N-Back Task

N-Back task experiment for Presentation® NeuroBehavioral Systems, This tasks are created for the Cystinosis experiment battery (2021). There are 2 Visual versions (1 verbal and 1 non-verbal) and 1 auditory version.

Table of Contents

1. About the project
2. Getting started
   • Presentation settings
3. Info about the paradigm
4. Piloting Results (EEG)
5. Contact
6. Acknowledgement

About The Project

This Project has 3 different N-back tasks each designed to touch a different aspect of the working memory. 2 of them are Visual and 1 is auditory.

1. Visual-verbal

   • For this experiment, participants will see a letter and have to do the N back task based on this.
   • This experiment has eyetracking.

2. Visual-non-verbal

   • For this experiment, participant will see a square and have to do the N-back task based on the location
   • This experiment has eyetracking.

3. Auditory

   • For this experiment, participant will hear letter being said out loud and have to do the N back task based on this.

Getting Started

There is only 1 sequence file if you download this repo. Use the matlab script to create more and change the presentation code (line 8 and 9 in each of the PCL files). This is done so there are not an extra 100 files per paradigm. When using the paradigm you need these 100 sequences to make sure that everyone's paradigm is not following the same sequence.

#string file_path = direc + "sequences//" + printf(random(1,100),"n-back_sequence_%d.txt");
string file_path = direc + "sequences//" + printf(1,"n-back_sequence_%d.txt");

Need to be

string file_path = direc + "sequences//" + printf(random(1,100),"n-back_sequence_%d.txt");
#string file_path = direc + "sequences//" + printf(1,"n-back_sequence_%d.txt");

Like this it will choose randomly between the 100 sequence files. These files are all semi random with the rule that there are always at least 2 no-target trails between targets. It also makes sure that 80% of the trials are non-target trials

Presentation settings

Info about the paradigm

Stimuli

1. Visual-verbal The stimuli are letter that presentation creates each time. This has a 2ms effect on the timing (see Timing), that we correct for.

2. Visual-non-verbal The stimuli are made in paint. They have a 7ms effect on the timing (as any picture that needs to be loaded does). See Timing for more info.

3. Auditory The stimuli are recorded in the lab by Ana Francisco and voiced by Alaina Berruti (lab member). They are cut in length so that the onset in of the stimulus in presentation is also the exect time the letter's sound start. THe do have different durations, this is why we have the trial lasting longer than the longest sound.

Logfiles

Logfiles with experiment reaction times and other information automatically should be placed in the logfile folder. In these logfiles you will find the behavioral information of each time the experiment is ran.

Sequences

In the Presentation Files folder you'll find the experiment and the sequences that are semi-randomized, so we are sure that there are no 2 target trials in a row and how many trials there are. These sequences are made so that there are always non-target trials before a target trial.

Instructions

For any of the instructions to make sense, put a blue sticker on the left Ctrl and a yellow sticker on the right control. These are the buttons people will respond with.

1. Visual-verbal

   • For this experiment, participants will see a letter and have to do the N back task based on this.
     • 0-back = Press the BLUE key when you see the letter X. Press the YELLOW key when you see any other letter.
     • 1-back = Press the BLUE key when you see the same letter twice in a row. Press the YELLOW key when you see any other letter.
     • 2-back = Press the BLUE key if the letter you see appeared two times ago. Press the YELLOW key when you see any other letter.

2. Visual-non-verbal

   • For this experiment, participant will see a square and have to do the N-back task based on the location
     • 0-back = Press the BLUE key when you see the square in the left top corner. Press the YELLOW key when you see the square anywhere else.
     • 1-back = Press the BLUE key when you see the square in the same place twice in a row. Press the YELLOW key when you see the square anywhere else.
     • 2-back = Press the BLUE key if the you see the square in the same place where it appeared two times ago. Press the YELLOW key when you see the square anywhere else.

3. Auditory

   • For this experiment, participant will hear letter being said out loud
     • 0-back = Press the BLUE key when you hear the letter X. Press the YELLOW key when you hear any other letter.
     • 1-back = Press the BLUE key when you hear the same letter twice in a row. Press the YELLOW key when you hear any other letter.
     • 2-back = Press the BLUE key if the letter you hear was said two times ago. Press the YELLOW key when you hear any other letter.

Trigger codes

port_code=11; #0-back Non-Target
port_code=21; #1-back Non-Target
port_code=31; #2-back Non-Target
port_code=12; #0-back Target
port_code=22; #1-back Target
port_code=32; #2-back Target
port_code=1;  # Left - ctrl (After perceiving target)
port_code=2;  # Right- ctrl (After perceiving Non-target)
port_code=201;# to auto-start saving (biosemi)
port_code=200;# to auto-pause saving (biosemi)

Timing

Auditory N-back

Having measured the time between the stimuli and the trigger with an oscilosscope we see a 1ms delay between the onset of any stimulus and the trigger. The trial consists of the sound of a letter for a total of 1000ms. Due to the nature of spoken stimuli the duration of the leters themselves are different. But each trial takes 1000ms in total.

Visual Non-Verbal

Having measured the time between the stimuli and the trigger with an oscilosscope we see a 0ms delay between the onset of any stimulus and the trigger. This is because we delay the trigger by 7ms (this is the time the video card need to produce the visual stimulus). Each trial starts with the presentation of the stimulus for 500ms followed by an ISI trial of 500ms. The ISI trial is a picture of only the fixation cross. Because of refresh rates speeds the trials have different times in the code. This is because they are corrected for Adult booth Right.

It is clear that the onset of the trigger (orange) always is at the same time as where the visual stimulus (blue) changes from the norm.

Visual Verbal

Having measured the time between the stimuli and the trigger with an oscilosscope we see a 0ms delay between the onset of any stimulus and the trigger. This is because we delay the trigger by 2ms (this is the time the video card need to produce the letters, this is a little unusual because all visual stimuli normally have a 7ms delay. This difference (5ms) is likely caused by not using a picture but presentation making the letters). Each trial starts with the presentation of the stimulus for 500ms followed by an ISI trial of 500ms. The ISI trial only has target and not target written in the bottom of the screen. Because of refresh rates speeds the trials have different times in the code. This is because they are corrected for Adult booth Right.

It is clear that the onset of the trigger (orange) always is at the same time as where the visual stimulus (blue) changes from the norm.

Piloting Results (EEG)

We have collected data from 4 control participants and averaged their data. The data shown here is of the CPz channel and is shows the different difficulties plotted separtatly. It is clear that the data indeed shows a difference in the time window we expected (P3) and changes depending based on difficulty.

Auditory verbal

Visual verbal

Visual non-verbal

Contact

Douwe Horsthuis - @douwejhorsthuis - [email protected]

Project Link: https://github.com/DouweHorsthuis/N-back-task-experiment/

Acknowledgements

• Ana Francisco - The Research Assistant Professor that conceptualized the experiment