Anne Marthe Meppelink

Visual Object Recognition and Attention in Parkinson's Disease Patients with Visual Hallucinations

Visual hallucinations (VH) are common in Parkinsons disease (PD) and are hypothesized to be due to impaired visual perception and attention deficits. We investigated whether PD patients with VH showed attention deficits, a more specific impairment of higher order visual perception, or both. Forty‐two volunteers participated in this study, including 14 PD patients with VH, 14 PD patients without VH and 14 healthy controls (HC), matched for age, gender, education level and for level of executive function. We created movies with images of animals, people, and objects dynamically appearing out of random noise. Time until recognition of the image was recorded. Sustained attention was tested using the Test of Attentional Performance. PD patients with VH recognized all images but were significantly slower in image recognition than both PD patients without VH and HC. PD patients with VH showed decreased sustained attention compared to PD patients without VH who again performed worse than HC. In conclusion, the recognition of objects is intact in PD patients with VH; however, these patients where significantly slower in image recognition than patients without VH and HC, which was not explained by executive dysfunction. Both image recognition speed and sustained attention decline in PD, in a more progressive way if VH start to occur.

Regional cortical grey matter loss in Parkinson's disease without dementia is independent from visual hallucinations.

In our previous functional magnetic resonance imaging study, Parkinsons disease (PD) patients with visual hallucinations (VH) showed reduced activations in ventral/lateral visual association cortices preceding image recognition, compared with both PD patients without VH and healthy controls. The primary aim of the current study was to investigate whether functional deficits are associated with grey matter volume changes. In addition, possible grey matter differences between all PD patients and healthy controls were assessed. By using 3‐Tesla magnetic resonance imaging (MRI) and voxel‐based morphometry (VBM), we found no differences between PD patients with (n = 11) and without VH (n = 13). However, grey matter decreases of the bilateral prefrontal and parietal cortex, left anterior superior temporal, and left middle occipital gyrus were found in the total group of PD patients, compared with controls (n = 14). This indicates that previously demonstrated functional deficits in PD patients with VH are not associated with grey matter loss. The strong left parietal reduction in both nondemented patient groups was hemisphere specific and independent of the side of PD symptoms.

Attentional and perceptual impairments in Parkinson's disease with visual hallucinations☆

Visual hallucinations (VH) are common in Parkinsons Disease (PD). Both deficits of perception and attention seem to play a role in the pathogenesis of VH in PD. However, the possible coexistence of impairments in attention and visual perception in PD with VH is not known. This study investigated both attention and visual perception in non-demented PD patients with VH, compared to PD patients without VH and healthy controls. Fourteen participants were included in each group. All patients were assessed with sustained visual attention and object and space perception tests. Only PD patients with VH showed impairments on object and space perception. In addition, PD patients with and without VH showed impairments on sustained visual attention, being more severely affected in PD patients with VH. Only in PD patients with VH sustained visual attention was associated with a decreased object and space perception. The results of our study thus suggest that in PD patients with VH an impairment of object and space perception, possibly in association with a decreased sustained visual attention, might play a role in the pathogenesis of VH.

Transcutaneous Port for Continuous Duodenal Levodopa/Carbidopa Administration in Parkinson's Disease

Motor fluctuations in Parkinsons disease (PD) can be reduced by intraduodenal infusion of levodopa‐carbidopa (Duodopa®) via percutaneous endoscopic gastrojejunostomy (PEG). We applied the transcutaneous soft‐tissue anchored titanium port (T‐port) in 15 PD patients with motor fluctuations; 7 Duodopa‐naive (non‐PEG), and 8 previously receiving Duodopa (former‐PEG). Motor scores (UPDRS‐III) and quality of life (QOL, PDQ‐8) were assessed at baseline and 6 month follow‐up. Six patients had local irritation shortly after implantation, persisting in one patient at 6 month follow‐up, which led to explantation. After having finished the protocol, four T‐ports were explanted in total. UPDRS‐III and PDQ‐8 scores improved moderately in the non‐PEG patients, but remained similar in the former‐PEG users. Two former‐PEG users developed polyneuropathy. No obstructions, retractions, or leakages occurred. Technical and hygienic properties of the T‐port were preferred by most patients. The T‐port seems to be suitable for most PD patients qualifying for Duodopa therapy, although local infection may lead to explantation during longer‐term follow‐up.

The effects of Apomorphine on Visual Perception in Patients With Parkinson Disease and Visual Hallucinations. A pilot study

Visual hallucinations (VHs) often occur in patients with advanced Parkinson disease (PD). Overstimulation of dopamine receptors has been considered as one of the causes for VHs in PD. However, several clinical studies suggested that apomorphine infusion did not worsen existing VHs in PD, but could even improve VHs in some PD patients. This pilot study included 4 PD patients with VHs, who were examined before, during, and after an intravenous infusion with apomorphine. The examinations included tests for lower- and higher-order visual functions, attention, and motor functions. Apomorphine had a significantly positive effect on contrast sensitivity and showed a significantly negative effect on attention. These results may explain why apomorphine is able to improve VHs in PD in some patients with mainly visual perceptive problems, but may also worsen VHs in other patients because of impaired attention.

