Motor Cortex Response to Pleasant Odor Perception and Imagery: The Differential Role of Personality Dimensions and Imagery Ability.

Background: Neuroimaging studies have shown a complex pattern of brain activation during perception of a pleasant odor and during its olfactory imagery. To date, little is known regarding changes in motor cortex excitability during these tasks. Bergamot essential oil (BEO) is extensively used in perfumes and cosmetics for its pleasantness. Therefore, to further our understanding of the human sense of smell, this study aimed to investigate the effect of perception and imagery of a pleasant odor (BEO) on motor cortex using Transcranial magnetic stimulation (TMS). Materials and Methods: We examined the primary motor cortex (M1) excitability during perception of a pleasant odor (BEO) or perception of odorless saline (experiment 1). Furthermore, we tested the effect of olfactory imagery (OI) of BEO on corticospinal excitability (experiment 2). The increase in motor evoked potential (MEP) amplitude was correlated with personality dimensions scores, pleasantness, vividness, and general imagery ability. Results: The results indicate that the corticospinal excitability changed after both perception and imagery of a pleasant odor (BEO). The correlation analysis shows an association with neuroticism personality trait (experiment 1) and with general olfactory imagery ability (experiment 2). Conclusion: Both perception of a pleasant odor and its olfactory imagery modulate motor cortex excitability. The enhanced brain activation is affected by specific individual characteristics. Overall, our findings provide physiological evidence for a complex interaction between the olfactory and motor systems.

Acute social and somatic stress alters cortical metaplasticity probed with non-invasive brain stimulation in humans.

Studying the neuronal mechanisms that govern the cortical adaptations to acute stress is critical for understanding the development of neuropsychiatric diseases. Homeostatic plasticity stabilizes the neural activity in which a previous synaptic event drives subsequent synaptic plasticity. In this study, we evaluated the effect of acute stress induced with the socially evaluated cold pressor test (SECPT) on cortical metaplasticity in humans using a non-invasive brain stimulation protocol. After being exposed to the SECPT and control stress conditions, 30 healthy participants were tested for cortical metaplasticity assessed with changes in the amplitude of the motor evoked potential (MEP) induced by a single-pulse transcranial magnetic stimulation (TMS). Cortical metaplasticity was induced by combining priming with cathodal tDCS (cTDCS) followed by a sub-threshold 1-Hz repetitive stimulation (rTMS) test session. Our results showed that SECPT induced cardiovascular adaptations (increase in systolic, diastolic blood pressure, and heart rate), indicating that SECPT effectively induced acute stress. Also, in our experiments stimulation of subjects with 1-Hz rTMS after they had undergone the SECPT condition induced inhibition of MEP whereas 1-Hz rTMS administered after the control condition induced a facilitatory (physiologic) response pattern. Here we observed that acute stress impairs homeostatic metaplasticity. The dysfunctional regulation of cortical plastic changes after stress could play a pivotal role in the pathogenesis of neurological and psychiatric diseases.

Exploring the Gender Difference and Predictors of Perceived Stress among Students Enrolled in Different Medical Programs: A Cross-Sectional Study.

Female medical students seem to experience higher level of perceived stress. Moreover, there is a lack of research examining perceived stress in students enrolled in different medical programs. We analyzed the association between temperament traits, optimism, self-esteem, and perceived stress of students pursuing a Doctor of Medicine (MD) degree and students pursuing a Doctor of Podiatric Medicine (DPM) degree. A cross-sectional study was conducted of two cohorts: allopathic medical students (N = 154) and the podiatric medical students (N = 150). Students anonymously completed the Perceived Stress Scale (PSS-10), Temperament Evaluation of Memphis, Pisa, Paris, and San Diego Auto Questionnaire (TEMPS-A), Rosenberg Self-Esteem Scale, and Life Orientation Test-Revised (LOT-R). We analyzed differences in the two cohort of students and predictors of perceived stress. There were no differences in the overall perception of stress between both cohorts (allopathic medical students: 18.83 ± 0.56; podiatric medical students: 19.3 ± 0.72; p = 0.4419). Women reported higher perceived stress in both programs (allopathic medical students: p = 0.0.038; podiatric medical students: p = 0.0.038). In both allopathic and podiatric medical students, the cyclothymic temperaments and anxious traits were positive predictors while hyperthymic temperaments and optimism traits were negative predictors of perceived stress. The level of perceived stress experienced by students pursuing different doctoral degrees in healthcare is similar. Regardless of the curriculum differences, female students experience higher perceived stress and there is evidence for similarities in predictors amongst allopathic and podiatric medical students.

