More hints. LTP was another possibility. High frequency stimulation of the dendrites of a neuron were known to improve the sensitivity of the synaptic nerve junctions. Such activity was seen to be "remembered" by the cell through greater sensitivity at specific inputs. Neurochemicals at the synaptic junctions were also known to increase such sensitivity. But, while the process enhanced memory, LTP failed to offer a global hypothesis about how memory could be stored.
Without answers. The hippocampus was also mentioned in connection with memory research. Damage to this organ, a component of a region of the brain called the limbic system, was known to cause patients to forget ongoing events within a few seconds. But, incidents from childhood and early adult life were still remembered. Memory had faded from a couple of years prior to the event that caused damage to the hippocampus. Older memories were still retained by the patient even without the hippocampus. Evidently, the organ did not store such memories. It could play a role, but the actual storage of memory remained enigmatic. In the end, all science did know was that memory resided all over the system and that one particular organ helped the formation of memories.
Combinatorial coding. Yet, the answer to the memory enigma had been staring them in the face for years. That happened, when science acknowledged the use of combinatorial coding by nerve cells in the olfactory system. Combinatorial coding sounded confusing and complex. But, in the context of nerve cells, combinatorial coding only meant that a nerve cell recognized combinations. If a nerve cell had dendritic inputs, identified as A, B, C and so on to Z, it could then fire, when it received inputs at ABD, ABP, or XYZ. It recognized those combinations. ABD, ABP, or XYZ. The cell could identify ABD from ABP. Subtle differences. Such codes were extensively used by nature. The four "letters" in the genetic code