The effect of Deep Brain Stimulation on language and cognitive abilities of Greek-speaking
individuals with Parkinson's disease
1A.
Terzi, 2V. Fyndanis, 1E. Barampati, 3C. Constantoyannis, 3 I. Ellul
1Technological Educational Institute of W. Greece, Patras, 2Univ. of Potsdam, 3Univ. of Patras
Results
Introduction
• The impact of Deep Brain Stimulation (DBS) on cognitive and language abilities
of individuals with Parkinson’s disease (PD) is not established. Moreover, the research
that has been conducted so far on language abilities in PD has focused primarily on
English.
P1’s % correct performance
100
90
80
70
• There have been claims in the literature (Hochstadt 2009) that performance on
center embedded relative clauses, if falling behind in PD, is a result of impaired executive
functions and, in particular, of set shifting (rather than of impaired grammatical knowledge).
60
P1-Preop
P1-Postop
50
40
30
• Such a claim needs confirmation. PD individuals subject to DBS provide a good
opportunity to do so, on the basis of the direction of change on language and cognitive
performance after the operation.
20
10
0
RB act
• Another area of grammar that has been found impaired in PD is past Tense
formation of regular verbs, a result of impaired grammatical rule application (Ullman et al.
1997 et seq.).
• Research on this topic has been mainly conducted on English, a morphologically
Impoverished language. In a study of Greek-speaking PD individuals, Terzi et al. (2005)
found that they performed 90% accurately.
CE act
RB pas CE pas
Past T
STM
WM
SS
Inhib
Note: In SS & Inhib, the lower the percentage the higher the performance
P2’s % correct performance
100
90
80
70
60
• The effects of DBS in such a morphologically rich language are not known, by
contrast to English, for which it was recently found that DBS affects negatively past Tense
formation of regular verbs (Phillips et al. 2012).
P2-Preop
P2-Postop
50
40
30
20
Against the above background, this study investigates the following interrelated issues:
1. the impact of DBS on cognitive and linguistic abilities of PD individuals;
2. whether comprehension of relative clauses is related to executive functions;
3. whether past Tense formation is affected by DBS.
This is the first report on an ongoing study of the linguistic and cognitive abilities of Greekspeaking PD individuals, before and after DBS.
10
0
RB act
CE act
RB pas CE pas
Past T
STM
WM
SS
Inhib
Note: In SS & Inhib, the lower the percentage the higher the performance
P3’s % correct performance
100
90
80
70
60
Methodology
Participants
• Three PD individuals have taken part in the study so far (all male, age range: 60-66).
• Participants were tested a) during the two days preceding the operation, and
b) three months after the operation, on the tasks below.
P3-Preop
P3-Postop
50
40
30
20
10
Tasks
Cognitive tasks
1. Digit forward span task (verbal short-term memory)
2. Digit ordering task (verbal working memory)
3. Plus-minus task (set-shifting)
4. Stroop task (inhibition)
Language tasks
1. Sentence-picture matching task (comprehension of relative clauses)
96 relative clauses––power point presentation––each sentence was accompanied by a
slide with 4 pictures from which the participant had to choose the one matching the
sentence they heard.
Four types of relative clauses:
a. right-branching active (N=24)
The cook follows the sailor who is tall.
b. center-embedded active (N=24)
The cook who follows the sailor is tall.
c. right-branching passive (N=24)
The cook is followed by the sailor who is tall.
d. center-embedded passive (N=24)
The cook who is followed by the tailor is tall.
2. Sentence completion task (production of past-reference verb forms).
18 sentences/real regular verbs
Participants heard a sentence that contained a verb and were instructed to complete
a following sentence with the same verb in the past tense, e.g.:
0
RB act
CE act
RB pas CE pas
Past T
STM
WM
SS
Inhib
Note: In SS & Inhib, the lower the percentage the higher the performance
RB act: Right-branching relative clauses
CE act: Center-embedded relative clauses
RB pas: Right-branching passive clauses
CE pas: Center-embedded passive clauses
Past T: Past Tense
STM: Short Term Memory
WM: (verbal) Working Memory
SS: Set-Shifting
Inhib: Inhibition
Summary of results & Discussion
• After DBS, all three PD participants performed significantly better on the stroop task
(which tapped inhibition).
• The impact of DBS on short-term memory and set-shifting is not clear, as results are
mixed. After DBS, working memory was improved in all three participants, but the
difference was not significant.
• Only one of the three PD participants, P3, benefited from DBS on relative clauses,
with statistically significant improvement on the passive right-branching.
• DBS seems to enhance PD individuals’ inhibition and WM capacity, which may lead to
improvement in language performance when the linguistic task involves syntactic
complexity (of the type involved in the relative clauses).
• Past Tense formation remained invariant (contrary to Phillips et al. 2012, for English).
The boy opens the window. > Yesterday, suddenly, the boy ___ the window.
(Target): opened
• These preliminary results suggest that DBS does not affect cognitive functions and
language abilities in opposite directions, neither does it affect rule application negatively
in a morphologically rich language such as Greek.
References
Contact Info:
aterzi@teipat.gr
This research has been co-financed by the European Union (European Social Fund - ESF) and Greek
national funds through the Operational Program "Education and Lifelong Learning" of the National
Strategic Reference Framework (NSRF) - Research Funding Program: ARCHIMEDES III. Investing in
knowledge society through the European Social Fund.
1. Hochstadt, J. (2009) Set-shifting and the on-line processing of relative clauses in
Parkinson’s disease: Results from a novel eye-tracking method. Cortex 45: 991-1011.
2. Phillips, L., K. Litcofsky, M. Pelster, M. Gelfald, M.T. Ullman, & P.D. Charles (2012)
Subthalamic Nuvleus Deep Brain Stimulation Impacts Language in Early Parkinson’s
Disease. PloS One 7: e42829.
3. Terzi, A, S. Papapetropoulos, & E. D. Kouvelas (2005) Past tense formation and
comprehension of passives sentences in Parkinson’s disease: Evidence from Greek. Brain
and Language 94: 297-303.
4. Ullman, M., S. Corkin, M. Coppola, G. Hickok, J.H. Growdon, W. Koroshetz, & S. Pinker
(1997) A neural dissociation within language: Evidence that the mental dictionary is part of
declarative memory, and that grammatical rules are processed by the procedural system.
Journal of Cognitive Neuroscience 9: 289-299.
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