Normal oscillations in different frequency bands have an important role in cognitive processing in the frontal region. The key issue is whether frequency oscillations of Electroencephalography (EEG) are related to cognitive task or not in occipital region. All frequency bands delta (δ), theta (θ), alpha (α), beta (β) and gamma (γ) are involved in brain tasks. This study is conducted to investigate the functional relationship between EEG frequency bands and the cognitive task. In various studies theta, alpha and beta bands are discussed for cognitive tasks; however there are few studies which have been focused on delta band for cognitive tasks. In this paper, behavior of θ, α, β and γ is described but the primary focus is on delta (δ) band during cognitive task in occipital region as it had been ignored in the literature. In conclusion, this study explains how different frequencies change during cognitive task as compared to base line (eyes open) in occipital region and the results show that there is an increase in power during the task in delta and theta band. © 2014 IEEE.