Cerebellar LTD in Alert Mice Figure 9. Simple and complex spike firing behavior before and during the 8-Hz electrical stimulus train. (A) Superimposed single stimulus (Stim, open arrow) trials under control conditions, before the 8-Hz stimulation. Note the SS evoked responses at the latency of the N2–N3 local field potential components (N2–N3, filled arrow). (B, C) Superimposed single traces during two 8-Hz stimulation protocols. In each case (A–C), the stimulations (Stim, open arrow) are aligned for comparisons. Single trace appears in color to facilitate the identification of SS and CS. Of note, (B) the early evoked SS is absent, and (C) the evoked SS is desynchronized compared to the control situation (A). (D) Raster sweeps (top) and related histograms (bin size = 1 ms, bottom) of the CS (upper part) and SS (lower part) evoked responses in control conditions. (E, F) Raster sweeps (top panels) and histograms (bin size = 1 ms, bottom panels) of (E) the CS and (F) SS evoked responses during the 8-Hz stimulation. doi:10.1371/journal.pone.0036184.g009 protocol of CF+molecular interneuron stimulation gave rise to an inhibitory synapse LTD [50] argues against the possibility that this inhibitory synapse was responsible for the LTD observed in the present study. Acknowledgments We thank C. Prigogine for help with the experiments and helpful discussions, and M. Dufief, E. Toussaint, T. D’Angelo, E. Hortmanns, M. Petieau, and R. Sa´nchez-Campusano for expert technical assistance. References 1. Ito M, Sakurai M, Tongroach P (1982) Climbing fibre induced depression of both mossy fibre responsiveness and glutamate sensitivity of cerebellar Purkinje cells. J Physiol 324: 113–134. 2. Ito M, Kano M (1982) Long-lasting depression of parallel fiber-Purkinje cell transmission induced by conjunctive stimulation of parallel fibers and climbing fibers in the cerebellar cortex. Neurosci Lett 33: 253–258. 3. Marr D (1969) A theory of cerebellar cortex. J Physiol (Lond) 202: 437–470. 4. Albus JS (1971) A theory of cerebellar function. Math Biosci 10: 25–61. 5. Ito M (1984) The Cerebellum and Neural Control. New York: Raven. 6. De Zeeuw CI, Yeo CH (2005) Time and tide in cerebellar memory formation. Curr Opin Neurobiol 15: 667–674. 7. Salin PA, Malenka RC, Nicoll RA (1996) Cyclic AMP mediates a presynaptic form of LTP at cerebellar parallel fiber synapses. Neuron 16: 797–803. 8. Lev-Ram V, Wong ST, Storm DR, Tsien RY (2002) A new form of cerebellar long-term potentiation is postsynaptic and depends on nitric oxide but not cAMP. Proc Natl Acad Sci U S A 99: 8389–8393. 9. Coesmans M, Weber JT, De Zeeuw CI, Hansel C (2004) Bidirectional parallel fiber plasticity in the cerebellum under climbing fiber control. Neuron 44: 691–700. 10. Servais L, Hourez R, Bearzatto B, Gall D, Schiffmann SN, et al. (2007) Purkinje cell dysfunction and alteration of long-term synaptic plasticity in fetal alcohol syndrome. Proc Natl Acad Sci U S A 104: 9858–9863. 11. Hansel C, Linden DJ (2000) Long-term depression of the cerebellar climbing fiber – Purkinje neuron synapse. Neuron 26: 473–482. Author Contributions Conceived and designed the experiments: JMR GC. Performed the experiments: JMR GC. Analyzed the data: JMR GC. Contributed reagents/materials/analysis tools: JMR GC. Wrote the paper: JMR GC. 12. Conquet F, Bashir ZI, Davies CH, Daniel H, Ferraguti F, et al. (1994) Motor deficit and impairment of synaptic plasticity in mice lacking mGluR1. Nature 372: 237–243. 13. Cre´pel F, Krupa M (1988) Activation of protein kinase C induces a long-term depression of glutamate sensitivity of cerebellar Purkinje cells. An in vitro study. Brain Res 458: 397–401. 14. Wang YT, Linden DJ (2000) Expression of cerebellar long-term depression requires postsynaptic clathrin-mediated endocytosis. Neuron 25: 635–647. 15. Hansel C, de Jeu M, Belmeguenai A, Houtman SH, Buitendijk GH, et al. (2006) aCaMKII is essential for cerebellar LTD and motor learning. Neuron 51: 835–843. 16. Bidoret C, Ayon A, Barbour B, Casado M (2009) Presynaptic NR2A-containing NMDA receptors implement a high-pass filter synaptic plasticity rule. Pro Natl Acad Sci U S A 106: 14126–14131. 17. Piochon C, Levenes C, Ohtsuki G, Hansel C (2010) Purkinje cell NMDA receptors assume a key role in synaptic gain control in the mature cerebellum. J Neurosci 30: 15330–15335. 18. Ekerot CF, Kano M (1989) Stimulation parameters including climbing fibre induced long-term depression of parallel fiber synapses. Neurosci Res 6: 264–268. 19. Jorntell H, Ekerot CF (2002) Reciprocal bidirectional plasticity of parallel fiber receptive fields in cerebellar Purkinje cells and their afferent interneurons. Neuron 34: 797–806. 20. Roggeri L, Rivieccio B, Rossi P, D’Angelo E (2008) Tactile stimulation evokes long-term synaptic plasticity in the granular layer of cerebellum. J Neurosci 28: 6354–6359. PLoS ONE | www.plosone.org 12 April 2012 | Volume 7 | Issue 4 | e36184