Tears Are a Turn-Off

English

(l-r) Yaara Yeshurun, Prof. Noam Sobel, Dr. Sagit Shushan, Liron Rozenkrantz, Idan Frumin and Shani Gelstein. The smell of tears

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
When we cry – a universal human behavior – we clearly send all sorts of emotional signals. Now, Institute scientists have shown that some of those emotional signals are chemically encoded in the tears themselves: In research that recently appeared in Science, they demonstrated that merely sniffing a woman’s tears – even when the crying woman is nowhere in the vicinity – reduces sexual arousal in men.

Humans, like most animals, expel various compounds in body fluids that give off subtle messages to other members of the species. A number of studies in recent years, for instance, have found that substances in human sweat can carry a surprising range of emotional and other signals to those who smell them.
 
 

But tears are odorless. In fact, in a first experiment led by Shani Gelstein, Yaara Yeshurun and their colleagues in the lab of Prof. Noam Sobel in the Weizmann Institute’s Neurobiology Department, the researchers tested whether men could discriminate the smell of saline from that of tears collected from female volunteers watching sad movies in a secluded room. The men could not.

 

 
Tears a turn-off
 
In a second experiment, male volunteers sniffed either tears or a control saline solution, and had these applied under their nostrils on a pad while they made various judgments regarding images of women’s faces on a computer screen. The next day, the test was repeated – the men who were previously exposed to tears got saline and vice versa. The tests were double-blinded, meaning neither the men nor the researchers performing the trials knew what was on the pads. The researchers found that sniffing tears did not influence how the men rated the sadness or empathy expressed in the women’s faces. To their surprise, however, it did have a negative effect on the sex appeal attributed to those faces.

To further explore the finding, male volunteers watched emotional movies after sniffing tears or saline. Throughout the movies, participants were asked to provide self-ratings of mood while they were being monitored for such physiological measures of arousal as skin temperature, heart rate, etc. Self-ratings showed that the subjects’ emotional responses to sad movies were no more negative when exposed to women’s tears; the men “smelling” tears showed no additional empathy. But they did rate their sexual arousal a bit lower. The physiological measurements, however, told a clearer story. These revealed a pronounced tear-induced drop in physiological measures of arousal, including a significant dip in testosterone – a hormone related to sexual arousal.

Finally, Sobel and his team repeated the previous experiment within an fMRI machine that allowed them to measure brain activity. The scans revealed a significant reduction in activity levels in the brain areas associated with sexual arousal after the subjects had sniffed tears.

Sobel: “This study raises many interesting questions. What is the chemical involved? Do different kinds of emotional situations send different tear-encoded signals? Are women’s tears different from, say, men’s tears? Children’s tears? This study reinforces the idea that human chemical signals – even ones we’re not explicitly conscious of – affect the behavior of others.”
 
Human emotional crying was especially puzzling to Charles Darwin, who identified functional antecedents to most emotional displays – for example, the tightening of the mouth in disgust, which he thought originated as a response to tasting spoiled food. But the original purpose of emotional tears eluded him. The current study has offered an answer to this riddle: Tears may serve as a chemosignal. Sobel points out that some rodent tears are known to contain such chemical signals. “The uniquely human behavior of emotional tearing may not be so uniquely human after all,” he says.

The work was authored by Shani Gelstein, Yaara Yeshurun, Liron Rozenkrantz, Sagit Shushan, Idan Frumin, Yehudah Roth and Noam Sobel, and was conducted in collaboration with the Edith Wolfson Medical Center, Holon.

Prof. Noam Sobel's research is supported by the James S. McDonnell Foundation 21st Century Science Scholar in Understanding Human Cognition Program; the Minerva Foundation; the European Research Council; and Regina Wachter, NY.
 

 

 

 

 
(l-r) Yaara Yeshurun, Prof. Noam Sobel, Dr. Sagit Shushan, Liron Rozenkrantz, Idan Frumin and Shani Gelstein. The smell of tears
Life Sciences
English
  • Noam Sobel
  • Sensory nerves›Sensory signal
  • Smell

New Insight into "Aha!" Memories

English
 
When we suddenly get the answer to a riddle or understand the solution to a problem, we can practically feel the light bulb click on in our head. But what happens after the “Aha!” moment? Why do the things we learn through sudden insight tend to stick in our memory?

