THE HIPPOCAMPAL-FORMATION PARTICIPATES IN NOVEL PICTURE ENCODING - EVIDENCE FROM FUNCTIONAL MAGNETIC-RESONANCE-IMAGING

Considerable evidence exists to support the hypothesis that the hippoc ampus and related medial temporal lobe structures are crucial for the encoding and storage of information in long-term memory. Few human ima ging studies, however have successfully shown signal intensity changes in these areas during encoding or retrieval. Using functional magneti c resonance imaging (fMRI), we studied normal human subjects while the y performed a novel picture encoding task. High-speed echo-planar imag ing techniques evaluated fMRI signal changes throughout the brain. Dur ing the encoding of novel pictures, statistically significant increase s in fMRI signal were observed bilaterally in the posterior hippocampa l formation and parahippocampal gyrus and in the lingual and fusiform gyri. To our knowledge, this experiment is the first fMRI study to sho w robust signal changes in the human hippocampal region. It also provi des evidence that the encoding of noveI, complex pictures depends upon an interaction between ventral cortical regions, specialized for obje ct vision, and the hippocampal formation and parahippocampal gyrus, sp ecialized for long-term memory.