Whether these new connections and changes are permanent is the subject of continuing research. For a rat, reaching for and grasping food is a learned behavior that takes time and repetition to master, not unlike a person learning to ride a bike or play the piano. If the behavior isn't regularly practiced, it becomes rusty, though it may be later resumed and remembered.
"This seems to be a 'hard-wired' form of memory," said Tuszynski. "We were curious whether we could find evidence of hard-wiring as part of learning in animal brains. We designed this study and our original hypothesis seems to be confirmed.
"Whether this physically represents the formation of long-term memory is hard to say" Tuszynski said, explaining that the data are correlative. "The rats learn, and we know that the learning is mediated by the small set of cells we studied. We know that adjacent cells in the cortex, which are not required to learn the new task, do not show the structural change. So presumably the structural change is occurring only in the learning neurons, and the learning would likely not occur without the structural change."
He added that in order to determine whether the structural change is necessary for the learning to occur, scientists would need to block the expansion in spines and then observe a failure to learn. "Yet the inference is quite strong that structural change is necessary for the learning to occur."
Tuszynski said it remains to be seen how the brain changes in other types of learning, such as language-based knowledge or arithmetic-type learning.
"Types of memory that require much repetition for learning and that don't fade away easily likely use this modification of (dendritic) structure to accomplish the learning," he
|Contact: Scott LaFee|
University of California - San Diego