title: Impairment of sensory-motor plasticity in mild Alzheimer's disease.
abstract: BACKGROUND
  Primary motor cortex (M1) is relatively spared in the early stages of Alzheimer's disease (AD).
  
  
  OBJECTIVE
  Aim of the present study was to investigate whether abnormal M1 synaptic plasticity is present at an early stage of AD. We employed an electrophysiological protocol, named rapid paired associative stimulation (rPAS), involving repetitive transcranial magnetic stimulation (rTMS) paired with electrical stimulation of the contralateral median nerve, that modifies corticospinal excitability and short latency afferent inhibition (SAI).
  
  
  METHODS
  We studied 10 patients with a diagnosis of probable mild AD according to the Mini Mental State Examination score (minimum 21) and 14 age-matched control subjects. Motor evoked potentials (MEP) amplitudes and short-afferent inhibition (SAI) were measured at baseline before and for up to 60 min after 5Hz-rPAS in abductor pollicis brevis (APB). rPAS consisted of 600 pairs of transcranial magnetic stimuli, at a rate of 5 Hz for 2 min, coupled with electrical median nerve stimulation preceding TMS over the contralateral M1 at an inter-stimulus interval of 25 ms.
  
  
  RESULTS
  Baseline SAI was significantly reduced in AD patients. In the control subjects rPAS induced a significant increase in MEP amplitudes and a decrease of SAI in the APB muscle persistently for up to 1 h. Conversely 5Hz-rPAS did not induce any significant changes in MEP amplitudes and SAI in mild AD patients.
  
  
  CONCLUSIONS
  Sensory-motor plasticity is impaired in the motor cortex of AD at an early stage of the disease.
authors.affiliation: Dipartimento di Neuroscienze, Scienze Psichiatriche ed Anestesiologiche, Università di Messina, Italy.
authors.forename: Carmen
authors.initials: C
authors.lastname: Terranova
authors.forename: Terranova
authors.initials: T
authors.lastname: Carmen
authors.forename: Antonino
authors.initials: A
authors.lastname: SantAngelo
authors.forename: Sant'Angelo
authors.initials: S
authors.lastname: Antonino
authors.forename: Francesca
authors.initials: F
authors.lastname: Morgante
authors.forename: Morgante
authors.initials: M
authors.lastname: Francesca
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Rizzo
authors.forename: Rizzo
authors.initials: R
authors.lastname: Vincenzo
authors.forename: Roberta
authors.initials: R
authors.lastname: Allegra
authors.forename: Allegra
authors.initials: A
authors.lastname: Roberta
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Arena
authors.forename: Arena Maria
authors.initials: AM
authors.lastname: Grazia
authors.forename: Lucia
authors.initials: L
authors.lastname: Ricciardi
authors.forename: Ricciardi
authors.initials: R
authors.lastname: Lucia
authors.forename: Marie Felice
authors.initials: MF
authors.lastname: Ghilardi
authors.forename: Ghilardi Maria
authors.initials: GM
authors.lastname: Felice
authors.forename: Paolo
authors.initials: P
authors.lastname: Girlanda
authors.forename: Girlanda
authors.initials: G
authors.lastname: Paolo
authors.forename: Angelo
authors.initials: A
authors.lastname: Quartarone
authors.forename: Quartarone
authors.initials: Q
authors.lastname: Angelo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000503:physiopathology*; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation