Polyunsaturated Fatty Acids (PUFA) Status and Cognitive Function in Healthy Young Adults

Simple Reaction Time (Attention)

The participant was instructed to press the 'space bar' on the laptop keyboard as quickly as possible every time an upwards pointing arrow appeared on screen. Fifty stimuli were presented with an inter-stimulus duration that varied randomly between 1 and 3.5 seconds.

Time frame: Single visit

Choice Reaction Time (Attention)

An arrow appeared on the screen pointing to the left or to the right. Participants responded with a left or right key press corresponding to the direction of the arrow. There was a randomly varying inter-stimulus interval of between 1 and 3 seconds for a total of fifty stimuli.

Time frame: Single visit

Four Choice Reaction Time (Attention)

A visual representation of the four direction arrow keys of a standard keyboard was presented on screen. The arrows 'lit up' at random on screen until the corresponding key press was made. In all, each arrow was the target stimulus 12 times, forming a total of 48 stimuli for this task in all.

Time frame: Single visit

Numeric Working Memory (Working Memory)

Time frame: Single visit

Alphabetic Working Memory (Working Memory)

Five random letters (A-Z) were presented sequentially for the participant to hold in memory. This was followed by a series of 30 probe digits (15 targets and 15 distractors) for each of which the participant indicated whether or not it had been in the original series by a simple key press. The task consisted of 3 separate trials.

Time frame: Single visit

Corsi Blocks Span (Spatial Working Memory)

In this task nine identical blue squares appeared on screen in non-overlapping random positions. A set number of blocks changed colour from blue to red in a randomly generated sequence. Participants were instructed to repeat the sequence by clicking on the blocks using the mouse and cursor. The task was repeated five times at each level of difficulty. The sequence span increased from 4, until the participant could no longer correctly recall the sequence, resulting in a span measure of nonverbal working memory, calculated by averaging the level of the last five correctly completed trials.

Time frame: Single visit

3-back Task (Working Memory)

A continuous string of letters (upper and lower case; inter-stimulus interval of 2.5 seconds) was presented; 45 letters in total with 15 target pairs. For each stimulus, participants were instructed to indicate whether this was the same letter that appeared three letters before.

Time frame: Single visit

Immediate Word Recall (Episodic Memory)

A unique set of fifteen words is presented. Words were selected at random from a large bank of words derived from the MRC Psycholinguistic Database matched for word length, frequency, familiarity and concreteness. Stimulus duration was one second, as was the inter-stimulus duration. Following word presentation, the participant was allowed 60 seconds to write down as many of the words as possible.

Time frame: Single visit

Delayed Word Recall (Episodic Memory)

The participant was again given 60 seconds to write down as many of the words presented previously as possible.

Time frame: Single visit

Word Recognition (Episodic Memory)

The original 15 words plus 15 distractor words were presented one at a time in a random order. For each word the participant indicated whether or not it was included in the original list of words by pressing appropriate 'yes' and 'no' keys as quickly as possible. Stimuli remained on screen until an appropriate response had been made.

Time frame: Single visit