In neurodegenerative disorders and psychiatric disorders, cognitive dysfunction is frequently reported. In Parkinson's disease (PD), Multiple Sclerosis (MS) and patients treated with electroconvulsive therapy after a severe or therapy resistant depression (postECT), executive dysfunction, attention deficit or episodic/autobiographic memory deficit is prevalent. In MS and PD, these dysfunctions can appear already early in the disease. The majority of PD patients - lifetime prevalence is about 80% - develops PD dementia. In MS, about half of the patients experiences problems with cognitive functions. ECT is used to treat patients with severe and/or therapy resistant depression. However, 30-50% of these patients develops severe cognitive dysfunction. Recovery usually occurs within six months after ECT. However, performances remain below-average compared to norm groups and there are large individual differences. The cognitive difficulties in MS and PD have a significant negative influence on the quality of life. Cognitive dysfunction in PD is associated with decreased independent daily functioning, hospitalization and the development and severity of neuropsychiatric symptoms. Furthermore, in the clinic cognitive dysfunction has been reported to be one of the most dreadful side effects of ECT. However, effective treatment of the described cognitive dysfunction is still in its infancy.

Cognitive training is based upon the principle that plasticity of the brain can facilitate function improvement by intensive training. In several neurological diseases, cognitive training has shown significant improvement in cognitive functions. In MS and PD, earlier studies have been small, frequently without an adequately controlled design. Additionally, earlier cognitive training programs have frequently been executed in a health care organization, impairing patients to successfully attend all training sessions due to mobility impairments. Also, there are limited studies in the effects of cognitive training on improved functioning of daily living and neuropsychiatric symptoms like anxiety and depression. Given the fact that there is an absence in cognitive training studies in patients post-ECT, there is no knowledge about the ability of cognitive training to speed up the natural course.

Using this pilot study, the investigators aim to study the feasibility of a randomized controlled trial using an online computerized intervention for training cognitive abilities in three patient groups. By using a double-blinded, controlled study design, the investigators keep in mind limitations of earlier comparable studies. If this treatment proves to be feasible, and a rough estimated effect size is positive, a larger randomized controlled trial can be executed to study the effectivity of this treatment. When effects are positive, an online cognitive training programme could prove to be a cost-efficient intervention that is accessible at home - something which is important for patients with mobility problems. The investigators hypothesize that patients using online cognitive training will improve more on cognitive functions, as compared to patients using an active training condition.