To investigate the change of EEG signals with chautic method

when the subjects were in different mental conditions

chaotic analysis of EEG signals among 18 normal subjccts and 34 patients with various brain diseases were conducted under different mental conditions 8 of 34 patients had impairment of intelligence. When mentally activated

the value of the fracional dimemsion of EEG signals increased signifcantiy in conaparison with those of in normal subjects and in patients without impairment of intelligece at rest

but for patients with impairment of intelligence tendency of lower value was noticed. lt was concluded that chaotic analysis of EEG signals can provide information concerning human braim mental status

which may help to diagnose impairment of intelligence in early stage.