Lasting visual hallucinations in visual deprivation; fMRI correlates and the influence of rTMS

### Clinical symptomatology A blind, otherwise healthy female (50 years old) was referred to our hospital with visual complaints concerning ongoing sensations of colour and movement. She had suffered from bilateral eye disease (retinopathy), resulting in irreversible blindness 22 years ago. Ever since, she perceived visual sensations in the entire visual field, consisting of changing colours and a semitransparent flow. The movement sensations showed a regular cyclic pattern: changing direction every 2 days, being slow when directed to the right and fast when directed to the left. In particular, the first day with flow to the left was very disturbing. One year after the start of the visual sensations, both eyes were removed and replaced by prostheses, which of course had no effect on the visual sensations. Antiepileptic and antipsychotic drugs had no effect either. An equivalent of Charles Bonnet syndrome is suggested.1 ### F18-fluorodeoxyglucose positron emission tomography and functional magnetic resonance imaging F18-fluorodeoxyglucose positron emission tomography (FDG-PET) and functional magnetic resonance imaging (fMRI) were performed to gain a further insight in mechanisms underlying these visual sensations and to define a possible focus for therapeutic rTMS. Cerebral FDG-PET showed bilaterally reduced occipital-, superior parietal and thalamic metabolism (figure 1A). Using fMRI, we localised brain regions specifically involved in either visual motion or colour perception, by verbally instructing the patient to focus attention to either colour or movement. In a …

Task-specific dystonia : pathophysiology and management

Task-specific dystonia is a form of isolated focal dystonia with the peculiarity of being displayed only during performance of a specific skilled motor task. This distinctive feature makes task-specific dystonia a particularly mysterious and fascinating neurological condition. In this review, we cover phenomenology and its increasingly broad-spectrum risk factors for the disease, critically review pathophysiological theories and evaluate current therapeutic options. We conclude by highlighting the unique features of task-specific dystonia within the wider concept of dystonia. We emphasise the central contribution of environmental risk factors, and propose a model by which these triggers may impact on the motor control of skilled movement. By viewing task-specific dystonia through this new lens which considers the disorder a modifiable disorder of motor control, we are optimistic that research will yield novel therapeutic avenues for this highly motivated group of patients.

Lateral and Medial Ventral Occipitotemporal Regions Interact During the Recognition of Images Revealed from Noise

Several studies suggest different functional roles for the medial and the lateral sections of the ventral visual cortex in object recognition. Texture and surface information is processed in medial sections, while shape information is processed in lateral sections. This begs the question whether and how these functionally specialized sections interact with each other and with early visual cortex to facilitate object recognition. In the current research, we set out to answer this question. In an fMRI study, 13 subjects viewed and recognized images of objects and animals that were gradually revealed from noise while their brains were being scanned. We applied dynamic causal modeling (DCM)—a method to characterize network interactions—to determine the modulatory effect of object recognition on a network comprising the primary visual cortex (V1), the lingual gyrus (LG) in medial ventral cortex and the lateral occipital cortex (LO). We found that object recognition modulated the bilateral connectivity between LG and LO. Moreover, the feed-forward connectivity from V1 to LG and LO was modulated, while there was no evidence for feedback from these regions to V1 during object recognition. In particular, the interaction between medial and lateral areas supports a framework in which visual recognition of objects is achieved by networked regions that integrate information on image statistics, scene content and shape—rather than by a single categorically specialized region—within the ventral visual cortex.

Abnormal beta power is a hallmark of explicit movement control in functional movement disorders

Objective To determine whether sensorimotor beta-frequency oscillatory power is raised during motor preparation in patients with functional movement disorders (FMD) and could therefore be a marker of abnormal “body-focused” attention. Methods We analyzed motor performance and beta-frequency cortical oscillations during a precued choice reaction time (RT) task with varying cue validity (50% or 95% congruence between preparation and go cues). We compared 21 patients with FMD with 13 healthy controls (HCs). Results In HCs, highly predictive cues were associated with faster RT and beta desynchronization in the contralateral hemisphere (contralateral slope −0.045 [95% confidence interval (CI) −0.057 to −0.033] vs ipsilateral −0.033 [95% CI −0.046 to −0.021], p < 0.001) and with a tendency for reaching lower contralateral end-of-preparation beta power (contralateral −0.482 [95% CI −0.827 to −0.137] vs ipsilateral −0.328 [95% CI −0.673 to 0.016], p = 0.069). In contrast, patients with FMD had no improvement in RTs with highly predictive cues and showed an impairment of beta desynchronization and lateralization before movement. Conclusions Persistent beta synchronization during motor preparation could reflect abnormal explicit control of movement in FMD. Excessive attention to movement itself rather than the goal might maintain beta synchronization and impair performance.

Improving neurophysiological biomarkers for functional myoclonic movements

Introduction Differentiating between functional jerks (FJ) and organic myoclonus can be challenging. At present, the only advanced diagnostic biomarker to support FJ is the Bereitschaftspotential (BP). However, its sensitivity is limited and its evaluation subjective. Recently, event related desynchronisation in the broad beta range (13–45 Hz) prior to functional generalised axial (propriospinal) myoclonus was reported as a possible complementary diagnostic marker for FJ. Here we study the value of ERD together with a quantified BP in clinical practice. Methods Twenty-nine patients with FJ and 16 patients with cortical myoclonus (CM) were included. Jerk-locked back-averaging for determination of the ‘classical’ and quantified BP, and time-frequency decomposition for the event related desynchronisation (ERD) were performed. Diagnostic gain, sensitivity and specificity were obtained for individual and combined techniques. Results We detected a classical BP in 14/29, a quantitative BP in 15/29 and an ERD in 18/29 patients. At group level we demonstrate that ERD in the broad beta band preceding a jerk has significantly higher amplitude in FJ compared to CM (respectively −0.14 ± 0.13 and +0.04 ± 0.09 (p < 0.001)). Adding ERD to the classical BP achieved an additional diagnostic gain of 53%. Furthermore, when combining ERD with quantified and classical BP, an additional diagnostic gain of 71% was achieved without loss of specificity. Conclusion Based on the current findings we propose to the use of combined beta ERD assessment and quantitative BP analyses in patients with a clinical suspicion for all types of FJ with a negative classical BP.