Calyx volume in mbm^N337 males is roughtly 80% of that measured in 'Berlin' males. mbm^N337 females exhibit smaller than average mushroom bodies.

mbm^N337 homozygous and heterozygous flies demonstrate comparable patterns of landmark orientation, indicating similar responses to visual stimulation in Buridan's paradigm as control flies.

mbm^N337 flies exhibit reduced activity levels.

mbm^N337 flies exhibit wild-type walking velocity. However mbm^N337 females are extremely slow, in addition to being very inactive.

mbm^N337 heterozygous flies exhibit wild-type mushroom body anatomy in both genders.

mbm^N337 mutant flies show abnormal temperature preference behavior.

Mushroom-body deficient mbm^N337 mutants show poor performance in experience-dependent shape feature extraction, even after full training with the shape feature alone. shape recognition ability in a flight simulator is not affected in mbm^N337 flies. In addition, similar to wild-type, mbm^N337 flies show poor shape feature extraction performance in the absence of any previous experience with the shape feature. When a uniform color (green or blue) is added to all objects, mbm^N337 flies are capable of recognizing previously conditioned shape features, similar to wild-type flies. When the same color is added to the objects with the same shape in a consistent manner, mbm^N337 flies as well as wildtype exhibit recognition of the previous shape feature. Previous exposure to the color feature without training improves color feature extraction in wild-type but not in mbm^N337 mutants. Training improves this in wild-type, but not in mbm^N337 mutants.

Mutant flies subjected to a visual choice test using a position/colour cue dilemma have substantially reduced preference indexes compared to wild-type flies (which preferentially choose the position cue over the colour cue). The mutant flies cannot distinguish pertinent position or colour cues when their saliencies vary.

Mutant flies which have been trained with both colour and position cues and then their preference for a single cue (each tested separately) has been assessed during the posttraining period perform similarly to wild-type flies.

mbm^N337/mbm^N337 (or larvae fed HU to delete most of the adult mushroom bodies) female flies have similar wild type responses to noxious heat (in both a CO[2] laser beam assay and in a heat plate assay)

mbm^N337 late third instar female larvae show premature degeneration of axons in the mushroom bodies and also show a general reduction in the size of the lobe system of the mushroom bodies.

Adult mbm^N337 females show a variable mushroom body phenotype. In those females with a moderate phenotype, the structural subdivision of the mushroom body is maintained, and the α/α', β/β' and γ-lobes can still be distinguished, although there is an overall reduction in mushroom body size. In females with a strong phenotype a rudimentary calyx, peduncle and lobes structures are formed.

mbm^N337/Df(2L)A1 females are rarely recovered. These females and mbm^N337/Df(2L)A1 males have reduced mushroom bodies. mbm^N337/Df(2L)A1 third instar female larval brains show a reduction in BrdU incorporation compared to controls.

Mutants do not show defects in larval locomotory behaviour.

mbm^N337 flies show distinctly different choice behaviour from wild-type flies when facing conflicting cues (a "colour/shape dilemma") in a choice test. There is no sharp transition in flight behaviour of mbm^N337 flies as colour intensity is gradually reduced (in contrast to wild type), indicating indecisive choice-making over a wide range of colour-intensity. This difference in choice behaviour is not due to any difference in colour sensitivity between wild-type and mbm^N337 flies, and mbm^N337 flies show normal learning and memory.

Adults carrying mbm^N337 in a Canton-S background have a brain anatomy indistinguishable from that of wild type. Long and short latency responses are indistinguishable from wild-type flies in both the DLM (flight) and TTM (jump) muscles. EC₅₀ values (the concentration at which half of the long latency responses are expected to fail) for halothane for mutant flies are indistinguishable from the EC₅₀ values of Canton-S controls.

mbm^N337 mutants have a block of memory retrieval if any of the experimental conditions are changed between training and test in visual-learning assay. Flies tolerate neither a switch between monochromatic and white light, nor between dark flashes and no flashes.

The mean volume of the calyx in mbm^N337 mutants is about 10% of that in WT-Berlin controls. Approximately 80% of mbm^N337 mutant animals exhibit no or minute mushroom bodies on both sides. In the remaining 20%, the size ranges from small to normal.

The total walking activity of mbm^N337 mutant flies is significantly increased, compared to controls. The number of walking 'bouts' is not significantly affected in these flies, compared to controls. However, there a significant increase in the mean of the number of counts per bout in these flies.

Flies have a number of brain defects, the exact phenotype depending on the genetic background. In the original genetic background in which it was induced, mbm^N337 produces the following phenotype; the mushroom bodies are nearly if not completely absent in female flies, whereas the mushroom bodies of males are only reduced to approximately 3/4 normal size. In contrast, when placed in a Canton S background, mbm^N337 males and females have similar size mushroom bodies that are approximately the size of the mushroom bodies of wild-type Canton S flies. Learning scores in an olfactory conditioning assay are 36% of the Canton S control for mbm^N337 females and 58% of the Canton S control for mbm^N337 males (with mbm^N337 in the original genetic background). Associative learning remains impaired when mbm^N337 is placed in a Canton S background. Detection of odours is normal in both genetic backgrounds.

Severe defects in mushroom body development. Kenyon fibres degenerate in third larval instar larvae and are not replaced during metamorphosis. Defects in spontaneous olfactory behavior and in olfactory learning.

Most Kenyon fibres are missing in females, no calyx, peduncle or lobes are detected. Mushroom bodies may be slightly larger than normal in males. Learning performance of males as good as wild type, leaning performance of females is very low. In females degree of morphological defect is not correlated to learning performance. Response to odours is lower than wild type in males and females.

Abnormally small calyces associated with mushroom bodies in dorsal brain; peduncles and lobes are thin or missing, owing to degeneration of Kenyon cell fibers during third larval instar; these defects are essentially limited to mutant females. Mushroom bodies appear nearly normal in brains of mbm males. Osmotropotaxis (re odor discrimination) is essentially normal in females; mutant females (larvae or adults) are defective in learning tests involving odors, electric shock, or sugar, whereas males are normal or less defective.