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NEUROLOGY 2009;72:928-934
© 2009 American Academy of Neurology

Mild cognitive impairment

Loss of linguistic task-induced changes in motor cortex excitability

L. Bracco, MD, F. Giovannelli, PsyD, V. Bessi, MD, A. Borgheresi, MD, A. Di Tullio, RhD, S. Sorbi, MD, G. Zaccara, MD and M. Cincotta, MD

From the Department of Neurological and Psychiatric Sciences (L.B., V.B., A.D.T., S.S.), University of Florence; and the Unit of Neurology (F.G., A.B., G.Z., M.C.), Florence Health Authority, Florence, Italy.

Address correspondence and reprint requests to Dr. Massimo Cincotta, U.O. di Neurologia, Azienda Sanitaria di Firenze, Ospedale Piero Palagi, Viale Michelangiolo, 41, 50125 Firenze, Italy cincotta{at}unifi.it

Background: In amnestic mild cognitive impairment (aMCI), functional neuronal connectivity may be altered, as suggested by quantitative EEG and neuroimaging data. In young healthy humans, the execution of linguistic tasks modifies the excitability of the hand area of the dominant primary motor cortex (M1hand), as tested by transcranial magnetic stimulation (TMS). We used TMS to investigate functional connectivity between language-related cortical areas and M1hand in aMCI.

Methods: Ten elderly women with aMCI and 10 age-matched women were recruited. All participants were right handed and underwent a neuropsychological evaluation. In the first TMS experiment, participants performed three different tasks: reading aloud, viewing of non-letter strings (baseline), and nonverbal oral movements. The second experiment included the baseline condition and three visual searching/matching tasks using letters, geometric shapes, or digits as target stimuli.

Results: In controls, motor evoked potentials (MEP) elicited by suprathreshold TMS of the left M1hand were significantly larger during reading aloud (170% baseline) than during nonverbal oral movements, whereas no difference was seen for right M1hand stimulation. Similarly, MEP elicited by left M1hand stimulation during letter and shape searching/matching tasks were significantly larger compared to digit task. In contrast, linguistic task performance did not produce any significant MEP modulation in patients with aMCI, although neuropsychological evaluation showed normal language abilities.

Conclusions: Findings suggest that functional connectivity between the language-related brain regions and the dominant M1hand may be altered in amnestic mild cognitive impairment. Follow-up studies will reveal whether transcranial magnetic stimulation application during linguistic tasks may contribute to characterize the risk of conversion to Alzheimer disease.

AD = Alzheimer disease; aMCI = amnestic mild cognitive impairment; ANOVA = analysis of variance; FDI = first dorsal interosseous; M1 = primary motor cortex; MEP = motor evoked potentials; MMSE = Mini-Mental State Examination; pvIQ = premorbid verbal intelligence; RMT = resting motor threshold; TMS = transcranial magnetic stimulation.

The Department of Neurological and Psychiatric Sciences, University of Florence, was supported by a grant from Regione Toscana (grant no. 734). The Unit of Neurology of the Florence Health Authority was supported by a grant from Ente Cassa di Risparmio di Firenze, Florence, Italy.

Disclosure: The authors report no disclosures.

Received September 18, 2008. Accepted in final form December 16, 2008.






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