Biomedical subjects

Mandar S Jog

Publications and source records attributed to Mandar S Jog.

11 recordsLinked to original sources

PubMed2006

Building spike representation in tetrodes.

This paper presents a new technique for analyzing the recorded information from tetrodes in freely behaving rats, based on independent component analysis (ICA). The ion-specific pumps and channels allow fast transfer of charges such as Na+, K+, Cl- and eventually Ca2+ during each action potential (AP). These groups of charges under an electrical field have distinct spatial trajectories. Therefore, the generated signals within a tetrode are considered to be composed mainly by statistically independent signal sources that can be obtained by performing ICA. In order to compute the position of independent sources during AP generation, the triangulation method uses an iterative Newton-Raphson algorithm. The representation of the independent signal sources in three-dimensional tetrode space is then obtained. Since the charge movements are extensively spread on the neuron's surface, the representation in tetrode space reveals electrical spatial patterns of activation during each AP. The analysis of several spikes coming from the same neuron reveals small changes from spike to spike in the 3D shape. Since information within spikes is highly transferred by ionic fluxes these electrical patterns of activation reflect neuronal computation occurring during each AP.

Action Potentials↗

PubMed2005

Computing spike directivity with tetrodes.

The ability of neurons to generate electrical signals is strongly dependent on the evolution of ion-specific pumps and channels that allow the transfer of charges under the influence of electric fields and concentration gradients. This paper presents a novel method by which flow of these charge fluxes may be computed to provide directivity of charge movement. Simulations of charge flow as well as actual electrophysiological data recorded by tetrodes are used to demonstrate the method. The propagation of charge fluxes in space in data from simulation and actual recordings during action potential can be analyzed using signals recorded by tetrodes. Variation in spike directivity can be estimated by computing singular value decomposition of the estimated 3D trajectory data. The analysis of the spike model can be accomplished by performing simulations of presumed equivalent moving charges recorded by the tetrode tips. For in vivo spike recordings, the variation of spike directivity could be obtained using several spikes of selected neurons considering the charge movement model (CMM). The relationship between computer simulation results and tetrode data recordings is examined. The paper concludes by showing that the method for calculating directivity in actual spike recordings is robust. The method allows for improved filtering of data and more importantly may shed light on furthering the study of spatio-temporal encoding in neurons.

Action Potentials↗

PubMed2005

Spike source localization with tetrodes.

The paper presents in detail a method for approximating the spatial position of neural spike activity from tetrode recordings. The method uses a nonlinear mapping of a set of tetrode tip amplitudes into three-dimensional (3D) space, followed by a self-organizing map clustering technique. Viewed as a spike sorting method, it performs better than tetrode peak amplitudes and it is roughly equivalent with amplitude ratios. The technique's appeal to physical location may be of advantage in many investigations.

Action Potentials↗

PubMed2005

Memory perception and strategy use in Parkinson's disease.

Although there is growing support for the existence of memory deficits within Parkinson's disease (PD), little has been done to evaluate the extent to which PD patients demonstrate differences in their use of metacognitive strategies. In the present study, 79 PD patients (46 men and 33 women) and 49 age-matched healthy participants (19 men and 30 women) were compared on a metamemory questionnaire. PD patients reported significantly less strategy-use than age-matched controls, particularly with regards to external memory strategies (such as making lists). This suggests that auxiliary treatments such as memory strategy training might be effective in this population.

Adaptation, Psychological↗

PubMed2004

Screening for Parkinson's disease with response time batteries: a pilot study.

BACKGROUND: Although significant response time deficits (both reaction time and movement time) have been identified in numerous studies of patients with Parkinson's disease (PD), few attempts have been made to evaluate the use of these measures in screening for PD. METHODS: Receiver operator characteristic curves were used to identify cutoff scores for a unit-weighted composite of two choice response tasks in a sample of 40 patients and 40 healthy participants. These scores were then cross-validated in an independent sample of 20 patients and 20 healthy participants. RESULTS: The unit-weighted movement time composite demonstrated high sensitivity (90%) and specificity (90%) in the identification of PD. Movement time was also significantly correlated (r = 0.59, p < 0.025) with the motor score of the Unified Parkinson's Disease Rating Scale (UPDRS). CONCLUSIONS: Measures of chronometric speed, assessed without the use of biomechanically complex movements, have a potential role in screening for PD. Furthermore, the significant correlation between movement time and UPDRS motor score suggests that movement time may be useful in the quantification of PD severity.

Aged↗

PubMed2004

Visual inspection time in Parkinson's disease: deficits in early stages of cognitive processing.

Inspection time (IT) is a simple information processing paradigm dependent on a participant's ability to identify physical properties of a stimulus presented for a specified time interval. In contrast with reaction time (RT) studies, the dependent variable of interest in IT is not related to the motoric speed with which the individual is able to respond, but rather the minimum presentation time necessary for participants to reliably identify physical properties of the stimulus. It is well documented that individuals with Parkinson's disease (PD) experience significant impairment on tests of simple RT, but it is unclear whether such deficits can be interpreted as 'pure' slowness of information processing, or a delay in the selection and output of a motor response. In the first experiment described here, a sample of 'optimally medicated' PD patients was compared with an age-matched control group, on an IT task. Results of this experiment suggested that individuals with PD required significantly longer stimulus presentation times than healthy participants. The second experiment compared a sample of PD patients (tested both "ON" and "OFF" their typical dopaminergic medications), with an age-matched control group, on the same test of IT. Results again indicated a significant IT deficit in participants with PD, and suggested that these deficits do not significantly resolve with levodopa treatment. Overall, the results of these two experiments suggest that information processing deficits associated with PD are distinct from motor impairment. These findings are further discussed in terms of existing neurochemical models of information processing ability.

