Information flow through neural circuits for pheromone orientation

Abstract

Moths use a sophisticated olfactory navigation strategy for resource localization. Here we investigate the neuronal circuits involved in sensory processing to generate locomotor commands for pheromone-source orientation in the moth. We identify a candidate pathway for pheromone processing in the protocerebrum using a mass-staining technique. Our intracellular recordings of pheromone responsiveness detect four major circuits, including a newly identified unstructured neuropil, the superior medial protocerebrum, which supplies output to the lateral accessory lobe (LAL), the premotor centre for walking commands. Interneurons innervating the lower division of the LAL elicited longer responses than those innervating the upper division. Descending interneurons innervating the lower division of the LAL showed a state-dependent flip-flop response. In contrast, input from other visual areas in the protocerebrum mostly converge onto the upper division of the LAL. These results reveal the basic organization of the LAL: the upper division is identified as a protocerebral hub that receives inputs from various areas, while the lower division generates long-lasting activity for locomotor command.

A lineage-related reciprocal inhibition circuitry for sensory-motor action selection

“…As a node of convergence, situated several synapses downstream of sensory neurons and several synapses upstream of motor ganglia, the position and connectivity of the EB-LAL interface implicates it in the translation of sensory representations into motor representations. Experiments in locusts 63 and silk moths 64 identified that LAL modules preserve information about values and saliency associated with selected sensory representations. Our simulations confirm these findings and predict that the EB exerts selection on premotor commands in the LAL by modulespecific columnar projections 10,64 that retain stimulus values by a one-to-one correspondence.…”

Principles of Insect Path Integration

“…These moth neurons show so-called flip flop activity that is characterized by sustained periods of alternating high and low firing rates [114]. The transition between the two states is initiated by sensory information, most commonly short pheromone pulses [113], but can also be triggered by light flashes [115]. As neck motor neurons show flip-flop activity as well and head-turns often precede body-turns, the flip flop circuit is considered a control network for turning movements during moth odor plume tracking [116].…”

Olfactory Projection Neurons From the Moth Antennal Lobe Lateral Cluster exhibit Diverse Morphological and Neurophysiological Characteristics

“…In this image projection neurons forming the diffuse lALT bifurcate around the Great Commissure (GC). The ventral aspect of the lALT pathway (v-lALT) proceeds to the lateral protocerebrum with terminals defining the ∆-lateral protocerebral area (∆LP equivalent to the ∆ILPC described in Seki et al 2005;Namiki et al 2014) located anteromedial of the Lateral Horn (LH). The ∆LP consists of parts of the ventrolateral protocerebral neuropils (VLPN: posterior ventral lateral protocerebrum PVLP, posterior lateral protocerebrum, PLP) and superior neuropils (superior lateral protocerebrum, SLP and superior clamp, SCL).…”

“…The PN axon followed the v-lALT and made no apparent synaptic contact in the isthmus as it departed the AL before bifurcating in an area of the ventrolateral protocerebral neuropils (VLPN) anteromedial of the lateral horn with one branch invading the posterior ventrolateral protocerebrum (PVLP) (note also the small projection into the anterior ventrolateral protocerebrum, AVLP, arrow) with a second branch projecting more posterio-dorsally close to the posterior lateral fascicle (PLF) and proximal to superior clamp (SC) and superior lateral protocerebrum (SLP). This bifurcated pattern into two main branches that defines the ∆LP region (equivalent to the ∆ILPC region described by Seki et al 2005, andNamiki et al 2014). Note a small amount of staining before the VLPN terminal arbors indicating a small projection into an area populated by d-lALT axons.…”

“…Unfortunately, no individual l-lcPNs were stained (Seki et al, 2005) although reevaluations of l-lcPNs stained in the previous study (Kanzaki et al, 2003) revealed that they too arborized in the ∆LP. A further study revealed details of a protocerebral pathway for processing pheromonal information in B. mori (Namiki et al 2014). In addition to input connections from the AL through either mALT via CA or directly through mlALT/lALT into ∆LP, a significant output connection between ∆LP and another neuropil, the superior medial protocerebrum (SMP), was characterized.…”