Pairs Of Stimuli Research Articles

How Fast Is Too Fast? Boundaries to the Perception of Electrical Stimulation of Peripheral Nerves.

Transcutaneous electrical stimulation is a promising technique for providing prosthetic hand users with information about sensory events. However, questions remain over how to design the stimulation paradigms to provide users the best opportunity to discriminate these events. Here, we investigate if the refractory period influences how the amplitude of the applied stimulus is perceived. Twenty participants completed a two-alternative forced choice experiment. We delivered two stimuli spaced between 250 ms to 450 ms apart (inter-stimulus-interval, isi). The participants reported which stimulus they perceived as strongest. Each stimulus consisted of either a single or paired pulse delivered transcutaneously. The inter-pulse interval (ipi) for the paired pulse stimuli varied between 6 and 10 ms. We found paired pulses with an ipi of 6 ms were perceived stronger than a single pulse less often than paired pulses with an ipi of 8 ms (p = 0.001) or 10 ms (p < 0.0001). Additionally, we found when the isi was 250 ms, participants were less likely to identify the paired pulse as strongest, than when the isi was 350 or 450 ms. This study emphasizes the importance of basing stimulation paradigms on the underlying neural physiology. The results indicate there is an upper limit to the commonly accepted notion that higher stimulation frequencies lead to stronger perception. If frequency is to be used to encode sensory events, then the results suggest stimulus paradigms should be designed using frequencies below 125 Hz.

History-dependent dopamine release increases cAMP levels in most basal amygdala glutamatergic neurons to control learning.

Dopaminergic inputs to basal amygdala (BA) instruct learning of motivational salience. This learning depends on intracellular plasticity signals such as cyclic adenosine monophosphate (cAMP), which is regulated by activation of dopamine receptors. We examine the dynamics of dopamine release and downstream signaling during multiple salient events occurring within tens of seconds. We perform real-time tracking and manipulation of cAMP in BA neurons invitro and invivo. Optogenetically evoked release of dopamine drives proportional increases in cAMP in almost all BA glutamatergic neurons, suggesting widespread actions of dopamine across neurons preferring positive or negative valence. This cAMP response decreases across trials with short intertrial intervals owing to depression of dopamine release. No such depression is evident when photostimulating cAMP production directly. cAMP and protein kinase A responses to repeated appetitive or aversive stimuli also exhibit pronounced depression. Thus, history-dependent dynamics of dopamine and cAMP may regulate learning of temporally clustered, salient stimuli.

The phonetic realization of Russian pitch accents in contrastive questions and enumeration contexts

This paper presents the results of a phonetic experiment that compares the acoustic features of rising pitch configurations used in contrastive questions and on non-last elements of a list in enumeration contexts in Russian. 23 native Russian speakers were instructed to read aloud pairs of stimuli with similar segmental structure embedded in larger texts. Significant differences were found between the two syntactic context conditions. In enumeration contexts, both local minima and maxima associated with the prominent syllable had a significantly earlier and more stable alignment, and the slope of the rise between the tonal targets was steeper. In addition, the effect of the speech rate on these acoustic features was tested. The effects of fast and slow reading turned out to be asymmetric. In line with the segmental anchoring hypothesis, no significant effect of fast speech rate on alignment and pitch range was found; only the effect on slope was significant. Conversely, while reading the texts intentionally slowly the participants consistently used melodies with later alignment of local minima and maxima and larger pitch range. On the one hand, these data can be indicative of the interchangeability of stylistically marked pitch accent postulated for the incompleteness contexts in traditional descriptions of Russian intonation. On the other hand, this interpretation cannot account for the fact that the rightward shift in alignment in slow tempo was also found in the contrastive question condition.

