a b s t r a c t
The insect mushroom body is a higher order integration center involved in cross-sensory integration and
memory formation. The relatively large mushroom bodies of social Hymenoptera (e.g. bees) have been
related to the demands of a social system and the neural processes required to allow the animal to navigate in an ever-changi ng environment. Here I review studies aiming to elucidate the neural proce sses
that take place at the input and the output sites of the mushroom bodies and that underlie cross-sensory
integrati on, associative learning, memory storage and retrieva l. Highly processed sensory information is
received at modality-specific compartments of the input site, the calyx. The large number of intrinsic
neurons of the mushroom body receive multiple sensory inputs establishing combinations of processed
sensory stimuli. A matrix-like memory structure characterizes the dendritic area of the intrinsic neurons
allowing storage of rich combinations of sensory information. The rather small number of extrinsic neurons read out from multiple intrinsic neurons, thereby losing their sensory coding properties. The
response properties of these neurons change according to the value of stimulus combinations experienced. It is concluded that the mushroom bodies trans form the highly dimensional sensory coding space
into a low dimensional coding space of value-bas ed information. A model of such an experie nce-dependent recoding device is presented and compared with the available data.