Corticomuscular Coherence Is Tuned to the Spontaneous Rhythmicity of Speech at 2-3 Hz

Human speech features rhythmicity that frames distinctive, fine-grained speech patterns. Speech can thus be counted among rhythmic motor behaviors that generally manifest characteristic spontaneous rates. However, the critical neural evidence for tuning of articulatory control to a spontaneous rate of speech has not been uncovered. The present study examined the spontaneous rhythmicity in speech production and its relationship to cortex–muscle neurocommunication, which is essential for speech control. Our MEG results show that, during articulation, coherent oscillatory coupling between the mouth sensorimotor cortex and the mouth muscles is strongest at the frequency of spontaneous rhythmicity of speech at 2–3 Hz, which is also the typical rate of word production. Corticomuscular coherence, a measure of efficient cortex–muscle neurocommunication, thus reveals behaviorally relevant oscillatory tuning for spoken language.Peer reviewe

Impairment of Auditory-Motor Timing and Compensatory Reorganization after Ventral Premotor Cortex Stimulation

Integrating auditory and motor information often requires precise timing as in speech and music. In humans, the position of the ventral premotor cortex (PMv) in the dorsal auditory stream renders this area a node for auditory-motor integration. Yet, it remains unknown whether the PMv is critical for auditory-motor timing and which activity increases help to preserve task performance following its disruption. 16 healthy volunteers participated in two sessions with fMRI measured at baseline and following rTMS (rTMS) of either the left PMv or a control region. Subjects synchronized left or right finger tapping to sub-second beat rates of auditory rhythms in the experimental task, and produced self-paced tapping during spectrally matched auditory stimuli in the control task. Left PMv rTMS impaired auditory-motor synchronization accuracy in the first sub-block following stimulation (p<0.01, Bonferroni corrected), but spared motor timing and attention to task. Task-related activity increased in the homologue right PMv, but did not predict the behavioral effect of rTMS. In contrast, anterior midline cerebellum revealed most pronounced activity increase in less impaired subjects. The present findings suggest a critical role of the left PMv in feed-forward computations enabling accurate auditory-motor timing, which can be compensated by activity modulations in the cerebellum, but not in the homologue region contralateral to stimulation

Biomechanical evaluation of cell-loaded and cell-free hydroxyapatite implants for the reconstruction of segmental bone defects.

none6Porous hydroxyapatite (HA) scaffoldings are currently used in tissue engineering for bone reconstruction. When this osteoconductive biomaterial is combined with osteoprogenitor cells, it acquires osteoinductive features which accelerate and improve bone formation in vivo. The aim of our study was to assess the mechanical properties of HA-bone complexes undergoing indentation tests, and relate stiffness to composition and structure as examined by micro X-ray. To this purpose, 35-mm tibia diaphyseal resections were performed in sheep. Gaps were filled using porous HA cylinders. Implants were loaded with autologous bone marrow stromal cells (BMSC); cell-free cylinders were used as control. After 8 weeks, bone tissue was found within the internal macropores of cell-loaded HA carriers, and in control implants, bone formation was mostly limited to the outer surface. As assessed by indentation testing the stiffness values of bone-HA composites were halfway between those of HA scaffoldings and tibia bone. Cell-loaded implants were stiffer than cell-free ones. In a cell-loaded implant we also analyzed the variation of stiffness along the main axis of the tibia.P. Chistolini;I. Ruspantini;P. Bianco;A. Corsi;R. Cancedda;R. QuartoP., Chistolini; I., Ruspantini; P., Bianco; A., Corsi; Cancedda, Ranieri; Quarto, Rodolf

Analysis of the mechanical properties of in vitro reconstructed epidermis: preliminary results

Human epidermis can be reconstructed in vitro and is currently used in autografts for the treatment of severe, extensive burns and pigmentation disorders. However, there are neither international standards nor a common nomenclature for engineered tissues. The paper discusses the results of a preliminary study on human cultured epidermis to assess its mechanical tensile strength, and to eventually establish mechanical evaluation criteria that will enable test and comparison of the behaviour of different engineered tissue products. To perform uniaxial tension tests a traditional testing machine was adapted, and dedicated sample holding frame and grips designed