Emotional and behavioral dysregulation in children with attention deficit hyperactivity disorder

To study disorders of emotional regulation in different types of attention deficit hyperactivity disorder (ADHD) in children. 58 children suffering from ADHD, aged 12 to 15 years were divided into 2 subgroups (38 children with a combined form of ADHD and 20 children with ADHD with a predominance of inattention). The control group consisted of 30 children without manifestations of neuropsychiatric disorders. The following research methods were used in the work: the SNAP-IY scale to assess the severity of the disease; the Strengths and Difficulties Questionnaire (SCT), a form for parents to assess emotional and behavioral impairments; Spielberger's self-assessment test in the processing of Khanin to assess the level of anxiety; spectral analysis of the EEG with the construction of graphical power spectra and registration of evoked potentials (EP) with the performance of an attention test in the Go/No-Go paradigm. The results of the study showed the presence of emotional and behavioral disorders in children with ADHD, more pronounced in the combined form of the disease. Complaints of emotional lability, tearfulness, irritability were noted in 53 children with ADHD in the study group (61.6%). At the same time, these complaints were registered in 39 children from the first group (72.2%) and 14 children from the second group (43.8%). The level of inattention was approximately the same (3.21±0.64 and 3.43±0.56, respectively), while the level of hyperactivity and impulsivity in adolescents from the first group was significantly higher (3.18±0.54, p<0.01). Indicators of the SCT scale, as a total indicator (3.4±1.6, p<0.01), and on the scales of «behavior problems» (7.4±1.6, p<0.01), «emotional problems» (8.0±1.6, p<0.01), «problems with peers» (7.6±1.3, p<0.01), «prosocial behavior» (3.4±1.6, p<0.01) were significantly higher in the subgroup of children from the first group. The performed statistical analysis of the test data for attention in the Go/No-Go paradigm revealed significant differences (p<0.01) in the number of omissions of significant pairs of stimuli between healthy children and a subgroup with ADHD with a predominance of inattention, between healthy children and a subgroup with combined form ADHD. When comparing evoked EEG synchronization in the theta range under Go conditions, we found a significant decrease in this parameter in the range of 200-400 ms in the subgroup of children with ADHD with a predominance of inattention and in the subgroup of ADHD with a combined form; under No-Go conditions, a significant decrease in the magnitude of evoked EEG synchronization was revealed in a subgroup of children with combined form ADHD. In general, the results of this study allow us to conclude that impaired cognitive control has a large impact on the development of emotional disorders in children with ADHD.

Crossmodal Correspondence Between Auditory Timbre and Visual Shape.

Crossmodal correspondences are defined as associations between crossmodal stimuli based on seemingly irrelevant stimulus features (i.e., bright shapes being associated with high-pitched sounds). There is a large body of research describing auditory crossmodal correspondences involving pitch and volume, but not so much involving auditory timbre, the character or quality of a sound. Adeli and colleagues (2014, Front. Hum. Neurosci. 8, 352) found evidence of correspondences between timbre and visual shape. The present study aimed to replicate Adeli et al.'s findings, as well as identify novel timbre-shape correspondences. Participants were tested using two computerized tasks: an association task, which involved matching shapes to presented sounds based on best perceived fit, and a semantic task, which involved rating shapes and sounds on a number of scales. The analysis of association matches reveals nonrandom selection, with certain stimulus pairs being selected at a much higher frequency. The harsh/jagged and smooth/soft correspondences observed by Adeli et al. were found to be associated with a high level of consistency. Additionally, high matching frequency of sounds with unstudied timbre characteristics suggests the existence of novel correspondences. Finally, the ability of the semantic task to supplement existing crossmodal correspondence assessments was demonstrated. Convergent analysis of the semantic and association data demonstrates that the two datasets are significantly correlated (-0.36) meaning stimulus pairs associated with a high level of consensus were more likely to hold similar perceived meaning. The results of this study are discussed in both theoretical and applied contexts.

Evaluating the effects of social interaction on the results of preference assessments for leisure items.

