Facial Motor Cortex Research Articles

Targeted deep brain stimulation of the motor thalamus improves speech and swallowing motor functions after cerebral lesions.

Speech and swallowing are complex motor acts that depend upon the integrity of input neural signals from motor cortical areas to control muscles of the head and neck. Lesions damaging these neural pathways result in weakness of key muscles causing dysarthria and dysphagia, leading to profound social isolation and risk of aspiration and suffocation. Here we show that Deep Brain Stimulation (DBS) of the motor thalamus improved speech and swallowing functions in two participants with dysarthria and dysphagia. First, we proved that DBS increased excitation of the face motor cortex, augmenting motor evoked potentials, and range and speed of motion of orofacial articulators in n = 10 volunteers with intact neural pathways. Then, we demonstrated that this potentiation led to immediate improvement in swallowing functions in a patient with moderate dysphagia and profound dysarthria as a consequence of a traumatic brain lesion. In this subject and in another with mild dysarthria, we showed that DBS immediately ameliorated impairments of respiratory, phonatory, resonatory, and articulatory control thus resulting in a clinically significant improvement in speech intelligibility. Our data provide first-in-human evidence that DBS can be used to treat dysphagia and dysarthria in people with cerebral lesions.

Post-surgery Rehabilitative Intervention Based on Imitation Therapy and Mouth-Hand Motor Synergies Provides Better Outcomes in Smile Production in Children and Adults With Long Term Facial Paralysis.

Rehabilitation after free gracilis muscle transfer (smile surgery, SS) is crucial for a functional recovery of the smiling skill, mitigating social and psychological problems resulting from facial paralysis. We compared two post-SS rehabilitation treatments: the traditional based on teeth clenching exercises and the FIT-SAT (facial imitation and synergistic activity treatment). FIT-SAT, based on observation/imitation therapy and on hand-mouth motor synergies would facilitate neuronal activity in the facial motor cortex avoiding unwanted contractions of the jaw, implementing muscle control. We measured the smile symmetry on 30 patients, half of whom after SS underwent traditional treatment (control group, CG meanage = 20 ± 9) while the other half FIT-SAT (experimental group, EG meanage= 21 ± 14). We compared pictures of participants while holding two postures: maximum and gentle smile. The former corresponds to the maximal muscle contraction, whereas the latter is strongly linked to the control of muscle strength during voluntary movements. No differences were observed between the two groups in the maximum smile, whereas in the gentle smile the EG obtained a better symmetry than the CG. These results support the efficacy of FIT-SAT in modulating the smile allowing patients to adapt their smile to the various social contexts, aspect which is crucial during reciprocal interactions.

Efficacy and tolerability in patients with chronic facial pain of two consecutive treatment periods of rTMS applied over the facial motor cortex, using protocols differing in stimulation frequency, duration, and train pattern

ObjectiveWe conducted an open-label cross-over study assessing the global effect of two high-frequency protocols of electric-field navigated repetitive transcranial magnetic stimulation (rTMS) targeted to functional facial motor cortex and comparing their efficacy and tolerability in patients with chronic facial pain. Outcome predictors were also assessed. MethodsWe randomized twenty consecutive patients with chronic facial pain (post-traumatic trigeminal neuropathic pain, n=14; persistent idiopathic facial pain, n=4; secondary trigeminal neuralgia, n=2) to receive two distinct 5-day rTMS interventions (10Hz, 2400 pulses and 20Hz, 3600 pulses) separated by six weeks. The target area was assessed by mapping of lower face representation. The primary endpoint was the change in weekly mean of pain intensity (numeric rating scale, NRS) between the baseline and therapy week (1st week), and follow-up weeks (2nd and 3rd weeks) for each rTMS intervention. Response was defined using a combination scale including the patient's global impression of change and continuance with maintenance treatment. ResultsOverall, pain intensity NRS decreased from 7.4 at baseline to 5.9 ten weeks later, after the second rTMS intervention (p=0.009). The repetition of the treatment had a significant effect (F=4.983, p=0.043) indicating that the NRS scores are lower during the second four weeks period. Eight (40%) patients were responders, 4 (20%) exhibited a modest effect, 4 (20%) displayed no effect, and 4 (20%) experienced worsening of pain. High disability and high pain intensity (>7) predicted a better outcome (p=0.043 and p=0.045). Female gender, shorter duration of pain and low Beck Anxiety Inventory scores showed a trend towards a better outcome (p=0.052, 0.060 and 0.055, respectively). ConclusionsHigh-frequency rTMS targeted to face M1 alleviates treatment resistant chronic facial pain. Repeated treatment improves the analgesic effect. A protocol with higher frequency (above 10Hz), longer session duration (more than 20 minutes) and higher number of pulses (above 2400 pulses/session) did not improve the outcome. The results support early consideration of rTMS.

