Extraversion,neuroticism and individual differences in event-related potentials

Event-related potentials (ERPs) in response to task-irrelevant tone pips were elicited during meaningful and meaningless speech passages for two groups of subjects selected on the basis of their scores on the extraversion-introversion scale of the Eysenck Personality Questionnaire, ERPs were recorded from two temporal (T3 and T4) and Wernicke (W1 and W2) scalp locations. Peak latencies and amplitudes of N1, P2 and N2 components were obtained for each subject during each meaningful and meaningless condition. The extraverts exhibited higher levels of subjective engagement in the meaningful-speech condition than in meaningless condition; the opposite trend was found for introverts. The extraverts showed greater N2 amplitude in the meaningful-speech condition than in the meaningless condition; the reverse trend across conditions was found for introverts.     

Biofeedback of slow brain potentials]

Slow cortical potentials constitute neurophysiological indicators of cortical excitability. Behaviorally they correlate with attention and motor preparation. A system for biofeedback and self-regulation of slow cortical potentials (SCP) has been developed. The portable system allows on-line visual feedback of filtered and corrected slow brain potentials in a predetermined sequence of trials. Three different algorithms for transforming the original SCP-signal into a feedback-signal have been developed and were compared in a controlled outcome study. With the optimal feedback method subjects were able to produce cortical positivity and negativity on command after three sessions. Increases and decreases of negativity of up to 20 microV were also achieved. Therefore a simple and portable PC-based device for the clinical application of SCP-biofeedback is now available.     

The prediction of group motor performance from individual member abilities

Two experiments were conducted to investigate the prediction of group performance on the motor-maze task from individual member abilities. In both experiments subjects performed 20 individual trials on the maze task in an initial session prior to the actual experiment. On the basis of these individual performance scores, two-person groups were formed so that the groups represented a range of average ability levels and a range of discrepancies in abilities between partners. In Experiment 1, all groups performed a cooperative and a noncooperative group task in separate sessions both involving competition with another group. Only the cooperative group task was used in Experiment 2, but all groups performed under both competitive and noncompetitive conditions. Multiple regression analyses yielded a moderate, positive relationship between member abilities and group performance in both experiments; group performance on the highly cooperative task was dominated by the lower-ability partner.     

Preparation and motor potentials in chronic tic and Tourette syndromes

Many studies have found that people with tic disorder show more difficulty when inhibiting an automated than a controlled response. Furthermore, although normal motor threshold and excitability are present, but reduced or impaired, motor inhibition seems manifest in patients with tic. In order to localize this inhibition impairment in tic disorder the present study examine two response-locked ERPs: the Bereitschaft (preparation BP) and the motor potentials (MP). The simple tic group showed faster BP latency and smaller amplitude than control and complex tic group and did not show a corresponding change in values with practice or with automated or controlled condition. The MP amplitudes revealed that whereas both controls and complex tic disorder showed a decrease in amplitude during control condition for both blocks, simple tic showed larger amplitude. Our ERP results are in agreement with RT results of a previous study. The explanation could lie with modulation in motor excitation inhibition circuits and seems worse in simple tics where the movements are more automatic and nonvoluntary.     

Method for studying spinal evoked potentials]

The authors describe a new method of examing evoked spinal potentials. Derivation is by means of unipolar needle electrodes which are ventrolaterally introduced into the cervical disk space as far as the posterior longitudinal ligament. Detection of a spinal potential following the stimulation of brachial and crural nerves allows to exclude the possibility of complete transverse lesion of the spinal cord or severing of the peripheral nerve or plexus.     

