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Berti V, Polito C, Borghammer P, Ramat S, Mosconi L, Vanzi E, De Cristofaro MT, De Leon M, Sorbi S, Pupi A. Alternative normalization methods demonstrate widespread cortical hypometabolism in untreated de novo Parkinson's disease. THE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING : OFFICIAL PUBLICATION OF THE ITALIAN ASSOCIATION OF NUCLEAR MEDICINE (AIMN) [AND] THE INTERNATIONAL ASSOCIATION OF RADIOPHARMACOLOGY (IAR), [AND] SECTION OF THE SOCIETY OF... 2012; 56:299-308. [PMID: 22695340 PMCID: PMC3846292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
AIM Previous positron emission tomography (PET) [18F]fluorodeoxyglucose ([18F]FDG) studies in Parkinson's disease (PD) demonstrated that moderate to late stage patients display widespread cortical hypometabolism, whereas early stage PD patients exhibit little or no cortical changes. However, recent studies suggested that conventional data normalization procedures may not always be valid, and demonstrated that alternative normalization strategies better allow detection of low magnitude changes. We hypothesized that these alternative normalization procedures would disclose more widespread metabolic alterations in de novo PD. METHODS [18F]FDG PET scans of 26 untreated de novo PD patients (Hoehn & Yahr stage I-II) and 21 age-matched controls were compared using voxel-based analysis. Normalization was performed using gray matter (GM), white matter (WM) reference regions and Yakushev normalization. RESULTS Compared to GM normalization, WM and Yakushev normalization procedures disclosed much larger cortical regions of relative hypometabolism in the PD group with extensive involvement of frontal and parieto-temporal-occipital cortices, and several subcortical structures. Furthermore, in the WM and Yakushev normalized analyses, stage II patients displayed more prominent cortical hypometabolism than did stage I patients. CONCLUSION The use of alternative normalization procedures, other than GM, suggests that much more extensive cortical hypometabolism is present in untreated de novo PD patients than hitherto reported. The finding may have implications for our understanding of the basic pathophysiology of early-stage PD.
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Federighi P, Ramat S, Zee D, Leigh R, Piu P, Rufa A. Dynamic Properties of Saccades Identify Forms of Spinocerebellar Ataxia (S48.005). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.s48.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Maremmani C, Rossi G, Tambasco N, Fattori B, Pieroni A, Ramat S, Napolitano A, Vanni P, Serra P, Piersanti P, Zanetti M, Coltelli M, Orsini M, Marconi R, Purcaro C, Rossi A, Calabresi P, Meco G. The validity and reliability of the Italian Olfactory Identification Test (IOIT) in healthy subjects and in Parkinson's disease patients. Parkinsonism Relat Disord 2012; 18:788-93. [PMID: 22510205 DOI: 10.1016/j.parkreldis.2012.03.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 03/14/2012] [Accepted: 03/23/2012] [Indexed: 11/16/2022]
Abstract
BACKGROUND Olfactory function can be rapidly evaluated by means of standardized olfactory tests. Multiple-choice smell identification tests can be conditioned by cultural background. To investigate a new tool for detecting olfactory deficit in Italian subjects we developed a multiple-choice identification test prepared with odorants belonging to the Italian culture. METHODS The Italian Olfactory Identification Test (IOIT) was developed with 33 microencapsulated odorants with intensity of odors and headspace Gas Chromatography being tested. Test-retest reliability of the IOIT was evaluated. The IOIT was administered to 511 controls and 133 Parkinson's patients. RESULTS In healthy subjects the number of IOIT errors increased with age for both females (p < 0.0001) and males (p < 0.0001), while in the Parkinson's disease group the number of IOIT errors was significantly greater where compared to healthy subjects (p < 0.0001 in all age groups). The reference limits applied to all age groups revealed an IOIT sensitivity of 93% and a specificity of 99%. The test-retest reliability was excellent. CONCLUSION The IOIT is highly reliable, disposable, easy to administer, not fragile, and has a long shelf-life. All these features make the IOIT suitable for clinical use as well as for population screening and to discriminate Parkinson's patients from healthy subjects.
