  We present a study of the spatial and redshift distributions of Sloan Digital
Sky Survey (SDSS) galaxies toward the position of CrB-H, a very deep and
extended decrement in the Cosmic Microwave Background (CMB), located within the
Corona Borealis supercluster (CrB-SC). It was found in a survey with the Very
Small Array (VSA) interferometer at 33 GHz, with a peak negative brightness
temperature of -230 muK, and deviates 4.4-sigma from the Gaussian CMB
(G\'enova-Santos et al.). Observations with the Millimeter and Infrared Testa
Grigia Observatory (MITO) suggested that 25$^+21_-18% of this decrement may be
caused by the thermal Sunyaev-Zel'dovich (tSZ) effect (Battistelli et al.).
Here we investigate whether the galaxy distribution could be tracing either a
previously unnoticed galaxy cluster or a Warm/Hot Intergalactic Medium (WHIM)
filament that could build up this tSZ effect.
  We find that the projected density of galaxies outside Abell clusters and
with redshifts 0.05<z<0.12 at the position of CrB-H is the highest in the area
encompassed by the CrB-SC. Most of these galaxies are located around redshifts
z=0.07 and z=0.11, but no clear connection in the form of a filamentary
structure is appreciable in between. While the galaxy distribution at z=0.07 is
sparse, we find evidence at z=0.11 of a galaxy group or a low-mass galaxy
cluster. We estimate that this structure could produce a tSZ effect of ~ -18
muK. The remaining VSA signal of ~ -212 muK is still a significant 4.1-sigma
deviation from the Gaussian CMB. However, the MITO error bar allows for a
larger tSZ effect, which could be produced by galaxy clusters or superclusters
beyond the sensitivity of the SDSS. Contributions from other possible secondary
anisotropies associated with these structures are also discussed.
