Executive RT Test

The Executive Reaction Time (RT) Test is a Go/No-go test tapping into working memory, response inhibition, emotional interference and task switching (Hartikainen et al., 2010). In the Executive RT Test subject is required to respond to a visual stimulus, a triangle pointing up or down, by pressing one of the two keys on the response pad according to the orientation of the triangle (Go condition) or by not responding at all (No-go condition). The orientation of the triangle is randomized within each block. Go/No-go condition i.e., whether the subjects should respond or withhold from responding, is indicated by a green or a red traffic light. The rule for responding changes between each block i.e., whether green or red light indicates a Go condition and vice versa. There were four Green-Go Red-No-go and four Red-Go Green No-go blocks, totaling into 512 trials. In the centermost circle of the traffic light there is an emotional distractor i.e., black line drawing of a spider, a biologically relevant threat stimulus (Öhman et al., 2001), or an emotionally neutral control figure composed of the exact same line elements but in a different configuration resembling a flower. A trial begins with a triangle presented in the middle of the screen for 150 ms, followed by the fixation cross for 150 ms and by the traffic light 150 ms. One trial last approximately 2000 ms and subject has approximately 1550 ms to respond. There is a 150 ms jitter associated with the onset of the trial to prevent subjects from synchronizing their responding to the rhythm of stimulus presentation (Figure ​(Figure11).

The triangle is presented in the middle of the screen for 150 ms. The color of the traffic light indicates whether the subject is required to press (Go signal) one of the two buttons according to the orientation of the triangle or to withhold from responding (No-go signal). Emotionally neutral or threatening distractor is shown in the centermost circle of the traffic light.

The Executive RT Test performance measures include RT of the correct button presses and errors made. There are three basic types of errors: incorrect responses, missing responses and commission errors. In a go trial subject can make an incorrect response, i.e., press a wrong button, or miss responding, reflecting lapses in working memory and attention correspondingly. A commission error, i.e., a key press in a No-go trial, reflects failure in response inhibition. Basic errors are summed up as total errors indexing executive function performance in general.

The tests were conducted at the Behavioral Neurology Research Unit, Tampere University Hospital, Finland. The recording room was sound-attenuated, and the ceiling lights of the room were dimmed. The subjects sat at one-meter distance from a 21-inch screen, equipped with a response pad (Cedrus RB-840, Cedrus Corporation, San Pedro, CA, United States) with dedicated keys for each finger. Before starting the test, subjects practiced responding so that they felt confident in executing the test and researcher ensured that the subject learned to do the test. Typically, one practice block was enough to reach confidence. Subjects were instructed to respond as quickly and accurately as possible. The Executive RT Test utilizes Presentation software (Neurobehavioral systems, Inc., Berkeley, CA, United States) to present the stimuli and to register the performance of the subject.