How female fruit flies know when to say ‘yes’

A fundamental question in neurobiology is how animals, including humans, make decisions. A new study publishing in the open access journal PLOS Biology on October 7 reveals how fruit fly females make a very important decision: to either accept or reject male courtship. This decision appears to be generated by a very small number of excitatory neurons that use acetylcholine as their neurotransmitter located in three brain regions. This study provides the framework to understand how decisions are generated and suggests that a decision is reached because that option is literally the most exciting.

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Judgment and decision-making: brain activity indicates there is more than meets the eye

Published today in PLOS ONE, the study is the first in the world to show that it is possible to predict abstract judgments from brain waves, even though people were not conscious of making such judgments. The study also increases our understanding of impulsive behaviours and how to regulate it. 



It found that researchers could predict from participants’ brain activity how exciting they found a particular image to be, and whether a particular image made them think more about the future or the present. This is true even though the brain activity was recorded before participants knew they were going to be asked to make these judgments.


Lead authors Dr Stefan Bode from the Melbourne School of Psychological Sciences and Dr Carsten Murawski from the University of Melbourne Department of Finance said these findings illustrated there was more information encoded in brain activity than previously assumed.


“We have found that brain activity when looking at images can encode judgments such as time reference, even when the viewer is not aware of making such judgments. Moreover, our results suggest that certain images can prompt a person to think about the present or the future,” they said.


The authors said the results contributed to our understanding of impulsive behaviours, especially where those behaviours were caused by ‘prompts’ in the world around us. 



“For instance, consider someone trying to quit gambling who sees a gambling advertisement on TV. Our results suggest that even if this person is trying to ignore the ad, their brain may be unconsciously processing it and making it more likely that they will relapse,” he said. 


The researchers used electroencephalography technology (EEG) to measure the electrical activity of people’s brains while they looked at different pictures. The pictures displayed images of food, social scenes or status symbols like cars and money. 



After the EEG, researchers showed participants the same pictures again and asked questions about each image, such as how exciting they thought the image was or how strongly the image made them think of either the present or the future.

A statistical ‘decoding’ technique was then used to predict the judgments participants made about each of the pictures from the EEG brain activity that was recorded.

Co-author Daniel Bennett said just as certain prompts might cause impulsive behaviour, images could be used to prompt people to be more patient by regulating impulse control.


“Our results suggest that prompting people with images related to the future might cause processing outside awareness that could make it easier to think about the future. In theory, this could make people less impulsive and more likely to make healthy long-term decisions. These are hypotheses we will try to test in the future,” he said. 

The research was done in collaboration with the University of Cologne, Germany.

Using the brain to forecast decisions

You’re waiting at a bus stop, expecting the bus to arrive any time. You watch the road. Nothing yet. A little later you start to pace. More time passes. “Maybe there is some problem”, you think. Finally, you give up and raise your arm and hail a taxi. Just as you pull away, you glimpse the bus gliding up. Did you have a choice to wait a bit longer? Or was giving up too soon the inevitable and predictable result of a chain of neural events?

In research published on 09/28/2014 in the journal Nature Neuroscience, scientists show that neural recordings can be used to forecast when spontaneous decisions will take place. “Experiments like this have been used to argue that free will is an illusion,” says Zachary Mainen, a neuroscientist at the Champalimaud Centre for the Unknown, in Lisbon, Portugal, who led the study, “but we think that interpretation is mistaken.”

The scientists used recordings of neurons in an area of the brain involved in planning movements to try to predict when a rat would give up waiting for a delayed tone. “We know they were not just responding to a stimulus, but spontaneously deciding when to give up, because the timing of their choice varied unpredictably from trial to trial” said Mainen. The researchers discovered that neurons in the premotor cortex could predict the animals’ actions more than one second in advance. According to Mainen, “This is remarkable because in similar experiments, humans report deciding when to move only around two tenths of a second before the movement.”

