Monday, September 21, 2020

63-year-old man, after gunshot to the head, became “content,” light-hearted, and prone to joking and punning; prior to his brain injury, he suffered from frequent depression and suicidal ideation

Positive Emotions from Brain Injury: The Emergence of Mirth and Happiness. Mario F. Mendez and Leila Parand. Case Reports in Psychiatry, Volume 2020, Article ID 5702578, Jan 29 2020. https://doi.org/10.1155/2020/5702578

Rolf Degen's take: https://twitter.com/DegenRolf/status/1308081276965064706

Abstract: Brain injury can result in an increase in positive emotions. We describe a 63-year-old man who presented with a prominent personality change after a gunshot wound to the head. He became “content,” light-hearted, and prone to joking and punning. Prior to his brain injury, he suffered from frequent depression and suicidal ideation, which subsequently resolved. Examination showed a large right calvarial defect and right facial weakness, along with memory impairment and variable executive functions. Further testing was notable for excellent performance on joke comprehension, good facial emotional recognition, adequate Theory of Mind, and elevated happiness. Neuroimaging revealed loss of much of the right frontal and right anterior lobes and left orbitofrontal injury. This patient, and the literature, suggests that frontal predominant injury can facilitate the emergence of mirth along with a sense of increased happiness possibly from disinhibited activation of the subcortical reward/pleasure centers of the ventral striatal limbic area.


3. Discussion

This patient had a heightened sense of mirth and happiness after his brain injury. The loss of much of his right frontal and right anterior temporal lobes, and damage to left orbitofrontal cortex, altered his personality towards not just silly joking consistent with Witzelsucht but an actual increase in his appreciation of humor. He also maintained a very positive outlook and increased apparent happiness or contentment, per his report. On examination, he was able to detect jokes and identify them as funny, and he consistently described himself as very happy despite his brain injury and situation.

Beyond his joking or “Witzelsucht” from the German words for joke (Witz) and addiction (Sucht) [45], this patient had increased mirth. Mundane experiences and others’ jokes caused him amusement. Investigators have characterized the neurobiology of humor as involving several modular aspect [113]. The first is the cognitive aspect, or getting the joke, namely, the perception of incongruity or of incompatibility between an anticipated perspective and the punchline. Second, with resolution of the incongruity, there is the actual humor appreciation or mirth involving the dopaminergic pleasure/reward centers of the ventral striatum and nucleus accumbens (VS/NA) [1416]. The frontal lobes participate in incongruity detection and resolution, with the left frontal more responsive to simple humor [1618], and the right more engaged with complex humor [141921]. In addition, other regions may contribute to incongruity detection and resolution, such as the temporoparietal junction, the precuneus, the posterior cingulate cortex, and the parahippocampal gyrus [22]. Once incongruity is resolved, the new explanation triggers emotionally pleasurable responses experienced as mirth [914152324]. Since this patient could “get a joke,” his changes appeared at the level of the ease of elicitation of mirth.

The regions associated with the experience of mirth include the VS/NA as well as connections from the anterior cingulate gyrus (ACG), posterior insula, and frontal (left>right) lobe [2528]. Deep brain stimulation of the VS/NA induces mirth and enhances effective connectivity from the ACG to the VS [2526]. As well as promoting surprise, electrical stimulation of the rostral pregenual ACG can also elicit laughter with mirth [272930]. The experience of mirth can occur with the rerepresentation and integration of interoceptive information in the insula [28]. Finally, the frontal lobes trigger humor appreciation through connections with these structures [141620293132].

The formation and regulation of happiness seem to be associated with significant reductions in activity in the right prefrontal cortex, as well as increased activity in the VS/NA [33]. The left frontal lobe may produce a default state biased towards happy or positive interpretations [34]. For example, cortical sites that produce mirth when stimulated tend to be located in the dominant hemisphere close to language areas [3536]. Furthermore, disruption of left frontostriatal emotion regulation systems can impair the ability to suppress positive emotions such as happiness [37]. Together, these findings, as well as the patient’s increased appreciation of humor, suggest that his brain lesion facilitated or released his VS/NA area from any negative input or inhibition. This view must be interpreted cautiously from the analysis of a single patient. There may be other explanations for the patient’s positive emotions, such as the simple relief from depression after his head injury, or as a result of alleviation of stress from no longer functioning as a minister. Nevertheless, his personality change was quite dramatic shortly after recovering from his gunshot wound to the head.

We conclude that positive emotions such as mirth and happiness can emerge from brain lesions and persist. The loss of much of the right frontal and right anterior temporal lobes and damage to the left orbitofrontal cortex facilitated a positive sense of amusement and a positive outlook described as “contentment” by this patient. The literature suggests that this can occur in patients with predominant damage to the right frontal lobe, but also affecting left frontostriatal circuits. These observations warrant further investigation as they speak to the source of positive emotions in humans.

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