diff --git a/src/spikeinterface/extractors/nwbextractors.py b/src/spikeinterface/extractors/nwbextractors.py
index 24e400bdaf..d5f5ac60a5 100644
--- a/src/spikeinterface/extractors/nwbextractors.py
+++ b/src/spikeinterface/extractors/nwbextractors.py
@@ -68,6 +68,61 @@ def retrieve_electrical_series(nwbfile: NWBFile, electrical_series_name: Optiona
     return electrical_series
 
 
+def _read_hdf5_file(
+    *,
+    file_path: str | Path | None,
+    file: BinaryIO | None = None,
+    stream_mode: Literal["ffspec", "ros3", "remfile"] | None = None,
+    cache: bool = False,
+    stream_cache_path: str | Path | None = None,
+):
+    import h5py
+
+    if stream_mode == "fsspec":
+        import fsspec
+        from fsspec.implementations.cached import CachingFileSystem
+
+        assert file_path is not None, "file_path must be specified when using stream_mode='fsspec'"
+
+        fsspec_file_system = fsspec.filesystem("http")
+
+        if cache:
+            stream_cache_path = stream_cache_path if stream_cache_path is not None else str(get_global_tmp_folder())
+            caching_file_system = CachingFileSystem(
+                fs=fsspec_file_system,
+                cache_storage=str(stream_cache_path),
+            )
+            ffspec_file = caching_file_system.open(path=file_path, mode="rb")
+        else:
+            ffspec_file = fsspec_file_system.open(file_path, "rb")
+
+        hdf5_file = h5py.File(name=ffspec_file, mode="r")
+
+    elif stream_mode == "ros3":
+        assert file_path is not None, "file_path must be specified when using stream_mode='ros3'"
+
+        drivers = h5py.registered_drivers()
+        assertion_msg = "ROS3 support not enbabled, use: install -c conda-forge h5py>=3.2 to enable streaming"
+        assert "ros3" in drivers, assertion_msg
+        hdf5_file = h5py.File(name=file_path, mode="r", driver="ros3")
+
+    elif stream_mode == "remfile":
+        import remfile
+
+        assert file_path is not None, "file_path must be specified when using stream_mode='remfile'"
+        rfile = remfile.File(file_path)
+        hdf5_file = h5py.File(rfile, "r")
+
+    elif file_path is not None:
+        file_path = str(Path(file_path).resolve())
+        hdf5_file = h5py.File(name=file_path, mode="r")
+    else:
+        assert file is not None, "Unexpected, file is None"
+        hdf5_file = h5py.File(file, "r")
+
+    return hdf5_file
+
+
 def read_nwbfile(
     *,
     file_path: str | Path | None,
@@ -119,59 +174,14 @@ def read_nwbfile(
     if file_path is None and file is None:
         raise ValueError("Provide either file_path or file")
 
-    if stream_mode == "fsspec":
-        import fsspec
-        import h5py
-
-        from fsspec.implementations.cached import CachingFileSystem
-
-        assert file_path is not None, "file_path must be specified when using stream_mode='fsspec'"
-
-        fsspec_file_system = fsspec.filesystem("http")
-
-        if cache:
-            stream_cache_path = stream_cache_path if stream_cache_path is not None else str(get_global_tmp_folder())
-            caching_file_system = CachingFileSystem(
-                fs=fsspec_file_system,
-                cache_storage=str(stream_cache_path),
-            )
-            ffspec_file = caching_file_system.open(path=file_path, mode="rb")
-        else:
-            ffspec_file = fsspec_file_system.open(file_path, "rb")
-
-        file = h5py.File(ffspec_file, "r")
-        io = NWBHDF5IO(file=file, mode="r", load_namespaces=True)
-
-    elif stream_mode == "ros3":
-        import h5py
-
-        assert file_path is not None, "file_path must be specified when using stream_mode='ros3'"
-
-        drivers = h5py.registered_drivers()
-        assertion_msg = "ROS3 support not enbabled, use: install -c conda-forge h5py>=3.2 to enable streaming"
-        assert "ros3" in drivers, assertion_msg
-        io = NWBHDF5IO(path=file_path, mode="r", load_namespaces=True, driver="ros3")
-
-    elif stream_mode == "remfile":
-        import remfile
-        import h5py
-
-        assert file_path is not None, "file_path must be specified when using stream_mode='remfile'"
-        rfile = remfile.File(file_path)
-        h5_file = h5py.File(rfile, "r")
-        io = NWBHDF5IO(file=h5_file, mode="r", load_namespaces=True)
-
-    elif file_path is not None:
-        file_path = str(Path(file_path).absolute())
-        io = NWBHDF5IO(path=file_path, mode="r", load_namespaces=True)
-
-    else:
-        import h5py
-
-        assert file is not None, "Unexpected, file is None"
-        h5_file = h5py.File(file, "r")
-        io = NWBHDF5IO(file=h5_file, mode="r", load_namespaces=True)
-
+    hdf5_file = _read_hdf5_file(
+        file_path=file_path,
+        file=file,
+        stream_mode=stream_mode,
+        cache=cache,
+        stream_cache_path=stream_cache_path,
+    )
+    io = NWBHDF5IO(file=hdf5_file, mode="r", load_namespaces=True)
     nwbfile = io.read()
     return nwbfile
 
@@ -464,7 +474,9 @@ def get_traces(self, start_frame, end_frame, channel_indices):
             end_frame = self.get_num_samples()
 
         electrical_series_data = self.electrical_series.data
-        if isinstance(channel_indices, slice):
+        if electrical_series_data.ndim == 1:
+            traces = electrical_series_data[start_frame:end_frame][:, np.newaxis]
+        elif isinstance(channel_indices, slice):
             traces = electrical_series_data[start_frame:end_frame, channel_indices]
         else:
             # channel_indices is np.ndarray