On the Problem of Cooperation of the Reaction of Hands: I. Cooperation of Hand Reaction to Sound and Light Stimuli in Healthy Subjects

Coordinated reaction of hands was analyzed during examination of healthy subjects and patients with focal lesions of the central nervous system in order to find the morphological structures responsible for such cooperation. Results of investigation of coordinated hand reaction in healthy subjects to sound and light stimuli with a warning signal are presented. The degree of cooperation was estimated by the correlation coefficient between the values of the reaction time of the right and left hands under conditions of their simultaneous response. In healthy subjects, there exists a strong positive correlation, whose variability in repeated examinations is determined by constitutional features of the subject.     

Dynamics of temporal parameters of sensorimotor reactions in relation to the type of human movement

The study was conducted on nine right-handed male subjects 20-24 year old and consisted of two series. In the first series one warning signal in the form of one of the digits (from 1 to 8) was successively presented to the subjects on the display and then four trigger signals which required either simple pressing of the push button (an arrow with a dot) or its holding during 0.5 s (two arrows) by the right or left hand depending on the arrow direction. The digit corresponded to one variant of signals succession. Each variant was repeated randomly among other variants 15 times. In the second series instead of arrows asterisks were presented. Reaction time and duration of push button holding were recorded. Two regularities were observed: significant decrease of RT in the series of reacting by memory and successive decrease of RT in accordance with the decrease of the number of the remaining signals observed in both series. In the first series RT successively decreased by 35-40 ms, in the second one-by 16-20 ms. It is supposed that the difference in RTs between series characterizes the time of signal structure analysis, while the difference in RTs within one block of signals in the second series-the time of extraction of selected motor program from memory.     

Effect of music on motor reaction time and interhemispheric relations

Influence of music on motor reaction time (RT) was studied. Warning and triggering stimuli were presented either in the left or in the right visual fields. RT was recorded when playing classical or variety music; control sessions were not accompanied by music. Music shortened RT, and its stimulating effect was the stronger the longer were the initial RTs without music. The influence of variety music was more effective than of the classic one. RT was shortened more when the triggering stimulus was presented in the left visual field. This phenomenon is considered to be an evidence of predominant influence of music on the right cerebral hemisphere due to greater activation from emotional structures.     

Motivational Salience Signal in the Basal Forebrain Is Coupled with Faster and More Precise Decision Speed

The survival of animals depends critically on prioritizing responses to motivationally salient stimuli. While it is generally believed that motivational salience increases decision speed, the quantitative relationship between motivational salience and decision speed, measured by reaction time (RT), remains unclear. Here we show that the neural correlate of motivational salience in the basal forebrain (BF), defined independently of RT, is coupled with faster and also more precise decision speed. In rats performing a reward-biased simple RT task, motivational salience was encoded by BF bursting response that occurred before RT. We found that faster RTs were tightly coupled with stronger BF motivational salience signals. Furthermore, the fraction of RT variability reflecting the contribution of intrinsic noise in the decision-making process was actively suppressed in faster RT distributions with stronger BF motivational salience signals. Artificially augmenting the BF motivational salience signal via electrical stimulation led to faster and more precise RTs and supports a causal relationship. Together, these results not only describe for the first time, to our knowledge, the quantitative relationship between motivational salience and faster decision speed, they also reveal the quantitative coupling relationship between motivational salience and more precise RT. Our results further establish the existence of an early and previously unrecognized step in the decision-making process that determines both the RT speed and variability of the entire decision-making process and suggest that this novel decision step is dictated largely by the BF motivational salience signal. Finally, our study raises the hypothesis that the dysregulation of decision speed in conditions such as depression, schizophrenia, and cognitive aging may result from the functional impairment of the motivational salience signal encoded by the poorly understood noncholinergic BF neurons.     

Reaction time and interhemispheric interaction

The study was made on healthy adult subjects. The reaction time of the hand (RT) was measured under two conditions: 1) the choice of reaction (right or left hand) is determined by the nature of the warning stimulus; 2) decision on the choice is taken, depending on the second, trigger stimulus. Stimuli are presented at random sequences to different visual fields. The reaction time to the visual signal presented to the visual field ipsilateral to the hand is significantly shorter (by 15 to 26 msec) than to the stimulus in the contralateral visual field. In a simple motor reaction, when no discrimination of trigger stimulus and the decision on the choice of reaction is required, a hemispheric asymmetry of reaction time is manifested: the left hemisphere only responds differently to direct visual stimulation and to that mediated through the contralateral hemisphere.     

Cognitive effects of radiation emitted by cellular phones: The influence of exposure side and time

This study examined the time dependence effects of exposure to radiofrequency radiation (RFR) emitted by standard GSM cellular phones on the cognitive functions of humans. A total of 48 healthy right‐handed male subjects performed a spatial working memory task (that required either a left‐hand or a right‐hand response) while being exposed to one of two GSM phones placed at both sides of the head. The subjects were randomly divided into three groups. Each group was exposed to one of three exposure conditions: left‐side of the head, right‐side, or sham‐exposure. The experiment consisted of 12 blocks of trials. Response times (RTs) and accuracy of the responses were recorded. It was found that the average RT of the right‐hand responses under left‐side exposure condition was significantly longer than those of the right‐side and sham‐exposure groups averaged together during the first two time blocks. These results confirmed the existence of an effect of exposure on RT, as well as the fact that exposure duration (together with the responding hand and the side of exposure) may play an important role in producing detectable RFR effects on performance. Differences in these parameters might be the reason for the failure of certain studies to detect or replicate RFR effects. Bioelectromagnetics 30:198–204, 2009. © 2008 Wiley‐Liss, Inc.     

Lateral facilitation of Hoffmann-reflexes prior to voluntary movement in a choice reaction time task.

Hoffmann reflexes (H reflexes) were elicited from both legs simultaneously in human subjects at varying intervals after a reaction signal (RS) in a binary choice reaction time task. A left light RS required a rapid plantar flexion of the left foot and a right light RS required a similar rapid response of the right foot. A large faciliataion of reflex amplitude occurred only in the muscle involved in the movement (right of left soleus). The timing of the facilitation indicated that a decision about the status of the RS occurred within 200 msec and probably was completed somewhat earlier. Furthermore, the facilitation of the H reflexes was shown to be closely linked with the organization required for the contractions of the responding muscle. The results are considered in the light of hypothesized mechanisms regulating voluntary movement.     

Bilateral asymmetry in bone measurements of the hand and lateral hand dominance

Two hundred thirty–five (235) normal male participants of the Baltimore Longitudinal Study were classified as right handed, left handed, and ambidextrous on the basis of their grip–strength performance. Their left and right hands were also radiographed and the measurements of the second metacarpal bones were evaluated on the basis of hand dominance. The results indicated that, as a rule, the right hand measurements are higher than those of the left hand, regardless of hand dominance. The bilateral differences in total width, length, total area and cortical area are significant among the right hand dominant and nonsignificant among the left hand dominant. Regardless off hand dominance the bilateral differences in medullary width are nonsignificant. These results suggest an inherent tendency of the right second metacarpal to have more bone than the left regardless of hand dominance. Differential stress due to hand dominance will increase the bilateral difference in the right handed and reduce it in the left handed.     

Analysis of monoPEGylated human galectin-2 by small-angle X-ray and neutron scattering: concentration dependence of PEG conformation in the conjugate

Protein conjugation with polyethylene glycol (PEG) is a valuable means for improving stability, solubility, and bioavailability of pharmaceutical proteins. Using human galectin-2 (hGal-2) and 5 kDa PEG as a model system we first produced a PEG-hGal-2 conjugate exclusively at the Cys75 residue, resulting in two monosubstituted subunits per hGal-2 homodimer. Small angle X-ray and neutron scattering (SAXS and SANS) were combined to provide complementary structural information about the PEG-hGal-2 conjugate, wherein signal generation in SAXS depends mainly on the protein while SANS data presents signals from both the protein and PEG moieties. SAXS data gave a constant radius of gyration (R(g) = 21.5 ?) for the conjugate at different concentrations and provided no evidence for an alteration of homodimeric structure or hGal-2 ellipsoidal shape upon PEGylation. In contrast, SANS data revealed a concentration dependence of R(g) for the conjugate, with the value decreasing from 31.5 ? at 2 mg/mL to 26 ? at 14 mg/mL (based on hGal-2 concentration). Scattering data have been successfully described by the model of the ellipsoidal homogeneous core (hGal-2) attached with polymer chains (PEG) at the surface. Evidently, the PEG conformation of the conjugate strongly depends on conjugate concentration and PEG's radius of gyration decreases from 24.5 to 15 ?. An excluded volume effect, arising from steric clashes between PEG molecules at high concentration, was quantified by estimating the second virial coefficient, A(2), of PEGylated hGal-2 from the SANS data. A positive value of A(2) (6.0 ± 0.4 × 10(-4) cm(3) mol g(-2)) indicates repulsive interactions between molecules, which are expected to protect the PEGylated protein against aggregation.     

