Valentina Fiori

Transcranial direct current stimulation improves word retrieval in healthy and nonfluent aphasic subjects

A number of studies have shown that modulating cortical activity by means of transcranial direct current stimulation (tDCS) affects performances of both healthy and brain-damaged subjects. In this study, we investigated the potential of tDCS to enhance associative verbal learning in 10 healthy individuals and to improve word retrieval deficits in three patients with stroke-induced aphasia. In healthy individuals, tDCS (20 min, 1 mA) was applied over Wernickes area (position CP5 of the International 10–20 EEG System) while they learned 20 new “words” (legal nonwords arbitrarily assigned to 20 different pictures). The healthy subjects participated in a randomized counterbalanced double-blind procedure in which they were subjected to one session of anodic tDCS over left Wernickes area, one sham session over this location and one session of anodic tDCS stimulating the right occipito-parietal area. Each experimental session was performed during a different week (over three consecutive weeks) with 6 days of intersession interval. Over 2 weeks, three aphasic subjects participated in a randomized double-blind experiment involving intensive language training for their anomic difficulties in two tDCS conditions. Each subject participated in five consecutive daily sessions of anodic tDCS (20 min, 1 mA) and sham stimulation over Wernickes area while they performed a picture-naming task. By the end of each week, anodic tDCS had significantly improved their accuracy on the picture-naming task. Both normal subjects and aphasic patients also had shorter naming latencies during anodic tDCS than during sham condition. At two follow-ups (1 and 3 weeks after the end of treatment), performed only in two aphasic subjects, response accuracy and reaction times were still significantly better in the anodic than in the sham condition, suggesting a long-term effect on recovery of their anomic disturbances.

Electrical stimulation over the left inferior frontal gyrus (IFG) determines long-term effects in the recovery of speech apraxia in three chronic aphasics

A number of studies have shown that modulating cortical activity by means of transcranial direct current stimulation (tDCS) affects the performance of both healthy and brain-damaged subjects. In this study, we investigated the potential of tDCS for the recovery of apraxia of speech in 3 patients with stroke-induced aphasia. Over 2 weeks, three aphasic subjects participated in a randomized double-blinded experiment involving intensive language training for their articulatory difficulties in two tDCS conditions. Each subject participated in five consecutive daily sessions of anodic tDCS (20 min, 1 mA) and sham stimulation over the left inferior frontal gyrus (referred to as Brocas area) while they performed a repetition task. By the end of each week, a significant improvement was found in both conditions. However, all three subjects showed greater response accuracy in the anodic than in the sham condition. Moreover, results for transfer of treatment effects, although different across subjects, indicate a generalization of the recovery at the language test. Subjects 2 and 3 showed a significant improvement in oral production tasks, such as word repetition and reading, while Subjects 1 and 2 had an unexpected significant recovery in written naming and word writing under dictation tasks. At three follow-ups (1 week, 1 and 2 months after the end of treatment), response accuracy was still significantly better in the anodic than in sham condition, suggesting a long-term effect on the recovery of their articulatory gestures.

tDCS over the left inferior frontal cortex improves speech production in aphasia

In this study, we investigated the combined effect of transcranial direct current stimulation (tDCS) and an intensive Conversational therapy treatment on discourse skills in 12 persons with chronic aphasia. Six short video clips depicting everyday life contexts were prepared. Three videoclips were used to elicit spontaneous conversation during treatment. The remaining three were presented only before and after the therapy. Participants were prompted to talk about the contents of each videoclip while stimulated with tDCS (20 min 1 mA) over the left hemisphere in three conditions: anodic tDCS over the Brocas area, anodic tDCS over the Wernickes area, and a sham condition. Each experimental condition was performed for 10 consecutive daily sessions with 14 days of intersession interval. After stimulation over Brocas area, the participants produced more Content Units, verbs and sentences than in the remaining two conditions. Importantly, this improvement was still detectable 1 month after the end of treatment and its effects were generalized also to the three videoclips that had been administered at the beginning and at the end of the therapy sessions. In conclusion, anodic tDCS applied over the left Brocas area together with an intensive “Conversational Therapy” treatment improves informative speech in persons with chronic aphasia. We believe that positive tDCS effects may be further extended to other language domains, such as the recovery of speech production.

