Systems and methods for applying signals, including contralesional electromagnetic signals, to neural populations, are disclosed. A particular method can be directed to treating a patient having a subject neural population in a first (e.g., ipsilesional) hemisphere of the brain, with the subject neural population having, or previously having, a functionality capable of being improved. The method can include directing an application of electromagnetic signals at least proximate to a target neural population at a second (e.g., contralesional) hemisphere of the brain to at least constrain a functionality of the target neural population, which has transcallosal communication with the first hemisphere.