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Morgante L, Colosimo C, Antonini A, Marconi R, Meco G, Pederzoli M, Pontieri FE, Cicarelli G, Abbruzzese G, Zappulla S, Ramat S, Manfredi M, Bottacchi E, Abrignani M, Berardelli A, Cozzolino A, Paradiso C, De Gaspari D, Morgante F, Barone P. Psychosis associated to Parkinson's disease in the early stages: relevance of cognitive decline and depression. J Neurol Neurosurg Psychiatry 2012; 83:76-82. [PMID: 21836035 DOI: 10.1136/jnnp-2011-300043] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE To evaluate the prevalence of psychosis associated with Parkinson's disease (PSY-PD) in its early stages, its incidence over a 24 month follow-up period and the association with motor and non-motor clinical features. METHODS PRIAMO is a 2 year longitudinal observational study that has enrolled patients with parkinsonism in 55 Italian centres. A cohort of 495 patients with early disease stage PD (baseline Hoehn and Yahr score ≤ 2, disease's duration (median) 3.4 years) were followed for 2 years. PSY-PD was evaluated by means of a clinician rated questionnaire and defined as the presence of at least one of the following symptoms occurring for at least 1 month: illusions, hallucinations, jealousy ideas and persecutory ideas. Patients with and without PSY-PD were compared on several clinical variables, encompassing motor and non-motor features. RESULTS The prevalence of PSY-PD at baseline was 3%; the incidences at 12 and 24 months were 5.2% and 7.7%, respectively. Longer disease duration and prescription of dopamine agonists at baseline were associated with the development of PSY-PD over the 24 month period. At this follow-up time, worse disease severity, decline in cognitive performances, presence of depressive symptoms and anxiety were more frequently observed in PSY-PD. CONCLUSIONS Psychotic type symptoms may occur in the early stages of PD although less frequently than in later stages. Beyond dopaminergic treatment, there are disease related factors, such as disease severity and the occurrence of cognitive and depressive symptoms, which may underlie the onset of psychotic type symptoms from the earliest stages.
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Marconi R, Antonini A, Barone P, Colosimo C, Avarello TP, Bottacchi E, Cannas A, Ceravolo MG, Ceravolo R, Cicarelli G, Gaglio RM, Giglia L, Iemolo F, Manfredi M, Meco G, Nicoletti A, Pederzoli M, Petrone A, Pisani A, Pontieri FE, Quatrale R, Ramat S, Scala R, Volpe G, Zappulla S, Bentivoglio AR, Stocchi F, Trianni G, Del Dotto P, De Gaspari D, Grasso L, Morgante F, Santangelo G, Fabbrini G, Morgante L. Frontal assessment battery scores and non-motor symptoms in parkinsonian disorders. Neurol Sci 2011; 33:585-93. [PMID: 22048791 DOI: 10.1007/s10072-011-0807-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Accepted: 09/17/2011] [Indexed: 10/16/2022]
Abstract
Using data from the PRIAMO study, we investigated non-motor symptoms (NMS) versus frontal lobe dysfunction in patients with idiopathic Parkinson disease (PD); 808 patients with PD and 118 with atypical parkinsonisms (AP) were consecutively enrolled at 55 Centers in Italy. Twelve categories of NMS were investigated. Cognitive impairment was defined as a Mini-Mental Status Evaluation score ≤ 23.8 and frontal lobe dysfunction as a Frontal Assessment Battery (FAB) score ≤ 3.48. Multivariable logistic regression was used to identify predictor of frontal lobe dysfunction in 524 PD patients, and a generalized linear model was used for each of the six FAB items. Not only the total FAB scores but also the single FAB items were lower in AP versus PD (p ≤ 0.005). Age (OR = 1.05), cognitive impairment (OR = 9.54), lack of cardiovascular symptoms (OR = 3.25), attention or memory problems (OR = 0.59) and treatment with L: -DOPA (OR = 5.58) were predictors of frontal lobe dysfunction. MMSE was negatively associated with all FAB items (β ≤ -0.16) and age with all FAB items but prehension behavior (β ≤ -0.01). Previous use of L: -DOPA was negatively associated with verbal fluency (β = -0.32) possibly acting as surrogate marker of disease duration. Cognitive impairment is a predictor of frontal lobe dysfunction. Among NMS, lack of attention or memory problems were negatively associated with frontal impairment. Further studies are nonetheless needed to better identify the predictors of frontal impairment in PD patients.
