TROPICAL SYNAPSES
Reflections on topics including clinical neurology, recent publications in neuroscience,
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Doll's Eyes, Dragonflies, and the Media Gets It Wrong Again
The problem is that, as we see too often in media reporting on neuroscience, the Post goes for the sensational over the truthful. Its hyperbole is that they report that dragonflies have a claivoyant accuracy in predicting their prey:
"Hunting dragonflies can perfectly predict their prey’s future movements"
But even the briefest look at the article reveals that the dragonfly is not moving its head position to keep its eyes on the prey depite its prey's movements! Instead, the predictive acrobatics of dragonfly head movement is that it can keep its eyes on the prey despite the dragonfly's own flight movements. This is akin to what is tested by a human neurologist in examination of the human "vestibulo-ocular,"or "dolls-eyes," reflex, which helps us to visually track an object even as we move in space, like a baseball fielder keeping his eye on the ball. One difference is that the article suggests that head position (and thus eye position) guides body movements in the flying dragonfly, not the reverse as in the human oculo-cephalic reflex. Says the article: "Model-driven control thus underlies the bulk of interception steering manoeuvres, while vision is used for reactions to unexpected prey movements."
It is prudent to consider that, when media reporting on topics we know about can be wrong so often, we must very often be misinformed in the subjects of which we know little, if we trust the media for such information.
By the way, this article is viewable without first paying up to pass the journal's pay-wall, a welcome sign from a venerable institution like Nature.
Sensorimotor control in vertebrates relies on internal models. When extending an arm to reach for an object, the brain uses predictive models of both limb dynamics and target properties. Whether invertebrates use such models remains unclear. Here we examine to what extent prey interception by dragonflies (Plathemis lydia), a behaviour analogous to targeted reaching, requires internal models. By simultaneously tracking the position and orientation of a dragonfly’s head and body during flight, we provide evidence that interception steering is driven by forward and inverse models of dragonfly body dynamics and by models of prey motion. Predictive rotations of the dragonfly’s head continuously track the prey’s angular position. The head–body angles established by prey tracking appear to guide systematic rotations of the dragonfly’s body to align it with the prey’s flight path. Model-driven control thus underlies the bulk of interception steering manoeuvres, while vision is used for reactions to unexpected prey movements. These findings illuminate the computational sophistication with which insects construct behaviour.
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