How to create neural circuit diagrams (updated)

nmeth.3777-F3

My diagrams are always a mess, but maybe I could start following this advice a little more carefully?

Diagrams of even simple circuits are often unnecessarily complex, making understanding brain connectivity maps difficult…Encoding several variables without sacrificing information, while still maintaining clarity, is a challenge. To do this, exclude extraneous variables—vary a graphical element only if it encodes something relevant, and do not encode any variables twice…

For neural circuits such as the brainstem auditory circuits, physical arrangement is a fundamental part of function. Another topology that is commonly necessary in neural circuit diagrams is the laminar organization of the cerebral cortex. When some parts of a circuit diagram are anatomically correct, readers may assume all aspects of the figure are similarly correct. For example, if cells are in their appropriate layers, one may assume that the path that one axon travels to reach another cell is also accurate. Be careful not to portray misleading information—draw edges clearly within or between layers, and always clearly communicate any uncertainty in the circuit.

Update: Andrew Giessel pointed me to this collection of blog posts from Nature Methods on how to visualize biological data more generally. Recommended!

How social status affects your brain

When you get into work in the morning, you might say hi to your coworkers and complain for awhile about your boss.  Then maybe you joke with the janitor, only to flee when you see your boss headed to your desk.  Each of these interactions – as is every interaction between individuals -is deeply embedded in the context of social status.  Social status isn’t just a construct of our world, but a state of our environment that causes profound changes in the way your brain functions.

One way social status affects the brain is through serotonin; it is well known in the scientific literature that changes in serotonin level seems to directly affect perceived social status.  Whether high social status depends on high or low serotonin depends on the species; dominant individuals of species who must fight to retain social status have high serotonin levels, whereas dominant individuals of more cooperative species such as bonobos have low serotonin levels.

Issa et al. looked at social status in crayfish.  Crayfish actually form long-lasting and complex dominance hierarchies where subordinate animals give way to dominants in contests over resources.  Issa et al. took socially isolated animals and let them interact for thirty minutes a day, even though dominance was usually established within the first fifteen minutes.  They then examined the response to these individuals to a surprise touch to the back leg.  Dominant individuals always immediately turned toward the tap, presumably because they were prepared to be aggressive toward some threat.  Submissive individuals, on the other hand, always showed one of two behaviors: they either pushed backwards and then lowered their posture, or they flexed their abdomen, dropped their posture, and then moved backward.  When they recorded from a (specific) neuron that releases serotonin, they found the same kind of stereotyped response from the dominant individuals’ neurons, and the same kind of symmetric response from the subordinates’.  The authors also have a nice model suggesting that the neural circuit itself might be reconfiguring itself by modifying thresholds for firing of excitatory and inhibitory neurons.  It’s a simple result that looks true, though in the field of circuit neuroscience, the easy answer is almost never the right one…

This means that the dominant and subordinate individuals not only have different levels of serotonin, but that their neural circuitry is fundamentally different.  The authors interpret this to mean that a change in status indicates a persistent change is enacted, perhaps by modifying the amount or type of receptors.  The fact that dominance is usually established within fifteen minutes leads one to think that perhaps there is some other underlying difference; however, isolated individuals that weren’t exposed to this dominant-subordinate training acted in roughly the same manner as dominant individuals, with similar neural responses.

For the crayfish, there is probably a trade-off: dominant individuals get more resources, but must also be prepared to fight, perhaps making them more likely to be consumed by predators.  The lessons for humans is probably more complex.  Serotonin is not just linked to social status, but also depression, so it would not be surprising if low social status can literally make us ill.

Reference

Issa, F., Drummond, J., Cattaert, D., & Edwards, D. (2012). Neural Circuit Reconfiguration by Social Status Journal of Neuroscience, 32 (16), 5638-5645 DOI: 10.1523/JNEUROSCI.5668-11.2012

Photo from