Extended Data Fig. 6: Unitary EPSCs, EPSPs and spatiotemporal receptive fields of presynaptic thalamic units.

a, Each panel illustrates one of the 23 paired recordings. The upper part of the panel shows the shift-subtracted uEPSP (red; Methods) and the shift-subtracted uEPSC (blue; Methods) recorded during visual stimulation. The spatiotemporal receptive field (heat map) of the presynaptic thalamic unit, obtained from the response to static gratings, is shown on the bottom. For some pairs the uEPSC recorded during spontaneous activity (spont uEPSC; grey; Methods) is also shown. uEPSCs are recorded during cortical silencing; uEPSPs are recorded under control conditions. The vertical line at time 0 marks the time of the peak of the extracellularly recorded action potential in the presynaptic thalamic unit. Pair numbers of the same colour were recorded in the same postsynaptic layer 4 cortical neuron. The heat map shows the spatiotemporal receptive field of the thalamic unit in response to static gratings. Each spatiotemporal receptive field is centred (157.5°) on the preferred spatial phase (defined as the phase that produced the most spikes) of its unit except for converging pairs which are aligned to the average preferred phase of the converging units. The response of pairs marked by an asterisk were not included in the analysis of static gratings because of their poorly defined spatiotemporal receptive field. The early/late index (see Extended Data Fig. 4) for the preferred phase of the presynaptic thalamic unit is given for each pair on the top right in black except for pairs with an asterisk. uEPSCs (blue) are the average of 49–970 spike-triggered traces. uEPSPs (red) are the average of 101–1,496 spike triggered traces. Spontaneous uEPSCs (grey) are the average of 30–412 spike triggered traces. Units of pairs 10, 11, 12, 13, 14, 18, 21 and 22 are the eight presynaptic units to the compound neuron in Fig. 4 and correspond to the units numbered in Fig. 4 as 6, 7, 1, 2, 8, 5, 4 and 3, respectively. Pair 4 corresponds to the pair shown in Fig. 6 and in Extended Data Fig. 5. b, Top, correlation between the amplitude of the visually evoked uEPSC (blue in a) and the spontaneous uEPSC (grey in a) for those pairs in which both could be recorded (r = 0.95; P = 5.9 × 10⁻⁹; n = 17). The diagonal line indicates unity. Bottom, correlation between the amplitude of the visually evoked uEPSC (blue in a) and the uEPSP (red in a) for all pairs (r = 0.59; P = 0.0028; n = 23). The diagonal line is a linear fit to the data with a slope of 0.056 mV pA⁻¹.