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Machine learning of neural representations of emotion identifies suicidal youth

methodsman.com

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Re: Machine learning of neural representations of emotion identifies suicidal youth

#11

Post by asperous »

nieve wrote: post #4

"This study used machine-learning algorithms (Gaussian Naive Bayes) to identify such individuals (17 suicidal ideators versus 17 controls) with high (91%) accuracy, based on their altered functional magnetic resonance imaging neural signatures of death-related and life-related concepts." Anyone with a Nature subscription want to check whether they simply trained their discriminator and then used it on the same data s…

"On each fold, the trained classifier was tested on the data of the left-out participant. This procedure was reiterated for all 34 possible ways of leaving out one participant, yielding 34 classifications whose averaged accuracies are reported."

Sounds like they overfit their cross validation score and reported that. The data is actually available here though:

http://www.ccbi.cmu.edu/Suicidal-ideation-NATHUMBEH2017/

Re: Machine learning of neural representations of emotion identifies suicidal youth

#12

Post by onetwotree »

nieve wrote: post #4

"This study used machine-learning algorithms (Gaussian Naive Bayes) to identify such individuals (17 suicidal ideators versus 17 controls) with high (91%) accuracy, based on their altered functional magnetic resonance imaging neural signatures of death-related and life-related concepts." Anyone with a Nature subscription want to check whether they simply trained their discriminator and then used it on the same data s…

17 subjects per group is extremely small.

Looking at it either from a machine learning or statistical point of view, using such a small sample is problematic.

This is the chronic issue with fMRI studies, since administering an fMRI is extremely expensive, and has led to some very difficult to reproduce results in the field.

Re: Machine learning of neural representations of emotion identifies suicidal youth

#13

Post by drdaeman »

wildmusings wrote: post #9
Gibbon1 wrote: post #8

Earlier quoted context omitted.

Problem is people buy guns when they aren't suicidal. Tip: If you own a gun and are feeling suicidal, give it to a trusted person for safekeeping.

It can't hurt to get rid of the gun if you're suicidal. But would it actually make a difference? Suicide rates across countries aren't related to gun availability.

I think false positives can hurt.

Re: Machine learning of neural representations of emotion identifies suicidal youth

#14

Post by lottin »

nonbel wrote: post #3

Will it be that 10% of people are suicidal and it always predicts non-suicidal? Will it be that accuracy actually means AUC? Will it be that they are reporting predictive skill on the training data?

Not only that, the researchers admit that 80% of suicidal people deny being suicidal. Then, how can they be sure than the ones in the control group are not suicidal?

Re: Machine learning of neural representations of emotion identifies suicidal youth

#15

Post by skj »

wildmusings wrote: post #9
Gibbon1 wrote: post #8

Earlier quoted context omitted.

Problem is people buy guns when they aren't suicidal. Tip: If you own a gun and are feeling suicidal, give it to a trusted person for safekeeping.

It can't hurt to get rid of the gun if you're suicidal. But would it actually make a difference? Suicide rates across countries aren't related to gun availability.

Got any citation for that? Sounds like the kind of thing someone would confidently assert on principle.

Re: Machine learning of neural representations of emotion identifies suicidal youth

#16

Post by bobstaples »

nieve wrote: post #4

"This study used machine-learning algorithms (Gaussian Naive Bayes) to identify such individuals (17 suicidal ideators versus 17 controls) with high (91%) accuracy, based on their altered functional magnetic resonance imaging neural signatures of death-related and life-related concepts." Anyone with a Nature subscription want to check whether they simply trained their discriminator and then used it on the same data s…

in the paper they state they performed " 34 “leave one participant out” cross-validation cycles (folds)", the dataset still seems to small to be able to draw any conclusion though.

Re: Machine learning of neural representations of emotion identifies suicidal youth

#17

Post by mintplant »

evolve2017 wrote: post #5

To the moderators, the title would be more accurate with 'fMRI' as opposed to 'MRI'. The latter is typically used to examine structural brain elements, whereas fMRI is thought to correlate with brain activity and, by extension, thought. Confusing the two would lead to the more unusual conclusion that suicidal ideation is associated with abnormal brain connectivity, while the authors are instead focusing on neuronal a…

Specifically fMRI measures blood flow across the brain (the BOLD response) which is correlated with neuron activity. It has good spatial resolution but poor temporal resolution [0], compared to EEG which gives you good temporal resolution but poor spatial resolution.

[0] i.e. you know with precision where in the brain activity occurred, but less precisely when it occurred in time

Re: Machine learning of neural representations of emotion identifies suicidal youth

#18

Post by nonbel »

nonbel wrote: post #3

Will it be that 10% of people are suicidal and it always predicts non-suicidal? Will it be that accuracy actually means AUC? Will it be that they are reporting predictive skill on the training data?

"Machine learning entails training a classifier on a subset of the data and testing the classifier on an independent subset. The crossvalidation procedure iterates through all possible partitionings (folds) of the data, always keeping the training and test sets separate from each other. The main machine learning here uses a GNB classifier (using pooled variance).

[...]

The features used by the classifier to characterize a participant consisted of a vector of activation levels for several (discriminating) concepts in a set of (discriminating) brain locations. To determine how many and which concepts were most discriminating between ideators and controls, a reiterative procedure analogous to stepwise regression was used, first finding the single most discriminating concept and then the second most discriminating concept, reiterating until the next step reduced the accuracy. A similar procedure was used to determine the most discriminating locations (clusters)." https://www.nature.com/articles/s41562-017-0234-y

The winner is #3: data leakage leading them to use predictive skill on the training data.

Re: Machine learning of neural representations of emotion identifies suicidal youth

#19

Post by aplummer »

wildmusings wrote: post #9
Gibbon1 wrote: post #8

Earlier quoted context omitted.

Problem is people buy guns when they aren't suicidal. Tip: If you own a gun and are feeling suicidal, give it to a trusted person for safekeeping.

It can't hurt to get rid of the gun if you're suicidal. But would it actually make a difference? Suicide rates across countries aren't related to gun availability.

Suicide is definitely linked to gun availability.

"A study by the Harvard School of Public Health of all 50 U.S. states reveals a powerful link between rates of firearm ownership and suicides. Based on a survey of American households conducted in 2002, HSPH Assistant Professor of Health Policy and Management Matthew Miller, Research Associate Deborah Azrael, and colleagues at the School’s Injury Control Research Center (ICRC), found that in states where guns were prevalent—as in Wyoming, where 63 percent of households reported owning guns—rates of suicide were higher. The inverse was also true: where gun ownership was less common, suicide rates were also lower."

https://www.hsph.harvard.edu/news/magazine/guns-and-suicide/

Re: Machine learning of neural representations of emotion identifies suicidal youth

#20

Post by SomeStupidPoint »

wildmusings wrote: post #9
Gibbon1 wrote: post #8

Earlier quoted context omitted.

Problem is people buy guns when they aren't suicidal. Tip: If you own a gun and are feeling suicidal, give it to a trusted person for safekeeping.

It can't hurt to get rid of the gun if you're suicidal. But would it actually make a difference? Suicide rates across countries aren't related to gun availability.

Intentionally denying 1 in 10 healthy adults their rights is illegal, no matter how much good you're doing by denying some smaller group their rights.

(It's also not clear that even if they have suicidal ideation that they're not entitled to gun rights, but I don't feel like having that debate today.)

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