title: Orthogonal coding of object location.
abstract: It has been argued whether internal representations are encoded using a universal ('the neural code') or multiple codes. Here, we review a series of experiments that demonstrate that tactile encoding of object location via whisking employs an orthogonal, triple-code scheme. Rats, and other rodents, actively move the whiskers back and forth to localize and identify objects. Neural recordings from primary sensory afferents, along with behavioral observations, demonstrate that vertical coordinates of contacted objects are encoded by the identity of activated afferents, horizontal coordinates by the timing of activation and radial coordinates by the intensity of activation. Because these codes are mutually independent, the three-dimensional location of an object could, in principle, be encoded by individual afferents during single whisker-object contacts. One advantage of such a same-neuron-different-codes scheme over the traditionally assumed same-code-different-neurons scheme is a reduction of code ambiguity that, in turn, simplifies decoding circuits.
authors.affiliation: Department of Neurobiology, Weizmann Institute for Science, Rehovot 76100, Israel.
authors.forename: Per Magne
authors.initials: PM
authors.lastname: Knutsen
authors.forename: Ehud
authors.initials: E
authors.lastname: Ahissar
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000344:Afferent Pathways / Q000033:anatomy & histology / Q000502:physiology; D000818:Animals; D006801:Humans; D009949:Orientation / Q000502:physiology*; D051381:Rats; D011984:Sensory Receptor Cells / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology; D014110:Touch / Q000502:physiology*; D014276:Trigeminal Nerve / Q000502:physiology; D014738:Vibrissae / Q000294:innervation / Q000502:physiology*