Dopamine is often referred to as the "reward" neurotransmitter, a chemical signal released to rewarding stimuli such as drugs of abuse. Its effect on motivation and reward is, however, more nuanced.

Prefrontal Cortical Dopamine and Cognition
In fact, dopamine signaling in an area of the brain known as the prefrontal cortex (PFC) is critical for a variety of cognitive functions, including attention and processes such as working memory. Interestingly, dopamine's function on cognition has proposed to be non-linear (inverted U shaped) with some optimal intermediate level of dopamine associated with better cognitive performance. My own work in collaboration with Charlotte Boettiger and Amanda Elton has used the inverted-U model of PFC dopamine's effect on cognition to explain differences in working memory and choice behavior seen in healthy adults. We have also shown evidence of U-shaped patterns in resting and task-related brain function.

PFC dopamine is thought to vary based on genetics and sex. Thus, biological factors affect where individuals fall on the inverted-U. Additionally, stress is known to boost PFC dopamine (and other neurotransmitters) and an individual's biologically-based PFC dopamine levels may explain why some people perform better under stress (i.e., their basal PFC dopamine is sub-optimal but it boosted "up" the curve to optimal range with stress) then others (whose PFC dopamine levels may start out more in the optimal range but are then pushed into a supra-optimal level "down" the inverted-U curve). Genetic variation in one key PFC dopamine regulatory gene in particular (COMT) has led to the use of the term "warriors" and "worriers" to explain the function this natural variation in PFC dopamine plays in human behavior.

Dopamine Signaling Declines with Age
Dopaminergic signaling declines with age. A 2017 meta analysis led by Teresa Karrer has demonstrated declines in both the receptors that are the key target of dopamine signaling as well as the dopamine transporters important in the regulation of this signaling.
This decline has effects on a variety of decision making processes. It also has implications for the inverted-U model as natural declines of PFC dopamine with age would be expected to shift where individuals fall on the U-shaped curve.

Dopamine's effects on cognition in particular and the fact that cognitive processes also decline with age (also see) that has lead to the correlative triad hypothesis. This hypothesis proposes that the decline of brain dopamine signaling explains much of the cognitive decline in aging.

You can explore these data showing variations in age-related decline of brain dopamine via an online application created by my colleague, Kendra Seaman, here.

Aging, Dopamine, and Decision Making
While our own data does not unequivocally support the correlative triad hypothesis of dopamine, aging, and cognition, this does not mean dopamine changes with age don't impact some aspects of human behavior. Work from the Samanez-Larking group and others has shown older adults are more likely to choose skewed gambles than younger adults, are less sensitive to monetary losses, and decrease their selection of risky monetary choices with age. See two excellent review articles on some of this aging & neuroeconomics literature here and here.
Our group, in work led by Kendra Seaman, has also found evidence that different types of commodities (social interaction and health) may be more valuable to older adults immediately and with certainty than money.
Interestingly, the brain regions responsible for assigning value to potential rewards are consistently engaged across adulthood. Thus, older and younger adults are using similar brain mechanisms to assign value to rewards. It is possible, though, that changes in dopamine signaling in these key reward valuation brain areas (ventromedial PFC, ventral striatum) influences to amount of value assigned to rewards as we age.

Summary & Future Directions
An increasingly aging human population makes it critical to understand how decision making processes may differ between younger and older adults. Natural, age-related declines in dopamine probably play a role in reward and choice behavior differences between young and older adults. Understanding the differences between choice behavior with aging will allow more effective interventions to be developed to assist older adults in their financial and healthcare choices (see also).
More work is needed to determine if particular approaches (from pharmacology to exercise) can be taken to optimize PFC dopamine levels and/or prevent age-related declines in dopamine signaling. 

Naming my first Reflections blog post "Start Here" may seem a bit on the nose. But, the key to taking on any big life decision is to start tackling the problem. 

I am currently reading the book Designing Your Life: How to Build a Well-Lived, Joyful Life, by Bill Burnett & Dave Evans (see an excellent New York Times review here).
It is a really great read for anyone trying to improve some aspect of their lives: finding the right job, prioritizing your love/family life, doing something that makes a difference in the world, etc...

The book starts out emphasizing the need to Start Where You Are. This centers on the need for a person to figure out where they currently are in their lives and what problem(s) they are trying to solve. A key point here is that you need to focus on the right, actionable problems in your life.
You should avoid tackling what the book terms "gravity problems" or problems that we effectively have no chance of changing because they are systemic (like gravity). This doesn't mean you should tackle a difficult problem but you should address it in an actionable way where your actions have the ability to affect change.
Another key step to moving forward with your problem is addressing "anchor problems". Anchor problems often keep us stuck because we have become anchored to only one ideal solution. This is problematic because that solution may not be obtainable (think, achieving a particular job at a particular company - what are the odds of you achieving this?). Ultimately, to address these problems, you need to reframe them or approach them from a new perspective. Maybe you don't need to land that particular job but you want to do a particular type of work and there are other avenues you could pursue to find a career that is a good fit for you. Be flexible and don't get stuck on only one solution.  

