A novel protocol to investigate motor training-induced plasticity and sensorimotor integration in the cerebellum and motor cortex.

Our group set out to develop a sensitive technique, capable of detecting output changes from the posterior fossa following a motor acquisition task. Transcranial magnetic stimulation (TMS) was applied over the right cerebellar cortex 5 ms in advance of test stimuli over the left cerebral motor cortex (M1), suppressing test motor-evoked potentials (MEPs) recorded in a distal hand muscle. Ten participants typed the letters Z, D, F, and P in randomized 8-letter sequences for ∼15 min, and 10 participants took part in the control condition. Cerebellar-M1 recruitment curves were established before and after the motor acquisition task. Cerebellar inhibition at 50% (CBI50) was defined as the intensity of cerebellar-M1 stimulations that produced MEPs that were 50% of the initial test MEP. Collection also occurred at stimulator intensities 5 and 10% above CBI50. A significant interaction effect of group (experimental and control) vs. time (pre- and postintervention) was observed [F(1,18) = 4.617, P = 0.046]. Post hoc tests showed a significant effect for the learning task in the experimental group [F(1,9) = 10.28, P = 0.01]. Further analysis showed specific disinhibition at CBI50 (P = 0.04), CBI50+5% (P = 0.008), and CBI50+10% (P = 0.01) for the experimental group only. Reaction time (P < 0.001) and accuracy (P = 0.006) improved significantly following practice, implying that disinhibition coincides with motor learning. No changes, however, were seen in the control condition. We conclude that this protocol is a sensitive technique that may be used to study cerebellar disinhibition with motor acquisition in vivo.

TMS stimulus-response asymmetry in left- and right-handed individuals.

There have been inconsistencies in the literature regarding asymmetrical neural control and results of experiments using TMS techniques. Therefore, the aim of this study was to further our understanding of the neural relationships that may underlie performance asymmetry with respect to the distal muscles of the hand using a TMS stimulus-response curve technique. Twenty-four male subjects (12 right handed, 12 left handed) participated in a TMS stimulus-response (S-R) curve trial. Focal TMS was applied over the motor cortex to find the optimal position for the first dorsal interossei muscle and to determine rest threshold (RTh). Seven TMS intensities ranging from 90 to 150 % of RTh were delivered in 10 % increments. One single TMS block consisted of 16 stimuli at each intensity. Peak-to-peak amplitudes were measured and the S-R curve generated. In right-handed subjects, the mean difference in slopes between the right and left hand was -0.011 ± 0.03, while the mean difference between hands in left-handed subjects was -0.049 ± 0.08. Left-handed normalized data in right handers displayed a mean of 1.616 ± 1.019 (two-tailed t test p < 0.05). The left-handed group showed a significant change in the normalized slope as indicated by a mean of 1.693 ± 0.149 (two-tailed t test p < 0.00006). The results found in this study reinforce previous work which suggests that there is an asymmetry in neural drive that exists in both left- and right-handed individuals. However, the results show that the non-dominant motor hemisphere displays a greater amount of excitability than the dominant, which goes against the conventional dogma. This asymmetry indicates that the non-dominant hemisphere may have a higher level of excitation or a lower level of inhibition for both groups of participants.

Alterations in cortical and cerebellar motor processing in subclinical neck pain patients following spinal manipulation.

OBJECTIVE: The purpose of this study was investigate whether there are alterations in cerebellar output in a subclinical neck pain (SCNP) group and whether spinal manipulation before motor sequence learning might restore the baseline functional relationship between the cerebellum and motor cortex. METHODS: Ten volunteers were tested with SCNP using transcranial magnetic stimulation before and after a combined intervention of spinal manipulation and motor sequence learning. In a separate experiment, we tested 10 healthy controls using the same measures before and after motor sequence learning. Our transcranial magnetic stimulation measurements included short-interval intracortical inhibition, long-interval intracortical inhibition, and cerebellar inhibition (CBI). RESULTS: The SCNP group showed a significant improvement in task performance as indicated by a 19% decrease in mean reaction time (P < .0001), which occurred concurrently with a decrease in CBI following the combined spinal manipulation and motor sequence learning intervention (F1,6 = 7.92, P < .05). The control group also showed an improvement in task performance as indicated by a 25% increase in reaction time (P < .001) with no changes to CBI. CONCLUSIONS: Subclinical neck pain patients have altered CBI when compared with healthy controls, and spinal manipulation before a motor sequence learning task changes the CBI pattern to one similar to healthy controls.

Validation of the Fitbit Flex in an Acute Post-Cardiac Surgery Patient Population.

