Abnormal sensorimotor integration correlates with cognitive profile in vascular parkinsonism

Accepted Manuscript Abnormal sensorimotor integration correlates with cognitive profile in vascular parkinsonism

Sonia Benítez-Rivero, Francisco J. Palomar, Juan F. MartínRodríguez, Paloma Álvarez de Toledo, María J. Lama, Ismael Huertas-Fernández, María T. Cáceres-Redondo, Paolo Porcacchia, Pablo Mir PII: DOI: Reference:

S0022-510X(17)30218-6 doi: 10.1016/j.jns.2017.03.050 JNS 15250

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Journal of the Neurological Sciences

Received date: Revised date: Accepted date:

9 August 2016 6 March 2017 29 March 2017

Please cite this article as: Sonia Benítez-Rivero, Francisco J. Palomar, Juan F. MartínRodríguez, Paloma Álvarez de Toledo, María J. Lama, Ismael Huertas-Fernández, María T. Cáceres-Redondo, Paolo Porcacchia, Pablo Mir , Abnormal sensorimotor integration correlates with cognitive profile in vascular parkinsonism. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Jns(2017), doi: 10.1016/j.jns.2017.03.050

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ACCEPTED MANUSCRIPT Abnormal sensorimotor integration correlates with cognitive profile in vascular parkinsonism Sonia Benítez-Rivero1 MD, PhD; Francisco J. Palomar1,2 MD, PhD; Juan F. MartínRodríguez1 PhD; Paloma Álvarez de Toledo1 BSc; María J. Lama1 MSc; Ismael HuertasFernández1 MSc; María T. Cáceres-Redondo1 MD; Paolo Porcacchia1 MD; Pablo Mir1,2

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MD, PhD.

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1. Unidad de Trastornos del Movimiento, Servicio de Neurología y Neurofisiología Clínica, Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del

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Rocío/CSIC/Universidad de Sevilla, Seville, Spain.

2. Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas

Corresponding author:

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(CIBERNED), Spain.

Pablo Mir. Unidad de Trastornos del Movimiento. Servicio de Neurología y

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Neurofisiología Clínica. Hospital Universitario Virgen del Rocío. Avda. Manuel Siurot s/n. 41013 Seville, Spain. Tel.:(+34) 955923039. Fax:(+34) 955923101. E-mail:

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[email protected].

ACCEPTED MANUSCRIPT ABSTRACT Introduction: Vascular parkinsonism is a syndrome that develops as a result of cerebrovascular disease. Although several studies on clinical features and neuroimaging have been published, little is known about its pathophysiology. Our aim was to study sensorimotor integration using transcranial magnetic stimulation in this condition and to correlate the potential abnormalities in this technique with the cognitive profile of these

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patients.

Methods: We studied 11 vascular parkinsonism patients and 13 controls. We applied

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transcranial magnetic stimulation to investigate sensorimotor inhibition and sensorimotor

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plasticity and we performed extensive neuropsychological examinations.

Results: Vascular parkinsonism patients showed reduced short latency afferent

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inhibition and lack of long term potentiation-like plasticity after paired associative stimulation protocol. Correlations were found in these patients between short latency afferent inhibition and sensorimotor plasticity with verbal memory tests.

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Conclusions: Our neurophysiological findings suggest deficiencies of a variety of receptors and signalling systems in vascular parkinsonism, including cortical

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glutamatergic and cholinergic synapses, which may be a consequence of the disruption of subcortical-cortical connections caused by vascular lesions. The correlations found suggest that these neurotransmitter systems may be involved in the processes of cognitive

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decline in these patients.

Keywords: Neurophysiology; cognitive function; vascular parkinsonism; Parkinson’s disease; plasticity; long term potentiation.

ACCEPTED MANUSCRIPT 1. INTRODUCTION Vascular parkinsonism (VP) was first described by Critchley in 1929. This author reported a distinct clinical condition called ‘arteriosclerotic parkinsonism’, a syndrome characterised by rigidity, fixed faces and short-stepped gait in older patients with a history of arteriosclerosis and extensive cerebrovascular disease [1] . Clinically, core neurological signs and symptoms in VP are considered to be different from those

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observed in Parkinson’s disease (PD) and include bilateral and symmetrical involvement of the lower limbs, with gait disorder, short steps, postural instability and falls [2].

