Figure 5.

Eyeblink  conditioning  protocols  and  electrophysiological  recording  of  the  conditioned  eyelid  response. (a) Experimental design for eyeblink conditioning in behaving rabbits illustrating the location of the bipolar hook electrodes for the recording of orbicularis oculi muscle activity (O.O. EMG). Classical eyeblink conditioning protocol consists of pairing a conditioned stimulus (CSt) (e.g., a neutral stimulus such as a tone) and an unconditioned stimulus (USt) (e.g., an airpuff to the eye that induces a reflexive blink). (b) Two principal paradigms have been classically used depending on the temporal relationship between CSt and USt. Thus, in the delay paradigm (top) the CSt and USt coterminate. In the trace paradigm there is a constant time interval between both stimuli (bottom). (c) The figure illustrates the eyeblink conditioning process using a delay paradigm. The conditioning paradigm (CS and US presentations) and representative orbicularis oculi electromyohraphic (O.O. EMG) recordings from the same animals along seven conditioning sessions (C1–C7) are presented. Along conditioning sessions the initial unconditioned response (UR), consisting of a reflexive eyelid response just after the US, leads to a timed eyelid response which precedes the USt named the conditioned response, CR (arrows).