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.     

On the problem of cooperation of the reactions of hands: III. Cooperation of hand reactions to auditory and visual stimuli in patients with focal lesions of the brainstem and diencephalon

The response time (simple mental reaction time) cooperation was estimated in 53 patients with focal lesions of the brainstem and diencephalon (thalamus). The cooperation between the left-and right-hand simple mental reactions to auditory and visual stimuli presented after a warning stimulus was analyzed to determine the morphological structures responsible for the cooperation of responses. The cooperation of the simple mental reaction remained normal in some of the subjects and was disturbed in others. In the latter case, the correlation coefficient between the left-and right-hand simple mental reactions to an auditory or visual stimulus or both stimuli simultaneously was changed. The disturbances were detected in patients with lesions of the tectum at the boundary between the medulla and the pons and in those with affected lateral regions of the thalamus.     

Eye Tracking and Interhemispheric Interaction in the Distribution of Spatial Attention

The patterns of visual attention allocation were investigated in healthy subjects (n = 43) and patients with focal brain lesions (n = 17) using the original method developed for eye tracking in patients while memorizing a series of stimulatory image triplets. Two processes were estimated: delayed reproduction and recognition of stimuli in a series of consecutive visually similar distractors. In healthy subjects both processes correlated to a great extent (r = 0.6; p = 0.00001). The most significant disorders of voluntary verbal reproduction were observed when the left hemisphere of the brain was affected. The overall effectiveness of recognition in the case of brain damage decreased without significant dependence on the lateralization of the focus. Some correlation was observed between realized and remembered information and the patterns of visual fixations (concentrated on the semantic parts of the image or chaotically distributed in the space of stimulus exposure). Ineffective patterns of visual fixation in patients were more often observed in the area contralateral to the lesion. These contralateral stimuli were reproduced and recognized less efficiently in comparison with the central and ipsilateral images. Complete ignoring of the contralateral image in the triplet was observed both in the absence of visual fixation and in combination with the diffuse pattern.     

Estimation by humans of signals simulating different sound movement directions and specificity of the perception of these signals by patients with temporal epilepsy

The perception of moving sound stimuli that imitate directional sound source movement was studied in healthy subjects and in patients with temporal lobe lesions, as well as in a group of patients with simultaneous lesions of the temporal cortex and hippocampus. Under the conditions of dichotic stimulation of patients with the rightor left-side foci of convulsive activity, the nature and length of the trajectories of the emerging subjective sound images (SSI) were estimated depending on the direction of movement and interaural time difference (700, 400, 200 μs). The audiograms of all patients did not differ from those of healthy subjects, suggesting that the auditory sensitivity of patients remained unimpaired. However, in the patients, the trajectories were shorter than the trajectories in healthy subjects at all the values of the initial time delay and at all the directions of SSI movements. In patients with the cortical temporal epilepsy, changes of the subjective sound field were the most significant in the case of the right-side localization of foci of the convulsive activity. In patients with simultaneous lesions of the temporal cortex and hippocampus, the averaged trajectories of SSI movement differed significantly from those in the group of healthy subjects (p < 0.01) and in patients with a relatively isolated lesion of the temporal cortex (p < 0.05); these trajectories were independent of the initial delay. The mediobasal structures of the temporal lobe that are involved in the epileptic process proved to play a significant role in the perception and estimation of the moving sound stimuli, although they do not belong to the auditory system proper. The possible mechanisms underlying disorders in patients with temporal epilepsy are discussed.     

Evoked potentials to joint presentation of photic and acoustic stimuli in the human EEG

The results are outlined of a comparative estimation of averaged EP recorded in response to simultaneous and separate presentation of photic and acoustic stimuli on EEG of fifteen healthy subjects and twelve patients with focal lesions of the diencephalic structures. Investigation of the EP components and integral-temporal parameters has revealed that in healthy subjects EP to a combined heteromodal stimulation considerably exceeded by amplitude the one recorded in response to a separate presentation of stimuli. In case of lesion of the diencephalic formations, the converging effect of polysensory stimulation for the main waves of the response was less pronounced than in healthy subjects. At the same time, in pathological cases the summation effect of the afteraction potential (recorded after the main EP components as a slow negative oscillation) was manifested most distinctly, especially in the central zone of the cortex.     

The effects of neck flexion on cerebral potentials evoked by visual,auditory and somatosensory stimuli and focal brain blood flow in related sensory cortices

Background

A flexed neck posture leads to non-specific activation of the brain. Sensory evoked cerebral potentials and focal brain blood flow have been used to evaluate the activation of the sensory cortex. We investigated the effects of a flexed neck posture on the cerebral potentials evoked by visual, auditory and somatosensory stimuli and focal brain blood flow in the related sensory cortices.

