Phenobarbital primarily causes which change in EEG?

Phenobarbital is a barbiturate with sedative and anticonvulsant properties. Its effect on the EEG is characterized by a general increase in beta activity. This is due to its ability to enhance inhibitory neurotransmission and facilitate a state of sedation or relaxation in the patient, resulting in more organized brain activity.

When phenobarbital is administered, it generally stabilizes neuronal firing, leading to increased beta patterns, especially in individuals who are undergoing treatment for seizures or certain types of neurological disorders. These beta waves are faster brain waves that can dominate the EEG when a person is alert or in a relaxed state, often indicating a level of cognitive engagement.

In contrast, while other options might describe different EEG patterns linked to other medications or states, the unique characteristic of phenobarbital's influence is the promotion of beta activity in the EEG readings, making it the correct answer in this context.