“Much of memory research involves repetitive, rote learning,” says Kelly Ludmer, a research student in the group of Prof. Yadin Dudai of the Institute’s Neurobiology Department, “but in fact, we regularly absorb large blocks of information in the blink of an eye and remember things quite well from single events. Insight is an example of a one-time event that is often well-preserved in memory.”

To investigate how lessons we gain from insight get embedded in our long-term memory, Ludmer, Dudai and Prof. Nava Rubin of New York University designed a test with “camouflage images” – photographs that had been systematically degraded until they resembled inkblots. When volunteers first viewed the images, they were hard pressed to identify them. But after the camouflage was switched with the original, undoctored picture for a second, the subjects experienced an ‘Aha!’ moment – the image now popped out clearly even in the degraded image. Their perceptions, says Ludmer, underwent a sudden change – just as a flash of insight instantly shifts our world view. To tax their memory of the insightful moment, participants were asked to repeat the exercise with dozens of different images and, in a later repeat session, they were given only the camouflaged images (together with some they hadn’t seen before) to identify.

 

Aha! Mouse over "camouflage" image for undoctored picture
 

The team found that some of the memories disappeared over time, but the ones that made it past a week were likely to remain. All in all, about half of all the learned “insights” seemed to be consolidated in the subjects’ memories.

To reveal what occurs in the brain at the moment of insight, the initial viewing session was conducted in a functional MRI (fMRI) scanner. When the scientists looked at the fMRI results, they were surprised to find that among the areas that lit up in the scans – those known to be involved in object recognition, for instance – was the amygdala. The amygdala is more famously known as the seat of emotion in the brain. Though it has recently been found to play a role in the consolidation of certain memories, studies have implied that it does so by attaching special weight to emotion-laden events. But the images used in the experiment – hot-air balloons, dogs, people looking through binoculars, etc. – were hardly the sort to elicit an emotional response. Yet, not only was the amygdala lighting up in the fMRI, the team found that its activity was actually predictive of the subject’s ability to identify the degraded image long after that moment of induced insight in which it was first recognized.


“Our results demonstrate, for the first time, that the amygdala is important for creating long-term memories – not only when the information learned is explicitly emotional, but also when there is a sudden reorganization of information in our brain, for example, involving a sudden shift in perception,” says Ludmer. “It might somehow evaluate the event, ‘deciding’ whether it is significant and therefore worthy of preservation.”

 

 

Prof. Yadin Dudai’s research is supported by the Nella and Leon Benoziyo Center for Neurological Diseases; the Abe and Kathryn Selsky Memorial Research Project; Miel de Botton Aynsley, UK; Dr. Henry Kaminer, New York, NY; Marla L. Schaefer, New York, NY; and Lisa Mierins Smith, Canada. Prof. Dudai is the incumbent of the Sara and Michael Sela Professorial Chair of Neurobiology.

 

Aha! Mouse over "camouflage" image for undoctored picture
Life Sciences
English
  • Long term memory
  • Memory
  • Neurobiology
  • Yadin Dudai
  • fMRI

Getting a Grasp on Memory

English
 
Long-term memory is a slippery thing. Just how slippery it can be was demonstrated a few years ago by Weizmann Institute scientists, who erased entire memories in rats just by blocking a certain protein in the brain. In other words, memory – even the part we imagine to contain neatly packed files – is in reality a dynamic piece of equipment that must be actively maintained to work. Now, in research published in Science, these scientists have shown that manipulating the same protein can enhance memory.

The protein – PKMzeta – is produced in the brain in response to learning, and it acts on the synapses – the active contact points between neurons. It continues to operate there long after the memory has been formed, suggesting that its function is tied not to learning (that is, absorbing information), but to keeping what is learned available in the long-term memory. In 2007, Prof. Yadin Dudai and research student Reut Shema of the Neurobiology Department, together with Prof. Todd Sacktor of SUNY Downstate Medical Center, New York, trained rats to avoid a specific taste and then blocked the activity of PKMzeta in their brains. While the control rats still had a strong aversion to the taste, even months after the training, those in which the activity of the protein was briefly blocked had no such qualms, appearing to have forgotten what they had learned.

But, could extra doses of PKMzeta actually improve memory? Investigating this claim turned out to be a more difficult prospect than blocking protein activity. Simply injecting the protein into the rats’ grey matter was not an option, as the brain is built to keep such extraneous material from reaching the neurons. So Dudai, Shema and Sacktor teamed up with Dr. Alon Chen and Sharon Haramati, also of the Neurobiology Department, to create harmless viruses that carry extra copies of the PKMzeta gene into the brain cells’ nucleus, tricking the neurons themselves into producing greater quantities of the protein.

