CNP RK

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Basic Task Description

The Remember-Know (RK) task is intended to probe episodic memory, which we conceptualize as involving an information encoding phase during which stimulus features are bound into a unified mental representation and a recognition phase during which that representation is retrieved and judgments are made about that retrieval process.

Taking a cognitive neuroscience perspective, retrieval has been modeled various ways, including the approach that provided the basis for the RK task. This approach employs a distinction between recollection-based retrieval and familiarity-based retrieval. Recollection is thought to rely to a great extent on hippocampal activity inasmuch as the stimulus features that the hippocampus binds together at encoding are recalled (Eldridge et al., 2000). Retrieval involving a sense of familiarity is believed to rely on distributed temporal, parietal, and frontal lobe structures. Although familiarity-based retrieval is thought to rely on a memory cue (i.e., test word), it does not necessarily involve the recall of a bound stimulus representation (including non-cued details; Henson et al., 1999). Accordingly, during the test portion of the RK task, participants are asked to make a meta-cognitive judgment regarding whether words labeled as "old" or "studied" were recognized using recollection (or "remember") or a familiarity-based (or "know") process (Tulving, 1985).

From a behavioral standpoint, patients diagnosed with schizophrenia (e.g., van Erp et al., 2008), bipolar disorder (e.g., Kurtz and Gerraty, 2009), and ADHD (e.g., Castel et al., 2011), all show evidence of disrupted episodic memory functioning, although the nature and severity of these impairments may differ. Furthermore, behavioral performance on tests thought to assess episodic memory ability has been shown to be at least moderately heritable (e.g., Finkel and McGue, 1993), with a number of gene variants identified as promising leads in helping to account for variability in performance (Bearden et al., 2012).

Task Procedure

The RK test procedure is comprised of four phases (implemented as three E-Prime programs, indicated below).

First, participants receive instruction on the conceptual distinction between “remembering” and “knowing” processes of stimulus recognition. They then answer a series of questions in order to demonstrate that they understand the concepts adequately. This first phase is referred to as the pretest.

The second phase of the RK task is the encoding phase, during which participants see pairs of words (and congruent images) and indicate which of the two words is presented in all capital letters (also presented with a color picture). Subjects also know at this point that there will be a memory test next.

The third phase is the recognition test, in which words are presented, and participants are asked to indicate whether they remember that the words were presented during the encoding phase, whether they know that the words were presented during encoding, or whether the word is new, or not presented at encoding.

Finally, during a validation phase, participants are presented with a set of words and images, and must indicate which word was paired with the presented word (or whether it was new at recognition) and then what the color of the presented image was during encoding (or whether it was new).

Sample Text Describing the Procedure (from van Erp et al., 2008b):

The R–K paradigm was administered on a personal computer using E-Prime (Psychology Software Tools,www.pstnet.com). Stimuli were presented as word and picture pairs in order to provide opportunities for use of relational information at encoding …. The paradigm comprised three phases: 1) encoding, 2) item recognition, and 3) stimulus feature recognition. Before the task began, participants were instructed to remember as much of the information presented on each trial as possible and were given examples of the types of questions that would be asked in the item and stimulus feature recognition phases. The explanation of “remember” and “know” responses was based on those by Gardiner and Java (1990), and those with regard to the stimulus feature recognition resembled those by Dudukovic and Knowlton (2006). As a pre-test measure, participants were given six example sentences describing memories and asked whether each was reflective of a “remember” or a “know” memory.

During the encoding phase, participants were shown sixty stimulus pairs, and explicitly asked to memorize as much about the items on the screen as possible: the words, pictures, colors of the pictures, and their location on the screen; they were also encouraged to develop other associations. As a check on task engagement, participants were asked to judge whether the colored target picture appeared on the left or right. During the item recognition phase, immediately following encoding, subjects were presented with the sixty previously presented targets and twenty new foil words. Participants were instructed to press one of three keys according to whether they remembered the word and could recall specific additional information presented with the word [“remember”], knew that the word was previously presented, but did not recall additional information [“know”], or thought the word was not previously presented [“unstudied”]. Immediately following the item recognition phase, subjects were given the feature recognition phase, in which they were first presented with a target word and asked to make a forced-choice recognition judgment between two possible paired words. A grayscale target picture was then presented and subjects were asked to make a forced-choice recognition judgment between two possible picture colors. Both judgments also offered the ‘unstudied’ option to indicate that the word or picture was not present in the encoding phase. The feature recognition phase was self-paced.”

Task Structure Detail

The RK task involves three E-Prime programs, including four task phases. The procedures included in the three programs are outlined below:


RKpretest (3-5 min)

Pretest Phase Instructions

Pretest Phase Questions


RKpart1 (17 min)

Encoding Phase Instructions

Encoding Phase Practice Trials – 2 trials

Recognition Phase Instructions

Recognition Phase Practice Trials – 3 trials

Encoding Task (Right-Left Judgment re. Capitalized Letters)

Recognition Phase Instructions Reminder

Recognition Task (3-Choice Word Recognition Trials)


RKpart2 (14 min)

Validation Phase Instructions

Validation Phase Practice Trials – 2 trials

Validation Phase Task (3-Choice, 2 options and “new”)

Task Schematic

Task Parameters Table

Stimuli

Dependent Variables

Cleaning Rules

Code/Algorithms

Data Distributions

References

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