Function of Pupillary Dilation in Sympathetic Arousal

A commonly cited response to sympathetic arousal is pupillary dilation: the eye’s pupils open up. Italian women of the Renaissance thought that by applying atropine (belladonna, literally beautiful lady) to their eyes, causing pupillary dilation, they could enhance their beauty, and modern studies by psychologists have shown that they were right: photographs of people with large pupils are judged to be more attractive than photos with small pupils (presumably because when you look at a person with large pupils you are looking at someone who is aroused while looking back at you). Psychologists have attempted to use pupillometry as a measure of emotion.

Dilated pupil (from Nutschig at the English language Wikipedia)

Constricted pupil (public domain)

What is almost always glossed over is the function served by dilated pupils in times of high emotional arousal.  One often sees statements such as “The pupils dilate, letting in more light so you can see better,” but this has never made much sense to me; why would making the scene brighter than normal make vision better?

I think I know what those dilated pupils are doing for us. At this point consider it a strong hunch, guided by years of thinking about both the adaptive value of behavior and about photography.  In photography, the term “depth-of-field” (DoF) refers to the region from the closest to the farthest part of the photo that appears to be in focus.  A large DoF means that objects near and far are in focus; landscape photographers typically want large DoF.  A small DoF means only a narrow region at a particular distance from the camera appears in focus and the rest is blurry; portrait photographers usually want small DoF resulting in a blurry background that does not distract from the model’s face. Enlarging the aperture of the lens decreases the depth-of-field, and reducing the aperture increases the depth-of-field.

Depth of field illustration. larger aperture on the left, small aperture on the right. (photo by Alex1ruff, licensed under the Creative Commons Attribution-Share Alike 4.0 International license)

Why should sympathetic arousal be associated with a large-aperture pupil and thus a small DoF? Wouldn’t you want a large DoF, with as much as possible in the scene in clear focus? I argue that no, in times of “fight or flight” a small DoF is beneficial. Accurate movement is essential, and judging the distance of objects (the branch to which you must jump to escape; the neck of the predator you have to bite to disable it) is critical. One unconscious cue that we use to judge distance is the extent that the lens must be curved or straightened to bring an object into focus — a process called accommodation. With a large DoF (small aperture pupil) there is a lot of leeway or “slop” in how accurately the lens must be curved. As the DoF gets smaller (with a large aperture pupil) lens curvature is more critical to focus as their is less slop. The result of that dilated pupil with its small DoF is more precision in the information that is provided by the lens accommodation; the brain therefore more accurately interprets the distance of the object being viewed. Behavior is then more accurate. Our arboreal primate ancestor escaping from the proto-leopard gauges the distance to the neighboring branch correctly because his pupils were dilated and he survives; his friend lacking the pupillary dilation misses the branch, and his genes are gone from the gene pool. 

To examine human DoF for constricted and dilated pupils, I used a web-based DoF simulator designed for photographers, applying photographic parameters to the human eye.  A web search suggested that a commonly-suggested value for the focal length of the human eye is 22 mm (the DoF simulator needs the entered focal length to be stated as if the camera in use is a 35-mm film camera, with film size of 24 x 36 mm; at least one online site suggests that in these terms the human eye’s focal length should be entered as 32 mm).  Another site suggests that the aperture of the human eye, expressed in the traditional f-stop terminology of photography, ranges from f/8.3 when constricted to f/2.1 when dilated. 

Taken from the online tool DOF Simulator, the grey regions illustrate the distance from the human eye that will appear in focus (depth of field) when an object is 3 m away. On the left – the DoF when the pupil is constricted; on the right – the DoF when the pupil is dilated.

The images (clipped from my session with the online DoF simulator) show the DoF when the pupil is constricted compared to the DoF when the pupil is dilated. Here the model is 3 m from the camera, a reasonable distance for that escape branch. With a constricted pupil (left), the area from ~0.8 m in front of that branch to ~1.6 m beyond the branch appears in sharp focus, a distance of 2.4 m. With a dilated pupil (right), the clear focus ranges from ~0.25 m in front to ~0.25 m beyond the branch, only 0.5 m. Clearly the dilated pupils provide better information about exactly how far to leap.

