An inhibitory process influencing visual responses in a fibre of the ventral nerve cord of locusts

doi:10.1016/0022-1910(67)90151-5

Journal of Insect Physiology

Volume 13, Issue 2, February 1967, Pages 235-242, IN5-IN7, 243-248

https://doi.org/10.1016/0022-1910(67)90151-5 Get rights and content

Abstract

A particular large fibre in each thoracic connective of locusts responds to visual stimuli and is amenable to prolonged experiment and analysis. It responds readily to movement, but luminance change in a stationary target can be equally effective. The optimal non-moving stimulus is strong dimming of a small target. Larger targets elicit responses with shorter latencies and lower thresholds but with a markedly smaller number of spikes (optimal area effect).

Dimming a large target can block a response which would have occurred to the simultaneous or immediately previous dimming of a small target up to a time interval approximately compensating the difference in latencies and independently of the position of the two targets.

A prolonged depression independent of location follows activation of the fibre. The degree of depression increases with both the amount of dimming and the area, even when increasing the area has resulted in a diminution of the first response. It is argued that the optimal area effect, the blocking effect, and post-excitatory depression are all expressions of a single inhibitory process.

The receptive field encompasses approximately a hemisphere. No evidence was obtained for a segregation of functionally distinct areas. The organization of the inhibition is probably different from (a) inhibitory surround, (b) Limulus-type lateral inhibition, or (c) recurrent inhibition.

Repeated dimming of a small light guide results in rapid habituation. However, dimming of a contiguous group of ommatidia is again effective. Reversing the direction of intensity change in the same location does not by itself reactivate the response. Habituation must be a process different from inhibition, because it is strictly localized while the latter is location-independent.

