Abstract: Novel uses for 4-phenylbutyrate (4PBA) and its pharmaceutically acceptable salts The use of 4PBA in the manufacture of a medicament useful to treat cognitive disorders in dementias coursing with tauopathies is described. The treatment with 4PBA improves cognitive deficit in a classic murine experimental model of Alzheimer's Disease (AD) (Tg 2576) that is accompanied by decreasing levels of a marker characteristic to AD pathologies, such as phosphorylated Tau, and increasing levels in the synthesis of some synaptic plasticity marker proteins such as GluR1 and PSD95. As mediating mechanism for the therapeutic effect we propose a decreasing stress in the endoplasmic reticulum as manifested by increasing levels of the GRP78 protein. On the other hand its inhibiting effect on histone deacetylation and its involvement in chromatin remodeling facilitates protein synthesis processes, which improves synaptic plasticity.