Nonoperative Management of Hallux Limitus Using a Novel Forefoot Orthosis.

Hallux limitus is among the most common arthritides of the foot and ankle, with increasing incidence in the aging population. Despite its prevalence and disease burden, treatment of the condition remains poorly understood. Many patients will fail initial conservative management, whereas controversy exists surrounding indications for and outcomes of surgery. The present study sought to examine the impact of a novel forefoot orthosis on foot function, pain, and plantar pressure distributions in patients with symptomatic hallux limitus. Nineteen adult patients completed a questionnaire consisting of the 23-item Foot Function Index and a 10-point visual analogue scale measuring pain. Standing pedobarographic maps were generated using a foot scanning system. Participants were instructed to wear the orthosis in athletic shoes for 4 weeks. Eighteen participants (94.7%) experienced improvements in foot function and pain, with 12 (63.2%) reporting complete resolution of pain at the end of the 4-week trial. Mean Foot Function Index scores improved significantly from 43.0% at baseline to 11.0% with the orthosis (p < .001). Similarly, mean visual analogue scale pain scores decreased significantly from 4.87 to 1.18 (p < .001). Pedobarographic analysis while wearing the orthosis demonstrated increased ability of participants to bear weight on the arthritic hallux metatarsophalangeal joint and restoration of physiologic stance. Compared to existing products, the device was well tolerated and did not require footwear modifications or impede normal gait. Overall, the orthosis offers an appealing solution to patients dissatisfied with existing treatment options as well as those who may be averse to or ineligible for surgery.

Affective Temperament Traits and Age-Predicted Recreational Cannabis Use in Medical Students: A Cross-Sectional Study.

The use of cannabis among college students is increasing. Cannabis abuse has been proposed to be associated with personality dimensions. However, there are currently no known studies on the relationship of temperament traits and recreational cannabis use among college students. This is a cross-sectional study that investigated 328 students at a Podiatric Medical College. We evaluated the association between temperament and recreational cannabis use by the students. Temperament was investigated using the Memphis, Pisa, Paris and San Diego Auto- Questionnaire (TEMPS-A (short version)). Additionally, we assessed demographics variables and perceived stress in the context of cannabis use, and analyzed the findings using logistic regression. The prevalence of recreational cannabis use was 8.45%. Recreational cannabis use among these students was highly associated with irritable and cyclothymic temperament traits. There was no association between recreational cannabis use and perceived stress, and demographic variables or other substance use. Furthermore, logistic regression analysis indicated that higher scores in cyclothymic or irritable temperament traits are significant predictors for recreational cannabis use. Our study has identified key temperament traits, with a strong association with recreational use of cannabis of the studied student population. Our findings are useful in designing screening and educational strategies directed towards increasing the wellbeing of medical students.

Effects of taurine acute intake on cortical excitability and post-exercise facilitation: A TMS study.

Taurine (TAU) is one of the most abundant amino acids in the brain. It has many important physiological functions. The effects of TAU supplementation on brain function need to be further characterized in humans. The purpose of this study was to investigate whether a single dose of Taurine (TAU) intake would modulate corticospinal excitability and post-exercise facilitation (PEF) of the motor evoked potentials (MEP).

Exploring the effect of adaptogenic Rhodiola Rosea extract on neuroplasticity in humans.