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The excitation in the S units is summed onto the LGMD and, if a given threshold is exceeded for more than a given number of time steps, a collision alert is produced. The output of both the real and the modelled neuron can be suppressed by a second form of inhibition called feed-forward inhibition (Palka 1967). The feed-forward pathway is thought to be triggered by large and rapid changes in the visual field, such as the onset of whole-field motion, and produces large inhibitory postsynaptic potentials in the LGMD (Rowell et al. 1977; Rind 1996; Santer et al. 2004).
A bio-inspired visual collision detection mechanism for cars: Optimisation of a model of a locust neuron to a novel environment
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In addition, a separate inhibitory pathway (feed-forward inhibition) was formed by summing the outputs of the photoreceptive units. If the feed-forward inhibition passed a certain threshold (FFthres) then it produced an inhibitory response on the LGMD neuron [9,11] (but see [6] for an alternative role of the feed-forward pathway). The feed-forward inhibition response was delayed by a certain number of timesteps (FFdelay) and was simulated by producing a spike value of −1 in the LGMD.
The lobula giant movement detector (LGMD) neuron of locusts has been shown to preferentially respond to objects approaching the eye of a locust on a direct collision course. Computer simulations of the neuron have been developed and have demonstrated the ability of mobile robots, interfaced with a simulated LGMD model, to avoid collisions. In this study, a model of the LGMD neuron is presented and the functional parameters of the model identified. Models with different parameters were presented with a range of automotive video sequences, including collisions with cars. The parameters were optimised to respond correctly to the video sequences using a range of genetic algorithms (GAs). The model evolved most rapidly using GAs with high clone rates into a form suitable for detecting collisions with cars and not producing false collision alerts to most non-collision scenes.
Implementation of front-end processor neural networks
1992, Neural Networks
Electronic implementation of a class of neural networks whose short-term memory equation is governed by multiplicative, rather than additive, inhibition is proposed. The network models can be derived from ionic flow in nerve membranes and multiplicative terms result from control of conductive paths by voltages of other cells in the network. Since Field Effect Transistors (FETs) are voltage controlled conductances when operated below pinch-off, these networks can be readily implemented in FET technology using this physical property. This class of neural networks appears in many areas of the brain as well as the sensory system and has been used as a basic building block for the multilayer self-organizing architecture of Adaptive Resonance Theory (ART). The model has been especially useful for explaining a wide range of peripheral visual phenomena. The implementation is intended to specifically demonstrate desirable front-end image processing properties of contrast enhancement, edge detection, dynamic range compression, and adaptation of dynamics to mean intensity levels. Since the network can be mathematically described, its dynamics and stability may be examined. Compatibility of the network with higher level processing allows for its inclusion in multilayer self-organizing neural network architectures.
Product term nonlinear lateral inhibition enhances visual selectivity for small objects or edges
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The effects of stimulus area and intensity on the on/off ratio of some locust visual interneurones
1982, Journal of Insect Physiology
The on- and off-discharges of three types of locust visual interneurones were recorded in response to luminous discs ranging in subtense from 0.4 to 25°. For the DCMD neurone there was a clear reciprocal relationship between ON and OFF, with large on- and small off-responses at 0.4°, and the reverse at 25° disc subtense. Most of the changeover from almost pure ON to almost pure OFF discharges occurred in the subtense range up to 2°, i.e. within the acceptance angle of one ommatidium or the angle between adjacent ommatidia. This behaviour was not found at low luminance levels, where ON and OFF followed parallel courses. These findings suggest the existence of strong inhibition, augmenting rapidly with increase in target subtense, as also with luminance as shown in separate experiments. For the DCMD the off-response had the characteristics of a simple rebound excitation, following a short period of light exposure.
The other visual interneurones (M and S) behaved differently. They did not show reciprocity of ON and OFF, but instead their responses followed parallel courses with increase in subtense, resembling those of the DCMD at low luminance. Nonetheless, like the DCMD, they did show peaking of the on-response at certain subtenses and luminance, although at much higher levels. The inhibitory activity defining the responses of M and S neurones appeared much less effective than that associated with the DCMD. This could be due to greater complexity in their central connexions, of which nothing is known.
Tonic effects of stationary luminous slits on the discharge rates of some locust visual interneurones
1980, Journal of Insect Physiology
The presence of an illuminated slit in the visual field of a locust compound eye produced changes in the tonic discharge rate of the DCMD and three other visual interneurones, recorded in a connective. The DCMD discharge peaked initially in the range of low slit subtenses, but over a period of minutes of exposure its character changed so that there was a rise at high subtenses also. When the luminance of a slit of fixed subtense was increased in steps, there was an initial rise then a sharp fall in discharge, indicating an abrupt onset of inhibition. Lateral spread of inhibition could account for the peak in response to slits, at a subtense falling well within the acceptance angle of a single ommatidium. The results show the ability of some visual interneurones to maintain a changed level of discharge in the presence of a stationary object in the visual field of the eye.

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^∗: Present address: Department of Zoology, Rice University, Houston, Texas.

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Journal of Insect Physiology

An inhibitory process influencing visual responses in a fibre of the ventral nerve cord of locusts

Abstract

Summation and inhibition in the frog's retina

J. Physiol.

Retinal ganglion cells responding selectively to direction and speed of image motion in the rabbit

J. Physiol.

The mechanism of directionally sensitive units in rabbit's retina

J. Physiol.

Visual perception of movement in the locust

J. Physiol.

Electrical responses to visual stimulation in the optic lobes of the locust and certain other insects

J. Physiol.

Transmission of visual responses in the nervous system of the locust

J. Physiol.

A diffraction theory of insect vision—I. An experimental investigation of visual acuity and image formation in the compound eyes of three species of insects

Functional organization of receptive fields of movement detecting neurons in the frog's retina

Pflügers Arch. ges. Physiol.

The receptive fields of optic nerve fibers

Am. J. Physiol.

The effects of spatial summation in the retina on the excitation of the fibers of the optic nerve

Am. J. Physiol.

The locust retina

The role of behavioural ecology in the design of bio-inspired technology

A bio-inspired visual collision detection mechanism for cars: Optimisation of a model of a locust neuron to a novel environment

Implementation of front-end processor neural networks

Product term nonlinear lateral inhibition enhances visual selectivity for small objects or edges

The effects of stimulus area and intensity on the on/off ratio of some locust visual interneurones

Tonic effects of stationary luminous slits on the discharge rates of some locust visual interneurones