Please recognize that the values used in the calculations that created these estimates were at best rough approximations of the parameters of the human eye. However, whatever values are used, the dilated pupil will produce a DoF that is much narrower than that afforded by the constricted pupil, so the dilated pupil will always provide better information about the accurate distance to the object. 

[If someone wants to take this idea and develop it more fully or more rigorously please do so – just acknowledge my contribution, please.]

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Thoughts on the Fate of Liberal Arts Colleges

Green Mountain College

Green Mountain College (VT) announced recently that it will close at the end of this year. Other small liberal arts colleges (LACs) face severe financial issues that have led to closing (Newbury College, Atlantic Union College, Mount Ida College) or fear of imminent closure (Hampshire College, Bennett College). Antioch College closed its main campus in Ohio a few years ago, and is now trying to rise phoenix-like from its ashes. 

I recall in the early 2000s seeing a TV segment about Upsala College, a small liberal arts college in East Orange, NJ, that had closed in 1995. The TV show featured an architectural salvage crew entering the now-overgrown buildings to reclaim whatever might be useful. My thought at the time was “Wow! How could that happen!? Glad it wouldn’t happen to me!”
 
Now it is clear that Upsala’s fate will be the fate of many other good schools. Why is this happening? All of these colleges have struggled with attracting students, whose tuition dollars are essential given relatively low endowments. Students chose not to attend these schools because of the perception that they could get the same education for a lower price elsewhere, typically at large state universities. This is a misperception that liberal arts colleges must overcome in order to survive
 
Course names and major names might be the same, but that’s where the similarities between the LACs and the state universities end. LACs send proportionately far more students to graduate programs than do the large universities; students come out of the small schools prepared for PhD programs because they have often done things that graduate students do: overseen research projects, presented papers at conferences, published articles. LAC graduates are preferred by businesses because they are better trained to think and to communicate.
 
High school students can’t assess the differences,and their parents are typically also not prepared to do so. A prospective student interested in, say, Psychology, will see a Psych program at Albion College and a Psych program at Big State, and on paper the programs look similar. Big State probably offers more courses, has a larger faculty, and publishes more papers, so Big State must be the better place. Look a bit deeper and the differences become clear: Big State has classes of 100 students or more, taught by graduate students, and those many research papers represent work done by graduate students under the mentorship of professors. Small classes at Albion are taught by professors, who oversee the research of undergraduates (much like the prospective student), mentoring it through to presentation or publication.
 
The prospective student who opts for the LAC will graduate in four years with a level of preparation that surpasses Big State’s graduates (who might have taken five or more years to graduate). Liberal arts colleges must figure out how to convey this truth to the prospective student and her parents if they hope to survive. I don’t know how to do this, nor, sadly, do most of the rest of us at liberal arts colleges. Until we figure this out the distinctly American liberal arts education is threatened, and with it one of the foundations of our country’s greatness.
 
News of the closings of these small schools saddens me, but it also reduces any potential regrets about my approaching retirement; I won’t have to spend much time worrying about the future of my job security at my very good small liberal arts college.
 
=========================
A few disclaimers:
 
Of course there are students who do very well at Big State U. My two older kids attended Big States and are quite successful in their careers. Finding and taking advantage of the best opportunities is easier at the LAC.
 
The perceived price difference between the LACs and Big State is smaller than it seems. LACs offer scholarships and financial aid that can significantly reduce the cost. The likelihood of needing more than four years to finish at Big State (due to difficulty in getting the required courses, or finding that the general education requirements for a changed major differ from those of the old major, requiring more classes, or maybe just due to poor advising) adds to the cost; LACs almost always get students out in four years.
 