A variable that may influence the outcomes of stimulus preference assessments (SPAs) is whether social interaction is provided during the stimulus access period. In Experiment 1, we compared the outcomes of a Solitary paired stimulus preference assessment (PSPA) (toys only), Social PSPA (toys plus social interaction), and Combined PSPA (toys alone and toys plus social interaction) to determine whether the addition of social interaction influenced preference for toys in preschool children. In Experiment 2, we conducted a concurrent-operant reinforcer assessment to compare the reinforcing efficacy of stimuli with and without social interaction. Experiment 1 showed preference for toys was stable across assessments (Solitary and Social PSPAs) and most participants preferred toys plus social interaction when compared in a single assessment (Combined PSPA). Experiment 2 showed that results of the Combined PSPA in Experiment 1 predicted the outcome of most participants' reinforcer assessments.

Pattern-Induced Visual Discomfort and Anxiety in Migraineurs: Their Relationship and the Effect of Colour.

In migraineurs, coloured lenses were found to reduce the visual stress caused by an aversive pattern known to trigger migraines by 70%, but do such patterns also produce a low-level anxiety/fear response? Is this response lessened by colour? We sought to investigate this in a study comprising a broad screening component followed by a dot-probe experiment to elicit attentional biases (AB) to aversive patterns. Undergraduate psychology students completed headache and visual discomfort (VD) questionnaires (N = 358), thereby forming a subject pool from which 13 migraineurs with high visual discomfort and 13 no-headache controls with low visual discomfort, matched on age and sex, completed a dot-probe experiment. Paired stimuli were presented for 500 ms: aversive achromatic 3 cpd square wave gratings vs control, scrambled patterns. These conditions were repeated using the colour that was most comfortable for each participant. VD was greater in the more severe headache groups. On all measures, the migraineurs were more anxious than the controls, and a positive relationship was found between VD and trait anxiety. The 3 cpd gratings elicited an aversive AB in the migraine group which was somewhat reduced by the use of colour, and this was not seen in the controls. The results suggest a new role for colour in reducing visual stress via anxiety/fear reduction.

Speech-related auditory salience detection in the posterior superior temporal region

Processing auditory human speech requires both detection (early and transient) and analysis (sustained). We analyzed high gamma (70–110 Hz) activity of intracranial electroencephalography waveforms acquired during an auditory task that paired forward speech, reverse speech, and signal correlated noise. We identified widespread superior temporal sites with sustained activity responding only to forward and reverse speech regardless of paired order. More localized superior temporal auditory onset sites responded to all stimulus types when presented first in a pair and responded in recurrent fashion to the second paired stimulus in select conditions even in the absence of interstimulus silence; a novel finding. Auditory onset activity to a second paired sound recurred according to relative salience, with evidence of partial suppression during linguistic processing. We propose that temporal lobe auditory onset sites facilitate a salience detector function with hysteresis of 200 ms and are influenced by cortico-cortical feedback loops involving linguistic processing and articulation.

Electrophysiological assessment of the cranial reflexes

Electrophysiological assessment methods play a key role in the diagnosis of various neurological disorders. Electrophysiological evaluation of cranial reflexes is particularly valuable for neurologists. This article provides an overview of electrophysiological evaluation methods for cranial reflexes, which are most commonly used in clinical practice. They provide objective assessment of the functional integrity of nervous system structures that make up the cranial reflex arc, identify the level and, in some cases, the nature of disease, as well as pathophysiological mechanisms of central and peripheral nervous system disorders. We describe the instruments and main approaches to analysing the results for the standard blink reflex, blink reflex with prepulse inhibition, blink reflex with paired stimuli and recovery curve evaluation, reflex inhibition of the levator palpebrae superioris, jaw jerk reflex, and reflex inhibition (cutaneous silent period) of the masseter muscle.

