Feature saliency in a dragonfly neuron
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1
The University of Adelaide, School of Medical Sciences, Australia
The dragonfly Hemicordulia tau pursues moving prey, often against a cluttered, visual surround. This already complex small target detection task may even occur in the presence of multiple target-like features (e.g. other potential prey and conspecifics). Yet this is only one of many challenging visual behaviors exhibited by these impressive predators, despite a small brain. To understand the neural basis for such behavior we use electrophysiological techniques to record intracellularly from feature detecting neurons, referred to as small target motion detectors (STMDs). STMDs likely underlie the dragonfly’s ability to discriminate prey motion as they provide velocity-tuned responses selective for objects of no more than a few degrees size (O’Carroll 1993).
One such neuron, the centrifugal STMD (CSTMD1) is a potential candidate for mediating higher-order mechanisms of attention towards targets in the presence of distractors. CSTMD1 gives a locally enhanced response when a target moves along a continuous trajectory (Nordström et al. 2011). Furthermore, the neural response is entirely suppressed by the presence of a second object in a visual region of the other eye (Bolzon et al. 2009). CSTMD1 takes dendritic input from one eye and has an axon that traverses the brain. The neuron arborizes in two regions on the contralateral side, with one output aligning with the input of the mirror-symmetric CSTMD1. It is possible that the two CSTMD1 neurons work together in transferring target information from one side of the brain to the other during target pursuit, but the details of these mechanisms remain unclear.
To elucidate a functional role for CSTMD1, we presented two target stimuli of varying sizes and contrasts. We found that a second ‘distracter’ target presented in the excitatory receptive field, suppresses the response of the neuron as its size is increased. Conversely, a second feature presented to the contralateral eye reveals inhibition that is itself size-tuned. Finally, we investigated how the saliency of two targets (of varying size and contrast) is encoded by the neuron through a simple form of selective attention. Putting this all together, the neuron is inhibited by either a large feature in the ipsilateral (excitatory) visual field or a small target in the contralateral eye. Additionally, if presented with multiple targets in the excitatory region, the neuron exhibits a simple form of visual attention via a competitive winner-takes-all interaction.
Acknowledgements
This research was supported by the US Air Force Office of Scientific Research (FA2386-10-1-4114)
References
O'Carroll D (1993) Feature-detecting neurons in dragonflies. Nature 362:541–543
Nordström K, Bolzon D (2011) Spatial facilitation by a high-performance dragonfly target-detecting neuron. Biology Letters 7:588–592
Bolzon D, Nordstrom K, O'Carroll D (2009) Local and Large-Range Inhibition in Feature Detection. Journal of Neuroscience 29:14143–14150
Keywords:
feature discrimination,
insect vision,
small target motion detector
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for Participant Symposium)
Topic:
Sensory: Vision
Citation:
Wiederman
SD and
O'Carrol
DC
(2012). Feature saliency in a dragonfly neuron.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00223
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Steven D Wiederman, The University of Adelaide, School of Medical Sciences, Adelaide, SA, 5005, Australia, steven.wiederman@adelaide.edu.au