Once again, they trained the rats to avoid the taste. Weeks after the training, the rats whose brains were churning out more of the proteins were much more likely to avoid the taste. In other words, an excess of PKMzeta effectively enhanced their memories. This is the very first demonstration that memories formed long ago can be augmented by manipulating a component of the memory machinery in the brain.

While the technique they developed is only suitable for the lab, the researchers hope that by shedding light on the function of this key component of the memory machinery, their findings might eventually point to ways of preventing or treating memory loss. Shema: “Our research is evidence that our brains are very plastic – even our long-term memories can be augmented.”
 
 
 
Overexpression of PKMzeta in the insular cortex. A merged picture of a neuron stained with GFP (green), PKMzeta (blue), and NeuN (red)
 
 
 
Prof. Yadin Dudai’s research is supported by the Nella and Leon Benoziyo Center for Neurological Diseases; the Abe and Kathryn Selsky Memorial Research Project; Miel de Botton Aynsley, UK; Dr. Henry Kaminer, New York, NY; Marla L. Schaefer, New York, NY; and Lisa Mierins Smith, Canada. Prof. Dudai is the incumbent of the Sara and Michael Sela Professorial Chair of Neurobiology.
 
Overexpression of PKMzeta in the insular cortex. A merged picture of a neuron stained with GFP (green), PKMzeta (blue), and NeuN (red)
Life Sciences
English
  • Alon Chen
  • Learning and memory
  • Long term memory
  • Neurobiology
  • Yadin Dudai

Weizmann Institute scientists discover: A Chemical Signal in Human Tears

English

 

Emotional crying is a universal, uniquely human behavior. When we cry, we clearly send all sorts of emotional signals. In a paper published online today in Science Express, scientists at the Weizmann Institute have demonstrated that some of these signals are chemically encoded in the tears themselves. Specifically, they found that merely sniffing a woman’s tears – even when the crying woman is not present – reduces sexual arousal in men.
 
 
 
 
Humans, like most animals, expel various compounds in body fluids that give off subtle messages to other members of the species. A number of studies in recent years, for instance, have found that substances in human sweat can carry a surprising range of emotional and other signals to those who smell them.
 
But tears are odorless. In fact, in a first experiment led by Shani Gelstein, Yaara Yeshurun and their colleagues in the lab of Prof. Noam Sobel in the Weizmann Institute’s Neurobiology Department, the researchers first obtained emotional tears from female volunteers watching sad movies in a secluded room and then tested whether men could discriminate the smell of these tears from that of saline. The men could not.
 
In a second experiment, male volunteers sniffed either tears or a control saline solution, and then had these applied under their nostrils on a pad while they made various judgments regarding images of women's faces on a computer screen. The next day, the test was repeated -- the men who were previously exposed to tears getting saline and vice versa. The tests were double blinded, meaning neither the men nor the researchers performing the trials knew what was on the pads. The researchers found that sniffing tears did not influence the men's estimates of sadness or empathy expressed in the faces. To their surprise, however, sniffing tears negatively affected the sex appeal attributed to the faces.
 
To further explore the finding, male volunteers watched emotional movies after similarly sniffing tears or saline. Throughout the movies, participants were asked to provide self-ratings of mood as they were being monitored for such physiological measures of arousal as skin temperature, heart rate, etc. Self-ratings showed that the subjects’ emotional responses to sad movies were no more negative when exposed to women’s tears, and the men “smelling” tears showed no more empathy. They did, however, rate their sexual arousal a bit lower. The physiological measures, however, told a clearer story. These revealed a pronounced tear-induced drop in physiological measures of arousal, including a significant dip in testosterone – a hormone related to sexual arousal.

Finally, in a fourth trial, Sobel and his team repeated the previous experiment within an fMRI machine that allowed them to measure brain activity. The scans revealed a significant reduction in activity levels in brain areas associated with sexual arousal after the subjects had sniffed tears.
 
Sobel: “This study raises many interesting questions. What is the chemical involved? Do different kinds of emotional situations send different tear-encoded signals? Are women’s tears different from, say, men's tears? Children’s tears? This study reinforces the idea that human chemical signals – even ones we’re not conscious of – affect the behavior of others.”
 
