The imprint of action: Motor cortex involvement in visual perception of handwritten letters

Humans are able to recognize handwritten texts accurately despite the extreme variability of scripts from one writer to another. This skill has been suggested to rely on the observer's own knowledge about implicit motor rules involved in writing. To investigate the possible neural correlates of such an ability, we monitored with magnetoencephalography (MEG) the approximately 20-Hz oscillations originating from the motor cortex. The oscillations were more suppressed after visual presentation of handwritten than printed letters, indicating stronger excitation of the motor cortex to handwritten scripts. These results support the idea of embodied visual perception of handwritten scripts and the involvement of the motor cortex in the underlying action-perception link.

Neuromagnetic responses to vowels vs. tones reveal hemispheric lateralization

OBJECTIVE

To evaluate whether a simple auditory paradigm could demonstrate a difference in cortical lateralization between right- and left-handed subjects. Such information would be important for later development of clinical noninvasive tests of hemispheric language dominance in candidates for brain surgery.

METHODS

Healthy subjects (10 strongly right-handed, 10 strongly left-handed, 5 weakly right-handed, and two ambidextrous) listened to binaural pairs of tones and pairs of Finnish vowels and decided whether the items in the pair were the same (target probability 20%). Cortical responses were recorded with whole-scalp magnetoencephalography.

RESULTS

The laterality index for strengths of the auditory-cortex 100 ms responses (N100m) to vowels vs. tones suggested left-hemispheric dominance in 8 of the 10 strongly right-handed subjects, and right-hemispheric dominance in 7 of the 10 left-handed subjects.

CONCLUSIONS

Our results demonstrate difference in hemispheric dominance for processing of vowels between right-handed and left-handed subjects. This difference resembles language lateralization suggested by previous invasive studies as well as by anatomical and functional comparisons in left- and right-handed subjects.

SIGNIFICANCE

After comparison with the Wada test, this simple paradigm could prove useful as a noninvasive test for language lateralization in clinical settings.

On the human sensorimotor-cortex beta rhythm: sources and modeling

Cortical oscillations in the beta band (13-35 Hz) are known to be modulated by the GABAergic agonist benzodiazepine. To investigate the mechanisms generating the approximately 20-Hz oscillations in the human cortex, we administered benzodiazepines to healthy adults and monitored cortical oscillatory activity by means of magnetoencephalography. Benzodiazepine increased the power and decreased the frequency of beta oscillations over rolandic areas. Minimum current estimates indicated the effect to take place around the hand area of the primary sensorimotor cortex. Given that previous research has identified sources of the beta rhythm in the motor cortex, our results suggest that these same motor-cortex beta sources are modulated by benzodiazepine. To explore the mechanisms underlying the increase in beta power with GABAergic inhibition, we simulated a conductance-based neuronal network comprising excitatory and inhibitory neurons. The model accounts for the increase in the beta power, the widening of the spectral peak, and the slowing down of the rhythms with benzodiazepines, implemented as an increase in GABAergic conductance. We found that an increase in IPSCs onto inhibitory neurons was more important for generating neuronal synchronization in the beta band than an increase in IPSCs onto excitatory pyramidal cells.

Evaluation of immunogenicity and safety of Genevac B: a new recombinant hepatitis B vaccine in comparison with Engerix B and Shanvac B in healthy adults

PURPOSE

Genevac B, a new indigenous recombinant hepatitis B vaccine was evaluated for its immunogenicity and safety in comparison with Engerix B (Smithkline Beecham Biologicals, Belgium) and Shanvac B (Shantha Biotechnics, India) in healthy adult volunteers.

METHODS

While 240 study subjects were included in the Genevac B group, 80 each were the subjects for Engerix B and Shanvac B. A three dose regimen of 0,1,2 months was adopted with 20 gm dosage uniformly in all the three groups. Vaccinees were assessed during prevaccination, followup and post vaccination periods for clinical, haematological, biochemical and immunological parameters for safety and immunogenicity.

RESULTS

Successful follow-up in all parameters for four months could be achieved in 92.5% (222/240) for Genevac B study subjects and the same was 85% (68/80) and 80% (64/80) for Engerix B and Shanvac B respectively. While 100% seroconversion was observed in all the three groups, the rate of seroprotectivity was 99.5% by Genevac B, 98.5% by Engerix B and 98.4% for Shanvac B. However the difference was not statistically significant (p>0.05). The GMT values of anti HBs after one month of completion of the vaccination were 735.50, 718.23 and 662.20 mIU/mL respectively. No systemic reaction was either seen or reported by the volunteers during the vaccination process of Genevac B and other two vaccines. Clinical, haematological and biochemical safety parameters remained within normal limits throughout the study period.

CONCLUSION

The study confirms that Genevac B, the new recombinant Hepatitis B vaccine has the acceptable international standards of safety and immunogenicity.

Activation of the human posterior parietal and temporoparietal cortices during audiotactile interaction

We recorded cortical-evoked responses with a whole-scalp neuromagnetometer to study human brain dynamics associated with audiotactile interaction. The subjects received unilateral auditory (A) or tactile (T) stimuli, or both stimuli simultaneously (AT), alternating to the left and right side. Responses to AT stimuli differed significantly from the algebraic sum of responses to A and T stimuli (A + T) at 75-85 and 105-130 ms and indicated suppressive audiotactile interaction. Source modeling revealed that the earlier interaction occurred in the contralateral posterior parietal cortex and the later interaction in the contralateral parietal opercula between the SII cortex and the auditory cortex. The interaction was significantly stronger in the left than the right hemisphere. In most subjects, AT responses were far more similar to T than to A responses, suggesting suppression of auditory processing during the spatially and temporally concordant audiotactile stimuli in which the tactile component was subjectively more salient.

Serodiagnosis of syphilis in a community: an evaluatory study

PURPOSE

To analyse the prevalence of syphilis in the apparently healthy population and to provide data for implementation of the joint STD/HIV control programme, a population based study was undertaken by using 'probability proportional to size' cluster survey method in three randomly chosen districts of Tamil Nadu, India namely Dindigul, Ramnad and Tanjore.

METHODS

Blood samples were collected from adults (n=1873) aged 15-45 years, from the selected households enrolled in this study. The sera were tested parallelly by rapid plasma reagin (RPR) and Treponema pallidum haemagglutination (TPHA) tests. Reactive samples by RPR and/or TPHA were later analysed by fluorescent treponemal antibody absorption (FTA-ABS) test.

RESULTS

The prevalence of syphilis in the community of Tamil Nadu as per RPR positivity was 2.7% (50/1873) as against 0.7% by TPHA (13/1873). FTA-ABS positivity was observed in only 12 out of 48 (25%) RPR/TPHA reactive samples tested. By taking the positivity by two of the three tests, the community prevalence of acute ongoing syphilis in Tamil Nadu was determined as 1.1% (20/1873).

CONCLUSIONS

The results confirmed that no single serological test for syphilis can act as the marker of ongoing acute infection in an apparently healthy population. The study suggests that for specific diagnosis of ongoing syphilis, the FTA-ABS test may be performed along with RPR and TPHA.

Task-dependent modulations of cortical oscillatory activity in human subjects during a bimanual precision grip task

Oscillations are a widespread feature of normal brain activity and have been reported at a variety of different frequencies in different neuronal systems. The demonstration that oscillatory activity is present in motor command signals has prompted renewed interest in the possible functions of synchronous oscillatory activity within the primate sensorimotor system. In the current study, we investigated task-dependent modulations in coupling between sensorimotor cortical oscillators during a bimanual precision grip task. The task required a hold-ramp-hold pattern of grip force to be exerted on a compliant object with the dominant right hand, while maintaining a steady grip with the nondominant hand. We found significant task-related modulation of 15- to 30-Hz coherence between magnetoencephalographic (MEG) activity recorded from the left sensorimotor cortex and electromyographic (EMG) activity in hand muscles on the right side. This coherence was maximal during steady hold, but disappeared during the ramp movements. Interestingly coherence between the right sensorimotor MEG and left-hand EMG showed a similar, although less deeply modulated, task-related pattern, even though this hand was maintaining a simple steady grip. No significant ipsilateral MEG-EMG coherence was observed in the 15- to 30-Hz passband for either hand. These results suggest that the cortical oscillators in the two sensorimotor cortices are independent to some degree but that they may share a common mechanism that attenuates the cortical power in both hemispheres in the 15- to 30-Hz range during movements of one hand. The results are consistent with the hypothesis that oscillatory activity in the motor system is important in resetting the descending motor commands needed for changes in motor state, such as those that occur in the transition from movement to steady grip.

Dorsal penile nerve stimulation elicits left-hemisphere dominant activation in the second somatosensory cortex

Activation of peripheral mixed and cutaneous nerves activates a distributed cortical network including the second somatosensory cortex (SII) in the parietal operculum. SII activation has not been previously reported in the stimulation of the dorsal penile nerve (DPN). We recorded somatosensory evoked fields (SEFs) to DPN stimulation from 7 healthy adults with a 122-channel whole-scalp neuromagnetometer. Electrical pulses were applied once every 0.5 or 1.5 sec to the left and right DPN. For comparison, left and right median and tibial nerves were stimulated alternatingly at 1.5-sec intervals. DPN stimuli elicited weak, early responses in the vicinity of responses to tibial nerve stimulation in the primary somatosensory cortex. Strong later responses, peaking at 107-126 msec were evoked in the SII cortices of both hemispheres, with left-hemisphere dominance. In addition to tactile processing, SII could also contribute to mediating emotional effects of DPN stimuli.

Herbal medicines for liver diseases in India

The use of natural remedies for the treatment of liver diseases has a long history, starting with the Ayurvedhic treatment, and extending to the Chinese, European and other systems of traditional medicines. The 21st century has seen a paradigm shift towards therapeutic evaluation of herbal products in liver diseases by carefully synergizing the strengths of the traditional systems of medicine with that of the modern concept of evidence-based medicinal evaluation, standardization of herbal products and randomized placebo controlled clinical trials to support clinical efficacy. The present review provides the status report on the scientific approaches made to herbal preparations used in Indian systems of medicine for the treatment of liver diseases. In spite of the availability of more than 300 preparations for the treatment of jaundice and chronic liver diseases in Indian systems of medicine using more than 87 Indian medicinal plants, only four terrestrial plants have been scientifically elucidated while adhering to the internationally acceptable scientific protocols. In-depth studies have proved Sylibum marianum to be anti-oxidative, antilipidperoxidative, antifibrotic, anti-inflammatory, immunomodulating and liver regenerative. Glycyrrhiza glabra has been shown to be hepatoprotective and capable of inducing an indigenous interferon. Picrorhiza kurroa is proved to be anti-inflammatory, hepatoprotective and immunomodulatory. Extensive studies on Phyllanthus amarus have confirmed this plant preparation as being anti-viral against hepatitis B and C viruses, hepatoprotective and immunomodulating, as well as possessing anti-inflammatory properties. For the first time in the Indian systems of medicine, a chemo-biological fingerprinting methodology for standardization of P. amarus preparation has been patented.

Oscillatory cortical drive to isometrically contracting muscle in Unverricht-Lundborg type progressive myoclonus epilepsy (ULD)

OBJECTIVE

We investigated with whole-scalp magnetoencephalography (MEG) oscillatory cortical drive to isometrically contracting muscle in 8 genetically verified, and thus etiologically homogeneous, Unverricht-Lundborg type progressive myoclonus epilepsy (ULD) patients suffering from cortical myoclonus and generalized tonic-clonic seizures. The results were compared with those of 8 healthy control subjects.

METHODS

Cortical MEG signals were measured simultaneously with surface electromyography (EMG) during isometric contraction of the left and right first dorsal interosseus muscles. Cortex-muscle coherence and cross-correlograms between MEG and EMG signals were calculated as indicators of oscillatory cortical drive to muscle. The cortical areas involved in the maximum cortex-muscle coherence were also identified.

