NetCon

classes
   active         postloc        preloc         valid          
   delay          pre            record         wcnt           
   event          precell        syn            weight         
   postcell       precelllist    synlist        x              
   postcelllist   prelist        threshold

SYNTAX

section netcon = new NetCon(&v(x), target, threshold, delay, weight)
netcon = new NetCon(source, target, threshold, delay, weight)
section netcon = new NetCon(&v(x), target)
netcon = new NetCon(source, target)

DESCRIPTION

Network Connection object that defines a synaptic connection between a source and target. When the source variable passes threshold in the positive direction at time t-delay, the target will receive an event at time t along with weight information. There is no limit on delay except that it be >= 0 and there is no limit on the number of events pending delivery.

If the optional threshold, delay, and weight arguments are not specified, their default values are 10, 1, and 0 respectively. In any case, their values can be specified after the netcon has been constucted, see threshold weight and delay .

The target must be a PointProcess that defines a NET_RECEIVE procedure. The number of NET_RECEIVE procedure arguments define a weight vector whose elements can be accessed with through the NetCon.weight ( weight )variable but the weight argument in the above constructors specify the value of the first argument, with the normal interpretation of weight or maximum conductance. On initialization, all weight elements with index > 0 are set to 0 unless the NET_RECEIVE block contains an INITIAL block. In the latter case, that block is executed on a call to finitialize and allows non-zero initialization of netcon "states" --- args not initialized in the INITIAL block would be analogous to a Parameter except that it can have a different value for different NetCon instances and can be set to a desired value with weight .

The target is allowed to be nil (NULLObject) in which case the NetCon is always inactive. However this can be useful for recording (see record ) the spike train from an output cell.

The source is normally a reference to a membrane potential which is watched during simulation for passage past threshold. The currently accessed section is required by the local variable time step method in order to determine the source "cell". Any range variable may be a source variable but I suspect that membrane potential is the only practical one.

The source may also be a PointProcess with a NET_RECEIVE block which contains a call to net_event. PointProcesses like this serve as entire artificial cells.

The source may also be a PointProcess which contains a "x" variable which is watched for threshold crossing, but this is obsolete since NET_RECEIVE blocks which explicitly call net_event are much more efficient since they avoid the overhead of threshold detection at every time step.

The source may be a NULLObject. In this case events can only occur by calling event from hoc. (It is also used by NEOSIM to implement its own delivery system.)

A source used by multiple NetCon instances is shared by those instances to allow faster threshold detection (ie on a per source basis instead of a per NetCon basis) Therefore, there is really only one threshold for all NetCon objects that share a source. However, delay and weight are distinct for each NetCon object.

From a NetCon instance, various lists of NetCon's can be created with the same target, precell, or postcell. See netconlist for creation of NetCon lists from a target, precell, or postcell pattern or object.

BUGS

NetCon can currently only be used if a CVode object exists.

valid

NetCon

SYNTAX

boolean = netcon.valid()

DESCRIPTION

Returns 0 if the source or target have been freed. If the NetCon object is used when it is not valid a runtime error message will be printed on the console terminal.

active

NetCon

SYNTAX

boolean = netcon.active(boolean)
boolean = netcon.active()

DESCRIPTION

Turns the synapse on or off in the sense that when off, no events are delivered using this NetCon instance. Returns the previous state (or current state if no argument).

event

NetCon

SYNTAX

netcon.event(tdeliver)

DESCRIPTION

Delivers an event to the postsynaptic point process at time, tdeliver. tdeliver must be >= t . Note that the netcon.delay is not used by this function. Because it is a delivery event as opposed to an initiating event, it will not be recorded in a NetCon.record(Vector).

syn

NetCon

SYNTAX

target_object = netcon.syn()

DESCRIPTION

Returns a reference to the synaptic target PointProcess.

pre

NetCon

SYNTAX

source_object = netcon.pre()

DESCRIPTION

Returns a reference to the source PointProcess. If the source is a membrane potential then the return value is NULLobject

preloc

NetCon

SYNTAX

{x = netcon.preloc() ... pop_section()}

DESCRIPTION

The source section is pushed onto the section stack so that it is the currently accessed section. Pop_section must be called after you are finished with the section.

