The Amygdala, Fraud and Older Adults

Figure from Zebrowitz-Gutchess paper

Figure 1. Peak amygdala activation as a function of face trustworthiness for older adult participants. Error bars represent standard errors. COPE is the contrast of parameter estimates [high or medium, or low trustworthy faces minus baseline fixation] from which peak values were extracted at the subject-level using FSL featquery. * p < .05.

There is a widespread belief that older adults are more vulnerable to consumer fraud than younger adults. Behavioral evidence supporting this belief is mixed, although there is a reliable tendency for older adults to view faces as more trustworthy than do younger adults.  One study provided supporting neural evidence by demonstrating that older adults failed to show greater amygdala activation to low than high trustworthy faces, in contrast to considerable evidence that younger adults do show this effect. This result is consistent with the argument for greater vulnerability to fraud in older adults, since the amygdala responds to threatening stimuli. More generally, however, the amygdala responds to biologically salient stimuli, and many previous studies of younger adults have shown that this includes not only threatening, low trustworthy faces, but also high trustworthy faces. The Zebrowitz Face Perception Lab therefore included medium trustworthy faces in order to detect separate effects of high trustworthiness and low trustworthiness on amygdala activation in older adults, something that the one previous study of older adults did not do. Consistent with that study we found that older adults did not show stronger amygdala activation to low than high trustworthy faces.  However, they did show stronger amygdala activation to high than to medium trustworthy faces, with a similar trend for low vs medium, although that difference was not strong enough to be confident that it would replicate (See Figure 1).

The fact that older adults did not show greater amygdala activation to low than medium or high trustworthy faces is consistent with the suggestion that older adults may be more vulnerable to fraud. However, an important question is whether vigilant responding to untrustworthy-looking faces could actually protect one from fraud.  Arguing against this possibility is the finding that although younger adults have consistently shown greater amygdala activation to people who look untrustworthy, they do not show greater activation to those who actually cheat.  On the other hand, some evidence indicates that facial appearance does provide valid cues to threat. Face shape not only influenced younger adults’ trust of potential exploiters, but it also proved to be a valid indicator of economic exploitation.  Furthermore, this face shape cue influenced both younger and older adults’ accurate impressions of aggressiveness. To shed further light on neural mechanisms for any age differences in vulnerability to fraud that may exist requires investigating: 1) the sensitivity of neural responses to actual differences in trustworthiness in the domain of economic exploitation, and 2) whether any age differences in those neural responses are related to differential vulnerability to economic exploitation.

Zebrowitz, L.A., Ward, N., Boshyan, J., Gutchess, A., & Hadjikhani, N. (2017).  Older adults’ neural activation in the reward circuit is sensitive to face trustworthiness.  Cognitve, Affective, and Behavioral Neuroscience.



To Get The Girl, You Have To Listen… No, Smell!

KC and the Sunshine band were prophetic when they wrote the song Get Down Tonight in ways that they never could have imagined. In the tiny social world of fruit fly courtship, the directive ‘do a little dance, make a little love’ is right on target. And just like in a dance club, what is said and when/how it is said are important to the success of fly hookups.

In ways not that dissimilar to humans, Drosophila melanogaster fruit flies meet at a singles bar commonly known as a fallen piece of overripe fruit. As the prospects congregate, there is a lot of information that is exchanged. Males use their wings to sing at short distances to the ladies milling about, giving persistent shouts of: (1) “Hey!” and (2) “How you doin’?”. When a female slows her pace to one of these calls from the dance floor, the male can then move in and cut out the ‘Hey’ portion of the call, and just use the more intimate “How you doin’?” signal. If she is still receptive, the male will dance a little closer, touching her butt and showing off his best moves until an eventual one-night-stand is awarded for his efforts. This interesting human/fruit fly parallel shows just how universal mating strategies are, even across 500 million years of evolution.

Also in similar fashion, when a miscommunication occurs, males have a much more difficult time obtaining a mate. The recent paper by Trott et al. (PLoS ONE, 2012) shows that the distance and timing of the two signals is critical to male mating success. Female fruit flies give off a chemical signal (like perfume!) to courting males, telling them that they’re interested, and the distance that the female lingers from the male is reinforcement to the male’s advances. Males who are deficient in their ability to smell due to an olfactory mutation also have a difficult time switching to a dominant “How you doin’?” signal. Without a functioning olfactory feedback mechanism, the male is unable to make the proper adjustments to his signal. For the female, it’s kind of like trying to have a one-on-one conversation with a male that is still trying to pick up every other female in the room. Even though the male is handsome/strong/free of parasites, interest from the female quickly wanes when he keeps giving the wrong signal. All the parts of the song are there; he just can’t read the cues.

So next time you’re out busting a move on the dance floor, think of the noble fruit fly passionately conducting it’s own miniature fandango. What is said is just as important as the moves that are made. And being able to read feedback is crucial to success. In a strange homage to Cyrano de Bergerac, it’s the male fruit fly that uses its ‘nose’ to speak sweet nothings that is best able to woo the female.

Trott AR, Donelson NC, Griffith LC, Ejima A (2012) Song Choice Is Modulated by Female Movement in Drosophila Males. PLoS ONE 7(9): e46025. doi:10.1371/journal.pone.0046025

Alexander Trott ’10 and postdocs Nathan Donelson and Aki Ejima worked on Drosophila courtship together with Prof. Leslie Griffith at Brandeis. Aki is now an Assistant Professor at Kyoto University. Alex is currently a graduate student at Harvard Medical School.

Video courtesy of Dr. Aki Ejima

How many neurons does it take to stay cool?

The worm (nematode) C. elegans is a nice model system for studying neuroscience, combining

  • genetic tools that allow genes to be turned on or off, often on a per cell basis, in the whole organism,
  • tools like laser or genetic ablation that allow individual, identified cells to be selectively eliminated,
  • robust behaviors that can be readily measured, and
  • a well defined nervous system consisting of 302 neurons, each of which can be identified, and whoseanatomical connectivity has been established.

In a paper appearing this month in Journal of Neuroscience, Molecular and Cell Biology grad student Matthew Beverly, undergrad Sriram Anbil, and Professor of Biology Piali Sengupta examined the contribution of sensory neurons to controlling thermotaxis in C. elegans. Worms develop a memory of the temperature at which they have been cultivated, and display a robust behavior in which worms placed on a temperature gradient at temperatures higher than their cultivation temperature will crawl back towards colder temperature (negative thermotaxis – see movie). The behavior depends on TAX-4, a channel protein expressed in a subset of the sensory neurons. In this study, the Brandeis researchers asked the question “how many and which of the sensory neurons are required for the worms to perform negative thermotaxis, and are the required sensory neurons the same regardless of the temperature range examined?” (or, in my paraphrase, “how many and which neurons does it take to stay cool?”)

Worm head, showing expression of the calcim indicator GCaMP in ASI and AWA neurons (used in calcium imaging experiments)

As it turns out, the answer is complicated (and readers are encouraged to read the paper). The researchers found that in addition to the previously known thermosensory neurons AFD and AWC, the ASI neurons previously known to be involved in chemosensation play a significant role in regulating negative thermotaxis. Interestingly, the circuits used seem to be degenerate; under one condition, for example, a particular combination of AFD, AWC or ASI is necessary to generate the behavior, although at other conditions, a different combination is required to generate the same behavior.. And only a couple of degrees Celsius makes a difference — the circuit required for negative thermotaxis on a gradient centered at 8oC above the cultivation temperature is different from a gradient centered at 6oC above.

These and other results taken together suggest that even in the worm, a complex circuit has evolved to control crawling behaviors to cope with temperature changes, and that having degeneracy in the underlying circuits may be a common feature that ensures that behaviors crucial to survival are maintained in a variety of environmental conditions..

Beverly M, Anbil S, Sengupta P. Degeneracy and Neuromodulation among Thermosensory Neurons Contribute to Robust Thermosensory Behaviors in Caenorhabditis elegans. J Neurosci. 2011;31(32):11718-27.

New courses, Fall 2011

New courses offered in the Division of Science in Fall, 2011:

BISC 9B Biology of Cancer (Dore)

Introduces the fundamental aspects of cancer development, progression and treatment with an emphasis on the cellular and molecular changes thought to lead to cancer. Both genetic and lifestyle factors and their impact on the predisposition to develop and recover from cancer will be discussed. Usually offered every year.

CBIO 101A  Chemical Biology (Pontrello)

Chemical biology is not just biochemistry, and the subject involves much more than a simple combination of chemistry and biology topics. This course will explore how recent cutting edge scientific work in chemistry has led to a deeper fundamental understanding of and ability to manipulate biological processes. Emphasis will be placed on the design and chemical synthesis of micro and macromolecular structures that allow scientists to ask unique chemical and biological questions as well as to control biological systems. Both synthetic strategies and characterization as well as biological evaluation and utility will be discussed. The course will consist of scientific literature readings, periodic assignments and exams based on literature and lecture content, as well as group projects and exercises. A textbook is not required, although retention of prerequisite course textbooks is strongly recommended. Topics will range from fluorescent probes, chemical inducers of dimerization, bacterial chemotaxis, controlling stem cell differentiation, solid phase synthesis, synthetic nucleotides, B cell activation, and chemical-inducers of dimerization, just to name a few.

This is not an introductory science course, and the structure will be designed to enhance student understanding of the subject through primary literature and group discussion and review. After several instructor lectures covering general chemistry and biology background, each class will be structured around student presentations of assigned primary scientific literature as a starting point for class discussion about the area of research. The course will also include a project where each student will search chemical biology journals, select a recent article they find interesting, and prepare a report explaining background, fundamental chemistry and biology addressed in the paper, results and applications, and also future directions and implications for the field. The final exam will be based on the content of this collective work.