A preliminary examination of social preference across assessors

AbstractThree assessors conducted paired stimulus preference assessments with an adult with autism spectrum disorder, his mother, a staff member, and an unknown researcher. Results indicated that the participant preferred different social interactions with his mother, as compared to the other assessors. In a follow‐up reinforcer assessment, the social interactions identified as most preferred for each assessor produced higher frequency responding when compared to no consequence or nonmatching preference conditions. Results suggest that preference for social interactions may vary based on the assessor. Implications regarding the impact of the assessor in social preference assessments are discussed.

Recognition of Affective Faces of Different Age Groups

It has been found that valence and arousal are the core affect dimensions in emotional structure. In this study, we hypothesized that there might be differences between different age groups in emotional structure using six facial expression stimuli (angry, disgusted, fearful, neutral, happy, and sad) of three age groups (young, middle-aged, and old). Unlike previous studies asking participants to rate subjective ratings or similarities between stimuli, participants in this study were required to determine whether stimulus pairs were the same or different emotions and reaction time and accuracy were measured for further analyses. We assumed that it would be harder when the stimulus pair is similar whereas it would be easier when the pair is different. The results showed that for the same emotion pair condition, the sad-sad pair had the lowest accuracy and the longest reaction time, while the happiness-happiness pair had the highest accuracy and the shortest reaction time. For the different emotion pairs, angry-disgusted and disgusted-sad was the lowest accuracy and the longest reaction time. For age of the stimuli effect, responses to the old faces had the lowest accuracy and the longest reaction time. The results suggest that identification of emotional stimuli might be affected by emotion category and age. Further study may need to recruit various age groups, because participants in the current study were mostly young adults.

The Dot-Probe Attention Bias Task as a Method to Assess Psychological Well-Being after Anesthesia: A Study with Adult Female Long-Tailed Macaques (Macaca fascicularis)

Understanding the impact routine research and laboratory procedures have on animals is crucial to improving their well-being and to the success and reproducibility of the research they are involved in. Cognitive measures of welfare offer insight into animals’ internal psychological state, but require validation. Attention bias – the tendency to attend to one type of information over another – is a cognitive phenomenon documented in humans and animals that is known to be modulated by affective state (i.e., emotions). Hence, changes in attention bias may offer researchers a deeper perspective of their animals’ psychological well-being. The dot-probe task is an established method for quantifying attention bias in humans (by measuring reaction time to a dot-probe replacing pairs of stimuli), but has yet to be validated in animals. We developed a dot-probe task for long-tailed macaques (Macaca fascicularis) to determine if the task can detect changes in attention bias following anesthesia, a context known to modulate attention and trigger physiological arousal in macaques. Our task included the following features: stimulus pairs of threatening and neutral facial expressions of conspecifics and their scrambled counterparts, two stimuli durations (100 and 1,000 ms), and counterbalancing of the dot-probe’s position on the touchscreen (left and right) and location relative to the threatening stimulus. We tested 8 group-housed adult females on different days relative to being anesthetized (baseline and 1-, 3-, 7-, and 14-days after). At baseline, monkeys were vigilant to threatening content when stimulus pairs were presented for 100 ms, but not 1,000 ms. On the day immediately following anesthesia, we found evidence that attention bias changed to an avoidance of threatening content. Attention bias returned to threat vigilance by the third day postanesthesia and remained so up to the last day of testing (14-days after anesthesia). We also found that attention bias was independent of the type of stimuli pair (i.e., whole face vs. scrambled counterparts), suggesting that the scrambled stimuli retained aspects of the original stimuli. Nevertheless, whole faces were more salient to the monkeys as responses to these trials were generally slower than to scrambled stimulus pairs. Overall, our study suggests it is feasible to detect changes in attention bias following anesthesia using the dot-probe task in nonhuman primates. Our results also reveal important aspects of stimulus preparation and experimental design.

Lateral Entorhinal Cortex Suppresses Drift in Cortical Memory Representations.