Human emotional crying was especially puzzling to Charles Darwin, who identified functional antecedents to most emotional displays -- for example, the tightening of the mouth in disgust, which he thought originated as a response to tasting spoiled food. But the original purpose of emotional tears eluded him. The current study has offered an answer to this riddle: Tears may serve as a chemosignal. Sobel points out that some rodent tears are known to contain such chemical signals. "The uniquely human behavior of emotional tearing may not be so uniquely human after all,” he says.
 
The work was authored by Shani Gelstein, Yaara Yeshurun, Liron Rozenkrantz, Sagit Shushan, Idan Frumin, Yehudah Roth and Noam Sobel, was conducted in collaboration with the Edith Wolfson Medical Center, Holon.
 
 
Prof. Noam Sobel’s research is supported by the James S. McDonnell Foundation 21st Century Science Scholar in Understanding Human Cognition Program; the Minerva Foundation; the European Research Council; and Regina Wachter, NY.
 
 
The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,600 scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.
 
Weizmann Institute news releases are posted on the World Wide Web at http://wis-wander.weizmann.ac.il/, and are also available at http://www.eurekalert.org/
 
Life Sciences
English
  • Neurobiology
  • Noam Sobel
  • Odor
  • Signaling
  • Smell

Brave Brains: Neural Mechanisms of Courage

English
 
The research, published by Cell Press in the June 24th issue of the journal Neuron, provides fascinating insight into what happens in the brain when an individual voluntarily performs an action opposite to that promoted by ongoing fear and may even lead to new treatment strategies for those who exhibit a failure to overcome their fear.
 
Although there is a substantial body of research examining brain mechanisms associated with fear, far less is known about the brain mechanisms associated with courage, defined here as action in the face of ongoing fear. ‘By gauging properly defined actions of either overcoming fear or succumbing to it in an acute controllable fearful situation, one can render certain neural substrates of courage amenable to investigation in a brain research laboratory setting,’ explains senior study author, Dr. Yadin Dudai from the Weizmann Institute of Science in Rehovot, Israel.
 
To study the neural mechanisms associated with moments of real-life courage, Dr. Dudai, Uri Nilli and their colleagues devised an experimental paradigm where participants had to choose whether to advance an object closer or farther away from them while their brain was scanned with functional magnetic resonance imaging (fMRI). The objects used in the study were either a toy bear or a live corn snake. Prior to the study, participants were categorized as ‘fearful’ or ‘fearless’ depending on how they responded to a validated snake-fear questionnaire.
 
As might be expected, the researchers observed that both high subjective fear and high somatic arousal were associated with succumbing to fear and moving the snake farther away. However, somewhat surprisingly, bringing the snake closer was associated with either high somatic arousal (assessed by skin conductance response) accompanied by low subjective fear (assessed by fear self-ratings) or high subjective fear accompanied by low somatic arousal.
 
Brain imaging during the task revealed that activity in a brain region called the subgenual anterior cingulate cortex (sgACC) correlated positively with the level of subjective fear when choosing to act courageously but not when choosing to succumb to fear. Further, activity in a series of temporal lobe structures was decreased when the level of fear increased and the individual chose to overcome their fear.
 
‘Our results propose an account for brain processes and mechanisms supporting an intriguing aspect of human behavior, the ability to carry out a voluntary action opposite to that promoted by ongoing fear, namely courage,’ concludes Dr. Dudai. ‘Specifically, our findings delineate the importance of maintaining high sgACC activity in successful efforts to overcome ongoing fear and point to the possibility of manipulating sgACC activity in therapeutic intervention in disorders involving a failure to overcome fear.’
 

Prof. Yadin Dudai’s research is supported by the Norman and Helen Asher Center for Human Brain Imaging; the Nella and Leon Benoziyo Center for Neurological Diseases; the Nella and Leon Benoziyo Center for Neurosciences; the Carl and Micaela Einhorn-Dominic Center for Brain Research; the Rowen Family Fund for Neurocognitive Research; the Abe and Kathryn Selsky Memorial Research Project; Miel de Botton Aynsley, UK; and Dr. Henry Kaminer, New York, NY. Prof. Dudai is the incumbent of the Sara and Michael Sela Professorial Chair of Neurobiology
 
 
 
 
 

 
The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,600 scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.
 
Weizmann Institute news releases are posted on the World Wide Web at http://wis-wander.weizmann.ac.il/, and are also available at http://www.eurekalert.org/ .
 