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Manzari L, Colletti V, Mandalà M, Manganotti P, Ramat S, Colletti L. W3.4 Intraoperative observation of changes in cochlear nerve action potentials during exposure to electromagnetic fields generated by mobile phones. Clin Neurophysiol 2011. [DOI: 10.1016/s1388-2457(11)60031-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Bertolini G, Ramat S. Velocity storage in the human vertical rotational vestibulo-ocular reflex. Exp Brain Res 2010; 209:51-63. [PMID: 21170706 DOI: 10.1007/s00221-010-2518-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 12/02/2010] [Indexed: 11/29/2022]
Abstract
Human horizontal rotational vestibulo-ocular reflex (rVOR) has been extensively investigated: the horizontal semicircular canals sense yaw rotations with high-pass filter dynamics and a time constant (TC) around 5 s, yet the rVOR response shows a longer TC due to a central processing stage, known as velocity storage mechanism (VSM). It is generally assumed that the vertical rVOR behaves similarly to the horizontal one; however, VSM processing of the human vertical rVOR is still to be proven. We investigated the vertical rVOR in eight healthy human subjects using three experimental paradigms: (1) per- and post-rotatory around an earth-vertical axis (ear down rotations, EDR), (2) post-rotatory around an earth-horizontal axis with different stopping positions (static otolith stimulation), (3) per-rotatory around an earth-horizontal axis (dynamic otolith stimulation). We found that the TC of vertical rVOR responses ranged 3-10 s, depending both on gravity and on the direction of rotation. The shortest TC were found in response to post-rotatory earth-horizontal stimulation averaging 3.6 s, while they were prolonged in EDR stimulation, i.e. when the head angular velocity vector is aligned with gravity, with a mean value of about 6.0 s. Overall, the longest TC were observed in per-rotatory earth-horizontal stimulation, averaging 7.8 s. The finding of longer TC in EDR than in post-rotatory earth-horizontal stimulation indicates a role for the VSM in the vertical rVOR, although its contribution appears to be weaker than on the horizontal rVOR and may be directionally asymmetric. The results from per-rotatory earth-horizontal stimulation, instead, imply a role for the otoliths in controlling the duration of the vertical rVOR response. We found no reorientation of the response toward earth horizontal, indicating a difference between human and monkey rVOR.
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Bohler A, Mandala M, Ramat S. A software program for the head impulse testing device (HITD). ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2010; 2010:6615-8. [PMID: 21096520 DOI: 10.1109/iembs.2010.5627138] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The vestibulo-ocular reflex (VOR) uses head angular acceleration information transduced by the semicircular canals in the inner ear in order to drive eye movements that compensate for head rotations, and thus stabilize the visual scene on the retina. Peripheral and central vestibular pathologies may impair the function of the VOR, so that compensation becomes incomplete, making clear vision during head movement impossible. Powerful adaptive mechanisms quickly allow the central nervous system to use residual vestibular information or information provided through other senses to supplement the deficient VOR. Such recovery makes the clinical diagnosis difficult to classical testing techniques, yet the head impulse test allows to reveal vestibular deficits even in adapted patients. A compensatory saccade at the end of the head movement is the clinical sign of a vestibular deficit, and may be spotted by the experienced clinician. Here we describe the rationale and the software program driving a new computerized technique for reliably assessing vestibular function at different head angular accelerations, based on evaluating the ability of the patient in reading a character on the screen while the head is being rotated.
