| 1. |
- Anders, Silke, et al.
(author)
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When seeing outweighs feeling : a role for prefrontal cortex in passive control of negative affect in blindsight
- 2009
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In: Brain. - Oxford : Oxford University Press. - 0006-8950 .- 1460-2156. ; 132:11, s. 3021-3031
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Journal article (peer-reviewed)abstract
- Affective neuroscience has been strongly influenced by the viewthat a ‘feeling’ is the perception of somatic changesand has consequently often neglected the neural mechanisms thatunderlie the integration of somatic and other information inaffective experience. Here, we investigate affective processingby means of functional magnetic resonance imaging in nine corticallyblind patients. In these patients, unilateral postgeniculatelesions prevent primary cortical visual processing in part ofthe visual field which, as a result, becomes subjectively blind.Residual subcortical processing of visual information, however,is assumed to occur in the entire visual field. As we have reportedearlier, these patients show significant startle reflex potentiationwhen a threat-related visual stimulus is shown in their blindvisual field. Critically, this was associated with an increaseof brain activity in somatosensory-related areas, and an increasein experienced negative affect. Here, we investigated the patients’response when the visual stimulus was shown in the sighted visualfield, that is, when it was visible and cortically processed.Despite the fact that startle reflex potentiation was similarin the blind and sighted visual field, patients reported significantlyless negative affect during stimulation of the sighted visualfield. In other words, when the visual stimulus was visibleand received full cortical processing, the patients’ phenomenalexperience of affect did not closely reflect somatic changes.This decoupling of phenomenal affective experience and somaticchanges was associated with an increase of activity in the leftventrolateral prefrontal cortex and a decrease of affect-relatedsomatosensory activity. Moreover, patients who showed strongerleft ventrolateral prefrontal cortex activity tended to showa stronger decrease of affect-related somatosensory activity.Our findings show that similar affective somatic changes canbe associated with different phenomenal experiences of affect,depending on the depth of cortical processing. They are in linewith a model in which the left ventrolateral prefrontal cortexis a relay station that integrates information about subcorticallytriggered somatic responses and information resulting from in-depthcortical stimulus processing. Tentatively, we suggest that theobserved decoupling of somatic responses and experienced affect,and the reduction of negative phenomenal experience, can beexplained by a left ventrolateral prefrontal cortex-mediatedinhibition of affect-related somatosensory activity.
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| 4. |
- Buerger, Katharina, et al.
(author)
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CSF phosphorylated tau protein correlates with neocortical neurofibrillary pathology in Alzheimer's disease.
- 2006
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In: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 129:Pt 11, s. 3035-41
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Journal article (peer-reviewed)abstract
- Hyperphosphorylated tau protein (P-tau) in CSF is a core biomarker candidate of Alzheimer's disease. Hyperphosphorylation of tau is thought to lead to neurofibrillary changes, a neuropathological hallmark of this type of dementia. Currently, the question is unresolved whether CSF levels of P-tau reflect neurofibrillary changes within the brain of a patient with the illness. Twenty-six patients were included with intra-vitam CSF as well as post-mortem neuropathological data. In the CSF, P-tau phosphorylated at threonine 231 (P-tau231P) was analysed. Post-mortem, scores of neurofibrillary tangles (NFT) and neuritic plaques (NP) were assessed in frontal, temporal, parietal and hippocampal cortical areas. In the same cortical regions, load of hyperphosphorylated tau protein (HP-tau load) was determined. Concentrations of P-tau231P were measured in frontal cortex homogenates. We found significant correlations between CSF P-tau231P concentrations and scores of NFTs and HP-tau load in all neocortical regions studied. The score of NPs was correlated with CSF P-tau231P only within the frontal cortex. There was a correlation between P-tau231P in CSF and brain homogenates. These findings indicate that CSF P-tau231P may serve as an in vivo surrogate biomarker of neurofibrillary pathology in Alzheimer's disease.
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| 6. |
- Carlsson, Thomas, et al.
(author)
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Impact of grafted serotonin and dopamine neurons on development of L-DOPA-induced dyskinesias in parkinsonian rats is determined by the extent of dopamine neuron degeneration.
