Use case Lauwereyns et al 2002

• Lauwereyns, J., et al., A neural correlate of response bias in monkey caudate nucleus. Nature, 2002. 418(6896): p. 413-417.
• Reference can be found here.
• This use case was created to explore how space and time can be encoded.
• Same use case as the JBMS paper:
• Short description (from JBMS paper): This investigation studied the role of the primate caudate nucleus in the expectation of reward following action [Lauweyrens et al., 2002]. While the caudate nucleus responds preferentially to eye movements in different directions, the response begins prior to eye movement and is dramatically increased when there is expectation of reward for the preferred direction. Here we represent a single trial in which the visual target, a light, is presented to the animal and the neural response is recorded as data.
• Those classes and relations not in OBI (19 May 2010) have a gray background.

Description of the BST condition

This use case will use the BST experiment as reported in the paper. The BST consists of two conditions (see figure), where the difference between these conditions is simply the position of the reward stimulus.

• condition 1, the reward is given to the subject when there is a right cue and the subject makes a right saccade. In this first condition, no reward is given to the subject when the cue is on the left and a correct left saccade is made.
• condition 2: reward with left cue, no reward with right cue

The entire use case here is based on this BST experiment, describing the stimulus, subject/environment and time/sequence.

Stimulus Left Cue

In this section I would like to describe an example of the spatial features I need to describe the various stimuli in cognitive neuroscience.

Description of the stimulus in the article:

• Visual stimuli were small red spots, 0.2° in diameter, back-projected onto a tangent screen by LED projectors. (p. 416)

The stimulus is used in both conditions as a target/cue for the subject. I'm looking on how to represent the stimulus for this use case in relation with:

• the subject: being in front of the subject in an angle of 20°
• the central fixation point: the fixation point at that time is not present, my guess being that this relation does not have to be represented.
• the tangent screen: in fact the stimulus is only present to its projection on the tangent screen. Without the stimulus would not be presented, at least not at that position.

Diagram

The diagram shows that the DOT as project_by the LED projector (projects_on the tangent screen), is a dot which is left_side_of' the central fixation dot (as projected on the tangent screen) with a 20° angle. The diameter of the dot is 0.2° wide and has the color red.

Subject and Stimuli/Environment

Will be added once other diagrams are resolved.

Time/Sequence of Condition 1 (CST)

About the diagram

The condition BST (figure 'BST simplified') is in essence a rather straightforward condition. As previously mentioned, condition 1 of the BST has two options:

• a left target/cue appears and the subject has to make a saccade to the left. There is no reward.
• a right target/cut appears and the subject has to make a saccade to the right. There is no reward.

The figure is an example of such a sequence where initially the left cue is present (trial A), followed by a right cue/target (trial B), followed by a left cue (trial C), then again a left cue (trial D), followed by...

There are a total of 20 up to 40 trials repeated for the condition.

Description in article:

In the BST, the monkey was required to direct and maintain his gaze at a central fixation spot during a first fixation (‘pre-target’) period of 1.5 s. Visual stimuli were small red spots, 0.2° in diameter, back-projected onto a tangent screen by LED projectors. After the pre-target period, the fixation spot disappeared and a peripheral target appeared at 20° to the left or to the right. The monkey had to make a saccade within 500 ms to within 38 from the target position. A beep was presented as feedback for each correct trial. If the monkey made an error, the same trial was repeated. In half of the correct trials the monkey was rewarded with a drop of water depending on the reward schedule. During blocks of 20 or 40 correct trials, reward was mapped consistently onto one target position. We reversed the position reward contingency automatically (6–16 times) without any indication to the monkey. (p. 416-417)

Diagram: full description

• Concerns Condition 1 of the BST paradigm (see description above and p. 414 figure 1a in paper). When a left stimulus is presented the subject is not rewarded with juice, when a right stimulus occurs (and subject makes correct saccade) the subject receives a reward.
• A single trial consists of 3 blocks in the experimental design (1, 2 and 3 in figure):

1. 'resting phase' where subject is awaiting a new trial

2. 'fixation': subject has to fixate the central dot

3. 'saccade': central fixation stimulus disappears, subject is presented a peripheral stimulus (left/right of central fixation), subject has to make a saccade within 500ms

• Each trial is repeated for 20 or 40 correct correct trials (in figure '1 sequence of trials with identical reward scheme').
• After 20-40 correct trials the reward scheme is reversed (in figure lower '1 sequence of trials with identical reward scheme') 6-16 times (randomly).
• Condition 2 differs from condition 1 for its reward (reward on left stimulus, no reward on right stimulus).