However, the scientists claim that this kind of predictive activity does not mean that the brain has decided. “Our data can be explained very well by a theory of decision-making known as an ‘integration-to-bound’ model” says Mainen. According to this theory, individual brain cells cast votes for or against a particular action, such as raising an arm. Circuits within the brain keep a tally of the votes in favor of each action and when a threshold is reached it is triggered. Critically, like individual voters in an election, individual neurons influence a decision but do not determine the outcome. Mainen explained: “Elections can be forecast by polling, and the more data available, the better the prediction, but these forecasts are never 100% accurate and being able to partly predict an election does not mean that its results are predetermined. In the same way, being able to use neural activity to predict a decision does not mean that a decision has already taken place.”

The scientists also described a second population of neurons whose activity is theorized to reflect the running tally of votes for a particular action. This activity, described as “ramping”, had previously been reported only in humans and other primates. According to Masayoshi Murakami, co-author of the paper, “we believe these data provide strong evidence that the brain is performing integration to a threshold, but there are still many unknowns.” Said Mainen, “what is the origin of the variability is a huge question. Until we understand that, we cannot say we understand how a decision works”.

Neurons See What We Tell Them to See

Neurons programmed to fire at specific faces—such as the famously reported “Jennifer Aniston neuron”—may be more in line with the conscious recognition of faces than the actual images seen. Subjects presented with a blended face, such as an amalgamation of Bill Clinton and George W. Bush, had significantly more firing of such face-specific neurons when they recognized the blended or morphed face as one person or the other. Results of the study led by Christof Koch at the Allen Institute for Brain Science, and carried out by neuroscientists Rodrigo Quian Quiroga at the University of Leicester, Alexander Kraskov at University College London and Florian Mormann at the University of Bonn, under the clinical supervision of the neurosurgeon Itzhak Fried at the University of California at Los Angeles Medical School, are published online today in the journal Neuron.

Some neurons in the region of the brain known as the medial temporal lobe are observed to be extremely selective in the stimuli to which they respond. A cell may only fire in response to different pictures of a particular person who is very familiar to the subject (such as loved one or a celebrity), the person’s written or spoken name, or simply recalling the person from memory.

“These highly specific cells are an entry point to investigate how the brain makes meaning out of visual information,” explains Christof Koch, Chief Scientific Officer at the Allen Institute for Brain Science and senior author on the paper. “We wanted to know how these cells responded not just to a simple image of a person’s face, but to a more ambiguous image of that face averaged or morphed with another person’s face.”

For the trials, subjects were shown either the face of individuals such as Bill Clinton or George W. Bush (the “adaptor” image), and then an ambiguous face which was a blend of both faces. Primed with the Clinton image, subjects tended to recognize Bush’s face in the blended image, while subjects who saw Bush’s face first recognized the blended face as Clinton. That is, even though the blended images were identical, subjects tended to consciously perceive the identity of face to which they were not adapted.

Researchers wanted to know whether these selective neurons responded to the actual image on the screen, or whether they responded more to the perception that the image caused in the brain of the subject. When subjects recognized the ambiguous face as belonging to Clinton, their Clinton-specific neurons fired. However, when subjects recognized that same face as Bush, the neurons fired significantly less. These results indicated that conscious recognition of the face played a crucial role in whether the neurons fired, rather than the raw visual stimulus.

“This study provides further evidence that stimulus-specific neurons in the medial temporal lobe follow the subjective perception of the person, as opposed to faithfully reporting the visual stimulus the person sees,” explains Koch. “This distinction may help us glean insight into how the brain takes raw visual information and transforms it into something meaningful, which can be further modulated by other aspects of experience in the brain.”

Strategic or Random? How the Brain Chooses

Many of the choices we make are informed by experiences we’ve had in the past. But occasionally we’re better off abandoning those lessons and exploring a new situation unfettered by past experiences. Scientists at the Howard Hughes Medical Institute’s Janelia Research Campus have shown that the brain can temporarily disconnect information about past experience from decision-making circuits, thereby triggering random behavior.

In the study, rats playing a game for a food reward usually acted strategically, but switched to random behavior when they confronted a particularly unpredictable and hard-to-beat competitor. The animals sometimes got stuck in a random-behavior mode, but the researchers, led by Janelia lab head Alla Karpova and postdoctoral fellow Gowan Tervo, found that they could restore normal behavior by manipulating activity in a specific region of the brain. Because the behavior of animals stuck in this random mode bears some resemblance to that of patients affected by a psychological condition called learned helplessness, the findings may help explain that condition and suggest strategies for treating it. Karpova, Tervo and their colleagues published their findings in the September 25, 2012, issue of the journal Cell.