- 2009
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In: Brain. - : Oxford University Press (OUP). - 1460-2156 .- 0006-8950. ; 132, s. 319-335
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Journal article (peer-reviewed)abstract
- Previous studies have shown that serotonin neurons play an important role in the induction and maintenance of l-DOPA-induced dyskinesia in animals with lesion of the nigrostriatal dopamine system. Patients with Parkinson's disease that receive transplants of foetal ventral mesencephalic tissue, the graft cell preparation is likely to contain, in addition to dopamine neurons, serotonin neurons that will vary in number depending on the landmarks used for dissection. Here, we have studied the impact of grafted serotonin neurons-alone or mixed with dopamine neurons-on the development of l-DOPA-induced dyskinesia in rats with a partial 6-hydroxydopamine lesion of the host nigrostriatal projection. In these rats, which showed only low-level dyskinesia at the time of transplantation, serotonin grafts induced a worsening in the severity of dyskinesia that developed during continued l-DOPA treatment, while the dopamine-rich graft had the opposite, dampening effect. The detrimental effect seen in animals with serotonin neuron grafts was dramatically increased when the residual dopamine innervation in the striatum was removed by a second 6-hydroxydopamine lesion. Interestingly, rats with grafts that contained a mixture of dopamine and serotonin neurons (in approximately 2:1) showed a marked reduction in l-DOPA-induced dyskinesia over time, and the appearance of severe dyskinesia induced by the removal of the residual dopamine innervation, seen in the animals with transplants of serotonin neurons alone, was blocked. FosB expression in the striatal projection neurons, which is associated with dyskinesias, was also normalized by the dopamine-rich grafts, but not by the serotonin neuron grafts. These data indicate that as long as a sufficient portion, some 10-20%, of the dopamine innervation still remains, the increased host serotonin innervation generated by the grafted serotonin neurons will have limited effect on the development or severity of l-DOPA-induced dyskinesias. At more advanced stages of the disease, when the dopamine innervation of the putamen is reduced below this critical threshold, grafted serotonin neurons are likely to aggravate l-DOPA-induced dyskinesia in those cases where the dopamine re-innervation derived from the grafted neurons is insufficient in magnitude or do not cover the critical dyskinesia-inducing sub-regions of the grafted putamen. We conclude that it is not the absolute number of serotonin neurons in the grafts, but the relative densities of dopamine and serotonin innervations in the grafted striatum that is the critical factor in determining the long-term effect of foetal tissue graft, beneficial or detrimental, on dyskinesia in grafted Parkinson's disease patients.
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| 7. |
- Carlsson, Thomas, et al.
(author)
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Reversal of dyskinesias in an animal model of Parkinson's disease by continuous L-DOPA delivery using rAAV vectors.
- 2005
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In: Brain. - : Oxford University Press (OUP). - 1460-2156. ; 128:3, s. 559-569
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Journal article (peer-reviewed)abstract
- Dyskinesias are a major complication of long-term l-3,4-dihydroxyphenylalanine (L-DOPA) treatment in Parkinson's disease, and are believed to result from the intermittent and pulsatile supply of L-DOPA. Daily injections of L-DOPA can prime similar abnormal involuntary movements of the limb, orolingual and axial muscles in rats rendered parkinsonian by destruction of the nigrostriatal dopamine (DA) neurons. In this study we used 33 rats with severe nigrostriatal dopamine depletion and showed that in vivo gene transfer of the DA-synthetic enzymes tyrosine hydroxylase (TH) and GTP cyclohydrolase 1 (GCH1) using recombinant adeno-associated virus vectors can provide a constant source of DOPA production locally in the striatum, at a level that is effective in reducing L-DOPA-induced dyskinesias by >85%, and reverse lesion-induced motor impairments. Furthermore, the abnormal expression of DeltaFosB, prodynorphin and preproenkephalin mRNA within the striatal projection neurons normally seen in dyskinetic animals was completely reversed by TH-GCH1 gene transfer. These findings form a strong basis for replacing, or supplementing, conventional systemic L-DOPA therapy by continuous intrastriatal DOPA using in vivo gene transfer in the treatment of patients with advanced Parkinson's disease.
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| 8. |
- Carta, Manolo, et al.
(author)
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Dopamine released from 5-HT terminals is the cause of L-DOPA-induced dyskinesia in parkinsonian rats.
