October 01, 2008

The Organization of Memory And Internet Analogy

You are reading this particular article now on my website (in your computer and browser, of course!). There are billions of such websites and you picked mine. Perhaps you put your queries in the search box, which then showed you a list of results. You clicked my link there and lo, you are here!

The search engines (Google, Yahoo!, MSN and others) parse or read the webpages, index them and rank them. Each search engine has its own search robot, called bot, which crawls the pages. Now, this particular webpage that you are seeing is a part of my website. If you think of a website as a tall building, webpages may be considered as its floors. The search spiders not only crawl the website vertically (that is vertically up and down its individual floors), but they also move horizontally (clicking hyperlinks will lead you to arrive at some floor of another building) to be navigated to another webpage of another website.

Longitudinal (vertical) scanning picks up individual elements of the content, which are indexed (tagged) and remembered with respect to their locations, much like the human episodic memory in the hippocampus.

schematic representation of neurodesNow, its time for the bot to leave. It follows a hyperlink, if you have one, to a page of another website. So the search engine spider is directed to some floor in another building. Thus one might think of this search engine analogy to “neurodes and synapses” in artificial neural network. Here neurodes are the floors of the buildings and synapses are the hyperlinks (connections between them).

Next the search engine (Google) looks around in the floor to find similarities and dissimilarities from the floor it came. That is, it compares the webpages for relevance, in much the same way the anterior cingulated cortex (ACC) calculates “error related negativity” (ERN), and learns from it. It then calculates the ‘weight’ of association. It too learns from time to time by constant error related feedback, as happens in the ACC. Thus it assigns its hallowed “pagerank”.

Google PageRankPageRank is the relative importance of a page in Google’s eyes. ‘Page’ could come from Larry Page, co-founder of Google or more likely after ‘webpage’. One can see them in the Google toolbar in IE or Firefox, as a small green bar (Google’s own browser ‘chrome’ is yet to provide with a pagerank though). The lowest rank a page can have is 0, and the highest 10. Though the algorithm of pageranking is kept a secret like that of CocaCola, some insights may be had from “The Anatomy of a Large-Scale Hypertextual Web Search Engine” by Sergey Brin and Lawrence Page, founders of Google. I found a lot of resemblance of this paper with the architecture of learning and memory.

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Reference: hyper-links, unless specifically mentioned
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