Transcript A role for right medial prefrontal cortex in accurate

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
My Opinion
• Strengths
• Good graphs
• Excellent Results
• Weaknesses
• Confusing statistics
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?