In the article “Cell Type-Specific Tuning of Hippocampal Interneuron Firing during Gamma Oscillations In Vivo” by John J. Tukker, Pablo Fuentealba, Katja Hartwich, Peter Somogyi, and Thomas Klausberger, which appeared on pages 8184–8189 of the August 1, 2007 issue, data from two cells were erroneously allocated to cell types in the analysis. However, after omitting these two cells, all conclusions reached by us in the paper are fully supported by the remaining data. The previously published significant differences at preset alpha values between cell types remain valid; only the exact p values, vector lengths, and n numbers are affected.
Cell T139c was incorrectly classified as a cholecystokinin (CCK)-expressing cell and cell T151b, for which the code should have been T151a, was incorrectly classified as an oriens-lacunosum moleculare (O-LM) cell, as revealed by further analysis.
Changes to Materials and Methods
As before, comparison of the average gamma amplitude for all recordings (overall mean, 0.17 mV; SD, 0.07 mV; n = 27) confirmed that there was no systematic difference in gamma amplitude between the recordings for the five cell types [Kruskal–Wallis (KW) test, χ2 = 5.8; p = 0.218, n = 27]; excluding the four larger mean gamma amplitudes recorded at the SR/SLM border still did not result in a systematic difference between the gamma amplitudes recorded for different cell types (KW test, χ2 = 5.0; p = 0.284, n = 23). Furthermore, there was still no correlation between the recorded depth of modulation and the average gamma oscillation amplitude (two-tailed Spearman's nonparametric correlation test, r = 0.349, p = 0.075, n = 27); the same was true when only LFP recordings from stratum pyramidale (SP) were considered (r = 0.233, p = 0.284, n = 23) or when correlations were tested per cell class (p > 0.3; n = 5, 5, 6, 6, or 5).
Changes to Results
The corrected dataset indicated significantly gamma-modulated firing for four of six CCK cells and two of six O-LM cells. As before, the depth of modulation of interneurons revealed a significant difference between different classes (p = 0.0004, two-tailed multisample exact KW test; n = 27), and the spike timing of O-LM cells exhibited no or very little modulation during gamma oscillations (median r = 0.056, interquartile range, 0.050–0.058; n = 6), remaining different from bistratified cells (p = 0.009; two-tailed exact KW test; n = 11). As described in the published paper, the remaining 27 interneurons fired preferentially at or after the troughs of extracellular gamma oscillations in SP (p < 0.01, multisample Moore test; n = 27). The reduced population (n = 4) of significantly modulated CCK-expressing interneurons still fired significantly earlier than the other gamma-modulated cells (p = 0.03, two-sample permutation test; n = 21). The corrected results are shown in the updated figure (Fig. 3A–D). These corrections do not change our conclusions. The corrected Figure 3 is printed here.
