Heat Stress–Mediated Plasticity in a Locust Looming-Sensitive Visual Interneuron

2005 ◽  
Vol 93 (4) ◽  
pp. 1908-1919 ◽  
Author(s):  
Tomas G. A. Money ◽  
Michael L. Anstey ◽  
R. Meldrum Robertson
Keyword(s):  
High Temperature ◽  
Heat Shock ◽  
Action Potential ◽  
Locusta Migratoria ◽  
Firing Frequency ◽  
Neural Pathways ◽  
Movement Detector ◽  
Migratory Locust ◽  
Visual Interneuron ◽  
Contralateral Movement

Neural circuits are strongly affected by temperature and failure ensues at extremes. However, detrimental effects of high temperature on neural pathways can be mitigated by prior exposure to high, but sublethal temperatures (heat shock). Using the migratory locust, Locusta migratoria, we investigated the effects of heat shock on the thermosensitivity of a visual interneuron [the descending contralateral movement detector (DCMD)]. Activity in the DCMD was elicited using a looming stimulus and the response was recorded from the axon using intracellular and extracellular methods. The thoracic region was perfused with temperature-controlled saline and measurements were taken at 5° intervals starting at 25°C. Activity in DCMD was decreased in control animals with increased temperature, whereas heat-shocked animals had a potentiated response such that the peak firing frequency was increased. Significant differences were also found in the thermosensitivity of the action potential properties between control and heat-shocked animals. Heat shock also had a potentiating effect on the amplitude of the afterdepolarization. The concurrent increase in peak firing frequency and maintenance of action potential properties after heat shock could enhance the reliability with which DCMD initiates visually guided behaviors at high temperature.

Background complexity affects response of a looming-sensitive neuron to object motion

2015 ◽  
Vol 113 (1) ◽  
pp. 218-231 ◽  
Author(s):  
Ana C. Silva ◽  
Glyn A. McMillan ◽  
Cristina P. Santos ◽  
John R. Gray
Keyword(s):  
Flow Field ◽  
Locusta Migratoria ◽  
Three Dimensional ◽  
Object Motion ◽  
Stimulus Complexity ◽  
Movement Detector ◽  
Behavioral Context ◽  
Firing Rates ◽  
Moving Stimulus ◽  
Contralateral Movement

An increasing number of studies show how stimulus complexity affects the responses of looming-sensitive neurons across multiple animal taxa. Locusts contain a well-described, descending motion-sensitive pathway that is preferentially looming sensitive. However, the lobula giant movement detector/descending contralateral movement detector (LGMD/DCMD) pathway responds to more than simple objects approaching at constant, predictable trajectories. In this study, we presented Locusta migratoria with a series of complex three-dimensional visual stimuli presented while simultaneously recording DCMD activity extracellularly. In addition to a frontal looming stimulus, we used a combination of compound trajectories (nonlooming transitioning to looming) presented at different velocities and onto a simple, scattered, or progressive flow field background. Regardless of stimulus background, DCMD responses to looming were characteristic and related to previously described effects of azimuthal approach angle and velocity of object expansion. However, increasing background complexity caused reduced firing rates, delayed peaks, shorter rise phases, and longer fall phases. DCMD responded to transitions to looming with a characteristic drop in a firing rate that was relatively invariant across most stimulus combinations and occurred regardless of stimulus background. Spike numbers were higher in the presence of the scattered background and reduced in the flow field background. We show that DCMD response time to a transition depends on unique expansion parameters of the moving stimulus irrespective of background complexity. Our results show how background complexity shapes DCMD responses to looming stimuli, which is explained within a behavioral context.

Enhancement of Short-Term Synaptic Plasticity by Prior Environmental Stress

2001 ◽  
Vol 85 (3) ◽  
pp. 1332-1335 ◽  
Author(s):  
J. W. Barclay ◽  
R. M. Robertson
Keyword(s):  
High Temperature ◽  
Locusta Migratoria ◽  
Neuromuscular Synapse ◽  
Temperature Limit ◽  
High Temperature Stress ◽  
Neural Pathways ◽  
Short Term ◽  
Short Term Plasticity ◽  
Stressful Environment ◽  
Chemical Synapses

All chemical synapses can rapidly up- or downregulate the strength of their connections to reshape the postsynaptic signal, thereby stressing the informational importance of specific neural pathways. It is also true that an organism's environment can exert a powerful influence on all aspects of neural circuitry. We investigated the effect of a prior high-temperature stress on the short-term plasticity of a neuromuscular synapse in the hindleg tibial extensor muscle of Locusta migratoria. We found that the prior stress acted to precondition the synapse by increasing the upper temperature limit for synaptic transmission during a subsequent stressful exposure. As well, preexposure to a stressful high-temperature environment increased short-term facilitation of excitatory junction potentials concurrent with a decrease in excitatory junction potential amplitude and a reduction in its temporal parameters. We conclude that a stressful environment can modify synaptic physiological properties resulting in an enhancement of short-term plasticity of the synapse.

Connexions Between a Movement-Detecting Visual Interneurone and Flight Motoneurones of a Locust

1980 ◽  
Vol 86 (1) ◽  
pp. 87-97
Author(s):  
PETER SIMMONS
Keyword(s):  
Movement Detector ◽  
Excitatory Postsynaptic Potentials ◽  
Schistocerca Americana ◽  
Postsynaptic Potentials ◽  
Contralateral Movement ◽  
Contralateral Eye ◽  
Stimulation Of

Both of the descending contralateral movement detector (DCMD) neurones of Schistocerca americana gregaria, which respond to stimulation of the contralateral eye or to loud noises, mediate excitatory postsynaptic potentials in most ipsilateral flight motoneurones.

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