Topological Alterations in White Matter Structural Networks in Blepharospasm

AbstractBackgroundAccumulating evidence indicates regional structural changes in the white matter (WM) of brains in patients with blepharospasm (BSP); however, whether large‐scale WM structural networks undergo widespread reorganization in these patients remains unclear.ObjectiveWe investigated topology changes and global and local features of large‐scale WM structural networks in BSP patients compared with hemifacial spasm (HFS) patients or healthy controls (HCs).MethodsThis cross‐sectional study applied graph theoretical analysis to assess deterministic diffusion tensor tractography findings in 41 BSP patients, 41 HFS patients, and 41 HCs. WM structural connectivity in 246 cortical and subcortical regions was assessed, and topological parameters of the resulting graphs were calculated. Networks were compared among BSP, HFS, and HCs groups.ResultsCompared to HCs, both BSP and HFS patients showed alterations in network integration and segregation characterized by increased global efficiency and modularity and reduced shortest path length. Moreover, increased nodal efficiency in multiple cortical and subcortical regions was found in BSP and HFS patients compared with HCs. However, these differences were not found between BSP and HFS patients. Whereas all participants showed highly similar hub distribution patterns, BSP patients had additional hub regions not present in either HFS patients or HCs, which were located in the primary head and face motor cortex and basal ganglia.ConclusionsOur findings suggest that the large‐scale WM structural network undergoes an extensive reorganization in BSP, probably due to both dystonia‐specific abnormalities and facial hyperkinetic movements. © 2021 International Parkinson and Movement Disorder Society

Role of cutaneous and proprioceptive inputs in sensorimotor integration and plasticity occurring in the facial primary motor cortex

Previous studies investigating the effects of somatosensory afferent inputs on cortical excitability and neural plasticity often used transcranial magnetic stimulation (TMS) of hand motor cortex (M1) as a model, but in this model it is difficult to separate out the relative contribution of cutaneous and muscle afferent input to each effect. In the face, cutaneous and muscle afferents are segregated in the trigeminal and facial nerves, respectively. We studied their relative contribution to corticobulbar excitability and neural plasticity in the depressor anguli oris M1. Stimulation of trigeminal afferents induced short-latency (SAI) but not long-latency (LAI) afferent inhibition of face M1, while facial nerve stimulation evoked LAI but not SAI. Plasticity induction was observed only after a paired associative stimulation protocol using the facial nerve. Physiological differences in effects of cutaneous and muscle afferent inputs on face M1 excitability suggest they play separate functional roles in behaviour. The lack of conventional muscle spindles in face muscles raises the question of how sensory input from the face is used to control muscle activation. In 16 healthy volunteers, we probed sensorimotor interactions in face motor cortex (fM1) using short-afferent inhibition (SAI), long-afferent inhibition (LAI) and LTP-like plasticity following paired associative stimulation (PAS) in the depressor anguli oris muscle (DAO). Stimulation of low threshold afferents in the trigeminal nerve produced a clear SAI (P<0.05) when the interval between trigeminal stimulation and transcranial magnetic stimulation (TMS) of fM1 was 15-30ms. However, there was no evidence for LAI at longer intervals of 100-200ms, nor was there any effect of PAS. In contrast, facial nerve stimulation produced significant LAI (P<0.05) as well as significant facilitation 10-30 minutes after PAS (P<0.05). Given that the facial nerve is a pure motor nerve, we presume that the afferent fibres responsible were those activated by the evoked muscle twitch. The F-wave in DAO was unaffected during both LAI and SAI, consistent with their presumed cortical origin. We hypothesize that, in fM1, SAI is evoked by activity in low threshold, presumably cutaneous afferents, whereas LAI and PAS require activity in (higher threshold) afferents activated by the muscle twitch evoked by electrical stimulation of the facial nerve. Cutaneous inputs may exert a paucisynaptic inhibitory effect on fM1, while proprioceptive information is likely to target inhibitory and excitatory polysynaptic circuits involved in LAI and PAS. Such information may be relevant to the physiopathology of several disorders involving the cranio-facial system.

