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The Apache Point Observatory Galactic Evolution Experiment (APOGEE) providesspectroscopic information of regions of the inner Milky Way inaccessible tooptical surveys. We present the first large study of the metallicitydistribution of the innermost Galactic regions based on homogeneousmeasurements from the SDSS Data Release 12 for 7545 red giant stars within 4.5kpc of the Galactic center, with the goal to shed light on the structure andorigin of the Galactic bulge.  Stellar metallicities are found, through multiple-Gaussian decompositions, tobe distributed in several components indicative of the presence of variousstellar populations such as the bar, or the thin and the thick disk. Asuper-solar ([Fe/H]=+0.32) and a solar ([Fe/H]=+0.00) metallicity components,tentatively associated with the thin disk and the Galactic bar, respectively,seem to be the major contributors near the midplane. The solar-metallicitycomponent extends outwards in the midplane but is not observed in the innermostregions. The central regions (within 3 kpc of the Galactic center) reveal, onthe other hand, the presence of a significant metal-poor population ([Fe/H]=-0.46), tentatively associated with the thick disk, and which becomes thedominant component far from the midplane ($|Z| > +0.75 kpc). Varyingcontributions from these different components produce a transition region at+0.5 kpc < |Z| < +1.0 kpc characterized by a significant vertical metallicitygradient.

The Bulge Metallicity Distribution from the APOGEE Survey