The anatomy and output connection of a locust visual interneurone; the lobular giant movement detector (LGMD) neurone

O’Shea, Michael; Williams, J. L. D.

doi:10.1007/bf00698057

Cited by 227 publications

(106 citation statements)

References 9 publications

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“…Visual neurons tuned to detect looming objects are found in both vertebrates (Sun and Frost, 1998) and invertebrates (Gabbiani et al, 1999;Rind and Simmons, 1992). DCMD and its presynaptic neuron LGMD (the lobula giant movement detector (O'Shea and Williams, 1974) fulfil all the requirements of such looming detector neurones, being highly tuned to the approach of objects on a direct collision course, having outputs to the flight and leg motor systems of the thorax, and being involved in turning or escape responses during flight (Santer et al, 2006). DCMD has also been implicated in the control of jumping escape behaviours, acting in synergy with other descending visual interneurones (Fotowat et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

Solitary and Gregarious Locusts Differ in Circadian Rhythmicity of a Visual Output Neuron

et al. 2012

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Locusts demonstrate remarkable phenotypic plasticity driven by changes in population density. This density dependent phase polyphenism is associated with many physiological, behavioural and morphological changes, including observations that cryptic solitarious (solitary-reared) individuals start to fly at dusk, whereas gregarious (crowd-reared) individuals are day-active. We have recorded for 24-36h from an identified visual output neuron, the descending contralateral movement detector (DCMD) of Schistocerca gregaria, in solitarious and gregarious animals. DCMD signals impending collision and participates in flight avoidance manoeuvres. The strength of DCMD's response to looming stimuli, characterised by the number of evoked spikes and peak firing rate, varies approximately sinusoidally with a period close to 24h under constant light in solitarious locusts. In gregarious individuals the 24h pattern is more complex, being modified by secondary ultradian rhythms. DCMD's strongest responses occur around expected dusk in solitarious locusts, but up to 6h earlier in gregarious locusts, matching the times of day at which locusts of each type are most active. We thus demonstrate a neuronal correlate of a temporal shift in behaviour that is observed in gregarious locusts. Our ability to alter the nature of a circadian rhythm by manipulating the rearing density of locusts under identical light-dark cycles may provide important tools to investigate further the mechanisms underlying diurnal rhythmicity.

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Section: Discussionmentioning

confidence: 99%

Solitary and Gregarious Locusts Differ in Circadian Rhythmicity of a Visual Output Neuron

et al. 2012

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“…Spikes in DCMD follow spikes in its presynaptic neuron, the lobula giant movement detector (LGMD) (O'Shea and Williams, 1974) with a 1:1 relationship.…”

Section: Introductionmentioning

confidence: 99%

Compensatory Plasticity at an Identified Synapse Tunes a Visuomotor Pathway

Rogers¹,

Krapp²,

Burrows³

et al. 2007

J. Neurosci.

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We characterized homeostatic plasticity at an identified sensory-motor synapse in an insect, which maintains constant levels of motor drive as locusts transform from their solitarious phase to their gregarious swarming phase. The same mechanism produces behaviorally relevant changes in response timing that can be understood in the context of an animal's altered behavioral state. For individual animals of either phase, different looming objects elicited different spiking responses in a visual looming detector interneuron, descending contralateral movement detector (DCMD), yet its synaptic drive to a leg motoneuron, fast extensor tibiae (FETi), always had the same maximum amplitude. Gregarious locust DCMDs produced more action potentials and had higher firing frequencies, but individual postsynaptic potentials (PSPs) elicited in FETi were half the amplitude of those in solitarious locusts. A model suggested that this alone could not explain the similarity in overall amplitude, and we show that facilitation increased the maximum compound PSP amplitude in gregarious animals. There was the same linear relationship between times of peak DCMD firing before collision and the size/velocity of looming objects in both phases. The DCMD-FETi synapse transformed this relationship nonlinearly, such that peak amplitudes of compound PSPs occurred disproportionately earlier for smaller/faster objects. Furthermore, the peak PSP amplitude occurred earlier in gregarious than in solitarious locusts, indicating a differential tuning. Homeostatic modulation of the amplitude, together with a nonlinear synaptic transformation of timing, acted together to tune the DCMD-FETi system so that swarming gregarious locusts respond earlier to small moving objects, such as conspecifics, than solitarious locusts.

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“…The DCMD axon branches bilaterally within the thoracic ganglia, and synapses onto flight interneurons and motorneurons (Burrows and Rowell, 1973;Simmons, 1980;Robertson and Pearson, 1983). Each spike in the LGMD elicits a spike in the DCMD (O'Shea and Williams, 1974;Rind, 1984) and thus DCMD activity reflects the spatiotemporal properties of a looming stimulus.…”

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confidence: 99%

Habituated visual neurons in locusts remain sensitive to novel looming objects

Gray

2005

Journal of Experimental Biology

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Many animals must contend with visual cues that provide information about the spatiotemporal dynamics of multiple objects in their environment. Much research has been devoted to understanding how an identified pair of interneurons in the locust, the Descending Contralateral Movement Detectors (DCMDs), respond to objects on an impending collision course. However, little is known about how these neurons respond when challenged with multiple, looming objects of different complex shapes. I presented locusts with objects resembling either another locust or a bird approaching on a direct collision course at 3·m·s -1 while recording from the DCMD axon within the mesothoracic ganglion. Stimulus presentations were designed to test: (i) whether DCMD habituation was related to the frequency of approach, (ii) if habituated DCMDs were able to respond to a novel stimulus and (iii) if non-looming motion within complex objects (internal object motion) during approach affects habituation. DCMD responses to simulated locusts or birds habituated more when the time interval between consecutive approaches within similar sequences decreased from 34·s to 4·s. Strongly habituated DCMDs were, however, able to respond to the same object approaching along a new trajectory or to a larger object approaching along the same trajectory. Habituation was not affected by internal object motion. These data are consistent with earlier findings that DCMD habituation occurs at localized synapses, which permits maintained sensitivity to multiple objects in the animal's environment.

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The anatomy and output connection of a locust visual interneurone; the lobular giant movement detector (LGMD) neurone

Cited by 227 publications

References 9 publications

Solitary and Gregarious Locusts Differ in Circadian Rhythmicity of a Visual Output Neuron

Solitary and Gregarious Locusts Differ in Circadian Rhythmicity of a Visual Output Neuron

Compensatory Plasticity at an Identified Synapse Tunes a Visuomotor Pathway

Habituated visual neurons in locusts remain sensitive to novel looming objects

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