Methods

Twelve healthy young adults received right visual hemi-field, binaural auditory and left median nerve stimuli while sitting with the neck in a resting and flexed (20° flexion) position. Sensory evoked potentials were recorded from the right occipital region, Cz in accordance with the international 10–20 system, and 2 cm posterior from C4, during visual, auditory and somatosensory stimulations. The oxidative-hemoglobin concentration was measured in the respective sensory cortex using near-infrared spectroscopy.

Results

Latencies of the late component of all sensory evoked potentials significantly shortened, and the amplitude of auditory evoked potentials increased when the neck was in a flexed position. Oxidative-hemoglobin concentrations in the left and right visual cortices were higher during visual stimulation in the flexed neck position. The left visual cortex is responsible for receiving the visual information. In addition, oxidative-hemoglobin concentrations in the bilateral auditory cortex during auditory stimulation, and in the right somatosensory cortex during somatosensory stimulation, were higher in the flexed neck position.

Conclusions

Visual, auditory and somatosensory pathways were activated by neck flexion. The sensory cortices were selectively activated, reflecting the modalities in sensory projection to the cerebral cortex and inter-hemispheric connections.     

A New Auditory Multi-Class Brain-Computer Interface Paradigm: Spatial Hearing as an Informative Cue

Most P300-based brain-computer interface (BCI) approaches use the visual modality for stimulation. For use with patients suffering from amyotrophic lateral sclerosis (ALS) this might not be the preferable choice because of sight deterioration. Moreover, using a modality different from the visual one minimizes interference with possible visual feedback. Therefore, a multi-class BCI paradigm is proposed that uses spatially distributed, auditory cues. Ten healthy subjects participated in an offline oddball task with the spatial location of the stimuli being a discriminating cue. Experiments were done in free field, with an individual speaker for each location. Different inter-stimulus intervals of 1000 ms, 300 ms and 175 ms were tested. With averaging over multiple repetitions, selection scores went over 90% for most conditions, i.e., in over 90% of the trials the correct location was selected. One subject reached a 100% correct score. Corresponding information transfer rates were high, up to an average score of 17.39 bits/minute for the 175 ms condition (best subject 25.20 bits/minute). When presenting the stimuli through a single speaker, thus effectively canceling the spatial properties of the cue, selection scores went down below 70% for most subjects. We conclude that the proposed spatial auditory paradigm is successful for healthy subjects and shows promising results that may lead to a fast BCI that solely relies on the auditory sense.     

Enhanced tactile performance at the destination of an upcoming saccade

Previous work has demonstrated that upcoming saccades influence visual and auditory performance even for stimuli presented before the saccade is executed. These studies suggest a close relationship between saccade generation and visual/auditory attention. Furthermore, they provide support for Rizzolatti et al.'s premotor model of attention, which suggests that the same circuits involved in motor programming are also responsible for shifts in covert orienting (shifting attention without moving the eyes or changing posture). In a series of experiments, we demonstrate that saccade programming also affects tactile perception. Participants made speeded saccades to the left and right side as well as tactile discriminations of up versus down. The first experiment demonstrates that participants were reliably faster at responding to tactile stimuli near the location of upcoming saccades. In our second experiment, we had the subjects cross their hands and demonstrated that the effect occurs in visual space (rather than the early representations of touch). In our third experiment, the tactile events usually occurred on the opposite side of upcoming eye movement. We found that the benefit at the saccade target location vanished, suggesting that this shift is not obligatory but that it may be vetoed on the basis of expectation.     

Spatial compatibility and position of the effectors

Mean reaction times obtained with crossed hands (right had on the left and left hand on the right) are slower than reaction times obtained with uncrossed hands (right hand on the right and left hand on the left). These results have been explained as a compatibility effect between the responding hand and its spatial position. The goal of the present experiment was to establish whether the position of the hand is encoded by the subjects relative to their body (absolute position) or relative to the other hand (relative position). The subjects performed a discrimination task on two visual stimuli. Stimuli and hands were either on the same side of the body (both on the left or both on the right) or had different absolute position. In all conditions the subjects responded with crossed and uncrossed hands. The results support the hypothesis that relative position is encoded.     

Visual and auditory conditional position discrimination in chimpanzees (Pan troglodytes)

Chimpanzee cognition has been studied predominantly through the visual modality, and much less through the auditory modality. The aim of this study was to explore possible differences in chimpanzees’ processing of visual and auditory stimuli. We developed a new conditional position discrimination (CPD) task requiring the association between a stimulus (from either the auditory or the visual modality), and a spatial position (left or right). The stimuli consisted of the face and voice of two individuals well known to the subjects (one chimpanzee and one human). Six chimpanzees participated in both the visual and the auditory conditions. We found contrasting results between the two conditions: the subjects acquired the CPD more easily in the visual than in the auditory condition. This supports previous findings on the difficulties encountered by chimpanzees in learning tasks involving auditory stimuli. Our experiments also revealed individual differences: the chimpanzee with the most extensive experience in symbolic visual matching tasks showed good performance in both conditions. In contrast, the chimpanzee expert in an auditory-visual intermodal matching task showed no sign of learning in either condition. Future work should focus on finding the most appropriate procedure for exploring chimpanzees’ auditory-visual cognitive skills.     

Behavioral and neuronal investigations of hypervigilance in patients with fibromyalgia syndrome

Painful stimuli are of utmost behavioral relevance and thereby affect attentional resources. In health, variable effects of pain on attention have been observed, indicating alerting as well as distracting effects of pain. In the human brain, these effects are closely related to modulations of neuronal gamma oscillations. As hypervigilance as an abnormal increase of attention to external stimuli has been implicated in chronic pain states, we assumed both attentional performance and pain-induced gamma oscillations to be altered in patients with fibromyalgia syndrome (FMS). We recorded electroencephalography from healthy subjects (n = 22) and patients with FMS (n = 19) during an attention demanding visual reaction time task. In 50% of the trials we applied painful laser stimuli. The results of self-assessment questionnaires confirm that patients with FMS consider themselves hypervigilant towards pain as compared to healthy controls. However, the experimental findings indicate that the effects of painful stimuli on attentional performance and neuronal gamma oscillations do not differ between patients and healthy subjects. We further found a significant correlation between the pain-induced modulation of visual gamma oscillations and the pain-induced modulation of reaction times. This relationship did not differ between groups either. These findings confirm a close relationship between gamma oscillations and the variable attentional effects of pain, which appear to be comparable in health and disease. Thus, our results do not provide evidence for a behavioral or neuronal manifestation of hypervigilance in patients with FMS.     

Aberrant Interference of Auditory Negative Words on Attention in Patients with Schizophrenia

Previous research suggests that deficits in attention-emotion interaction are implicated in schizophrenia symptoms. Although disruption in auditory processing is crucial in the pathophysiology of schizophrenia, deficits in interaction between emotional processing of auditorily presented language stimuli and auditory attention have not yet been clarified. To address this issue, the current study used a dichotic listening task to examine 22 patients with schizophrenia and 24 age-, sex-, parental socioeconomic background-, handedness-, dexterous ear-, and intelligence quotient-matched healthy controls. The participants completed a word recognition task on the attended side in which a word with emotionally valenced content (negative/positive/neutral) was presented to one ear and a different neutral word was presented to the other ear. Participants selectively attended to either ear. In the control subjects, presentation of negative but not positive word stimuli provoked a significantly prolonged reaction time compared with presentation of neutral word stimuli. This interference effect for negative words existed whether or not subjects directed attention to the negative words. This interference effect was significantly smaller in the patients with schizophrenia than in the healthy controls. Furthermore, the smaller interference effect was significantly correlated with severe positive symptoms and delusional behavior in the patients with schizophrenia. The present findings suggest that aberrant interaction between semantic processing of negative emotional content and auditory attention plays a role in production of positive symptoms in schizophrenia. (224 words)     

Use of backward masking test for the study of visual information processing in healthy subjects and schizophrenic patients

The study of 14 healthy subjects and 15 schizophrenic patients was conducted under visual backward masking conditions. Sensory thresholds were identified using the method of constant stimuli. A special modification of the backward masking technique with lateralized presentation of test and masking stimuli was used to study the lateral characteristics of visual attention. It was found that the thresholds of letter stimulus identification were significantly higher in patients with schizophrenia than in healthy subjects. Only in patients the asymmetry of visual perception was revealed with the higher recognition thresholds in the left visual hemifield. The overall data analysis suggests an association between increased recognition thresholds in schizophrenic patients and changes in the interruption mechanism functioning at the neocortex level.     

