While watching the scene where Jack Nicolson peeks through the doors in the movie The Shining, there is a natural instinct to shield your eyes from the expected horror. Researchers from the University of Tokyo may have found an answer for such a reaction.
In the study, published in Nature Communications on 13 July, the researchers found a group of neurons in the visual region of the brain that may explain the neural basis responsible for averting our eyes in the face of fear.
They saw that the group of neurons in the fruit fly (Drosophila) releases a chemical called tachykinin. Tachykinin activates the aversion response of the eyes and could open an effective approach to managing phobias and some psychiatric conditions.
“Since fear affects vision across animal species, including humans, the mechanism we found may be active in humans as well,” says Professor Masato Tsuji, Department of Biological Sciences, University of Tokyo in a statement.
Basic neurological activities like neurodevelopment, neuron signalling and learning are similar in fruit flies and humans. Genetic manipulation in experimental studies help in better and faster understanding of these interactions and the behaviour of human neurons.
The fear chemical
Tachykinin is a peptide (short chain of amino acids) produced by neurons of the central nervous system plays a significant role in pain perception, immune response, and functioning of the gastrointestinal tract. The new study highlights the importance of tachykinin in the visual circuitry of the fruit fly’s brain.
In the study, they found that a group of neurons called AOTU visual neurons in the fruit fly, bind to tachykinin in response to fear. “AOTU contains various visual neurons, each of which can drive either visual aversion or visual appetition. Tachykinin may therefore change the reactivity of AOTU to promote visual aversion,” shares Dr Tsuji to Happiest Health.
Dr Tsuji’s team used a combination of physical intimidation and molecular mechanisms to understand the fly’s activity to a visual threat. On using a combination of puffs of air and obstructive object, they observed that the flies moved away to escape them. In mutated flies with altered activity of tachykinin-releasing neurons, they saw that this fearful response was abated.
“This suggested that the cluster of neurons which releases the chemical tachykinin was necessary for activating visual aversion,” says Dr Tsuji.
‘Seeing’ it in humans
How does this translate to the human experience of fear? Dr Tsuji explains that similar characteristics have been documented for certain neurons in the visual cortex, thalamus, and amygdala. “These regions respond to an array of sensory stimuli (visual, tactile, nociceptive, gustatory, and olfactory), but whether tachykinin neurons can also respond to such a wide variety of sensory stimuli remains to be tested,” says Dr Tsuji.
A core symptom of psychiatric conditions and phobias is hyperreactivity to stimuli that may evoke mild fear in the unaffected people. Dr Tsuji believes that finding a corresponding tachykinin neural pathway in humans can help suppress the neural activity to manage them effectively.
Read more: How brain neurons rally to make a choice
