Figure 2.
Classical eyeblink conditioning using a delay paradigm. (A) In addition to the stimulating electrodes, rabbits were implanted with EMG recording electrodes in the left O.O. muscle (O.O. EMG) aimed at recording CRs. (B) Representation of the delay paradigm and the firing activity of a selected CL neuron recorded during the fifth conditioning session. From top to bottom are shown: (1) the CS (a tone; 600 Hz, 90 dB, 350 ms); (2) the US (a corneal air puff; 3 kg/cm2, 100 ms); (3) one example of the EMG activity of the O.O. muscle—note the presence of the CR in the CS–US interval as a learning-dependent response (light gray area) and the UR in the CS + US period as a reflex reaction (in dark gray area)—(4) the firing activity of a CL neuron during a CS/US presentation; (5) a raster plot of 18 successive CS/US trials; and (6) the peristimulus time histogram of all of them (in spikes/s). (C) Evolution of the percentage of CRs across six conditioning sessions for five conditioned and two pseudoconditioned rabbits. Note that conditioned animals reached the selected criterion (≥80% of CRs for two consecutive days) by the fifth conditioning session.