Predictive Value of Intraoperative Facial Motor Evoked Potentials in Vestibular Schwannoma Surgery Under 2 Anesthesia Protocols.

We sought to validate the feasibility of facial motor evoked potential (FMEP) in facial nerve (FN) monitoring during vestibular schwannoma (VS) surgery under 2 anesthesia protocols and to examine its value for postoperative prognosis. This prospective study included 106 patients with VS who underwent microsurgical excision between May 2014 and November 2016 at the Beijing Tiantan Hospital, Capital Medical University, China. All patients were investigated for FMEP elicited by transcranial electrical stimulation in the contralateral facial motor cortex. The patients randomly received total intravenous anesthesia or combined intravenous-inhalation anesthesia. Postoperative FN function was evaluated 7-10 days after surgery (short-term) and at the last follow-up (long-term) using the House-Brackmann (HB) grading system. HB grades 1 and 2 were deemed satisfactory, whereas HB grades 3-6 were deemed unsatisfactory. The value of the final-to-start FMEP ratio for predicting short-term and long-term postoperative FN functions was examined. Valid FMEPs were obtained in 97 patients, which were recorded from the mentalis muscle. The FMEP amplitude ratio was significantly correlated with short-term and long-term postoperative FN functions. Receiver operating characteristic curve analysis showed that the FMEP ratio cut-off values of 77.4% (area under the curve= 0.797) and 56.9% (area under the curve= 0.900) predicted satisfactory FN function 7-10 days after surgery and at the last follow-up, respectively. No statistically significant difference was found in FMEP quantitative parameters between the 2 anesthesia protocols. The FMEP amplitude ratio is a valuable predictor for postoperative FN function. FMEP ratio ≥57% is predictive of satisfactory long-term FN function.

Representational precision in visual cortex reveals outcome encoding and reward modulation during action preparation

According to ideomotor theory, goal-directed action involves the active perceptual anticipation of actions and their associated effects. We used multivariate analysis of fMRI data to test if preparation of an action promotes precision in the perceptual representation of the action. In addition, we tested how reward magnitude modulates this effect. Finally, we examined how expectation and uncertainty impact neural precision in the motor cortex. In line with our predictions, preparation of a hand or face action increased the precision of neural activation patterns in the extrastriate body area (EBA) and fusiform face area (FFA), respectively. The size of this effect of anticipation predicted individuals' efficiency at performing the prepared action. In addition, increasing reward magnitude increased the precision of perceptual representations in both EBA and FFA although this effect was limited to the group of participants that learned to associate face actions with high reward. Surprisingly, examination of representations in the hand motor cortex and face motor cortex yielded effects in the opposite direction. Our findings demonstrate that the precision of representations in visual and motor areas provides an important neural signature of the sensorimotor representations involved in goal-directed action.

Intraoperative continuous monitoring of facial motor evoked potentials in acoustic neuroma surgery.

The preservation of facial nerve function is one of the primary objectives in acoustic neuroma surgery. We detail our method of continuous intraoperative facial motor evoked potential (MEP) monitoring and present criteria for the preservation of facial nerve function to avoid postoperative facial nerve palsy. Our study population was comprised of 15 patients who did not (group 1), and 20 who did (group 2) undergo facial MEP monitoring during surgery to remove acoustic neuromas. In group 2, we continuously stimulated the facial motor cortex at 5- or 10-s intervals throughout surgery. Electromyograms (EMGs) were recorded from the contralateral orbicularis oculi- and orbicularis oris muscles. Optimal anode and cathode placement was at the facial motor cortex and the vertex, respectively. Postoperative facial palsy occurred in 8 of the 15 group 1 patients; in 2 it improved to grade II at 6 months after the operation. Of the 20 group 2 patients, 7 suffered postoperative facial palsy. At 6 months after the operation, their facial nerve function was normal. At the end of the operation, the ratio of the amplitude of the supramaximal EMG to the amplitude at the dural opening was 39.6 % in patients with- and 94.3 % in patients without transient postoperative facial palsy. Continuous facial MEP monitoring not only alerts to surgical invasion of the facial nerves but also helps to predict postoperative facial nerve function. To preserve a minimum amplitude ratio of 50 %, even transient postoperative facial palsy must be avoided. MEP monitoring is an additional useful modality for facial nerve monitoring during acoustic neuroma surgery.

