An important aspect of human
memory is our ability to conjure specific moments from the vast array of
experiences that have occurred in any given setting. For example, if asked to
recommend a tourist itinerary for a city you have visited many times, your brain
somehow enables you to selectively recall and distinguish specific memories
from your different trips to provide an answer. Studies have shown that
declarative memory relies on healthy medial temporal lobe structures in the
brain, including the hippocampus and entorhinal cortex (EC). These regions are
also important for spatial cognition. However, it has not been clear if or how
this spatial map in the brain relates to a person's memory of events at those
locations, and how neuronal activity in these regions enables us to target a
particular memory for retrieval among related experiences.
A team led by neuro-engineers at
Columbia Engineering has found the first evidence that individual neurons in
the human brain target specific memories during recall. They studied recordings
in neurosurgical patients who had electrodes implanted in their brains and
examined how the patients' brain signals corresponded to their behavior while
performing a virtual-reality (VR) object-location memory task. The researchers
identified memory-trace cells whose activity was spatially tuned to the location
where subjects remembered encountering specific objects. The team was able to
measure the activity of single neurons by taking advantage of a rare
opportunity: invasively recording from the brains of 19 neurosurgical patients
at several hospitals, including the Columbia University Irving Medical Center.
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