Which of the following conditions is linked to an increase in posterior alpha activity?

An increase in posterior alpha activity is typically associated with hyperthyroidism. This condition results in an overactive thyroid, which can affect the levels of certain neurotransmitters in the brain, often leading to heightened arousal or alertness. Such alterations in brain activity can manifest as increased alpha wave production in the posterior regions of the EEG.

In contrast, the other conditions listed tend to produce varying effects on brain wave patterns that do not align with an increase in posterior alpha activity. For example, hypertension may lead to changes such as slowing in certain frequency bands due to vascular changes in the brain. Similarly, depression is often associated with a decrease in alpha activity, as patients typically present with more slow waves or theta activity instead. Chronic fatigue syndrome may produce nonspecific changes in the EEG, but it does not have a strong correlation with increased posterior alpha activity.

Thus, hyperthyroidism stands out as the condition most closely linked to increased posterior alpha waves, aligning with the known physiological effects it exerts on brain activity.