Memories are popularly considered to originate from brain where they are stored on neural synapses between cells and undergo modifications in response to cellular environment. However, by definition, memory is “a pattern of functional interconnections of cells”. There are numerous ways in which cell-cell connections are established, thus, memories between cells can also be stored in more than one way. Theories suggest that emotions and memories can be stored in the cell membrane of different cells of the body apart from brain. Further, memories can also be transferred from one individual to other through organ transplants.
The concept of “memory” in biological cells has been investigated in organisms such as flat worms and very recently in sea slugs and slime molds. There might be a possibility that just like these organisms, cellular memory is transferred in human beings as well. There have been 1,2 on changes in personality traits, food preferences, music choices, physical activities and even sex preference in individuals that have undergone organ transplants. These changes in the recipient follow their donor’s personality characteristics. Thus, supporting the possibility that memories stored in the donor cells are transferable into recepient body during an organ transplant.
Along the lines, a recent paper published in the Journal Medical Hypotheses discusses the acquisition of personality characteristics like changed preferences, alteration in emotions or temperament, modifications of identity and memories from the donor, in the recipients following a heart transplant. Since there are suggestions of non – cognitive cellular memory, it is likely that the individual cells present in the donated organ carry these memories in one way or the other. Inside every cell there are specialised structures called organelles that perform various functions. Fundamentally these organelles involve macromolecules such as – DNA, RNA and Protein to perform specialised functions. Further, the process of formation, consolidation and execution of memory is facilitated by interplay of these macromolecules. For example when a particular memory is formed in response to a stimulus, it requires various proteins such as receptors on surface muscle cell that receive the stimulus , ion channels / transport proteins that facilitate transport of ions and molecules across cell membrane thus converting this stimulus into electrical impulses that are finally interpreted in brain and stored as memory. Similarly execution or recalling of memory as well requires this interplay of different proteins in which brain generates response in form of electrical impulses by movement ions through transport proteins located in cell membrane. This electrical impulse is then converted into a mechanical or behavioural response via proteins and other macromolecules that make up muscular, skeletal and hormonal system of body. Proteins required in all the above steps are coded by genes located on DNA via RNA. This expression of proteins can be controlled by different mechanisms in different cells. There is a-likelihood that transcriptional state of cells, the type of -protein receptors, their distribution and the way in which their expression is regulated is transferred from a donor to recepient through cells present in donated organ. There have been reports where memory has been been transferred from a trained marine snail to an untrained one through RNA injections suggesting that this transfer of RNA induced certain epigenetic non synaptic changes that resulted in new behaviour responses in these animals.
When memory is formed it requires perception of a physical stimulus from the surrounding. This perception requires receptor proteins such as those on muscle cells that can receive stimuli from the environment, movement of ions via ion channels / transporters (type of proteins) across cell membrane that convert these signals into electrical impulses to be finally interpreted by brain. Similarly the execution or recalling of memory also requires signalling via membrane associated channels and receptors to produce a response such as behaviour changes, perceptions, neural activity etc. These signalling steps require gene expression that can result in proteins that are required to modify neuronal connections that can form and regulate memory. Thus epigenetic pattern on DNA or protein arrangement present in cells of transplanted organ can act as a storehouse of memory per se.
Memories are dynamic in the sense that they can be made, remembered, modified, distorted and even forgotten. This requires a collaborative function of memory associated genes, transcripts, protein channels and transporters present in neurons and surrounding cells. Thus there is a likelihood that this pattern of aforementioned molecules when transferred to a new individual in case of transplant of organ such as heart, result in establishment of new memories. However if this is true, more convincing studies are required to establish exact nature of this transfer of memories. Study of cell memory and its implications can enable a better understanding on how they are transferred and what role they have to play in the donated organ being accepted and integrated into the recepient system.