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Bertolini G, Ramat S, Laurens J, Bockisch CJ, Marti S, Straumann D, Palla A. Velocity storage contribution to vestibular self-motion perception in healthy human subjects. J Neurophysiol 2010; 105:209-23. [PMID: 21068266 DOI: 10.1152/jn.00154.2010] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Self-motion perception after a sudden stop from a sustained rotation in darkness lasts approximately as long as reflexive eye movements. We hypothesized that, after an angular velocity step, self-motion perception and reflexive eye movements are driven by the same vestibular pathways. In 16 healthy subjects (25-71 years of age), perceived rotational velocity (PRV) and the vestibulo-ocular reflex (rVOR) after sudden decelerations (90°/s(2)) from constant-velocity (90°/s) earth-vertical axis rotations were simultaneously measured (PRV reported by hand-lever turning; rVOR recorded by search coils). Subjects were upright (yaw) or 90° left-ear-down (pitch). After both yaw and pitch decelerations, PRV rose rapidly and showed a plateau before decaying. In contrast, slow-phase eye velocity (SPV) decayed immediately after the initial increase. SPV and PRV were fitted with the sum of two exponentials: one time constant accounting for the semicircular canal (SCC) dynamics and one time constant accounting for a central process, known as velocity storage mechanism (VSM). Parameters were constrained by requiring equal SCC time constant and VSM time constant for SPV and PRV. The gains weighting the two exponential functions were free to change. SPV were accurately fitted (variance-accounted-for: 0.85 ± 0.10) and PRV (variance-accounted-for: 0.86 ± 0.07), showing that SPV and PRV curve differences can be explained by a greater relative weight of VSM in PRV compared with SPV (twofold for yaw, threefold for pitch). These results support our hypothesis that self-motion perception after angular velocity steps is be driven by the same central vestibular processes as reflexive eye movements and that no additional mechanisms are required to explain the perceptual dynamics.
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Pallanti S, Bernardi S, Raglione LM, Marini P, Ammannati F, Sorbi S, Ramat S. Complex repetitive behavior: punding after bilateral subthalamic nucleus stimulation in Parkinson's disease. Parkinsonism Relat Disord 2010; 16:376-80. [PMID: 20346726 DOI: 10.1016/j.parkreldis.2010.02.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 02/12/2010] [Accepted: 02/22/2010] [Indexed: 10/19/2022]
Abstract
"Punding" is the term used to describe a stereotyped motor behavior characterized by an intense fascination with repetitive purposeless movements, such as taking apart mechanical objects, handling common objects as if they were new and entertaining, constantly picking at oneself, etc. As a phenomenon with both impulsive and compulsive features, the phenomenology of punding is currently being questioned. In order to investigate the pathophysiology of this phenomenon, we screened a population of Parkinson's disease (PD) outpatients who underwent subthalamic nucleus deep brain stimulation (STN DBS). We conducted a patient-and-relative-completed survey with 24 consecutive patients in an academic outpatient care center, using a modified version of a structured interview. Patients were administered the Unified Parkinson's Disease Rating Scale (UPDRS), the Obsessive-Compulsive Inventory and the Sheehan Disability Scale. Five (20.8%) of the 24 subjects were identified as punders, including three men (60%) and two women. The punders were comparable to the non-punders in terms of clinical and demographic factors. The punder and non-punder groups only differed statistically with regard to the length of time from DBS implantation. Those findings suggest that punding might be induced by STN DBS, and its rate of occurrence in DBS population seems to be more common than previously suspected.
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Sestini S, Pupi A, Ammannati F, Ramat S, Sorbi S, Sciagrà R, Mansi L, Castagnoli A. Predictive potential of pre-operative functional neuroimaging in patients treated with subthalamic stimulation. Eur J Nucl Med Mol Imaging 2010; 37:12-22. [PMID: 19582450 DOI: 10.1007/s00259-009-1198-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 06/03/2009] [Indexed: 10/20/2022]
Abstract
PURPOSE The aim of this study was to investigate the predictive potential of pre-operative regional cerebral blood flow (rCBF) in the pre-supplementary motor area (pre-SMA) and clinical factors in Parkinson's disease (PD) patients treated with subthalamic nucleus (STN) stimulation. METHODS Ten patients underwent rCBF SPECT and motor Unified Parkinson's Disease Rating Scale (UPDRS) pre- and post-operatively during stimulation at 5 and 42 months. Statistical parametric mapping (SPM) was used to extract rCBF values in the pre-SMA because it is related with motor improvement. Post-operative outcomes included motor response to stimulation and percent improvement in UPDRS. Pre-operative predictors were explored by correlation test, linear regression and multivariate analyses. RESULTS Higher pre-operative rCBF in the pre-SMA and younger age were associated with favourable outcomes at 5 and 42 months. Pre-operative rCBF results were significantly associated with baseline clinical factors. CONCLUSION This study shows that PD patients with younger age have higher rCBF values in the pre-SMA and better outcome, thus giving the rationale to the hypothesis that STN stimulation could be considered early in the course of disease.