This piece clearly reflects the views of the author, informed by many years of teaching at a liberal arts college, and experience at a few Big States.
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Musings on Photography at Concerts

I have attended many events where the venue bars cameras. Typically this means “good” cameras, often but not always defined as cameras with interchangeable lenses. Most recently I saw Jesse Cook at the Kalamazoo State Theatre—it was a great show by fabulously talented musicians—and I watched as countless cell phones were used to take photos and to record audio and video. I had smuggled in my “good” camera, an Olympus OM-D E-M10, with a 45mm f/1.8 lens – a fast and somewhat short telephoto lens. Patrons were searched as the entered the venue; we had to have our coats open and security patted us down – probably checking for alcohol or weapons. My camera, in the pocket of the coat and thus held away from me as I opened the coat for inspection, was undetected.

Jesse Cook at the Kalamazoo State Theatre

My seat at the front of the Mezzanine (lower balcony) gave me a great view of the stage, and after the first song I got my camera out and took a few photos, being sure to hold this threatening object in my lap when not in use so that the watchful eyes of the security guards wouldn’t see it.  At a prior concert at this venue I had seen security approach people with “good” cameras and ask them to put them away under threat of expulsion (of course while cell phones were in use all around them); at that concert I had used a longer lens and got some great shots.  

So, should cameras be allowed or not? My view, not surprisingly, is that if photography is permitted, then the venue should not care what equipment is used, within limits. Equipment that could interfere with the enjoyment of the event by those around you should of course not be used – no flash, no tripods that might impede safe egress, no long lenses poking over the shoulder of the patron in the seat in front of you.  Once photography is allowed and phones are recording photos and video, cameras should not be banned.

Upon arriving home, I reviewed my shots and posted a few good ones to a Facebook album. By the next morning, the Kalamazoo State Theatre had “liked” my album. Here’s the reply that I posted to them:

Great show – glad you brought Jesse Cook and his other talented musicians to town! And I’m glad that you liked the photo album that I shared. I wish I hadn’t had to smuggle in my camera to take a few photos, especially considering that photos were allowed and there were many phones recording not only still photos but audio and video as well. Guess I need to add a phone app to my camera, then there would be no issue 🙂. Wish you would reconsider your camera policy.

No reply from them yet – I’ll post it here if they respond.

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Quadrantids

A time-lapse video of the northeast sky from about 12:30 – 2:00 on January 4, 2019. Hoping to capture a few of the Quadrantid meteors – I think I can see three in this video.   

 Here’s the link if you want to download the video:  

http://campus.albion.edu/wjwilson/files/2019/01/Quadrantids1419.mp4

Keep looking up!

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Another SfN in the Books.

I just returned from the Society for Neuroscience 2018 meeting in San Diego. Attendance was down – I heard that only 23,000 attended (rather than the usual 29 – 30,000), but I have not confirmed this. Good talks, good science, but not all is perfect.

Foreign attendance was down, at least in part due to Trump’s travel restrictions. Not only does he fail to accept science, he stands in the way of scientific progress.

Eight current Albion students attended with me. We met with Nick Singletary, a grad student at Columbia University, to get his perspective on life in grad school, and with Debbie Bangasser (Temple U.) to get the perspective of a professor who oversees grad students. Both meetings were useful. 

I hosted a get-together for Albion’s neuroscience alums; a good time was had by all, but sadly only five could attend. At least two others were at the meeting; in the past we’ve had more than 10 alums at the event.

And a highlight for me is getting to see Alice Powers (Stonybrook U.), my first psychology prof ever. She continues to examine learning in turtles, this year demonstrating that neurogenesis in what passes for a turtle’s hippocampus plays a role in learning. By the time I graduated from college in 1977 she was my friend, and I am glad I can call her a friend this many years later. 

Albion Neuro Alums and current students. From left: Amanda Blaker, me, Amanda (Tilot) Komoru, Emily Stephens, Megan Anderson Brooks, Irene Corona, Nicole (Ferrara) Clark, Haley McQuown, Brandon Gary.