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Cognitive impairment has also been reported to be common in VP, presenting a cognitive profile different from that of PD [3]. Clinical features combined with radiological studies,

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including CT, MRI and DAT-SPECT support the diagnosis of VP [4,5]. Despite the number of articles published on the clinical and radiological features

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of VP, the diagnosis of this disease is still very challenging and the pathophysiological mechanisms involved in this condition are not completely understood yet. White matter

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ischaemic disease, strategic infarcts of the subcortical grey matter nuclei and, less commonly, large vessel infarcts are the factors involved in the development of VP [6]. However, there have been only a few reports on the pathophysiology of this disease and it

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is not clear how ischaemic lesions give rise to parkinsonism. Transcranial magnetic stimulation (TMS) is a non-invasive technique to study

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distinct brain functions [7]. This technique has been applied to healthy brains and many neurological and psychiatric disorders to explore the pathophysiology of these conditions, examine the clinical diagnostic usefulness and as a potential treatment [8]. From a

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pathophysiological point of view, it has become a useful method for evaluating the involvement of different neurotransmitter systems. To the best of our knowledge, very few previous studies have applied TMS in VP patients [9-11] and none have studied the sensorimotor system in this condition. One possible mechanism that has been suggested to explain VP is the disruption of sensorimotor integration caused by macroscopic infarcts in basal ganglia and diffuse small vessel disease [12,13]. Considering this, the main objective of our study was to investigate sensorimotor inhibition and plasticity in a group of patients with VP, comparing the results with a group of healthy controls. To assess sensorimotor inhibition, short latency afferent inhibition (SAI) protocol was used. In order to evaluate cortical associative sensorimotor plasticity, we used the paired associative stimulation (PAS) protocol. We hypothesize that VP patients will display

ACCEPTED MANUSCRIPT deficits in the integration of sensorimotor information as reflected by decreased SAI and decreased PAS-induced plasticity. We also aimed at correlating deficits in sensorimotor integration with neuropsychological profile in our patients as we hypothesize that these deficits may be related to the presence of cognitive decline, as previously described in

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other conditions such as PD [14].

ACCEPTED MANUSCRIPT 2. METHODS 2.1. Participants We included in this study 11 patients diagnosed with VP according to the diagnostic criteria proposed by Zijlmans et al. [15] (9 men, 2 women, mean age 75.7 years [SD=4.73]). Patients were recruited from the Neurology clinics at Virgen del Rocio Hospital in Seville. We also included a group of 13 healthy subjects with similar age and

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sex distribution (10 men, 3 women, mean age 72.3 years [SD=4.53]). Healthy controls were recruited from non-blood relatives, friends and spouses of patients. At the time of

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inclusion, clinical data including age at the onset of symptoms and disease duration were collected. In patients on treatment, the total L-dopa equivalent daily dose was recorded.

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All patients were assessed with the motor subsection of the Unified Parkinson's Disease Rating Scale (UPDRS - section III) and the Hoehn and Yahr scale during ‘on’ and ‘off’

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conditions. Neuroimaging studies (CT or MRI) were performed in all VP patients. The neuroimaging result was categorized as: white matter lesions, lacunar strokes and

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territorial infarction. All these details are given in Table 1. This study was approved by the local Ethics Committee and informed written

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consent was obtained from each participant.

2.2. Electromyographic recordings

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Electromyographic (EMG) recordings were made from abductor pollicis brevis (APB) and first dorsal interosseous (FDI) muscles on the side contralateral to the stimulated cortex with Ag-AgCl surface electrodes using a belly-tendon montage. EMG

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signals were amplified (1000x) and band-pass filtered (bandwidth 20Hz to 2kHz) with a Digitimer D360 amplifier (Digitimer, UK), acquired at a sampling rate of 5kHz through a CED 1401 laboratory interface (Cambridge Electronic Design, Cambridge, UK) and stored on a PC. The EMG traces were analysed using custom scripts implemented in SIGNAL software V.4.00.

