Odor Recognition & Brute-Force Conversions

Frontiers in Computational Neuroscience will be publishing an interesting paper written by Honi Sanders and John Lisman (with co-authors Brian E. Kolterman, Roman Shusterman, Dmitry Rinberg, Alexei Koulakov) titled, “A network that performs brute-force conversion of a temporal sequence to a spatial pattern: relevance to odor recognition“. Honi Sanders has written a preview of this paper.

by Honi Sanders

Lisman_ProvisionalPDF_BLThere are many occasions in which the brain needs to process information that is provided in a sequence. These sequences may be externally generated or internally generated. For example, in the case of understanding speech, where words that come later may affect the meaning of words that come earlier, the brain must somehow store the sentence it is receiving long enough to process the sentence as a whole. On the other hand, sequences of information also are passed from one brain area to another.  In these cases too the brain must store the sequence it is receiving long enough to process the message as a whole.

One such sequence is generated by the olfactory bulb, which is the second stage of processing of the sense of smell.  While individual cells in the olfactory bulb will fire bursts in response to many odors, the order in which they fire is specific to an individual odor. How such a sequence can be recognized as a specific odor remains unclear.  In Sanders et al, we present experimental evidence that the sequence is discrete and therefore contains a relatively small number of sequential elements; each element is represented in a given cycle of the gamma frequency oscillations that occur during a sniff. This raises the possibility of a “brute force” solution for converting the sequence into a spatial pattern of the sort that could be recognized by standard “attractor” neural networks.  We present computer simulations of model networks that have modules; each model can produce a persistent snapshot of what occurs during a given gamma cycle. In this way, the unique properties of the sequence can be determined at the end of sniff by the spatial pattern of cell firing in all modules.

The authors thank Brandeis University High Performance Computing Cluster for cluster time. This work was supported by the NSF Collaborative Research in Computational Neuroscience, NSF IGERT, and the Howard Hughes Medical Institute.

Gina Turrigiano Named One of the “30 Most Influential Neuroscientists Alive Today”

Gina Tturrigiano405urrigiano has been named one of the “30 Most Influential Neuroscientists Alive Today” by the Online Psychology Degree Guide.

The guidelines for selecting the neuroscientists include: leadership, applicability (neuroscientists that have created technologies that have improved people’s lives); awards & recognition by the international science community and other notable accomplishments such as personal or educational achievements.

Gina Turrigiano is the author of numerous papers, has been awarded a MacArthur Foundation fellowship and the HFSP Nakasone Award, and in 2013 was elected to the National Academy of Sciences.

Men, Women and Emotional Stress Responses

Psychoneuroendocrinology (November 2014) is publishing a fascinating paper authored by Sarah Lupis, Michelle Lerman and Jutta Wolf titled Anger responses to psychosocial stress predict heart rate and cortisol stress responses in men but not women.

473People can experience a wide range of emotions when under stress, including feelings of anger and fear. In recent years researchers have sought to understand how these emotion stress responses are linked to biological stress responses. In particular, some evidence suggests that anger and fear may be linked to cardiovascular changes in differential ways. It is less clear, however, how emotions during stress may predict increases in levels of the stress hormone cortisol. These deficits in our understanding are partly due to the methodological difficulties in measuring emotion in the context of stress. Much prior research has relied solely on retrospective self-report (after the stress has passed, a questionnaire asks a study participant to reflect on how he felt in the moment of stress). By this time, the participant may have forgotten how he felt, or may already be utilizing coping strategies to process those emotions. In addition, he may not feel comfortable reporting how the stressor made him feel, leading to less-than-honest responses. Unsurprisingly, prior research has not shown consistent links between these self-report measures and biological stress responses. In the current study, we therefore added facial coding of emotion expression to assess emotions occurring during stress. Our aim was to determine how expressions of anger and fear were linked to heart rate and cortisol stress responses.

