The orbitofrontal cortex (OFC) is an area of the brain located in the prefrontal cortex, which, as its name suggests, is the front part of the brain. The OFC is my favorite area of the brain, partially because it was the first region I studied, but mostly because of its complex role in motivated behaviors. The OFC is comprised of five subregions: medial, ventral, ventrolateral, lateral, and dorsolateral. Current research is still working to understand each of these subregions and their functions; however, we do know that the OFC is imperative for encoding, updating, and retrieving information about the value of rewards. For instance, if you went to a candy store and ate a large amount of chocolate, so much that you became ill, you will be less likely to visit that candy store later on. The value of the chocolate has been decreased or “devalued” after you overindulged and became sick. Your OFC keeps a running tally of the value of different rewards, including chocolate, so you can make better feeding choices in the future. The OFC’s role in this “devaluation” learning has been studied for decades, but more recent research suggests that this isn’t the OFC’s only role. This brain region is also involved in more complex learning, but its function is still not fully understood.
The images you see here show both a broad and a close-up look at the lateral OFC (lOFC) of rat brains. In the first image, the blue you see is from Dapi, a marker for all neurons. The green comes from a virus that was injected into a separate part of the brain called the Basolateral Amygdala (BLA). There are a lot of connections between the lOFC and BLA, and the green in this image is marking the neurons projecting, or sending information, from the BLA to the lOFC. You can read more about the BLA in my previous post here. The second image shows two hemispheres, or halves, of the brain from two separate rats. The right side of the image came from a rat with a neurotoxic lesion in the lOFC. In this case, a neurotoxin was injected into the lOFC during surgery, which killed all of the neurons in this region. On the left side, you can see a control rat that underwent the same surgery, but no neurotoxin was injected, thus all of the lOFC neurons are intact. This side by side comparison of the two rat brains allows researchers to visualize the extent of the lOFC damage in the lesion rat compared to the intact neurons in the control rat. Lesions are a great tool for understanding the effects of lOFC damage, while viruses can be used to visualize and manipulate the connections between the lOFC and other regions, such as the BLA. These tools are just a few examples of how researchers are continuing to explore the mysteries of the OFC.
If you want to read more about the neurotoxin experiment, that paper is open access and you can find it here.
Contributed by Maddie Ray, a third year PhD graduate student at Boston College, and our Featured Artist for September and October, 2018. To meet Maddie and see more of her art, click here.