Research

My current research at Portugues lab @TUM focuses on understanding the circuit mechanisms of cognitive processes using the larval zebrafish as a model system. The larval zebrafish is one of the smallest vertebrate model organisms used in neuroscience. Their small size, optical transparency, and genetic tractability make them amenable to diverse cutting-edge experimental approaches such as whole-brain calcium imaging with light-sheet microscopy, genetic manipulation of specific circuit elements, electronmicrograph-based circuit reconstruction, as well as behavioral experiments in immersive virtual reality settings. While the brain of these baby fish is tiny, it has a direct homology to our brains. I believe that obtaining a detailed, mechanistic understanding of how the fish brain works is a promissing avenue for the better understanding of our own minds.

Prior to arriving at Germany, I conducted my PhD research at Clark lab @Yale. My PhD research focused on understanding visual processing in fruit fly Drosophila, with a special emphasis on bridging sensory ecology to circuit mechanisms. Specifically, I studied how flies detect visual motion and objects (e. g. conspecifics) by combining behavioral experiments, two-photon imaging, optogenetics, computational modeling, and connectomic analyses. Before starting my PhD, I was engaged in psychophysical and neuroimaging studies of human subjects at Yotsumoto lab @UTokyo, covering topics such as visual illusions and perception of time.

You can find my Google Scholar profile here.

Publications

Fish works

• Comming Soon
• Hopefully!

Fly works

• Tanaka, Zhou, Agrochao, Badwan, Au, Matos, & Clark (2023) Neural mechanisms to incorporate visual counterevidence in self-movement estimation. Curr. Biol.. [link] [preprint]
• Have you ever had an experience where you confused the movement of a train on another track as yours? This paper studied how flies minimize this type of confusion between self- and world-motion. A useful heuristic cue to distinguish motion out in the world and your own movement are stationary visual patterns, because nothing can remain stationary when you yourself is moving (or rotating to be preceise). Here, we found that flies actually interprets visual motion as "world-motion" in the presence of stationary visual patterns, which can be seen as a very basic form of falsification logic.
• Mano, Choi, Tanaka, Creamer, Matos, Shomar, Badwan, Clandinin, & Clark (2023) Long timescale anti-directional rotation in Drosophila optomotor behavior. eLife. [link]
• When presented with wide-field visual motion sideways, animals ranging from humble insects to humans just cannot help following it, a reflex termed optomotor (or optokinetic) response. This behavior functions to stabilize the heading and the gaze, and has been intensively studied for almost a century, ever since the dawn of modern vision science/opthalamology. But sometimes they do the opposite! This study identified when and how this paradoxical "antioptomotor" response happens in fruit flies. Ryosuke contributed a part of LPTC calcium imaging data.
• Tanaka & Clark (2022) Neural mechanisms to exploit positional geometry for collision avoidance. Curr. Biol. [link] [preprint]
• In this paper, we studied how walking flies avoid collision with objects like other flies. There is a geometrical rule that any agent crossing in front of you (e. g. a car merging into your lane) appear to be moving in the back-to-front direction on your retina. We found that a specific visual neuron type in the fly brain called LPLC1 detects these kinds of objects by combining output of motion and object detectors, and its activity causes the fly to stop, which prevents collisions.
• Tanaka & Clark (2022) Identifying inputs to visual projection neurons in Drosophila lobula by analyzing connectomic data. eNeuro. [link] [preprint]
• The release of the "hemibrain" connectome by Janelia Reseach Campus in January 2020 was a big game-changer in the field of fly neuroscience. However, unfortunately for vision researchers like myself, the hemibrain connectome did not include early visual neuropils, and thus input neurons to the lobula (which was the only visual neuropil almost fully included in the dataset) were fragmented and unlabeled. This paper summarizes my effort to categorize these neruon fragments into cell types with a hiearchical clustering approach based on connectivity and neuronal morphology.
• Tanaka & Clark (2020) Object-Displacement-Sensitive Visual Neurons Drive Freezing in Drosophila. Curr. Biol. [link]
• The visual system of Drosophila is equipped with a suite of visual projection neurons (VPNs) that are supposedly tuned to behaviorally relevant visual features (e. g. conspecifics, predators), whose activity can drive specific behavioral programs. This paper focused on one of these VPNs called LC11, whose functions and mechanisms had been unknown at the time. Here, with a psychophysics experiment, I found LC11 to be necessary for a short timescale freezing behavior in flies caused by small moving objects. In addition, I constrained the mechanism by which LC11 detects objects with connectomic analyses as well as direct visualization of their neurotransmitter inputs, and built a computational model that can explain their visual tuning well.
• Creamer, Mano, Tanaka, & Clark (2019) A flexible geometry for panoramic visual and optogenetic stimulation during behavior and physiology. Journal of Neuroscience Methods. [link]
• It is crucial to have a good visual stimulation setup to study the neural bases of visual behaviors. The standard solution among the fly researchers has been to either use custom-build LED arrays, or to simply repurpose a PC monitor. This paper proposed a low-cost, low-footprint solution to create a immersive virtual reality setup by combining a small DLP projector with a couple of mirrors. The highly parallelized psychophysics rigs using this geometry were crucial to the succsess of my other experimental projects. I performed a proof-of-principle experiment to show that one can perform optogenetic stimulations with the light from the projectors simultaneously with visual stimuli on this setup.

Human works

• Tanaka & Yotsumoto (2017) Passage of Time Judgments Is Relative to Temporal Expectation. Front. Psych. [link]
• There has been a growing interest among psychologists in the phenomenon of "passage of time judgements (POTJ)", which refers to our sense of how fast or slow time seems to be progressing, as often expressed in the statements like "time flies when you are having fun". While some psychologists have drawn a strong distinction between POTJ and memory of duration (alluding to the distinctions between time-consciousness and objective time by phenomenologists), in this paper, I tried to argue that POTJ is basically made based on deviations between remembered and expected durations with several simple experiments.
• Tanaka & Yotsumoto (2016) Networks extending across dorsal and ventral visual pathways correlate with trajectory perception. J. Vis. [link]
• This paper examined neural activities of human subjects while observing a visual illusion where dots moving straight elicit illusory sense of curvature with an fMRI.

Fly AND Human works (!)

• Agrochao*, Tanaka*, Salazar-Gatzimas & Clark (2020) Mechanism for analogous illusory motion perception in flies and humans. PNAS. (*: equal contributions) See also a WIRED coverage of this paper. [link]
• Peripheral drift illusions, where repeated patterns of luminance gradients give the illusory sense of movement, is one of the most striking kinds of visual illusions. While many theories to explain the illusion have been proposed, definitive, mechanistic explanations have been lacking. In this study, we found that flies also percieve motion in repeated gradation patterns just like ourseleves, and discovered that the illusion ultimately originates from the imbalanced contributions of bright and dark edges for motion detection. Our results demonstrate that this popular illusion is a manifestation of a strategy to efficiently detect motion by exploiting the asymmetric distribution of light and dark in our visual environment, convergently evolved in vertebrates and insects. For this study, I performed human psychophysics experiments to show that the mechanistic model of the illusion derived from the experiments in flies approximately applies to humans as well, among others.