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Lacey and Lacey (1970). Heart rate typically increases in
response to feared stimuli when presented visually or
imagined. On the other hand, HR deceleration follows the
visual presentation of a novel or interesting stimulus,
whereas imaging of a novel or interesting stimuli produces
HR acceleration followed by deceleration.
Facial Electromyography (EMG)
Before describing the facial electromyography research,
the neuroanatomical pathways involved in facial muscle
movements will be briefly reviewed. Motor neurons send
information from the brain to innervate muscle and can be
distinguished from sensory neurons which bring information
to the brain. There are two types of motor neurons: upper
motor neurons (UMN) and lower motor neurons (LMN). Upper
motor neurons carry impulses from motor centers in the brain
to the brain stem and spinal cord. Lower motor neurons
carry information from brain stem and spinal cord to
muscles. At the UMN level, fibers from either the
contralateral or both hemispheres supply impulses to the LMN
nucleus, the motor nucleus of the facial nerve, which
innervates muscles of facial expression. The voluntary and
involuntary motor pathways mediating facial expression are
distinct from one another. Voluntary movement is mediated
by the corticobulbar tract, originating in the precentral
gyrus of the motor cortex of the frontal lobe. The
involuntary pathway includes the basal ganglia, red nucleus,