The Rise and Fall of Neurotransmitters
There are dozens of neurotransmitters in the human brain. How do neuroscientists decide which transmitters are most important? Are there trends and fashions in neuroscience, such that some transmitters rise and fall in popularity?
I searched PubMed for nine different neurotransmitters, and downloaded the ‘Results by Year’ data to track the number of peer-reviewed papers published each year from 1960 to 2014. The results are very interesting:
Here are some of my observations in no particular order:
The stagnation of serotonin (red): after growing steadily from 1960 to 2005, the number of papers about serotonin has flat-lined. This is possibly a reflection of the stagnation of research into selective serotonin re-uptake inhibitor (SSRI) antidepressants which likewise plateaued around 2005(although it has started to grow again lately, unlike serotonin). This, in turn, may be related to the fact that most of the SSRI drugs went off-patent around this period. However, this can’t explain why GABA (purple) andendocannabinoids (black) stagnated over the same period. Hmm.
Dopamine (blue) is on the march: it’s the only transmitter that’s been steadily growing research since 1960.
The decline of noradrenaline/norepinephine (green): it was once the hottest transmitter, but something happened in the mid 1980s, and noradrenaline’s research output flat-lined, and then began to shrink. What went wrong? Maybe it was related to…
The rise and fall of substance p (orange) and the endorphins (pale blue): these two neuropeptides were discovered to be neurotransmitters in the late 1970s. Research on them grew rapidly but it didn’t last – by the early 1990s, they had each entered a decline from which they’ve never recovered. At one point the endorphins were more popular than GABA, but by 2014, 28 times more papers were published about GABA than about endorphins.
Note: This post is an update of one of my first ever posts, from 2008.
Meta-analyses are systematic syntheses of scientific evidence, most commonly randomized controlled clinical trials. A meta-analysis combines the results of multiple studies and can lead to new insights and more reliable results.
However, according to Italian surgeon Giovanni Tebala writing in Medical Hypotheses, meta-analyses are becoming too popular, and are in danger of taking over the medical literature.
Another day, another alarming brain-related story hits the news:
A Close Look at the Connectivity of a Single Brain
In a new paper just out in Neuron, researchers Timothy Laumann and colleagues present an in-depth look at a single human brain.
Social Priming: Time for A Definitive Test?
The scientific controversy over social priming – the (claimed) ability of incidental exposure to stimuli to ‘prime’ or evoke complex behaviors – has been rumbling for the past few years. Will it ever end?
In this post I’ll propose one way in which I think it could be resolved.
“Right Wing Brain Surgeons” And The NFL
This week (via Retraction Watch) we learned about the case of Joseph Maroon. Earlier this year Maroon and colleagues published a paper arguing that the much-discussed issue of chronic traumatic encephalopathy (CTE) may not be a widespread problem in contact sports such as American football.
However, it turns out that Maroon did not fully declare his conflicts of interest, which include links to the NFL and also World Wrestling Entertainment (WWE).
Maroon, who amongst other things is lead neurosurgeon for the Pittsburgh Steelers football team, issued a Correction acknowledging his interests in this area. The question of which athletes are at risk of CTE has potential legal and financial implications for sports organisations such as NFL and WWE.
Now this story got my attention because Maroon is also linked to Surgical Neurology International (SNI), an academic journal that I blogged about earlier this year: Right-Wing Brain Surgeons.
“Is Your Brain Really Necessary?”, Revisited
According to British biochemist Donald R. Forsdyke in a new paper inBiological Theory, the existence of people who seem to be missing most of their brain tissue calls into question some of the “cherished assumptions” of neuroscience.
I’m not so sure.
Cognition And Perception Are Separate After All?
Can our beliefs, motivations and emotions influence our visual perception? Are cognition and perception ultimately inseparable?
Wind Farms, Infrasound And The Brain
An alarming news story appeared on Monday in the Daily Telegraph:
Wind turbines may trigger danger response in brainThe low frequency noises from turbine blades can be picked up and can trigger a part of the brain linked to emotions, scientists have found…Brain scans show that even infrasound as low as 8 Hz – a whole octave below the traditional cut off point for human hearing – is still being picked up by the primary auditory cortex, the part of the brain which translates sounds into meaning. And a separate part of the brain, linked to emotions, also lit up.
What’s curious about this is that the research in question wasn’t about wind turbines, and has not been published anywhere yet, as far as I can tell.
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