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Abstract
Single-unit recordings of vestibular afferents from the semicircular canals of squirrel monkeys have shown that the cupular time constant (T(c)) is between 5 and 6 sec. Such recordings obviously cannot be performed in humans, and the corresponding values have thus been inferred to be somewhat longer based on their size and on the cupula-endolymph system. The ocular motor response of the rotational vestibulo-ocular reflex (rVOR) is characterized by longer time constants, typically between 15 and 20 sec, due to the so-called velocity storage mechanism (VSM), which prolongs the time constant of the afferents through central processing. Recent studies have attempted to determine the time constant of the cupula by fitting the slow phase velocity (SPV) of the response to postrotational stimuli using a mathematical model of the rVOR processing. To this goal they considered the processing of head velocity due to the peripheral vestibular organs and to the VSM. The resulting estimates of T(c) are lower than expected, averaging about 4 sec. These modeling approaches, though, neglect both the processing of the final common pathway and the adaptation shown by the discharge of primary vestibular afferents. Here we argue that such an approach may be bound to underestimate the duration of the rVOR time constants.
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Barone P, Antonini A, Colosimo C, Marconi R, Morgante L, Avarello TP, Bottacchi E, Cannas A, Ceravolo G, Ceravolo R, Cicarelli G, Gaglio RM, Giglia RM, Iemolo F, Manfredi M, Meco G, Nicoletti A, Pederzoli M, Petrone A, Pisani A, Pontieri FE, Quatrale R, Ramat S, Scala R, Volpe G, Zappulla S, Bentivoglio AR, Stocchi F, Trianni G, Dotto PD. The PRIAMO study: A multicenter assessment of nonmotor symptoms and their impact on quality of life in Parkinson's disease. Mov Disord 2009; 24:1641-9. [PMID: 19514014 DOI: 10.1002/mds.22643] [Citation(s) in RCA: 937] [Impact Index Per Article: 62.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Colosimo C, Morgante L, Antonini A, Barone P, Avarello TP, Bottacchi E, Cannas A, Ceravolo MG, Ceravolo R, Cicarelli G, Gaglio RM, Giglia L, Iemolo F, Manfredi M, Meco G, Nicoletti A, Pederzoli M, Petrone A, Pisani A, Pontieri FE, Quatrale R, Ramat S, Scala R, Volpe G, Zappulla S, Bentivoglio AR, Stocchi F, Trianni G, Del Dotto P, Simoni L, Marconi R. Non-motor symptoms in atypical and secondary parkinsonism: the PRIAMO study. J Neurol 2009; 257:5-14. [DOI: 10.1007/s00415-009-5255-7] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 06/12/2009] [Accepted: 07/08/2009] [Indexed: 10/20/2022]
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Bertolini G, Bockisch CJ, Straumann D, Zee DS, Ramat S. Estimating the time constant of pitch rVOR by separation of otoliths and semicircular canals contributions. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2008:1060-3. [PMID: 19162845 DOI: 10.1109/iembs.2008.4649342] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The rotational vestibulo-ocular reflex (rVOR) contributes to gaze stabilitization by compensating head rotational movements sensed by the semicircular canals (SCC). The CNS improves the performance of the horizontal rVOR through the so called velocity storage mechanism (VSM). However the properties of the VSM in response to pitch rotations are less well known. We recorded eye movements evoked by whole-body constant-velocity pitch rotations about an earth-horizontal, interaural axis in four healthy human subjects. Subjects were tumbled forward, and backward, at 60 deg/s for over one minute using a 3D turntable. In these conditions also the otoliths contribute to the perception of head rotation because they sense the changes in direction of the gravity vector. The vertical slow phase velocity (SPV) responses show the typical exponential decay of the rVOR and a residual, otolith-driven sinusoidal modulation with a bias. Here the estimates of the contributions coming from the otoliths and from the canals are based on a linear summation hypothesis. The time constants of the canal-driven vertical component of the SPV ranged from 6 to 9 seconds. These values are closer to those produced by the SCC alone than the typical 20 s produced by the VSM in the horizontal plane, confirming the relatively small contribution of the VSM to these vertical responses. We also show that the estimation method, while it may be not physiologically accurate, is easy to implement and leads to reliable results.
