Aphasia is a complex language disorder that typically results from brain damage, most commonly due to a stroke, which often leads to rupture of the left cerebral artery. This disorder severely impacts an individual’s ability to speak, write, and read. Current research has shown that linguistic processes are distributed across several brain regions, forming intricate neural networks. Understanding how these regions interact is crucial for developing therapies that target specific deficits in aphasic patients. This thesis focuses on two critical brain regions involved in language processing, the inferior frontal gyrus (IFG) and the temporoparietal junction (TPJ), whose exact roles in language processing are still debated. To explore the neural mechanisms involved in these cognitive processes, we used functional connectivity (FC), a powerful tool for analyzing interactions between different brain regions. This thesis consists of three studies that examine the effects of two non-invasive brain stimulation techniques, high-definition transcranial direct current stimulation (HD-tDCS) and transcranial alternating current stimulation (tACS), on linguistic functions. They were applied to healthy participants and aphasic patients to investigate their potential for language recovery. The first study examines how HD-tDCS affects the learning of new words. Thirty-six neurotypical participants received anodal HD-tDCS over the left IFG or left TPJ while performing a word learning task. The results showed that HD-tDCS over the left IFG enhanced functional connectivity in the theta band between the IFG and TPJ, which correlated with improved learning for verbs. The second study investigated whether tACS at specific frequencies could enhance phonological processing. Twenty-four healthy participants received tACS at 10 Hz, 16.18 Hz (control frequency) or placebo stimulation. The stimulation was applied to the bilateral prefrontal cortex before performing a phonological decision task. Results indicated that increased functional connectivity in the alpha band within left temporo-parietal regions was associated with better phonological performance. The third study applied HD-tDCS to the left IFG in aphasic patients, combined with a verb learning task using computer-assisted therapy (CAT). The goal was to improve verb naming abilities in patients with chronic aphasia. Preliminary results (behavioral data from 11 subjects) suggest that HD-tDCS may enhance verb naming when applied after a period of familiarization. These findings emphasize the importance of timing for optimizing cognitive functions. Additional data from more subjects and EEG analysis are needed to confirm these results and to explore the underlying neural mechanisms during different stimulation conditions. In conclusion, this thesis highlights the potential of non-invasive brain stimulation (HD-tDCS and tACS) concerning the recovery of linguistic functions. Moreover, the theta and alpha frequency bands emerge as potential markers for the functioning of linguistic processes. The crucial role of network interactions is also evident, as cognitive efficiency depends not only on local activation but also on the communication between different brain regions. Finally, modulating functional connectivity between the left IFG and the left TPJ could enhance the effectiveness of current therapeutic approaches.