Neural correlates of tactile detection: a combined
magnetoencephalography and biophysically based computational modeling
study.  Jones SR, Pritchett DL, Stufflebeam SM, Hamalainen M, Moore
CI.  J Neurosci. 2007 Oct 3;27(40):10751-64.

Previous reports conflict as to the role of primary somatosensory
neocortex (SI) in tactile detection. We addressed this question in
normal human subjects using whole-head magnetoencephalography (MEG)
recording. We found that the evoked signal (0-175 ms) showed a
prominent equivalent current dipole that localized to the anterior
bank of the postcentral gyrus, area 3b of SI. The magnitude and timing
of peaks in the SI waveform were stimulus amplitude dependent and
predicted perception beginning at approximately 70 ms after
stimulus. To make a direct and principled connection between the SI
waveform and underlying neural dynamics, we developed a biophysically
realistic computational SI model that contained excitatory and
inhibitory neurons in supragranular and infragranular layers. The SI
evoked response was successfully reproduced from the intracellular
currents in pyramidal neurons driven by a sequence of lamina-specific
excitatory input, consisting of output from the granular layer
(approximately 25 ms), exogenous input to the supragranular layers
(approximately 70 ms), and a second wave of granular output
(approximately 135 ms). The model also predicted that SI correlates of
perception reflect stronger and shorter-latency supragranular and late
granular drive during perceived trials. These findings strongly
support the view that signatures of tactile detection are present in
human SI and are mediated by local neural dynamics induced by
lamina-specific synaptic drive. Furthermore, our model provides a
biophysically realistic solution to the MEG signal and can predict the
electrophysiological correlates of human perception.


Implementor's Notes:

The implementation of the S1 soamtosemsory cortex is an ongoing
effort.  The present version has been explanded from its present one
dimensional geometry to a two dimensional cortical sheet. We
anticipate this will be posted on ModelDB once the results from it
have been published. See http://CompNeuroSci.info for updates.

Executing "nrniv batch.hoc -" will generate a concatenated file
representing 100 trial runs. To replicate the simulation figures in
the paper the relevant configuration file is specified (see below),
and the averaged waveforms are filtered (see paper).

The demo of the simulation illustrates a single trial run. After
compiling all mod files run 'nrngui' then load hoc file
'init-cortex.hoc'. After loading one of the three configuration files;
load demo.ses and a short time later the following figures should
appear (the example below used the wiring-config_suprathresh.hoc
configuration file). Restart with each configuration file.



(try each of the three configuration files).

Index of hoc files:
batch.hoc

This file will reproduce Figure 5 & 6 in the paper. The relevant
wiring configuration and output file name are set here.
--------------------------------------------------------------------
The following 3 wiring configuration files follow Tables 2 and 3 in
the paper.
----------------------------------------------------------
wiring-config_suprathresh.hoc 
Wiring configuration for the supra-threshold evoked response
----------------------------------------------------------
wiring-config_thresh_nonpercieved.hoc
Wiring configuration for the non-perceived evoked response
----------------------------------------------------------
wiring-config_thresh_percieved.hoc
Wiring configuration for the perceived evoked response
===========================================================
wiring_proc.hoc
Procedures called by the wiring configuration files
--------------------------------------------------------------------
sj3-cortex.hoc
The templates for the cells, synapses and exogenous feeds are defined
in this file. The cells and feeds are instantiated and the dipoles
"placed".
--------------------------------------------------------------------
noise.hoc
The noise procedures are defined in this file.
--------------------------------------------------------------------
dipole.hoc
Template for the dipole in a single cell

20120131 cad.mod solve methods updated to derivimplicit from euler as
per http://www.neuron.yale.edu/phpbb/viewtopic.php?f=28&t=592