as these inhibitors can't be used to inhibit proliferation in specific regions, thus leading to nonspecific effects from other systems being affected. To avoid these effects, more work must be done to determine optimal doses in order to minimize the effects on systems unrelated to neurogenesis. A common pharmacological inhibitor for adult neurogenesis is methylazoxymethanol acetate (MAM), a chemotherapeutic agent. Other cell division inhibitors commonly used in studies are cytarabine and temozolomide. Pharmacogenetics Another method used to study the effects of adult neurogenesis is using pharmacogenetic models. These models provide different benefits from the pharmacological route, as it allows for more specificity by targeting specific precursors to neurogenesis and specific stem cell promoters. It also allows for temporal specificity with the interaction of certain drugs. This is beneficial in looking specifically at neurogenesis in adulthood, after normal development of other regions in the brain. The herpes simplex virus thymidine kinase (HSV-TK) has been used in studies in conjunction with antiviral drugs to inhibit adult neurogenesis. It works by targeting stem cells using glial fibrillary acidic proteins and nestin expression. These targeted stem cells undergo cell death instead of cell proliferation when exposed to antiviral drugs. Cre protein is also commonly used in targeting stem cells that will undergo gene changes upon treatment with tamoxifen. Irradiation Irradiation is a method that allows for very specific inhibition of adult neurogenesis. It can be targeted to the brain to avoid affecting other systems and having nonspecific effects. It can even be used to target specific brain regions, which is important in determining how adult neurogenesis in different areas of the brain affects behavior. However, irradiation is more expensive than the other methods and also requires large equipment with trained individuals. Inhibition of adult neurogenesis in the hippocampus Many studies have observed how inhibiting adult neurogenesis in other mammals, such as rats and mice, affect their behavior. Inhibition of adult neurogenesis in the hippocampus has been shown to have various affects on learning and memory, conditioning, and investigative behaviors. Impaired fear conditioning has been seen in studies involving rats with a lack of adult neurogenesis in the hippocampus. Inhibition of adult neurogenesis in the hippocampus has also been linked to changes in behavior in tasks involving investigation. Rats also show decreased contextualized freezing behaviors in response to contextualized fear and impairment in learning spatial locations when lacking adult neurogenesis. Effects on pattern separation The