The book defines "life" broadly as health, work, play, and love. You should start out assessing how your life is going in each of these areas (how full is your life in each area, what could be improved) and whether you want to tackle a particular problem in one or more of them. 

You may find work fulfilling but have no time for play, love, and health. So, that might mean you need to address how much time you spend on work and whether you might want to do something different that provides you the free time to spend on the other important aspects of your life. What is a good life and how "full" these four areas of work, health, play, and love need to be to achieve the life you want will vary considerably from person to person. 
Once again we come back to starting where you are. What one person might deem a life problem worth solving another might be perfectly OK with. One's "good life" is immensely personal. But you need to understand what that good life looks like for you. 
As this blog and my interests focus on career exploration, let's turn to what a "good career" looks like for you. Where do you start?

Other great resources include InterSECT Job Simulations and content from UCSF's Office of Career & Professional Development (see also the MIND resources from UCSF).

A key concept from Designing Your Life is to "prototype" your next move...ie, try out a new career before you make the leap. A useful way to begin to learn more about a career and start to measure its fit for you is via informational interviews. Another great way to prototype is to freelance or volunteer, performing the task "on the side" to see how you like it and begin building a portfolio of experience that will help to land a job in that space, should you want to pursue it. Some work is easier to freelance or volunteer for than others. Writing is in high demand from many organizations (think, your professional association and their newsletter). You can also get experience with working with and presenting data (and market yourself as a Data Scientist) via Kaggle and keep your work available on GitHub.

A final point to keep in mind as you explore your career options, prototype your next move, and think about your ideal life: there is not one "optimal" life for you. The following quote from Designing your Life sums up this point: "A common mistake that people make, is to assume that there’s only one right solution or optimal version of your life, and that if you choose wrong, you’ve blown it.That’s completely absurd," Mr. Evans said, “There are lots of you. There are lots of right answers.”
I think this point is especially powerful as people grapple with the fear of making the "wrong" choices in life. It is freeing to know that one choice (or series of choices) doesn't have to define your whole life. The book pushes the idea of creating multiple "Odyssey Plans" for your life. Map out the next five years of your life in radically different ways: 1) pursue certificate in X, 2) intern at company Y, 3) transition to position at company Y OR 1) continue working in area Z while also working on improving writing skills by volunteering with association W, 2) do freelance writing for company D while still working in area Z, 3) move to a full-time writing career OR 1) continue working at company T, 2) take night classes in area U, 3) get promoted to new role at company T, etc.
This activity reinforces the idea that there are multiple viable options available to you in your career and life. I could do A, B, or C and be happy and fulfilled. Having this mindset means that if things don't work out with option A (you realize that career/life choice wasn't the right fit for you), you know you can pivot to option B or C and be equally (or maybe more) happy.

Remember that life is a journey, and there is no one way to undertake it nor one path to follow. With some deep reflection on your skills, values, and interests, you can start researching and planning the multiple paths you could take to achieve fulfillment in your life. 

Find more resources on the Designing Your Life website. ​

As some may know, I have written on postdoc-related topics for The POSTDOCket, the online newsletter for the National Postdoctoral Association, since May 2017.

Links to past POSTDOCket pieces:
Postdoc Industry Consultants Program at Medical College of Wisconsin
Services and Resources Available at Postdoctoral Offices of Varying Sizes
Using Your Total Research Experiences to Make You Business-Ready
Preparing for a Faculty Career at a Predominantly Undergrad Institution
Vanderbilt PDA & Office for Postdoctoral Affairs Broaden Reach with Organizational Transition
Thirty-Plus Years Enhancing the Postdoc Experience: Sam Castañeda
Mentoring for Mutual Benefit: Leanne Redman
Accelerate to Industry: A new Approach to Academic & Private Industry Collaboration to Improve Career Readiness of Graduate Students and Postdocs

Since October 2018, I have been a contributing blogger for NIH BEST, writing about career exploration and professional development, from my perspective.

I am now launching my own blog to continue to reflect on topics I am passionate about. These are varied and might include:

• Neuroscience-related topics, especially those focused on behavioral economics
• Personalized Medicine, especially how individual differences in biology (genetics) may affect treatment for a variety of diseases
• Career Exploration tips for graduate students and postdocs
• Professional Development resources and reflections for graduate students and postdocs
• Thoughts on the Evolving Scientific Workforce and how we can better prepare graduate students and postdocs for 21st-Century careers, inside and outside academia
• And more...

Example Personalized Medicine topics:
Using Data Science & Artificial Intelligence to Improve Healthcare
The NIH All of Us Research Initiative: A New Standard in Participant Engagement & Partnership

I hope my posts serve as useful resources for trainees, those who work with and advise them, as well as the general public interested in science, medicine, and the scientific workforce.
Stay tuned for more content!