RESULTS

In patients, the strengths of the dominant coherent peaks were 2-4 fold compared with the healthy controls. Whereas the coherence was found strictly in the contralateral primary motor cortex in controls, additional coherent activity was observed ipsilaterally in 5 out of 8 patients.

CONCLUSIONS

The remarkably increased MEG-EMG coherence in ULD patients suggests altered oscillatory cortical drive to the muscle during isometric contraction. We suggest that the enhanced cortex-muscle coherence in ULD patients reflects reduced inhibition in the motor cortex, and may contribute to disturbed voluntary movements.

Whose arm is it anyway? An fMRI case study of supernumerary phantom limb

Under normal circumstances, information from a number of sources is combined to compute a unitary percept of the body. However, after pathology these influences may be perceived simultaneously, resulting in multiple dissociated conscious representations. In a recent paper, we described subject E.P., a right-handed female stroke patient with a right frontomesial lesion who sporadically experiences a supernumerary 'ghost' left arm that occupies the previous position of the real left arm after a delay of 60-90 s. We used a delayed response paradigm with functional MRI to examine the haemodynamic correlates of E.P.'s illusion. Comparison of periods of time during scanning when the ghost arm was present against when it was not revealed a single cluster (9 voxels, t = 5.11, P < 0.012 corrected for multiple comparisons) located on the right medial wall in the supplementary motor area ('SMA proper'). Our results suggest that areas traditionally classified as part of the motor system can influence the conscious perception of the body. We propose that, as a consequence of her injury, E.P. is aware of the position of the phantom limb in this 'action space' while also continuing to be aware of the true position of her real limb on the basis of afferent somatosensory information.

Facilitation of neonatal nasotracheal intubation with premedication: a randomized controlled trial

OBJECTIVES

To determine if premedication reduces the time and number of attempts by junior medical staff to achieve nasotracheal intubation in neonates. The experimental design was a non-blinded randomized controlled pilot trial. The setting was a perinatal centre in a university teaching hospital.

METHODS

Twenty infants (within the ranges of 25-40 weeks gestation, 650-3660 g and 1 h to 81 days of age) requiring semi-urgent intubation were randomized to either premedication with morphine, atropine and suxamethonium, or to awake intubation.

RESULTS

There were no significant differences between the two groups in regard to prior intubation experience of the staff or infant weight or gestation. The intubation procedure, including intervening events, to completion was significantly faster in premedicated infants (median 60 s vs 595 s; P = 0.002) who were intubated at a younger postnatal age. It took twice as many attempts to intubate a conscious infant (median 2 vs 1; P = 0.010). There was a greater decrease in heart rate from the baseline in the unpremedicated group (mean 68 b.p.m. vs 29 b.p.m.; P = 0.017), but decreases in oxygen saturation were not different. Blood was observed in the oral and nasal passages after intubation in five of the awake infants and in one of the premedicated infants.

CONCLUSIONS

The use of premedication reduces the total time and number of attempts taken to achieve successful nasotracheal intubation of neonates by junior medical staff under supervision.

Cortical activation associated with passive movements of the human index finger: an MEG study

We recorded somatosensory evoked fields to passive extensions of the left and right index fingers in eight healthy adults. A new nonmagnetic device was designed to produce calibrated extensions of 19 degrees, with a mean angular velocity of 630 degrees/s. The responses, recorded with a 306-channel neuromagnetometer, were modeled with current dipoles. The earliest activation was in the primary somatosensory cortex, with peaks at 36-58 and 30-82 ms for left and right index finger extensions, respectively. Later signals were observed in the left second somatosensory (SII) cortex in six of eight subjects at 75-175 and 75-155 ms for left- and right-sided extensions, respectively; three subjects showed bilateral SII activation in at least one condition. Our results suggest a predominant role for the human left SII cortex in proprioceptive processing.