diff --git a/brainrender_napari/napari_atlas_representation.py b/brainrender_napari/napari_atlas_representation.py
index f22518d..13b6306 100644
--- a/brainrender_napari/napari_atlas_representation.py
+++ b/brainrender_napari/napari_atlas_representation.py
@@ -96,12 +96,15 @@ def add_additional_reference(self, additional_reference_key: str):
     def _on_mouse_move(self, _, event):
         """Adapts the tooltip according to the cursor position.
 
-        No tooltip is displayed if
-        * the viewer is in 3D display
-        * or the cursor is outside annotations image
-        * or the user has chosen to switch off layer tooltips.
+        The tooltip is only displayed if
+        * the viewer is in 2D display
+        * and the cursor is inside the annotation
+        * and the user has not switched off layer tooltips.
         """
         cursor_position = self.viewer.cursor.position
+        print(type(event))
+        print(event)
+        print(event.pos)
         napari_settings = get_settings()
         tooltip_visibility = (
             napari_settings.appearance.layer_tooltip_visibility
@@ -123,7 +126,7 @@ def _on_mouse_move(self, _, event):
                 hemisphere = self.bg_atlas.hemisphere_from_coords(
                     cursor_position, as_string=True, microns=True
                 ).capitalize()
-                tooltip_text = f"{structure_name} | {hemisphere}."
+                tooltip_text = f"{structure_name} | {hemisphere}"
                 self._tooltip.setText(tooltip_text)
                 self._tooltip.adjustSize()
                 self._tooltip.show()
diff --git a/tests/test_unit/test_napari_atlas_representation.py b/tests/test_unit/test_napari_atlas_representation.py
index 481d184..0251b96 100644
--- a/tests/test_unit/test_napari_atlas_representation.py
+++ b/tests/test_unit/test_napari_atlas_representation.py
@@ -2,6 +2,8 @@
 from bg_atlasapi import BrainGlobeAtlas
 from napari.layers import Image, Labels
 from numpy import all, allclose
+from qtpy.QtCore import QEvent, QPoint, Qt
+from qtpy.QtGui import QMouseEvent
 
 from brainrender_napari.napari_atlas_representation import (
     NapariAtlasRepresentation,
@@ -123,3 +125,38 @@ def test_add_additional_reference(make_napari_viewer):
         viewer.layers[0].name
         == f"{atlas_name}_{additional_reference_name}_reference"
     )
+
+
+@pytest.mark.parametrize(
+    "cursor_position, expected_tooltip_text",
+    [
+        ((6500.0, 4298.5, 9057.6), "Caudoputamen | Left"),
+        ((-1000, 0, 0), ""),  # outside image
+    ],
+)
+def test_viewer_tooltip(
+    make_napari_viewer, mocker, cursor_position, expected_tooltip_text
+):
+    """Checks that the custom callback for mouse movement sets the expected
+    tooltip text."""
+    viewer = make_napari_viewer()
+    atlas_name = "allen_mouse_100um"
+    atlas = BrainGlobeAtlas(atlas_name=atlas_name)
+    atlas_representation = NapariAtlasRepresentation(atlas, viewer)
+    atlas_representation.add_to_viewer()
+
+    event = QMouseEvent(
+        QEvent.MouseMove,
+        QPoint(0, 0),  # any pos will do to check text
+        Qt.MouseButton.NoButton,
+        Qt.MouseButton.NoButton,
+        Qt.KeyboardModifier.NoModifier,
+    )
+    # a slight hacky mock of event.pos to circumvent
+    # the napari read-only wrapper around qt events
+    mock_event = mocker.patch.object(event, "pos", return_value=(50, 50))
+    viewer.cursor.position = cursor_position
+    atlas_representation._on_mouse_move(
+        atlas_representation.annotation, mock_event
+    )
+    assert atlas_representation._tooltip.text() == expected_tooltip_text