The brain excels at integrating information from past experiences to guide decision-making in new situations. But in certain circumstances, random behavior may be preferable. An animal might have the best chance of avoiding a predator if it moves unpredictably, for example. And in a new environment, unrestricted exploration might make more sense than relying on an internal model developed elsewhere. So scientists have long speculated that the brain may have a way to switch off the influence of past experiences so that behavior can proceed randomly, Karpova says. But others disagreed. “They argue that it’s inefficient, and that it would be at odds with what some people call one of the most central operating principles of the brain – to use our past experience and knowledge to optimize behavioral choices,” she notes.

Karpova and her colleagues wanted to see if they could create a situation that would force animals to switch into this random mode of behavior. “We tried to create a setting that would push the need to create behavioral variability and unpredictability to its extreme,” she says. They did this by placing rats in a competitive setting in which a computer-simulated competitor determined which of two holes in a wall would provide a sugary reward. The virtual competitor, whose sophistication was varied by the experimenters, analyzed the rats’ behavior to predict their future choices.

“We thought if we came up with very sophisticated competitors, then the animals would eventually be unable to figure out how to outcompete them, and be forced to either give up or switch into this [random] mode, if such a mode exists,” Karpova says. And that’s exactly what happened: When faced with a weak competitor, the animals made strategic choices based on the outcomes of previous trials. But when a sophisticated competitor made strong predictions, the rats ignored past experience and made random selections in search of a reward.

Now that they had evidence that the brain could generate both strategic and random behavior, Karpova and her colleagues wanted to know how it switched between modes. Since that switch determines whether or not an animal’s internal model of the world influences its behavior, the scientists suspected it might involve a brain region called the anterior cingulate cortex, where that internal model is likely encoded.

They found that they could cause animals to switch between random and strategic behavior by manipulating the level of a stress hormone called norepinephrine in the anterior cingulate cortex. Increasing norepinephrine in the region activated random behavior and suppressed the strategic mode.  Inhibiting release of the hormone had the opposite effect.

Karpova’s team observed that animals in their experiments sometimes continued to behave randomly, even when such behavior was no longer advantageous. “If all they’ve experienced is this really sophisticated competitor for several sessions that thwarts their attempts at strategic, model-based counter-prediction, they go into this [random mode], and they can get stuck in it for quite some time after that competitor is gone,” she says. This, she says, resembles the condition of learned helplessness, in which strategic decision-making is impaired following an experience in which a person finds they are unable to control their environment.

The scientists could release the animals from this “stuck” state by suppressing the release of norepinephrine in the anterior cingulate cortex. “Just by manipulating a single neuromodulatory input into one brain area, you can dramatically enhance the strategic mode. The effect is strong enough to rescue animals out of the random mode and successfully transform them into strategic decision makers,” Karpova says. “We think this might shed light on what has gone wrong in conditions such as learned helplessness, and possibly how we can help alleviate them.” 

Karpova says that now that her team has uncovered a mechanism that switches the brain between random and strategic behavior, she would like to understand how those behaviors are controlled in more natural settings. “We normally try to use all of our knowledge to think strategically, but sometimes we still need to explore,” she says. In most cases, that probably means brief bouts of random behavior during times when we are uncertain that past experience is relevant, followed by a return to more strategic behavior – a more subtle balance that Karpova intends to investigate at the level of changes in activity in individual neural circuits.

Gambling with confidence: Are you sure about that?

Life is a series of decisions, ranging from the mundane to the monumental. And each decision is a gamble, carrying with it the chance to second-guess. Did I make the right turn at that light? Did I choose the right college? Was this the right job for me?

Our desire to persist along a chosen path is almost entirely determined by our confidence in the decision: when you are confident that your choice is correct, you are willing to stick it out for a lot longer.

Confidence determines much of our path through life, but what is it? Most people would describe it as an emotion or a feeling. In contrast, scientists at Cold Spring Harbor Laboratory (CSHL) have found that confidence is actually a measureable quantity, and not reserved just for humans. The team, led by CSHL Associate Professor Adam Kepecs, has identified a brain region in rats whose function is required for the animals to express confidence in their decisions.

How do we know when a rat is exhibiting confidence? The researchers devised a method to study decision making in these animals. The rats were offered an odor that they were trained to associate with one of two doors. When they chose the correct door, they were rewarded. This part was easy for the animals: their selections were almost always correct.­­ Things got trickier when Kepecs and his team offered a mixture of the two scents, with one dominating over the other by only a very small percentage. The rats now needed to choose the door representing the dominant odor in order to get their reward – a choice that reflects their best guess.

In work published today in Neuron, the team describes how confidence can be measured simply by challenging a rat to wait for the reward to be revealed behind the door. The time they are willing wait serves as a measure of the confidence in their original decision. “We found that the rats are willing to ‘gamble’ with their time,” Kepecs explains, sometimes waiting as much as 15 seconds, which is an eternity for these animals. “This is something that we can measure and create mathematical models to explain,” says Kepecs. “The time rats are willing to wait predicts the likelihood of correct decisions and provides an objective measure to track the feeling of confidence.”

The researchers hypothesized that a distinct region of the brain might control confidence. Previous work has suggested that the orbitofrontal cortex (OFC), a part of the brain involved in making predictions, might have a role in decision confidence. Kepecs and his team specifically shut off neurons in the OFC, inactivating it, and found that rats no longer exhibited appropriate levels of confidence in their decisions.

“With an inactive OFC, the rats retained the ability to make decisions – their accuracy did not change,” says Kepecs. “And they spent the same amount of time waiting for a reward on average. The only difference is that animals’ willingness to wait for a reward was no longer guided by confidence. They would often wait a long time even when they were wrong.”

The discovery offers a rare glimpse into the neuronal basis of a higher-level cognitive process, and is likely to have implications in human decision-making as well. As Kepecs describes, “we now know that the OFC is critical for making on-the-fly predictions in rats. The human OFC is just a more sophisticated version of the rodent counterpart.” The team is expanding their research to explore how the elusive feelings of confidence are based on objective predictions that influence human decisions as well.

Don’t Underestimate Your Mind’s Eye

Take a look around, and what do you see? Much more than you think you do, thanks to your finely tuned mind’s eye, which processes images without your even knowing.

A University of Arizona study has found that objects in our visual field of which we are not consciously aware still may influence our decisions. The findings refute traditional ideas about visual perception and cognition, and they could shed light on why we sometimes make decisions — stepping into a street, choosing not to merge into a traffic lane — without really knowing why.

Laura Cacciamani, who recently earned her doctorate in psychology with a minor in neuroscience, has found supporting evidence. Cacciamani’s is the lead author on a co-authored study, published online in the journal Attention, Perception and Psychophysics, shows that the brain’s subconscious processing has an impact on behavior and decision-making.

This seems to make evolutionary sense, Cacciamani said. Early humans would have required keen awareness of their surroundings on a subliminal level in order to survive.

"Your brain is always monitoring for meaning in the world, to be aware of your general surroundings and potential predators," Cacciamani said. "You can be focused on a task, but your brain is assessing the meaning of everything around you – even objects that you’re not consciously perceiving."

The study builds on the findings of earlier research by Jay Sanguinetti, who also was a doctoral candidate in the UA Department of Psychology. Both studies go against conventional wisdom among vision scientists.

"According to the traditional view, the brain accesses the meaning – or the memory – of an object after you perceive it," Cacciamani said. "Against this view, we have now shown that the meaning of an object can be accessed before conscious perception.

"We’re showing that there’s more interplay between memory and perception than previously has been assumed," she said.

Cacciamani asked participants in her study to classify nouns that appeared on a computer screen as naming a natural object or artificial object by pressing one of two buttons labeled “natural” or “artificial.” For example, the word “leaf” indicates an object found in nature, while “anchor” indicates a man-made or artificial object.