Memory retrieval is thought to depend on the reinstatement of cortical memory representations guided by pattern completion processes in the hippocampus. The lateral entorhinal cortex (LEC) is one of the intermediary regions supporting hippocampal-cortical interactions and houses neurons that prospectively signal past events in a familiar environment. To investigate the functional relevance of the activity of the LEC for cortical reinstatement, we pharmacologically inhibited the LEC and examined its impact on the stability of ensemble firing patterns in one of the efferent targets of the LEC, the medial prefrontal cortex (mPFC). When male rats underwent multiple epochs of identical stimulus sequences in the same environment, the mPFC maintained a stable ensemble firing pattern across repetitions, particularly when the sequence included pairings of neutral and aversive stimuli. With LEC inhibition, the mPFC still formed an ensemble pattern that accurately captured stimuli and their associations within each epoch. However, LEC inhibition markedly disrupted its consistency across the epochs by decreasing the proportion of mPFC neurons that stably maintained firing selectivity for stimulus associations. Thus, the LEC stabilizes cortical representations of learned stimulus associations, thereby facilitating the recovery of the original memory trace without generating a new, redundant trace for familiar experiences. Failure of this process might underlie retrieval deficits in conditions associated with degeneration of the LEC, such as normal aging and Alzheimer's disease.SIGNIFICANCE STATEMENT To recall past events, the brain needs to reactivate the activity patterns that occurred during those events. However, such reinstatement of memory traces is not trivial because it goes against the natural tendency of the brain to restructure the activity patterns continuously. We found that dysfunction of a brain region called the LEC worsened the drift of the brain activity when rats repeatedly underwent the same events in the same room and made them behave as if they had never experienced these events before. Thus, the LEC stabilizes the brain activity to facilitate the recovery of the original memory trace. Failure of this process might underlie memory problems in elderly and Alzheimer's disease patients with the degenerated LEC.

Fishnition: Developing Models From Cognition Toward Consciousness.

A challenge to developing a model for testing animal consciousness is the pull of opposite intuitions. On one extreme, the anthropocentric view holds that consciousness is a highly sophisticated capacity involving self-reflection and conceptual categorization that is almost certainly exclusive to humans. At the opposite extreme, an anthropomorphic view attributes consciousness broadly to any behavior that involves sensory responsiveness. Yet human experience and observation of diverse species suggest that the most plausible case is that consciousness functions between these poles. In exploring the middle ground, we discuss the pros and cons of “high level” approaches such as the dual systems approach. According to this model, System 1 can be thought of as unconscious; processing is fast, automatic, associative, heuristic, parallel, contextual, and likely to be conserved across species. Consciousness is associated with System 2 processing that is slow, effortful, rule-based, serial, abstract, and exclusively human. An advantage of this model is the clear contrast between heuristic and decision-based responses, but it fails to include contextual decision-making in novel conditions which falls in between these two categories. We also review a “low level” model involving trace conditioning, which is a trained response to the first of two paired stimuli separated by an interval. This model highlights the role of consciousness in maintaining a stimulus representation over a temporal span, though it overlooks the importance of attention in subserving and also disrupting trace conditioning in humans. Through a critical analysis of these two extremes, we will develop the case for flexible behavioral response to the stimulus environment as the best model for demonstrating animal consciousness. We discuss a methodology for gauging flexibility across a wide variety of species and offer a case study in spatial navigation to illustrate our proposal. Flexibility serves the evolutionary function of enabling the complex evaluation of changing conditions, where motivation is the basis for goal valuation, and attention selects task-relevant stimuli to aid decision-making processes. We situate this evolutionary function within the Temporal Representation Theory of consciousness, which proposes that consciousness represents the present moment in order to facilitate flexible action.

