In Search of Memory

A few weeks ago, I read Eric Kandel’s In Search of Memory. It was different from the books that I normally post about here, as it is an autobiography with the emergence of modern neurobiology woven in, rather than an argument for this or that perspective. But I am a neurobiologist at heart and an aspiring scientist at the very beginning of my career, so I couldn’t resist:

memory

Eric Kandel won the nobel prize in the year 2000 for his pioneering work on the molecular mechanisms of memory formation and storage. In this book, Kandel lays down the path of his life, professional and otherwise, from his earliest days in Vienna, just before World War II, up through his acceptance of the nobel prize in Stockholm, just a few years ago. His book will be of interest to biologists, philosophers, psychologists and laymen alike. The material is presented in the order that it was first discovered and assumes no prior knowledge, leaving no bars to entry for this exciting journey. All the same, weathered experimentalists will surely enjoy the ride that is the birth of this new science, from single-cell recordings in hippocampal cells, to the neural networks of Aplysia, to the beginnings of the differentiation of  the neural substrates for unconscious vs conscious information processing.

And a fun fact for those who are, like me, still trying to break into this field: What was Eric Kandel, nobel laureate in biology, studying in his Junior year of college? None other than Northern European History. He didn’t set foot in a lab until medical school, when he was entranced by the promises of psychoanalytic theory. I think we’ll be ok.

Finally, for those of you who wonder what I am doing when I am not reading or writing about consciousness (or wonder why I post so scarcely now!), I am now excitedly spending the majority of my time in the BRAIN Lab at Washington University in St. Louis on a summer research fellowship studying up on neurogenetics (i.e., how genetic variation influences how our brains respond to our environment and modulates risk for psychopathology). Check us out!

A Different Perspective

Now that I’ve finished Chalmers’ primary work on consciousness, I’ll be taking a brief break from more or less purely philosophical treatments. I finally managed to pick up a copy of Crick and Koch’s The Quest for Consciousness: A Neurobiological Approach from my university’s library. I’ve always had a great deal of respect for the authors, insofar as they were, and still are to an extent, among the first and few to assume a “scientific” approach in tackling consciousness, while admitting that there may be many things that purely empirical scientific inquiry will not be able to answer—notably the problem of qualia. Their final conclusion on the matter may not sit well with me once I discover it, but the mere fact that they take the time to discuss the problem is promising (many in the “mainstream” would do nothing more than dismiss the problem outright, denying that it is even a problem).

Regardless of the outcome, I am positive that the next few weeks will provide plenty of excitement and new ideas for me to consider on my own quest for consciousness.

A Rough Sketch of a Neurobiological Mechanism of Consciousness

I envision conscious states as being represented in the brain as local, transient patterns of neural activation linked together through a binding mechanism such as that proposed by Crick and Koch, or Gamma Wave Theory. At any instant in time, then, there is a specific subset of neurons firing in a brain that corresponds in some way to the current mental activity of the organism. For this picture, I adapt Damasio’s Convergence-Divergence Zone hypothesis, which states that across networks of brain regions, there exist highly connective nodes that record co-occurrent inputs, and activate a specific pattern of outputs. In doing so, by later activation of those outputs in the form of a memory, the original input pattern could be re-induced by Hebbian-type mechanisms. Since CDZs are highly interconnected, the evolution of a conscious state over time may be thought of as one pattern of neural activity systematically inducing another one, which induces another, and another, ad infinitum. If you are familiar with semantic networks, the idea is of some use in fully realising this proposal. In such networks, activation of one node (corresponding to, say, the idea of a dog) facilitates the activation of closely connected nodes (in this example, four-legged animals, or barking). My idea for conscious states over time corresponds very closely to this, except that it is not activation of individual nodes that matters, but activation of discrete patterns of nodes. Each activated node within this greater pattern can bring related nodes online, which depending on the strength and co-occurrence of activation, may induce another coherent pattern of activation through networks of CDZs.

I’ll continue this later.