Rule induction performance in amnestic mild cognitive impairment and Alzheimer's dementia: examining the role of simple and biconditional rule learning processes.
BACKGROUND
Rule induction tests such as the Wisconsin Card Sorting Test require executive control processes, but also the learning and memorization of simple stimulus-response rules. In this study, we examined the contribution of diminished learning and memorization of simple rules to complex rule induction test performance in patients with amnestic mild cognitive impairment (aMCI) or Alzheimer's dementia (AD).


METHODS
Twenty-six aMCI patients, 39 AD patients, and 32 control participants were included. A task was used in which the memory load and the complexity of the rules were independently manipulated. This task consisted of three conditions: a simple two-rule learning condition (Condition 1), a simple four-rule learning condition (inducing an increase in memory load, Condition 2), and a complex biconditional four-rule learning condition-inducing an increase in complexity and, hence, executive control load (Condition 3).


RESULTS
Performance of AD patients declined disproportionately when the number of simple rules that had to be memorized increased (from Condition 1 to 2). An additional increment in complexity (from Condition 2 to 3) did not, however, disproportionately affect performance of the patients. Performance of the aMCI patients did not differ from that of the control participants. In the patient group, correlation analysis showed that memory performance correlated with Condition 1 performance, whereas executive task performance correlated with Condition 2 performance.


CONCLUSIONS
These results indicate that the reduced learning and memorization of underlying task rules explains a significant part of the diminished complex rule induction performance commonly reported in AD, although results from the correlation analysis suggest involvement of executive control functions as well. Taken together, these findings suggest that care is needed when interpreting rule induction task performance in terms of executive function deficits in these patients.
a Donders Institute for Brain, Cognition and Behaviour , Radboud University , Nijmegen , The Netherlands.
Joukje M
JM
Oosterman
b Department of Psychiatry, Brain Center Rudolf Magnus , University Medical Center , Utrecht , the Netherlands.
Sophie M
SM
Heringa
a Donders Institute for Brain, Cognition and Behaviour , Radboud University , Nijmegen , The Netherlands.|c Department of Medical Psychology & Radboudumc Alzheimer Center , Radboud University Medical Center , Nijmegen , the Netherlands.
Roy P C
RP
Kessels
d Department of Neurology, Brain Center Rudolf Magnus , University Medical Center , Utrecht , the Netherlands.
Geert Jan
GJ
Biessels
e Department of Geriatrics , University Medical Center Utrecht , Utrecht , the Netherlands.
Huiberdina L
HL
Koek
a Donders Institute for Brain, Cognition and Behaviour , Radboud University , Nijmegen , The Netherlands.
Joseph H R
JH
Maes
d Department of Neurology, Brain Center Rudolf Magnus , University Medical Center , Utrecht , the Netherlands.|f Experimental Psychology , Utrecht University , Utrecht , The Netherlands.|g Department of Neurology , Erasmus Medical Center , Rotterdam , The Netherlands.
Esther
E
van den Berg
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000523:psychology*; D000647:Amnesia / Q000523:psychology*; D060825:Cognitive Dysfunction / Q000523:psychology*; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology; D009483:Neuropsychological Tests; D013647:Task Performance and Analysis
Dementia; Executive function; Mild cognitive impairment; Rule induction; Stimulus-response learning