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Bernardi S, Ramat S, Raglione L, Marini P, Sorbi S, Ammannati F, Pallanti S. Punding after bilateral subthalamic nucleus stimulation in Parkinson' disease. Eur Psychiatry 2008. [DOI: 10.1016/j.eurpsy.2008.01.1212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Shaikh AG, Jinnah HA, Tripp RM, Optican LM, Ramat S, Lenz FA, Zee DS. Irregularity distinguishes limb tremor in cervical dystonia from essential tremor. J Neurol Neurosurg Psychiatry 2008; 79:187-9. [PMID: 17872981 PMCID: PMC2737356 DOI: 10.1136/jnnp.2007.131110] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Patients with cervical dystonia (CD) often have limb tremor that is clinically indistinguishable from essential tremor (ET). Whether a common central mechanism underlies the tremor in these conditions is unknown. We addressed this issue by quantifying limb tremor in 19 patients with CD and 35 patients with ET. METHOD Postural, resting and kinetic tremors were quantified (amplitude, mean frequency and regularity) using a three-axis accelerometer. RESULTS The amplitude of limb tremor in ET was significantly higher than in CD, but the mean frequency was not significantly different between the groups. The cycle-to-cycle variability of the frequency (ie the tremor irregularity), however, was significantly greater (approximately 50%) in CD. Analysis of covariance excluded the possibility that the increased irregularity was related to the smaller amplitude of tremor in CD (ANCOVA: p = 0.007, F = 5.31). DISCUSSION We propose that tremor in CD arises from oscillators with different dynamic characteristics, producing a more irregular output, whereas the tremor in ET arises from oscillators with similar dynamic characteristics, producing a more regular output. We suggest that variability of tremor is an important parameter for distinguishing tremor mechanisms. It is possible that changes in membrane kinetics based on the pattern of ion channel expression underlie the differences in tremor in some diseases.
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Ramat S, Leigh RJ, Zee DS, Shaikh AG, Optican LM. Applying saccade models to account for oscillations. PROGRESS IN BRAIN RESEARCH 2008; 171:123-30. [PMID: 18718290 DOI: 10.1016/s0079-6123(08)00616-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Saccadic oscillations are unwanted back-to-back saccades occurring one upon the other that produce a high-frequency oscillation of the eyes (usually 15-30 Hz). These may occur transiently in normal subjects, for example, around the orthogonal axis of a purely horizontal or vertical saccade, during combined saccade-vergence gaze shifts or during blinks. Some subjects may produce saccadic oscillations at will, usually with convergence. Pathological, involuntary saccadic oscillations such as flutter and opsoclonus are prominent in certain diseases. Our recent mathematical model of the premotor circuit for generating saccades includes brainstem burst neurons in the paramedian pontine reticular formation (PPRF), which show the physiological phenomenon of post-inhibitory rebound (PIR). This model makes saccadic oscillations because of the positive feedback among excitatory and inhibitory burst neurons. Here we review our recent findings and hypotheses and show how they may be reproduced using our lumped model of the saccadic premotor circuitry by reducing the inhibitory efficacy of omnipause neurons.
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Ramat S, Pré D, Magenes G. An internal model of self-motion based on inertial signals. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2006:4961-4. [PMID: 17946271 DOI: 10.1109/iembs.2006.259926] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The question of how the central nervous system can distinguish tilt with respect to gravity from inertial acceleration due to translation in a horizontal plane using vestibular information has long been debated by the scientific community over the past ten years. Recently, it was hypothesized that such discrimination may be based on the multisensory integration of information provided by the otolith organs and the semicircular canals. Some evidence of such processing was found in the neural activity of cells in the fastigial nuclei and vestibular nuclei. To investigate the ability of the central nervous system to build an internal model of self motion based on vestibular signals, we developed an artificial vestibular sensor composed of accelerometers and gyroscopes providing movement data of the same nature as that transduced by the otoliths and canals, respectively. Here we show that the processing of these signals based on the multisensory integration hypothesis can be successfully used to discriminate tilt from translation and that the internal model based on such processing can successfully track angular and linear displacements over short periods of time.
