diff --git a/spec/ndx-microscopy.extensions.yaml b/spec/ndx-microscopy.extensions.yaml
index da3d397..c5fb049 100644
--- a/spec/ndx-microscopy.extensions.yaml
+++ b/spec/ndx-microscopy.extensions.yaml
@@ -312,9 +312,10 @@ groups:
     - name: microscope
       doc: Link to a Microscope object containing metadata about the device used to acquire this imaging data.
       target_type: Microscope
-    - name: light_source
-      doc: Link to a LightSource object containing metadata about the device used to illuminate the imaging space.
-      target_type: LightSource
+      # TODO: figure out best way to link to list of light sources
+    - name: light_sources
+      doc: Link to an ordered list of MicroscopyLightSource objects containing metadata about the excitation method.
+      target_type: MicroscopyLightSource
     # TODO: figure out best way to link to list of optical channels
     - name: optical_channels
       doc: Link to an ordered list of MicroscopyOpticalChannel objects containing metadata about the indicator and
diff --git a/src/pynwb/ndx_microscopy/testing/_mock.py b/src/pynwb/ndx_microscopy/testing/_mock.py
index 6a32364..12cf5eb 100644
--- a/src/pynwb/ndx_microscopy/testing/_mock.py
+++ b/src/pynwb/ndx_microscopy/testing/_mock.py
@@ -291,7 +291,7 @@ def mock_VolumetricMicroscopySeries(
 def mock_MultiChannelMicroscopyVolume(
     *,
     microscope: ndx_microscopy.Microscope,
-    light_source: ndx_microscopy.LightSource,
+    light_sources: List[ndx_microscopy.MicroscopyLightSource],
     imaging_space: ndx_microscopy.VolumetricImagingSpace,
     optical_channels: List[ndx_microscopy.MicroscopyOpticalChannel],
     name: Optional[str] = None,
@@ -308,7 +308,7 @@ def mock_MultiChannelMicroscopyVolume(
         name=series_name,
         description=description,
         microscope=microscope,
-        light_source=light_source,
+        light_sources=light_sources[0],  # TODO: figure out how to specify list
         imaging_space=imaging_space,
         optical_channels=optical_channels[0],  # TODO: figure out how to specify list
         data=imaging_data,