2.3. TMS procedure Patients on dopaminergic treatment were advised to discontinue their medication the day before the TMS study (‘off’ state assessment). Patients were considered ‘off’ after overnight withdrawal of dopaminergic medications of at least 12 h. None of the VP patients involved in this study was taking long-acting dopaminergic drugs. At the time of

ACCEPTED MANUSCRIPT the study, none of the participants were on any other medications that could affect the TMS measurements. Single and paired-pulse TMS of the primary motor cortex were applied using Magstim 200 magnetic stimulators (Magstim Company, Carmarthenshire, Wales, UK). The magnetic stimulators were connected to a standard figure-of-eight coil with an external diameter of 70mm. The coil was held tangentially to the skull with the handle pointing backwards and laterally at an angle of ~45° to the sagittal plane in order to generate a posterior–anterior current in the brain. Experiments were performed with

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subjects fully relaxed and with their eyes open. The ‘hot spot’ was defined as the optimal scalp position for eliciting a MEP of maximum amplitude in the contralateral APB

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muscle. The amplitude of MEPs was measured peak to peak (mV) and then averaged.

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Patients and controls were tested in the left hemisphere. The N20 wave latency of somatosensory evoked potentials (SEPs) response was recorded from the right median

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nerve and analysed to verify the absence of delays in the arrival of the peripheral sensory stimulus to the left primary somatosensory cortex. SAI was measured in all subjects, PAS was measured in all VP patients and in 12 of the 13 healthy subjects, N20 was recorded

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in 7 VP patients and 11 healthy subjects.

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2.3.1. SEPs

N20 was recorded by stimulating the right median nerve with the reference electrode at Cz and the active electrode attached 2cm behind C3 (10–20 International

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System). A total of 200 responses were averaged twice and superimposed to identify the latency of the N20 peak.

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2.3.2. SAI

SAI was assessed for the contralateral APB as the target muscle using the technique reported by Tokimura et al. [17]. Conditioning stimuli were single pulses of electrical stimulation applied through bipolar electrodes to the median nerve at the wrist, with the cathode positioned proximally. The pulses were constant current square wave pulses with a pulse width of 200s. The intensity of the median nerve stimulus was set as three times the perceptual threshold, while the intensity of the magnetic stimulus was adjusted to evoke an MEP amplitude of 1mV. SAI was evaluated at rest at ISIs of 18, 20 and 22 ms between the electrical stimulus and the TMS stimulus. Ten MEPs were collected for each ISI and for the test stimulus alone. The presentation of the test stimuli and the conditioning stimuli were randomized within the SAI experimental block. To

ACCEPTED MANUSCRIPT assess the selectivity of the SAI protocol on median nerve innervated muscles, FDI MEP was also monitored.

2.3.3. Sensorimotor plasticity Sensorimotor plasticity was assessed by applying a PAS protocol. For the PAS protocol, 240 pairs of stimuli were given at 0.25Hz, using TMS of the APB area of the left motor cortex preceded by electrical stimulation of the contralateral median nerve at

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the wrist at a fixed interstimulus interval (ISI) of 25ms. Electrical stimulation was applied through a bipolar electrode, with the cathode positioned proximally. The pulses were

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constant current square wave pulses with a pulse width of 200s. The intensity of the

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median nerve stimulus was set at three times the perceptual threshold, while TMS intensity was adjusted to elicit a MEP amplitude of 1 mV. The effects of PAS have been

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reported to depend on the level of attention to the stimulated body part [16]. In order to control for this, we asked all participants to count the number of electrical stimuli that were delivered at the wrist level during the procedure.

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The facilitatory effects of the PAS protocol included the evaluation of APB resting motor threshold (RMT) and the recording of blocks of 20 single MEPs before and

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three times after PAS protocol: immediately after (t0), 10 min (t10) and 20 min (t20) after the protocol. To test the selectivity of the PAS protocol on median nerve innervated

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muscles, FDI MEP was also monitored.

2.4. Neuropsychological assessment

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All subjects underwent a neuropsychological assessment with tests adapted for the Spanish population to explore different cognitive domains, including global efficiency, executive functions, verbal memory, language and visuospatial function. Details of the different tests performed are given in the Supplementary material (Table 1S).

