Intervention: All patients will receive a multidisciplinary conventional stroke rehabilitation program provided by the rehabilitation staff. The control group will receive a series of cognitive exercises focusing on aspects of memory (visual, auditory, and working memory), attention (sustained attention and selective attention), and executive functioning (planning and problem-solving). The additional training of the trunk training group focuses on trunk muscle strength, coordination and selective movements. The training program will consist of task-specific movements of the upper and lower part of the trunk both in supine and sitting position on stable and unstable surfaces (physio balls). The following trunk exercises will be performed: bridging, reaching, lower/upper trunk rotations, lower/upper trunk lateral flexion, upper/lower trunk flexion, ...