The article states that when it comes to the formation of long-term memory, it is accepted that it is formed by the strength of the synapse (space between two neurons). Neurons are the cells in our brain that retrieve and send information throughout our body. There is a theory that long-term memory is actually encoded by changes in gene expression or epigenetics. This modification is not due to inheritance but to the activation or deactivation of the gene itself. This phenomenon may be mediated by RNA. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay The researchers chose to test this theory by taking RNA from a trained animal and inserting it into an untrained animal to see if it generates the same long-term memory as the trained animal. They used Aplysia sea snails for the study. The training involved Aplysia undergoing long-term sensitization. In this process, repetition of a stimulus will cause an enhanced reaction over time, becoming more sensitive to the stimulus. The Aplysia were placed in separate tanks and all had their tails implanted bilaterally with Teflon-coated platinum wires. They sensitized the Aplysia's withdrawal-siphon reflex by lightly stimulating the tubular portion of the Aplysia known as the siphon with a herb stimulator. This reflex consists in retracting the siphon when disturbed. Three pre-tests were administered to the sensitized Aplysia 25 minutes before training, once every 10 minutes. For training, the duration of the reflex was timed and recorded twice with an interval of twenty-four hours between them. Five cycles of shocks were administered at twenty-minute intervals and a post-test was performed twenty-four hours later. For the RNA injection portion of the test, untrained animals were given three pre-tests like trained animals before the injection, followed by a post-test twenty-four hours later. To prepare for RNA injection, four to five trained and four to five untrained animals had their pleural and abdominal ganglia removed. The RNA was then removed from the ganglia and homogenized. It was then centrifuged to separate the upper aqueous phase containing the RNA nucleic acids. All the RNA from the trained animals was combined into one tube and the same goes for the RNA from the untrained animals. Each animal was injected with 70 ug of trained or untrained RNA. Electrophysiological measurements were made from pleural sensory neurons and small siphon motor neurons that were separated from the animals in cell culture. Each cell culture could have had sensory neurons or motor neurons, or a synaptic coupling of the two. Separated neurons remained in culture for five days while synaptic paired neurons remained in culture for three days before recording. They were recorded by impaling them with micropipettes filled with 1.5 M potassium acetate, 0.5 M potassium chloride, and 0.01 M HEPES. This would allow the voltage to be recorded by a molecular device and digitized for analysis. Action potential threshold was determined by injecting current of 2 s at incremental intensity levels. Sensory neurons whose resting membrane potential was more depolarized than −35 mV were excluded. Motor neurons whose membrane potentials were more depolarized than −30 mV were also excluded. Their excitability was recorded by sending positive current pulses of 0.1, 0.2, or 0.3 nA..