Reanimating the paralyzed face

Facial animation is an essential part of human communication and one of the main means of expressing emotions, indexing our physiologic state and providing nonverbal cues. The loss of this important human quality due to facial paralysis can be devastating and is often associated with depression, social isolation and poor quality of life. Interruption of the neuromuscular pathway from the facial motor cortex to the facial muscles is the common causative factor in facial paralysis resulting from various etiologies. Restoring tone, symmetry and movement to the paralyzed face requires timely nerve grafting intervention in cases of reversible paralysis and the transfer of functional muscle units in irreversible paralysis. We review recent advances in these techniques.

P 20. Corticobulbar projection and intracortical circuits in the facial motor cortex innervating lower facial muscles in healthy humans

Despite the importance of facial muscles in social life and their frequent and disabling involvement in stroke or movement disorders, conclusive data concerning bilaterality, symmetry and hemisphere dominance in the control of lower facial muscles are not available yet. In addition, the role of intracortical circuits in the modulation of resting and active facial muscles is still debated. (1) To reassess controversy about the symmetry of cortical output to lower facial muscles, arising from the left and right hemisphere. (2) To clarify whether intracortical excitability modulates the ipsi-and contralateral corticobulbar projection, depending on the muscle state and on the stimulated hemisphere. In nine healthy subjects, left and right hemisphere were tested using single and paired pulse TMS methods to probe hot spot, motor evoked potentials (MEPs) latencies and amplitudes as well as short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the ipsi-and contralateral depressor anguli oris (DAO) muscles both at rest and during activation at 10% of maximal voluntary contraction. Resting and active motor thresholds (RMT and AMT, respectively) were determined following TMS of both hemispheres. Test and conditioning stimuli were 120% and 70% of motor threshold, respectively, and interstimulus intervals (ISIs) were 2 ms for SICI and 10 ms for ICF. Student’s paired t -test, ANOVA and post hoc t -test have been performed for single paired pulse TMS on the left and right hemispheres. Resting and active MEPs were evoked bilaterally in the relaxed and active DAO following left and right hemisphere stimulations. Student’s paired t test showed no differences between left and right hemisphere as for hot spot, RMT, AMT, MEP amplitudes and onset latencies. In both muscle states, the contralateral MEP had a significantly shorter latency ( p = 0.005) and larger amplitude ( p = 0.02) than the ipsilateral MEP, with no significant differences according to the side of the stimulated hemisphere. Repeated measures ANOVA showed a significant effect of the paired pulse protocol ( p < 0.001) at rest and during voluntary contraction, regardless the side of the stimulated hemisphere. Post hoc analysis showed, in both muscle states and for both hemispheres, significant SICI ( p < 0.01) at 2 ms and ICF ( p < 0.05) at 10 ms. SICI effects were smaller in the ipsilateral respect to the contralateral DAO at rest ( p = 0.003) and during voluntary contraction (p = 0.032); ICF was reduced ipsilaterally only in the resting state ( p = 0.037). The amount of SICI and ICF was significantly smaller during voluntary contraction in the ipsi-and contralateral DAO ( p = 0.026 and p = 0.005, respectively). TMS applied to the left and right facial motor cortex evokes, in the DAO muscle, bilateral and asymmetric MEPs, with contralateral predominance regardless of the stimulated hemisphere. SICI and ICF are present bilaterally at rest and during voluntary activation and show similar extent following stimulation of both hemispheres. In conclusion, corticobulbar responses as well as intracortical excitability of the left and right facial motor cortex innervating lower facial muscles show similar physiological properties. These data may provide further insight into studies of pathologies affecting the facial motor system. This research was founded by Fondazione Italiana Sclerosi Multipla (FISM 2011/R/17).

