Cognitive Functions Assessment
Methods
An extensive neuropsychological assessment was administered in order to encompass the
cognitive domains that are sensitive to dysfunction in PD.
Overall cognitive status was assessed in terms of the score on the Mattis dementia rating scale
(DRS, Mattis, 1976)
Memory was assessed using (i) the forward and backward digit span and (ii) the French
version of the Grober and Buschke 16-item free/cued word learning and recall test (Van der
Linden et al., 2004). Performance was assessed in terms of the number of words (out of 16)
immediately recalled at learning, the total number of words (out of 48) correctly recalled after
the three free recall trials and the total number of words (out of 48) correctly recalled after the
three free and cued recall trials.
Attention and executive functions were assessed using:
- An oral version of the Symbol Digit Modalities test (Smith, 1982). Subjects were instructed
to associate symbols with digits according to a key code. Performance was evaluated in terms
of the number of correct responses given in 90 sec.
- A 50-item version of the Stroop word color test (to assess response inhibition). The
procedure has been described fully elsewhere (Dujardin et al., 2001). Performance was
evaluated in terms of the time needed to complete the test's two phases (naming the color of
dots and color names, respectively) and the number of errors in the interference phase (phase
2).
- A letter and number sequencing task, corresponding to an oral version of the Trail Making
Test (to assess set shifting) (Dujardin et al., 2001). Performance was evaluated in terms of the
time needed to complete the test's two phases (baseline and alternation, respectively) and the
number of errors in the alternation phase.
- A word generation task performed over 60 sec and in three conditions (to assess action
initiation and working memory updating), i.e. phonemic (letter P), semantic (animals) and
alternating (letter T and V, alternatively) conditions.
Results
Table 1 shows the mean (SD) results of both groups at the extensive neuropsychological
assessment. Group comparisons revealed no significant difference, except that PD patients
took significantly more time to complete the Symbol Digit Modalities test and the alternation
phase of the letter and number sequencing task.
Table 1: Mean (SD) results of both groups at the extensive cognitive assessment. Group comparisons were performed using non parametric
Mann-Whitney tests. P values below 0.05 were considered to be statistically significant.
PD patients
Healthy
Controls
p value (MannWhitney)
141.3 (2.7)
142.1 (1.6)
0.642
Forward Digit span
6.3 (1.3)
6.3 (1)
0.983
Backward Digit span
4.9 (1.8)
4.1 (1.1)
0.144
16-item free/cued word learning and recall test: immediate recall (/16)
15.5 0.9)
15.9 (0.4)
0.312
16-item free/cued word learning and recall test:Total Free Recall (/48)
32.1 (4.3)
31.3 (3.1)
0.63
16-item free/cued word learning and recall test:Total Free + Cued Recall (/48)
47.4 (0.9)
46.8 (1.6)
0.327
46.7 (10.8)
53.3 (4.8)
0.027
Stroop word/color test: time to complete phase 1 (sec)
33.5 (4.2)
32.2 (5.1)
0.466
Stroop word/color test: time to complete phase 2 (sec)
54.7 (12.4)
52 (9.8)
0.455
1 (1.6)
1.6 (1.5)
0.187
Letter/Number sequencing: time to complete phase A (sec)
16.2 (11.9)
9.3 (3.2)
0.114
Letter/Number sequencing: time to complete phase B (sec)
34.2 (16.2)
22.2 (4.9)
0.024
0.3 (0.7)
0.2 (0.4)
0.858
Word generation task (60 sec): letter "P"
14.8 (5.2)
16 (3.8)
0.279
Word generation task (60 sec): Animals
21.1 (4.2)
22.9 (6.2)
0.204
Word generation task (60 sec): Alternating "T"/"V"
12.1 (4.2)
13.9 (3.8)
0.26
Tasks
Mattis dementia rating scale (/144)
Symbol Digit Modalities test (number of correct responses)
Stroop word/color test: number of error in phase 2
Letter/Number sequencing: errors
REFERENCES
Mattis S. Mental status examination for organic mental syndrome in the elderly patient. In:
Bellak L, Karasy T, eds. Geriatric Psychiatry. New York: Grune and Stratton, 1976:77-121.
Van der Linden M, Coyette F, Poitrenaud J, et al. L'épreuve de rappel libre/rappel indicé à 16
items (RL/RI-16). In: Van der Linden M, GREMEM, eds. L'évaluation des troubles de la
mémoire. Marseille: Solal, 2004:25-47.
Smith A. Symbol Digit Modalities Test (SDMT): Western Psychological Services, 1982.
Dujardin K, Defebvre L, Grunberg C, Becquet E, Destee A. Memory and executive function
in sporadic and familial Parkinson's disease. Brain 2001;124(Pt 2):389-398.