TREMOR IN CREE SUBJECTS EXPOSED TO METHYLMERCURY - A PRELIMINARY-STUDY

Rest, postural, and kinetic tremors were recorded in Cree subjects (n = 36) exposed to low levels of methylmercury (MeHg) and control subjec ts (n = 30) using lasers designed to measure displacement. Displacemen t and derived velocity and acceleration time series were analyzed usin g quantitative characteristics in time and frequency domains. We found : 1) relatively low agreement between our results and those of a clini cal examination done at the time of testing (r = 0.31 for postural tre mor); 2) best discrimination with velocity of static (postural with vi sual feedback) and:kinetic tremors for which significant differences b etween the two groups are found in many of the characteristics examine d; 3) myoclonic-like finger microdisplacements in tremor of Cree subje cts; 4) significant changes in static tremor of Cree subjects followin g a kinetic task; 5) significant differences among three age-matched s ubgroups of six subjects each (Cree with higher and lower MeHg level, and a control group) in characteristics that reflect difficulty with t racking, myoclonic-like microdisplacements and change in frequency com position of tremor after the tracking task. The subtle differences det ected in this preliminary study suggest that further work is warranted to determine whether they can be unambiguously associated with exposu re to MeHg. (C) 1998 Elsevier Science Inc.