The Brain's "Reward" Centre Also Responds to Fear

One of my pet hates in neuroscience is the propensity to attribute highly specialised functions to currently identified brain regions. If only it were that simple. This study, remarkable in its detailed analysis, again reminds us that the brain is not only a wonderful thing but an incredibly wonderfully complex thing.

It has long been known and studied that the ventral tegmental area(VTA), a rather small nucleus in the midbrain, is very much involved in "reward" processes. Illicit drug use very often involves the VTA dopamine neurons becoming rather active. Even marijuana, who some claim is not addictive, will involve activation of these neurons.  Note though that the abstract refers to a specific location in the VTA - the posterior region. These nuances in how these "cerebral modules" respond needs to be kept in mind. For example, we often read that the amygdala is a "fear center". For example, consider this recent news release which appears counter intuitive. In that news release, the so-called "fear centre" - amygdala appears to play a role in reducing anxiety. Note though that is very misleading to refer to a "fear centre". Neurons don't experience fear, we do! As the linked Wiki article states, the amygdala can be subdivided into many regions. For an excellent introduction to the amygdala, try reading "The Emotional Brain" by Joseph LeDoux, who pioneered important research into this region.

This study identified 3 types of dopamine neurons in the VTA. While Type 1 and Type 2 neurons did not respond to fearful events, actually decreasing their firing rates but with a rebound at the cessation of the fearful event, Type 3 neurons increased their firing rate. Thus ...

Moreover, the excitation duration of type-3 dopaminergic-like neurons also correlated with the duration of fearful events.

However I am puzzled by this and have to wonder if it points to error in identifying these Type 3 neurons:

Our pharmacological results revealed that the vast majority (96%; 23/24) of type-1 and type-2 putative dopamine neurons were significantly suppressed, while surprisingly the type-3 neurons (n = 9) otherwise showed excitation by apomorphine

The bods then went onto to test how these neurons responded to both positive and aversive events:

Neuronal activity recordings in these conditioned mice (after 1-week training) revealed that VTA putative dopamine neurons responded significantly to the conditioned tone that predicted a sugar pellet in the reward chamber (Figure 6D, left panel). Interestingly, the same VTA neurons also responded reliably to the same conditioned tone when it predicted free fall in the free fall chamber (Figure 6D, middle panel). When the same conditioned tone was delivered to mice in a neutral chamber that was not associated with any event, it did not produce significant changes in firing.

What this suggests is that these neurons in the VTA are not only responding to reward or adversity but also to the expectation that something in the environment is about to change. It would be interesting to see if any of these neurons would respond to innocuous environmental contingencies. I have a sneaking impression that what we are witnessing here is a general alerting function to a change in the environment, with different neurons providing information about the nature of the environmental change. This information is highlighted by a sentence in the closing paragraph of the paper:

These putative dopamine neurons respond to different negative events in a similar manner and more importantly, their temporal durations of dynamic firing changes are proportional to the durations of the fearful events.

The Horror, The Horror!

Political Conservatives Fear Chaos; Liberals Fear Emptiness

Mistah Kurtz died long ago so get over it. (With apologies to the wonderful Joseph Conrad)

Keep in mind that with these studies the results are statistical so don't go around thinking that because someone has liberal or conservative political beliefs ipso facto that particular person experiences what the study results suggest.

According to this study conservatives fear of social chaos and absence of order while liberals fear emptiness. The potential for social chaos and absence of order is always a problem for societies so these things need to be guarded against. As for feelings of emptiness just get over it. The universe is a cold heartless place and the sooner you realise that and go on living the better off you will be. Stuff the rubbish touted by Deepak Chopra, Gary Zukav, and even Anthony Robbins for that matter. These people are fools who delude others into thinking that life truly is meaningful. It isn't. This has long been known but few are willing to embrace it wholeheartedly. When people do truly accept the meaninglessness of existence they realise it was a stupid thing to worry about. Alas I fear that humanity will continue to generate all manner of Imaginary Friends to keep The Horror away. As that wonderful French writer Albert Camus noted, "Seeking the truth is not seeking what is desirable." More importantly, remember his words:

But it is bad to stop, hard to be satisfied with a single way of seeing, to go without contradiction, perhaps the most subtle of all spiritual forces. The preceding merely defines a way of thinking. But the point is to live.

The Myth of Sisyphus.

So if you are a conservative and fear emptiness the problem is that you fear nothingness. When you think about it, that's kinda stupid. At least conservatives aren't that silly.