What is typically observed in an EEG when a person is alert?

When a person is alert and actively engaged in mental activities, beta waves are typically observed in an electroencephalogram (EEG). Beta waves are characterized by their high frequency and low amplitude, ranging from about 12 to 30 Hz. They are associated with active thinking, problem-solving, and concentration. This state is marked by increased cognitive processing and mental engagement, which correlates with the presence of beta waves.

In contrast, alpha waves, which occur when a person is relaxed and awake but not processing much information (such as during calm, meditative states), have a frequency between 8 and 12 Hz. Delta waves, which are the slowest with a frequency of 0.5 to 4 Hz, are typically present during deep sleep. Theta waves, with a frequency range of 4 to 8 Hz, often occur during light sleep or deep relaxation. Thus, during states of alertness and active engagement, the EEG is primarily dominated by beta waves.