The role of the hippocampus and adjacent medial temporal lobe structures
in memory systems has long been debated. Here we show in humans that these
neural structures are important for encoding implicit contextual information
from the environment. We used a contextual cuing task in which repeated visual
context facilitates visual search for embedded target objects. An important
feature of our task is that memory traces for contextual information were
not accessible to conscious awareness, and hence could be classified as implicit.
Amnesic patients with medial temporal system damage showed normal implicit
perceptual/skill learning but were impaired on implicit contextual learning.
Our results demonstrate that the human medial temporal memory system is important
for learning contextual information, which requires the binding of multiple
cues.
