with improved resource efficiency.

High-frequency (> 65 MHz) broadband transparent transducer with ultrathin gold electrode for dual-mode photoacoustic and laser-induced ultrasound microscopy

2025-08-19T05:40:11Z

Title: High-frequency (> 65 MHz) broadband transparent transducer with ultrathin gold electrode for dual-mode photoacoustic and laser-induced ultrasound microscopy Author(s): Park, Sunghun; Hong, Woongki; Park, Hyeongyu; Lee, Eunji; Nam, Sangwoo; Jung, Jin Hwan; Hyun, Jung Ho; Yu, Jaesok; Kang, Hongki; Chang, Jin Ho Abstract: For high-performance combined photoacoustic (PA) and Ultrasound (US) microscopy, precise coaxial alignment of the US and laser beams is essential. This can be realized using broadband transparent ultrasound transducers (TUTs). However, the current dual-mode imaging systems encounter significant challenges in simultaneous PA and US data acquisition due to sequential transmission of light and ultrasound and mechanical movement of dual-mode probes, leading to longer acquisition times and potential registration inaccuracies. To overcome these limitations, we propose a recently developed high-frequency broadband TUT with an ultrathin (< 10 nm) gold electrode, achieving a center frequency of 65.6 MHz and a –6 dB bandwidth of 71.6 %. The ultrathin gold electrode facilitates laser-induced ultrasound (LUS), enabling simultaneous acquisition of PA and US images. In vivo experiments demonstrate that LUS imaging can effectively replace conventional US imaging, offering highly efficient dual-mode PA/US imaging with minimized registration errors.

Engram and behavior: How memory is stored in the brain

2025-07-25T03:28:24Z

Title: Engram and behavior: How memory is stored in the brain Author(s): Eom, Kisang; Kim, Donguk; Hyun, Jung Ho Abstract: During the processing of information in humans, activated neurons behave in a specific way. The activity of these neurons leaves traces on the neurons, such as changes in synaptic or intrinsic properties. Formation of the memory traces is associated with molecular changes in the neurons. Hence, monitoring collective neural activities and following the trace of neural activities are important to neuroscience research. This collective or group of neurons is described as a 'neural ensemble', while the neural trace is described as a 'neural engram'. Both terms have been used and studied by neuroscientists for a long time. In this article, we discuss the development of these concepts, current research methods, and future areas of development.

Repository Collection: null

The hippocampal CA3 area implements sequence learning of discontinuous episodes

Ultrasound localization microscopy lite (ULM lite): ultrasound localization microscopy with resource-efficient signal processing scheme

High-frequency (> 65 MHz) broadband transparent transducer with ultrathin gold electrode for dual-mode photoacoustic and laser-induced ultrasound microscopy

Engram and behavior: How memory is stored in the brain

High-frequency (> 65 MHz) broadband transparent transducer with ultrathin gold electrode for dual-mode photoacoustic and laser-induced ultrasound microscopy