CONTACT: Yivsam Azgad, Tel: 972-8-934-3856/2
EMAIL: Yivsam.azgad@weizmann.ac.il / news@weizmann.ac.il

 
 

 
Life Sciences
English
  • Neural pathway›Neural mechanism
  • Yadin Dudai
  • fMRI

Weizmann Institute scientists discover: A Gene that Ties Stress to Obesity and Diabetes

English

The constant stress that many are exposed to in our modern society may be taking a heavy toll: Anxiety disorders and depression, as well as metabolic (substance exchange) disorders, including obesity, type 2 diabetes and arteriosclerosis, have all been linked to stress. These problems are reaching epidemic proportions: Diabetes, alone, is expected to affect some 360 million people worldwide by the year 2030. While anyone who has ever gorged on chocolate before an important exam understands, instinctively, the tie between stress, changes in appetite and anxiety-related behavior, the connection has lately been borne out by science, though the exact reasons for this haven’t been crystal clear.

 

Dr. Alon Chen of the Weizmann Institute’s Neurobiology Department and his research team have now discovered that changes in the activity of a single gene in the brain not only cause mice to exhibit anxious behavior, but also lead to metabolic changes that cause the mice to develop symptoms associated with type 2 diabetes. These findings were published online this week in the Proceedings of the National Academy of Sciences (PNAS).
 
All of the body’s systems are involved in the stress response, which evolved to deal with threats and danger. Behavioral changes tied to stress include heightened anxiety and concentration, while other changes in the body include heat-generation, changes the metabolism of various substances and even changes in food preferences. What ties all of these things together? The Weizmann team suspected that a protein known as Urocortin-3 (Ucn3) was involved. This protein is produced in certain brain cells -- especially in times of stress -- and it’s known to play a role in regulating the body’s stress response. These nerve cells have extensions that act as ‘highways’ that speed Ucn3 on to two other sites in the brain: One, in the hypothalamus - the brain’s center for hormonal regulation of basic bodily functions -- oversees, among other things, substance exchange and feelings of hunger and satiety; the other is involved in regulating behavior, including levels of anxiety. Nerve cells in both these areas have special receptors for Ucn3 on their surfaces, and the protein binds to these receptors to initiate the stress response.

 

The researchers developed a new, finely-tuned method for influencing the activity of a single gene in one area in the brain, using it to increase the amounts of Ucn3 produced in just that location. They found that heightened levels of the protein produced two different effects: The mice’s anxiety-related behavior increased, and their bodies underwent metabolic changes, as well. With excess Ucn3, their bodies burned more sugar and fewer fatty acids, and their metabolic rate sped up. These mice began to show signs of the first stages of type 2 diabetes: A drop in muscle sensitivity to insulin delayed sugar uptake by the cells, resulting in raised sugar levels in the blood. Their pancreas then produced extra insulin to make up for the perceived ‘deficit.’

 

‘We showed that the actions of single gene in just one part of the brain can have profound effects on the metabolism of the whole body,’ says Chen. This mechanism, which appears to be a ‘smoking gun’ tying stress levels to metabolic disease, might, in the future, point the way toward the treatment or prevention of a number of stress-related diseases.

 

Participating in the research were research students Yael Kuperman, Orna Issler, Limor Regev, Ifat Musseri, Inbal Navon and Adi Neufeld-Cohen, along with Shosh Gil, all of the Weizmann Institute’s Neurobiology Department. 


Dr. Alon Chen’s research is supported by the Nella and Leon Benoziyo Center for Neurosciences; the Carl and Micaela Einhorn-Dominic Brain Research Institute; the Croscill Home Fashions Charitable Trust; the Irwin Green Alzheimer's Research Fund; Gerhard and Hannah Bacharach, Fort Lee, NJ; Mark Besen and the Pratt Foundation, Australia; Roberto and Renata Ruhman, Sao Paulo, Brazil; and Barry Wolfe, Woodland Hills, CA. Dr. Chen is the incumbent of the Philip Harris and Gerald Ronson Career Development Chair.

 

The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,600 scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.

 

Weizmann Institute news releases are posted on the World Wide Web at http://wis-wander.weizmann.ac.il/, and are also available at http://www.eurekalert.org/.

