Summary: Researchers report on the role of the thalamus in perception and reaction to predators.
Source: University of Queensland.
How the zebrafish brain perceives and reacts to predators has been determined by researchers at the University of Queensland.
School of Biomedical Sciences Associate Professor Ethan Scott said the processing of visual threats by the brain represented a really interesting puzzle in neuroscience.
“Animals ranging from insects to humans will try to escape physically in response to a visual threat,” Dr Scott said.
“But we don’t know how the brain recognises that the stimulus is threatening or decides to escape.
“Because zebrafish larvae are small and transparent, we examined activity across the entire brain using microscopes while visual threats were presented.
“This gave us a window into the brain’s responses.”
Queensland Brain Institute postdoctoral fellow Dr Lucy Heap completed the study while undertaking a PhD at the Faculty of Medicine.
She said the study involved showing zebrafish a large threatening shape moving towards them.
“We found that visual information received from the eyes was broken down into components, such as shapes and brightness,” Dr Heap said.
“These components then needed to be processed separately by two different parts of the brain for the fish to respond appropriately.
“When a visual threat appeared, cells in a particular part of the brain, the thalamus, lit up.
“But if we interfered with activity in the thalamus, the fish failed to recognise the threat and did not swim away.
“These results help to complete our picture of how different sensory information travels through the brain, and how the brain represents the outside world.
“Because these functions are abnormal in patients with certain psychiatric disorders, including autism spectrum disorder and schizophrenia, this work sets the stage for deeper studies into the disorders’ basic mechanisms.”
Source: Claire Usmar – University of Queensland
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is credited to University of Queensland.
Original Research: Abstract for “Luminance Changes Drive Directional Startle through a Thalamic Pathway” by Lucy A.L. Heap, Gilles Vanwalleghem, Andrew W. Thompson, Itia A. Favre-Bulle, and Ethan K. Scott in Neuron. Published July 5 2018.
doi:10.1016/j.neuron.2018.06.013
[cbtabs][cbtab title=”MLA”]University of Queensland”New Brain Pathway for Escaping Predators Discovered.” NeuroscienceNews. NeuroscienceNews, 5 July 2018.
<https://neurosciencenews.com/predator-escape-9517/>.[/cbtab][cbtab title=”APA”]University of Queensland(2018, July 5). New Brain Pathway for Escaping Predators Discovered. NeuroscienceNews. Retrieved July 5, 2018 from https://neurosciencenews.com/predator-escape-9517/[/cbtab][cbtab title=”Chicago”]University of Queensland”New Brain Pathway for Escaping Predators Discovered.” https://neurosciencenews.com/predator-escape-9517/ (accessed July 5, 2018).[/cbtab][/cbtabs]
Abstract
Luminance Changes Drive Directional Startle through a Thalamic Pathway
Highlights
•The thalamus responds to looming stimuli and specifically to drops in luminance
•Thalamic projection neurons deliver luminance information to the tectum
•In the absence of luminance information, escapes are less frequent and nondirectional
•Directional visual startle depends on comparisons of luminance across the two eyes
Summary
Looming visual stimuli result in escape responses that are conserved from insects to humans. Despite their importance for survival, the circuits mediating visual startle have only recently been explored in vertebrates. Here we show that the zebrafish thalamus is a luminance detector critical to visual escape. Thalamic projection neurons deliver dim-specific information to the optic tectum, and ablations of these projections disrupt normal tectal responses to looms. Without this information, larvae are less likely to escape from dark looming stimuli and lose the ability to escape away from the source of the loom. Remarkably, when paired with an isoluminant loom stimulus to the opposite eye, dimming is sufficient to increase startle probability and to reverse the direction of the escape so that it is toward the loom. We suggest that bilateral comparisons of luminance, relayed from the thalamus to the tectum, facilitate escape responses and are essential for their directionality.
