Effects of Arousal and Stress on Classical Conditioning

Correct-go Reaction Time (RT)

时间窗: 2000 ms during trial

Correct go responses were go trials followed by button press. Mean reaction time (RT) was calculated for correct-go to evaluate speed-accuracy trade-off.

Nogo Trials Followed by no Button Press

时间窗: 250 ms at a rate of one every 2000 ms

Subjects participated in go/no go (GNG) task condition during periods of threat of shocks and periods of safety when no shock could be administered. During the GNG stimuli were presented on a monitor. In the GNG task, participants were asked to respond to frequent 'go' stimuli ('=') by pressing the '2' on the keypad of a computer keyboard and to withhold their response to infrequent 'nogo' stimuli ('O'). Stimuli were randomly distributed. A correct go hit was a response recorded during these 2000 millisecond (ms) to a go trial. Similarly, a correct nogo omission was a no response during the same period to a nogo trial. Performance was determined for each condition (threat, safe) and trial type (go, nogo) by dividing the number of correct response by the total number of each trial type.

Response to Startle Reflex

时间窗: 20-100 ms window following the onset of the startle stimulus

The startle reflex was elicited with a 103-decibel (dB) white noise (40-ms duration) delivered via headphone. The eyeblink component of the startle reflex was recorded binaurally with two AgCl electrodes placed under the left eye. The peak startle/eyeblink reflex magnitude was determined in the 20-100 ms timeframe. The shock was administered either on the left wrist or on the left middle and ring fingers, depending on where the desired intensity was reached. Startle stimuli were delivered between two go trials and go trials that followed a startle stimulus were not included in the analysis. A shock was delivered in two of the four threat blocks in each sequence, just prior to the last go trial, which was not included in the analysis (for a total of 4 shocks). Shock could be administered only in the threat condition and never in the safe condition. The results were analyzed using a Condition (safe, threat) x Task (task, no task) repeated ANOVA.

Go Correct Hits Followed by Button Press

时间窗: 250 ms at a rate of one every 2000 ms

Subjects participated in go/no go (GNG) task condition during periods of threat of shocks and periods of safety when no shock could be administered. During the GNG stimuli were presented on a monitor. In the GNG task, participants were asked to respond to frequent 'go' stimuli ('=') by pressing the '2' on the keypad of a computer keyboard and to withhold their response to infrequent 'nogo' stimuli ('O'). Stimuli were randomly distributed. A correct go hit was a response recorded during these 2000 millisecond (ms) to a go trial. Similarly, a correct nogo omission was a no response during the same period to a nogo trial. Performance was determined for each condition (threat, safe) and trial type (go, nogo) by dividing the number of correct response by the total number of each trial type.

Subjective Measures of Level of Anxiety

时间窗: Every 100 sec repeated 8 times

Subjects retrospectively rated their level of anxiety using a scale of 1-10 where 1 = "not at all anxious" and 10 = "extremely anxious" at the end of each block of a sequence for a total of eight blocks. A block was defined as a combination of a condition (safe or threat) and a task (task or no task). The results were analyzed using a Condition (safe, threat) x Task (task, no task) repeated ANOVA.