OBJECTIVES: Rhodiola rosea extract is one of the most common herbal treatment for stress. Its mechanism of action in humans still need to be determined. We investigated the effect of a single dose intake of Rhodiola rosea extract on the plastic after-effects induced by anodal and cathodal motor cortex transcranial Direct Current Stimulation in humans. METHODS: Twenty-eight healthy volunteers were required to intake 500 mg of either RRE or placebo. Transcranial Magnetic Stimulation was used to investigate cortical excitability. Motor threshold, recruitment of motor-evoked potentials, cortical silent period, short-interval intracortical inhibition and intracortical facilitation were assessed at different time points. Spinal excitability and peripheral nerve conduction were measured by F-response and M-wave. Furthermore, we assessed the modulation of cortical plasticity using transcranial direct current stimulation after-effects on Motor Evoked Potentials amplitudes. RESULTS: Rhodiola rosea extract acute intake prevented cathodal transcranial Direct Current Stimulation-induced Long-term depression-like plasticity. The extract intake did not affect cortical excitability. CONCLUSIONS: Our findings suggest that a single oral dose of Rhodiola rosea extract intake modulates cortical plasticity in humans preventing the activity-dependent reduction in the efficacy of neuronal synapses. These results suggest that the adaptogenic and antidepressant effects of Rhodiola rosea extract might be based on its modulation of brain plasticity.

Motor facilitation during observation of implied motion: Evidence for a role of the left dorsolateral prefrontal cortex.

The phenomenon of motor resonance (the increase in motor cortex excitability during observation of actions) has been previously described. Transcranial magnetic stimulation (TMS) studies have demonstrated a similar effect during perception of implied motion (IM). The left dorsolateral prefrontal cortex (DLPFC) seems to be activated during action observation. Furthermore, the role of this brain area in motor resonance to IM is yet to be investigated. Fourteen healthy volunteers were enrolled into the study. We used transcranial direct current stimulation (tDCS) to stimulate DLPFC aiming to investigate whether stimulation with different polarities would affect the amplitude of motor evoked potential collected during observation of images with and without IM. The results of our experiment indicated that Cathodal tDCS over the left DLPFC prevented motor resonance during observation of IM. On the contrary, anodal and sham tDCS did not significantly modulate motor resonance to IM. The current study expands the understanding of the neural circuits engaged during observation of IM. Our results are consistent with the hypothesis that action understanding requires the interaction of large networks and that the left DLPFC plays a crucial role in generating motor resonance to IM.

Modulation of sensorimotor circuits during retrieval of negative Autobiographical Memories: Exploring the impact of personality dimensions.

Autobiographical Memory (AM) retrieval refers to recollection of experienced past events. Previous Transcranial Magnetic Stimulation (TMS) studies have shown that presentation of emotional negative stimuli affects human motor cortex excitability resulting in larger motor evoked potentials (MEPs). Up to date no TMS studies have been carried out in order to investigate the effect of personal memories with negative emotional value on corticospinal excitability. In this study we hypothesized that negative AM retrieval will modulate corticomotor excitability and sensorimotor integration as determined by TMS neurophysiological parameters. Furthermore, we investigated whether TMS responses during retrieval of negative AM are associated with specific personality traits. Twelve healthy subjects were asked to recall either a negative or a neutral AM across two different days in a randomized order. During this memory retrieval, the following TMS parameters were recorded: MEPs; Short- interval intracortical inhibition (SICI) and Intracortical facilitation (ICF); Short-latency afferent inhibition (SAI) and Long- latency afferent inhibition (LAI). Personality traits were assessed by using the Big Five scale. Statistical analysis was performed using factorial ANOVAs and multiple linear regression models. When compared to retrieval of neutral AM, recollection of negative AM induced a larger increase in MEP amplitude, an increase in ICF, and a decrease in SAI. The neuroticism personality trait was a significant predictor of the MEP amplitude increase during retrieval of negative AM. Altogether these results indicate that cortical excitability and sensorimotor integration are selectively modulated by the valence of AM. These results provide the first TMS evidence that the modulatory effect of the AM retrieval is associated with specific personality traits.

Hypericum perforatum extract modulates cortical plasticity in humans.

