It’s an epidemic! Another group does the right thing, retracting neuroscience paper
This month we have seen commendable instances of researchers retracting papers after identifying flaws in their own data — an outbreak of integrity that has us here at Retraction Watch applauding. (We’ve even created a new category, “doing the right thing,” at the suggestion of a reader.)
Today’s feel-good story comes from the lab of Karl Svoboda, of the Howard Hughes Medical Institute’s Janelia Farm Research Campus, in Ashburn, Va. Back in June, Svoboda and his colleagues published “Whisker Dynamics Underlying Tactile Exploration,” in the Journal of Neuroscience. Here’s what the abstract had to say about the study:
Rodents explore the world by palpating objects with their whiskers. Whiskers interact with objects, causing stresses in whisker follicles and spikes in sensory neurons, which are interpreted by the brain to produce tactile perception. The mechanics of the whisker thus couple self-movement and the structure of the world to sensation. Whiskers are elastic thin rods; hence, they tend to vibrate. Whisker vibrations could be a key ingredient of rodent somatosensation. However, the specific conditions under which vibrations contribute appreciably to the stresses in the follicle remain unclear. We present an analytical solution for the deformation of individual whiskers in response to a time-varying force. We tracked the deformation of mouse whiskers during a pole localization task to extract the whisker Young’s modulus and damping coefficient. We further extracted the time course and amplitude of steady-state forces during whisker–object contact. We use our model to calculate the relative contribution of steady-state and vibrational forces to stresses in the follicle in a variety of active sensation tasks and during the passive whisker stimuli typically used for sensory physiology. Vibrational stresses are relatively more prominent compared with steady-state forces for short contacts and for contacts close to the whisker tip. Vibrational stresses are large for texture discrimination, and under some conditions, object localization tasks. Vibrational stresses are negligible for typical ramp-and-hold stimuli. Our calculation provides a general framework, applicable to most experimental situations.
But, well, shortly thereafter, they said, the scientists caught whiff of a problem with their study. According to the retraction notice:
At the request of the authors, The Journal of Neuroscience is retracting “Whisker Dynamics Underlying Tactile Exploration” by S. Andrew Hires, Alexander L. Efros, and Karel Svoboda, which appeared on pages 9576–9591 of the June 5, 2013 issue. The authors report, “After publication we discovered that higher-order eigenmodes were incorrectly summed when calculating the time-dependence of whisker shape during touch with a rigid object. Correction of this error revealed that our boundary conditions were inappropriate for the whisker-object interactions treated in our paper. Modification of these boundary conditions will alter the results presented in Figures 6–11. We therefore wish to withdraw the article. A corrected treatment will be published in the future. We apologize for any confusion caused by this error.”
Svoboda gave us a bit more information about what happened:
We were applying our model to different experimental conditions examined by another group (George Debrégeas & Dan Shulz) and found a mismatch between their and our results. We then found an error in one of our computer routines used for calculating the total displacement of a whisker through time during contact with an object. The error caused the time-dependence of each eigenmode to behave as if it were the first eigenmode when calculating vibrational whisker displacement…
After fixing the code, the calculation showed that vibrations would force the whisker into the pole during force application, a physical impossibility for a rigid object. Thus our initial boundary conditions were insufficiently constrained. This statement in the discussion was no longer correct.
We are working through all the consequences of the new approach. There will be differences in how vibrations propagate along the whisker and how vibrational modes interacts. The results in Figures 6-11 will be quantitatively different.
As we’ve said before, this sort of retraction deserves kudos — and it underscores that retractions don’t have to be a blot on the record when there’s no reason to smell a rat.