Distribution and morphology of descending brain neurons in the cricket Gryllus bimaculatus

Abstract

The number and distribution of descending brain neurons have been investigated in the cricket. The results are based on retrograde labeling of these cells with either Lucifer yellow or Neurobiotin via whole or small split portions of the cervical connectives. Various groups of cells and single neurons have been identified, and the morphology of more than 40 cells is described. Nearly 200 descending brain neurons can be stained via one cervical connective. Their perikarya are concentrated in clusters that occur ipsi- and contralateral to the filled connective and that lie dorsal and ventral in the brain. Descending cells only arborize in the nonglomerular neuropils of the brain and never branch in the optic lobe. Cells descending ipsilaterally never arborize in the contralateral hemisphere, whereas contralateral descending neurons often branch in both hemispheres. Irrespective of soma position, cells can arborize in the ventral and/or dorsal neuropils of the brain. Neurons with somata in the protocerebrum often have branches in the deutocerebrum and vice versa. The main arborizations of the cells from the prominent ventral i5 group are found in the same part of the protocerebrum. In contrast, various cells arborize in the ventral posterior deutocerebrum, but their somata are not located in different clusters. Thus, neurons from the same cluster may, but need not necessarily, arborize in the same brain area.<KWDG LANGUAGE="EN">

Front leg movements and tibial motoneurons underlying auditory steering in the cricket (Gryllus bimaculatusdeGeer)

“…Instead the gating mechanism may exist in the brain, with a descending pathway mediating the steering responses. Most of AN1's presynaptic terminals project anteroventrally in the brain, laterally of the α-lobes (Schildberger, 1984), however, most descending brain neurons extend their dendritic fields in the ventral posterior deutocerebrum (Staudacher, 1998). We therefore anticipate a cephalic auditory loop to require at least two synapses within the brain, involving local brain neurons forwarding the auditory information from AN1 towards descending pathways.…”

Encoding of near-range spatial information by descending interneurons in the stick insect antennal mechanosensory pathway

“…Second, there is a rapid, direct neural pathway involving descending interneurons (DINs) that may convey spikes to the thoracic ganglia within Ͻ20 ms after tactile stimulation. This pathway is direct in that it connects the input region of antennal afferents in the deutocerebrum and subesophageal ganglion (SOG) to neuropiles in the thoracic ganglia (e.g., Burdohan and Comer 1996;Gebhardt and Honegger 2001;Schöneich et al 2011;Staudacher 1998), which control leg movements (Burrows 1996;Büschges and Gruhn 2007;Büschges et al 2008). Here we used the stick insect Carausius morosus (de Sinéty 1901) for characterizing a large population of antennal mechanosensory DINs that mediate antennal posture and movement to thoracic ganglia.…”

“…Median numbers of 92 ipsilateral and 55 contralateral descending brain interneurons were found in the cricket (Staudacher 1998). In the stick insect, median numbers of 176 pairs of DINs with somata in the brain and 183 DINs with somata in the SOG were found (J. Goldammer, personal communication).…”

Processing of species-specific auditory patterns in the cricket brain by ascending, local, and descending neurons during standing and walking

“…Besides the experiments of Böhm and Schildberger (1992), , , and Staudacher (1998Staudacher ( , 2001, studies of neural pathways underlying cricket phonotactic behavior were usually carried out in restrained animals. However, the activity of the neurons involved in phonotaxis appeared to be strongly affected by motor activity-dependent and modulatory influences (Staudacher 2001;Staudacher and Schildberger 1998).…”