In the phenomenology of dementia, the cognitive symptoms surround most of the interests both for investigators as clinicians. However, the non cognitive symptoms are shown so often they should become a major one in the clinical evaluation of the dementia syndrome. Moreover, the presence of this symptoms means more clinical severity, increases the institutionalization risk and causes a larger emotional burden for demented carers. On this work, the authors argue about the possible physiopathogenic causes related to cognitive and non cognitive aspects of dementia.