Other highlights for me:

  • Seeing many other friends whom I’ve known for decades in some cases, a few years in others. 
  • Meeting a few new friends with shared interests (Alexxai), or just through odd happenstance (Heike).
  • Having the Med Associates representative remember me and my work with earthworms, and want to pick my brain about it.
  • Reeling as always at the growth of FUN (Faculty for Undergraduate Neuroscience), which rose from its humble beginnings in 1991 to become a powerful force in undergraduate education, hosting a poster session with 172 posters presented by undergrads, and giving away thousands of dollars in travel awards.
  • Checking in with my friends Tim and Greg at Backyard Brains to see what new and innovative projects they’ve developed.
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Chronistic Serendipity

Much is made of the importance of serendipity to scientific discovery. Here are some well-known examples:

  • Roentgen’s discovery of x-rays.

    Antenna used by Penzias & Wilson

  • Becquerel’s discovery of radioactivity.
  • Hoffmann’s accidental first trip on LSD.
  • Fleming’s discovery of penicillin.
  • Bell’s discovery of pulsars.
  • Penzias and Wilson’s discovery of cosmic background radiation.

All of these “accidental” findings resulted from trained minds being capable of recognizing something unusual and unexpected as worthy of further study. I argue that all of these breakthroughs would have occurred at some point–these folks simply happened to notice them. There was nothing special about the time when the discovery occurred, except that the technology had been developed that allowed it to happen. Once that technology existed, the discovery was inevitable.

However, I suggest that an important discovery in neuroscience–so important that it led to a Nobel Prize–occurred in large measure because of the time when the research was done. The technology that allowed it did not exist a few decades earlier, and a few decades later the technology had changed to the point that the discovery would not have occurred. I’m talking about Hubel and Wiesel’s discovery of the receptive fields of visual cells in the brain’s cortex.

These neuroscientists found that the simplest visual stimulus that activates cells in our cortex is a line, in a particular place and oriented a particular way. Even Hubel has admitted that the discovery was accidental. Cells in the retina and thalamus were known to respond to spots of light (or dark), so Hubel and Wiesel were shining all sorts of spots in front of their anesthetized cats in a failing effort to make the cortical cells fire. 

The scientists used spots painted on glass slides, which were moved around in a projector and displayed on a projection screen in front of the cat. The cortical cells did not respond to the spots, but when the edge of the glass slide moved through the projector, casting a faint line on the screen, a cell responded.  Hubel and Wiesel realized that cortical cells respond not to dots or spots, but to lines, as a result of this accidental finding.

So what was special about this point in time, the 1950s, that allowed this discovery? It is almost certain that, had they done this work in the 1980s or later, they would not have used a glass slide in a projector. Instead, it is likely that they would have used a computer to generate the spots and move them around on a screen in front of the cat. What’s missing in the scenario? The edge of the glass slide. No glass slide, no edge, no line presented to the cat. Their serendipitous finding that cells respond to lines would not have occurred.

The discovery of the nature of the receptive fields of visual cortical neurons rested on the scientists doing the work not after a particular point in time, but in a particular time window. This is an example of chronistic serendipity. I would love to hear examples of others if someone can identify any. Post them as comments below.

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Amusing Facebook Juxtapositions

Facebook uses an algorithm to determine what to display on your newsfeed. It is proprietary, and designed to keep you on the page so that you consume the ads that are thrown at you. Occasionally this algorithm places items next to each other that, while not amusing in their own right, become amusing because of their proximity. Over the past several years I have collected examples of such juxtapositions – many appear here. Please note that an “amusing” juxtaposition does not necessarily mean that either item by itself is “funny” — it simply means that in my opinion their adjacency made me think or smile. 




















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Great Meeting!

The Pavlovian Society held its annual meeting in Iowa City, Oct 4-6, 2018. Pres. John Freeman put together an excellent program–fabulous talks spanning the breadth of learning. Here are a few photos:

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Thoughts on Grad School Admission

[10/10/2018 – It’s been a while – worth moving to the top of the page.]

[10/20/2012 – I now realize that the students who most need to read this are unlikely to do so because it won’t be on the test.]

