[Frontiers in Bioscience S2, 268-288, January 1, 2010]

Brain plasticity in Diptera and Hymenoptera

Claudia Groh1,2, Ian A. Meinertzhagen1

1Life Sciences Centre, Dalhousie University, Halifax, NS, Canada B3H 4J1, 2Department of Behavioral Physiology and Sociobiology, University of Wuerzburg, Am Hubland, 97074 Wuerzburg, Germany


1. Abstract
2. Introduction
3. Plasticity during larval and pupal development
3.1. The neuromuscular junction
3.2. Sprouting of central neurons
3.3. Sensory neurons
3.4. Synapse formation
3.5. Plasticity during metamorphosis
4. Plasticity in adult insects 4.1. Behavioural plasticity
4.2. The visual system 4.2.1. Spectral sensitivity
4.2.2. Motion detection
4.2.3. Electroretinogram
4.2.4. Synaptic changes
4.2.5. Reactive responses to loss of inputs or targets
4.2.6. Neuropile volumes
4.3. The olfactory system
4.4. Mushroom bodies
4.4.1. Adult neurogenesis
4.4.2. Neuropile volumes
4.4.3. Synaptic changes
4.5. Basis for changes in cell and neuropile volumes
5. Plasticity and the time course of evoked changes in the adult insect brain
5.1. Short-term synaptic plasticity
5.2. Long-term synaptic changes
5.3. Daily changes
5.4. Critical periods
5.4.1. Duration
6. Possible mechanisms
6.1. Factors regulating dendritic growth
6.2. Effects of neural activity
6.3. Neuromodulators
7. Conclusion
8. References


To mediate different types of behaviour, nervous systems must coordinate the proper operation of their neural circuits as well as short- and long-term alterations that occur within those circuits. The latter ultimately devolve upon specific changes in neuronal structures, membrane properties and synaptic connections that are all examples of plasticity. This reorganization of the adult nervous system is shaped by internal and external influences both during development and adult maturation. In adults, behavioural experience is a major driving force of neuronal plasticity studied particularly in sensory systems. The range of adaptation depends on features that are important to a particular species, so that learning is essential for foraging in honeybees, while regenerative capacities are important in hemimetabolous insects with long appendages. Experience is usually effective during a critical period in early adult life, when neural function becomes tuned to future conditions in an insect's life. Changes occur at all levels, in synaptic circuits, neuropile volumes, and behaviour. There are many examples, and this review incorporates only a select few, mainly those from Diptera and Hymenoptera.