Age-related changes in hand grip strength among rural and urban Haryanvi Jat females

The aim of this study was to investigate the age-related changes in hand grip strength (both right and left hand) among rural and urban Jat females and its correlation with various anthropometric variables. The present cross-sectional study was based on a sample of 600 Jat females (rural=300, urban=300), ranging in age from 40 to 70 years. Findings indicated that rural and urban Jat females exhibit an age-related decline in the mean values of hand grip strength (both right and left hand). The comparison suggested that rural Jat females had significantly higher overall mean value of hand grip strength (kg) (right hand=20.35 vs 18.87, p<0.001 and left hand=17.05 vs 15.68, p<0.001) than their urban counterparts. Mean values for right hand grip strength were found to be higher than left hand grip strength in rural as well as urban Jat females. Significant and positive correlation coefficients exist between hand grip strength (both right and left hand) and various anthropometric variables (height, weight, body mass index, biceps and triceps skinfold thickness) in both rural and urban Jat females. An age-related decline in manual functioning of rural and urban Jat females may be attributed to behavioral factors (reduced physical activity, sedentary lifestyle) and poor nutrition (deteriorating quality and quantity of food intake with increasing age) associated with the normal aging process.     

Unimanual Reaction Time during Comparison of Lateralized Verbal Stimuli: the Features of Interhemispheric Interactions Related to Subjects' Gender

Reaction time (RT) and number of correct responses to letter stimuli were measured in 49 male and 47 female subjects under conditions of crossed and uncrossed lateralization of a pair of stimuli and the hand that performed motor reaction. Gender differences were detected on the basis of RT in the hemispheric organization when a task was performed. Males reacted more rapidly to the stimuli presented in the right visual field, while females demonstrated no lateral effects. There was a significant difference in the case of the males' right hand between crossed and uncrossed lateralization of visual stimuli, which exceeded that in the females and in the case of the males' left hand. There were no gender differences in the number of correct responses. When motor response was performed by either hand, the number of correct responses was significantly higher when the stimuli were presented in the right visual field.     

Microplate assay for aptamer-based thrombin detection using a DNA-enzyme conjugate based on histidine-tag chemistry

We report a method to prepare a DNA–enzyme conjugate using histidine-tag (His-tag) chemistry. A DNA oligonucleotide was modified with nitrilotriacetate (NTA), whose K_d was approximately 10^?6 (M^?1) toward a His-tag present on a recombinant protein via the complexation of Ni²⁺. His-tagged alkaline phosphatase (His-AP) was used as the model enzyme. Enzyme immobilization on the microplate revealed the conjugation of His-AP and the NTA-modified DNA via an Ni²⁺ complex. SPR measurements also proved the conjugation of His-AP with the NTA-modified DNA via an Ni²⁺ complex. The DNA–enzyme conjugate was then used for the detection of thrombin using a DNA aptamer. The DNA-AP conjugate successfully amplified the binding signal between the DNA aptamer and the thrombin, and the signal was measured as the fluorescent intensity derived from the AP-catalyzed reaction. The detection limit was 11 nM. Finally, we studied the effect of the release of the immobilized His-AP from the microplate on the AP activity, because the present strategy used a cleavable linker for the conjugation and the enzyme immobilization. The DNase-catalyzed release of the immobilized His-AP resulted in a 1.7-fold higher AP activity than observed when the His-AP was surface-immobilized.     

