Distribution of dendrites of descending neurons and its implications for the basic organization of the cockroach brain

Abstract

To determine precisely the brain areas from which descending neurons (DNs) originate, we examined the distribution of somata and dendrites of DNs in the cockroach brain by retrogradely filling their axons from the cervical connective. At least 235 pairs of somata of DNs were stained, and most of these were grouped into 22 clusters. Their dendrites were distributed in most brain areas, including lateral and medial protocerebra, which are major termination areas of output neurons of the mushroom body, but not in the optic and antennal lobes, the mushroom body, the central complex, or the posteroventral part of the lateral horn. The last area is the termination area of major types of olfactory projection neurons from the antennal lobe, i.e., uni- and macroglomerular projection neurons, so these neurons have no direct connections with DNs. The distribution of axon terminals of ascending neurons overlaps with that of DN dendrites. We propose, based on these findings, that there are numerous parallel processing streams from cephalic sensory areas to thoracic locomotory centers, many of which are via premotor brain areas from which DNs originate. In addition, outputs from the mushroom body, central complex, and posteroventral part of the lateral horn converge on some of the premotor areas, presumably to modulate the activity of some sensorimotor pathways. We propose, based on our results and documented findings, that many parallel processing streams function in various forms of reflexive and relatively stereotyped behaviors, whereas indirect pathways govern some forms of experience-dependent modification of behavior.

Linking the Input to the Output: New Sets of Neurons Complement the Polarization Vision Network in the Locust Central Complex

“…The LAL-LT neuron communicates between projection areas of columnar neurons across the brain midline, whereas the LAL-pPC neuron transfers polarization information to the posterior protocerebrum. Both the LAL and the posterior protocerebrum are regions where many descending neurons receive their input (Williams, 1975;Strausfeld and Seyan, 1985;Staudacher and Schildberger, 1998;Okada et al, 2003). The different ⌽ max values of the two LAL-LT recordings implicate that several LAL-LT neurons differ in E-vector tuning or that E-vector tuning in the same neuron is dynamically adjusted corresponding to motor demands.…”

Classical conditioning of activities of salivary neurones in the cockroach

“…After removal of its legs and wings, it was pinned ventral-side-up on a wax-coated dish and the cuticle of the ventral part of the neck was removed. One SDN was cut and its proximal or distal cut-stump was inserted into a plastic tube filled with a solution containing 0.16·mol·l -1 NiCl 2 and 0.04·mol·l -1 CoCl 2 (Okada et al, 2003). The preparations were kept in a moist chamber at 4°C for 4 days.…”

“…After forwardfilling, the ventral cuticle of the thorax was removed to expose the salivary gland. Then one or two droplets of rubeanic acid were applied onto the SOG or the salivary gland for 3-5·min to precipitate the metals (Okada et al, 2003). The SOG or the salivary gland was rinsed many times with cockroach saline (Yamasaki and Narahashi, 1959), dissected out, fixed in 3-4% paraformaldehyde in cockroach saline for 30-60·min, dehydrated in a graded series of ethanol, cleared in methyl salicylate, and observed as whole mounts under a light microscope.…”

Classical Olfactory Conditioning in the Cockroach Periplaneta americana

“…They proposed that many parallel processing streams function in various forms of reflexive and relatively stereotyped behaviors, while indirect pathways govern some forms of experiencedependent modification of behavior. Notably, this organization has fundamental similarities to basic organizations of the mammalian brain: Parallel and hierarchical features of Okada et al, 2003. They are mostly confined to study using intracellular recording and staining techniques; dendritic and termination areas of the neurons are estimated from their morphology and from their neural activities. Modified from Okada et al (2003).…”