2.5. Data analysis Sample size was estimated based on the reported effect sizes of SAI and PAS in the PD population. Complete details for the sample size and power calculations are provided in the Supplementary material (Fig. 1S and 2S). The statistical analyses were performed with IBM SPSS software version 20.0 for Windows. To explore differences regarding SAI we used repeated measures ANOVA

ACCEPTED MANUSCRIPT with ‘group’ as between-subject factor and ‘time’ as within-subject factor. PAS-induced plasticity was also analysed in APB and FDI muscles using repeated measures ANOVA, using ‘time’ and ‘muscle’ as within-subject factors and ‘group’ as between-subject factor. PAS effects on RMT were assessed in separate two-way repeated measures ANOVA. Mauchley’s test assessed sphericity and Greenhouse-Geisser correction was used for nonspherical data. To explore within-group effects, we computed separate two-factorial ANOVAs for each group, with ‘time’ and ‘muscle’ as within-subject factors. Significant

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main effects and interactions in ANOVA were also followed by Bonferroni-corrected post hoc paired t-test analysis. N20 latencies were compared using t-tests.

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Results of the different neuropsychological tests were first compared between

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groups by using Student’s t test for independent measures. Significantly altered neuropsychological tests in VP were included in a correlation analysis with statistically

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significant TMS findings in this group. In this analysis the conditioned MEP amplitude was expressed as a percentage of the test MEP. For the significant SAI findings, the results of the different ISIs were averaged to yield a unique mean value per protocol. In

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the PAS protocol we selected the time after PAS with the largest effect size. Spearman’s correlation test was used for this analysis. Subsequently, we performed a multiple linear

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regression analysis with Bonferroni correction using neuropsychological measures as independent variables and TMS results as dependent variables, adjusting for age and UPDRS-III. Variables were included using a forward-selection method. All data are

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shown as means and standard deviations (SD).

ACCEPTED MANUSCRIPT 3. RESULTS 3.1. TMS and electrical intensities VP patients showed lower 1mV MEP intensity in FDI and lower 1mV MEP intensity in APB than healthy controls (1 mV FDI MEP: t22 =2.46, P=0.022; 1 mV APB MEP: t15 =2.53, P=0.022), whereas non-significant differences were found for the

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electrical stimulus (See Table 2S in the Supplementary material).

3.2. SEPs latencies

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MeanSD value of N20 latency was 20.562.08 ms in VP patients and 19.941.32 ms in healthy controls. These results were not significantly different between

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groups (t16 =-0.773, P=0.451).

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3.3. SAI

In SAI, repeated measures ANOVA showed main effect of ‘time’ (F 4,88 =11.23;

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P<0.001), ‘group’ (F1,22 =5.57; P=0.028), but not time x group interaction (F3,22 =1.41; P=0.249). Healthy controls showed significant inhibition at 20ms (P=0.002) and 22ms

3.4. PAS

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(P>0.524) (Fig. 1).

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(P=0.025). Conversely, VP patients did not show significant inhibition at any ISI

At baseline, APB RMT was lower in VP patients compared to healthy controls (P=0.031). However, no significant changes in APB RMT after PAS were found in VP

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patients (F3,30 =0.623; P=0.606). Healthy controls showed a reduction in RMT after PAS but failed to reach statistical significance (F3,33 =2.740; P=0.059). Fig. 2 shows results of PAS on APB MEP in VP patients and controls. A significant time x group interaction was found (F3,22 =5.730; P=0.005). Post-hoc tests revealed that PAS caused a statistically significant facilitation in APB MEP amplitudes in controls at t0 (P=0.029), t10 (P=0.014) and t20 (P=0.026). No statistically significant changes in APB MEP were observed at any specific time in VP patients (t0 P=0.71, t10 P=0.111, t20 P=0.319). The three-way interaction of time x muscle x group was not significant (F3,63 =0.987; P=0.405). To explore exclusively within-group effects, we computed separate two-way ANOVAs for each group, with ‘time’ and ‘muscle’ as within-subject factors. In VP patients, ANOVA showed that the main effect for the factor

ACCEPTED MANUSCRIPT ‘time’ remained not significant (F3,30 =0.291; P=0.832); this analysis also revealed a nonsignificant time x muscle interaction (F3,30 =0.589; P=0.378), indicating that there was no difference in PAS-induced effect in APB and FDI MEPs. In controls ANOVA demonstrated that the main effect for the factor ‘time’ was significant (F3,33 =3.224; P=0.035). Furthermore, we obtained a significant time x muscle interaction (F3,33 =6.848;

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P=0.001), indicating a topographic specificity of PAS in APB MEP.