We recruited 32 healthy Brandeis students and exposed them to a brief psychosocial stressor. A certified coder assessed facial expressions shown during the stressful situation. Heart rate and cortisol levels were measured throughout. After the stressor, the participants also self-reported how they felt during the stressor. A first notable finding showed that what participants self-reported feeling and the expressions they actually showed did not correlate. With regards to self-report, men who reported feeling fear showed blunted cortisol stress responses. Consistent with prior research, self-report was otherwise not associated with heart rate or cortisol stress responses. When looking at facial expressions, a consistent pattern appeared: men who showed more anger during the stressful situation also showed exaggerated heart rate and cortisol stress responses. For women, neither anger nor fear were linked to biological stress responses (see Figure).

Our findings first emphasize the importance of assessing emotion using multiple means. In this case, facial expressions revealed an emotion-stress link for males that would not be apparent using self-report alone. Facial coding may thus be a useful addition to current stress paradigms. Further, if men who react with anger in stressful situations do respond with exaggerated stress responses, it could have important down-stream health effects. Exaggerated, prolonged, or dysfunctional stress responses could, over time, lead to changes in basal stress systems. This kind of ‘allostatic load’ is associated with negative health outcomes including diabetes and cardiovascular disease. Anger and fear do not seem to drive these responses in females, and further study is needed to determine if similar relationships exist for a different set of emotions, perhaps self-conscious emotions like shame. By better understanding these relationships, more healthful ways of coping with stress can be developed, which is particularly important given that for many, stress has become an unavoidable part of daily life.


The “Fly on the Wall” Blog

fruit_fly_drawingBethany Christmann, a Neuroscience Ph.D. student in Leslie Griffith’s lab at Brandeis University has created a blog titled Fly on the Wall. The blog’s purpose is to introduce fly science to a broader audience of non-fly scientists. Check it out if you want to learn more about fly life, current research and how fruit fly research has already made huge contributions to understanding human biology and will continue to do so in the future.

Learn more about research in the Griffith Lab.


Why we love basic research

Brandeis PhD students Jonathan Napoline (Graduate Program in Chemistry, Thomas lab) and Sara Haddad (Graduate Program in Neuroscience, Marder lab) tell PBS NewsHour why they’re excited about basic research



Deep inside a worm’s nose

In a new paper in eLIFE, a team spearheaded by Brandeis postdocs David Doroquez and Cristina Berciu provide a strikingly detailed look at key structures called cilia on neurons involved in sensory perception in the nematode C. elegans. Primary cilia are the antenna-like structures onsensory neurons that gather information about the animal’s environment, such as chemicals, temperature, humidity, and touch. The genetic tools available to manipulate individual, identifiable neurons in C. elegans make worms an excellent model organism to study the assembly and function of cilia. This study requires a description of the structure of the cilia and their immediate surrounding glial support cells, and this new paper, a collaboration of the Sengupta and Nicastro labs, provides high-resolution 3D models showing how diverse and specialized these structures are.


A bouquet of sensory antennae. The 3D ultrastructure of all sensory cilia
and other neuronal projections in the head of the soil roundworm C.
elegans have been reconstructed using serial section transmission electron
microscopy. Shown are 3D isosurface-rendering models emerging from a
transmission electron microscopic cross-section of the worm.

The key techniques in this study were serial section transmission electron microscopy and electron tomography, with structures well-preserved by high-pressure freezing and freeze-substitution. With these techniques, the authors achieved the first high-resolution 3D reconstructions of 50/60 cilia from C. elegans. They describe several previously uncharacterized features — for example, there are distinct types of branching patterns – in one, the two cilia originate from independent basal bodies (as previously seen in Chlamydomonas). In the second, the cilia branch after the basal transition zone, the ciliary gatekeeper region. In the latter case, this basically means that whatever is needed for the cilia to branch has to be transported through the transition zone, suggest there might be novel mechanisms of ciliary protein trafficking. In a third pattern, the branching occurs proximally before the transition zone, and represent therefore dendritic microvilli, rather than ciliary branching. The study also showed different organizations  of microtubules in different cilia types and vesicles in regions of the cilia which have never been seen before, again pointing to new mechanisms of protein transport. They also describe new cilia-glial interactions, which might suggest that cilia and glia talk to each other.

For more about these structures (with lots of pretty pictures and movies), see:

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