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The role of the contralesional hemisphere during the recovery after a stroke : a short review
No full textBackground.
The cerebral plasticity plays a critical role after damage to central nervous system (CNS), with functional reshaping that underlies the clinical recovery [1]. Neural substrates of “post-lesional” brain plasticity are under intense study, since knowledge of this phenomenon can lead to an appropriate rehabilitation treatment and a successful functional recovery. After a stroke, among the mechanisms of cortical reorganization, there is the increase of activity of contralesional hemisphere [2], as assessed by longitudinal studies using functional imaging and direct cortical stimulation. The role of the unaffected hemisphere during recovery after a stroke is still debated. The aim of this study is to assess how and when the contribution of contralesional hemisphere influences the functional recovery after a cerebrovascular event.
Materials and methods.
A search was performed through the database PubMed, considering the publications between 2004 and 2015. The following key words were used: "stroke", "recovery", "contralesional", "functional magnetic resonance imaging (fMRI)", "transcranial magnetic stimulation (TMS)", with several search strings. All studies concerning adults after their first ischemic or hemorrhagic stroke, within the first six months after the event, were collected. Twenty-four studies were included and a qualitative analysis of the selected studies was performed.
Discussion.
Most of the recent studies confirm that, in the acute phase after a stroke, the hyperactivity of the unaffected hemisphere appears to depend on the extension of the lesion, on the severity of the clinical injury and on the interval from the cerebrovascular event. The underlying pathophysiological mechanism represents an adaptive compensation and may enhance functional recovery. After the third month after a stroke, the persistence of contralesional hyperactivity appears to be a maladaptive process, because it may slow down a functional recovery. Since the unaffected hemisphere is activated also when the ipsilesional limbs are moving, the rehabilitation treatment should respect the different phases of cerebral plasticity and should avoid “overuse”. After a cerebrovascular event, in fact, neurological deficits are caused not only by the lesion, but also by the same mechanisms that underlie the functional recovery, such as diaschisis.
References.
(1) Daffau H. Brain plasticity: from pathophysiological mechanisms to therapeutic applications. Journal of Clinical Neuroscience 2006 Vol 13, 885–97.
(2) Grafkes C. Ward N.S. Cortical reorganization after stroke: how much and how functional? The Neuroscientist 2014 Vol. 20 (1), 56 –70
Emotional training after facial nerve palsy: From theory to practice
Full text linkBackground: Facial expressions can be either voluntary or emotionally controlled. According to the Component Theory of facial expressions, the upper and lower face motor control is behaviorally independent in adults.
In addition, the right and the left face may also exhibit partially independent motor control. Spontaneous facial expressions are organized predominantly across the horizontal facial axis and secondarily across the
vertical axis. Two neural networks for laughter have been recently described in a tractography study. One network is involved in producing emotional laughter (the pregenual anterior cingulate, ventral temporal pole and ventral striatum/nucleus accumbens), while the second one in non-emotional and conversational laughter (frontal operculum and primary motor cortex M1). Smile production and recognition of others’ smiles are encoded in the pregenual anterior cingulate cortex. Unlike hand mirror neurons (MNs), mouthMNs do not receive their visual input from parietal regions. Facial visual input could reach mouth MNs through the ventrolateral prefrontal cortex. Other strong connections derive from limbic structures involved in encoding emotional facial expressions and motivational processing. The mirror mechanism linked to the face motor control is connected with limbic structures, involved in communication and emotions.
