Math 490N / Biol 595N April 13 Reading Assignment and Class Discussion Instructions

I will not be in class on Tuesday, April 13, but you will organize yourselves into groups for a discussion of the readings for the class, and then, perhaps, have a cross group discussion of the topics that do not seem clear. (Yes, this will be on the test!)

Up until now, in this course, we have taken a microscopic, cell by cell, view of the subject of computational neuroscience. This reflects both my prejudice on where the most effective work on the subject has been done, and also the areas where the most work has been done. It is clear, however, that we will never have a complete picture of how neural systems work in any but the simplest animals by trying to build up from the cell by cell picture. On the other hand, it is not at all clear what other pictures are possible that can illuminate the questions we wish to find answers to!

The main article for today's class discussion, Hasson, et al, "Intersubject Synchronization of Cortical Activity During Natural Vision", Science 303: 1634-1640, 12 March 2004, illustrates the kind of work that is being done increasingly often to address questions about higher level processes. The foundation of these experiments is Blood Oxygenation Level Detection (BOLD) which indicates the level of cortical activity. The point is that the cellular activity in neural signalling (e.g. operating ion pumps and opening and closing channels) uses energy and oxygen, so that cortical activity is related to oxygen use. Unfortunately, for example, oxygen use cannot be directly used, apparently, to distinguish between excitatory and inhibitory signalling.

The Papers Forming the Foundation for the Discussion

  • Hasson, et al., Intersubject Synchronization of Cortical Activity During Natural Vision, Science 303: 1634-1640, 12 March 2004 The main paper.
  • Hasson, et al., Intersubject Synchronization of Cortical Activity ..., Supplement Supplement to main paper, with more information than was in the article.
  • Hasson, et al., Large Scale Mirror Symmetry Organization of Human Occipito-Temporal Object Areas, Neuron 37: 1027-1041, 2003. Pages 12 and 13 give experimental set up for the 2004 paper.
  • Sea Chen, Charles Bouman, and Mark Lowe, Clustered Component Analysis for Functional MRI, to appear, 2004. Pages 1 to 4 give background on BOLD; this is a different mathematical anlyysis than the Hasson papers.
  • Charles Bouman, Sea Chen, and Mark Lowe, Clustered Component Analysis for FMRI Signal Estimation and Classification, to appear, 2004. Apparently a shorter version of the above paper by the same authors.

  • Discussion Questions

  • What is BOLD?
  • What are some limitations of BOLD?
  • Contrast the sort of information Hasson and his co-authors report with the sort of information studied in the models we have looked at earlier.
  • What do the authors mean by the words "natural vision" in the title, that is, to what are they contrasting what they have done?
  • What do the authors claim to have found? Do you think their conclusions are justified?
  • What are some of the special processing areas of the brain that the findings of this paper provide evidence for?
  • Not all of the cortical areas of the subjects were highly correlated; why might that be?
  • If you were in the authors' lab, what would you suggest as some follow-up questions for further investigation?
  • The authors do not directly address the mathematics involved in the analysis of their results; what kinds of mathematical tools do you think they should be using in their analysis?

  • Last Update: April 11, 2004

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