Anodal transcranial direct current stimulation (tDCS) is a reliable technique to improve motor learning. We here wanted to test its potential to enhance associative verbal learning, a skill crucial for both acquiring new languages in healthy individuals and for language reacquisition after stroke-induced aphasia. We applied tDCS (20 min, 1 mA) over the posterior part of the left peri-sylvian area of 19 young right-handed individuals while subjects acquired a miniature lexicon of 30 novel object names. Every subject participated in one session of anodal tDCS, one session of cathodal tDCS, and one sham session in a randomized and double-blinded design with three parallel versions of the miniature lexicon. Outcome measures were learning speed and learning success at the end of each session, and the transfer to the subjects' native language after the respective stimulation. With anodal stimulation, subjects showed faster and better associative learning as compared to sham stimulation. Mood ratings, reaction times, and response styles were comparable between stimulation conditions. Our results demonstrate that anodal tDCS is a promising technique to enhance language learning in healthy adults and may also have the potential to improve language reacquisition after stroke.

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Measures of performance on the Trail Making Test (TMT) are among the most popular neuropsychological assessment techniques. Completion time on TMT-A is considered to provide a measure of processing speed, whereas completion time on TMT-B is considered to constitute a behavioral measure of the ability to shift between cognitive sets (cognitive flexibility), commonly attributed to the frontal lobes. However, empirical evidence linking performance on the TMT-B to localized frontal lesions is mostly lacking. Here, we examined the association of frontal lesions following stroke with TMT-B performance measures (i.e., completion time and completion accuracy measures) using voxel-based lesion-behavior mapping, with a focus on right hemispheric frontal lobe lesions. Our results suggest that the number of errors, but not completion time on the TMT-B, is associated with right hemispheric frontal lesions. This finding contradicts common clinical practice—the use of completion time on the TMT-B to measure cognitive flexibility, and it underscores the need for additional research on the association between cognitive flexibility and the frontal lobes. Further work in a larger sample, including left frontal lobe damage and with more power to detect effects of right posterior brain injury, is necessary to determine whether our observation is specific for right frontal lesions.

BackgroundThe Frontal Assessment Battery (FAB) is a brief battery of six neuropsychological tasks designed to assess frontal lobe function at bedside [Neurology 55:1621-1626, 2000]. The six FAB tasks explore cognitive and behavioral domains that are thought to be under the control of the frontal lobes, most notably conceptualization and abstract reasoning, lexical verbal fluency and mental flexibility, motor programming and executive control of action, self-regulation and resistance to interference, inhibitory control, and environmental autonomy.MethodsWe examined the sensitivity of performance on the FAB to frontal lobe damage in right-hemisphere-damaged first-ever stroke patients based on voxel-based lesion-behavior mapping.ResultsVoxel-based lesion-behavior mapping of FAB performance revealed that the integrity of the right anterior insula (BA13) is crucial for the FAB global composite score, for the FAB conceptualization score, as well as for the FAB inhibitory control score. Furthermore, the FAB conceptualization and mental flexibility scores were sensitive to damage of the right middle frontal gyrus (MFG; BA9). Finally, the FAB inhibitory control score was sensitive to damage of the right inferior frontal gyrus (IFG; BA44/45).ConclusionsThese findings indicate that several FAB scores (including composite and item scores) provide valid measures of right hemispheric lateral frontal lobe dysfunction, specifically of focal lesions near the anterior insula, in the MFG and in the IFG.

Background and Objectives A tight link between linguistic functions and activation of motor areas has been consistently reported, indicating that the two systems share functional neural resources. However, little efforts have been made to explore whether this knowledge could aid the rehabilitation of neurological conditions affecting language functions (e.g., aphasia). Moreover, the few previous studies that assessed the impact of motor-language interactions in aphasia used manual gestures, which are an integral component of language comprehension and production. Methods In the present study we assessed whether pre-activation of the leg-motor cortex, during standing vs. sitting, can facilitate language production in chronic aphasia. In a cross-over within-subject design, we assessed performance on a picture naming task and controlled for effects on processing speed and simple verbal reaction time. Results We found that standing compared to sitting had a beneficial effect on the number of semantic self-corrections that resulted in correct naming. In the absence of effects on motor or general processing speed, this points to a specific effect on lexical retrieval and selection. This was further corroborated by an error pattern analysis. Successful semantic self-corrections during standing were only found when there was already partial activation of the target semantic network, i.e., when self-corrections were preceded by an incorrect, but semantically associated naming response. Discussion Our findings show that pre-activation of the motor system, that extends beyond the intrinsic link between manual gestures and language, can facilitate lexical access in chronic aphasia and may open new directions in aphasia rehabilitation.

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Three trail-making tasks were designed to yield measures of visuomotor speed, efficiency of visual search, and cognitive flexibility (attentional switching). Scores on paper-and-pencil trail-making performance tasks were analyzed in 54 neurologically nonimpaired participants (21 men, 33 women; M=40 yr., SD=15 yr.). In Study 1, a 5-item 3-task format of the new trail-making test was developed by selecting items based on psychometric characteristics. The tasks were visuomotor trail-making (one item), visual search (two items), and cognitive flexibility (two items). Estimates of internal consistency of the resulting test scores of the Brunswick Trail Making Test yielded acceptable values (.91 and .90). In Study 2, the effects of repeated practice on trail-making tasks were analyzed. Task repetition affected the performance in the three trail-making tasks differentially. On the visuomotor task, effects of repeated task practice were completely carried over to similar trails. Evidence for transfer of learning was obtained neither for the visual search task nor for the cognitive flexibility task. It is concluded that training effects of perceptual-motor and cognitive skills are highly specific. Implications of these findings for cognitive neurorehabilitation are discussed.