- 2007
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In: Brain. - : Oxford University Press (OUP). - 1460-2156 .- 0006-8950. ; 130:7, s. 1819-1833
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Journal article (peer-reviewed)abstract
- n patients with Parkinson's disease, the therapeutic efficacy of L-DOPA medication is gradually lost over time, and abnormal involuntary movements, dyskinesias, gradually emerge as a prominent side-effect in response to previously beneficial doses of the drug. Here we show that dyskinesia induced by chronic L-DOPA treatment in rats with 6-hydroxydopamine-induced lesions of the nigrostriatal dopamine pathway is critically dependent on the integrity and function of the serotonergic system. Removal of the serotonin afferents, or dampening of serotonin neuron activity by 5-HT1A and 5-HT1B agonist drugs, resulted in a near-complete block of the L-DOPA-induced dyskinesias, suggesting that dysregulated dopamine release from serotonin terminals is the prime trigger of dyskinesia in the rat Parkinson's disease model. In animals with complete dopamine lesions, the spared serotonin innervation was unable to sustain the therapeutic effect of L-DOPA, suggesting that dopamine released as a 'false transmitter' from serotonin terminals is detrimental rather than beneficial. The potent synergistic effect of low doses of 5-HT1A and 5-HT1B agonists to suppress dyskinesia, without affecting the anti-parkinsonian effect of L-DOPA in presence of spared dopamine terminals, suggests an early use of these drugs to counteract the development of dyskinesia in Parkinson's disease patients.
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| 9. |
- Cervenka, Simon, et al.
(author)
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Support for dopaminergic hypoactivity in restless legs syndrome : a PET study on D2-receptor binding
- 2006
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In: Brain. - Karolinska Univ Hosp Solna, Dept Clin Neurosci, Psychol Sect, Karolinska Inst, SE-17176 Stockholm, Sweden. Karolinska Univ Hosp Huddinge, Div Clin Pharmacol, Dept Lab Med, Stockholm, Sweden. Karolinska Univ Hosp Huddinge, Dept Neurol, Stockholm, Sweden. GlaxoSmithKline Inc, Translat Med & Genet, Cambridge, England. Univ Manchester, Wolfson Mol Imaging Ctr, Manchester, Lancs, England. GlaxoSmithKline Inc, Neurol Discovery Med, Harlow, Essex, England. : OXFORD UNIV PRESS. - 0006-8950 .- 1460-2156. ; 129, s. 2017-2028
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Journal article (peer-reviewed)abstract
- Clinical observations support a central role of the dopamine system in restless legs syndrome (RLS) but previous imaging studies of striatal dopamine D2-receptors have yielded inconclusive results. Extrastriatal dopaminergic function has hitherto not been investigated. Sixteen RLS patients naive to dopaminergic drugs and sixteen matched control subjects were examined with PET. [C-11]Raclopride and [C-11]FLB 457 were used to estimate D2-receptor availability in striatum and extrastriatal regions, respectively. Examinations were performed both in the morning (starting between 10:00 and 12:00 h) and evening (starting at 18:00 h). Measures were taken to monitor and control for head movement during data acquisition. In the striatum, patients had significantly higher [C-11]raclopride binding potential (BP) values than controls. In extrastriatal regions, [C-11]FLB 457 BP was higher in patients than controls, and in the regional analysis the difference was statistically significant in subregions of thalamus and the anterior cingulate cortex. The diurnal variability in BP with [C-11]FLB 457 and [C-11]raclopride was within the previously reported test-retest reproducibility for both radioligands. The study supports involvement of the dopamine system in both striatal and extrastriatal brain regions in the pathophysiology of RLS. The brain regions where differences in D2-receptor binding were shown are implicated in the regulation of affective and motivational aspects of sensory processing, suggesting a possible pathway for sensory symptoms in RLS. Increased D2-receptor availability in RLS may correspond to higher receptor densities or lower levels of endogenous dopamine. Both interpretations are consistent with the hypothesis of hypoactive dopaminergic neurotransmission in RLS, as increased receptor levels can be owing to receptor upregulation in response to low levels of endogenous dopamine. The results do not support variations in dopamine D2-receptor availability as a correlate to the diurnal rhythm of RLS symptoms.
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