İşitme cihazı kullanıcısı bebeklerin görsel pekiştirmeli konuşmayı ayırt etme yöntemi ile değerlendirilmesi: Olgu serisi

Evaluation of babies with hearing aids using visual reinforced ınfant speech discrimination method: A case series Speech perception measurements are an important part of the audiology test battery. It is important to investigate hearing loss in the early period and to evaluate the auditory pathway in terms of speech perception for appropriate amplification. Due to the level of language development in infants, it is not possible to objectively evaluate speech perception skills with the speech test battery used in adults. It is necessary to use a test battery that gives objective results for the measurement of speech perception in infants. Visual Reinforcement Infant Speech Discrimination (VRISD) method is the most commonly used test technique to evaluate speech discrimination skills in infants. The aim of this study is to evaluate the speech discrimination skills of 3 babies aged 6-18 months, who are hearing aid users, with the VRISD test method. In the VRISD test protocol used in this study, test stimuli were created by matching /a/ with /i/ and /ba/ with /da/ speech stimuli. These stimulus pairs are arranged as one target sound and the other background sound, and they are presented at 70 dB via loudspeaker by creating a repeating sound sequence. Animated video that attracts the attention of the baby was used as visual reinforcement. Speech discrimination skills of 3 babies with bilateral hearing aids were evaluated with the VRISD test, and the results of the cases are presented. As a result of the study, speech discrimination skills of babies with hearing aids will be evaluated with the VRISD test method. These results contribute to habilitation and amplification programming. Keywords: Hearing aid, speech perception, pediatric audiology

Color mismatch and observer metamerism between conventional liquid crystal displays and organic light emitting diode displays, Part II: Adjacent stimuli with a larger field of view

In part I of this study [Opt. Express 29, 12292 (2021)10.1364/OE.418675], 50 human observers matched the color appearance of six color stimuli produced by four smartphone displays, including one conventional liquid crystal display (LCD) and three organic light emitting diode (OLED) displays, to those produced by a reference smartphone OLED display. The matching and reference stimuli had a field of view (FOV) around 4.77° and were 5.72° apart. In this experiment, we carefully designed and built a new apparatus to make the two stimuli adjacent to each other with an FOV around 20.2°. This not only made the viewing condition in the experiment similar to the typical viewing condition of smartphone displays, but also allowed for an easier color matching, resulting in smaller intra- and inter-observer variations. The performance of the four CMFs, however, were not significantly changed with the increase of the FOV. The CIE 2006 2° CMFs still had the best performance in characterizing the color matches, which did not support the recommendation of using 10° CMFs for stimuli with an FOV beyond 4°. Meanwhile, for the pairs of stimuli with matched color appearance, the LCD display always had the greatest chromaticity differences and degrees of observer metamerism among the four displays, regardless of the CMFs. In particular, the chromaticities of the stimuli produced by the LCD display were always shifted towards the -u’+v’ direction in the CIE 1976 u’v’ chromaticity diagram, when calculated using the CIE 1931 CMFs. This implies that the neutral colors shown on LCD displays would have a yellow-green tint on OLED displays, if they were calibrated to the same chromaticities using the CIE 1931 2° CMFs.

Therapeutic application of rTMS in neurodegenerative and movement disorders: A review

Transcranial magnetic stimulation (TMS) is a non-invasive form of brain stimulation that makes use of the magnetic field generated when an electric current passes through a magnetic coil placed over the scalp. It can be applied as a single stimulus at a time, in pairs of stimuli, or repetitively in trains of stimuli (repetitive TMS, rTMS). RTMS can induce changes in brain activity, whose after-effects reflect the processes of long-term potentiation and long-term depression, as certain protocols, namely those using low frequencies (≤1 Hz) seem to suppress cortical excitability, while those using high frequencies (>1 Hz) seem to enhance it. It is a technique with very few and mostly mild side-effects, whose effects can persist for long time periods, and as such, it has been studied as a potential treatment option in a multitude of neurodegenerative diseases, including those affecting movement. Although rTMS has received approval as a treatment strategy of only a few aspects in movement disorders in the latest guidelines, its further use seems to also be promising in their context. In this review, we gathered the available literature on the therapeutic application of rTMS in movement disorders, namely Parkinson’s disease, Amyotrophic Lateral Sclerosis, Huntington’s disease, Dystonia, Tic disorders and Essential Tremor.

