The present study aims at investigating cognitive functions requiring orbitofrontal control, namely decision-making and facial emotion recognition. The investigators hypothesize that decision-making and facial emotion recognition are impaired in patients with essential tremor (ET) due to frontal lobe dysfunction which may have consequences in daily social life.

Beyond tremor, ET patients display a wide spectrum of clinical abnormalities such as ataxia, deafness, olfactory disturbances, cognitive dysfunction and personality changes. Cognitive dysfunction mainly consists in a dysexecutive syndrome. Personality changes are characterized by increased harm avoidance. These findings suggest a complex modification in frontal lobe function in ET patients, including aspects of dorsolateral and orbitofrontal control. Previous studies have exclusively focused on dorsolateral prefrontal control, while orbitofrontal aspects remain to be elucidated. Orbitofrontal areas are involved in processing emotion and reward, as well as normal social behavior. Dysfunction in these regions may have direct consequences in daily social life.

We hypothesize that decision-making and facial emotion recognition are impaired in ET patients due to frontal lobe dysfunction which may have consequences in daily social life. The first aspect can be assessed with the Iowa Gambling Task, a simple paradigm that simulates real-life decision-making. Briefly, players are given four decks of cards, a loan of $ 2,000 and asked to play so they can lose the least amount of money and win the most. Turning each card carries an immediate reward and sometimes an unpredictable penalty. Decks A and B are the most disadvantageous leading to an overall loss of money, while decks C and D are the most advantageous with an overall gain of money. In contrast to control subjects, patients with damage of the orbitofrontal or ventromedian cortex continue to perseverate with the bad decks, sometimes even though they know that they are losing money overall. The second aspect, i.e. the recognition of facial emotion can be assessed in a simple paradigm where patients have to choose the best fitting response among six facial expressions (happiness, sadness, fear, surprise, disgust and anger) that are presented in random order. All study subjects will be tested with the Benton Visual Retention Test to exclude impairment in visual perception, visual memory or visuoconstructive abilities.

Performances in the Iowa Gambling Task and the facial emotion recognition test will be compared between ET patients and controls. All study subjects will also be tested with the following battery: Modified Card Sorting Test, Stroop, Trail Making Test and Verbal Fluency, Beck Depression Inventory and the Mattis Dementia Rating Scale. These tests will allow assessing the impact of executive function, depression and memory loss on performances in the Iowa Gambling Task and the facial emotion recognition test. Finally, performances in the Iowa Gambling Task and the facial emotion recognition test will be related to sex, age, disease duration and tremor severity.

Inclusion Criteria:

• Patient:

  • Age over 18 years
  • Patient diagnosed as having essential tremor
  • Written informed consent
  • Patient covered by the French health insurance system

• Control:

  • Age over 18 years
  • No diagnosis of essential tremor
  • Written informed consent
  • Subject covered by the French health insurance system

Exclusion Criteria:

• Patient:

  • Dementia (MMSE<24) or other known illness which could impact motor and cognitive performances
  • Patient unable to give written informed consent

• Control:

  • Same exclusion criteria as for patients