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3.5. Neuropsychological tests

VP patients showed significant worse performance in all the Mattis dementia

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rating scale (MDRS) subtests, except conceptualisation. In addition, VP patients showed worse results in verbal memory (delayed recall) and executive tests (semantic fluency).

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No significant differences among groups occurred in the Go-no-go test, Letter verbal fluency (P), Clock drawing test or Boston naming test. Detailed scores and statistical

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results from the neuropsychological tests performed are shown in Table 2.

3.6. Neurophysiological to neuropsychological correlation in VP

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TMS values included in the correlation analyses were the mean value of SAI and the t0 of APB MEP amplitude in the PAS protocol. Neuropsychological tests included

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were the attention, initiation/perseveration, construction and memory domains of the MDRS, the total score of the MDRS, semantic fluency and the delayed recall from the WMS-III. We observed that some of the neuropsychological tests were correlated with

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both protocols. Detailed results of correlation analyses are shown in Table 3. Next, all neuropsychological tests correlating with the TMS paradigms were included in a multiple regression analysis with the TMS parameter as the dependent variable, adjusting for age and UPDRS-III in ‘off’ state. To avoid collinearity, only the total score of the MDRS was included in the model when a significant correlation was found at the same time with the total score of this scale and any of its domains. This analysis showed that the delayed recall from the WMS-III remained with a significant correlation with the mean value of SAI (adjusted R2 =0.341, P=0.045) and t0 of APB MEP amplitude in the PAS protocol (adjusted R2 =0.434, P=0.023). Detailed  and P values of this model are detailed in Tables 3S and 4S of the Supplementary material. Scatterplots of the significant correlations that were posteriorly introduced in the multiple linear regression model in

ACCEPTED MANUSCRIPT VP patients are shown in Fig. 3 and 4. We did not find any significant correlation in these

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analyses in controls.

ACCEPTED MANUSCRIPT 4. DISCUSSION This study shows sensorimotor abnormalities in patients with VP after using different TMS paradigms. Our findings include reduced SAI and an absence of long term potentiation (LTP)-like plasticity after PAS protocol. Interestingly, we found associations between neuropsychological measures and TMS results. To our knowledge, there have been no previous studies exploring sensorimotor system in VP. Furthermore, this is the

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first study to explore potential correlations between neurophysiologic abnormalities and cognitive profiles in these patients.

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Our study revealed decreased SAI in VP patients. The role of cholinergic circuits in SAI has been previously demonstrated, given that the effect of this protocol can be

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abolished or reduced by intravenous injection of muscarinic antagonists [16]. SAI gives the opportunity to test non-invasively the excitability of some cholinergic circuits in the

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human cerebral motor cortex. Our results suggest that a central cholinergic deficiency could be present in our group of patients. Remarkably, we also obtained a correlation

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between verbal memory and SAI. Memory abnormalities have previously been correlated with central cholinergic dysfunction and a reduction of SAI in patients with AD and dementia with Lewy bodies [17,18], which is in accordance with our findings. An

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abnormal SAI has also been found in a subgroup of patients with vascular dementia [19] and in cerebral autosomal dominant arteriopathy with subcortical infarcts and

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leukoencephalopathy (CADASIL) [20]. Recently, SAI has also been found to be significantly impaired in PD patients with cognitive impairment compared with cognitively normal PD patients [14]. The presence of similar changes in SAI in these different forms of dementing syndromes indicates that abnormalities in this protocol are

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not specific for VP patients and that they are probably more related to the processes of cognitive decline in these conditions, such that it may be considered a useful biomarker of increased risk of dementia in these patients. Some previous studies have suggested that acetylcholine is likely to play a part in cognition and attentional function. Attention is thought to be mediated by cholinergic circuits in the frontal lobes and thalamocortical processing and this association has been strengthened in studies of cholinesterase inhibitors, which have shown improvement in attentional scores in PD dementia and dementia with lewy body [21]. However, in our study, after multiple regression analyses adjusting for age and UPDRS-III, we did not obtain a significant correlation between SAI and the attention domain of the MDRS, so

