Brain tissue has an enormous quantity of connections between neurons. These become established so that neuronal activities become synchronous and different brain areas can communicate. One of the mathematical parameters that enable measurement of this connectivity is electroencephalographic (EEG) coherence. Several published studies have suggested that this coherence decreases through the aging process, with reduction of the neuron population 1 . Life expectancy in Brazil has increased over recent years and, consequently, the population of nonagenarians has increased. Therefore, there is a need for knowledge of the neurophysiological characteristics of EEG signals in cognitively normal individuals of this age.Investigation of EEG coherence enables measurement of the correlation between different brain areas. This is done through examining the mutual relationship between two EEG signals for different frequency bands. Quadratic or ordinary coherence consists of measurement of the covariance of spectral power between two pairs of electrodes 1,2,3 . Because coherence is a normative value for the power of a given frequency, it is independent of the amplitude oscillations of the signal 4,5 . Thus, this property makes coherence a relatively safe method for comparing groups of individuals, because differences in EEG potency do not affect the estimated coherence value ABSTRACT Electroencephalographic (EEG) coherence is a parameter that enables evaluation of cerebral connectivity. It may be related to the functional state of the brain. In the elderly, it may reflect the neuronal loss caused by aging. Objective: To describe characteristics of coherence in nonagenarians. Methods: We evaluated interhemispheric coherence for the alpha band in 42 cognitively normal individuals aged 90 to 101 years. Coherence values in the occipital electrode (O1O2), in the resting state with closed eyes, were calculated by means of spectral analysis using digital EEG EMSA 32 channels, 12 bits and a frequency of 200 Hz. Results: The mean coherence value for the alpha band at O1O2 was 0.65 (SD 0.13). No significant differences were found between men and women. Conclusions: The findings from this study did not show any decrease in interhemispheric coherence for the alpha band in cognitively normal nonagenarians. This may be useful as a standard value for this age group.Keywords: electroencephalography; aged, 80 and over; health of the elderly; aging. RESUMOA coerência é um parâmetro que permite avaliar a conectividade cerebral, podendo se relacionar com o estado funcional do cérebro.Especialmente nos idosos, pode refletir a perda neuronal decorrente do envelhecimento. Objetivo: Descrever características da coerência em nonagenários. Métodos: Avaliamos a coerência interhemisferica para a banda alfa em 42 indivíduos cognitivamente normais entre 90 e 101 anos. Foram calculados através da análise espectral o valor da coerência nos eletrodos O1O2, em estado de repouso e olhos fechados, com EEG digital 32 canais marca EMSA 12 bits e frequência de amost...