Figure 5.

Object–space novelty during SR impairs LTP in the CA1 (a) Application of 100 Hz HFS to the Schaffer collateral—CA1 stratum radiatum synapses in freely moving mice led to LTP (n = 16). When HFS stimulation was paired with spatial object recognition (SR), the potentiation was completely abolished and fell below basal levels and then persisted for more than 24 h (1440 min; ANOVA, P < 0.0001). No inhibition in synaptic potentiation was observed when the mice were reexposed to the same objects at the same locations the next day together with HFS. When a novel spatial configuration of the same objects was presented with HFS, however, the abolishment of synaptic potentiation reemerged (ANOVA, P < 0.0001). (b) Analog traces illustrate the Schaffer collateral—CA1 field potentials at pretask, 5 min and 24 h (1440 min). Vertical scale bar corresponds to 2 mV and horizontal scale bar corresponds to 5 ms. (c) Behavioral analysis showed that the mice explored the objects significantly less during reexposure at the old positions but explored to a much greater extent when the objects were arranged in a novel configuration. Reexposure and novel configuration data are expressed as a percentage of novelty exploration. *t-test, P < 0.0001. (d) Analysis of the discrimination ratio revealed that the mice showed a decreased preference when the objects where presented at the familiar locations during reexposure and a strong increment in preference when the objects were relocated in a novel location (ANOVA, P < 0.0001).