Startle response
From The Art and Popular Culture Encyclopedia
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The startle response is a brainstem reflex that serves to protect the back of the neck (whole-body startle), or the eye (eyeblink), and also facilitates escape from sudden stimuli. It is found across the lifespan and in many species. An individual's emotional state may lead to a variety of different responses. The Startle Response is also known as the Moro reflex in younger children and is said the change around 3-6 months.
Acoustic Startle Reflex
The pathway for this response was largely elucidated in rats in the 1980s.
In summary the basic pathway follows the auditory pathway from the ear up to the Nucleus of the Lateral Lemniscus (LLN) from where it then activates a motor centre in the reticular formation. This centre sends descending projections to lower motor neurones of the limbs. In slightly more detail this corresponds to: Ear (cochlea)->Cranial Nerve VIII (auditory) -> Cochlear Nucleus (ventral/inferior) -> LLN -> Caudal pontine reticular nucleus (PnC). The whole process has a less than 10ms latency. There is no involvement of the superior/rostral or inferior/caudal colliculus in the reaction that "twitches" the hindlimbs, but these may be important for adjustment of pinnae, gaze towards the direction of the sound or the associated blink.
See also
- Prepulse inhibition - attenuation of the startle response after a weaker preceding stimulus, or prepulse.
- Surprise (emotion)
