The amygdala is an area of the brain named for its almond shape (amygdala is Latin for almond). The amygdala is necessary for any biologically significant event, or anything related to survival, because of its involvement in decision-making, memory, and emotional responses, including both positive and negative. The amygdala is most commonly known for its role in aversive learning, in which a behavior is taught by pairing it with an unpleasant stimulus. For instance, if you’re trying to train a kitten to only urinate in the litter box, you could spray the kitten with water when they pee on the carpet. Interestingly, the amygdala is also heavily involved in reward learning, where a pleasant stimulus is used to teach a behavior. Going back to our kitten example, you could give the kitten a treat when the it correctly uses the litter box. This bivalent nature of the amygdala, that allows it to be involved in both reward and aversive learning, makes it a key brain area for many researchers, including my lab.
The amygdala images here are all from the same brain, showing different views of the amygdala. The blue marker is DAPI, which is a fluorescent stain that binds to DNA. This blue staining allows researchers to visualize cells. The green in these images is from a virus injected into a subregion of the amygdala called the basolateral amygdala. The first image shows a broad view of the amygdala. This virus is tagged with green fluorescent protein (GFP), which lets us visualize not just the neurons in the basolateral amygdala, but also the projections, or where those neurons are traveling. In the next three images, we have a closer look at the neurons and their projections.
The neurons shown in these images are pyramidal neurons, named for their triangular shaped cell bodies. The “branches” protruding from the cell body are called dendrites; this is where the neuron receives information (such as electrical and chemical signals) from other neurons with which it is connected. The longer extension from the cell body is the axon, through which information is sent when the cell is activated. This axon connects to other neurons’ dendrites, forming what is called a synapse, or a connection between two neurons. These synapses are the basis for communication between neurons, and although small, they are very mighty! The information exchanged at synapses influences not just the neurons involved in the synapse, but also other neurons, brain regions, the brain as a whole, and it is ultimately responsible for our memory, decision-making, movement, and, of course, learning!
Contributed by Maddie Ray, a third year PhD graduate student at Boston College, and our Featured Artist for the fall of 2018. To meet Maddie and see more of her art, click here.
Very nicely written post with beautiful histological photos.
A minor point of correction: “amygdala” as the name of the brain region you’re describing comes from Latin, but it’s actually derived from the Greek word for almond (see https://www.dictionary.com/browse/amygdala).