Occasionally interactions with students remind me of advice that should be given to everyone who hopes to go to graduate or professional school.  Maybe posting my thoughts here will help someone.

  1. Admission to graduate/medical/law/business/etc school is not a right; nobody is guaranteed admission.
  2. Good grades do not get you admitted.  In fact, other than getting the grad/etc program to look at your application, grades are unimportant.
  3. Good test scores (GRE, MCAT, LSAT…) are also largely unimportant other than getting you a second look.
  4. Re-read points 2 & 3 above.  Go ahead; I’ll wait…
  5. OK – here’s the story on good grades and test scores: if you don’t have them you won’t be considered – if you do have them you will be considered, but not on the basis of the grades or test scores.
  6. You have to provide the admissions committee with something that differentiates you from the other applicants with good grades and test scores.  They will learn why they should admit you via the letters that are written on your behalf.
  7. They will also learn from your letters why they should stop considering you.
  8. Letters are critical.

Consider this in your interactions with professors.  You will need to ask some small number of professors for letters – it would be best if these people thought highly of you.  When I write a letter for a student aiming for grad school, I consider whether this is a student I am comfortable sending to work with a friend.  If the answer is “no” then I cannot write a strong letter.  When I write a letter for a student aiming for med school, I consider whether this is someone I would like to find looking down at me when I regain consciousness in the emergency room.  If the answer is “no” then I cannot write a strong letter.

My letter will address your academic abilities, of course, but it will also address aspects of your character that are not apparent in your transcript:

  • Are you responsible?
  • Are you thoughtful?
  • Are you pleasant?
  • Are you polite?
  • Are you interested in learning or just in getting grades?

These are the things that will matter in grad school.  You have to be able to play nicely with others in order to succeed in science; a 4.o GPA is no assurance of this.  If you want me to write a strong letter for you then do not do any of these things:

  • Make an appointment with me then fail to show up (OK – I understand that stuff happens, so in the event of something unavoidable at least act as if you realize that I was inconvenienced).
  • “Grub” for grades.  Yes – it is certainly fine to ask for clarification if you don’t understand why you missed points on something, but it is not fine to argue that you deserve a point simply because a word in your answer matches a word in a related paragraph in the text.  Meaning derives from the combination of words, not from one word.  And think about it this way: is the additional point that you might get worth alienating the person whom you will ask to write a letter for you?
  • Fail to be polite.  A simple “please” or “thank you” goes a long way.  Your profs are here to help you, of course, and we like to do it.  However, our time is valuable, and meeting you outside of class time or office hours takes us away from other things that we need to do.  Acknowledge this.
  • Turn in papers or assignments late.  You will not get leniency in this regard in the real world: if you miss a grant application deadline, or the deadline for submission of your work to a professional meeting, you have missed it, and will simply have to wait until next time.
  • Be a jerk (’nuff said).

To end on a positive note, let me point out behaviors or characteristics that will lead to a strong positive letter:

  • Express interest and curiosity in the world.
  • Strive for understanding rather than for grades.
  • Read.
  • Treat people with respect.

If you do these things, you will be maximizing the chances that you will gain admission to grad school.

[You might also want to read this or oher thoughts on success organized here – similar but with slightly different emphasis.]

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“Engram” – When I’m wrong, I admit it.

For as long as I can remember, when I have introduced students to the concept of the “engram,” or “memory-trace”–the change in the nervous system that encodes a memory–I have told them that the word was coined by Karl Lashley. Lashley spent a career, well over 30 years, searching for the engram, an effort described in one of his later papers, The Search for the Engram (1950), in which he famously concluded (with tongue firmly implanted in cheek) that “learning just is not possible.” Basically, he was unable to find the engram.

I learned at the recent meeting of the Pavlovian Society that I have been wrong for all these years. The term “engram” was coined by Richard Semon, an evolutionary biologist and physiologist. His work is little known, as are most of the other memory-relates words that he coined, but “engram” is still going strong.

Apologies to the many students I have misled.

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