(a) Single-unit activity of dorsolateral striatal neurons were monitored in awake freely moving mice while electrically stimulating the contralateral dentate cerebellar nucleus.
(b) Responses of a striatal neuron to cerebellar stimulations at various intensities. Rasters obtained from 200 trials at each intensity are shown together with the corresponding post –stimulus firing rate histogram. Yellow bar denotes the timing of the stimulus, and the neuron’s average waveform is displayed on the top-left.
(c) Quantification of cell shown in “b”. The change in number of spikes for the excitatory and inhibitory phases is shown in the top panel in blue and red respectively. The pause duration is shown in green in the bottom panel.

Single-unit responses of dorsolateral striatal neurons in awake freely moving mice to (a) electrical, or (b) optogenetic stimulation of the centrolateral cerebellar dentate nucleus. In both cases three general types of responses are seen: excitation, excitation followed by inhibition, and inhibition. Each neuron’s average waveforms is shown as an inset in each raster.
(c) Percent of cells responding to electrical stimulation (n=154, N=14) and optogenetic stimulation (n=33, N=4).

(a) Schematic of experimental design. Microwire arrays were implanted in the dorsolateral striatum (St), ChR2 was expressed in the dentate nucleus of the cerebellum (DN), and the optical fiber was implanted in the CL ipsilateral to the microwire implant.
(b,c) Expression of ChR2 in the injection site (b) and thalamus (c). ChR2 expression is shown in green; DAPI staining in blue. Cerebellar axons expressing ChR2 are present in multiple thalamic regions. Inset magnification: 20X. Abbreviations: Fast: fastigial nucleus; Int: interposed nucleus; and DN: dentate nucleus of the cerebellum; HP: hippocampus; CL: centrolateral thalamus; CM: centromedian nucleus; VL: ventrolateral thalamus; VM: ventromedial thalamus; VPM: ventral posteromedial thalamus; VPL: ventral posterolateral thalamus.
(d) Example responses to optogenetic stimulation of cerebellar projection axons within the CL and surrounding intralaminar thalamic nuclei.
(e) Percent of cells responding with each response type to optogenetic stimulation of cerebellar axons in the CL (n=20, N=3).
(f) Firing rate and waveform characteristics of every dorsolateral striatal neuron which showed a response (red), or was unaffected (black) by electrical or optogenetic stimulation of the cerebellum.
(g) Excitatory response latencies of striatal neurons following cerebellar activation using electrical DN stimulation, optogenetic DN stimulation, or optogenetic stimulation of cerebellar axons in the thalamus.

(a) Inactivation of the thalamus by microinjection of QX-314 or TTX blocked cerebellar-induced responses in striatal neurons. An example cell is shown on top panels. Summary data for the change in the number of spikes during excitatory and inhibitory phases of the response and the change in pause duration are shown on the bottom. Data are displayed as mean±S.E.M. ****=p<0.0001; one tailed Wilcoxon paired signed ranks test. (n=24, N=4)
(b) Optogenetic inactivation of the intralaminar nuclei by primarily optically targeting CL blocked cerebellar-induced responses in striatal neurons. Summary data as in (a). *=p<0.05, **=p<0.01; one tailed Wilcoxon paired signed ranks test. (n=10, N=2)
(c) Cerebellar-evoked striatal responses persist when the cortex is inactivated by infusion of TTX or QX314 (n=5, N=2).
(d) Single-unit (i) (n=5) or multi-unit (ii) (n=24) recording examples of excitatory responses of neurons in the dorsolateral striatum following cerebellar stimulation in a mouse in which the motor cortices were bilaterally surgically removed (N=3).

To examine whether the striatum can follow high frequency cerebellar activity, the dentate nucleus was electrically stimulated with 25 and 50 Hz trains. All neurons examined (n=32; N=5) could follow the high frequency trains.
(a–c) Example responses for different cells to a single pulse, 25 Hz train, and 50 Hz train at the same stimulation intensity. With high frequency stimulation excitatory responses dominated in some striatal cells and in others, inhibition. The last stimulus pulse at the end of each train was monitored to determine whether excitation persisted (examples in “a” and “b”), or inhibition dominated (50 Hz example shown in “c”).
(d) Both with 25 and 50 Hz trains, whether excitation or inhibition dominated during the train was correlated with the baseline firing rate of the striatal neuron; excitation was dominant in cells with higher baseline firing rates cells. (** = p<0.01; two tailed Mann-Whitney U test).

(a) Single-unit activity of dorsolateral striatal neurons was recorded in awake freely moving mice in response to activation of the motor cortex before and after high frequency stimulation of the cortex (HFS, 100 Hz). Data are presented as the ratio of the number of spikes after high frequency cortical stimulation (Δ spikes post-stimulus) to that prior to high frequency stimulation (Δ spikes pre-stimulus) with the scatter of individual cells on the left. A ratio greater than 1 indicates LTP (light blue symbols) and less than 1 indicates LTD (dark blue symbols). (mean±S.E.M., LTD n=21, LTP n=5, N = 4, *=p<0.05, ****=p<0.0001, one-tailed, one-sample Wilcoxon signed ranks).
(b) AM-251 was injected i.p. 30 minutes before delivery of cortical HFS to test whether the plasticity induced by motor cortex HFS was cannabinoid-dependent. AM-251 injected animals showed significantly more LTP than LTD (p < 0.0001, Chi-squared goodness-of-fit test). The magnitude of plasticity for cells exhibiting LTD or LTP was significantly different from unity (mean±S.E.M., LTD n = 9, LTP n =14, N =3, ****=p<0.0001, **=p<0.01, one-tailed, one-sample Wilcoxon signed ranks).
(c) The magnitude of LTD was significantly less in the animals injected with AM-251 compared with those in the control animals (one tailed Mann-Whitney U test, p < 0.05). In contrast, the magnitude of LTP in the animals injected with AM-251 was the same as that seen in the control animals (one tailed Mann-Whitney U test, p = 0.82).