A Functional Magnetic Resonance Imaging Paradigm to Identify Distinct Cortical Areas of Facial Function

Irreversible facial paralysis can be surgically treated by importing both a new neural and a new motor muscle supply. Various donor nerves can be used. If a nerve supply other than the facial nerve is used, the patient has to adapt to generate a smile. If branches of the fifth cranial nerve are used, the patient has to learn to clench teeth and smile. Currently, controversy exists regarding whether a patient develops a spontaneous smile if a nerve other than the facial nerve is used. The authors postulate that brain adaptation in facial palsy patients can occur because of neural plasticity. The authors aimed to determine whether functional magnetic resonance imaging could topographically differentiate activity between the facial nerve- and the trigeminal nerve-related cortical areas. A new paradigm of study using functional magnetic resonance imaging based on blood oxygen level-dependent signal activation was tested on 15 voluntary healthy subjects to find a sensitive localizer for teeth clenching and smiling. Subjects smiled to stimulate the facial nerve-related cortex, clenched their jaws to stimulate the trigeminal nerve-related cortex, and tapped their finger as a control condition. Smiling and teeth clenching showed distinct and consistent areas of cortical activation. Trigeminal and facial motor cortex areas were found to be distinct areas with minimal overlapping. The authors successfully devised a functional magnetic resonance imaging paradigm effective for activating specific areas corresponding to teeth clenching and smiling. This will allow accurate mapping of cortical plasticity in facial reanimation patients.

Intracortical circuits, sensorimotor integration and plasticity in human motor cortical projections to muscles of the lower face

Previous studies of the cortical control of human facial muscles documented the distribution of corticobulbar projections and the presence of intracortical inhibitory and facilitatory mechanisms. Yet surprisingly, given the importance and precision in control of facial expression, there have been no studies of the afferent modulation of corticobulbar excitability or of the plasticity of synaptic connections in the facial primary motor cortex (face M1). In 25 healthy volunteers, we used standard single- and paired-pulse transcranial magnetic stimulation (TMS) methods to probe motor-evoked potentials (MEPs), short-intracortical inhibition, intracortical facilitation, short-afferent and long-afferent inhibition and paired associative stimulation in relaxed and active depressor anguli oris muscles. Single-pulse TMS evoked bilateral MEPs at rest and during activity that were larger in contralateral muscles, confirming that corticobulbar projection to lower facial muscles is bilateral and asymmetric, with contralateral predominance. Both short-intracortical inhibition and intracortical facilitation were present bilaterally in resting and active conditions. Electrical stimulation of the facial nerve paired with a TMS pulse 5-200 ms later showed no short-afferent inhibition, but long-afferent inhibition was present. Paired associative stimulation tested with an electrical stimulation-TMS interval of 20 ms significantly facilitated MEPs for up to 30 min. The long-term potentiation, evoked for the first time in face M1, demonstrates that excitability of the facial motor cortex is prone to plastic changes after paired associative stimulation. Evaluation of intracortical circuits in both relaxed and active lower facial muscles as well as of plasticity in the facial motor cortex may provide further physiological insight into pathologies affecting the facial motor system.

10. Sensorimotor interaction and motor learning in facial muscles

Background and aim : Integration of sensory information with motor output is thought to be important in motor learning. In limb muscles, this is studied using the short afferent inhibition (SAI) paradigm, to assess sensorimotor interaction, and paired associative stimulation (PAS), to evaluate LTP-like plasticity. As far as we know, SAI and PAS paradigms have never been used in the territory of the cranial nerves. The present study was aimed at testing in normal subjects whether sensorimotor interaction and LTP-like plasticity can be observed in facial muscles as well as in limb muscles. Methods : Motor evoked potentials (MEPs) were evoked in the depressor angulis oris (DAO) muscle of 7 subjects. MEPs were recorded from the contralateral DAO at rest and during 10% maximal voluntary contraction (active condition). SAI was tested in 5 subjects, by pairing electrical stimulation (ES, intensity 3 times the perceptual threshold) of the facial nerve, with magnetic stimulation (TMS, 120% of motor threshold intensity) of the facial motor cortex. Intervals between ES and TMS were 5, 10, 15, 20, 25 and 30 ms. The LTP-like plasticity protocol (200 pairs of ES and TMS, 20 ms ISI, at 0.25 Hz) was tested in X subjects by evoking twenty MEPs in both resting and active conditions, before and at 0, 20 and 30 min after paired stimulation. Results : Facial nerve stimulation in the SAI paradigm had no significant affect on MEP amplitude, either in the active or in the relaxed DAO muscle. By contrast MEP amplitude at rest showed a trend of facilitation (p < 0,072) after the PAS protocol administration. When tested at rest this effect was observed at baseline and after 10 min. On the contrary MEP amplitude recorded during activity was significantly enhanced at 10 (p < 0,026) and 30 (p < 0,014) minutes after PAS. There was a significant difference between the time course in resting and active conditions (p < 0,019). Conclusions : These data show that there is no short latency afferent inhibition in the facial motor cortex, yet despite this, there is evidence for maintained LTP-like plasticity. Further studies are needed to understand how and why PAS works in facial muscles despite the absence of SAI. A larger sample is also required to confirm the PAS effect on resting DAO MEPs. A second point to be clarified is why the PAS time course at rest is different from that operating during active condition.