Purpose: This study examined the validity of the Fitbit Flex activity monitor for step count and distance walked among post-cardiac surgery patients. Method: Participants (n=20) from a major urban cardiac surgery centre were recruited 1-2 days before hospital discharge. The Fitbit Flex step count and distance walked outputs and video recording of each participant performing the 6-minute walk test were collected. Fitbit Flex output was compared with criterion measures of manual step count obtained from the video recording and manual measurement of distance walked. Statistical analysis compared the output and criterion measures using paired sample t-tests, Pearson correlation coefficients, Lin's concordance correlations, and Bland-Altman plots. Sub-analysis compared slower walking (<0.8 m/s; n=11) and faster walking (≥0.8 m/s; n=8) group speeds (1 participant was excluded from analysis). Results: Steps counted and distance walked were significantly different between the Fitbit Flex outputs and criterion measures (p<0.05). The Fitbit Flex steps counted and distance walked showed moderate association with manual measure steps counted (r=0.67) and distance walked (r=0.45). Lin's concordance coefficients revealed a lack of agreement between the Fitbit Flex and the criterion measurement of both steps counted (concordance correlation coefficient [CCC]=0.43) and distance walked (CCC=0.36). The percentage of relative error was -18.6 (SD 22.7) for steps counted and 25.4 (SD 45.8) for distance walked. Conclusions: The Fitbit Flex activity monitor was not a valid measure of step count and distance walked in this sample of post-cardiac surgery patients. The lack of agreement between outputs and criterion measures suggests the Fitbit Flex alone would not be an acceptable clinical outcome measure for monitoring walking progression in the early postoperative period.

Objectif : examiner la validité du moniteur d'activité Fitbit Flex pour calculer le compte des pas et la distance parcourue chez des patients après une chirurgie cardiaque. Méthodologie : les chercheurs ont recruté les participants (n=20) dans un grand centre de chirurgie cardiaque urbain un ou deux jours avant leur congé de l'hôpital. Ils ont recueilli les résultats du compte de pas et la distance parcourue à l'aide du moniteur Fitbit Flex et l'enregistrement vidéo de chaque participant qui effectue le texte de marche de six minutes (TM6M). Ils ont comparé les résultats du moniteur Fitbit Flex aux critères du compte manuel des pas obtenus par l'enregistrement vidéo et la mesure manuelle de la distance parcourue. Par l'analyse statistique, ils ont comparé les résultats et les critères à l'aide d'échantillons de tests de Student appariés, du coefficient de corrélation de Pearson, de la corrélation de concordance de Lin et du graphique de Bland-Altman. Ils ont effectué la sous-analyse en comparant la vitesse de marche plus lente (<0,8 m/s; n=11) et plus rapide (≥0,8 m/s; n=8) des groupes (un participant a été exclu de l'analyse). Résultats : le compte de pas et la distance parcourue différaient considérablement entre les résultats du moniteur Fitbit Flex et des critères (p<0,05). Le compte de pas et la distance parcourue calculés à l'aide du moniteur Fitbit Flex ont révélé une association modérée avec la mesure manuelle du compte de pas (r =0,67) et la distance parcourue (r=0,45). Les coefficients de concordance de Lin ont révélé une absence de concordance entre le moniteur Fitbit Flex et les critères pour ce qui est du compte de pas (CCC=0,43) et de la distance parcourue (CCC=0,36). L'erreur relative du compte de pas était de −18,6 (ÉT 22,7) et celle de la distance parcourue, de 25,4 (ÉT 45,8). Conclusions : le moniteur d'activité Fitbit Flex n'est pas une mesure valide du nombre de pas et de la distance parcourue dans cet échantillon de patients après une chirurgie cardiaque. Selon l'absence de concordance entre les résultats et les critères, le moniteur Fitbit Flex ne serait pas une mesure de résultat clinique acceptable pour surveiller la progression de la marche au début de la période postopératoire.

The effects of upper limb posture and a sub-maximal gripping task on corticospinal excitability to muscles of the forearm.

Variations in handgrip force influences shoulder muscle activity, and this effect is dependent upon upper limb position. Previous work suggests that neural coupling between proximal and distal muscles with changes in joint position is a possible mechanism but these studies tend to use artificially constrained postures that do not reflect activities of daily living. The purpose of this study was to examine the effects of upper limb posture on corticospinal excitability to the forearm muscles during workplace relevant arm positions. Motor evoked potentials (MEPs) were elicited in four forearm muscles via transcranial magnetic stimulation at six arm positions (45°, 90° and 120° of humeral elevation in both the flexion and abduction planes). MEPs were delivered as stimulus-response curves (SRCs) at rest and at constant intensity during two gripping tasks. Boltzmann plateau levels were smaller for the flexor carpi radialis in flexion at 45° versus 90° (p=0.0008). Extensor carpi radialis had a greater plateau during flexion than abduction (p=0.0042). Corticospinal excitability to the forearm muscles were influenced by upper limb posture during both the resting and gripping conditions. This provides further evidence that upper limb movements are controlled as a whole rather than segmentally and is relevant for workplace design considerations.