According to a Center for Disease Control and Prevention (CDC) report, chronic exposure to mercury can result in "a variety of manifestations of central nervous system toxicity," that is, high levels of mercury in your brain and spinal cord may cause memory loss, mental illness, and changes in or loss of hearing, vision, or taste. The CDC states mercury toxicity should be considered as a probable cause in cases where neurologic symptoms like these are of unclear etiology.
(Source: ProHealth's Healthwatch newsletter, Vol. XII, No. 1, 2003. Read complete article at http://www.immunesupport.com/Library/showarticle.cfm/ID/4486/HealthWatch/HealthWatch-Spring-2003