Aa, stimulation of the principal vibrissa drives excitation in the recorded VB neurone (VB), followed by recurrent inhibition via the TRN. Ab, PSTH record showing responses of the principal vibrissa when stimulated with a short-duration stimulus. Ba, stimulation of an adjacent secondary vibrissa drives lateral inhibition onto the recorded VB neurone, via the TRN. Bb, PSTH record showing responses when stimulation of the principal vibrissa is preceded by stimulation of the secondary vibrissa. Note the reduction in the response to the test stimulus (arrow). T: 20 ms short-duration test stimulation to the principal vibrissa; C: 20 ms conditioning stimulation to a secondary vibrissa; spike count: the total number of action potentials recorded per 2 ms bin over 6 trials. PSTHs were constructed using responses from the same cell (CVB050b).

Aa, the top three PSTHs represent responses from a single neurone to short-duration stimulation of the principal vibrissa under control conditions, during application of the Group II agonist, and during recovery. The bottom bar graph represents the mean responses of a group of neurones (n = 44) to short-duration stimulation of the principal vibrissa under the same conditions. Ab, the top three PSTHs represent responses from a single neurone upon execution of the condition–test protocol under control conditions, during application of the Group II agonist, and during recovery. The bottom bar graph represents the mean inhibitions of a group of neurones (n = 25) to the condition–test protocol under the same conditions. Ba, the top three PSTHs represent responses from a single neurone to short-duration stimulation of the principal vibrissa under control conditions, upon co-application of the Group II agonist and the mGlu2 PAM and during recovery. The bottom bar graph represents the mean responses of a group of neurones (n = 22) to short-duration stimulation of the principal vibrissa under control conditions, upon application of the Group II agonist alone, and upon co-application of the Group II agonist and the mGlu2 PAM. Bb, the top three PSTHs represent responses from a single neurone to the condition–test protocol under control conditions, during co-application of the Group II agonist and the mGlu2 PAM, and during recovery. The bottom bar graph represents the mean reduction in sensory inhibition of a group of neurones (n = 14) compared to control to application of the Group II agonist alone, or co-applied with the mGlu2 PAM upon execution of the condition–test protocol. T: 20 ms short-duration test stimulation to the principal vibrissa; C: 20 ms conditioning stimulation to a secondary vibrissa; spike count: the total number of action potentials recorded per 2 ms bin over 6 trials. All PSTHs are constructed using responses from the same cell (CVB050b). Bar graph data are expressed as means ± SEM; *P < 0.05.

A, the top three PSTHs represent responses from a single neurone to short-duration stimulation of the principal vibrissa under control conditions, during application of the mGlu2 PAM, and during recovery. The bottom bar graph represents the mean responses of a group of neurones (n = 39) to short-duration stimulation of the principal vibrissa under the same conditions. B, the top three PSTHs represent responses from a single neurone upon execution of the condition–test protocol under control conditions, during application of the mGlu2 PAM, and during recovery. The bottom bar graph represents the mean inhibitions of a group of neurones (n = 7) to the condition–test protocol under the same conditions. T: 20 ms short-duration test stimulation to the principal vibrissa; C: 20 ms conditioning stimulation to a secondary vibrissa; spike count: the total number of action potentials recorded per 2ms bin over 6 trials. All PSTHs are constructed using responses from the same cell (CVB049c). Bar graph data are expressed as means ± SEM; *P < 0.05.

A, the top three PSTHs represent responses from a single neurone during continuous NMDA application (see Methods) to short-duration stimulation of the principal vibrissa under control conditions, during application of the Group II agonist, and during recovery. The bottom bar graph represents the mean inhibitions of a group of neurones (n = 6) to short-duration stimulation of the principal vibrissa under the same conditions. B, the top three PSTHs represent responses from a single neurone during continuous NMDA application to short-duration stimulation of a secondary vibrissa under control conditions, during application of the Group II agonist, and during recovery. The bottom bar graph represents the mean inhibitions of a group of neurones (n = 6) to short-duration stimulation of a secondary vibrissa under the same conditions. T: 30 ms short-duration test stimulation to the principal vibrissa; C: 30 ms conditioning stimulation to a secondary vibrissa; spike count: the total number of action potentials recorded per 50 ms bin over 30 trials. All PSTHs are constructed using responses from the same cell (CVB060b). Bar graph data are expressed as means ± SEM; *P < 0.05.

