Patients treated for breast cancer frequently complain of sleep disturbances, about 40% of them. Of the sleep disturbances experienced by patients, insomnia is the most common complaint. The prevalence of insomnia complaints is higher in breast cancer patients compared to other types of cancer, and is also higher than in the general population (between 20% and 70% in breast cancer patients vs 30% in the general population). A recent study indicates that sleep complaints concern 25% of patients even before diagnosis, and 46% (including 18% complaining of insomnia) at the time of diagnosis, showing the negative impact of the announcement of the pathology on the subjective quality of sleep, and particularly on symptoms suggestive of insomnia. However, objective information on a modification of sleep patterns in breast cancer remains scarce and does not allow us to conclude. In particular, previous studies have focused only on the effects of chemotherapy and have not always included a control group, limiting the significance of their results. The links with cognitive and psychopathological processes and the underlying mechanisms are not clearly demonstrated in this pathology. Finally, taking into account patients' complaints, it appears necessary to limit sleep disorders in breast cancer in order to improve patients' quality of life using non-medicinal and easy-to-implement approaches.

Inclusion Criteria:

• Patients aged 39 to 69 years
• Patient with operated localized breast cancer who may or may not be starting adjuvant chemotherapy
• Patient with education level 3 "end of primary education"
• Patient with a good command of the French language
• Patient with access to the Internet from a computer at home
• Patient having signed the consent to participate in the study
• Patient with no pre-existing cognitive impairment at the time of cancer diagnosis
• Patient with a sleep complaint (ISI > 7)

Exclusion Criteria:

• Patient with metastatic cancer
• Patient with a primary cancer other than breast cancer
• Patient with a history of neurological damage
• Patient with treated sleep apnea
• Patient with drug use or alcohol abuse (≥3 drinks/day on average and/or >10 drinks/week)
• Patient with a treatment that has not been stabilized for at least 3 months (hypnotics, antidepressants, anxiolytics)
• Patient with a personality disorder and/or an evolving psychiatric pathology
• Patient with a contraindication to MRI (claustrophobia, metallic objects in the body)
• Patient with an uncorrected vision problem