How does the heel-off posture modify gait initiation parameter programming?

The authors studied the adjustment of the 2 distinct known expressions of gait velocity, the velocity of the center of gravity (CG) and the velocity of the center of foot pressure (CP) at the end of the 1st step in 2 experimental situations: natural gait initiation (the control situation, CS) and heel-off gait initiation (the test situation, TS). Gait was initiated by 7 healthy participants, from an erect spontaneous posture in the CS and from a posture with heels raised in the TS, on a force platform at 3 self-selected speed conditions. Biomechanical data from the force platform were collected in both experimental situations, and the authors used a particular gait analysis based on the differential method of Y. Brenière (2003) in order to approach velocity modulation by means of step length and frequency. Results showed that CG and CP velocities were adjusted differently during heel-off gait initiation than during natural gait initiation. CP velocity, as compared with CG velocity, was overestimated in TS. Results also established the relevance of the expression of step velocity by means of step length and frequency: The central nervous system, taking into account the specific postural constraints of each experimental situation, uses a reference value and a regulating parameter to modulate step velocity. Moreover, the contributions of 1st step length and frequency to the expression of step velocity in TS and CS were different. Thus, a specific locomotor behavior corresponds to a given experimental situation that is characterized by its own initial biomechanical constraints.     

Differential method of characterizing gait strategies from step lengths and frequencies: strategy of velocity modulation

The differential method consists of the analysis of the variation of gait parameters length, frequency, and velocity with respect to their mean values, respectively, Delta L = L - L(m), Delta f = f - f(m), and Delta v = v - vm, where L(m), f(m), and v(m) represent the mean values of those parameters. Assuming that the strategy of modulation of velocity implies that L and f are functions of v and that statistical analyses of ratios Delta L/Delta v and Delta f/Delta v have established that there is a very significant linear correlation, close to 1, between those ratios, the mathematical procedure allows one to determine the equation of step length, L = a x f + b x v + K, where a and b are the slope and the intercept of the linear regression and K is close to L(m). The equation was experimentally tested on 140 gait sequences performed by 6 participants and for gait velocities ranging from 0.6 to 2.2 m/s and was found to be very representative of all individual values. The differential method provides another way of using the derivative of velocity, v = L x f, to characterize the strategy of velocity modulation, which then permits one to determine the linear equation of velocity, v = f x L + L x f(m) - L(m) x f(m), and to show that the respective parts played by each parameter in the progression velocity are approximately equal. The author establishes the uniqueness of the different linear adjustments and discusses the differential method's own modes of use, that is, interindividually or globally.     

Effect of bilateral stimulation of the subthalamic nucleus on parkinsonian dysarthria

Never was the effect of bilateral stimulation of the subthalamic nucleus (STN) evaluated quantitatively on all the components of speech production, that is articulation, respiration and phonation, at the same time. It is the purpose of this study which uses force measurements of the articulatory organs and acoustic analysis in 16 parkinsonian patients. With STN stimulation, reaction and movement time of the articulatory organs decreased and their maximal strength, as well as their precision increased. We also noted a large beneficial effect on voice with a significant improvement in respiratory and phonatory functions.     

Correlation between evening and morning waking EEG and spatial orientation

The prefrontal, frontal, and parietal EEG of 16 healthy young adults (seven men, nine women; age=22.57+/-4.2) was recorded during the waking state (eyes closed) in the evening before and the morning following a second consecutive night spent in a sleep laboratory. Following the morning EEG recording session, participants were tested in a human-size maze upon five learning trials of a four-intersection route. Results on the fifth trial served as the learning index. We found a significant positive correlation between time taken to carry out the route and prefrontal, frontal EEG alpha-2 (10.0-12.75 Hz), and sigma (11.5-14.5 Hz) frequency bands. We also found that prefrontal and frontal theta activity correlated negatively with number of errors. No correlation was found between performance and neither alpha-1 (8.0-9.75 Hz) nor parietal EEG activity. These results confirm the involvement of the prefrontal and frontal cortices in the mechanisms responsible for modulating spatial orientation.     

Erotomanic stalking in evolutionary perspective

Erotomania, the delusion of being loved by another person, comprises marked sex differences concerning prevalence rates and behavior. Whereas traditional psychiatry has considered erotomania to be almost entirely restricted to women, recent studies have revealed that criminal offenses associated with the condition occur much more frequently in men. The main hypothesis of this article is that these findings may be explained in terms of evolutionary theory. Erotomania, accordingly, may be viewed as a pathological variant of a specific sexual strategy that evolved under selection pressures of the human environment of evolutionary adaptedness. The overt behavior is related to the pursuit of long-term mating, its potentially beneficial effect on inclusive fitness of the individual, and disparate strategies of the sexes to ensure sexual fidelity of the potential partner. Therefore, the evolutionary approach provides a plausible explanation as to why forensically relevant erotomania prevails in men. The pathological process of delusional misinterpretation of perceived signals from the social environment itself may result from poor reality testing due to a failure of social meta-cognition. The evolutionary perspective may provide additional insights into the nature of sex-specific behaviors and may improve our understanding of forensically relevant behaviors.     

