Portugues Lab

New paper alert! 🚨

We found that the brain's compass is remarkably stable at two scales

1️⃣ the system maintains its internal organization for weeks
2️⃣ It "remembers" its orientation for weeks, even after a single visit

This may be key to how the brain aligns its other maps.

Paper: rdcu.be/e3waP

We propose that behavioral alignment is a general principle that should be considered when understanding sensorimotor representations.

Read the study here: doi.org/10.64898/202...

We check this behavioral alignment principle by measuring behavior in larval zebrafish and showing that we can predictively account for visual encoding throughout the brain: population codes represent visual stimuli according to the optomotor responses they elicit.

Normative theories such as efficient coding have constrained representations from the sensory input side. Here, we propose that representations to sensory stimuli should be similar when they elicit similar behaviors.

Have you ever wondered how the brain should represent the sensory world in order to generate behavior? Read our new preprint: work by Shuhong Huang shuhonghuang.bsky.social with our long-standing collaborator James Fitzgerald at Northwestern.

Plastic landmark anchoring in zebrafish compass neurons - Nature Using two-photon microscopy with a panoramic virtual reality setup, how head direction cells in larval zebrafish integrate visual landmarks and optic flow to track orientation is revealed.

Nature research paper: Plastic landmark anchoring in zebrafish compass neurons

go.nature.com/4qP4HwB

Plastic landmark anchoring in zebrafish compass neurons Nature - Using two-photon microscopy with a panoramic virtual reality setup, how head direction cells in larval zebrafish integrate visual landmarks and optic flow to track orientation is revealed.

6/6: Although the habenula-IPN is conserved across vertebrates, in mammals it is thought that anchoring to visual scenes occurs at the level of retrosplenial cortex and postsubiculum. Mystified? Read the paper here: rdcu.be/eX1L4 Congrats Ryosuke! (@ryosuketanaka.bsky.social)

5/6: The study shows that the anchoring of the HD system to the visual scene in this little fish occurs in the habenula-IPN pathway, using a similar architectural motif to what has been observed in flies.

4/6: This requires that neurons that were originally tuned to opposite headings and inhibited each other, shift their relative tuning, as required by the underlying ring attractor structure, indicating a high level of plasticity that can map landmark position to heading in an all-to-all manner.

3/6: The relation between landmark position and heading varies across animals and is experience-dependent. In fact, if you show two identical landmarks, neurons tuned to one heading acquire two preferred (and out-of-phase) headings.

2/6: This study shows that the heading direction (HD) network in larval zebrafish can use visual cues, both landmarks and optic flow, to track orientation in visual environments. Landmark tracking requires an intact projection from the “visual” habenula to the interpeduncular nucleus (IPN).

Plastic landmark anchoring in zebrafish compass neurons Nature - Using two-photon microscopy with a panoramic virtual reality setup, how head direction cells in larval zebrafish integrate visual landmarks and optic flow to track orientation is revealed.

1/6: New publication from the lab: “Plastic landmark anchoring in zebrafish compass neurons” by Ryosuke Tanaka (@ryosuketanaka.bsky.social) and Ruben is available here:
rdcu.be/eX1L4

Neuronal calcium spikes enable vector inversion in the Drosophila brain In the fly central complex, PFNa neurons switch from firing classical sodium spikes when depolarized to firing non-canonical T-type calcium spikes when hyperpolarized. This bidirectional spiking allow...

www.cell.com/cell/fulltex...

We had a lot of fun working on this project (led by Itzel Ishida, not on bluesky). Some interesting highlights from the paper -

A multi-ring shifter network computes head direction in zebrafish From insects to fish to mammals, many species have an internal compass: a set of recurrently connected neurons that combine motor feedback, vestibular signals, and external cues to compute the animal’...

n/n: The method recapitulates what we know from fly central complex anatomy and then predicts that the zebrafish HDN is also a three-ring shifter network! Interested in the details? Read the paper with our friends from Munich here: www.biorxiv.org/content/10.6...

