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In the thoracic part of the ventral cord of Nezara viridula four vibratory interneuron types were electrophysiologically identified and classified. They show different frequency-intensity characteristics, the LFVI, LFTVI and LFSVI being most sensitive in the low frequency region between 100 and 600 Hz and the HFVI being most sensitive in the higher frequency region between 600 and 1,500 Hz (Fig. 1). Simultaneous contralateral and ipsilateral stimulation shows an excitatory effect in LFVI, LFTVI and LFSVI and a small inhibitory effect in HFVI from the contralateral side (Figs. 4 and 5). All four identified vibratory interneurons reproduce the stimulus duration in a phasic-tonic way (Fig-6). The morphology of two of four electrophysiologically identified interneurons was partially described by a combined recording and staining technique. The LFTVI is a through neuron extending at least from the cervical connectives to the metathoracic part of the central ganglion and which has laterally and medially running branches (Fig. 2). Its dendritic field lies in the prothoracic ganglion. The LFSVI seems to be restricted to the mesothoracic part of the central ganglion (Fig. 3). Its axon connects two large branching fields on both sides of this segmental part. It is supposed that with this system of identified vibratory interneurons biologically important sound parameters can be recognized by Nezara viridula. [ABSTRACT FROM AUTHOR]

Most of the auditory neurons in the ventral nerve cord of Locusta migratoria carry information not only from the tympanal organs but also from the subgenual organs (vibration sensors). Six of the eight neuron types studied electrophysiologically respond to at least these two modalities. Artificial sounds (white noise and pure tones varying in frequency and intensity) and sinusoidal vibration (200 Hz with an acceleration of 15.8 cm/s or 2000 Hz and 87 cm/s) were used as stimuli. Complex excitatory and/or inhibitory interactions of the signals from both tympanal organs form the discharge patterns of auditory ventral-cord neurons in response to stimulation with air-borne sound. Normally the input of the ipsilateral sense organ dominates. The response patterns of these same neurons elicited by vibration stimuli are formed differently, as follows: (1) the sensory inputs of all subgenual organs are integrated in the responses of the ventral-cord neurons; in a single neuron they have either excitatory or inhibitory effects, but not both. (2) The more legs vibrated, the larger is the response. (3) The subgenual organs in the middle legs are most effective, those in the hind legs least so. (4) Ipsilateral vibration has more effect than contralateral. The six auditory neurons react to vibration combined with air-borne sound in different ways. The B neuron is the only one inhibited by vibration stimuli. The G neuron has been studied more intensively; because its anatomical arrangement and the location of the endings of the subgenual receptor fibers are known, it could be inferred from effects of transection of the connectives that interneurons are interposed between receptor cells and the G neuron. [ABSTRACT FROM AUTHOR]