The early gene knockout studies with a neurobiological focus were directed at fairly obvious target genes and added very little to our knowledge of behavioural neuroscience. On the contrary, since the behavioural consequences were often predictable, this helped confirm that the technology was working. However, a substantial number of knockouts of genes expressed in the brain have been without obvious behavioural consequences, supporting the concept of genetic canalisation and redundancy. Others have produced a behavioural deficit for which there is no (...) obvious explanation. Many cells of different tissue types have a capacity for memory, and in the brain, cells of the hippocampus are important for spatial learning and memory. Deleting genes that are expressed in the happpocampus has received considerable attention in this behavioural context. Although the initial studies experienced problems of interpretation, considerable advances have since been made. Knockout mice are now subject to tests of different forms of learning, multicellular hippocampal recordings, and restricted gene deletion specific to cells of component regions. This multi‐level approach is proving more informative. Nevertheless, there is still a need to recognise that behavioural expression is several steps removed from gene expression, and that the relationship between genes and behaviour can be reciprocal. (shrink)

Mammalian vomeronasal receptors respond to pheromones conveying information on gender, reproductive status and individual recognition. The question arises as to how this information is coded, which parts of the code require combinatorial activity and whether or not there are specific receptor neurons committed to sex discrimination. Are there receptor neurons that are committed to responding for female or male pheromones? Is there a sex difference for the proportion of these receptors, bearing in mind that it is very much in the (...) male's interest to distinguish the restricted oestrous phase of the female's cycle in order to successfully mate? Perhaps more intriguing is the complexity of individual recognition and whether or not the vomeronasal receptors actually possess this capacity. A recent paper in Science1 by Ron Yu and colleagues addresses these issues by literally visualising patterns of activity in VNO slices and determining what information is common across different individuals and what distinguishes them. BioEssays 30:802–805, 2008. © 2008 Wiley Periodicals, Inc. (shrink)