New York University researchers have determined that the brain’s hippocampus is important for linking together individual elements of our experiences in order to form memories. Their study, which appears in the latest issue of the journal Neuron, helps to illuminate how something as complex as our memories arises out of a much more simple process of bridging gaps in experience. It may have implications for treating memory-related dysfunction arising from aging, Alzheimer’s Disease, or amnesia.
In order to transform an experience into a memory, the individual, disparate elements of that experience that unfold across space and time need to be somehow linked into a singular memory. Researchers have previously determined that the brain’s hippocampus, which is located in the medial temporal lobe, plays a significant role in memory. But its contributions to linking together individual experiences into a larger, singular memory-or associative memory-had not been well understood.
The NYU researchers, Lila Davachi, an assistant professor in NYU’s Department of Psychology and its Center for Neural Science, and a graduate student in her laboratory, Bernhard Staresina, sought to determine if the hippocampus served as the “glue” needed to connect disparate elements of our experiences in memory.
To explore this dynamic, the study’s subjects were shown a series of visuals composed of different elements-e.g., an object and a background color. Subjects were then asked to recall the object separately and in combination with its associated color. Under some conditions, subjects could only recall the previously presented object (unlinked memory); under others, they were able to remember both the object and its associated color (a linked memory).
The researchers then examined how these memories were encoded by the brain. To do this, they used functional magnetic resonance imaging (fMRI), which gauged which parts of the brain were active under both the unlinked and linked memory conditions. Their results showed that there was significant hippocampus activity when the subjects successfully formed linked memories, but not when the elements were separately encoded.
“Our results show that a core function of the hippocampus is the capacity to bridge gaps between elements of our experiences so that we may later remember them,” explained Davachi. “But they may also explain the role of this portion of brain more broadly in memory and cognition. All kinds of functions, such as spatial navigation, memory, and vivid imagery, depend upon the ability to bridge gaps in our experience and thoughts. If the hippocampus is the glue that holds together our experiences, this can explain the role of this region in other forms of memory and thought.”
The researchers added that the findings may have relevance to understanding, then combating, memory-related afflictions such as age-related memory impairment and Alzheimer’s Disease.
“As we learn more about how the brain forms memories, we can better understand what makes them go awry and then explore behavioral and neurological remedies,” explained Davachi.