Blaž Koritnik

Imaging the brain during sniffing: a pilot fMRI study.

Whilst the act of sniffing can provide us with an indirect method to study the central mechanisms of respiratory control, functional neuroimaging now provides us with a tool to directly visualise the activity of the human brain during this voluntary action using functional magnetic resonance imaging (fMRI). We performed fMRI during sniffing in 11 healthy volunteers where all subjects executed single, brisk sniffs of around 60% of their maximum sniff pressure at intervals of approximately every 20s. Simultaneous nasal pressure and chest movements were also measured during the task and a statistical parametric map of activation correlating with the sniff manoeuvre was calculated. A bilateral cortical and subcortical sensorimotor network was activated. The activations were localised within the primary sensorimotor cortex, lateral premotor cortex, supplementary motor area, anterior cingulate, insula, basal ganglia, thalami, mesencephalon, upper pons, cerebellar vermis, piriform cortex, entorhinal cortex and parahippocampal gyrus. The activated brain areas identified, i.e. the cortical and subcortical respiratory network, are similar to those described in other neuroimaging studies of voluntary inspiration. Sniffing is a component of olfactory processing and activations of the olfaction-related cortical areas were also observed in our study. The results of our study show that event-related fMRI can be successfully used to study sniffing. This provides a novel approach to our study of the central neural control of respiration.

Genetic analysis of amyotrophic lateral sclerosis in the Slovenian population.

Amyotrophic lateral sclerosis (ALS) is a complex fatal neurodegenerative disease characterized by progressive degeneration and loss of upper motor neurons in the cerebral cortex and lower motor neurons in brainstem and spinal cord. We established the frequencies of mutations in 4 major ALS-associated genes, SOD1, TARDBP, FUS, and C9ORF72 in a representative cohort of 85 Slovenian patients with sporadic form of ALS. Pathogenic massive hexanucleotide repeat expansion mutation in C9ORF72 was detected in 5.9% of patients and was the most common cause of the disease. In the remaining 3 genes, we identified 4 changes in 3 patients, p.Val14Met in SOD1, silent mutation p.Arg522Arg in FUS, and p.Gly93Cys in SOD1 together with a novel synonymous variant c.990A>G (p.Leu330Leu) in TARDBP gene, respectively. This study represents the first genetic screening of major causative genes for ALS in a cohort of sporadic ALS patients from Slovenia and is according to our knowledge the first such study in Slavic population. Overall, we genetically characterized 8.2% sporadic ALS patients.

Gripping-force identification using EEG and phase-demodulation approach.

In this paper we investigate the fuzzy identification of brain-code during simple gripping-force control tasks. Since the synchronized oscillatory activity and the phase dynamics between the brain areas are two important mechanisms in the brains function and information transfer, we decided to examine whether it is possible to extract the encoded information from the EEG signals using the phase-demodulation approach. The EEG was measured during the performance of different visuomotor tasks and the information we were trying to decode was the gripping force as applied by the subjects. The study revealed that it is possible, by using simple beta-rhythm filtering, phase demodulation, principal component analysis and a fuzzy model, to estimate the gripping-force response by using EEG signals as the inputs for the proposed model. The presented study has shown that even though EEG signals represent a superposition of all the active neurons, it is still possible to decode some information about the current activity of the brain centers. Furthermore, the cross-validation showed that the information about the gripping force is encoded in a very similar way for all the examined subjects. Thus, the phase shifts of the EEG signals seem to have a key role during activity and information transfer in the brain, while the phase-demodulation method proved to be a crucial step in the signal processing.

Decreased movement-related beta desynchronization and impaired post-movement beta rebound in amyotrophic lateral sclerosis

OBJECTIVE This study explored event-related desynchronization (ERD) and synchronization (ERS) in amyotrophic lateral sclerosis (ALS) to quantify cortical sensorimotor processes during volitional movements. We furthermore compared ERD/ERS measures with clinical scores and movement-related cortical potential (MRCP) amplitudes. METHODS Electroencephalograms were recorded while 21 ALS patients and 19 controls performed two self-paced motor tasks: sniffing and right index finger flexion. Based on Wavelet analysis the alpha and beta frequency bands were selected for subsequent evaluation. RESULTS Patients generated significantly smaller resting alpha spectral power density (SPD) and smaller beta ERD compared to controls. Additionally patients exhibited merely unilateral post-movement ERS (beta rebound) whereas this phenomenon was bilateral in controls. ERD/ERS amplitudes did not correlate with corresponding MRCPs for either patients or controls. CONCLUSIONS The smaller resting alpha SPD and beta ERD and asymmetrical appearance of beta ERS in patients compared to controls could be the result of pyramidal cell degeneration and/or corpus callosum involvement in ALS. SIGNIFICANCE These results support the notion of reduced movement preparation in ALS involving also areas outside the motor cortex. Furthermore post-movement cortical inhibition seems to be impaired in ALS. ERD/ERS and MRCP are found to be independent measures of cortical motor functions in ALS.

Muscle activity-resistant acetylcholine receptor accumulation is induced in places of former motor endplates in ectopically innervated regenerating rat muscles

Expression of acetylcholine receptors (AChRs) in the extrajunctional muscle regions, but not in the neuromuscular junctions, is repressed by propagated electric activity in muscle fibers. During regeneration, subsynaptic‐like specializations accumulating AChRs are induced in new myotubes by agrin attached to the synaptic basal lamina at the places of former motor endplates even in the absence of innervation. We examined whether AChRs still accumulated at these places when the regenerating muscles were ectopically innervated and the former synaptic places became extrajunctional. Rat soleus muscles were injured by bupivacaine and ischemia to produce complete myofiber degeneration. The soleus muscle nerve was permanently severed and the muscle was ectopically innervated by the peroneal nerve a few millimeters away from the former junctional region. After 4 weeks of regeneration, the muscles contracted upon nerve stimulation, showed little atrophy and the cross‐section areas of their fibers were completely above the range in non‐innervated regenerating muscles, indicating successful innervation. Subsynaptic‐like specializations in the former junctional region still accumulated AChRs (and acetylcholinesterase) although no motor nerve endings were observed in their vicinity and the cross‐section area of their fibers clearly demonstrated that they were ectopically innervated. We conclude that the expression of AChRs at the places of the former neuromuscular junctions in the ectopically innervated regenerated soleus muscles is activity‐independent.

Sniffing-related motor cortical potential: topography and possible generators.

This study estimated the whole-scalp topography and possible generators of the cortical potential associated with volitional self-paced inspirations (sniffs). In 17 healthy subjects we recorded a 32-channel electroencephalogram (EEG) during sniffing, for comparison during finger flexions. We averaged the EEG with respect to movement onset, and performed current source density and principal component analysis on the grand averaged data. We identified an early negative sniffing-related cortical potential starting ∼1.5s before movement at the vertex, which, in its time-course and dipole orientation, closely resembled Bereitshaftspotential preceding finger flexions. Around the movement onset, its topography became unique with three negative current sources: one at the vertex, and two bilaterally over the fronto-temporal derivations. We conclude that sequential cortical activation in preparation for sniffing is similar to other volitional movements. The current sources at sniff onset at the vertex likely reflect somatotopic motor representation of the diaphragm, neck and intercostal muscles, whereas current sources over fronto-temporal derivations likely reflect the somatotopic representation of the orofacial muscles.

Differential expression of microRNAs and other small RNAs in muscle tissue of patients with ALS and healthy age-matched controls

Amyotrophic lateral sclerosis is a late-onset disorder primarily affecting motor neurons and leading to progressive and lethal skeletal muscle atrophy. Small RNAs, including microRNAs (miRNAs), can serve as important regulators of gene expression and can act both globally and in a tissue-/cell-type-specific manner. In muscle, miRNAs called myomiRs govern important processes and are deregulated in various disorders. Several myomiRs have shown promise for therapeutic use in cellular and animal models of ALS; however, the exact miRNA species differentially expressed in muscle tissue of ALS patients remain unknown. Following small RNA-Seq, we compared the expression of small RNAs in muscle tissue of ALS patients and healthy age-matched controls. The identified snoRNAs, mtRNAs and other small RNAs provide possible molecular links between insulin signaling and ALS. Furthermore, the identified miRNAs are predicted to target proteins that are involved in both normal processes and various muscle disorders and indicate muscle tissue is undergoing active reinnervation/compensatory attempts thus providing targets for further research and therapy development in ALS.

Movement-related cortical potentials in ALS increase at lower and decrease at higher upper motor neuron burden scores

Abstract Our aim was to investigate changes in movement-related cortical potentials (MRCPs) in ALS patients with different degrees of upper motor neuron (UMN) involvement. Since respiratory failure is the main cause of death in ALS, changes in inspiratory-related (sniffing) potentials were studied in addition to finger-flexion-related potentials. Subjects (21 ALS, 19 controls) performed two self-paced motor tasks while their EEGs were recorded. The first task required flexions of the right index finger and the second, brisk nasal inspirations. The early (BP1), late (BP2) and motor potential (MP) components of MRCPs were evaluated. Results showed that patients generated higher MRCPs than controls. However, this effect was most significant in the subgroup of patients with low UMN burden (LUB). The high UMN burden (HUB) subgroup did not differ from controls, but had significantly lower MP amplitudes than the LUB subgroup. Progressive UMN deterioration was associated with an initial increase, followed by a later decrease, in MP amplitudes in ALS. In conclusion, the increased MRCPs in LUB compared to HUB patients indicate different processes of ALS pathophysiology that force opposing changes in MRCP amplitudes.

Differential Expression of Several miRNAs and the Host Genes AATK and DNM2 in Leukocytes of Sporadic ALS Patients

Genetic studies have managed to explain many cases of familial amyotrophic lateral sclerosis (ALS) through mutations in several genes. However, the cause of a majority of sporadic cases remains unknown. Recently, epigenetics, especially miRNA studies, show some promising aspects. We aimed to evaluate the differential expression of 10 miRNAs, including miR-9, miR-338, miR-638, miR-663a, miR-124a, miR-143, miR-451a, miR-132, miR-206, and let-7b, for which some connection to ALS was shown previously in ALS culture cells, animal models or patients, and in three miRNA host genes, including C1orf61 (miR-9), AATK (miR-338), and DNM2 (miR-638), in leukocyte samples of 84 patients with sporadic ALS. We observed significant aberrant dysregulation across our patient cohort for miR-124a, miR-206, miR-9, let-7b, and miR-638. Since we did not use neurological controls we cannot rule out that the revealed differences in expression of investigated miRNAs are specific for ALS. Nevertheless, the group of these five miRNAs is worth of additional research in leukocytes of larger cohorts from different populations in order to verify their potential association to ALS disease. We also detected a significant up-regulation of the AAKT gene and down-regulation of the DNM2 gene, and thus, for the first time, we connected these with sporadic ALS cases. These findings open up new research toward miRNAs as diagnostic biomarkers and epigenetic processes involved in ALS. The detected significant deregulation of AAKT and DNM2 in sporadic ALS also represents an interesting finding. The DNM2 gene was previously found to be mutated in Charcot-Marie-Tooth neuropathy-type CMT2M and centronuclear myopathy (CNM). In addition, as recent studies connected AATK and frontotemporal dementia (FTD) and DNM2 and hereditary spastic paraplegia (HSP), these two genes together with our results genetically connect, at least in part, five diseases, including FTD, HSP, Charcot-Marie-Tooth (type CMT2M), CNM, and ALS, thus opening future research toward a better understanding of the cell biology involved in these partly overlapping pathologies.

Beyond aphasia: Altered EEG connectivity in Broca's patients during working memory task.

Brocas region and adjacent cortex presumably take part in working memory (WM) processes. Electrophysiologically, these processes are reflected in synchronized oscillations. We present the first study exploring the effects of a stroke causing Brocas aphasia on these processes and specifically on synchronized functional WM networks. We used high-density EEG and coherence analysis to map WM networks in ten Brocas patients and ten healthy controls during verbal WM task. Our results demonstrate that a stroke resulting in Brocas aphasia also alters two distinct WM networks. These theta and gamma functional networks likely reflect the executive and the phonological processes, respectively. The striking imbalance between task-related theta synchronization and desynchronization in Brocas patients might represent a disrupted balance between task-positive and WM-irrelevant functional networks. There is complete disintegration of left fronto-centroparietal gamma network in Brocas patients, which could reflect the damaged phonological loop.