Goals

My goal for Spring 2008 is to construct an executable neural model that will translate a simulated-biological system’s angular requirements (preferred directions) into plausible neural signals as recorded by invasive electrodes. The simulator will accomplish its goal by uniting pre-existing fractal and neural simulation tools into a cohesive package to construct an executable 2-dimensional neural columnar model conforming to the topography of the human motor cortex as report by Mountcastle (1997)¹ and Georgeopolous (2007)². The model will be limited to approximately 100 roughly-hexagonal columns comprised of 64- 80 mini-columns each.

I will use this project as the subject matter for completing a formal thesis proposal.

Important Dates

Future Goals

Using fractal methods:

1. Modify the fractal map for multiple pd layers.
2. Adapt mask to mimic interneurons.

Within NEURON:

1. Replicate a 3-d columnar structure. Neurons in layers II, III & IV demonstrate similar preferred directions (pd) in the vertical dimension and are organized into slightly overlapping mini-columns and columns. Mini-columns form from the dendrites of 3 to 20 large layer V & VI pyramidal cells that, while ascending to layer I, collect layer II & III dendrites along their path to total ~80 to 100 neurons (striate cortex is ~2.5x larger). Columns form from 64 (30µm-diameter) to 80 (50 to 60µm-diameter) mini-columns normally bound together by cell-autonomous and histogenetic influences. The mini-columns are spaced at 20 to 80µm center-to-center creating columns² ranging in diameter from 240 to 600µm. As each column represents a full 360° pd, mini-columns represent roughly 5.62° pd and coalesce as doublets and triplets of similar pd’d mini-columns.

References

1. Mountcastle, V. B. (1997). The columnar organization of the neocortex. Brain, 120 ( Pt 4), 701-22. [↩]
2. Georgopoulos, A. P., Merchant, H., Naselaris, T. & Amirikian, B. (2007). Mapping of the preferred direction in the motor cortex. Proc Natl Acad Sci U S A, , . [↩]