Influence of the crossmodal congruency between color and flavor on product evaluations: Evidence from behavioral and oscillatory brain responses

People often associate features or stimuli across senses, and these crossmodal correspondences also function as criteria for judging whether a pair of features or stimuli is crossmodally congruent or incongruent. We conducted two studies to examine whether the crossmodal congruency between a drink color and a flavor could also elicit more positive ratings of this drink. In Study 1, the experimental task was to simultaneously view a photo of a colored drink and to taste a beverage whose flavor was either congruent or incongruent with the color. Consequently, the color-flavor congruent drinks received more positive ratings than the color-flavor incongruent ones. In Study 2, we conducted an EEG experiment to investigate both behavioral and oscillatory brain responses to the crossmodal congruency between the successively presented color and flavor. The results of subjective ratings did not reveal any significant difference between the color-flavor congruent and incongruent stimuli. However, the time–frequency analyses on the EEG data revealed that rating the color-flavor incongruent beverages elicited greater alpha band power in the parietal region, compared to the color-flavor congruent stimuli. Collectively, these findings revealed the influence of color-flavor congruency on the subjective ratings of beverages, and demonstrated how this effect was modulated by the temporal synchrony of the color and flavor cues.

Attentional bias modification for chocolate: Sham-n training as a new control group.

Although attentional bias modification has been shown effective in several appetitive domains, results have been mixed. A major contributor seems to be the choice of control condition. The aim of the present study was to compare attentional bias modification for chocolate against a new control condition, sham-n (neutral or no-contingency) training. Using a modified dot probe protocol, participants (N = 192; 17–30 years) were randomly trained to attend to chocolate pictures, avoid chocolate pictures, or received sham-n training. In the attend and avoid conditions, stimulus pairs consisted of one chocolate and one non-chocolate picture, and probes replaced most often (90/10) chocolate or non-chocolate pictures, respectively. In the sham-n training condition, stimulus pairs consisted of two chocolate or two non-chocolate pictures, and probes replaced pictures within pairs with equal frequency (50/50). Attentional bias for chocolate increased following attend training, decreased following avoidance training, and did not change following sham-n training. The findings clearly demonstrate that both attend and avoidance training alter (in opposite direction) attentional bias for chocolate, whereas sham-n training is inert. This makes sham-n training particularly promising for use in clinical samples who tend to show strong initial biases.

Intensity dependency of peripheral nerve stimulation in spinal LTP induced by paired associative corticospinal-motoneuronal stimulation (PCMS).

Paired associative corticospinal-motoneuronal stimulation (PCMS) induces plasticity at synapses between corticospinal tracts (CSTs) and spinal motoneurons (SMs). We investigated the effects of peripheral nerve electrical stimulation (PNS) intensity on PCMS-induced plasticity. PCMS consisted of 180 paired stimuli of transcranial magnetic stimulation (TMS) over the left primary motor cortex with PNS on the right ulnar nerve at the wrist. We compared effects induced by different PNS intensities: supramaximal, twice and three times sensory threshold intensities. For evaluating efficacy of the synapse between CSTs and SMs, single-pulse TMS was delivered at cervicomedullary junction level, and cervicomedullary motor-evoked potentials (CMEPs) were recorded from the right first-dorsal interosseous muscle before and after PCMS. PCMS with the supramaximal PNS intensity increased CMEP amplitude. The facilitatory effect of PCMS with the supramaximal PNS was larger than those of PCMS with weaker PNS intensities. Sham TMS with the supramaximal PNS showed no CMEP changes after the intervention. PNS intensity of PCMS influences the magnitude of synaptic plasticity induction between the CSTs and SMs at the spinal level, and the supramaximal intensity is the best for induction of long-term potentiation-like effects. The PNS intensity may influence the number of activated SMs by axonal backpropagating pulses with PNS which must overlap with descending volleys induced by TMS.