Tuesday, 15 May 2018
Memory Engrams: The Physical Traces of Memories in Your Brain
In 1923, German biologist Richard Semon proposed the engram theory of memory. According to this theory, when a person experiences something, a set of selected stimuli from this experience activates entire populations of neurons in that person’s brain, thus inducing lasting chemical and physical changes in their connections. These changes are known as the engram. Each of the assemblies of neurons thus selected thereby contributes to the storage of the memory.
As we shall see in a moment, this was a visionary concept, but Semon’s theory was almost completely ignored until the 1970s, when an article by Daniel Schacter, James Eich, and Endel Tulving brought it back into the scientific discussion. (more…)
Memory and the Brain | Comments Closed
Tuesday, 1 May 2018
Limitations of Brain Mapping
With the use of tracers, dyes and modern brain-imaging technology, it is now possible to produce maps of the human brain. But why would we want to do so? Simply because our cognitive functions emerge from interactions among numerous parts of the brain, in many cases physically quite distant from one another. If we can map the neural highways that form the various networks in our brains, or better still, understand which are the preferred highways for use in particular situations, we can learn a lot about how we go about talking, thinking and behaving.
But because the brain is so complex, brain mapping involves many problems and is subject to some major limitations. In this post I will discuss just two of these problems and a few limitations inherent in efforts to map the “connectome”—to prepare a map of all the nerve bundles connecting the neurons to one another in a given brain. (more…)
From the Simple to the Complex | Comments Closed
Sunday, 25 March 2018
The Many Events Without Which We Wouldn’t Be Here To Talk About Them
In the course of evolution, there have been many times when the future existence of my brain as I write these lines and yours as you read them has hung by the slenderest thread. Without the events, many of them quite unlikely, that occurred at these times, we would not be here today to speculate about their nature (or at least not in our current form). (more…)
From the Simple to the Complex | Comments Closed
Wednesday, 7 March 2018
“Winner effect” Makes Subordinate Mice Dominant
This week I’d like to tell you about an experiment by Hailan Hu and his team at Zhejiang University, in China. These researchers used optogenetic methods and various wavelengths of light to excite or inhibit, on command, a particular population of neurons in the dorsomedial prefrontal cortex (dmPFC) of mice. (These neurons receive their natural inputs from the mediodorsal portion of the thalamus.) When the researchers excited these neurons in previously subordinate mice, they began to win confrontations with previously dominant mice, forcing them to retreat in a tube resembling a narrow tunnel (see photo above) and let them pass first. (more…)
Pleasure and Pain | Comments Closed
Thursday, 22 February 2018
Walking in Nature Stops You from Brooding
If you can manage it, try to go out and walk a bit each day in a large park or other green space (not always easy in poor neighbourhoods. Why? Because yet another study, since the first one by Roger Ulrich in 1984, has confirmed the benefits of natural environments for reducing our tendency to ruminate (focus our thoughts repetitively on negative aspects of ourselves). This new study was done by Gregory Bratman and his colleagues. It is entitled “Nature experience reduces rumination and subgenual prefrontal cortex activation”, and it was published in the journal PNAS in July 2015. (more…)
Body Movement and the Brain | Comments Closed