BCHM 104A Physical Chemistry of Macromolecules I (C.Miller, Oprian)

Covers basics of physical chemistry underpinning applications in BCHM 104b. Focus is placed on quantitative treatments of the probabilistic nature of molecular reality: molecular kinetic theory, basic statistical mechanics, and chemical thermodynamics in aqueous solution. Usually offered every second year

BIOL 107A Data Analysis and Statistics Workshop (Van Hooser)

The interpretation of data is key to making new discoveries, making optimal decisions, and designing experiments. Students will learn skills of data analysis through hands-on, computer-based tutorials and exercises that include experimental data from the biological sciences. Knowledge of very basic statistics (mean, median) will be assumed. Usually offered every second year.

BCHM 172A Cholesterol in Health and Disease (Westover)

In today’s supermarkets, many foods are proudly labeled “cholesterol-free.” 1in 4 Americans over 45 take medicine to lower their cholesterol levels.  Yet, every beginning biology student learns that cholesterol is an essential component of mammalian cell membranes.

This fall, the Biochemistry Department’s Emily Westover will teach a new course called Cholesterol in Health and Disease, BCHM 172a. Drawing from the current literature, students in this course will explore many facets of cholesterol science.  This course will be case study in cholesterol, bringing together concepts from a variety of disciplines, including cell biology, biophysics, biochemistry, physiology and medicine.

The class will address questions such as:

  • How does the body balance production and dietary uptake of cholesterol?
  • What effects does cholesterol have on membrane and protein function?
  • What is the connection between cholesterol and atherosclerosis?

BCHM 172 will meet Tuesdays at 2 pm in the 4th floor Ros-Kos Conference Room.

NBIO 157A Project Laboratory in Neurobiology and Behavior (Vecsey)

What is it like to be a scientist?

Many college science courses don’t help students answer that question. In lecture courses, a host of scientific facts are taught via textbook, but at the end of the course students have read little if any primary research, and would be hard-pressed to explain in detail how those facts were discovered. Courses with labs often have “recipe books” that lay out all of the necessary ingredients and steps required to achieve a desired experimental result. Even students who try to get scientific training by working in a lab may at first be relegated to perform menial tasks that are not fully representative of the scientific process.

With all of this in mind, Brandeis University introduced a series of courses called Project Labs. In these courses, students carry out legitimate research projects in a range of disciplines. No cookbooks, no expected outcomes. We start with an introduction to a biological question, and then set about answering it. We read primary literature to understand the basis for the research we will carry out, and we write up the results in a true journal format.

The newest installment in the Project Lab series is Bio157a, the Project Lab in Neurobiology and Behavior. In this course, the ultimate goal is to understand how an animal like the fruit fly senses and responds to temperature. Specifically, we will examine temperature preference behavior in Drosophila melanogaster and several related species. Some of those species are native to cold climates, whereas others hail from deserts such as the Mojave. Have these species evolved to prefer different temperatures? Or are they simply more tolerant of those temperatures? These are some of the core questions that we will address. What the results will be we can only guess – and that’s what it’s like to be a scientist!

Learning from unexpected events

Have you ever heard the phrase ‘the eyes are a window to the soul’? New research from Dr. Robert Sekuler’s Vision Lab suggests that the eyes may be a window to the brain as well. In an article published in this month’s issue of the Journal of Vision, Neuroscience grad student Jessica Maryott (PhD ’09) and Psychology grad student Abigail Noyce showed that as participants learn, their eye movements change in a way that lets scientists investigate how that learning takes place, specifically in response to unexpected events.

Participants in the study watched as a disk moved on a computer screen in a zig-zag path; they then reproduced its trajectory from memory. Each path was repeated several times, allowing the researchers to examine the learning process as participants became familiar with the pattern and more accurate at reproducing it. Researchers also measured participants’ eye movements as they watched the disk move, and examined learning-related changes in those as well. The results suggest that eye movements reflect the participant’s level of learning by actually predicting where the disk will be going next.

Sometimes, part of the disk’s path changed after several repetitions going in the opposite direction (a 180 degree change, shown in the green trace on the figure), without warning to the participant. This caused participants to make a prediction error: the actual motion of the disk no longer matched the pattern they had learned, but their eyes moved in the direction of the expected movement (positive velocity) until they were able to correct the error (this is when the green trace reverses velocity and goes below 0 in the figure). After such a prediction error, when the pattern appeared again, participants’ eye movements showed that the previous prediction error produced fast ‘one-shot’ learning, and participants now expected to see the new version of the path (shown in the blue trace, which goes in the new expected direction, 180 degrees from the old – thus showing a negative velocity). The researchers concluded that unexpected events (like the induced error) have high salience for learning. These results suggest that humans have a cognitive system which monitors how well sensory input matches predictions, and responds to errors with sudden, strong learning about the new situation.

Sex-specificity of behavior in the fruit fly

What makes a male fly act like a guy?

Adriana Villella and Jeff Hall discuss the neurogenetics of courtship and mating in Drosophila in a new review.

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