Cortical representation sites of mimic movements after facial nerve reconstruction: A functional magnetic resonance imaging study

To describe cortical reorganization after classic hypoglossal-facial nerve anastomosis (HFA) (four patients), hypoglossal-facial nerve jump anastomosis (HFJA) (three patients), and facial nerve interpositional graft (FNIG) (three patients). Prospective case series. Functional magnetic resonance imaging (fMRI) was performed during lip and tongue movement using a block or an event-related design. Despite the presence of some intersubject variability, the following general brain activation patterns were revealed: As expected, lip movements after FNIG led to selective brain activation in the original facial motor cortex, and lip movements after HFA were associated with activation in the hypoglossal motor cortex. Following HFJA, lip movements resulted in overlapping activation encompassing both the original facial and the hypoglossal motor cortex, but tongue movements led solely to strong activation within the original hypoglossal motor cortex. In contrast, tongue movements after HFA were associated with strong activation in the original hypoglossal motor cortex and weaker activation in the facial motor cortex. Direct facial nerve repair (FNIG) leads to restoration of the original cortical activation. A cross nerve suture (HFA or HFJA) changes cortical activation and leads to different patterns of cortical activation during lip and tongue movements.

Pleasure detection by online brain–computer interface

This paper seeks to elucidate the design and implementation of an instrumentation amplifier, filters, LabVIEW-based spike detection, and automatic spike counting to detect pleasure sensation in the rat using invasive BCI. This method involved sites related to pleasure, and after acquiring signals from the ventral pallidum, facial motor cortex, and orbitofrontal cortex, these signals were analyzed to assess the pleasure sensation in the rat. The results illustrated a decreased spike rate in the motor and orbitofrontal cortices and an increased spike rate in the ventral pallidum during pleasure. The pleasure detection experiment was conducted four times to obtain the mean values of spike rates. The motor cortex had 9 spikes/s, the orbitofrontal cortex had 18 spikes/s and the ventral pallidum had 34 spikes/s. The correlation coefficient is above 78%, effectiveness of the experiment.

Decoding spoken words using local field potentials recorded from the cortical surface

Pathological conditions such as amyotrophic lateral sclerosis or damage to the brainstem can leave patients severely paralyzed but fully aware, in a condition known as ‘locked-in syndrome’. Communication in this state is often reduced to selecting individual letters or words by arduous residual movements. More intuitive and rapid communication may be restored by directly interfacing with language areas of the cerebral cortex. We used a grid of closely spaced, nonpenetrating micro-electrodes to record local field potentials (LFPs) from the surface of face motor cortex and Wernicke's area. From these LFPs we were successful in classifying a small set of words on a trial-by-trial basis at levels well above chance. We found that the pattern of electrodes with the highest accuracy changed for each word, which supports the idea that closely spaced micro-electrodes are capable of capturing neural signals from independent neural processing assemblies. These results further support using cortical surface potentials (electrocorticography) in brain–computer interfaces. These results also show that LFPs recorded from the cortical surface (micro-electrocorticography) of language areas can be used to classify speech-related cortical rhythms and potentially restore communication to locked-in patients.

Facial motor cortex plasticity in patients with unilateral peripheral facial paralysis

Hand motor representation area expands towards the area of the perioral facial motor cortex in patients with peripheral facial paralysis (PFP) and in hemifacial spasm cases treated with botulinum toxin. In this current study, we aimed to investigate the changes both in the ipsilateral and contralateral facial motor cortex areas in patients with PFP with transcranial magnetic stimulation (TMS). Thirty healthy individuals and 41 patients with unilateral PFP with partial or total axonal degeneration participated in this study. Motor evoked potentials (MEPs) of perioral muscles elicited by TMS of the intracranial portion of the facial nerve and motor cortex, were recorded. TMS was delivered through a figure-of-eight coil. Mapping of the cortical representation of perioral muscles were also studied in 13 of 41 patients and in 10 of control subjects. Mean amplitude of the intact perioral MEPs elicited by the ipsilateral hemisphere TMS, was significantly higher in patients than the control subjects. There was also a mild enlargement of the mean cortical representation area of intact perioral muscles on both hemispheres though it was not significant. We have concluded that there was a cortical reorganization in the hemisphere contralateral to the paralytic side resulting in an increase at corticofugal output related to intact perioral muscles.

