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Research paper
Lies tell the truth about cognitive dysfunction in essential tremor: an experimental deception study with the guilty knowledge task
  1. F Mameli1,2,
  2. E Tomasini1,2,
  3. E Scelzo3,
  4. M Fumagalli1,2,
  5. R Ferrucci1,2,
  6. L Bertolasi4,
  7. A Priori1,3
  1. 1Centro Clinico per la Neurostimolazione, le Neurotecnologie ed i Disordini del Movimento, Fondazione IRCCS Ca'Granda–Ospedale Maggiore Policlinico, Milan, Italy
  2. 2Servizio di Neuropsicologia Clinica, Fondazione IRCCS Ca'Granda–Ospedale Maggiore Policlinico, Milan, Italy
  3. 3Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy
  4. 4Dipartimento ad Attività Integrata di Neuroscienze, Azienda Ospedaliera Universitaria Integrata, Verona, Italy
  1. Correspondence to Professor Alberto Priori, Centro Clinico per la Neurostimolazione, le Neurotecnologie ed i Disordini del Movimento, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, University of Milan, Via F. Sforza 35, Milan 20122, Italy; alberto.priori{at}


Background Research conducted in the past decade challenges the traditional view that essential tremor (ET) is characterised exclusively by movement disorder, and increasingly shows that these patients have deficits in cognitive and behavioural functioning. The available evidence suggests that this impairment might arise from dysfunction in either the fronto-subcortical or cortico-cerebellar circuits. Although abnormalities in the fronto-subcortical circuits could imply difficulty in lying, no study has investigated deception in patients with ET.

Aims To examine the cognitive functions regulating deception in patients with ET, we used a computerised task, the Guilty Knowledge Task (GKT). We also tested a group of patients with Parkinson's disease (PD), a disease associated with a known difficulty in lie production, and a group of healthy subjects (HS).

Results In the GKT for deception, patients with ET responded less accurately than HS (p=0.014) but similarly to patients with PD (p=0.955). No differences between groups were found in truthful responses (p=0.488).

Conclusions Besides confirming impaired deception in patients with PD, our results show a lie production deficit in patients with ET also. These findings suggest that difficulty in lying is an aspecific cognitive feature in movement disorders characterised by fronto-subcortical circuit dysfunction, such as PD and ET. Current knowledge along with our new findings in patients with ET—possibly arising from individually unrecognised extremely mild, cognitive difficulties—should help in designing specific rehabilitative programmes to improve cognitive and behavioural disturbances in patients.


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