Mushroom body

How are such diverse compounds detected and recognized to elicit the associated behavior Several steps contribute to the odor coding, such as olfactory receptor interactions and processing in mushroom bodies, but also including odor interactions with OBPs. The diversity and heterogeneity of OBPs implicates these proteins in the process of odor discrimination. 

The PNs project to the LP via three antennocerebral tracts (ACT, Figure 23.5 Stocker et al., 1990). The largest of these in Drosophila is the inner ACT (iACT) that sends collaterals to the prominent mushroom bodies (MB). It carries a large population of mostly uniglomerular PNs. A smaller set of PNs project directly to... 

Wang Y., Wright N. J. D., Guo H.-F., Xie Z., Svoboda K., Malinow R., Smith D. P. and Zhong Y. (2001) Genetic manipulation of the odor-evoked distributed neural activity in the Drosophila mushroom body. Neuron 29, 267-276. 

Yusuyama K., Meinertzhagen I. A. and Schurmann F.-W. (2002) Synaptic organization of the mushroom body calyx in Drosophila melanogaster. J. Comp. Neurol. 445, 211-226. 

Desynchronization of PNs affects the specificity of neurons in the P-lobes of the mushroom bodies (a neural convergence site post-synaptic to the calyces) (MacLeod el al., 1998). Application of picrotoxin to the AL resulted in a decreased ability of P-lobe neurons to correctly identify odors. Single P-lobe neurons showed responses to odors after desynchronization to which they were formerly silent and responses to similar odors lost odor-specific temporal features seen prior to picrotoxin application. These differences were never seen in PNs and the authors concluded that information is sampled across assemblies of responding PNs and that this information converges onto single neurons in the p-lobe. Thus, neurons downstream of the AL appear to read and decode temporal information conveyed by neurons leaving the AL. 

Bicker G. (1999) Histochemistry of classical neurotransmitters in antennal lobes and mushroom bodies of the honeybee. Microsc. Res. Tech. 45(3), 174—183. 

Goldberg F., GrunewaldB., RosenboomH. and Menzel R. (1999) Nicotinic acetylcholine currents of cultured Kenyon cells from the mushroom bodies of the honey bee Apis mellifera. J. Physiol. 514, 759-768. 

The axon wiring in the insect antennal lobe is anatomically and physiologically similar to that in the mammalian olfactory bulb. Insect ORNs target and synapse with two neurons projection neurons and GABA-mediated local intemeurons. Projection neurons are second-order olfactory intemeurons that transmit the information of odorants into the mushroom body calyx and lateral horn, which is the center for olfactory-related memory formation (Heisenberg... 

Hallem EA, Carlson JR (2006) Coding of odors by a receptor repertoire. Cell 125 143-160 Heimbeck G et al (1999) Smell and taste perception in Drosophila melanogaster larva toxin expression studies in chemosensory neurons. J Neurosci 19 6599-6609 Heisenberg M (2003) Mushroom body memoir from maps to models. Nat Rev Neurosci 4 266-275... 

As detailed already, the olfactory system conveys odour information initially to the antennal lobe and then further via the projection neurons to the lateral horn and the mushroom bodies. From both these centres, premotor commands are thought to originate. The gustatory system, in contrast, carries sugar information to the suboesophageal ganglion, from where premotor commands likely can be triggered... 

Connolly et al. (1996) transgenically expressed a mutant Gas protein (CG 2835, using the G mutant) in the mushroom bodies which constitutively activates the cyclase, hence presumably rendering any modulation of cyclase activity impaired. This leads to an abolishment of memory scores after odour-shock learning. Whether a knockdown of the rut-cyclase by means of RNA interference would lead to a similar abolishment of short-term odour-shock memory is unknown. 

Thus, synaptic plasticity in the mushroom bodies is sufficient (rat-rescue) and necessary (Ga ) to establish a short-term memory trace during odour-shock training. 

Furthermore, olfactory information needs to enter the mushroom bodies during... 

---