Differential involvement of the left frontal and temporal regions in verb naming: A tDCS treatment study

PURPOSE In aphasic patients, some studies have already emphasized the efficacy of transcranial direct current stimulation (tDCS) during the treatment of noun retrieval deficits. To date, in the same population, there are have been no studies addressing tDCS effects in the recovery of verb retrieval deficits. In this study, we wanted to test the potential of tDCS to improve verb production in a group of aphasic patients. METHODS Seven chronic subjects participated in an intensive language training for their difficulties in action naming. Each subject was treated with tDCS (20 min., 1 mA) over the left hemisphere in three different conditions: anodic tDCS over Wernickes area, anodic tDCS and sham stimulation over Brocas area. Each experimental condition was performed in five consecutive daily sessions over three weeks with 6 days of intersession interval. RESULTS In all patients, results showed a significantly better response accuracy during the anodic tDCS over Brocas area with respect to the other two conditions which still persisted at one month after the end of the treatment suggesting a long-term effect on the recovery of their verb retrieval deficits. CONCLUSION These findings further confirm that tDCS represents a useful new therapeutic interventions for the rehabilitation of lexical deficits in aphasic patients.

Something to talk about: Enhancement of linguistic cohesion through tdCS in chronic non fluent aphasia

Several studies have shown that the modulation of cortical activity through transcranial direct current stimulation (tDCS) enhances naming performance in persons with aphasia. In this study, we investigated the potential effects of tDCS in improving spontaneous speech and the ability to use connective words to establish cohesion among adjacent utterances in a group of eight participants with chronic non fluent aphasia. They were administered five short videoclips representing everyday life contexts and two picture description tasks. Three videoclips were used to elicit spontaneous conversation during the treatment, while the remaining tasks were presented to the patients only before and after the therapy. Patients were required to talk about each videoclip, with the help of a therapist, while they were treated with tDCS (20 min, 1 mA) over the left hemisphere in three different conditions: anodic tDCS over the Brocas area, anodic tDCS over the Wernickes area and a sham condition. Each experimental condition was performed for ten consecutive daily sessions with 14 days of intersession interval. Only after Brocas stimulation, patients showed a greater improvement in producing words that enhanced the cohesion of their speech samples (i.e., pronouns, ellipses, word repetitions, conjunctions). Beneficial effects of the stimulation were generalized also to contexts presented to the patients at the beginning and at the end of the therapy sessions. Our data further confirm the key role of the left inferior frontal gyrus in binding words into a coherent speech. We believe that positive tDCS effects may be further extended to different linguistic domains, useful to promote language recovery.

Bilateral transcranial direct current stimulation language treatment enhances functional connectivity in the left hemisphere: Preliminary data from aphasia

Several studies have already shown that transcranial direct current stimulation (tDCS) is a useful tool for enhancing recovery in aphasia. However, no reports to date have investigated functional connectivity changes on cortical activity because of tDCS language treatment. Here, nine aphasic persons with articulatory disorders underwent an intensive language therapy in two different conditions: bilateral anodic stimulation over the left Brocas area and cathodic contralesional stimulation over the right homologue of Brocas area and a sham condition. The language treatment lasted 3 weeks (Monday to Friday, 15 sessions). In all patients, language measures were collected before (T0) and at the end of treatment (T15). Before and after each treatment condition (real vs. sham), each participant underwent a resting-state fMRI study. Results showed that, after real stimulation, patients exhibited the greatest recovery not only in terms of better accuracy in articulating the treated stimuli but also for untreated items on different tasks of the language test. Moreover, although after the sham condition connectivity changes were confined to the right brain hemisphere, real stimulation yielded to stronger functional connectivity increase in the left hemisphere. In conclusion, our data provide converging evidence from behavioral and functional imaging data that bilateral tDCS determines functional connectivity changes within the lesioned hemisphere, enhancing the language recovery process in stroke patients.

Bihemispheric stimulation over left and right inferior frontal region enhances recovery from apraxia of speech in chronic aphasia

Several studies have already shown that transcranial direct current stimulation (tDCS) is a useful tool for enhancing recovery in aphasia. However, all tDCS studies have previously investigated the effects using unihemisperic stimulation. No reports to date have examined the role of bihemispheric tDCS on aphasia recovery. Here, eight aphasic persons with apraxia of speech underwent intensive language therapy in two different conditions: real bihemispheric anodic ipsilesional stimulation over the left Brocas area and cathodic contralesional stimulation over the right homologue of Brocas area, and a sham condition. In both conditions, patients underwent concurrent language therapy for their apraxia of speech. The language treatment lasted 10 days (Monday to Friday, then weekend off, then Monday to Friday). There was a 14‐day intersession interval between the real and the sham conditions. In all patients, language measures were collected before (T0), at the end of (T10) and 1 week after the end of (F/U) treatment. Results showed that after simultaneous excitatory stimulation to the left frontal hemisphere and inhibitory stimulation to the right frontal hemisphere regions, patients exhibited a significant recovery not only in terms of better accuracy and speed in articulating the treated stimuli but also in other language tasks (picture description, noun and verb naming, word repetition, word reading) which persisted in the follow‐up session. Taken together, these data suggest that bihemispheric anodic ipsilesional and cathodic contralesional stimulation in chronic aphasia patients may affect the treated function, resulting in a positive influence on different language tasks.

