How people use, and lose, preexisting biases to make decisions

From love and politics to health and finances, humans can sometimes make decisions that appear irrational, or dictated by an existing bias or belief. But a new study from Columbia University neuroscientists uncovers a surprisingly rational feature of the human brain: A previously held bias can be set aside so that the brain can apply logical, mathematical reasoning to the decision at hand. These findings highlight the importance that the brain places on the accumulation of evidence during decision-making, as well as how prior knowledge is assessed and updated as the brain incorporates new evidence over time.

This research was reported today in Neuron.

“As we interact with the world every day, our brains constantly form opinions and beliefs about our surroundings,” said Michael Shadlen, MD, PhD, the study’s senior author and a principal investigator at Columbia’s Mortimer B. Zuckerman Mind Brain Behavior Institute. “Sometimes knowledge is gained through education, or through feedback we receive. But in many cases we learn, not from a teacher, but from the accumulation of our own experiences. This study showed us how our brains help us to do that.”

As an example, consider an oncologist who must determine the best course of treatment for a patient diagnosed with cancer. Based on the doctor’s prior knowledge and her previous experiences with cancer patients, she may already have an opinion about what treatment combination (i.e. surgery, radiation and/or chemotherapy) to recommend — even before she examines this new patient’s complete medical history.

But each new patient brings new information, or evidence, that must be weighed against the doctor’s prior knowledge and experiences. The central question, the researchers of today’s study asked, was whether, or to what extent, that prior knowledge would be modified if someone is presented with new or conflicting evidence.

To find out, the team asked human participants to watch a group of dots as they moved across a computer screen, like grains of sand blowing in the wind. Over a series of trials, participants judged whether each new group of dots tended to move to the left or right — a tough decision as the movement patterns were not always immediately clear.

As new groups of dots were shown again and again across several trials, the participants were also given a second task: to judge whether the computer program generating the dots appeared to have an underlying bias.

Without telling the participants, the researchers had indeed programmed a bias into the computer; the movement of the dots was not evenly distributed between rightward and leftward motion, but instead was skewed toward one direction over another.

“The bias varied randomly from one short block of trials to the next,” said Ariel Zylberberg, PhD, a postdoctoral fellow in the Shadlen lab at Columbia’s Zuckerman Institute and the paper’s first author. “By altering the strength and direction of the bias across different blocks of trials, we could study how people gradually learned the direction of the bias and then incorporated that knowledge into the decision-making process.”

The study, which was co-led by Zuckerman Institute Principal Investigator Daniel Wolpert, PhD, took two approaches to evaluating the learning of the bias. First, implicitly, by monitoring the influence of bias in the participant’s decisions and their confidence in those decisions. Second, explicitly, by asking people to report the most likely direction of movement in the block of trials. Both approaches demonstrated that the participants used sensory evidence to update their beliefs about directional bias of the dots, and they did so without being told whether their decisions were correct.

“Originally, we thought that people were going to show a confirmation bias, and interpret ambiguous evidence as favoring their preexisting beliefs” said Dr. Zylberberg. “But instead we found the opposite: People were able to update their beliefs about the bias in a statistically optimal manner.”

The researchers argue that this occurred because the participants’ brains were considering two situations simultaneously: one in which the bias exists, and a second in which it does not.

“Even though their brains were gradually learning the existence of a legitimate bias, that bias would be set aside so as not to influence the person’s assessment of what was in front of their eyes when updating their belief about the bias,” said Dr. Wolpert, who is also professor of neuroscience at Columbia University Irving Medical Center (CUIMC). “In other words, the brain performed counterfactual reasoning by asking ‘What would my choice and confidence have been if there were no bias in the motion direction?’ Only after doing this did the brain update its estimate of the bias.

The researchers were amazed at the brain’s ability to interchange these multiple, realistic representations with an almost Bayesian-like, mathematical quality.

“When we look hard under the hood, so to speak, we see that our brains are built pretty rationally,” said Dr. Shadlen, who is also professor of neuroscience at CUIMC and an investigator at the Howard Hughes Medical Institute. “Even though that is at odds with all the ways that we know ourselves to be irrational.”

Although not addressed in this study, irrationality, Dr. Shadlen hypothesizes, may arise when the stories we tell ourselves influence the decision-making process.

