Why do we cry? (Part 2)

The crying was associated with a sorrowful facial expression, sobbing body movements, and a voice inflected with sadness. These physical manifestations ended with the termi- nation of stimulation and the patient described feeling sad, but could not express the trigger for the sadness or crying. Results were consistent and reproducible.

I have previously wondered why we cry, from a biological perspective. When I went looking for reasons, I found a paucity of actual evidence. However, in a link from a recent report on sticking electrodes in people I found a study that was able to induce crying. Causing a person to cry by electrically stimulating a part of the brain is about as good as you can get, right? Then you have causal evidence that that region is intimately involved in that behavior.

To recap, when an epileptic patient needs surgery, an electrode will often be stuck in the brain in order to localize the source of the seizures. Scientists are always thrilled about this because it’s next to impossible to get an electrode in a human brain otherwise, and how else are we to study human-specific behavior? So they get into these operations and zap portions of the patient’s brain to see what it does – and what qualitative feelings the patient experiences.

One recent such zapping managed to reliably produce crying in a patient – and not just crying, but crying with a feeling of sadness. This isn’t like what I had reported previously, where crying was the result of very deep areas that may not be directly linked to ’emotion’. The area of the brain they were stimulating was the ‘left posterior orbito-frontal gyrus’, which is a region of orbitofrontal cortex and looks to me like it may overlay the ventromedial (or perhaps ventrolateral) prefrontal cortex? This area has strong connections with amygdala and hypothalamus, as well as other reward-related areas.

So activation of this area of orbitofrontal cortex is sufficient to induce crying and sadness. But is the crying directly caused by this stimulation? Or is it indirectly induced by the feeling of intense sadness? I’ll admit to being pretty interested in what the pathway is here, and then: what is the pathway that causes this area to activate?

Also, three cheers for the surgeon whose job it was to repeatedly and remorselessly cause this patient to cry and feel intense sadness!

References

Burghardt T, Basha MM, Fuerst D, & Mittal S (2013). Crying with sorrow evoked by electrocortical stimulation. Epileptic disorders : international epilepsy journal with videotape, 15 (1), 72-5 PMID: 23531727

Why do we cry?

I was recently reading an article on the psychology of why we cry (via):

In a study published in 2000, Vingerhoets and a team of researchers found that adults, unlike children, rarely cry in public. They wait until they’re in the privacy of their homes—when they are alone or, at most, in the company of one other adult. On the face of it, the “crying-as-communication” hypothesis does not fully hold up, and it certainly doesn’t explain why we cry when we’re alone, or in an airplane surrounded by strangers we have no connection to…

In the same 2000 study, Vingerhoet’s team also discovered that, in adults, crying is most likely to follow a few specific antecedents. When asked to choose from a wide range of reasons for recent spells of crying, participants in the study chose “separation” or “rejection” far more often than other options, which included things like “pain and injury” and “criticism.” Also of note is that, of those who answered “rejection,” the most common subcategory selected was “loneliness.”…

Although biological reasons have been proposed, they often seem a bit silly to me. So I tried to dig into the neurobiology literature – and found just about nothing. It’s actually kind of hard; there’s basically nothing, so far as I can tell. What do we know about the neurobiology behind this intensely social behavior?

There are clues from a paper in 2001 crying is somehow related to laughter. Some people suffer from a neurological disorder known as pathological laughter and crying which is exactly what it sounds like: crying at a moderately sad movie or laughing uncontrollably when frustrated. Here is a video of someone with pathological laughter, and here is another video explaining it (and the connection with MS). This is not so surprising when you think about it. After all, who doesn’t know someone who has cried from happiness or laughed at something sad?

These two things may be linked because they are part of a proposed ‘laughing and crying center’ of the brain, located in the brainstem. In fact, anyone who suddenly begins pathologically laughing should be careful as it is a warning sign of a brainstem stroke. This emotional center probably receives input from the cerebellum; a patient who had a lesion in the cerebellar peduncle, which sends information from the cerebellum to the brainstem, was a pathological laugher and cryer. The authors suggest that the cerebellum usually integrates all sorts of social cues to guide behavior but when it cannot do it’s job properly laughing and crying occur inappropriately.

The cerebellum is an accordion-like structure that often gets accused of being a primitive lizard brain. Whenever a structure looks old, people assume it’s archaic and can’t have evolved to do anything new. But the cerebellum has more than three times as many neurons as the whole neocortex, and is responsible for a lot that it doesn’t get credit for. Other portions of the brain that are involved in emotion and social behaviors, such as the serotonin-producing raphe nuclei and the hypothalamus, send information to the cerebellum and damage to the cerebellum is linked to disinhibited and inappropriate social behavior, as well as a generally lower intellect.

The moral of the story is that crying is a response to all kinds of social cues which psychologists are equipped to study while neuroscientists are unable to. About all we can say is that a structure that coordinates social input is playing an intricate role in controlling tears.

Update: I have a new blog post with a little more information. Apparently, stimulating the orbitofrontal cortex – a region connecting to the ’emotion center’ of the amygdala, while also dealing with (positive and negative) reward – is able to cause crying and feelings of sadness.

Reference

Parvizi J, Anderson SW, Martin CO, Damasio H, & Damasio AR (2001). Pathological laughter and crying: a link to the cerebellum. Brain : a journal of neurology, 124 (Pt 9), 1708-19 PMID: 11522574