Rik Lodevicus Elizabeth Maria Ubaghs

Killer whales, humpback whales, fin whales, and sperm whales converged in a fjord system in Northern Norway during the 2023–2024 winter, where whale watching and fishing vessels add to the acoustic scene. Cetaceans are intensely studied for their acoustic behaviour and communication, and the co-occurrence of four species in confined waters offers a unique opportunity to record them with hydrophone arrays. We present WhaleSonic, a raw acoustic dataset recorded with two synchronised array systems. Four drifting buoys, each carrying a tetrahedral hydrophone array, captured 78 hours of calibrated recordings; seven bottom-mounted hydrophones yielded 52 days of continuous data. Both systems are synchronised to UTC ( < 1 μs and 3–7 ms) and positioned to 2 m accuracy. Transmission experiments and sound velocity measurements provide in-situ ground truth. All data are in physical units and a unified coordinate system, self-documented in HDF5 files, and published with open-source tools. WhaleSonic supports the development of multichannel algorithms for source separation, localisation, sound field analysis, and group communication in free-ranging cetaceans.

Functional magnetic resonance imaging (fMRI) based on the blood-oxygen-level-dependent (BOLD) signal is widely used to study brain activity non-invasively. However, the relationship between the local neural population activity and vascular activity, as measured by BOLD fMRI, remains incompletely understood. Here we show that simultaneous measurement of cellular calcium (Ca ²⁺ ) activity and whole-brain BOLD fMRI in awake mice can reveal spatially specific relationships between neurons and the surrounding vasculature. We introduce an MRI-compatible single-photon microscope that enables recordings from genetically defined neurons at cellular resolution during fMRI. Using this approach, we find that neurons located close to blood vessels often show a negative relationship with the local BOLD signal, whereas neurons farther away display a more variable, often positive relationship. We further demonstrate that local neural activity can be linked to BOLD responses across distributed, connected brain regions. Together, these results provide insight into how vascular organization shapes fMRI signals and establish a powerful tool for bridging cellular and whole-brain measurements of brain function.

Blood Oxygen Level-Dependent (BOLD) functional Magnetic Resonance Imaging (fMRI) allows for non-invasive, indirect recordings of neural activity across the whole brain in both humans and animals. However, the relationship between the local neural population activity and the vascular activity is not completely understood. To investigate this relationship, we present a novel MRI compatible single-photon microscope capable of measuring cellular resolution Ca ²⁺ activity of genetically defined neurons during whole-brain BOLD fMRI in awake behaving mice. Using this combined imaging approach, we found a difference in activity patterns between cells which was dependent on their location with respect to the vasculature. Notably, neurons near the vasculature showed pronounced negative activity during contralateral whisker movements at 3 Hz. In a second proof of concept experiment, we demonstrate the potential of recording both local neural activities, like those in the barrel field (SSp-bfd), and BOLD fMRI readings from interlinked brain regions. In sum, the presented technological advancement paves the way for studies examining the interplay between local brain circuits and overarching brain functions. In addition, the new approach enhances our understanding of the vascular BOLD fMRI signal, providing insights into the determinants of local neurovascular functions and the brain’s organizational framework across various scales.