BACKGROUND: Hypericum perforatum (HYP) extract is one of the most commonly used complementary alternative medicines (CAMs) for the treatment of mild-to-moderate depression. Non-invasive brain stimulation protocols can be used to investigate the effect of psychoactive substances on the human brain. In this study, we explored the effect of a single dose of HYP extract (WS 5570) intake on corticospinal excitability and plasticity in humans. METHODS: Twenty-eight healthy subjects were required to intake 900 mg of either HYP extract or placebo. Cortical excitability was assessed using single and paired transcranial magnetic stimulation (TMS). The electrophysiological parameters of motor threshold, recruitment of motor-evoked potentials (MEPs), cortical silent period (CSP), short interval intracortical inhibition (SICI), and intracortical facilitation (ICF) were tested before and 2 and 5 h after the oral intake. Spinal and neuromuscular excitability and peripheral nerve excitability were measured by F response and M-wave. Cortical plasticity was induced using transcranial direct current stimulation (tDCS). Subjects received either HYP extract or placebo before anodal and cathodal tDCS of the primary motor cortex. Plasticity was assessed by MEP amplitudes. RESULTS: HYP extract reversed cathodal tDCS-induced long-term depression (LTD)-like plasticity into facilitation, as compared to placebo. HYP extract did not have a significant effect on anodal tDCS-induced plasticity and TMS measures of motor cortex and spinal/neuromuscular excitability. CONCLUSIONS: Our findings suggest that a single oral dose of HYP extract modulates cortical plasticity in healthy subjects and provide new insight into its possible mechanism of action in humans.

Valeriana officinalis Root Extract Modulates Cortical Excitatory Circuits in Humans.

BACKGROUND: Valeriana officinalis extract (VE) is a popular herbal medicine used for the treatment of anxiety and sleep disorders. Although the anxiolytic and sedative effects are mainly attributed to the modulation of GABA-ergic transmission, the mechanism of action has not been fully investigated in humans. Noninvasive brain stimulation protocols can be used to elucidate the mechanisms of action of psychoactive substances at the cortical level in humans. In this study, we investigated the effects of a single dose of VE on cortical excitability as assessed with transcranial magnetic stimulation (TMS). METHODS: Fifteen healthy volunteers participated in a double-blind, randomized, cross-over, placebo-controlled study. Subjects were required to take either 900 mg of VE (valerenic acid 0.8%) or placebo (an equal dose of vitamin E). Motor cortex excitability was studied by single and paired TMS before and at 1 h and 6 h after the oral administration. Cortical excitability was assessed using different TMS parameters: resting motor threshold, motor-evoked potential amplitude, cortical silent period, short-interval intracortical inhibition, and intracortical facilitation. Furthermore, we assessed sensorimotor integration by short-latency and long-latency afferent inhibition. RESULTS: We found a significant reduction in ICF, without any significant changes in other TMS measures of motor cortex excitability. The amount of ICF returned to baseline value 6 h after the intake of the VE. CONCLUSION: A single oral dose of VE modulates intracortical facilitatory circuits. Our results in healthy subjects could be predictive markers of treatment response in patients and further support the use of pharmaco-TMS to investigate the neuropsychiatric effects of herbal therapies in humans.

Motor-Evoked Potentials of the Abductor Hallucis Muscle and Their Relationship with Foot Arch Functional Anatomy.

BACKGROUND: The present study aimed to investigate the correlation between abductor hallucis (AH) muscle motor evoked potential (MEP) amplitude and foot arch anatomy. METHODS: Twelve healthy individuals underwent foot arch measurement using a digital photographic technique and measurements of cortical excitability using transcranial magnetic stimulation applied on the cortical representation area of the right AH muscle. Truncated foot length and dorsal height were then measured and used to create the arch height index (AHI). Resting motor threshold, MEP amplitude (using a stimulation intensity of 110% resting motor threshold), and cortical silent period duration were also measured. RESULTS: Mean ± SE values were as follows: truncated foot length, 16.72 ± 0.3 cm; dorsal height, 5.62 ± 0.13 cm; AHI, 0.34 ± 0.01; resting motor threshold, 81.6% ± 2.12%; MEP amplitude, 0.71 ± 0.1 mV; and cortical silent period duration, 108.05 ± 0.45 msec. A significant correlation was found between MEP amplitude and AHI (Spearman's rho: P < .01). CONCLUSIONS: These results indicate that AH muscle functional neuroanatomy measurements are reliable and might be used by clinicians and therapists to investigate foot arch physiology and monitor the efficacy of treatments and rehabilitative protocols.

Caffeinated energy drink intake modulates motor circuits at rest, before and after a movement.