ACCEPTED MANUSCRIPT we cannot support the association refered in previous literature. Nevertheless, further studies using more specific tests to assess attentional functions are needed to contrast our findings. The lack of LTP-like plasticity induced by the PAS protocol in our VP group was evidenced by the absence of both MEP amplitude facilitation and APB RMT decrease. At a molecular level, different studies have shown that PAS-induced LTP-like plasticity is related to glutamate NMDA receptors [22]. Interestingly, we obtained a correlation

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between impairment in cortical LTP-like phenomena and verbal memory (delayed recall). Battaglia et al. [23]. using Alzheimer’s disease (AD) patients and transgenic animal

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models, demonstrated a deficiency in NMDA receptor-dependent plasticity not only in

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the hippocampus, but also in the neocortex using mice brain slices and a PAS protocol in M1 in patients. These findings support our results and suggest a relationship between

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verbal memory impairment and altered cortical associative plasticity in patients with VP, in which abnormalities in the excitatory glutamatergic neurotransmission system may underlie this relationship with verbal memory. However, it also seems that some

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important properties of LTP, such as durability, specificity and associativity, can be implemented by a variety of receptors and signalling systems, apart from glutamatergic

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synapses, which must also be considered as part of the effects seen in our patients [24]. Abnormalities in sensorimotor integration have previously been reported in other conditions, such as stroke and parkinsonian syndromes. Suppresion of afferent inhibition

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has been reported in acute stroke [25]. Some studies have also documented an increase of intracortical excitatory activity remote from the lesion in stroke patients, as well as a disinhibition in the unaffected hemisphere [26]. In PD patients off medication a

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significant increase of SAI has been described on the affected side [27,28], however, as previously mentioned, in PD patients with mild cognitive impairment SAI has also been found to be significantly decreased compared with cognitively normal PD patients [14]. Studies investigating the motor cortical plasticity have found altered plasticity in PD but there are inconsistencies among these studies, with some of them reporting that PAS elicits abnormally reduced LTP-like plasticity, and others reporting an increased plasticity. The abnormalities in sensorimotor integration documented in all these conditions reflect that these changes seem unlikely to underlie any specific VP feature, but rather possibly reflect a nonspecific imbalance of inhibitory and facilitory cortical circuits shared with other conditions. It has not yet been completely elucidated whether these abnormalities are a primary disease-related pathophysiological dysfunction or a

ACCEPTED MANUSCRIPT compensatory mechanism. Considering that VP is related in the majority of cases with the presence of subcortical white matter ischaemic disease and infarcts of the subcortical grey matter nuclei, an important issue is the explanation of how our TMS findings, which represent a cortical phenomenon, can be present in these patients. We postulate that this is probably related to the interruption of ascending glutamatergic and cholinergic axons by subcortical vascular lesions which may lead to widespread disconnection of cortical and

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subcortical neurons, as previously proposed in CADASIL [20,29]. In a minority of cases, large vessel infarcts and cortical infarcts are the factors involved in the development of

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VP. In these cases TMS abnormalities may suggest a primary cortical phenomenon.

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Although this is the first study to explore SAI and PAS in VP patients to date, our sample size is relatively small and further studies with larger cohorts are required to

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confirm our findings and to give a definite conclusion. Another limitation of this study is that VP, similarly to vascular dementia, is the epiphenomenon of vascular pathology that can affect cortical or subcortical structures with a large variability in localization of

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vascular lesions. This may determine different patterns of cognitive decline and TMS abnormalities in these patients. Further studies including a bigger sample of patients with

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different subtypes of vascular lesions are necessary to clarify their effect in the pathophysiology of this condition. Finally, although most TMS studies have been performed in the dominant hemisphere, it is true that some experiments, particularly in

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PD population, have found a different effect when comparing the most and the less affected sides. No previous studies have explored these effects in VP patients, but it might also exist an asymmetry in TMS results in VP patients with asymmetric symptoms.

