Linguistic irregularities in number naming systems, such as the inversion of number words, affect the processing of Arabic numerals. Recently, it has been claimed that there is even a syntactic representation of number words. participant investigate the neurofunctional correlates of the syntactic processing of number words by examining different levels of place-value processing in a study with two complementary successive phases (Group 1 and Group 2) in healthy adults. In the first phase with Group 1, participant evaluate the unit-decade compatibility effect (UDCE) in two-digit magnitude comparisons. In the second phase with Group 2, participant investigate the carry-over effect in two-digit addition problems.

Selection visit

• Call for participants for pre-selection

• Sending of information forms by mail

• Making an appointment for the inclusion visit at GHU Paris

• Information on the modalities, constraints and foreseeable risks of the study

• Collection of informed consent

• Verification of inclusion/non-inclusion criteria

• Clinical examination:

  • Verification of medical history and drug treatments
  • Psychiatric pathology
  • Consumption of toxic substances (nicotine, alcohol, cannabis, etc.)
  • Manual lateralization will be assessed by the score on the Edinburgh questionnaire (Oldfield, 1971)

• Collection of main medical history and concomitant treatments

• Explanation of study procedures

• MRI examination

Inclusion Criteria:

• Subject aged 18 to 45 years;
• Female or male;
• Right-handed preference;
• Subject, or legal representative, who has given consent to participate;
• Native language: French
• Subject affiliated with a social security system;
• Having signed their consent to participate (and their legal representative if applicable),
• Subjects have read the information letter and given their free and informed consent;
• Normal medical, neurological, and neuroradiological examinations
• For women of childbearing age, be on effective contraception

Exclusion Criteria:

• Not corresponding to the targeted age range;
• Subject with contraindications to an MRI examination (pacemaker or neurosensory stimulator or implantable defibrillator, cochlear implants, ferromagnetic foreign bodies in the eyes or brain near neural structures, metal prostheses, patient agitation: non-cooperative or agitated patients, minors, claustrophobic subjects, pregnant women, ventriculoperitoneal neurosurgical shunt valves, dental braces);
• Subject with chronic alcohol or drug use;
• Abuse or dependence on substances (except nicotine) or toxic substances for more than 5 years or having led to comas (overdoses);
• Subject with sudden-onset cognitive disorders that could indicate a stroke; a history of head trauma with loss of consciousness for more than 1 hour, or encephalitis;
• Subject with chronic neurological, psychiatric, endocrine, hepatic, or infectious conditions;
• Subject with a history of major illness (diabetes, chronic lung disease, severe cardiac, metabolic, hematological, endocrine, or immunological disorder, cancer);
• Subject on medication: taking medications likely to interfere with brain imaging measurements (psychotropics, anxiolytic hypnotics, neuroleptics, anti-Parkinsonians, benzodiazepines, steroidal anti-inflammatories, antiepileptics, central analgesics, and muscle relaxants);
• Color blindness;
• Inability to comply with the study for geographical or psychiatric reasons;
• Tattoo incompatible with MRI;
• Cerebral palsy;
• Fine motor skills disorder;
• Pregnant women at the time of inclusion;
• Adult subjects under legal protection or unable to give consent (article L.1121-8 of the French Public Health Code) (under guardianship or curatorship);
• Children and parents under legal protection measures

In the experimental phase, 42 adult volunteers (a total of 84), selected according to strict criteria, will undergo an MRI scan, each comprising: - anatomical acquisition, - functional acquisition of activation during a number processing task (Phase 1: two-digit number magnitude comparison; Phase 2: multi-digit mental arithmetic).