Effect of Emotional State on Eyeblink Classical Conditioning in Humans

The emotional state affects reflexive eyeblink to a startle probe. In startle probes the unconditioned eyeblink reflex to an aversive stimulus is augmented when the subject is in an emotionally negative state comparing to the positive state. The present study examines how the emotional state affects classically conditioned eyeblink to a tone. In startle probes the performance of the reflex is modified by emotional state. On the other hand, in classical eyeblink conditioning the intensity of the stimulus affects learning in a way, that more intense stimulus enhances learning. Question is, whether emotionally negative state enhances performance of the reflex, or also processing of its eliciting stimulus, in which case learning would be different depending on the emotional state. It is hypothesized, that the conditioned eyeblink response to a tone is augmented when the subject is in an emotionally negative state comparing to the response in a positive state. Three groups of participants (N = 30) were shown either appetitive, neutral or aversive pictures in continuous series during eyeblink classical conditioning. Electromyographic activity was measured to assess the eyeblink response. The augmentation of the conditioned eyeblink response to the tone was weaker with the appetitive pictures than with neutral pictures. This effect is proposed to be result of stronger motivational conflict between the pleasant motivational state and the state caused by the aversive startle stimulus. Surprisingly, the eyeblink to the tone was not augmented with the aversive pictures. This effect is suggested to reflect anxiety in the subjects.