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Further studies to clarify the possible differences between hemispheres are needed. In conclusion, our findings demonstrate that SAI and PAS are impaired in VP patients and we provide correlations between these TMS paradigms and impairment in verbal memory tests. This suggests that damage to a variety of receptors and signalling systems, including cortical glutamatergic and cholinergic tracts, may be implicated in cognitive impairment in VP. These correlations are particularly important and further studies to confirm these results are necessary, since they may help to better understand the pathophysiology of this condition, consider TMS as a possible diagnostic tool and even evaluate the efficacy of pharmacological agents in cognitive decline in this entity. CONFLICT ON INTEREST On behalf of all authors, the corresponding author states that there is no conflict of

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FUNDING This work was supported by grants from the Ministerio de Economía y Competitividad de España [SAF2007-60700], the Instituto de Salud Carlos III [PI10/01674, CP08/00174,

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PI13/01461], the Consejería de Economía, Innovación, Ciencia y Empleo de la Junta de Andalucía [CVI-02526, CTS-7685], the Consejería de Salud y Bienestar Social de la Junta de Andalucía [PI-0377/2007, PI-0741/2010, PI-0437-2012], the Sociedad Andaluza

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de Neurología, the Jacques and Gloria Gossweiler Foundation and the Fundación Alicia

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Koplowitz.

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attention, and falls in Parkinson's disease. Mov Disord 26(14):2496-2503. [22] Stefan K, Kunesch E, Benecke R et al (2002) Mechanisms of enhancement of human

Physiol 543:699-708.

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motor cortex excitability induced by interventional paired associative stimulation. J

[23] Battaglia F, Wang HY, Ghilardi MF et al (2007) Cortical plasticity in Alzheimer's

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disease in humans and rodents. Biol Psychiatry 62:1405-1412. [24] Cooke SF, Bliss TVP (2006) Plasticity in the human central nervous system. Brain 129:1659-1673.

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[25] Di Lazzaro V, Profice P, Pilato F et al (2012) The Level of Cortical Afferent Inhibition in Acute Stroke Correlates With Long-Term Functional Recovery in Humans. Stroke 43:250-252.

[26] Rossini P, Calautti C, Pauri F, Baron JC (2003) Post-stroke plastic reorganisation in the adult brain. Lancet Neurology 2: 493–502. [27] Di Lazzaro V, Oliviero A, Pilato F et al (2004) Normal or enhanced short latency afferent inhibition in Parkinson’s disease? Brain 127(Pt 4):E8. [28] Nardone R, Florio I, Lochner P, Tezzon F (2005) Cholinergic cortical circuits in Parkinson’s disease and in progressive supranuclear palsy: a transcranial magnetic stimulation study. Exp Brain Res 163: 128–131.

ACCEPTED MANUSCRIPT [29] Mesulam M, Siddique T, Cohen B (2003) Cholinergic denervation in a pure multi-

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infarct state: observations on CADASIL. Neurology 60:1183-1185.

ACCEPTED MANUSCRIPT FIGURE LEGENDS Fig. 1. Representation of short afferent inhibition protocol (SAI) in abductor pollicis brevis (APB) performed in VP patients and healthy subjects. Results are expressed in mean mV±SEM.

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*Statistically significant difference comparing the conditioned MEP to the test MEP, P<0.05, ** Statistically significant difference comparing the conditioned MEP to the test

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MEP, P<0.01.

Fig. 2. Representation of sensorimotor plasticity in abductor pollicis brevis (APB) after

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using a paired associative stimulation (PAS) protocol performed in VP patients and healthy subjects, up to 20 min after the end of the protocol. Results are expressed in mean

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mV±SEM.

*Statistically significant difference comparing the conditioned MEP to the test MEP,

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P<0.05.

Fig. 3. Scarterplotts for SAI significant correlations that were posteriorly introduced in the multiple linear regression model in vascular parkinsonism patients, including

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regression lines and showing the 95% confidence interval of the best-fit line.

Fig. 4. Scarterplotts for PAS (t0) significant correlations in vascular parkinsonism patients, including regression lines and showing the 95% confidence interval of the bestfit line.

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Figure 2

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Figure 3

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Figure 4

ACCEPTED MANUSCRIPT Table 1. Demographic, clinical and neuroimaging features of VP patients

Case

Sex

Age

Disease

UPDRS-

Hoehn y

Medication

Equivalent dose

Neuroimaging

(y)

duration (y)

III

Yahr

(yes/no)

of L-dopa (mg/d)

findings

‘on’/’off’