BUGS

The return value of x is .5 unless the source is a membrane potential and located at 0, or 1, in which case value returned is 0 or 1, respectively. Therefore it does not necessarily correspond to the actual x value location. If the source was an object, the section is not pushed and the return value is -1.

postloc

NetCon

SYNTAX

{x = netcon.postloc() ... pop_section()}

DESCRIPTION

The section of the target point process is pushed onto the section stack so that it is the currently accessed section. Pop_section must be called after you are finished with the section. The x return value is the relative location of the point process in that section.

precell

NetCon

SYNTAX

cellobj = netcon.precell()

DESCRIPTION

If the source is a membrane potential and the section was declared in an object (defined in a cell template), a reference to the presynaptic cell (object) is returned.

postcell

NetCon

SYNTAX

cellobj = netcon.postcell()

DESCRIPTION

If the synaptic point process is located in a section which was declared in an object (defined in a cell template), a reference to the postsynaptic cell (object) is returned.

prelist

NetCon

SYNTAX

List = netcon.prelist()
List = netcon.prelist(List)

DESCRIPTION

List of all the NetCon objects with source the same as netcon. With no argument, a new List is created. If the List arg is present, the objects are appended.

synlist

NetCon

SYNTAX

List = netcon.synlist()
List = netcon.synlist(List)

DESCRIPTION

List of all the NetCon objects with target the same as netcon. With no argument, a new List is created. If the List arg is present, the objects are appended.

SEE ALSO

netconlist

postcelllist

NetCon

SYNTAX

List = netcon.postcelllist()
List = netcon.postcelllist(List)

DESCRIPTION

List of all the NetCon objects with postsynaptic cell object the same as netcon. With no argument, a new List is created. If the List arg is present, the objects are appended.

SEE ALSO

netconlist

precelllist

NetCon

SYNTAX

List = netcon.precelllist()
List = netcon.precelllist(List)

DESCRIPTION

List of all the NetCon objects with presynaptic cell object the same as netcon. With no argument, a new List is created. If the List arg is present, the objects are appended.

SEE ALSO

netconlist

delay

NetCon

SYNTAX

del = netcon.delay
netcon.delay = del

DESCRIPTION

Time (ms) between source crossing threshold and delivery of event to target. Any number of threshold events may occur before delivery of previous events. delay may be any value >= 0.

wcnt

NetCon

SYNTAX

n = netcon.wcnt()

DESCRIPTION

Returns the size of the weight array.

weight

NetCon

SYNTAX

w = netcon.weight
netcon.weight = w
x = netcon.weight[i]
netcon.weight[i] = x

DESCRIPTION

Weight variable which is delivered to the target point processes NET_RECEIVE procedure. The number of arguments in the model descriptions NET_RECEIVE procedure determines the size of the weight vector. Generally the 0th element (no index required) refers to synaptic weight and remaining elements are used as storage by a synaptic model for purposes of distinguishing NetCon streams of events. However if the NET_RECEIVE block of the post synaptic point process contains an INITIAL block, that block is executed instead of setting all weight[i>0] = 0.

threshold

NetCon

SYNTAX

th = netcon.threshold
netcon.threshold = th

DESCRIPTION

Source threshold. Note that many NetCon objects may share the same source.

x

NetCon

SYNTAX

x = netcon.x
netcon.x = x

DESCRIPTION

Value of the source variable which is watched for threshold crossing. If the source is a membrane potential then netcon.x is a reference to that potential. If the source is an object, then netcon.x is a reference to the objects field called "x", ie source.x .

record

NetCon

SYNTAX

netcon.record(Vector)
netcon.record()

DESCRIPTION

Records the event times at the source the netcon connects to.

With no argument, no recording at the source takes place.

The vector is resized to 0 when finitialize is called.

NB: Recording takes place on a per source, not a per netcon basis, and the source only records into one vector at a time.

If a source is recording a vector, that source is not destroyed when the last netcon connecting to it is destroyed and it continues to record. The source is notified when the vector it is recording ceases to exist---at that time it will be destroyed if no netcons currently connect to it. To do a recording of a source, the following idiom works: 

objref vec, netcon, nil
vec = new Vector()
netcon = new NetCon(source, nil)
netcon.record(vec)
objref netcon
The source will continue to record events until record is called with another netcon connecting to the source or until the vec is destroyed. Notice that this idiom allows recording from output cells (which normally have no connecting netcons) as well as simplifying the management of recording from cells.

Note that NetCon.event(t) events are NOT recorded.

neuron/neuron/classes/netcon.hel : 9590 Oct 10