Energy drinks are thought to improve certain aspects of athletic and cognitive performances. Moreover, less is understood about physiological mechanisms that might underlie these effects. The aim of this study was to examine the influence of sugar-free energy drink (SFED) ingestion on corticomotor excitability and plasticity. Fourteen college students consumed a commercially available SFED or a "dummy" drink. By using Transcranial magnetic Stimulation (TMS) we investigated resting motor threshold (RMT), motor evoked potential (MEP) amplitude and cortical silent period (CSP). Paired-pulse stimulation was used to assess short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). Sensorimotor integration was investigated with the short- and long-afferent inhibition paradigms (SAI and LAI). Cortical plasticity was studied with the paired associative stimulation (PAS) paradigm. In addition, we examined the effect of SFED on simple reaction time (RT), pre-movement facilitation and post-exercise facilitation (PEF). SFED consumption decreased ICF, shortened RT, increased pre-movement facilitation and PEF of the motor evoked potentials. These results demonstrate that SFED consumption induced a shorter RT that is paralleled by changes in cortical excitability at rest, prior and after a non-fatiguing muscle contraction. These acute changes in brain function might be of relevance in understanding the mechanisms underlying the enhancement of psychomotor performance.

Academic stress disrupts cortical plasticity in graduate students.

Medical education is a time of high stress and anxiety for many graduate students in medical professions. In this study, we sought to investigate the effect of academic stress on cortical excitability and plasticity by using transcranial magnetic stimulation (TMS). We tested two groups (n = 13 each) of healthy graduate medical students (mean age 33.7 ± 3.8 SE). One group was tested during a final exam week (High-stress group) while the other group was tested after a break, during a week without exams (Low-stress group). Students were required to fill the Perceived Stress Scale-10 (PSS) questionnaire. We investigated resting motor threshold (RMT), motor evoked potential (MEP) amplitude and cortical silent period (CSP). The paired-pulse stimulation paradigm was used to assess short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). Long-term potentiation (LTP)-like plasticity was evaluated with paired associative stimulation (PAS-25). There was no between-group difference in cortical excitability. On the contrary, during examination period, levels of perceived stress were significantly higher (p= .036) and the amount of cortical plasticity (60 min after PAS) was significantly lower (p = .029). LTP-like plasticity (60 min after PAS) was inversely correlated with perceived stress in the High-stress group. The present study showed LTP-like plasticity was reduced by examining stress in graduate students. Our results provide a new opportunity to objectively quantify the negative effect of academic and examination stress on brain plasticity.

Modulation of prefrontal cortex with anodal tDCS prevents post-exercise facilitation interference during dual task.

In this study we aimed to investigate whether transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) reduces interference effects of a dual task (DT) on post-exercise facilitation (PEF) of the motor evoked potentials. Anodal tDCS reversed the DT interference on PEF after a non-fatiguing isometric contraction. We conclude that anodal DLPFC tDCS improves the ability to allocate attentional resources and modulates plastic adaptations across brain systems.

Anodal cerebellar tDCS modulates lower extremity pain perception.

BACKGROUND: Previous studies have investigated the use of transcranial direct current stimulation (tDCS) for pain management. The studies investigating therapeutic neuromodulation with tDCS for lower extremity pain are scarce and inconclusive. OBJECTIVE: The aim of the present study was to analyze the effects of cerebellar tDCS on lower extremity sensory and pain thresholds in healthy volunteers. METHODS: This was a single-blind crossover repeated-measure study. Utilizing randomized conditions, we examined the effects of anodal, cathodal and sham stimulation of the right cerebellum in 14 healthy volunteers on sensory and pain thresholds which were induced in the right leg using electrical stimulation. tDCS intensity was 2 mA and the duration of the stimulation was 10 minutes. RESULTS: After anodal cerebellar stimulation the pain threshold of the ipsilateral leg was increased (p < 0.01). We could not detect any significant pain modulation with cathodal or sham stimulation (p > 0.05). Furthermore, no significant modulation of the sensory threshold was detected after anodal, cathodal or sham cerebellar tDCS (p > 0.05). CONCLUSIONS: Our results indicate that anodal cerebellar tDCS with a reference electrode positioned over the buccinator area modulates pain processing in the ipsilateral leg. Further investigation is required to evaluate possible application in chronic pain patients.

