Talk:Vibrissal location coding
The authors have contributed an excellent article. My only major criticism is that the authors have presented our understanding of how rodents localize objects with their vibrissae in a manner that is a bit too simple; the reader might think the problem of object localization is basically solved. In fact, the field is highly dynamic. To the extent that this Scholarpedia article will serve as an introduction to “Vibrissal location coding” for a broad audience, I feel it requires either a bit of expansion or a clearer delineation of what topics are skipped over (or, since this is Scholarpedia, what topics are “to be filled in”).
In particular, the reader might come away thinking the authors provide a more or less comprehensive description of how object location is coded by vibrissa-responsive neurons---i.e. that vertical, horizontal and radial spatial dimensions correspond to the three orthogonal encoding dimensions of labeled line identity, latency and firing rate. While this is an elegant hypothesis, the supporting data comes from fictive whisking in anesthetized animals, mainly from the trigeminal ganglion. But animals are likely reading out 3D location from sensory-motor cortex, which is required in many localization tasks (Hutson and Masterton 1986; Krupa et al. 2001; O’Connor et al. 2010). An organized description of cortical coding, esp. in behaving animals, is merited but absent (the discussion in the “Recoding section” is minimal). I realize this is a complicated and dynamic topic. I think it is reasonable for the authors largely to skip a discussion of cortical coding, but they should more clearly delineate the scope of the article. This will help provide a framework as the article undergoes expansion and revision over the next several years. One solution would be to include a section on cortical coding in between the sections on “Neural encoding of object location by primary afferents” and “Behavioral features of object localization.” Even a section that mainly highlights mysteries would be useful.
Minor points: -The description of behavior during radial localization is based on a single behavioral paradigm, namely the aperture discrimination task for freely moving rats of Nicolelis and colleagues. There are a couple statements that are not generally true, based on Pammer et al. 2009, SfN Abstracts, 174.5. First, in the section titled: “Behavioral features of object localization”: “Whisking is absent…during radial localization” is not generally true. Second, in the section titled: “Orthogonal encoding of object location”: "Consistent with this, behaving animals also need multiple whiskers to localize objects along the radial axis." Again, not generally true. The authors may want either to make clear that their conclusions apply to a particular behavioral paradigm or to loosen some of their statements. -The text related to Fig. 4 discusses coding in the trigeminal ganglion. The Fig. 4 legend describes the depicted data as being from the trigeminal nuclei. Are these not recordings from the trigeminal ganglion? Possibly the figure is mislabeled.