Figure 1. Schematic diagram of the radiofrequency ablation device, adapted from surgical oncology procedures to apply a focal high frequency alternating current to the region of the amygdala.
Alternatively, a gamma knife-like TMS application, slyly incorporated into a metal detector, temporarily deactivates the amygdala when each customer enters the casino.
Figure 2. Adjustable transcranial magnetic stimulation (TMS) helmet incorporated into a Metor 200 Walk-Thru Metal Detector.
What was the inspiration for such ground-breaking technology?1 The revelation that two rare individuals with bilateral lesions of the amygdala2 did not care about losing large sums of money in a gambling task (De Martino et al., 2010). This comes as no surprise, really, since the same two patients (S.M. and A.P.) do not show fear in other contexts. Patient S.M. in particular has repeatedly demonstrated deficits in the perception of fear (reviewed in Adolphs, 2008). She's more likely to judge unfamiliar faces as trustworthy and approachable (Adolphs et al., 1998). Further, she fails to show a normal sense of distrust and "danger" (Tranel et al., 2006), and:
Her interpersonal behaviour is notable for a somewhat coquettish and disinhibited style. She tends to be friendly with her examiners, with a familiar style of interaction that goes a little beyond what is typical in conventional Midwestern culture.In a related vein, her requirement for personal space is non-existent (Kennedy et al., 2009). On the other hand, she's impaired at making eye contact with people during conversations (Spezio et al., 2007). Although fearful facial expressions are a mystery, she can accurately judge fear from whole-body cues (Atkinson et al., 2007). Hmm. I find it puzzling when investigators publish a paper that stands in relative isolation from their previous work, as if the current result is so novel that it merits placement in a high-profile journal.
So what does all this uncited work have to do with "loss aversion", the well-studied behavioral economic phenomenon3 probed in the current study? The authors proposed that "the amygdala computes a signal of prospective loss that is integrated with other information to guide behavioral choice" (De Martino et al., 2010). How does this fit with the collection of findings mentioned above? Granted, constraints of the short, high-impact journal article format prevent in-depth discussion and integration, but presenting so many punctate disconnected pieces just to up your number of glamor publications can be viewed as a disservice to the field. In my opinion, it's important to make connections between the different functions carried out by a particular brain structure (or network of structures), rather than treating the computations performed in a specific task as somehow uninformed by these other "computations".
Adolphs et al. (2005) tied some of the disparate fear findings together when they linked S.M.'s lack of eye contact to her impaired recognition of fear from faces. But how does this connect with her propensity to throw money away in Vegas? More broadly, do pathological gamblers show amygdala-like deficits similar to S.M.? Probably not. Ultimately, the casinos don't care whether it's due to alterations in the striatum, the ventromedial prefrontal cortex, or the amygdala, they'd just like to attract customers with lowered loss aversion...
1 In case it's not completely obvious, these are fictional techniques.
2 The cause of the amygdala damage was Urbach-Wiethe disease, a rare genetic disorder with less than 300 reported cases.
3 To learn more about loss aversion in neurological patients, I refer the reader to this post in The Frontal Cortex.
Adolphs R. Fear, faces, and the human amygdala. (2008). Curr Opin Neurobiol. 18:166-72.
Adolphs R, Tranel D, Damasio AR. (1998). The human amygdala in social judgment. Nature 393:470-4.
Adolphs R, Gosselin F, Buchanan TW, Tranel D, Schyns P, Damasio AR. (2005). A mechanism for impaired fear recognition after amygdala damage. Nature 433:68-72.
Atkinson AP, Heberlein AS, Adolphs R. (2007). Spared ability to recognise fear from static and moving whole-body cues following bilateral amygdala damage. Neuropsychologia 45:2772-82.
De Martino, B., Camerer, C., & Adolphs, R. (2010). Amygdala damage eliminates monetary loss aversion. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0910230107
Kennedy DP, Gläscher J, Tyszka JM, Adolphs R. (2009). Personal space regulation by the human amygdala. Nat Neurosci. 12:1226-7.
Spezio ML, Huang PY, Castelli F, Adolphs R. (2007). Amygdala damage impairs eye contact during conversations with real people. J Neurosci. 27:3994-7.
Tranel D, Gullickson G, Koch M, Adolphs R. (2006). Altered experience of emotion following bilateral amygdala damage. Cogn Neuropsychiatry 11:219-32.
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