A high proportion of patients who have suffered a
stroke also suffer from
aphasia. Approximately half of those affected will remain in this state despite intensive
language therapy. Non-invasive brain stimulation allows us to directly and focally stimulate areas of the brain. Repetitive
transcranial magnetic stimulation (rTMS) and
transcranial direct current stimulation (
tDCS), methods used in the treatment of
aphasia, are based on an imbalance of mutual interhemispheric inhibition. In open and
sham-controlled studies, a low-frequency, 1Hz stimulation of the non-lesioned hemisphere (the homologue of Broca's area) for a week or more significantly improved spontaneous speech and
anomia in patients with non-
fluent aphasia. These positive outcomes from rTMS stimulation developed slowly, often over months following treatment, and persisted. Effects of intermittent theta burst stimulation (iTBS) developed faster than the low-frequency stimulation, and high-activity enhancement was detected in the left hemisphere after the stimulation of Broca's region. Both types of
tDCS stimulation resulted in improved comprehension and reduced
anomia, their primary modes of action are distinct, however, both share a common site of action with regard to the balance that occurs between inhibitory and excitatory
neurotransmitters (synaptic and non-synaptic). Both types of non-invasive stimulation prepare the lesioned brain for better outcome.