Walking but not barking improves verb recovery: Implications for action observation treatment in aphasia rehabilitation

Recent studies have shown that action observation treatment without concomitant verbal cue has a positive impact on the recovery of verb retrieval deficits in aphasic patients. In agreement with an embodied cognition viewpoint, a hypothesis has been advanced that gestures and language form a single communication system and words whose retrieval is facilitated by gestures are semantically represented through sensory-motor features. However, it is still an open question as to what extent this treatment approach works. Results from the recovery of motor deficits have suggested that action observation promotes motor recovery only for actions that are part of the motor repertoire of the observer. The aim of the present experiment was to further investigate the role of action observation treatment in verb recovery. In particular, we contrasted the effects induced by observing human actions (e.g. dancing, kicking, pointing, eating) versus non human actions (e.g. barking, printing). Seven chronic aphasic patients with a selective deficit in verb retrieval underwent an intensive rehabilitation training that included five daily sessions over two consecutive weeks. Each subject was asked to carefully observe 115 video-clips of actions, one at a time and, after observing them, they had to produce the corresponding verb. Two groups of actions were randomly presented: humans versus nonhuman actions. In all patients, significant improvement in verb retrieval was found only by observing video-clips of human actions. Moreover, follow-up testing revealed long-term verb recovery that was still present two months after the two treatments had ended. In support of the multimodal concept representations proposal, we suggest that just the observation of actions pertaining to the human motor repertoire is an effective rehabilitation approach for verb recovery.

''IF TWO WITCHES WOULD WATCH TWO WATCHES, WHICH WITCH WOULD WATCH WHICH WATCH?'' TDCS OVER THE LEFT FRONTAL REGION MODULATES TONGUE TWISTER REPETITION IN HEALTHY SUBJECTS

Recent studies have demonstrated that transcranial direct current stimulation (tDCS) modulates cortical activity in the human brain. In the language domain, it has already been shown that during a naming task tDCS reduces vocal reaction times in healthy individuals and speeds up the recovery process in left brain-damaged aphasic subjects. In this study, we wondered whether tDCS would influence the ability to articulate tongue twisters during a repetition task. Three groups of 10 healthy individuals were asked to repeat a list of tongue twisters in three different stimulation conditions: one group performed the task during anodal tDCS (atDCS) (20 min, 2 mA) over the left frontal region; a second group during cathodal tDCS delivered over the same region; and, in a third group, sham stimulation was applied. Accuracy and vocal reaction times in repeating each tongue twister before, during and 1h after the stimulation were recorded. Participants were more accurate and faster at repeating the stimuli during atDCS than at baseline, while cathodal tDCS significantly reduced their performance in terms of accuracy and reaction times. No significant differences were observed among the three time points during the sham condition. We believe that these data clearly confirm that the left frontal region is critically involved in the process of speech repetition. They are also in line with recent evidence suggesting that frontal tDCS might be used as a therapeutic tool in patients suffering from articulatory deficits.

How Conversational therapy influences language recovery in chronic non-fluent aphasia

The study aimed to determine the efficacy of a Conversational Therapy approach in the treatment of chronic patients with moderately severe non-fluent aphasia. Eight patients completed a six week intensive language training. Every two weeks, each patient received rehabilitation using a different videoclip depicting everyday life. To elicit verbal communication, patients were required to observe each videoclip and to converse about it with the help of an experienced clinician. To measure any significant improvement in speech production all patients were tested before and after treatment. A significant increase in their ability to produce correct informative words (C-Units), verbs, nouns, adjectives, adverbs, as well as closed-class words (pronouns, articles and conjunctions) and well-formed sentences was found after therapy. Such improvement persisted at one week and one month after the end of the treatment. These results suggest that conversational therapy, applied through intensive language training, has a significant efficacy in the recovery of verbal communication in chronic non-fluent aphasic individuals. This approach should be considered for patients with moderately severe non-fluent aphasia, as it enhances not only the ability to use informative language but also its correct use in daily living.