Effects of Auditory Stimuli in the Horizontal Plane on Audiovisual Integration: An Event-Related Potential Study

This article aims to investigate whether auditory stimuli in the horizontal plane, particularly originating from behind the participant, affect audiovisual integration by using behavioral and event-related potential (ERP) measurements. In this study, visual stimuli were presented directly in front of the participants, auditory stimuli were presented at one location in an equidistant horizontal plane at the front (0°, the fixation point), right (90°), back (180°), or left (270°) of the participants, and audiovisual stimuli that include both visual stimuli and auditory stimuli originating from one of the four locations were simultaneously presented. These stimuli were presented randomly with equal probability; during this time, participants were asked to attend to the visual stimulus and respond promptly only to visual target stimuli (a unimodal visual target stimulus and the visual target of the audiovisual stimulus). A significant facilitation of reaction times and hit rates was obtained following audiovisual stimulation, irrespective of whether the auditory stimuli were presented in the front or back of the participant. However, no significant interactions were found between visual stimuli and auditory stimuli from the right or left. Two main ERP components related to audiovisual integration were found: first, auditory stimuli from the front location produced an ERP reaction over the right temporal area and right occipital area at approximately 160–200 milliseconds; second, auditory stimuli from the back produced a reaction over the parietal and occipital areas at approximately 360–400 milliseconds. Our results confirmed that audiovisual integration was also elicited, even though auditory stimuli were presented behind the participant, but no integration occurred when auditory stimuli were presented in the right or left spaces, suggesting that the human brain might be particularly sensitive to information received from behind than both sides.     

Mismatch negativity of ERP in cross-modal attention

Event-related potentials were measured in 12 healthy youth subjects aged 19-22 using the paradigm "cross-modal and delayed response" which is able to improve unattended purity and to avoid the effect of task target on the deviant components of ERP. The experiment included two conditions: (i) Attend visual modality, ignore auditory modality; (ii) attend auditory modality, ignore visual modality. The stimuli under the two conditions were the same. The difference wave was obtained by subtracting ERPs of the standard stimuli from that of the deviant stim-uli. The present results showed that mismatch negativity (MMN), N2b and P3 components can be produced in the auditory and visual modalities under attention condition. However, only MMN was observed in the two modalities un-der inattention condition. Auditory and visual MMN have some features in common: their largest MMN wave peaks were distributed respectively over their primary sensory projection areas of the scalp under attention condition, but over front     

Continuity of Visual and Auditory Rhythms Influences Sensorimotor Coordination

People often coordinate their movement with visual and auditory environmental rhythms. Previous research showed better performances when coordinating with auditory compared to visual stimuli, and with bimodal compared to unimodal stimuli. However, these results have been demonstrated with discrete rhythms and it is possible that such effects depend on the continuity of the stimulus rhythms (i.e., whether they are discrete or continuous). The aim of the current study was to investigate the influence of the continuity of visual and auditory rhythms on sensorimotor coordination. We examined the dynamics of synchronized oscillations of a wrist pendulum with auditory and visual rhythms at different frequencies, which were either unimodal or bimodal and discrete or continuous. Specifically, the stimuli used were a light flash, a fading light, a short tone and a frequency-modulated tone. The results demonstrate that the continuity of the stimulus rhythms strongly influences visual and auditory motor coordination. Participants'' movement led continuous stimuli and followed discrete stimuli. Asymmetries between the half-cycles of the movement in term of duration and nonlinearity of the trajectory occurred with slower discrete rhythms. Furthermore, the results show that the differences of performance between visual and auditory modalities depend on the continuity of the stimulus rhythms as indicated by movements closer to the instructed coordination for the auditory modality when coordinating with discrete stimuli. The results also indicate that visual and auditory rhythms are integrated together in order to better coordinate irrespective of their continuity, as indicated by less variable coordination closer to the instructed pattern. Generally, the findings have important implications for understanding how we coordinate our movements with visual and auditory environmental rhythms in everyday life.     

Alpha-rhythm of the EEG in directed attention

Degree of manifestation and synchronization of rhythmic alpha-range components in various cortical areas was studied in healthy adult subjects in conditions of controlled computer experiment by spectral-correlation method of EEG analysis during directed attention previous to discrimination of tactile, auditory and visual stimuli. The obtained results show that in preparation for discrimination of heteromodal stimuli, specific reconstructions take place of alpha-range electrical activity determined by signal modality. These changes are expressed in a local increase of the degree of synchronization of alpha oscillations in those projection and associative brain areas which are connected with the analysis of the given stimuli. Functional significance of these reconstructions is seen in the fact that they are significantly more expressed at correct recognition. A hypothesis is suggested about participation of the alpha-range in neurophysiological mechanisms of directed attention.     