Life Sciences
English
  • Alon Chen
  • Insulin›Insulin resistance
  • Metabolic disease
  • Neurobiology
  • Stress reaction
  • Type 2 diabetes

Scientists Have Developed Electronic 'Nose' That is Able to Predict the Pleasantness of Novel Odors

English
 
In research published in PLoS Computational Biology, the scientists argue that the perception of an odor’s pleasantness is innately hard-wired to its molecular structure, and it is only within specific contexts that personal or cultural differences are made apparent.These findings have important implications for automated environmental toxicity and malodor monitoring, fast odor screening in the perfume industry, and provide a critical building block for the Holy Grail of sense technology – transmitting scent digitally.

 

Over the last decade, electronic devices, commonly known as electronic noses or ‘eNoses,’ have been developed to be able to detect and recognize odors. The main component of an eNose is an array of chemical sensors. As an odor passes through the eNose, its molecular features stimulate the sensors in such a way as to produce a unique electrical pattern – an ‘odor fingerprint’ – that characterizes that specific odor. Like a sniffer dog, an eNose first needs to be trained with odor samples so as to build a database of reference. Then the instrument can recognize new samples of those odors by comparing the odor’s fingerprint to those contained in its database.

 

But unlike humans, if eNoses are presented with a novel odor whose fingerprint has not already been recorded in their database, they are unable to classify or recognize it.

 

So a team of Weizmann scientists, led by Dr. Rafi Haddad, then a graduate student of Prof. Noam Sobel of the Neurobiology Department and co-supervisor Prof. David Harel of the Computer Science and Applied Mathematics Department, together with their colleague Abebe Medhanie of the Neurobiology Department, and Dr. Yehudah Roth of the Edith Wolfson Medical Center, Holon, decided to approach this issue from a different perspective. Rather than train an eNose to recognize a particular odor, they trained it to estimate the odor along a particular perceptual axis. The axis they chose was odorant pleasantness. In other words, they trained their eNose to predict whether an odor would be perceived as pleasant or unpleasant, or anywhere in between.

 

To achieve this, the scientists first asked a group of native Israelis to rate the pleasantness of a selection of odors according to a 30-point scale ranging from ‘very pleasant’ to ‘very unpleasant.’ From this dataset, they developed an ‘odor pleasantness’ algorithm, which they then programmed into the eNose. The scientists then got the eNose to predict the pleasantness of a completely new set of odors not contained in their database against the ratings provided by a completely different group of native Israelis. The scientists found that the eNose was able to generalize and rate the pleasantness of novel odors it never smelled before, and these ratings were about 80% similar to those of naive human raters who had not participated in the eNose training phase. Moreover, if the odors were simply categorized as either ‘pleasant’ or ‘unpleasant,’ as opposed to being rated on a scale, it achieved an accuracy of 99%.

 

But these findings still don’t determine whether olfactory perception is culture-specific or not.  With this in mind, the scientists decided to test eNose predictions against a group of recent immigrants to Israel from Ethiopia. The results showed that the eNose’s ability to predict the pleasantness of novel odors against the native Ethiopians’ ratings was just as good, even though it was ‘tuned’ to the pleasantness of odors as perceived by native Israelis. In other words, even though different odors have different meanings across cultures, the eNose performed equally well across these populations. This suggests a fundamental cross-cultural similarity in odorant pleasantness.

 

Sobel: ‘Being able to predict whether a person who we never tested before would like a specific odorant, no matter their cultural background, provides evidence that odor pleasantness is a fundamental biological property, and that certain aspects of molecular structure are what determine whether an odor is pleasant or not.’ So how are cultural differences accounted for? ‘We believe that culture influences the perception of olfactory pleasantness mostly in particular contexts. To stress this point, many may wonder how the French can like the smell of their cheese, when most find the smell quite repulsive. We believe that it is not that the French think the smell is pleasant per se, they merely think it is a sign of good cheese. However, if the smell was presented out of context in a jar, then the French would probably rate the odor just as unpleasant as anyone else would.’

 

The scientists’ findings that odor perception is hard-wired to molecular structure and their design of an eNose that is able to classify new odors could provide new methods for odor screening and environmental monitoring, and may, in the future, allow for the digital transmission of smell to scent-enable movies, games and music to provide a more immersive and captivating experience.

 

Prof. Noam Sobel’s research is supported by the Nella and Leon Benoziyo Center for Neurosciences; the J&R Foundation; and Regina Wachter, New York.

This research was funded by an FP7 grant from the European Research Council awarded to Noam Sobel.