Discussion: Peripheral paralysis of the facial nerve compromises facial motility, resulting in alterations in facial expressions, particularly in representing emotionality and non-verbal communication. The primary therapeutic goal of rehabilitation treatment should be to recover expressive gestures, characterized by a biological function and facial expressions for non-verbal communication. A rehabilitation protocol could be
based on neurocognitive exercises with an emotional component (Emotional training) to recover spontaneous and emotional expressive movements. The patient is asked to reproduce the movements to express different emotions by showing drawings or photos of faces, by reproducing the examiner’s expression or by imaging a situation that evoked a specific emotion. The different sensory channels can be used: visual (viewing photos or videos that arouse a particular emotion), auditory (listening to emotionally significantmusic), tactile (touching surfaces that evoke a pleasant feeling) and gustatory (tasting some favorite foods). Even functional exercises, such as producing movements with the mouth (e.g. blowing) or the other parts of the face, can be proposed in contexts with emotional connotations (e.g. imagine blowing candles at a birthday party).
Conclusion: After a facial paralysis, once voluntary contraction appeared, neuromotor treatment should be integrated with emotional training which is a promising rehabilitation proposal that radically changes rehabilitation intervention
Emotional training of facial nerve palsy : a preliminary report
Full text linkIntroduction: Differently from limb muscles, facial muscles motoneurons can be recruited by two descending motor pathways, one arising from the primary motor cortex and the second arising from the midcingulate area (1). Lesions involving the former pathway are associated to voluntary facial paresis, while lesions involving the latter are associated to emotional paresis (2). Patients suffering a voluntary facial paresis cannot voluntary smile, but for example they smile normally in response to jokes. On the contrary, patients suffering an emotional paresis can voluntarily mimic facial expressions, but are unable to produce spontaneous emotional expressions. During rehabilitation after facial nerve lesion, patients are commonly trained to produce symmetric and isolated voluntary movements [e.g. neuromuscular retraining (3)]. In this work we used emotional activation to train facial muscles after peripheral facial nerve palsy, according to the hypothesis that midcingulate area in addition to the primary motor cortex can participate to the motor recovery after facial nerve lesion.
Materials: Tue House-Brackmann scale (HBS) was used to evaluate facial symmetry and synkinesis, both before and after the rehabilitation program.
Methods: Ten patients (36-76 years) suffering a facial nerve lesion (6 Bell's palsy, 2 Ramsay Hunt syndrome, 2 post-surgery palsy) underwent up to 20 physiotherapy sessions. Each session ( 45 minutes long) was led by a physiotherapist. Consecutive sessions were kept at least 3 days apart. The emotional activation of the paretic facial muscles was obtained by asking patients to recall pleasant memories. Patients were guided by the therapist in increasing their awareness of the emotion-evoked movement by concentrating on kinesthesis.
Results: On average, patients started the rehabilitation 80 days after the nerve lesion. At the beginning of the rehabilitation program, patients suffered a moderate facial asymmetry according to the HBS (median HBS score: 3.5; IQR: 3). At the end of the rehabilitation program, HBS score median was reduced to 1 (IQR: 1), indicating a more symmetric face and less severe synkinesis (Wilcoxon test, p = 0.002). Ali patients improved their HBS score.
Discussion: Emotional training, a form of repetitive task-specific training, seems beneficial for people receiving rehabilitation following facial nerve lesion. Tue neural network mediating the emotional training effects could include structures of the limbic system such as the amygdala which are known to project to the facial muscle motoneurons via the midcingulate area (1).
Conclusion: Emotional training of facial muscles led by a physiotherapist is a promising tool for rehabilitation after facial nerve lesions.
References:
1. Morecraft RJ, Louie JL, Herrick JL, Stilwell-Morecraft KS. Cortical
innervation of the facial nucleus in the non-human primate: a new interpretation of the effects of stroke and related subtotal brain trauma on the muscles of facial expression. Brain (2001);124:176-208
2. Gothard KM. Tue amygdalo-motor pathways and the control of facial expressions. Front Neurosci. (2014); 19(8):43
3. Nicastri M, Mancini P, De Seta D, Bertoli G, Prosperini L, Toni D, lnghilleri M, Filipo R. Efficacy of early physical therapy in severe Bell's palsy: a randomized controlled trial. Neurorehabil Neural Repair. (2013);27(6):542-5
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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