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Vanzi E, De Cristofaro MT, Ramat S, Sotgia B, Mascalchi M, Formiconi AR. A direct ROI quantification method for inherent PVE correction: accuracy assessment in striatal SPECT measurements. Eur J Nucl Med Mol Imaging 2007; 34:1480-9. [PMID: 17390134 DOI: 10.1007/s00259-007-0404-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Accepted: 01/19/2007] [Indexed: 11/27/2022]
Abstract
PURPOSE The clinical potential of striatal imaging with dopamine transporter (DAT) SPECT tracers is hampered by the limited capability to recover activity concentration ratios due to partial volume effects (PVE). We evaluated the accuracy of a least squares method that allows retrieval of activity in regions of interest directly from projections (LS-ROI). METHODS An Alderson striatal phantom was filled with striatal to background ratios of 6:1, 9:1 and 28:1; the striatal and background ROIs were drawn on a coregistered X-ray CT of the phantom. The activity ratios of these ROIs were derived both with the LS-ROI method and with conventional SPECT EM reconstruction (EM-SPECT). Moreover, the two methods were compared in seven patients with motor symptoms who were examined with N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) (FP-CIT) SPECT, calculating the binding potential (BP). RESULTS In the phantom study, the activity ratios obtained with EM-SPECT were 3.5, 5.3 and 17.0, respectively, whereas the LS-ROI method resulted in ratios of 6.2, 9.0 and 27.3, respectively. With the LS-ROI method, the BP in the seven patients was approximately 60% higher than with EM-SPECT; a linear correlation between the LS-ROI and the EM estimates was found (r=0.98, p=0.03). CONCLUSION The LS-ROI PVE correction capability is mainly due to the fact that the ill-conditioning of the LS-ROI approach is lower than that of the EM-SPECT one. The LS-ROI seems to be feasible and accurate in the examination of the dopaminergic system. This approach can be fruitful in monitoring of disease progression and in clinical trials of dopaminergic drugs.
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Ramat S, Leigh R, Zee D, Optican L. What clinical disorders tell us about the neural control of saccadic eye movements. Am J Ophthalmol 2007. [DOI: 10.1016/j.ajo.2007.01.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Raglione L, Ammannati F, Ramat S, Marini P, Paganini M, Molteni S, Scotto di Luzio A, Mennonna P, Sorbi S. 3.214 Nine-year follow up of bilateral stimulation of the subthalamic nucleus in advanced Parkinson's disease. Parkinsonism Relat Disord 2007. [DOI: 10.1016/s1353-8020(08)70852-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Polito C, Ramat S, De Cristofaro M, Marini P, Paganini M, Sorbi S, Pupi A. 3.116 Set-shifting deficit and fronto-temporal hypometabolism in early Parkinson's disease. Parkinsonism Relat Disord 2007. [DOI: 10.1016/s1353-8020(08)70824-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Polito C, Ramat S, Paganini M, Merli L, Marini P, Raglione L, Ammannati F, Mennonna P, Sorbi S. 3.225 Neuropsychological outcome of bilateral deep brain stimulation of the subthalamic nucleus in Parkinson's disease. Parkinsonism Relat Disord 2007. [DOI: 10.1016/s1353-8020(08)70863-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Righi S, Viggiano MP, Paganini M, Ramat S, Marini P. Recognition of category-related visual stimuli in Parkinson's disease: Before and after pharmacological treatment. Neuropsychologia 2007; 45:2931-41. [PMID: 17662314 DOI: 10.1016/j.neuropsychologia.2007.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Revised: 06/01/2007] [Accepted: 06/08/2007] [Indexed: 11/25/2022]
Abstract
Visual-sensory dysfunctions and semantic processing impairments are widely reported in Parkinson's disease (PD) research. The present study investigated the category-specific deficit in object recognition as a function of both the semantic category and spatial frequency content of stimuli. In the first experiment, the role of dopamine in object-recognition processing was assessed by comparing PD drug naïve (PD-DN), PD receiving levodopa treatment (PD-LD), and control subjects. Experiment 2 consisted of a retest session for PD drug naïve subjects after a period of pharmacological treatment. All participants completed an identification task which displayed animals and tools at nine levels of filtering. Each object was revealed in a sequence of frames whereby the object was presented at increasingly less-filtered images up to a complete version of the image. Results indicate an impaired identification pattern for PD-DN subjects solely for animal category stimuli. This differential pharmacological therapy effect was also confirmed at retest (experiment 2). Thus, our data suggest that dopaminergic loss has a specific role in category-specific impairment. Two possible hypotheses are discussed that may account for the defective recognition of semantically different objects in PD.
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