The trouble with brain scans + Attention & memory share same neural mechanisms

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Study shows that attention and working memory share the same neural mechanisms

INTRO: In 1890, psychologist William James described attention as the spotlight we shine not only on the world around us, but also on the contents of our minds.

Most cognitive scientists since then have drawn a sharp distinction between what James termed "sensorial attention" and "intellectual attention," now usually called "attention" and "working memory," but James saw them as two varieties of the same mental process.

New research by Princeton neuroscientists suggests that James was on to something, finding that attention to the outside world and attention to our own thoughts are actually two sides of the same neural coin. What's more, they have observed the coin as it flips inside the brain.

A paper published in Nature on March 31 by Matthew Panichello, a postdoctoral research associate at the Princeton Neuroscience Institute, and Timothy Buschman, an assistant professor of psychology and neuroscience at Princeton, found that attention and working memory share the same neural mechanisms. Importantly, their work also reveals how neural representations of memories are transformed as they direct behavior.

"When we act on sensory inputs we call it 'attention,'" said Buschman. "But there's a similar mechanism that can act on the thoughts we hold in mind." (MORE - details)

The trouble with brain scans

EXCERPTS: . . . The following year I joined a lab at Harvard, where I started working on an experiment that used functional MRI, or fMRI, to study the brain regions involved in social decision-making. fMRI allows us to record what the brain is up to while people perform mental tasks. I committed to a senior thesis and set my future sights on a Ph.D. in cognitive science.

[...] the “I” of fMRI stands for “imaging” because the output of this process is essentially a 3-D video of the brain in action. The scanning process divides the brain into small cubes called voxels, the three-dimensional equivalent of pixels. The data collected from a person’s scanning session consists of quantitative measures of the BOLD signal at every voxel. Voxels typically range in size from 1 cubic millimeter to 27 cubic millimeters—small to us, but colossal on the scale of neurons. For a sense of scale, the brain contains an estimated 100 billion neurons, and a single voxel in the human cortex can cover over 500,000 neurons. Those neurons may be doing any number of things—exciting each other, inhibiting each other, or firing in different patterns within sub-populations—but all that fMRI can detect is the net change in oxygenated blood over that whole voxel space every 2 seconds. This is like trying to determine the average opinion on foreign policy from 500,000 different people arguing, agreeing, and debating simultaneously.

[...] The most common analysis procedure in fMRI experiments, null hypothesis tests, require that the researcher designate a statistical threshold. Picking statistical thresholds determines what counts as a significant voxel—which voxels end up colored cherry red or lemon yellow. Statistical thresholds make the difference between a meaningful result published in prestigious journals like Nature or Science, and a null result shoved into the proverbial file drawer.

Scientists are under tremendous pressure to publish positive results, especially given the hypercompetitive academic job market that fixates on publication record as a measure of scientific achievement (though the reproducibility crisis has brought attention to the detriments of this incentive structure). If an fMRI study ends up with a null or lackluster result, you can’t always go back and run another version of the study. MRI experiments are very expensive and time-intensive—my own required upward of $25,000 and took over a year to finish. You can see how a researcher might be tempted, even subconsciously, to play around with the analysis parameters just one more time to see if they can find a significant effect in the data it cost so much to obtain.

“fMRI is clearly not pure noise, it’s a real signal, but it’s subject to many degrees of freedom, fiddling around with the data, filtering it in different ways until you can see whatever you want to see,” Born said.

The problem of statistical excess, called multiple comparisons, looms large over this part of the analysis. “That’s probably the single biggest issue in brain imaging,” Fischl told me. Multiple comparisons means too many statistical tests. The problem of multiple comparisons is like surveying 100,000 strangers about whether they know Beyoncé personally. None of those 100,000 people are actually acquainted with her, but for each person you ask, there is a 5 percent chance they will lie and say they are, just for kicks. In the end, you tally 5,000 friends of Beyoncé, even though the ground truth is that zero of those people are friends with her. If you had asked 100 strangers, you would only end up with five incorrect measurements, but because of sheer numbers and the probability of random deception, surveying 100,000 strangers results in 5,000 incorrect measurements.

So, too, with fMRI data: One person’s brain data has hundreds of thousands of voxels. By the sheer number of voxels and random noise, a researcher who performs a statistical test at every voxel will almost certainly find significant effects where there isn’t really one.

[...] It is precisely this power of brain images’ projected scientific authority that led anthropologist of science Joseph Dumit to comment on the “undue risk in courtrooms that brain images will not be seen as prejudiced, stylized representations of correlation, but rather as straightforward, objective photographs.”

In attempts to mitigate sentences, lawyers have adduced brain images as evidence of pathologies in criminal defendants. Arguments often take the following form: The defendant has a neurological or psychiatric disorder that impairs cognitive and moral reasoning. This image reveals the brain abnormalities associated with the psychopathology.

In court cases involving capital punishment, neuroimaging evidence can literally become a matter of life and death. At the same time, this kind of evidence validates conceptions of distinct human kinds: the mad and the sane, the pathological and the healthy, with these categories borne out in shining pictures of brain activity. In doing so, it privileges biological conceptions of personhood over other more holistic notions of a human life.

One concerning upshot of this is the medicalization of deviance, which can ultimately motivate biological intervention to eliminate behaviors considered non-normative or wrong...

[...] The problem lies in what we ask and expect of these scientific results, and the authority we give them. After all, the phrase “the brain lights up” is an artifact of the images that we craft. The eye-catching blobs and connectivity maps exist because of the particular way in which neuroscientists, magnetic resonance physicists, and data scientists decided to visualize and represent data from the brain.

Now I’m questioning whether I want to continue in this fraught field. Since graduating, I’ve turned toward my other passion, political advocacy and education in the Asian-American community [...] Still, I keep my Google bookmark folder for cognitive science Ph.D. programs. I attend neuroscience lectures when I can. Maybe I’ll return, either as a scientist or sociologist of neuroimaging techniques. In opening the black box of the MRI machine, I may have fallen out of love with neuroimages, but at least now I see them for what they are... (MORE - details)
Syne Offline
Why would anyone think external and internal attention are any different, except in what they perceive? Working memory is just an "automated" bit of attention, much like what we do when we drive a car, not having to think about every coordinated action required. This bit of attention is basically what retrieves memories, and it's what brings up the name of that song you were trying to remember an hour ago, and other delayed memory retrieval as well.

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