Figure 5. Optogenetic stimulation of PV+ inhibitory neurons prevents SRP expression.

(A) Blue light was delivered locally into V1 via optic fibers chronically implanted at a 45° angle to target the VEP recording site in layer 4 of binocular V1 of PV-Cre mice infected with AAV5-EF1α-DIO-hChR2(H134R)-eYFP. (B) Experimental timeline showing that after viral infection, electrode implantation, and ChR2 expression; mice were accustomed to head-fixation and gray screen viewing. Subsequently, they underwent a standard SRP induction protocol over 6 days. On day 7, mice viewed a novel oriented stimulus in addition to the familiar stimulus and, on 50% of presentations of each stimulus, blue light (473 nm) was delivered to cortex to optogenetically activate PV+ cells. (C) Significant SRP was induced over 6 days as VEPs underwent a typical potentiation. (D) On day 7, SRP was expressed through significantly larger VEP magnitude in response to the familiar X^o orientation than a novel X + 90° stimulus when blue light was not delivered (Black bars). In the presence of blue light (blue bars), VEPs were suppressed, and there was a significant reduction in the differential magnitude of VEPs driven by familiar and novel stimuli. (E) The ratio of VEP magnitude elicited by familiar/novel stimuli was significantly reduced by optogenetic activation of PV+ neurons, reflecting a decrement in SRP expression. Significant comparisons are marked with an asterisk and post hoc test p values are reported in D to emphasize the impact of laser stimulation on SRP selectivity. Error bars are standard error of the mean (S.E.M.).

DOI: http://dx.doi.org/10.7554/eLife.11450.013

Figure 5—figure supplement 1. Blue light has no impact on SRP expression.

(A) To check that light itself had no effect on cortical physiology in the optogenetic experiments, WT mice were infected bilaterally with AAV5-EF1α -DIO-hChR2(H134R)-eYFP in binocular V1. After 4 weeks, during which ChR2 was expressed at high levels in PV-Cre mice, WT mice were taken through the standard SRP protocol described above. Again, significant SRP occurred. (B) On test day, during interleaved presentations of a familiar and novel oriented stimulus together with either blue light (473 nm) or no light stimulation delivery to V1, VEPs were significantly greater in magnitude for the familiar than the novel stimulus, regardless of the presence of blue light. Significant comparisons are marked with an asterisk throughout while non-significant comparisons are marked with n.s. Error bars are standard error of the mean (S.E.M.).

DOI: http://dx.doi.org/10.7554/eLife.11450.015