“We tend to navigate through particularly complex scenarios by telling stories, and perhaps this storytelling — when layered on top of the brain’s underlying rationality — plays a role in some of our more irrational decisions; whether that be what to eat for dinner, where to invest (or not invest) your money or which candidate to choose.”

This research was supported by the Howard Hughes Medical Institute, the National Eye Institute (R01 EY11378), the Human Frontier Science Program, the Wellcome Trust and the Royal Society.

Source: Read Full Article

How the brain biases beliefs: Proposed neural circuit may underlie motivation to cling to desirable notions about the future

People’s motivation to cling to desirable notions about future outlooks results from interactions between prefrontal cortex regions, according to a human neuroimaging study published in JNeurosci.

Bojana Kuzmanovic and colleagues uncovered circuits in the brain that support belief updating by asking participants to estimate their own and a peer’s likelihood of experiencing an adverse life event, such as receiving a cancer diagnosis, and then presenting them with the actual federal statistics. Participants then reevaluated their personal risk in light of this new information.

The researchers found that the difference between the two estimates was greater when participants initially overestimated their risk of the adverse event, demonstrating the well-known optimism bias. An analysis of brain activity and the underlying circuitry revealed that this phenomenon depends on the influence of the brain’s valuation system on reasoning processes.

The proposed circuit involves the dorsolateral, ventromedial, and dorsomedial prefrontal cortex, which together bias integration of new information to support a preferred conclusion.

Source: Read Full Article

Discovery presents treatment hope for Alzheimer’s and other neurodegenerative diseases

There is new hope for the treatment of Alzheimer’s and other neurological diseases following a ground-breaking discovery made by an Australian-Chinese research collaboration.

Researchers from the University of South Australia and the Third Military Medical University in China have discovered a signal pathway within cells, and also invented a potential drug that could stop degeneration and actually improve learning and memory in affected patients.

UniSA’s Professor Xin-Fu Zhou and colleagues have been investigating tauopathies — which refers to a class of diseases caused by misfolding of the tau protein inside nerve cells that results in cell damage and eventually cell death.

These diseases include Alzheimer’s, Parkinson’s and Motor Neuron Disease, all of which presently have no cure.

Specifically, the team has looked into frontotemporal lobe degeneration (FTLD), a term representing a group of clinical syndromes related to cognitive impairment, behavioural abnormalities and speech disorders.

Professor Zhou says that previously it was unknown how the gene mutation was responsible for causing cell death or damage — referred to generally as neurodegeneration, and dementia in patients with FTLD and other motor neuron diseases. “Right now there is no treatment available at all,” Prof Zhou says. “We have been investigating how these tauopathies (diseases) have some common pathology, including a particular tau protein that plays a critical role in nerve cell function.”

Tau protein is a protein that stabilises microtubules and it is specifically abundant in neurons of the nervous system, but not in elsewhere.

“Our research found that in both the animal model and human brains, the signal of neurotrophins and receptors is abnormal in brains with FTLD,” Prof Zhou says.

“We discovered an increase in the neurotrophin signalling pathway that is related to life and death of nerve cells, known as proNGF/p75, and then found blocking its functions was shown to reduce cell damage.

“Thus, in this paper we not only discovered a signaling pathway but also invented a potential drug for treatment of such diseases.”

Given this strong evidence now available, the next stage is a clinical trial and South Australian biotech company Tiantai Medical Technology Pty Ltd has recently acquired a licence to further develop and commercialise this medical technology.

Professor Zhou says this industry involvement means there is an opportunity to translate the discovery into a treatment of Alzheimer’s disease and other tauopathies.

The paper published in Molecular Psychiatry is a collaborative work between two laboratories led by Professor Xin-Fu Zhou, University of South Australia and Professor Yanjiang Wang, the Third Military Medical University.

Source: Read Full Article

Who made the error? The brain distinguishes causes of errors to perform adaptation

Practice is necessary to improve motor skills. Even if one performs poorly at first, one’s athletic performance improves through repeated exercise due to the reduction of motor errors as the brain learns.

However, it’s important to remember that there are two types of errors: motor errors caused by poor motor control and target errors caused by unexpected target movements.

For example, if you swung a bat aiming at a ball coming straight to the middle of the strike zone and missed your swing 10 cm over the ball, the missed swing was caused by your motor error. So, the connection between your intention and your movement control needs to be adjusted downward.

