Complex Neural Integration and Identified Interneurons in the Locust Brain
In 1971, one of us (Rowell, 197la) published an extensive literature review concerned with the analysis of responses recorded extracellularly from certain movement-detecting visual interneurons (INs) contained in the ventral thoracic nerve cord of grasshoppers and crickets. These units attracted attention because they are the most conspicuous (~ 3 mV) of the units which can be recorded with extracellular hook electrodes from the whole thoracic cord. They were characterized (Rowell, 197la) and called the descending movement detectors (DMDs). They fall into two classes depending on whether they are excited by movement in the receptive field of the eye ipsilateral or contralateral to the nerve cord projection: DIMDs or DCMDs. Prior to 1971, the DMD neurons in both crickets and grasshoppers were used in studies on perception of movement and visual acuity (Built and Catton, 1954, 1962, 1966, 1969; Palka, 1965), color sensitivity (Suga and Katsuki, 1962), and light and dark adaptation (Burtt et al.,1963, Cosens, 1966). These studies were not directed at determining either the function in behavior or the origin, in neural terms, of the specific response characteristics. The DMDs were also studied in their own right, and by 1971 a body of work had accumulated describing their specific response characteristics (Palka, 1967a,b, 1969; Rowell and Horn, 1967, 1968; Horn and Rowell, 1968; Rowell, 197la). The ease of extracellular recording still makes them an attractive and convenient assay for general properties of the visual system (Northrop, 1974; Palka and Pinter, 1975). Consideration of their role in behavior was introduced (Rowell, 197la) and extended, for the DCMD, by studies in freely moving animals (Rowell, 197lb,c).
KeywordsNerve Cord Optic Lobe Extracellular Recording Thoracic Ganglion Neural Integration
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