performed well in tests of visual naming and sentence comprehension, visual-spatial ability, and "general semantic knowledge about the world". They also noted an improved vocabulary and general knowledge base after 18 months. C.L.s episodic memory, on the other hand, was far below expectations: She could not retain daily events, where she had gone on vacation, the names of places she had been, and other such information. However, this study and others like it are susceptible to subjectivity, since it is not always possible to clearly distinguish between episodic and semantic memory. For this reason, the topic remains controversial and debated. Familiarity and the fractionation of memory
The right hippocampus is clearly necessary for familiarity in spatial tasks, whereas the left hippocampus is necessary for familiarity-based recollection in verbal tasks. Some researchers claim the hippocampus is important for the retrieval of memories, whereas adjacent cortical regions can support familiarity-based memories. These memory decisions are made based on matching already-existing memories (before the onset of pathology) to the current situation. According to Gilboa et al., patients with localized hippocampal damage can score well on a test if it is based on familiarity.Poreh et al. describe a case study of patient A.D., whose damage to the fornix rendered the hippocampus useless, but spared adjacent cortical areas – a fairly rare injury. When the patient was given a test with something with which he had some familiarity, the patient was able to score well. In general, however, A.D. had severely impaired episodic memory, but had some ability to learn semantic knowledge.
This report further expands the phenotypic spectrum to include the possibility of normal intelligence as corroborated by formal, longitudinal psycho-educational testing.The presence of two homologous low copy repeats either side of the deletion break-point suggests that non-allelic homologous recombination is the likely mechanism underlying this syndrome. Genetics
The microdeletion, around 1.6 million base pairs, in length and encompasses 5 known genes and 17 uncharacterised transcripts. These include transferrin receptor, choline-phosphate cytidylyltransferase A, RNF168, serine/threonine-protein kinase, nuclear cap-binding protein complex, melanotransferrin, DLG1 and D-beta-hydroxybutyrate dehydrogenase

Research
Research on the risk for developing schizophrenia in Ashkenazi Jews and other populations showed that 3q29 microdeletion syndrome leads to a significant higher rate of schizophrenia. In addition, a deletion at 3q29 was found to confer an increase to the odds of developing schizophrenia in a study of copy number variants and their effect on that disorder. References
External links

DECIPHER database entry for 3q29 microdeletion syndrome