On the other hand, if you missed the ball because it suddenly moved downwards 10 cm below the center of the strike zone after going through the center, the missed swing was caused by unexpected movement of the target. So, when it comes to these target errors, it would be better to learn using a system to predict the target’s move instead of changing the connection between intention and movement control.

Using the monkey parietal lobe, two researchers at Osaka University, Shigeru Kitazawa and Masato Inoue, examined (1) brain regions to detect motor and target errors, and (2) whether error signals from these regions were really used for learning. Their research results were published in Current Biology.

They found that the parietal lob of the cerebral cortex, the region in which signals of visual, acoustic, and somatic sensations are perceived, distinguished the causes of motor errors in arm reaching movements and provided signals to compensate for these errors. They also revealed that Brodmann area 5 detected self-generated motor errors and provided signals for adaptation and that Brodmann area 7 detected target errors caused by target movements and provided error signals for adaptation.

This study verified that the brain does not automatically detect the discrepancy between the hand and target positions, i.e., error, but the brain distinguishes motor error from target error and performs adaptation using the two distinctive systems.

This discovery will lead not only to the development of effective learning of sports, but also to the improvement of autonomous driving systems and the development of effective learning methods for robot control.

Source: Read Full Article

Brain iron levels may predict multiple sclerosis disabilities

A new, highly accurate MRI technique can monitor iron levels in the brains of multiple sclerosis (MS) patients and help identify those at a higher risk for developing physical disability, according to a study published in the journal Radiology.

MS is a disease that attacks three critical components of the central nervous system: the neurons (nerve fibers), myelin (the protective sheath around the neurons), and the cells that produce myelin. Common symptoms of MS include weakness, spasticity and pain. The disease can progress in many patients, leaving them severely disabled. Brain atrophy is the current gold standard for predicting cognitive and physical decline in MS, but it has limitations, said study lead author Robert Zivadinov, M.D., Ph.D., professor of neurology at the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo (UB) in Buffalo, N.Y. He is director of the Buffalo Neuroimaging Analysis Center in the Jacobs School and the Center for Biomedical Imaging at UB’s Clinical and Translational Science Institute.

“Brain atrophy takes a long time to see,” he said. “We need an earlier measure of who will develop MS-related disability.”

MRI studies of iron concentration have emerged recently as a promising measure of changes in the brain associated with MS progression. Iron is vital for various cellular functions in the brain, including myelination of neurons, and both iron overload and iron deficiencies can be harmful.

“It is known that there is more iron in the deep gray matter structures in MS patients, but also we’ve seen in recent literature that there are regions where we find less iron in the brains of these patients,” Dr. Zivadinov said.

Dr. Zivadinov and colleagues recently compared brain iron levels in people with MS to those of a healthy control group using an advanced MRI technique called quantitative susceptibility mapping. A brain region with more iron would have higher magnetic susceptibility, and one with less iron would have lower susceptibility.

The researchers performed the mapping technique on 600 MS patients, including 452 with early-stage disease and 148 whose disease had progressed.

Compared to 250 healthy control participants, MS patients had higher levels of iron in the basal ganglia, a group of structures deep in the brain that are central to movement. However, the MS patients had lower levels of iron in their thalamus, an important brain region that helps process sensory input by acting as a relay between certain brain structures and the spinal cord. The lower iron content in the thalamus and higher iron content in other deep gray matter structures of people with MS were associated with longer disease duration, higher disability degree and disease progression.

This association with clinical disability persisted even after adjusting for changes in the brain volumes of each individual structure.

“In this large cohort of MS patients and healthy controls, we have reported, for the first time, iron increasing in the basal ganglia but decreasing in thalamic structures,” Dr. Zivadinov said. “Iron depletion or increase in several structures of the brain is an independent predictor of disability related to MS.”

The results point to a potential role for quantitative susceptibility mapping in clinical trials of promising new drugs, Dr. Zivadinov said. Current treatments involving anti-inflammatory drugs do not prevent MS patients from developing disability.

“Susceptibility is an interesting imaging marker of disease severity that can predict which patients are at severe risk of progressing,” Dr. Zivadinov said. “To be able to act against changes in susceptibility would be extremely beneficial.”

Source: Read Full Article