Monday, March 28, 2011

Patrick Lockberby - Artice Ice Update - March 2011

Hmmm, this is not good:

"Arctic sea ice extent for February 2011 tied with February 2005 as the lowest recorded in the satellite record." 

Interestingly, 2005 was a year of very high sunspot activity and this year sunspot activity is also high.

Apocalypse 2012: An Investigation into Civilisation's End

Book Review: Apocalypse 2012: An Investigation into Civilisation's End.
Lawrence E. Joseph.
Broadway Books, New York, 2007

I find this a perplexing text. So many new ideas from so many different sources. The author traveled around the world to interview scientists, psychics, Mayan ancestors, and various individuals ranging from shamans to mystics. It would take me far too long to investigate all the claims in this text. Other reviews on this text indicated a mixture of respect and caution in judging this text. There are errors, there must be errors, but there is enough solid material in this text to leave me interested.

The first two thirds of the text are an entertaining read. The author employs an easy reading style that doesn't become too technical and bogged down. Thankfully the text is not alarmist or written as if being some great document of revelation. He quotes the relevant individuals, he puts forward their ideas clearly and without editorialising their statements.

Sunday, March 13, 2011

A Counter Intuitive Study on Longevity

There is no easy way to establish strategies for living a long life. This news release adds to our confusion. I proffer the following cautions:

  1. This study contradicts many other studies. When that occurs don't accept the study at face value, it needs to be subject to critical review by many people, and believe me that is far superior to peer review! 
  2. This study is relying on data gathered a very long time ago, when experimental methods were much less refined than today. 
  3. It relates to analysis of "more than 1500 bright children". Small sample, and just what do they mean by "bright". 

The new release does not point to a published paper, the results are being published in book form. I would much prefer that they first publish a series of papers then publish their book. By publishing the book first they are putting out a view on longevity that has not been subject to (1) above.

For myself at least I have to disregard the claims of this news article. Yes I can see elements that I find plausible but in the absence of a series of papers that have been subject to critical review and discussion by a wide range of people it is virtually impossible to know if all their conclusions are valid.

There is a good lesson here in relation to health news. There are also sorts of claims being made about the secrets to longevity. There are no secrets, we're still learning, but obviously a good deal of common sense goes a very long way. Eat well, exercise regularly, and don't go looking for fountains of longevity.

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.