A role for right medial prefrontal cortex in accurate feeling-of knowing judgments: evidence from patients with lesions to frontal cortex

Yushen Zhu

Introduction• Feeling of Knowing (FOK) judgements refer to feelings of

knowledge to a certain subject.

• A form of meta-memory.

• FOK Paradigm used to examine memory for semantic information and new episodic learning

Introduction Cont’d.

2 Hypotheses on how FOK works:- Accessibility View- Cue Familiarity

Questions of Researchers:How does damage to prefrontal cortex affect memory abilities, including:Do FOK impairments lead to general deficits in meta-memory?Are FOK judgements localized in a specific brain region?

Ways of Measuring FOK Accuracy

• 2 ways:• Goodman-Kruskall Gamma correlation

• Measure of “association”

• Hamann Statistic• Actually measures correlation

• Suggested that they provide distinct, but complementary information

Method• 14 patients with frontal cortex damage (10 females, 4 males)• 18 control participants (14 females, 4 males)• Mean age = 54.05 ± 8.45 • Matched in verbal IQ and age

• 24 sentences chosen out of a pool, 2 sets created• Study phase and test phase• 18 sentences asked to be read out loud and retained in study phase• 24 sentences given in test phase, whilst asking participants to guess

the last word of each sentence• Confidence ratings and FOK accuracy ratings given afterwards• Participants asked to select correct word out of 6 choices after

ratings

Results

Results Cont’d.

Results Cont’d.

Results Cont’d.• 4 patients with a FOK accuracy rating lower than the 5th

percentile of the control group• Top pictures represent regions of overlap between patients,

red being region where there is overlap in all 4• Bottom 2 diagrams represent overlap in right medial

prefrontal cortex (red region above)• a = Hamman index• b = Gamma index

Discussion• Patients with damage to prefrontal cortex exhibit impairments in

free recall and recognition• While memory plays an important role in FOK accuracy

impairment, it is not the only factor• FOK impairments is selective, did not affect confidence • Specialized in right ventromedial prefrontal cortex

• Recognition and recall accuracy were enabled when assessments were easy and rapid, but failed when assessments required additional probing

• Lateral prefrontal cortex may play a very important role in memory assessment following retrieval• Retrieval monitoring is regionalized in a part of dorsolateral prefrontal

cortex• Memory monitoring is not a unitary function

Confounds and Limitations• FOK judgements based only on incorrect answers• Small sample size

• Strengths• Good graphs• Excellent Results

• Weaknesses• Confusing statistics

My Opinion

Future Directions• Isolate other aspects of meta-memory (feeling of not knowing,

remembering vs. knowing, judgements of learning)• Practical application to increase FOK judgements -> increase in

ability to retrieve episodic memories

References• D. M. Schnyer , M. Verfaellie , M. P. Alexander , G. LaFleche , L.

Nicholls , & A. W. Kaszniak. (2004). A role for right medial prefrontal cortex in accurate feeling-of-knowing judgments: evidence from patients with lesions to frontal cortex, Neuropsychologia, 42: 957-966.

Questions?