During wakefulness thalamocortical (TC) neurons are typically depolarised and fire ‘tonic’ Na2+-mediated action potentials (APs), whereas during sleep they are more hyperpolarised and typically fire ‘bursts’ of APs that are driven by low threshold Ca2+ spikes (LTS). In many other neurons, including pyramidal neurons, APs have been demonstrated to actively backpropagate far into the dendritic tree and play a major role in synaptic integration. Using patch clamp recording and two photon Ca2+ imaging (Fluo 5F/Fluo 4FF and Alexa 594, G/R), we studied dendritic Ca2+ changes evoked by tonic APs and LTS-mediated AP bursts in TC neurons of the lateral geniculate nucleus. Thalamic slices were prepared from Wistar rats that had been fully anaesthetized with isoflurane in accordance with the UK Animal Scientific Procedure Act. LTS evoked by somatic current injection (50 ms, 50-180 pA) into TC neurons held at -72.4 ± 0.3 mV produced quasi-synchronous global dendritic Ca2+ transients that were temporally aligned with the somatic voltage inflection, which signifies the onset of the LTS, and that were significantly larger in distal dendrites (< 50 µm, ΔG/R = 0.17 ± 0.02; >100 µm, 0.26 ± 0.02, n = 8, P < 0.05, one-way ANOVA). LTS evoked Ca2+ transients were also significantly larger than bursts of 3 bAPs evoked at 200 Hz (3bAPs, ΔG/R = 0.06 ± 0.007, P < 0.05) and reduced significantly by TTX (500 nM, P < 0.05, n = 6). In marked contrast, trains of APs (10-50 Hz, 500 ms) evoked somatically (2 ms, 1-1.5 nA) from a holding potential of -50 mV produced Ca2+ elevations that were spatially restricted to proximal dendrites (30 Hz, < 50 µm, 0.129 ± 0.011; >100 µm, 0.006 ± 0.001, n = 8, P < 0.001). In proximal dendrites Ca2+ increases were linearly related to tonic firing frequency (10 Hz, 0.037 ± 0.004; 30 Hz, 0.095 ± 0.014; 50 Hz, 0.17 ± 0.019, n = 7) and plateau levels matched predictions based upon single bAP evoked transients. Moreover, τdecay for each train was not significantly different from τdecaybAP indicating that Ca2+ extrusion is also linearly related to activity during tonic firing at frequencies up to 50 Hz. Unlike LTS Ca2+ transients bAP transients were completely abolished in TTX. LTS evoked Ca2+ transients in distal dendrites were significantly reduced by focal ‘puffed’ applications of the T-type calcium channel antagonist TTA-P2 but were not significantly reduced in TTX. These results demonstrate, for the first time, the presence of T-type calcium channels in distal dendrites of TC neurons and highlight the spatial and temporal differences in dendritic calcium signalling during the classical ‘tonic’ and ‘burst’ firing modes.