(a) Cells were tested using a 5 pulse, 50 Hz train to determine whether they were reliably depolarized by cerebellar inputs.
(b) High frequency 100 Hz electrical stimulation of the cortex was combined with high frequency 50 Hz optogenetic stimulation of the dentate nucleus of the cerebellum. This HFS reliably potentiated the corticostriatal response in all the cells tested. (mean±S.E.M., LTP n=8, N=4, **=p<0.01, one-tailed, one-sample Wilcoxon signed ranks).
(c) Example cell demonstrating the timecourse of the LTP induced in (b). Time zero denotes time of paired HFS. The average firing rate of the cell as a function of time relative to HFS is shown in the right column with the red dashed line denoting the peak firing rate of the pre-HFS response.
(d) The average change in the cortico-striatal response after concurrent HFS of the cortex and cerebellum shows clear LTP. Subsequent HFS of the cortex induced LTD in the same cells. (mean±S.E.M., *=p<0.05, **=p<0.01, one tailed Wilcoxon paired signed ranks test).
(e) Effect of simultaneous cortical and cerebellar HFS on two neighboring striatal neurons recorded with the same electrode, where one cell was responsive to cerebellar stimulation and the other was not. The cell which was excited by cerebellar stimulation underwent LTP, while the non-responsive neuron showed LTD.
(f) Comparison of the strength of plasticity induced by HFS under various experimental conditions. Also shown is the “do nothing” condition, where no HFS was delivered. (p<0.0001, one tailed Kruskal-Wallis test).

(a) Simultaneous multi-unit (MUA) recording from dorsolateral striatum (top black trace) and field electromyography (fEMG; bottom green trace) in a mouse with cerebellar-induced dystonia. At the time indicated by the dashed red line the animal suffered a severe dystonic posture and this was reflected both as an increase in the MUA and concurrently in the fEMG record. The regular spikes throughout the fEMG correspond with the heartbeat.
(b) Single unit activity of a striatal neuron in an awake freely moving mouse recorded under normal conditions (Control, grey) and during cerebellar-induced dystonia (green). Scale bars denote 500 ms and 100 μV respectively.
(c) Average autocorrelation of striatal neuron activity before (grey) and after (green) cerebellar-induced dystonia show an increased tendency to burst firing during dystonia. The shaded areas denote S.E.M.
(d) Average firing rate, mode of the instantaneous firing rate, and the coefficient of variation (CV) of interspike intervals (ISI) in dorsolateral striatal neurons before (grey bars) and during (green bars) cerebellar-induced dystonia. While with dystonia the average firing rate of striatal neurons is not changed appreciably, their burst firing is reflected in their high predominant (mode) firing rate and in their irregular activity (indicated by the increase in ISI CV). Data are shown as mean±S.E.M. n= 139 control, 42 dystonia, ****=p<0.0001; two-tailed unpaired t-test.
(e) Rasters showing the spiking of representative striatal neurons recorded from control (black) and dystonic (green) mice. Each row represents 25 seconds and the same cell’s activity continues from one row to the next.
(f) The Example rasters show the activity of the same two adjacent striatal neurons recorded by the same electrode before (grey) and after (green) cerebellar-induced dystonia. Each row represents 30 seconds and the cell pair’s activities continue from one row to the next. During dystonia there is a significant increase in the periods of time when the two adjacent cells are active at the same time.
(g) Average cross-correlation of activity of adjacent striatal cell pairs under normal conditions (black) and during cerebellar-induced dystonia (green). The shading represents S.E.M. (n = 21 pairs).
(h) Dystonia scores in animals with cerebellar-induced dystonia before and after bilateral lesioning of the centrolateral nucleus of the thalamus (CL) are shown on the left column. The right figure shows Nissl stained section of tissue of a CL lesioned animal with matching stereotaxic atlas on right. Lesion area is marked in red. Scale bar, 1 mm. Data are presented as mean±S.E.M. HP: hippocampus, CL: centrolateral thalamic nucleus, LV: lateral Ventricle, CM: central medial thalamic nucleus. *=p<0.05, Wilcoxon paired signed ranks.
(i) Average dystonia scores pre, during, and post optogenetic silencing of the intralaminar thalamic nuclei in mice with cerebellar-induced dystonia. To silence neurons archaerhodpsin was expressed in the intralaminar nuclei and CL was primarily targeted by the fiber optic. The photographs show cerebellar-induced dystonia in mouse (top) and its alleviation (bottom) when laser was turned on to silence CL. *=p<0.05, Wilcoxon paired signed ranks.