In some examples of selecting a target therapy delivery site for treating a patient condition, a relatively high frequency electrical stimulation signal is delivered to at least two areas within a first region (e.g., an anterior nucleus of the thalamus) of a brain of a patient, and changes in brain activity (e.g., as indicated by bioelectrical brain signals) within a second region (e.g., a hippocampus) of the brain of the patient in response to the delivered stimulation are determined. The target therapy delivery site, an electrode combination, or both, may be selected based on the changes in brain activity.