Figure 1.

Examples of VNS-directed plasticity. A) Repeatedly pairing VNS with a tone increases the number of neurons in primary auditory cortex (A1) that are tuned to the paired frequency¹². Each polygon represents a single microelectrode recording site and the color indicates the preferred tone frequency at that location. The left panel shows the A1 map of tone frequency in a normal rat. The right panel shows the map after a brief burst of VNS was repeatedly paired with a 9 kHz (blue) tone over twenty days. B-C) Repeatedly pairing VNS with different tones surrounding the tinnitus frequency eliminated the behavioral and neural correlates of tinnitus, including map distortion, frequency broadening, increased excitability and increased synchrony, in an animal model¹². Tinnitus was documented by the inability to detect a brief gap in a sound matched to the tinnitus frequency with no impairment in detecting gaps in other sounds²⁷. Degraded values are plotted lower on the x-axis to match the impaired behavior. The shape of the curved lines was inferred from earlier studies. Error bars show s.e.m. D) Repeatedly pairing VNS with a movement increases the number of neurons in primary motor cortex that generate the paired movement⁴⁴. The map on the left is from a rat that received VNS paired with movement of the lower forelimb (yellow). The map on the right is from a rat that received VNS paired with movement of the upper forelimb (green). Movement training alone did not alter the maps compared to naïve rats. Data adapted, with permission, from ⁹ (panels A-C), ³² (panel D).