Any sensory experience in any animal species can originate from either an event in the outside world, such as a predator approaching, or from a stimulus generated by the animal itself. For example, if an animal emits a threatening growl, this sound will activate auditory pathways that could indicate the presence of an aggressive conspecific, but clearly no defensive action is initiated.
Our team of researchers from the Lichtman and Engert Labs, led by then-MCO student Iris Odstrcil, recently published an investigation into how zebrafish identify self-produced sensory signals. Responses to such self-induced sensory stimuli, often called reafferent stimuli, need to be very different from responses to signals that originate from the outside world, which are commonly known as exafferent stimuli. Since the biophysical nature of these two different versions of stimuli is identical at the level of the primary sensory receptors, the distinction between them needs to happen somewhere else within the nervous system. In the somatosensory modality, i.e. touch, this distinction between reafference and exafference is equally important. Tickling, for example, is for many people an intense sensation, if, and only if, performed by another individual.