Post-training intrahippocampal injection of synthetic poly-alpha-2,8-sialic acid-neural cell adhesion molecule mimetic peptide improves spatial long-term performance in mice

Several data have shown that the neural cell adhesion molecule (NCAM) is necessary for long-term memory formation and might play a role in the structural reorganization of synapses. The NCAM, encoded by a single gene, is represented by several isoforms that differ with regard to their content of alpha-2,8-linked sialic acid residues (PSA) on their extracellular domain. The carbohydrate PSA is known to promote plasticity, and PSA-NCAM isoforms remain expressed in the CA3 region of the adult hippocampus. In the present study, we investigated the effect on spatial memory consolidation of a PSA gain of function by injecting a PSA mimetic peptide (termed pr2) into the dorsal hippocampus. Mice were subjected to massed training in the spatial version of the water maze. Five hours after the last training session, experimental mice received an injection of pr2, whereas control mice received PBS or reverse peptide injections in the hippocampal CA3 region. Memory retention was tested at different time intervals: 24 h, 1 wk, and 4 wk. The results showed that the post-training infusion of pr2 peptide significantly increases spatial performance whenever it was assessed after the training phase. By contrast, administration of the control reverse peptide did not affect retention performance. These findings provide evidence that (1) PSA-NCAM is involved in memory consolidation processes in the CA3 hippocampal region, and (2) PSA mimetic peptides can facilitate the formation of long-term spatial memory when injected during the memory consolidation phase.     

Conditional visuo-motor learning and dimension reduction

Conditional visuo-motor learning consists in learning by trial and error to associate visual cues with correct motor responses, that have no direct link. Converging evidence supports the role of a large brain network in this type of learning, including the prefrontal and the premotor cortex, the basal ganglia (BG) and the hippocampus. In this paper we focus on the role of a major structure of the BG, the striatum. We first present behavioral results and electrophysiological data recorded from this structure in monkeys engaged in learning new visuo-motor associations. Visual stimuli were presented on a video screen and the animals had to learn, by trial and error, to select the correct movement of a joystick, in order to receive a liquid reward. Behavioral results revealed that the monkeys used a sequential strategy, whereby they learned the associations one by one although they were presented randomly. Human subjects, tested on the same task, also used a sequential strategy. Neuronal recordings in monkeys revealed learning-related modulations of neural activity in the striatum. We then present a mathematical model inspired by viability theory developed to implement the use of strategies during learning. This model complements existing models of the BG based on reinforcement learning (RL), which do not take into account the use of strategies to reduce the dimension of the learning space.     

A tale of two visions: can a new view of personality help integrate psychology?

Personality psychology studies how psychological systems work together. Consequently, the field can act as a unifying resource for the broader discipline of psychology. Yet personality's current fieldwide organization promotes a fragmented view of the person, seen through such competing theories as the psychodynamic, trait, and humanistic. There exists an alternative--a systems framework for personality--that focuses on 4 topics: identifying personality, personality's parts, its organization, and its development. This new framework and its view of personality are described. The framework is applied to such issues as personality measurement, psychotherapy outcome research, and education. The new framework may better organize the field of personality and help with its mission of addressing how major psychological systems interrelate.     

Sequential combinations of drug and cognitive behavioral therapy for chronic insomnia: an exploratory study

This study explores the efficacy of sequential treatments involving medication and cognitive behavioral treatment (CBT) for primary insomnia. Seventeen participants took part in a multiple baseline design and were assigned to: (a) medication for 5 weeks, followed by combined medication plus CBT for 5 weeks; (b) combined treatment for 5 weeks, followed by CBT alone; or (c) CBT alone. Each treatment sequence produced significant sleep improvements, but at different points in time. For the first sequence, most of the sleep improvement was obtained after the introduction of CBT, while for the other sequence and CBT alone, improvement appeared during the first weeks. These results suggest that sleep improvement seems affected by the way treatments are combined. Also, a sequence beginning with a combined treatment followed by CBT alone seems to produce the best outcome. Additional research should be conducted with larger samples to determine the most effective sequence.