Clinical application of the P3 component of event-related potentials. I. Normal aging

Normal adult volunteer subjects ranging in age from 18 to 90 years participated in a study in which analogous auditory and visual paradigms, with infrequently occurring target and non-target events, were used to elicit event-related potentials (ERPs) with a prominent P3 component. Of the 135 subjects participating, 66 completed both auditory and visual paradigms. The amplitude and latency of P3 were analyzed using average ERPs, single trials (adaptive filter) and principal components analysis (PCA). Age regressions were calculated using measures derived from average ERPs and single trials. Single trial measures were better than average ERP measures in demonstrating age-related changes in P3 latency. There was a significant increase in P3 latency with age of 1–1.5 msec/year. The range of normal P3 latency for a given age (1 S.E. of the regression = 40 msec for the visual target stimuli) was much larger than obtained by other investigators.The visual paradigm produced higher P3 latency/age correlations than the auditory paradigm (visual target r = 0.52, non-target r = 0.42; auditory target r = 0.32, non-target r = 0.33). Within individuals, the amplitude and latency of P3 generated by auditory and visual stimuli were highly correlated, though the visual paradigm produced larger and later P3s than the auditory paradigm.There is an apparent change in the scalp topography of P3 with age. In young adults, P3s to target stimuli have a markedly parietal distribution. The distribution of P3 becomes more uniformly distributed from Pz to Fz with age. This may be due to changes in overlapping components such as the slow wave (SW) rather than to changes in the amplitude of P3 per se.     

How Does the Extraction of Local and Global Auditory Regularities Vary with Context?

How does the human brain extract regularities from its environment? There is evidence that short range or ‘local’ regularities (within seconds) are automatically detected by the brain while long range or ‘global’ regularities (over tens of seconds or more) require conscious awareness. In the present experiment, we asked whether participants'' attention was needed to acquire such auditory regularities, to detect their violation or both. We designed a paradigm in which participants listened to predictable sounds. Subjects could be distracted by a visual task at two moments: when they were first exposed to a regularity or when they detected violations of this regularity. MEG recordings revealed that early brain responses (100–130 ms) to violations of short range regularities were unaffected by visual distraction and driven essentially by local transitional probabilities. Based on global workspace theory and prior results, we expected that visual distraction would eliminate the long range global effect, but unexpectedly, we found the contrary, i.e. late brain responses (300–600 ms) to violations of long range regularities on audio-visual trials but not on auditory only trials. Further analyses showed that, in fact, visual distraction was incomplete and that auditory and visual stimuli interfered in both directions. Our results show that conscious, attentive subjects can learn the long range dependencies present in auditory stimuli even while performing a visual task on synchronous visual stimuli. Furthermore, they acquire a complex regularity and end up making different predictions for the very same stimulus depending on the context (i.e. absence or presence of visual stimuli). These results suggest that while short-range regularity detection is driven by local transitional probabilities between stimuli, the human brain detects and stores long-range regularities in a highly flexible, context dependent manner.     

Specific changes in auditory cognitive evoked potentials in those who participated in the liquidation of the Chernobyl accident: II. Analysis of the late P300 component

An integrated neuropsychological study and recording of auditory cognitive evoked potentials (EPs) using the three-stimulus oddball paradigm was performed in groups of ten subjects who participated in the liquidation of the consequences of the Chernobyl accident aged 50.5 ± 4.0 years and ten healthy subjects aged 47.0 ± 6.0 years. The neuropsychological study showed impairment of higher mental functions, including aspontaneity, fatigability, a decrease in the auditory-verbal and visual memories, and higher motor function deficiency, in cleanup workers (usually referred to as liquidators). Analysis of the amplitude and time characteristics of the P300 component of the auditory cognitive EP showed a decrease in the amplitude of this component in all cortical areas of liquidators in both experimental situations and for all stimuli compared to healthy subjects of the same age. Analysis of the latent period (LP) of P300 in liquidators showed the most distinct increase in the situation of passive audition for all types of stimuli. Analysis of the patterns of reactive rearrangements in different experimental situations showed that the P300 LPs of healthy subjects were similar for all types of stimuli during passive audition and were higher for the significant stimulus in the situation of counting. Liquidators were characterized by an type of response, with the LPs of responses to most stimuli increased in both experimental situations. Analysis of regional changes in the P300 LP showed that the differences in the P300 LP between the groups were the largest in the frontal areas of the left hemisphere. In addition, liquidators exhibited “uneconomical, excessive” responses as compared to normal responses, which suggests a decrease in the attention and memory capacities and could contribute to the impairment of higher mental functions. The changes in the amplitude and time characteristics of the P300 component of auditory EPs suggest deceleration of perception, processing, and analysis of information combined with weakened inhibition. The changes found in liquidators are similar to those observed in elderly people, which supports the hypotheses on accelerated brain aging and on pathological aging caused by low-dose irradiation.