Acoustical development of the human baby cry: Anatomical and social factors

We investigated the acoustical development of the human baby cry based on our two-stage hypothesis, which holds that two distinct factors affect the development of the baby cry. First, humans possess the cortico-bulbar pathway connecting the face motor cortex and the medullary respiratory and vocal centers. This pathway is absent in nonhuman primates and other mammals. We postulate that the myelinization of this pathway would change the acoustic characteristics of the baby cry. Second, after neuroanatomical maturation enabled variable cry patterns, the social relationships with caregivers should differentiate the acoustical patterns of the baby cry. This should lead to family-specific cry patterns. To test the two-stage hypothesis, we recorded ten newborn babies until they were 1 year old. In all babies, the cry pattern was very simple up to 2 weeks, while after 1 month, the pattern became temporally and spectrally complex, suggesting neuroanatomical changes. At three months, we asked the mothers to classify the cries of their own babies into three categories: sleepy, hungry, and wet diaper. There were no acoustic patterns common to their classifications, suggesting that baby cry semantics are family-specific. These results support our two-stage hypothesis of cry development. [Work supported by JST and JSPS.]

Phase Coupling in a Cerebro-Cerebellar Network at 8–13 Hz during Reading

Words forming a continuous story were presented to 9 subjects at frequencies ranging from 5 to 30 Hz, determined individually to render comprehension easy, effortful, or practically impossible. We identified a left-hemisphere neural network sensitive to reading performance directly from the time courses of activation in the brain, derived from magnetoencephalography data. Regardless of the stimulus rate, communication within the long-range neural network occurred at a frequency of 8-13 Hz. Our coherence-based detection of interconnected nodes reproduced several brain regions that have been previously reported as active in reading tasks, based on traditional contrast estimates. Intriguingly, the face motor cortex and the cerebellum, typically associated with speech production, and the orbitofrontal cortex, linked to visual recognition and working memory, additionally emerged as densely connected components of the network. The left inferior occipitotemporal cortex, involved in early letter-string or word-specific processing, and the cerebellum turned out to be the main forward driving nodes of the network. Synchronization within a subset of nodes formed by the left occipitotemporal, the left superior temporal, and orbitofrontal cortex was increased with the subjects' effort to comprehend the text. Our results link long-range neural synchronization and directionality with cognitive performance.

The vibrissal motor output following severing and repair of the facial nerve in the newborn rat reorganises less than in the adult

This study examined the ability of facial motoneurons and motor cortex to reorganise their relationship with the somatic musculature following the severing and repair of the facial nerve in rats at birth. In each adult rat, the organisation of the facial nucleus and the cortical motor output corresponding to the normal side were compared with those corresponding to the reinnervated side. Labelling was used to reveal reinnervation-induced long-term changes in the motoneuron pool supplying vibrissal muscles. Cortical motor output was assessed by mapping the vibrissal movement area extension and thresholds evoked by intracortical microstimulation. After facial nerve reinnervation: (i) the proportion of labelled cell profiles decreased by 85.2% of that in the control side and cortical representation of vibrissal movement decreased by 66.3% of that in control hemispheres; (ii) the reorganised vibrissal representation was shrunken to the medialmost portion of the normal vibrissal representation and there was a medial extension of the forelimb representation, and a more modest lateral extension of eye representation, into the vibrissal territory; (iii) the normal pattern of contralateral vibrissal movement was observed in only 10% of the vibrissal sites, whereas ipsilateral vibrissal movement was found in 53% of the vibrissal sites; (iv) there was an increase in the mean threshold required to evoke contralateral vibrissal movement (32.5+/-11.1 vs. 20.5+/-6.9 microA). Thresholds to evoke other types of movement were similar to normal. These changes indicate that an incomplete motor axon regeneration at birth does not restore normal innervation and normal cortical control over the vibrissal muscles.