Adult↗

PubMed2003

Fear of falling and postural control in Parkinson's disease.

This study investigated the relationship between fear of falling (FOF) and qualitative and quantitative postural control in Parkinson's disease (PD). Fifty-eight nondemented PD patients were studied along with age-matched healthy controls. The degree of FOF was estimated using the Activities-specific Balance Confidence scale. Qualitative postural control was evaluated using a component of the Unified Parkinson Disease Rating Scale. Postural control was quantified, using centre of pressure measures obtained from a force plate, for eight standing balance tests of different challenges. The results showed that FOF was more evident for PD patients when compared with healthy individuals of similar age. Furthermore, FOF was significantly associated with a qualitative estimate of postural control in PD; individuals with PD who had a greater degree of posture impairment reported greater FOF. The results also showed that an estimate of FOF may help to explain quantitative postural instability in PD. FOF, when coupled with a qualitative estimate of postural control, was able to explain a greater amount of variation in quantitative balance performance for five of the eight balance tests. When considered independently, the qualitative measure of postural control, in general, could not well predict quantitative balance performance. The greater degree of FOF and its possible association with altered postural control suggests that FOF should be considered as an important, independent risk factor in the assessment and treatment of postural instability in patients with PD.

Accidental Falls↗

PubMed2003

Unique form of propriospinal myoclonus as a possible complication of an enteropathogenic toxin.

Propriospinal myoclonus is an uncommon form of spinal myoclonus propagated, presumably, by slowly conducting polysynaptic intraspinal pathways. Although most patients demonstrate no clear etiology, a variety of disorders have been linked to this abnormal movement, including trauma, multiple sclerosis, tumors, and infectious disorders such as herpes zoster, human immunodeficiency virus, and Lyme disease. We describe 2 young male patients from the same town in Northern Ontario, Canada, exposed to an outbreak of Escherichia coli O157:H7 from contaminated municipal water, who developed identical clinical and electrophysiological features suggestive of a rhythmic form of propriospinal myoclonus with activity alternating between abdominal and paraspinal muscles. A toxin-mediated microvascular thrombosis is proposed as a possible pathogenic mechanism underlying this novel association.

Adult↗

PubMed2003

A role of the basal ganglia in movement: the effect of precues on discrete bi-directional movements in Parkinson's disease.

The effect of a precue on improving movement initiation (i.e., reaction time; RT) is well understood, whereas its influence on movement execution (i.e., movement time; MT) has rarely been examined. The current study investigated the influence of a directional precue (i.e., left vs. right) on the RT and MT of simple and discrete bi-directional movements in a large sample of Parkinson's disease patients and healthy control participants. Both patients and controls were tested twice, with testing sessions separated by 2 hours. Patients were tested first following an overnight levodopa withdrawal and again after they had taken their medication. Both patients and controls demonstrated a significant RT improvement when information was provided in advance. MT in both healthy participants and medicated patients was, however, slower with the provision of advance information, while unmedicated patients showed no significant MT effects. These results suggest that while the basal ganglia may not be involved in motor program selection, they may dynamically modulate movement execution.

Adult↗

PubMed2002

Sublingual atropine for sialorrhea secondary to parkinsonism: a pilot study.

Sialorrhea is a relatively common symptom in idiopathic Parkinson's disease and related conditions for which most of the accepted treatments are either highly invasive or may cause substantial systemic side effects. This study describes an open-label pilot study of sublingual atropine drops for the treatment of sialorrhea in 7 patients (6 with Parkinson's disease, 1 with progressive supranuclear palsy). Participants demonstrated statistically significant declines in saliva production, both objectively and subjectively. Self-reported drooling severity showed a significant decline between baseline and 180 minutes, t(6) = 3.240 P < 0.025 (eta(2) = 0.636), and between baseline and 1 week, t(6) = 4.583 P < 0.005 (eta(2) = 0.778). Objectively measured saliva production decreased significantly between baseline and the 1-week follow-up, t(6) = 2.711 P < 0.05 (eta(2) = 0.551). Delirium occurred in 1 patient (concurrent with a urinary tract infection), and 2 patients experienced worsening of hallucinations (active hallucinosis was concealed by both individuals to allow participation in the trial). The remaining trial participants did not experience any anticholinergic side effects. This trial shows that, in selected patient populations, sublingual atropine is a simple and inexpensive treatment for sialorrhea associated with parkinsonism.

Administration, Sublingual↗

PubMed2002

Hemiparkinsonism-somatic hemiatrophy syndrome.

PURPOSE: This paper highlights the hemiparkinsonism-hemiatrophy (HPHA) syndrome as a unique presentation of the parkinsonian state. Clinically relevant diagnostic and treatment aspects are reviewed. METHOD: We report a case of HPHA, in a 21-year-old, otherwise healthy, woman. Clinical and radiographic features of our case are presented. We also review the current literature on the clinical, radiological and pathophysiological mechanisms of HPHA. RESULTS: In our case, despite the lack of benefit from anticholinergics and dopamine agonists (the patient declined treatment with levodopa), the patient showed a dramatic improvement with subthalamic nucleus stimulator (STN) implantation. There are no reported cases of use of STN stimulator in HPHA. CONCLUSION: Hemiparkinsonism-hemiatrophy is a distinct entity that may be clinically and pathogenetically different from idiopathic Parkinson's disease; hence, HPHA needs to be considered as a possible syndrome in patients that have persistent unilateral parkinsonism. As medications are reported to be unhelpful in HPHA cases, early surgical intervention may be an option, such as in our case.

Adult↗