The brain is a remarkably complex organ comprised of billions of interconnected neurons and glia cells. It controls all functions of the body and interprets information from the outside world. Intelligence, emotion, memory, creativity, and movement are a few of the many things governed by the brain. Some researchers believe that the function of the human brain is best explained by the concept of lateralization, meaning that the right and left hemispheres of the brain perform very different functions, and that the two communicate through their connections. Others believe that the hemisphere of the brain in charge of certain operations is more dependent upon which hemisphere is dominant for the individual.
The left hemisphere is more verbal, analytical, and orderly than the right brain; whereas, the right hemisphere is more visual and intuitive than the left brain. Each hemisphere is in charge of the opposite side of the body, so your right brain controls your left hand, and vice versa. Despite the difference in how they process their information, both hemispheres do not work independently of each other. A structure known as the corpus callosum connects the two hemispheres together enabling communication between them. Dysfunction or absence of the corpus callosum can result in a condition known as split-brain syndrome. Commonly, individuals with split-brain syndrome initially arises from a surgical procedure where the corpus callosum is cut, often when the individual has severe epilepsy. It has been proven to decrease the severity of seizers for individuals with severe epilepsy; however, severing the corpus callosum seems to cause each hemisphere to gain its own consciousness in these individuals that have undergone such a procedure.
Research conducted on split-brain experiments have provided a great deal of insight into the functional asymmetry and inter-hemispheric interactions in the human brain; however, how communication between the left and right hemispheres directly contributes to memory formation is still poorly understood. To address this issue, they cut the corpus callosum in rats’ brains prior to performing behavioral tests, which consisted of two short-term and two long-term memory tasks.The experiment was conducted using male Wistar albino rats that were 11 weeks old at the time of surgery. The corpus callosum was cut using the tip of a razor blade and each rat was allowed to recover for 5 days post-surgery. The two short-term memory tests used included the Novel Preference Test and the Spontaneous Alternation Test. To measure long-term memory functioning the Object Location Test and the Plus-Maze Test were used.
Cutting of the corpus callosum affected memory abilities on the Spontaneous Alternation Test and the Novel Preference Test but did not affect rat’s abilities on the Object Location Test and the Plus-Maze Test; therefore, suggesting that cutting of the corpus callosum does not impair long-term memory. For short-term memory on the other hand, the findings suggest that the left-right hemispheric interaction through the corpus callosum contributes to the appropriate formation of short-term memory. A similar study silenced the excitatory neurons in the right and left CA3 using optogenetics which was found to impair short-term memory, while silencing of the left CA3 and not the right CA3, impaired long-term memory. Based on these finding and this study’s experimental results, the left and right hemispheres interact with each other via the commissural fibers (corpus callosum) to control the formation of short-term memory; on the other hand, only the left hemisphere contributes to long-term memory formation.
Although further research is much needed to deeply understand the connection between the left and right hemispheres and their effect of memory formation, these findings overall help elucidate dynamic memory formation between the two hemisphere and contribute to the development of therapies for some neurological diseases, which cause a reduction in the inter-hemispheric interaction. Their findings act as a guided gateway to new potential discoveries in the future.
Sakaguchi, Y., & Sakurai, Y. (2021, October 4). Disconnection between rat’s left and right hemisphere impairs short-term memory but not long-term memory. MDPI. Retrieved October 23, 2021, from https://www.mdpi.com/2073-8994/13/10/1872/htm.