 

The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,600 scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.

 

Weizmann Institute news releases are posted on the World Wide Web at http://wis-wander.weizmann.ac.il/, and are also available at http://www.eurekalert.org/.

Life Sciences
English
  • Neurobiology
  • Noam Sobel
  • Smell

Aiming to the Side

English


The best way to track a moving object with a flashlight might be to aim it to one side, catching the object in the edge of the beam rather than the center. New research at the Weizmann Institute of Science reveals that bats, which ‘see’ with beams of sound waves, skew their beams off-center when they want to locate an object. The research, which recently appeared in Science, shows that this strategy is the most efficient for locating objects.

 
Dr. Nachum Ulanovsky and postdoctoral fellow Dr. Yossi Yovel of the Institute’s Neurobiology Department knew that bat sonar (or echolocation) obeys the same physical laws as the sonar on a submarine: The bats (or ships) emit a sound and listen for the echo, accurately judging the type and location of objects around them by the changes in the sound waves as they’re reflected back. But there’s a trade-off between detection and localization. The beam is most intense in the center, returning more information, which is good for detection; but localization is better done on the slope, where the intensity drops off as the signal spreads out, making it easier to follow movement across the beam.

Are bats able to choose the best echolocation strategy? Ulanovsky and Yovel, in collaboration with Prof. Cynthia Moss and research student Ben Falk from the University of Maryland, trained bats to locate and land on a black sphere placed randomly in a completely dark room, using echolocation alone. A string of special microphones arrayed around the room’s walls traced the bats’ sound waves, while two infrared video cameras tracked their flight patterns.

The Egyptian fruit bats in Ulanovsky’s lab produce their signals in pairs of clicks. The researchers identified a pattern: The first set of double clicks was aimed left, and then right, and the next set right, then left. As the bats closed in for a landing, they continued to throw their sound beams to alternate sides of the sphere, just where a mathematical formula for sonar sensing predicted they would be most effective. As the sphere was easily detectable, the bat’s optimal strategy was one of localization. To test a situation in which detection was needed as well as localization, the scientists installed a large panel behind the sphere that echoed the sound waves back to the bats’ ears. Now they had to find the sphere’s echo amidst conflicting signals. This time, as the bats approached their target, they began to narrow their sweep and aim the beams more or less directly toward the sphere.

Many types of sensation, from echolocation in dolphins to sniffing in dogs to human eye movements, are based on some sort of active sensing. Ulanovsky and Yovel believe that what works for bats may well work for other animals: ‘sensing on the slope’ could play a role in all of these and others.

Dr. Nachum Ulanovsky's research is supported by the Nella and Leon Benoziyo Center for Neurological Diseases; the Carl and Micaela Einhorn-Dominic Brain Research Institute; the J&R Foundation; and the A.M.N. Fund for the Promotion of Science, Culture and Arts in Israel.
 
 
 

The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,600 scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.

Weizmann Institute news releases are posted on the World Wide Web at http://wis-wander.weizmann.ac.il/, and are also available at http://www.eurekalert.org/


 
Life Sciences
English
  • Bats
  • Echolocation
  • Nachum Ulanovsky
  • Sensory stimulus

To See or Not to See

English

How do the visual images we experience, which have no tangible existence, arise out of physical processes in the brain? New research at the Weizmann Institute of Science provided evidence, for the first time, that an ‘ignition’ of intense neural activity underlies the experience of seeing.

 
In research recently published in the journal Neuron, Prof. Rafael Malach and research student Lior Fisch of the Weizmann Institute’s Neurobiology Department worked with a neurosurgeon, Dr. Itzhak Fried of Tel-Aviv Sourasky Medical Center, a distinguished team of medical doctors from the Center and Weizmann Institute students. They asked a group of epileptic patients who had had electrodes clinically implanted into their brains in preparation for surgery to volunteer for some perceptual awareness tasks.
 
The subjects looked at a computer screen, which briefly presented a ‘target’ image – a face, house, or man-made object. This image was followed by a ‘mask’ – a meaningless picture for distraction – at different time intervals after the target image had been presented. This allowed the experimenter to control the visibility of the images – the patients sometimes recognized the targets and sometimes failed to do so. By comparing the electrode recordings to the patients’ reports of whether they had correctly recognized the image or not, the scientists were able to pinpoint when, where and what was happening in the brain as transitions in perceptual awareness took place.
 
