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

(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?

(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).

(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.

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

(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

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

(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.