Word learning and individual differences in word learning reflected in event-related potentials

Adults learned the meanings of rare words (e.g., gloaming) and then made meaning judgments on pairs of words. The 1st word was a trained rare word, an untrained rare word, or an untrained familiar word. Event-related potentials distinguished trained rare words from both untrained rare and familiar words, first at 140 ms and again at 400-600 ms after onset of the 1st word. These results may point to an episodic memory effect. The 2nd word produced an N400 that distinguished trained and familiar word pairs that were related in meaning from unrelated word pairs. Skilled comprehenders learned more words than less skilled comprehenders and showed a stronger episodic memory effect at 400-600 ms on the 1st word and a stronger N400 effect on the 2nd word. These results suggest that superior word learning among skilled comprehenders may arise from a stronger episodic trace that includes orthographic and meaning information and illustrate, how an episodic theory of word identification can explain reading skill.     

Long-range correlation properties in motor timing are individual and task specific

1/f (β) noise represents a specific form of (long-range) correlations in a time series that is pervasive across many sensorimotor variables. Recent studies have shown that the precise properties of the correlations demonstrated by a group of test participants may vary as a function of experimental conditions or factors characterizing the group. Our purpose in the present study was to clarify whether long-range correlations affect sensorimotor performance generally or in a task-specific manner and whether each individual produces characteristic long-range correlations that are reliable across several runs of the same task. We analyzed the series of time intervals produced by 43 participants in two timing tasks: unimanual rhythmic tapping and circle drawing. We found that a participant's 1/f (β) properties in tapping were not related to the 1/f (β) properties in circle drawing. However, within each task, individual differences were reliable, and a Cronbach's alpha of .59 showed a high degree of within-subjects reproducibility of the long-range correlations. Thus, long-range correlations represent a consistent and distinctive characteristic of individuals performing a particular task, rather than a ubiquitous generic property of sensorimotor time series. The implications of these results are discussed from both a theoretical and a methodological perspective.     

Motor imagery combined with action observation training optimized for individual motor skills further improves motor skills close to a plateau

The acquisition of high-level motor skills beyond a “plateau” is important in sports training and rehabilitation. We aimed to investigate whether motor skills close to a plateau state can be improved further by performing motor imagery (MI) training while observing movements with difficulty levels optimized for individual motor skills. The subjects were divided randomly into four groups (n = 10 per group): the control group and three groups of MI combined with action observation (MI + AO) training with varying difficulty levels. The task was to rotate the two cork balls 20 times counterclockwise using the left hand. The subjects performed 30 and 10 successful trials of this task before and after MI + AO training, respectively. In the three training groups, MI training was performed while observing videos showing ball rotation movements adjusted to the same level, a moderately higher level, or a remarkably higher level of difficulty than that achieved by the individual subjects. The improvement rate of the ball rotation time after MI + AO training was significantly higher in the moderate-difficulty than in the control group and remarkably higher level of difficulty group. The other two MI + AO training groups did not differ significantly compared with the control group. The vividness of the MI during MI + AO training was significantly greater in the moderate-difficulty vs. the remarkably-high-difficulty group. These results suggest that performing MI training while observing movement at a level that is moderately higher than an individual's ability can promote improvements in motor skills (close to a plateau state) in rehabilitation and sports training. The vividness of MI may be an important index for determining the difficulty level of the movement to be observed during MI + AO training.     

Morphological units in the Arabic mental lexicon: evidence from an individual with deep dyslexia

An ongoing debate in Arabic morphology concerns the nature of the smallest unit governing lexical organization and representation in this language. A standard model maintains that Arabic words are typically analyzable into a three-consonantal root morpheme carrying the core meaning of words and a prosodic template responsible mostly for grammatical information. This view has been largely supported by research in both theoretical linguistics and psycholinguistics. An alternative theory holds that the meaning of words in Arabic is, rather, encoded in the 'etymon' comprising two unordered consonants of the root only. Results from a recent priming experiment have shown that the etymon induces strong morphological priming effects, supporting its morphological/lexical status. In this paper we present data from a patient with deep dyslexia questioning the role of the etymon as a psychologically real representational unit in Arabic and arguing, instead, for the central role of the root in both morphological and lexical representation in this language.     

Determinants of hand attractiveness--a study involving digitally manipulated stimuli

Although attractiveness of the human hand is of significance in the social and mating context, thus far it has attracted little scientific interest. In this study, young women and men were presented with pairs of digitally manipulated images of opposite-sex hands and asked to indicate the hand perceived to be the more attractive in each pair. The hands within a pair differed from one another by a single feature: shape averageness, femininity, finger length, second-to-fourth-digit ratio, or skin smoothness. All these features, with the exception of the digit ratio, were shown to increase hand attractiveness in each sex in both dorsal and ventral views. Skin smoothness was preferred more strongly in female than in male hands. Women also tended to prefer medium degrees of shape femininity and skin smoothness in male hands compared to both high and low levels. Adaptive and non-adaptive (related to perceptual bias) mechanisms underlying these preferences are discussed.     

Extroversion-related differences in speed of premotor and motor processing as revealed by lateralized readiness potentials

To further elucidate extroversion-related differences in speed of sensorimotor processing, the authors obtained behavioral and psychophysiological measures as participants (16 introverts and 16 extroverts) performed a visual go/no-go task. Although no extroversion-related differences in reaction time emerged, introverts showed faster premotor processing but slower central and peripheral motor processing--as indicated by latencies of the lateralized readiness potential (LRP) and electromyographic (EMG) data, respectively--than extroverts did. Additional regression analyses revealed that stimulus-locked LRP latency, response-locked LRP latency, and Nl EMG amplitude accounted for 40% of overall variability in individual extroversion scores. On the basis of the present results, the authors introduce a compensation hypothesis that accounts for the common failure of researchers to demonstrate extroversion-related differences in reaction time. The present results challenge J. Brebner and C. Cooper's (1985) model of extroversion in which stimulus analysis is not slower in introverts than in extroverts. However, the present findings support the assumption of faster motor processing in extroverts.     

Discrimination of differences in digitally manipulated phoneme length during speech

The present study investigated differences in the thresholds of phoneme duration in word and sentence contexts by participants' sex. In the word condition, 27 participants listened to two pairs of words in a dual pair discrimination task. One pair contained the same durations of /s/, and the other pair contained different durations of /s/. Participants were to select the pair which contained different durations of /s/ in the words. In the sentence condition, the other set of 27 participants listened to two pairs of sentences and selected the pair containing different durations of /s/ in the sentences. Throughout these tasks, the participants' just-noticeable-difference and trials-to-completion were analyzed. The results showed that the participants demonstrated better performance in detecting just-noticeable-difference in the sentence condition than in the word condition. In addition, a sex difference was found in just-noticeable-difference in both conditions with better performance in men than women. No significant differences in trials-to-completion were found in either condition.     

Same kinematics but different objects during action observation: Detection times and motor evoked potentials

Motor resonance refers to the fact that an observed action is online subliminally reenacted. The aim of the present paper was to verify if, on equal terms of kinematics, the to-be-grasped object's intrinsic properties are influencing the observers' motor behaviour. A detection time and a single pulse transcranial magnetic stimulation experiment were performed to verify the effects of a change of object's intrinsic properties artificially made on a video showing a grasping action. In particular, the object substituting the original one was not graspable by the showed movement. Results indicated an influence of object's intrinsic properties: Detection times were delayed and motor evoked potentials were reduced when the movement shown was not suitable to grasp the object. These results are interpreted as an evidence that during grasping action observation the motor system of the observer is influenced not only by the seen movements but also by the to-be-grasped object.     

Evaluative priming from subliminal emotional words: Insights from event-related potentials and individual differences related to anxiety

The present ERP study investigated effects of subliminal emotional words on preference judgments about subsequent visual target stimuli (paintings, portraits). Each target was preceded by a masked 17-ms emotional adjective. Four classes of prime words were distinguished according to the combinations of positive/negative valence and high/low arousal. Targets were liked significantly more after positive-arousing primes (e.g., happy), relative to negative-arousing (brutal), positive-nonarousing (mild), and negative-nonarousing primes (lazy). In the target ERP, amplitude of right-hemisphere positive slow wave was increased after positive-arousing compared to negative-arousing primes. Evaluative priming effects on judgments and ERPs were more pronounced in high state-anxious participants. The results suggest that (1) there is indeed affective/semantic processing of unconscious words, (2) evaluative priming operates relatively late during target processing, (3) to be effective, prime words need to score high on the arousal dimension, and (4) individual differences in state anxiety modulate the susceptibility to subliminal evaluative priming.     

Facilitation of motor evoked potentials and H-reflexes of flexor carpi radialis muscle induced by voluntary teeth clenching

In order to examine the effects of remote facilitation on cortical and spinal sites, we recorded motor evoked potentials (MEPs) and H-reflexes from the flexor carpi radialis muscle of 13 healthy subjects. The H-reflex was used to assess excitability changes at the spinal level, while the MEP following transcranial magnetic stimulation was used to study excitability changes at the cortical level. We induced remote facilitation by means of voluntary teeth clenching (VTC), the so-called Jendrassik maneuver, because this procedure is known to be effective and reliable. Although the facilitation induced by VTC was observed in both evoked potentials (i.e., H-reflex and MEP), which is consistent with previous reports, MEP onset latencies were shortened by VTC in proportion to an increased MEP amplitude, whereas the latencies of the H-reflex were not. Furthermore, statistically significant relationships between MEP latencies and amplitudes were observed in all subjects, whereas no such relationships were observed for the H-reflex. On the basis of these results, two neural pathways are presumed: one involving a release of pre-synaptic inhibition at the spinal level and the other involving an unmasking of lateral excitatory projections at the cortical level.     

Psychological variables and success of interpersonal coordination of motor performance tasks]

This paper examines which dispositional, cognitive and motivational variables will contribute to improved multi-person motor coordination. The study conceptually refers to a control-theoretical approach of continuous motor behavior. According to this approach interpersonal behavior should be determined by similar regulative processes as is individual behavior. Results of a laboratory study with 18 three-person groups support assumptions of this approach. Substantial effects on group performance are found for dispositional and motivational variables. Theoretical implications of the results obtained are discussed. Conclusions for applied issues are derived.     

Influence of temperature on the bioelectric conductivity of peripheral motor nerve]

14 persons were examined electro-neurographically before and after cooling with an ice bag. The following results were found. A slight decrease of the motor conductivity is verified. This decrease in function is shown most markedly in the slowly-conducting motor neurons. At the cooling borderlines reactions with increased function are discernible. For the clarification of the relevance of changes of the nerve conductivity, further investigations with methodic variants are necessary.     

Changes in spontaneous slow potentials and visually (flash) evoked potentials in response to stimuli with no performance implication]

The influence of spontaneous slow potential shifts (SPSs) on visual (flash-)evoked potentials (VEPs) was studied. Eighteen subjects received 100 flashes. The sequence of interstimulus-intervals (ISIs) was pseudo-randomized. ISI-durations were 3, 5, 7, 9 or 11 seconds. EEG was recorded from Fz, Cz, Pz and Oz with linked-mastoids as reference. EEG was EOG-corrected and VEPs were calculated for preceding positive SPSs. Averaging was done for local SPSs; VEP pairings as well as VEPs were calculated over occipital SPS-polarities. Results showed an influence of SPSs on VEP-amplitudes. Differences in amplitudes were interpreted with the 'activation-correction'-hypothesis and with the 'ceiling'-hypothesis. Negative SPSs were followed by smaller negative peaks, and positive SPSs were followed by smaller positive peak-amplitudes. Differences in latencies of N145-P300 peak-to-peak amplitudes after SPSs of different polarity were explained with the threshold-regulation hypothesis. Spectral-analysis were done for SPS-data. There were only poor effects, showing increased parietal alpha 2-power after negative SPSs.