Kenneth D. Miller, Ph.D.

Computational Neuroscience

My lab's interests focus on understanding the cerebral cortex. We use theoretical and computational methods to unravel the circuitry of the cerebral cortex, the rules by which this circuitry develops or "self-organizes", and the computational functions of this circuitry.

One goal of the lab is to understand the role of activity-dependent, "correlation-based" mechanisms of synaptic plasticity in determining cortical structure and function (see lab publications on Models of Neural Development, below). Under these mechanisms, synaptic change appears to follow a rule like that proposed by Hebb in 1949: a synapse is strengthened when pre- and postsynaptic activations are correlated. We have analyzed cortical development in the presence of such plasticity. One prominent feature of visual cortical development is the formation of ocular dominance columns. These are alternating patches of cortical cells that receive input only from the left eye or only from the right eye. The left- and right-eye inputs segregate, beginning from an initially intermixed condition, through an activity-dependent synaptic competition. We have predicted the conditions under which input neural activity will lead to such segregation, and the size of the resulting patches. Another feature of visual cortex is the tuning of the cells to respond to light-dark borders of a particular orientation. Our analysis revealed that the development of such orientation selectivity can be explained by a correlation-based competition between ON-center and OFF-center inputs to the visual cortex, very much like the left-eye/right-eye competition that leads to ocular dominance column formation but in a different parameter regime. More recently we have addressed the combined development of ocular dominance and orientation selectivity, showing how the orientation preferences of the two eyes can become matched despite the tendency of the two eyes to segregate from one another. All of these models make strong, testable predictions as to the pattern of correlations that must exist among the activities of inputs to cortex during development, if the mature cortical structure arises by correlation-based rules. In addition, our hypothesis as to the mechanism of matching of the two eye's orientation preferences leads to testable predictions for the relationship between the two eye's receptive fields in mature visual cortical cells, and explains existing observations of the distribution of best stimulus disparities in these cells.

Another goal of the lab is to develop realistic and testable models of mature cortical circuitry (see lab publications on Models of Neuronal Integration and Circuitry, below). We have developed improved simple models of cortical excitatory cells and shown how these naturally account for the high variability of cortical responses. We have developed a candidate circuit model to explain the full response properties of cortical cells in layer 4 (the input-recipient layer) of cat primary visual cortex, addressing the invariance of orientation tuning under changes in stimulus contrast and a variety of other response properties. The model makes a number of predictions, notably as to the response properties of inhibitory neurons in layer 4. This circuit model involves "correlation-based intracortical circuitry", and thus closely connects with the studies described above of cortical development. We are now working on a number of other aspects of the V1 circuit and also on the circuitry of other areas, such as monkey visual area LIP.

While I was at UCSF, I also developed an experimental component to my lab, focused on the study of the simultaneous activity of many neurons in visual cortex using the "tetrode" method of recording (see lab publications on Experimental Results, below). Experiments applied these methods in cat visual cortex and LGN (the nucleus providing visual input to cortex). Additional publications from that work are still in process. I am not establishing an experimental lab at Columbia. Instead, Michael Stryker has taken over the operation of the lab at UCSF.

Publications:

(Here's info on on how to download and view these publications, including info on postscript, gzipped (.gz) files, pdf files, tar files, tiff files, and other related topics.)

Pubs are organized in 5 overlapping categories:

Most Recent Publications:

Some Reviews/Overviews:

Models of Neural Development:

If you're just getting started: here's a link to a guided tour through the papers related to models of visual cortical development.

Models of Neuronal Integration and Circuitry:

Experimental Results:

Publications: How to download and view

To download a paper: click on 'compressed postscript' (for a version compressed with gzip; file ends in .gz; uncompress with 'gunzip') or 'uncompressed postscript' (for a plain postscript version; takes longer to download, so use 'compressed' if your browser understands .gz).
Recent papers have 'pdf' (portable document format) option rather than uncompressed postscript. Most browsers know what to do to display pdf files; if yours doesn't, you can read pdf files with Acrobat Reader (freely downloadable) or various public domain programs.

Postscript and gzip

Can't read postscript? Pick up ghostscript/ghostview; this link includes pointers to Mac and PC as well as Unix versions.

To read compressed files: It's easy to install gzip/gunzip on your system: Click here to find Mac and Dos executables for gzip/gunzip, as well as source code that should compile on any Unix machine. Web browsers can be easily configured to automatically gunzip .gz files; talk to your system manager, or see Los Alamos faq, described below. Windows users: compressed (gzipped) files can also be unpacked with winzip.

Terrific general information about getting started with postscript and gzip, including how to get your browser to automatically uncompress and display gzipped postscript, is here at the faq of the Los Alamos physics e-print archives.

Tar and tiff

Parts of a few papers, where indicated, are available only as tar files of compressed postscript and/or tiff files. A tar file is a Unix file that packs together a whole set of files. Save the file to some filename.tar; then, to unpack the file on a Unix system, say "tar xvf filename.tar". Windows users can unpack tar files with winzip. After unpacking, most of the resulting files will end with ".gz", meaning they've been compressed with gzip.

If you can't view tiff files, and run X-windows, pick up xv, a nice image manipulation and viewing shareware program for X-windows.

Guided tour of cortical development papers:

If you wish to get started reading the papers on models of cortical development, I recommend the following path (for postscript files, I link here to the compressed versions; links to the uncompressed versions are also available, above):

See Also: