Biology subjects

Karunanayaka, P.

Publications and source records attributed to Karunanayaka, P..

3 recordsLinked to original sources

bioRxiv2021

IMPAIRED OLFACTORY NETWORK FUNCTIONAL CONNECTIVITY IN PARKINSON'S DISEASE: A NOVEL MARKER FOR DISEASE PROGRESSION

ObjectiveDetermine the neural basis of olfactory impairment in akinetic-rigid (PDAR) and tremor predominant (PDT) Parkinsons disease subtypes. MethodsWe combined resting-state fMRI (rs-fMRI) with seed based functional connectivity (FC) in order to delineate the olfactory networks functional connectivity (ON FC) between PDAR and PDT patients. We then contrasted their ON FC patterns with cognitively normal (CN) subjects. All three groups were closely matched in age, demographic variables, and adjusted for relative cognitive performance. Olfactory function was measured using the University of Pennsylvania Smell Identification Test (UPSIT). ResultsUPSIT scores were lower in akinetic-rigid vs tremor subtypes; ON FC values were lower in PDAR compared to PDT and CN, and followed the trend observed in UPSIT scores. UPSIT scores and ON FC values were significantly correlated, reflecting the effects of PD pathologies. ConclusionsThe results show that olfactory function differs between PDAR and PDT suggesting a correlation between PD-related motor symptoms and olfactory deficits. ON FC differences accounts for the impaired olfactory functions observed between PDAR and PDT. PDAR is known to have worse clinical outcomes and faster cognitive decline compared to PDT; therefore, PD-related olfactory dysfunction may serve as a novel metric for enhancing PD prognosis.

neuroscience↗

bioRxiv2020

Neural Basis of Olfactory and Trigeminal Integration

Humans naturally integrate signals from the olfactory and intranasal trigeminal systems. A tight interplay has been demonstrated between these two systems, and yet the underlying neural circuitry that mediates olfactory-trigeminal integration remains poorly understood. Using functional magnetic resonance imaging (fMRI), combined with psychophysics, this study investigated the neural mechanisms underlying olfactory-trigeminal integration. Fifteen participants with normal olfactory function performed a localization task with air-puff stimuli, phenylethyl alcohol (PEA; rose odor), or a combination thereof while being scanned. The ability to localize PEA to either nostril was at chance. Yet, its presence significantly improved the localization accuracy of weak, but not strong, air-puffs, relative to air-puff localization without concomitant PEA when both stimuli were delivered concurrently to the same nostril, but not when different nostrils received the two stimuli. This enhancement in localization accuracy, exemplifying the principles of spatial coincidence and inverse effectiveness in multisensory integration, was associated with multisensory integrative activity in the primary olfactory (POC), orbitofrontal (OFC), superior temporal (STC), inferior parietal (IPC) and cingulate cortices, and in the cerebellum. Multisensory enhancement in most of these regions, except the OFC, correlated with behavioral multisensory enhancement, as did increases in connectivity between some of these regions. We interpret these findings as indicating that the POC is part of a distributed brain network mediating integration between the olfactory and trigeminal systems. HIGHLIGHTSO_LIPsychophysical and neuroimaging study of olfactory-mechanosensory (OM) integration C_LIO_LIBehavior, cortical activity and network connectivity show OM integration C_LIO_LIOM integration obeys principles of inverse effectiveness and spatial coincidence C_LIO_LIBehavioral and neural measures of OM integration are correlated C_LI

neuroscience↗

bioRxiv2020

18F-FDG-PET Hyperactivity in Alzheimers Disease Cerebellum and Primary Olfactory Cortex

Cerebellar involvement in Alzheimers disease (AD) has not been studied to the extent that cortical neuropathological changes have. Historical and recent histopathological literature demonstrate cerebellar AD pathology while functional investigation has demonstrated disrupted intrinsic cortical - cerebellar connectivity in AD. Additionally, olfactory deficits occur early in AD, prior to the onset of clinical symptoms. The neurological basis for the involvement of the cerebellum and olfactory system in the disease course remain unclear. 18F-fludeoxyglucose (FDG) positron emission tomography (PET) data from the Alzheimers Disease Neuroimaging Initiative (ADNI) were analyzed to characterize metabolism in the cerebellum and olfactory region of AD, mild-cognitive impaired (MCI), and age-matched cognitively normal (CN) controls. In contrast to known parietal and temporal lobe FDG hypo-metabolism within the default mode network in AD, a significant FDG hyper-metabolism was found in the cerebellum and olfactory cortical regions (including the piriform cortex, olfactory tubercle, anterior olfactory nucleus, and nucleus accumbens shell). The increase in cerebellum glucose utilization was shown also in late- verses early-MCI patients. The cerebellar and olfactory regions both contain inhibitory distal and inter-neuronal connections that are vulnerable to disruption in AD. The hyper-metabolism in the cerebellum and olfactory structures may reflect disruption of local and system-wide inhibitory networks due to AD neurodegeneration, suggesting a hypothetical mechanism for susceptibility of the olfactory system to early AD pathology.

neuroscience↗