diff --git a/helperFunctions.py b/helperFunctions.py
index e17c063..10da3dc 100644
--- a/helperFunctions.py
+++ b/helperFunctions.py
@@ -137,6 +137,7 @@ def all_calculate_mean_isi_frequencies(spiketimes, time_start, sampling_interval
     return times, mean_frequencies
 
 
+# TODO remove additional time vector calculation!
 def calculate_isi_frequency(spiketimes, time_start, sampling_interval):
     first_isi = spiketimes[0] - time_start
     isis = [first_isi]