A, the top three PSTHs represent responses from a single neurone during continuous NMDA application (see Methods) to short-duration stimulation of the principal vibrissa under control conditions, during application of the mGlu2 PAM, and during recovery. The bottom bar graph represents the mean inhibitions of a group of neurones (n = 6) to short-duration stimulation of the principal vibrissa under the same conditions. B, the top three PSTHs represent responses from a single neurone during continuous NMDA application to short-duration stimulation of a secondary vibrissa under control conditions, during application of the mGlu2 PAM, and during recovery. The bottom bar graph represents the mean inhibitions of a group of neurones (n = 6) to short-duration stimulation of a secondary vibrissa under the same conditions. T: 30 ms short-duration test stimulation to the principal vibrissa; C: 30 ms conditioning stimulation to a secondary vibrissa; spike count: the total number of action potentials recorded per 50 ms bin over 30 trials. All PSTHs are constructed using responses from the same cell (CVB060b). Bar graph data are expressed as means ± SEM; *P < 0.05.

A, the top three PSTHs represent responses from a single neurone to long-duration stimulation of the principal vibrissa under control conditions, during application of the Group II agonist, and during recovery. The bottom bar graph represents the mean responses of a group of neurones (n = 21) to long-duration stimulation of the principal vibrissa under the same conditions. B, the top three PSTHs represent responses from a single neurone to long-duration stimulation of the principal vibrissa under control conditions, upon co-application of the Group II agonist and the mGlu2 PAM, and during recovery. The bottom bar graph represents the mean responses of a group of neurones (n = 8) to long-duration stimulation of the principal vibrissa under control conditions, upon application of the Group II agonist alone and upon co-application of the Group II agonist and the mGlu2 PAM. T: 1000 ms long-duration test stimulation to the principal vibrissa; spike count: the total number of action potentials recorded per 200 ms bin over 18 trials. All PSTHs are constructed using responses from the same cell (CVB038d). Bar graph data are expressed as means ± SEM; *P < 0.05.

The top three PSTHs represent responses from a single neurone to long-duration stimulation of the principal vibrissa under control conditions, during application of the mGlu2 PAM, and during recovery. The bottom bar graph represents the mean responses of a group of neurones (n = 22) to long-duration stimulation of the principal vibrissa under the same conditions. T: 1000 ms long-duration test stimulation to the principal vibrissa; spike count: the total number of action potentials recorded per 100 ms bin over 18 trials. All PSTHs are constructed using responses from the same cell (CVB043a). Bar graph data are expressed as means ± SEM; *P < 0.05.

A, the top three PSTHs represent responses from a single neurone to short-duration stimulation of the principal vibrissa under control conditions, during application of the Group II antagonist, and during recovery. The bottom bar graph represents the mean responses of a group of neurones (n = 12) to short-duration stimulation of the principal vibrissa under the same conditions. B, the top three PSTHs represent responses from a single neurone upon to long-duration stimulation of the principal vibrissa under control conditions, during application of the Group II antagonist, and during recovery. The bottom bar graph represents the mean inhibitions of a group of neurones (n = 7) to the condition–test protocol under the same conditions. T₁: 30 ms short-duration test stimulation to the principal vibrissa; T₂: 500 ms long-duration test stimulation to the principal vibrissa; spike count: the total number of action potentials recorded per bin (20 ms bins in A, 100 ms bins in B) over 6 trials. All PSTHs are constructed using responses from the same cell (CVB085c). Bar graph data are expressed as means ± SEM; *P < 0.05.