Setting up connections with hoc
Model
A simplified NEURON implementation of the Hopfield and Brody
model described in
JJ Hopfield and CD Brody, PNAS 97:13919 (2000)
and
JJ Hopfield and CD Brody, PNAS 98:1282 (2001)
For detailed information about the original model see
http://str.princeton.edu/mus/Organism/
Implementation
The file model_hb_ex.hoc contains the specifications of cells and synapses.
The "event times pattern" is read
from the exemplar.txt file into the chan[inchan] vector.
The cells in the processing layer (alpha and beta) are
arranged in an array and, thus, each cell is identified by two indexes.
A subset of 30 cells has been preselected
to recognize the input pattern.
A list of the indexes for these cells is read from the connections.txt
file into the index[dimcon][2] array.
Exercise
Go to the course/hb directory and compile the mod files for the Na+ and K+
conductances that are used in this exercise.
Before running the hb_ex.hoc simulation, edit the model_ex_hb.hoc file to add
the hoc code that establishes all-to-all connections among the preselected cells.
Look at the
NEURON help file
for the syntax and parameters for
the NetCon() statements, and use the following pseudocode for hints:
for i=0 to dimcon-1 {
x0=index[i][0]
y0=index[i][1]
connect a[x0][y0] with gamma
connect b[x0][y0] with gamma
for j=0, dimcon-1 {
x1=index[j][0]
y1=index[j][1]
if (j!=i) {
connect a[x0][y0] with a[x1][y1]
connect b[x0][y0] with b[x1][y1]
}
connect a[x0][y0] with b[x1][y1]
connect b[x0][y0] with a[x1][y1]
}
}
In model_ex_hb.hoc there are predefined object names
that you should use to
define the connections :
netga[ ] for alpha --> gamma,
netgb[ ] for beta --> gamma,
netaa[ ] [ ] for alpha --> alpha,
netbb[ ] [ ] for beta --> beta,
netab[ ] [ ] for alpha --> beta,
and
netba[ ] [ ] for beta --> alpha.
The connection weights between the preselected cells
are initialised before each simulation
(look at the run_x procedures in the
hb_ex.hoc simulation file).
NEURON hands-on course
Copyright © 2001 by M. Migliore,
all rights reserved.