But before each word appeared on the screen, the computer flashed a black silhouette that – unknown to participants – had portions of natural or artificial objects suggested along the white outside regions (called the “ground” regions) of the image. Participants were not told to look for anything in the silhouettes, and they were flashed so quickly – 50 milliseconds – that it would have been difficult to notice the objects in the ground regions even if someone knew what to look for. Participants never were aware that the silhouette’s grounds suggested recognizable objects.

Cacciamani measured how well study participants performed at categorizing the words as natural or artificial by recording speed and accuracy.

"We found that participants performed better on the natural/artificial word task when that word followed a silhouette whose ground contained an object of the same rather than a different category," Cacciamani said.

This indicates that the brain accessed the meaning of the objects in the silhouette’s grounds even though study participants didn’t know the objects were there, she said.

"Every day our visual systems are bombarded with more information than we can consciously be aware of," Cacciamani said. "We’re showing that your brain might still be accessing information without your conscious awareness, and that could influence your behavior."

Influenced by Self-Interest, Humans Less Concerned About Inequity To Others

Strongly influenced by their self-interest, humans do not protest being overcompensated, even when there are no consequences, researchers in Georgia State University’s Brains and Behavior Program have found.

This could imply that humans are less concerned than previously believed about the inequity of others, researchers said. Their findings are published in the journal Brain Connectivity. These findings suggest humans’ sense of unfairness is affected by their self-interest, indicating the interest humans show in others’ outcomes is a recently evolved propensity.

It has long been known that humans show sensitivity when they are at a disadvantage by refusing or protesting outcomes more often when they are offered less money than a social partner. But the research team of physics graduate students Bidhan Lamichhane and Bhim Adhikari and Brains and Behavior faculty Dr. Sarah Brosnan, associate professor of psychology, and Dr. Mukesh Dhamala, associate professor of physics and astronomy, reports that, contrary to expectations, humans do not show any sensitivity when they are overcompensated. They conclude that humans are more interested in their own outcomes than those of others.

“A true sense of fairness means that I get upset if I get paid more than you because I don’t think that’s fair,” Brosnan said. “We thought that people would protest quite a bit in the fixed decision game because it’s a cost-free way to say, ‘This isn’t fair.’ But that’s not what we saw at all. People protested higher offers at roughly the same rate that they refused offers where they got more, indicating that this lack of refusal in advantaged situations may not be because of the cost of refusing. It may just be because people don’t care as much as we thought they did if they’re getting more than someone else.”

The researchers also used functional magnetic resonance imaging (fMRI) to study the underlying brain mechanisms from 18 participants, who played three two-person economic exchange games that involved inequity in their favor and not in their favor. Overcompensated offers triggered a different brain circuit than undercompensated offers and indicate that people may be responding to overcompensation as if it were a reward. This could explain the lack of refusals in this unfair situation, researchers said.

Each game involved three offers for how $100 would be split: fair (amount between $40 to $60), unfair-low (disadvantageous to the subject, amount between $0 to $20) and unfair-overcompensated (advantageous to the subject, amount between $80 to $100). Participants played 30 rounds of each game and earned about two percent of the total amount from the games.

In the first two games, the subject received an offer for how much money they would receive and were then asked whether they wanted to reject or accept it. In the Ultimatum Game, if the responder rejected the offer, neither player received any money, leading to a fair outcome. In the Impunity Game, if the subject rejected the offer, only he or she lost the payoff, meaning the outcome was even more unfair than the offer. The subject got nothing, but the partner still got their proposed amount. In the Fixed Decision Game, the subject could choose to protest or not protest the offers, but this didn’t change the outcome for either player. This allowed subjects to protest offers without an associated cost.

The blood-oxygen level dependent signals of the brain were recorded by an MRI scanner as participants played the games. The results of brain response provided new insights into the functional role of the dorsolateral prefrontal cortex and related networks of brain regions for advantageous inequity and protest.

A network of brain regions consisting of the left caudate, right cingulate and right thalamus had a higher level of activity for overcompensated offers than for fair offers. For protest, a different network, consisting of the right dorsolateral prefrontal cortex, left ventrolateral prefrontal cortex and left substantia nigra, came into play. The researchers also mapped out how the brain activity flow occurred within these networks during decision-making.