One of the most popular posts of all time here at Neuroethics at the Core is entitled The Science of Love by Sara Parke . The post deals with the discomfort that Sara felt as she began to explore the notion that love is mediated by the brain, prompted by work she did in a research lab as an undergraduate at Stanford. Even without a complete understanding of the underlying neurobiology, once one begins to ponder how love might work, most people fall into a well of despair as they realize that love, a most cherished experience, is based upon the firing of neurons and the release of chemicals. Continue reading
Each year when the Society for Neuroscience Meeting rolls around, all of the major journals devote extra space to neuroscience, publishing hot articles to attract the attention of the 30,000 plus attendees at the conference. This year is no exception, and one of the most important articles came out this past week in Nature with the heady title “Intracellular dynamics of hippocampal place cells during virtual navigation“. The paper, by Chris Harvey, Forrest Collman, Daniel Dombeck & Dave Tank is a tour de force investigation which combines new technology with insightful experimental manipulations and shows, according to an accompanying commentary by Doug Nitz, that “it is not impossible to examine brain correlates of higher cognitive processes and at the same time identify their underlying causes at the cellular level”.
The detailed results are probably too technically specific for most people in the field of neuroethics, but this study highlights some of the reasons that hard-core neuroscientists view fMRI with disdain. Given the prominence that imaging the human brain has come to play in neuroethical discourse, I encourage readers to take a few moments to at least try to appreciate what the issues might be.
First, let’s take a look at what Dave Tank’s group at Princeton have done. For over 35 years, neuroscientists have known that the firing rate of a subset of hippocampal pyramidal cells (the so-called place cells) change in predictable fashion as the animals navigate through a spatial environment. In particular, the firing rate of a place cell reflects both the animal’s present spatial position and the path the animal has taken to reach that position. Think about that for a second: the output of a single neuron reflects a highly nuanced and information rich algorithm. But it does not stop there. When multiple place cells are recorded at the same time, they exhibit a phenomenon called phase precession. Nitz’ commentary sums it up nicely:
The firing order for a set of hippocampal place cells with partially overlapping place fields is found to match the animal’s physical trajectory corresponding to those fields. Phase precession stands as perhaps the most robust example of temporal coding of information in the mammalian brain.
Addiction is a brain disease. This is undeniably a bold and controversial statement and one which usually elicits varied reactions ranging from denial and skepticism to wholehearted agreement. The lack of consensus means that when Canada’s “neuroscientist in chief” is defending this view, people to sit up and pay close attention. During his recent talk as part of our “Neuroethics of Addiction” workshop, Dr. Anthony Phillips, the newly appointed scientific director of the Canadian Institutes for Health Research’s (CIHR) Institute for Neuroscience, Mental Health and Addiction (INMHA), explored how the brain networks and chemistry change as a result of repeated drug abuse. Dr. Phillips explained that people who abuse drugs are in the process of changing their brain chemistry (mainly through fluctuations in dopamine levels), which has semi permanent effects on decision-making processes.
From the data Dr. Phillips presented, it is clear that the brain plays a role in addiction. The ‘reward network’ and dopamine-glutamate system function pathologically such that basic needs such as food are ignored and seeking a particular drug is prioritized. But is addiction only a brain disease? I think it would be shortsighted to conceptualize the condition in that way. In addition to brain activity, socioeconomic, psychological and political factors, among others contribute to onset of the addictive behavior as well as to the disease course itself. This is not to say that investigating the neuroscience of addiction and addictive behavior is not a worthy endeavor. After all, Dr. Phillips expressed hope that research on the neuroplasticity (the brain’s ability to change itself) may have important implications for treatment of addiction. The contributions that science can make towards understanding and managing addiction are undoubtedly valuable. It is important, however, to acknowledge the complexity of the condition and avoid reductionist perspectives on addiction.