Cognitive evoked potentials P300 after radiation exposure.

OBJECTIVE

The study was aimed at evaluating features of brain information processes and cognitive functioning in the remote period after irradiation due to the Chornobyl accident by using cognitive evoked potentials P300.

MATERIALS AND METHODS

The study included 128 people, 112 male Chornobyl clean up workers in 1986-1987 with the records of radiation doses available in Clinical and Epidemiological Registry (CER) of State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine» (NRCRM) (study group) and 16 unexposed persons due to the Chornobyl disaster (control group). At the time of the survey the average age of clean up workers (M ± SD) was (57.3 ± 5.9) years, range 44-65 years, and of unex posed persons was (57.3 ± 6.5) years, range 44-65 years. Radiation doses were within the range 0.0002-1.23 Gy, with the arithmetic mean dose (M ± SD) of (0.2 ± 0.2) Gy and the geometric mean dose of 0.1 Gy.

RESULTS

The radiocerebral effect in the projection of the left posterior superior temporal gyrus (Wernicke's area) proportionally to the radiation dose with the possible threshold of 0.05 Gy of total irradiation was revealed, with increasing radiation dose cognitive component P300 amplitude reduces and its latency period (LP) increases, espe cially at doses > 0.3-0.5 Gy. At doses > 0.5 Gy the functional relationship with the radiation dose for LP P300 increase in the projection of Wernicke's area (r = 0.9; p = 0.027) has been found.

CONCLUSIONS

The neurophysiological features detected are fully consistent with hypotheses both on radiosensitiv ity of human central nervous system and accelerated aging of the brain under the influence of small doses of ioniz ing radiation, and have questioned the feasibility of long term manned space flights (including Mars) until the development of adequate radiation hygiene standardization for space crews and invention of means for radiation protection of space flights. Further dynamic clinical and neurophysiological monitoring of individuals exposed to ionizing radiation is necessary. To identify the neurophysiological biological markers of ionizing radiation further international researches with adequate dosimetry support are needed.