Observation of implied motion in a work of art modulates cortical connectivity and plasticity.

Following the discovery of mirror neurons, much attention has been de-voted to understanding the neural responses evoked by observation of implied motion in works of art. Neuroimaging studies have demonstrated that dorsal premotor cortex (PMd) is commonly involved during observation of movements but the role of the inhibitory and excitatory connections between PMd and primary motor cortex (M1) during observation of implied motion remains uncertain. In this study, using high and low frequency repetitive transcranial magnetic stimulation (rTMS), we examined PMd-M1 connectivity and plasticity during observation of Michelangelo's frescos with and without implied motion (Sistine Chapel, 1508-1512). We found that observation of implied motion in a painting specifically reduces the activity of inhibitory PMd-M1 connections. On the contrary PMd-M1 facilitatory connections, as examined by means of 5-Hz rTMS, were not modulated during observation of the painting. Our data suggest that observation of implied motion in a painting modulates PMd-M1 connectivity and plasticity. These results are consistent with the hypothesis that art with implied motion might be used as a plasticity-based intervention in rehabilitation.

Influence of dual-task on postexercise facilitation: a transcranial magnetic stimulation study.

In this study we investigated the effect of a dual task (DT) comprised of a nonfatiguing leg and foot extension coupled with a calculation task on postexercise facilitation (PEF) of motor evoked potentials (MEPs) tested by using transcranial magnetic stimulation (TMS). Twelve right-handed healthy subjects participated in the study. They were required to perform a motor task, a cognitive task and a DT. The motor task consisted of extending the right leg and foot for 30 sec at 20% of the maximal voluntary contraction. The cognitive task consisted of a 30-sec backward calculation. In the DT condition, motor and cognitive tasks were performed concurrently. Resting motor threshold and 10 MEPs were collected before and immediately after each task. TMS was delivered to the motor hot spot of the right vastus lateralis and tibialis anterior (TA) muscles. Results showed that exercise induced a significant PEF in both VL and TA muscles while calculation was not associated with significant PEF. Furthermore, DT was associated with lack of significant PEF in both muscles (VL, 116.1%±9.6%; TA, 115.7%±9%). Our data indicates DT interference on corticospinal excitability after a nonfatiguing exercise. Our experimental paradigm may be used to address postexercise motor cortex plastic adaptations induced by motor and cognitive tasks of different complexity in sport, aging and neuropsychiatric diseases.

An Investigation of Diabetes Knowledge Levels Between Newly Diagnosed Type 2 Diabetes Patients in Galway, Ireland and New York, USA: A Cross-Sectional Study.

Management of diabetes mellitus (DM) involves podiatrists as the primary practitioners engaged in prevention and treatment of lower limb pathology. Patients must first possess adequate knowledge to engage in effective self-management. A knowledge assessment of a DM cohort has never before been conducted in Ireland. The primary research objective was to determine the existence of gaps in specific areas of DM-related knowledge between type 2 DM (T2DM) patients in Galway (GW) and New York (NY). A cross-sectional study compared DM-related knowledge levels between 2 cohorts over a 10-week period. Participants were recently (<3 years) diagnosed with T2DM, were based in general podiatry clinics in GW or NY and had no current or previous diabetic foot ulceration (DFU) or other DM-related foot pathology. Participants were recruited by convenience sampling. A purpose-designed 28-item closed questionnaire was completed by both cohorts to assess knowledge differences. Fifty-two subjects were recruited (GW, n = 32; NY, n = 20). The mean age was 61 ± 10 years; 56% were male. Significant differences were found between cohorts relating to individual questions; specifically regarding knowledge of glycemic control (P = .002) and frequency of self-monitoring of blood glucose (P = .003). Inappropriate foot care practices across both cohorts were highlighted. No significant intercohort differences in particular survey sections were identified. The scores in the systemic and podiatric sections of the questionnaire highlight patterns of common health misconceptions and some highly inappropriate foot care practices respectively across the entire sample. In particular, the dearth of patient awareness regarding uncontrolled blood glucose and its relationship to DFU development, amputation, and associated morbidity is shown to be an area of concern; this must be addressed a priori.