‘on’/’off’ WMD, LS, TI

Female

82

6

24 / 37

2/4

Yes

750

2

Male

72

9

- / 46

-/4

No

-

WMD, LS

3

Male

79

2

- / 13

- / 2.5

No

-

WMD, LS

4

Male

69

1

24 / 39

2 / 2.5

Yes

300

WMD, LS

5

Male

78

8

34 / 37

5/5

Yes

843

WMD, LS

6

Female

75

3

33 / 30

2.5 / 3

Yes

250

WMD, LS

7

Male

83

3

26 / 36

3/3

Yes

300

WMD, LS

8

Male

78

4

- / 18

-/3

No

-

WMD, LS

9

Male

69

2

20 / 23

2.5 / 2.5

Yes

300

WMD, LS

10

Male

74

4

- / 19

- / 2.5

No

-

WMD, LS

11

Male

74

5

- / 29

-/3

No

-

WMD, LS, TI

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Abbreviations: UPDRS-III, Unified Parkinson’s Disease Rating Scale – Part III; WMD,

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white matter disease; LS, lacunar strokes; TI, territorial infarction.

ACCEPTED MANUSCRIPT Table 2. Results of the neuropsychological tests in the 2 groups (VP and healthy controls). Results are displayed as meansstandard deviation (SD).

VARIABLES

P-VALUE

VP

HC

Attention

34.361.91

35.920.76

Construction

4.731.79

6.00.0

Conceptualisation

32.645.46

36.082.81

Initiation/Perseveration

30.916.09

36.151.72

t11.36 =2.76, P=0.018

Memory

20.184.66

23.622.75

t22 =2.24, P=0.036

MDRS

6.183.34

Go-no-go (inhibition)

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t14.38 =1.88, P=0.079

t11.37 =3.01, P=0.011

7.233.49

t22 =0.75, P=0.463

4.642.38

6.773.44

t21.24 =1.78, P=0.088

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Go-no-go (interference)

137.77 4.53

t10 =2.35, P=0.040

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122.82 15.92

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Total score

t12.66 =2.54, P=0.025

WMS-III Word List Immediate recall

22.648.55

28.466.81

t22 =1.86, P=0.077

Delayed recall

3.273.07

5.923.12

t22 =2.09, P=0.049

39.9143.94

61.6925.34

t22 =1.83, P=0.081

20.552.54

21.152.58

t22 =0.58, P=0.568

15.184.56

21.03.54

t22 =3.52, P=0.02

10.456.25

12.235.12

t22 =0.76, P=0.452

8.332.56

9.810.38

t8.25 =1.71, P=0.124

7.223.62

8.461.96

t11.27 =0.93, P=0.369

12.602.17

13.771.23

t13.42 =1.52, P=0.151

Recognition

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Semantic fluency (buying)

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Percentage retention

Letter Verbal Fluency (P) Clock Drawing Test Copy

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Spontaneous

Boston Naming test (15 items)

Abbreviations: VP, vascular parkinsonism; HC, healthy controls; MDRS, Mattis Dementia Rating Scale; WMS-III, Wechsler Memory Scale - Third edition.

ACCEPTED MANUSCRIPT Table 3. Neurophysiological to neuropsychological correlations in VP patients.

Mean value of SAI

Neuropsychological tests

PAS t0 (APB) (%)

Rho value

P value

-0.670

0.024*

0.647

0.032*

-0.377

0.253

0.602

0.050

-0.696

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(%)

Rho value

P value

*

0.017

0.596

0.053

-0.520

0.101

0.699

0.017*

-0.615

0.044*

0.601

0.050

-0.220

0.515

0.450

0.165

-0.757

0.007*

0.743

0.009*

GLOBAL EFFICIENCY MDRS-Initiation/Perseveration MDRS - Construction MDRS - Memory

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MDRS – Total score

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MDRS - Attention

Semantic fluency VERBAL MEMORY

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WMS-III – Delayed recall

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EXECUTIVE FUNCTION

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* Statistically significant difference of correlation R value

ACCEPTED MANUSCRIPT Highlights 

We examined transcranial magnetic stimulation findings in 11 vascular parkinsonism (VP) patients and 13 healthy controls.



VP patients showed reduced short afferent inhibition and lack of long term

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Correlations were found in these patients between sensorimotor inhibition and sensorimotor plasticity with verbal memory tests, suggesting cortical cholinergic and

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glutamatergic involvement in cognitive decline in VP.

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

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potentiation-like plasticity after paired associative stimulation protocol.