Organization of descending neurons in the brain of the desert locust.

In most animals, multiple external and internal signals are integrated by the brain, transformed and, finally, transmitted as commands to motor centers. In insects, the central complex is a motor control center in the brain, involved in decision-making and goal-directed navigation. In desert locusts, it encodes celestial cues in a compass-like fashion indicating a role in sky-compass navigation.

Space Takes Time: Concentration Dependent Output Codes from Primary Olfactory Networks Rapidly Provide Additional Information at Defined Discrimination Thresholds.

As odor concentration increases, primary olfactory network representations expand in spatial distribution, temporal complexity and duration. However, the direct relationship between concentration dependent odor representations and the psychophysical thresholds of detection and discrimination is poorly understood. This relationship is absolutely critical as thresholds signify transition points whereby representations become meaningful to the organism.

Odor detection in Manduca sexta is optimized when odor stimuli are pulsed at a frequency matching the wing beat during flight.

Sensory systems sample the external world actively, within the context of self-motion induced disturbances. Mammals sample olfactory cues within the context of respiratory cycles and have adapted to process olfactory information within the time frame of a single sniff cycle. In plume tracking insects, it remains unknown whether olfactory processing is adapted to wing beating, which causes similar physical effects as sniffing.

Detailed Characterization of Local Field Potential Oscillations and Their Relationship to Spike Timing in the Antennal Lobe of the Moth Manduca sexta.

The transient oscillatory model of odor identity encoding seeks to explain how odorants with spatially overlapped patterns of input into primary olfactory networks can be discriminated. This model provides several testable predictions about the distributed nature of network oscillations and how they control spike timing. To test these predictions, 16 channel electrode arrays were placed within the antennal lobe (AL) of the moth Manduca sexta.

Odors Pulsed at Wing Beat Frequencies are Tracked by Primary Olfactory Networks and Enhance Odor Detection.

Each down stroke of an insect's wings accelerates axial airflow over the antennae. Modeling studies suggest that this can greatly enhance penetration of air and air-born odorants through the antennal sensilla thereby periodically increasing odorant-receptor interactions. Do these periodic changes result in entrainment of neural responses in the antenna and antennal lobe (AL)? Does this entrainment affect olfactory acuity? To address these questions, we monitored antennal and AL responses in the moth Manduca sexta while odorants were pulsed at frequencies from 10-72 Hz, encompassing the natural wingbeat frequency.

A 4-dimensional representation of antennal lobe output based on an ensemble of characterized projection neurons.

A central problem facing studies of neural encoding in sensory systems is how to accurately quantify the extent of spatial and temporal responses. In this study, we take advantage of the relatively simple and stereotypic neural architecture found in invertebrates. We combine standard electrophysiological techniques, recently developed population analysis techniques, and novel anatomical methods to form an innovative 4-dimensional view of odor output representations in the antennal lobe of the moth Manduca sexta.

A multitransducer microsystem for insect monitoring and control.

This paper reports the development and in-vivo testing of a compact multitransducer microsystem intended for neuroethology experiments, including studies of gait dynamics in free-running insects. The system incorporates a combination of custom and off-the-shelf components. Its suite of measurement devices comprises leg-mounted strain gauges, electromyogram (EMG) and extracellular electrodes for the central nervous system, and a two-axis accelerometer.

Gating of sensory responses of descending brain neurones during walking in crickets.

Single descending brain neurones were recorded and stained intracellularly in the neck connectives of crickets while they walked upon a styrofoam ball under open-loop conditions. The animal's translational and rotational velocities were measured simultaneously, and various stimuli were used to investigate the neuronal response characteristics. Stimulation with a moving grating or an artificial calling song of 5 kHz induced optomotor behaviour and positive phonotaxis.