Malach: ‘We found that there was a rapid burst of neural activity occurring in the high-order visual centers of the brain – centers that are sensitive to entire images of objects, such as faces – whenever patients had correctly recognized the target image.’ The scientists also found that the transition from not seeing to seeing happens abruptly. Fisch: ‘When the mask was presented too soon after the target image, it ‘killed’ the visual input signals, resulting in the patients being unable to recognize the object. The patients suddenly became consciously aware of the target image at a clear threshold, suggesting that the brain needs a specific amount of time to process the input signals in order for conscious perceptual awareness to be ‘ignited.’’
 
This study is the first of its kind to uncover strong evidence linking ‘ignition’ of bursts of neural activity to perceptual awareness in humans. More questions remain: Is this the sole mechanism involved in the transition to perceptual awareness? To what extent is it a local phenomenon? By answering such questions, we might begin bridging the mysterious gap between mind and the brain.  
 
Prof. Rafael Malach’s research is supported by the Nella and Leon Benoziyo Center for Neurological Diseases; the Carl and Micaela Einhorn-Dominic Brain Research Institute; the S. and J. Lurje Memorial Foundation; the Benjamin and Seema Pulier Charitable Foundation, Inc; Vera Benedek, Israel; and Mary Helen Rowen, New York, NY. Prof. Malach is the incumbent of the Barbara and Morris Levinson Professorial Chair in Brain Research.
 
The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,600 scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.
 
Weizmann Institute news releases are posted on the World Wide Web at http://wis-wander.weizmann.ac.il/, and are also available at http://www.eurekalert.org/.
Life Sciences
English
  • Consciousness
  • Perception
  • Rafael Malach
  • Vision

Memory Machine

English

The process of storing long-term memories might involve a miniature molecular machine that must run constantly to keep memories going

 

 

What happens in our brains when we learn and remember? Are memories recorded in a stable physical change, like writing an inscription permanently on a clay tablet?  Prof. Yadin Dudai, Head of the Weizmann Institute’s Neurobiology Department, and his colleagues are challenging that view. They recently discovered that the process of storing long-term memories is much more dynamic, involving a miniature molecular machine that must run constantly to keep memories going. They also found that jamming the machine briefly can erase long-term memories. Their findings, which appeared today in the journal Science, may pave the way to future treatments for memory problems.

 

Dudai and research student Reut Shema, together with Todd Sacktor of theSUNY Downstate Medical Center, trained rats to avoid certain tastes. They then injected a drug to block a specific protein into the taste cortex – an area of the brain associated with taste memory. They hypothesized, on the basis of earlier research by Sacktor, that this protein, an enzyme called PKMzeta, acts as a miniature memory 'machine' that keeps memory up and running. An enzyme causes structural and functional changes in other proteins: PKMzeta, located in the synapses – the functional contact points between nerve cells – changes some facets of the structure of synaptic contacts. It must be persistently active, however, to maintain this change, which is brought about by learning. Silencing PKMzeta, reasoned the scientists, should reverse the change in the synapse. And this is exactly what happened: Regardless of the taste the rats were trained to avoid, they forget their learned aversion after a single application of the drug. The technique worked as successfully a month after the memories were formed (in terms of life span, more or less analogous to years in humans) and all signs so far indicate that the affected unpleasant memories of the taste had indeed disappeared. This is the first time that memories in the brain were shown to be capable of erasure so long after their formation.

 

'This drug is a molecular version of jamming the operation of the machine,' says Dudai. 'When the machine stops, the memories stop as well.' In other words, long-term memory is not a one-time inscription on the nerve network, but an ongoing process which the brain must continuously fuel and maintain. These findings raise the possibility of developing future, drug-based approaches for boosting and stabilizing memory.


Prof. Yadin Dudai's research is supported by the Norman and Helen Asher Center for Brain Imaging; the Nella and Leon Benoziyo Center for Neurosciences; the Carl and Micaela Einhorn-Dominic Brain Research Institute; the Irwin Green Alzheimer's Research Fund; and the Sylvia and Martin Snow Charitable Foundation. Prof. Dudai is the incumbent of the Sara and Michael Sela Professorial Chair of Neurobiology.


The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,600 scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.


Weizmann Institute news releases are posted on the World Wide Web at
http://wis-wander.weizmann.ac.il, and are also available at http://www.eurekalert.org

Life Sciences
English
  • Long term memory
  • Synapse
  • Yadin Dudai

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