4/n: Siyuan developed a framework that is able to distinguish shifter networks from velocity-modulated synaptic networks. The key point is that shifter networks require neurons that have conjunctive heading and angular velocity responses, whereas the alternative does not.

3/n: In fly, functional work, supported by the impressive connectome, show that its HDN is a shifter network made up of three rings: a central ring that encodes heading and two rings that shift the bump CW or CCW. What happens in zebrafish? Structure from function is much trickier there.

2/n: Heading direction networks (HDNs) are biological instantiations of ring attractors (RAs), but there are different classes of RAs that incorporate angular velocity signals in different mechanistic ways.

1/n: A new collaborative preprint from the lab to start the year: "A multi-ring shifter network computes head direction in zebrafish" together with Siyuan Mei, Martin Stemmler and Andreas Herz from the LMU, Munich.

Adam Kampff’s passion for understanding and explaining the world was unmatched. Living by example and not ever compromising on his dreams, Adam was uncanny in making people realize they can learn and understand anything and everything. Keep his dream alive!
In his own words: tinyurl.com/ye29csw3

Schematic of how ER-EPG plasticity enables the bump of activity in EPGs to accurately track visual cues. As a fly makes a counter-clockwise turn (top to bottom) it will view visual cues (e.g. the sun) from a new angle and the EPG activity bump (red) will swing clockwise around the network by integrating self motion signals with these visual inputs. When the fly faces a different angle, distinct visual ER neurons are active. Plasticity forms a trough of weak synapses (large circles - strong synapses, small circles - weak synapses) that allow ER neurons with distinct visual tuning to move the EPG bump via disinhibition.

*First preprint from our lab* !!!!!
How does the brain learn to anchor its internal sense of direction to the outside world? 🧭
led by Mark Plitt @markplitt.bsky.social & Dan Turner-Evans, w/ Vivek Jayaraman:
“Octopamine instructs head direction plasticity” www.biorxiv.org/content/10.6...
Thread ⬇️

Visual motion and landmark position align with heading direction in the zebrafish interpeduncular nucleus - Nature Communications How are various visual signals integrated in the vertebrate brain for navigation? Here authors show that different spatial signals are topographically organized and align to one another in the zebrafi...

(n/n) The parallels with insect navigation systems suggest deep conservation of spatial computation principles across evolution. Thanks to the team! For more read the full paper: www.nature.com/articles/s41...

(9/n) This work reveals how vertebrate navigation circuits organize multiple spatial signals (heading direction, visual motion, and landmarks) in aligned topographic maps, enabling flexible integration for navigation.

(8/n) This shows the habenula specifically provides landmark information to anchor the heading system to visual scenes.

(7/n) Habenula ablations revealed:

- Visual motion responses in the IPN persist without habenular input
- Landmark representations in the IPN require intact habenula
- The heading direction network continues to function normally in darkness without habenular input

(6/n) But here's the surprise: using targeted ablations, we found the habenula's role is highly specific.

(5/n) Critically, this striped organization aligns with how HD is represented in the same regions - suggesting the IPN as an integration site for spatial signals.

Where do these visual signals come from? The habenula contains neurons responding to both directional motion and landmark position.

(4/n) What we found reveals a striking organizational principle 👇

In the dorsal IPN, both directional motion AND landmark position are topographically organized in parasagittal stripes (running front-to-back).

(3/n) We wanted to address a fundamental question in navigation: how do animals integrate visual cues like optic flow (indicating traveling direction) and landmarks (for anchoring position) with their internal sense of heading direction?

(2/n) We discovered that navigationally relevant visual signals are topographically organized in the interpeduncular nucleus (IPN) and aligned with the heading direction signal.

Visual motion and landmark position align with heading direction in the zebrafish interpeduncular nucleus - Nature Communications How are various visual signals integrated in the vertebrate brain for navigation? Here authors show that different spatial signals are topographically organized and align to one another in the zebrafi...

(1/n) We are excited to share our new paper in Nature Communications, by Hagar Lavian (@hlavian.bsky.social) and team, revealing how the zebrafish brain integrates visual navigation signals! www.nature.com/articles/s41...