In the SERCOM Noise routine, a series of noise bursts is generated during an optional visual stimulus. At the same time, neuronal response data from the animal is collected and displayed.
The waveform of the noise bursts is obtained from an existing dataset in a data file. By default, the noise waveform is the dataset n25k, which is stored in the data file [populin.waves]noisewave.dat . As soon as the Noise option is specified (hitting 'n' from the SERCOM program), the user is given the option of using the default noise waveform, or specifying a different one. One can also change to a different waveform while running the Noise routine, by typing the 'f' command. (See the discussion of this and other commands, below.)
After specifying the waveform dataset, the Noise menu will be displayed. It is here that the various stimulus parameters are specified. Below is a sample Noise menu.
Speaker selection (0 - 15) = 9 Speaker attenuation = 20.00 dB Led selection (0 - 15) = 7 Led intensity (1 - 8) = 4 Give reward (0=no, 1=yes) = 0 Led duration = 4000.00 msec Spotting time = 800.00 msec Led off-time = 1500.00 msec Stimulus Duration = 250.00 msec Repetition Time = 350.00 msec Stimulus Delay = 50.00 msec w=Dset(name), u=Dset(unit#), x=Dset(seq#), d=t=Scr Dump, f=Fetch Waveform p=P=CTRL-P=Pause, g=G=CTRL-G=Go, e=E=CTRL-Z=Exit, r=R=Retrieve, s=S=Store
After the parameters are all specified, the user types the letter 'g' or 'G' to start things off. The visual stimulus (Led selection) will turn on. After a brief Spotting time, a series of noise bursts will start. In this example, there will be 1 noise burst every 350 msec (Repetition Time). Within this repetition time, there will be a Stimulus Delay of 50 msec, then the noise burst, with a Stimulus Duration of 250 msec, is presented. The stimulus delay allows for collecting neuronal data before each auditory stimulus starts.
The visual stimulus remains on for the entire Led duration period of 4000 msec. The successive noise bursts will continue only as long as the visual stimulus remains on. At the end of this time, both stimuli turn off and remain off during the specified Led off-time period. This cycle is then repeated over and over again.
Note that the number of noise bursts in each cycle is not specified by the user. It is determined by the repetition time of the bursts and by the led duration time. In this example, there is enough time for 9 noise bursts to be presented during each led duration.
Note that the visual stimulus is optional -- it can be omitted by setting the Led selection parameter to 0. However, the parameters Led duration, Spotting time, and Led off-time must still be specified. One can use a very long Led duration time to accomodate a long series of noise bursts.
The following figure illustrates the timing of the noise bursts with respect to the visual stimulus.
If the specified duration time of the auditory stimulus is longer than the playback time of the noise waveform, the waveform will be repeated until the full duration time is reached.
If the parameter Give reward is set to 1, then the animal will receive a reward at the end of each led duration (even if the led selection is set to 0).
The output display of the Noise routine has two parts. There is a plot of the accumulation of spikes generated after every series of noise bursts, plus a dot raster display of the spike times during each repetition interval.
The arrow keys are used to move around in the menu. There are also several single-character commands available to the user at all times, while in the Noise menu. They are listed here, and described in more detail below.
g, G, or ^G Start or restart stimulus p, P, or ^P Stop stimulus, stay in Noise menu e, E, or ^Z Stop stimulus, return to SER main menu f or F Fetch new noise waveform from user file d or D Dump next spike display to printer t or T Dump next spike display to printer s or S Store current menu params to special block r or R Retrieve menu params stored by 's' w or W Save current data, specify data set name u or U Save current data, increment unit # x or X Save current data, increment sequence #
After setting the parameters to the desired values, the series of Noise bursts is started by typing CTRL-G. At the end of each series of bursts, the display will be updated and the bursts will be generated again. This continues until the user stops the stimulus. As with the FM Sweep routine, 'e' is used to exit, and 'p' stops the stimulus. Any individual parameter can be changed at any time -- type the new value, then hit 'Return' or one of the arrow keys to move the cursor. Then, stimulus will stop and restart with the new parameter values. Note that, as with the FM Sweep, it is can be faster to change a number of parameters by first typing 'p' to stop the stimulus, then modifying the parameters, then hitting 'g' to restart.
With the Noise stimulus there is the special feature of a private storage block for the menu parameters. To store the current set of menu parameters into this storage block, type 's' or 'S'. Then, continue to run the stimulus, changing any parameter to a new value. To retrieve the set of parameters stored by the S command, type 'r' or 'R'.
There is now a hard copy feature, specified with the 'D' or 'T' option. Simply type D or T and the program will send to the printer a copy of the spike curve and dot raster at the end of the current series of noise bursts. (The display is only updated at the end of each series of bursts, and so both the 'd' and 't' options have been designed to do the same thing, that is, to send a hard copy dump of the next update of the display.)
Invalid parameter settings sometimes cause the stimulus to stop. The user must change the appropriate parameter(s), then type 'g' or CTRL-G to restart the stimulus.
To store the response data from the current series of noise bursts, the user can type 'w', 'u', or 'x'. Each of these commands stores the data for the entire series of bursts. The only difference between the 3 commands is how the name for the new data set is chosen. Each command displays the name of the most recently stored data set. The 'w' command prompts the user to type in a new name for the data set to be stored. The 'u' or the 'x' command will try to automatically create a new data set ID name. They look at the previous name, which is understood to have the format 'unit#-sequence#', preceded by an optional string of characters. For example, a valid name would be abc100-12, where the unit number is 100 and the sequence number is 12. The 'u' command will increment the unit number, and the 'x' command will increment the sequence number. If the previous data set name is not in this format, then each of the commands will prompt the user to type in a new data set id name.
The data for a series of noise bursts are stored with the data set type name SCNO, which will distinguish it from data collected during one of the other stimulus options. The schema name for each data set is SCH019.
See also the general description of the
SERCOM program.
See also the descriptions of the other SERCOM stimulus options:
Tone Pips,
Clicks,
jane@neurophys.wisc.edu