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Classic conditioning experiment with aversive UCS.

The following measurement program was developed to implement a classic conditioning paradigm. Measures taken are Skin Conductance and Heart Rate, derived from EKG.

There are three phases, habituation, acquisition and extinction. During habituation, the subject is shown two pictures, CS+ and CS- stimuli. Each picture is presented for 4 seconds, 3 times, with pseudo randomisation of the CS+ and CS- mix and pseudo randomisation of Inter Stimulus Interval (ISI) (mean = 20 seconds, variation = +/- 5 seconds).

During the acquisition phase the same CS+ and CS- stimuli are presented with similar randomisation of ISI and stimulus distribution. However, each stimulus type is presented 8 times, and the CS+ stimulus is always combined with an electric shock (UCS). The level of the shock to be used was established during an earlier ‘shock workup’ when the shocks of increasing level were presented until the subject said reached tolerance level.


The shock workup is performed using the Stimulator test panel in SAM1 program. The ‘Increase by:’ box is set to determine incremental shock level increase, and the Shock button is repeatedly clicked so that the subject receives shocks of increasing severity. The ‘Level’ slider goes up with each shock, and the Level indicator on top of the slider shows shock level. When tolerance level is reached, the shock level is entered into the ‘parameter’ field of the Subject Details panel. This level will then be used for all shocks, when data acquisition for the Conditioning program is started.

In the extinction phase, the CS+ and CS- stimuli are similarly presented, but as with the habituation phase the UCS is absent. Each stimulus type is presented 10 times, allowing adequate opportunity for response to the UCS to extinguish.

Two SAM units are required, with SC5 and BioAmplifier on one, TG2 sound generator and SHK shocker on the other. The loudspeaker seen in the picture is not required; headphones are used for subject sound stimulation. Sound volume may be precisely calibrated if required using an artificial ear.


The picture shows required equipment; two SAM units hosting (left to right) SC5 Skin conductance amplifier, BioAmplifier for EKG, TG/WN Tone/Noise generator and SHK1 Shocker. The waves seen on the screen are produced by these devices; the top View shows EKG and SC trace. The SC trace (upper) is seen increasing in a classic SCR curve. The lower View shows traces from the stimulators; no stimulus activity is seen at the time when the picture was taken. To the right of these Views, the Stimulator Test window shows.

Two screens and two graphic cards are fitted to the computer. ‘Extend Desktop’ must be checked in Windows Control Panel, Display, Settings., which requires a Windows Professional version. When SAM1 program is run, the ‘Media view’ window is opened from the Window menu and this window is moved onto the second monitor and sized so that it fills the screen (not maximized). This monitor is positioned in front of the subject for stimulation purposes. The subject sees only the pictures, but the operator is able to see all the SAM1 control windows and physiology waves on the main computer monitor.

Two pictures (chosen from the Lang set) are copied into the C:\CPI\STIMULUS folder on the computer hard drive, and the names of these pictures is entered into positions 1 and 2 of the Media Control window in the SAM1 program. This is easily done by double clicking in the text field, when an explorer window allows each file to be chosen from the folder list.

In the PCC menu, Prompt to open PCC file., is checked and Run PCC file when acquiring., is checked.
File, Save settings now., is then used to save these settings, file names and to retain the position of the program windows.



The SAM1 program is started with physiology waveforms in Idle mode. The Conditioning PCC script file is laoded at the time when SAM1 is started.


The subject is seated; electrodes and transducers are attached. Particular care is taken to ensure that the electrodes connected to the shock generator are situated on a part of the body where electrical stimulation cannot cause harm, such as the inside of the lower arm, well away from the heart and with the two electrodes positioned closely together so that no current can flow beyond the local shock site


The manual control on the shock generator is set to zero, then adjusted to an appropriate maximum limit, perhaps 2mA. The shock workup is performed as described above, and the level transferred to the ‘Parameters’ field of the Subject Details window..

The subject is then asked to watch the Stimulus screen, told that a number of pictures will be shown, and told that shocks may or may not occur. Data acquisition is then started, using File, Open data acquisition.


The program selects between the CS+ and CS- pictures, presenting each in pseudo random order, for the required presentation time and with the pseudo random inter-stimulus-intervals. The time and category of each stimulus is registered in an event channel recorded at the same rate as physiology measures. UCS shocks are separately registered in the event channel. This event channel is used when data are analysed off-line after the recording has been made, to allow trials to be identified by CS+, CS- or CS+UCS category.

Stimuli were delivered for all three phases of the experiment, habituation, acquisition and extinction. A total of 42 stimuli were presented in all. After the last stimulus (long enough to allow analysis of any response), measurement automatically terminated, with data stored on hard disk ready for subsequent analysis.

Electrodes were removed and cleaned ready for the next experiment.

Settings for the SAM units

SAM unit with SC amplifier and BioAmplifier:
Left side: Device: SC5
No other settings required for SC5 device.

Right side: Device: Heart Rate B (BioAmplifier)
Range: 500 uV
High pass filter: 10Hz
Low pass filter: 40Hz
Hum filter:1 (on)
Parameters setting 50 (trigger threshold in range 0 - 255).

SAM unit with sound and shock stimulators:
Left side: Device: Stimulator

Right side: Device: Stimulator
No other settings are required for either of these devices.