“May you live in interesting times” has always been something of a curse, even if the phrase’s exact origins are ambiguous — to live in a time of great unpredictability. We may be living in a pretty stressful time now — amplified by our degree of access to social media that makes disconnecting rather difficult, even if for a brief time, but anxiety has always been a part of the human experience, regardless of what age you might feel nostalgic for. It’s been carried with us throughout most of our evolutionary past, and yet there’s still not a whole lot that we understand about it.
There is both physiological stress — what we feel in bouts of pain or hunger, setting off the brain’s hypothalamus to produce glucocorticoids from our adrenal glands in order to help us cope with our response. For the longest time, scientists believed that subjective stress — our feelings of pressure and anxiety — was somehow always inextricably linked to the former. Now, researchers are less confident that such is always the case, and that the neurobiological origin of subjective stress could come from somewhere else entirely.
Evidence currently suggests that the brain’s hippocampus is somehow involved — the region charged with regulating memory, emotion, and even personal navigation, but the link is still not fully clear. Now a study from researchers at Yale University has sharpened the focus a bit, offering a clearer look into the foundations of stress as they occur in the human brain.
The study recruited 60 healthy adults who were then asked to look at a series of frightening and aversive images that would provoke responses like anger, disgust, fear, or sadness. The disturbing images were complemented with neutral scenes like landscapes in nature meant to make the subjects relax. As they took in the series of images, the participants’ brains were scanned using fMRI technology and numbers were used to rank their reaction to each of the stressful images.
When the researchers pored over their results, they discovered a higher degree of activity between the hippocampus and the hypothalamus. Increased interactions between the parahippocampal cortex (PHC) region of the brain, which is involved in the encoding and retrieval of memory, and the inferior temporal gyrus (ITG) which processes visual stimuli took place whenever the subject felt anxiety coming on.
The researchers were able to establish a connection in which greater activity among the pathways signified greater levels of stress — an example of what neuroscientists call a positive network. An increased degree of interaction between the hippocampus and the cerebellum, however, suggested that the subjects were experiencing less stress.
Somehow, the researchers suspect, an individual’s overall stress level is based on how these connections balance each other out — and that the anxiety that keeps us awake at night may just be a result of rebooting the basic network connections in the brain.
“Despite the distinct roles of these networks, our findings suggest that individuals engaged both positive and negative networks adaptively to attenuate feelings of stress,” noted the study’s co-author Dr. Elizabeth Goldfarb. If, for example, a subject had higher connectivity with negative networks and lower connectivity with positive networks, they would likely report feeling less stress in general. We tend to think of ourselves as better or worse equipped to handle stress based on our own experiences — and sometimes find it hard to believe why people who don’t have the same amount of stressful events in their lives as we do are still somehow less capable of coping with what they have — that they can’t handle a full plate and don’t have nearly the same degree of responsibilities we carry. Perhaps in the near future, that notion may be as dated as thinking our illnesses are based around a balance of the four humors.
“These findings may help us tailor therapeutic intervention to multiple targets, such as increasing the strength of the connections from the hippocampus to the frontal cortex or decreasing the signaling to the physiological stress centers,” explained the study’s senior researcher and neuroscientist Dr. Rajita Sinha.
There’s still a measure of research to be done when it comes to understanding the hippocampus and how it regulates the rest of the body, but this makes the picture somewhat clearer, particularly when it comes to therapy.