The Atg12-Atg5 conjugate has a novel E3-like activity for protein lipidation in autophagy

Autophagy is a bulk degradation process in eukaryotic cells; autophagosomes enclose cytoplasmic components for degradation in the lysosome/vacuole. Autophagosome formation requires two ubiquitin-like conjugation systems, the Atg12 and Atg8 systems, which are tightly associated with expansion of autophagosomal membrane. Previous studies have suggested that there is a hierarchy between these systems; the Atg12 system is located upstream of the Atg8 system in the context of Atg protein organization. However, the concrete molecular relationship is unclear. Here, we show using an in vitro Atg8 conjugation system that the Atg12-Atg5 conjugate, but not unconjugated Atg12 or Atg5, strongly enhances the formation of the other conjugate, Atg8-PE. The Atg12-Atg5 conjugate promotes the transfer of Atg8 from Atg3 to the substrate, phosphatidylethanolamine (PE), by stimulating the activity of Atg3. We also show that the Atg12-Atg5 conjugate interacts with both Atg3 and PE-containing liposomes. These results indicate that the Atg12-Atg5 conjugate is a ubiquitin-protein ligase (E3)-like enzyme for Atg8-PE conjugation reaction, distinctively promoting protein-lipid conjugation.     

Effect of the duration of a reproducible interval on reaction time in man

The dependence of reaction time (RT) of reproduction of presented standard intervals on their duration (100-5000 ms) was studied on 30 subjects. The intervals were limited by two electrocutaneous stimuli or two clicks and were presented both at random and at a gradual increase or decrease, with a step of 100 ms. They were reproduced by pressing a button. The RTs duration depended on the presented interval within the range from 100 to 2000 ms. Such scatter of the upper limit is due to differences in the methods of presentation of the material and to individual features of the subjects. A presence of two mechanisms of time intervals reproduction is suggested for such experimental conditions: the image of the standard interval might be created either after its presentation or in the process of its presentation. Correspondingly, the RT dependence on the interval duration is manifest in the first case and is absent in the second.     

Low-frequency component of photoplethysmogram reflects the autonomic control of blood pressure

The question of how much information the photoplethysmogram (PPG) signal contains on the autonomic regulation of blood pressure (BP) remains unsolved. This study aims to compare the low-frequency (LF) and high-frequency components of PPG and BP and assess their correlation with oscillations in interbeat (RR) intervals at similar frequencies. The PPG signal from the distal phalanx of the right index finger recorded using a reflective PPG sensor at green light, the BP signal from the left hand recorded using a Finometer, and RR intervals were analyzed. These signals were simultaneously recorded within 15 min in a supine resting condition in 17 healthy subjects (12 males and 5 females) aged 33 ± 9 years (mean ± SD). The study revealed the high coherence of LF components of PPG and BP with the LF component of RR intervals. The high-frequency components of these signals had low coherence. The analysis of the signal instantaneous phases revealed the presence of high-phase coherence between the LF components of PPG and BP. It is shown that the LF component of PPG is determined not only by local myogenic activity but also reflects the processes of autonomic control of BP.     

Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex Modulates Repetition Suppression to Unfamiliar Faces: An ERP Study

Repeated visual processing of an unfamiliar face suppresses neural activity in face-specific areas of the occipito-temporal cortex. This "repetition suppression" (RS) is a primitive mechanism involved in learning of unfamiliar faces, which can be detected through amplitude reduction of the N170 event-related potential (ERP). The dorsolateral prefrontal cortex (DLPFC) exerts top-down influence on early visual processing. However, its contribution to N170 RS and learning of unfamiliar faces remains unclear. Transcranial direct current stimulation (tDCS) transiently increases or decreases cortical excitability, as a function of polarity. We hypothesized that DLPFC excitability modulation by tDCS would cause polarity-dependent modulations of N170 RS during encoding of unfamiliar faces. tDCS-induced N170 RS enhancement would improve long-term recognition reaction time (RT) and/or accuracy rates, whereas N170 RS impairment would compromise recognition ability. Participants underwent three tDCS conditions in random order at ∼72 hour intervals: right anodal/left cathodal, right cathodal/left anodal and sham. Immediately following tDCS conditions, an EEG was recorded during encoding of unfamiliar faces for assessment of P100 and N170 visual ERPs. The P3a component was analyzed to detect prefrontal function modulation. Recognition tasks were administered ∼72 hours following encoding. Results indicate the right anodal/left cathodal condition facilitated N170 RS and induced larger P3a amplitudes, leading to faster recognition RT. Conversely, the right cathodal/left anodal condition caused N170 amplitude and RTs to increase, and a delay in P3a latency. These data demonstrate that DLPFC excitability modulation can influence early visual encoding of unfamiliar faces, highlighting the importance of DLPFC in basic learning mechanisms.