Continuous theta burst stimulation over right pars triangularis facilitates naming abilities in chronic post-stroke aphasia by enhancing phonological access

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) has been used experimentally to facilitate naming abilities in individuals with chronic post-stroke aphasia. However, little is known about how rTMS confers clinical improvement, hampering its therapeutic value. The present study investigated the characteristics of naming failure that improve following administration of continuous theta burst stimulation (cTBS)-an inhibitory form of rTMS-to the right pars triangularis (rPTr) in persons with chronic aphasia.

METHODS

Eleven participants with chronic aphasia following left hemisphere stroke named pictures prior to and immediately following cTBS of the rPTr and a control site (vertex) in separate sessions. Prior to stimulation, we obtained two baseline measurements of picture naming ability to determine the extent and type (i.e., phonological vs. semantic) of naming impairment. Items presented for naming during stimulation were those that were named incorrectly in one or both of the baseline sessions (i.e., inconsistent vs. wrong items, respectively). Analyses assessed whether cTBS effects differed depending on the severity and/or type of naming impairment.

RESULTS

Relative to vertex, cTBS of the rPTr improved naming of inconsistent, but not wrong, items for individuals with more severe baseline naming impairment. Critically, baseline phonological but not semantic naming impairment severity marginally correlated with improved accuracy overall, and significantly correlated with decreased phonological errors following rPTr stimulation.

CONCLUSION

CTBS of the rPTr enhances naming by facilitating phonological access during word retrieval, indicating that individuals whose naming impairment is localized to this stage of processing may be most likely to benefit from this rTMS approach.

Ipsilesional neglect: behavioral and anatomical correlates

[Correction Notice: An Erratum for this article was reported in Vol 29(2) of Neuropsychology (see record 2014-42242-001). The funding source information was missing from the author note, and A. M. Barrett's institutional affiliation was incorrect. The funding source information and Barrett's correct institutional affiliation are provided in the erratum.]

OBJECTIVE

The sparse existing research on ipsilesional neglect supports an association of this disorder with damage to the right frontal and subcortical brain networks. It is believed that dysfunction in these networks may result in primarily "aiming" motor-intentional spatial errors. The purpose of this study was to confirm whether frontal-subcortical circuits are indeed commonly affected in ipsilesional neglect and to determine the relative presence of "aiming" motor-intentional versus "where" perceptual-attentional spatial errors in these individuals.

METHODS

We identified 12 participants with ipsilesional neglect based on a computerized line bisection task and used the line bisection data to quantify participants' perceptual-attentional and motor-intentional errors. We were able to discriminate between these 2 biases using the algebraic solutions for 2 separate equations, one for "aiming" and one for "where" biases. Lesion mapping was conducted for all participants using MRIcron software; lesion checklist and overlap analysis were created from these images.

RESULTS

A greater percentage of participants with ipsilesional neglect had frontal/subcortical damage (83%) compared with the expected percentage (27%) observed in published patient samples with contralesional neglect. We observed the greatest area of lesion overlap in frontal lobe white matter pathways. Nevertheless, participants with ipsilesional neglect made primarily "where" rather than "aiming" spatial errors.

CONCLUSION

Our data confirm previous research suggesting that ipsilesional neglect may result from lesions to the right frontal-subcortical networks. Furthermore, in our group, ipsilesional neglect was also strongly associated with primarily "where" perceptual-attentional bias, and less so with "aiming" motor-intentional spatial bias.