Two different mirror neuron networks: The sensorimotor (hand) and limbic (face) pathways.

The vast majority of functional studies investigating mirror neurons (MNs) explored their properties in relation to hand actions, and very few investigated how MNs respond to mouth actions or communicative gestures. Since hand and mouth MNs were recorded in two partially overlapping sectors of the ventral precentral cortex of the macaque monkey, there is a general assumption that they share a same neuroanatomical network, with the parietal cortex as a main source of visual information. In the current review, we challenge this perspective and describe the connectivity pattern of mouth MN sector. The mouth MNs F5/opercular region is connected with premotor, parietal areas mostly related to the somatosensory and motor representation of the face/mouth, and with area PrCO, involved in processing gustatory and somatosensory intraoral input. Unlike hand MNs, mouth MNs do not receive their visual input from parietal regions. Such information related to face/communicative behaviors could come from the ventrolateral prefrontal cortex. Further strong connections derive from limbic structures involved in encoding emotional facial expressions and motivational/reward processing. These brain structures include the anterior cingulate cortex, the anterior and mid-dorsal insula, orbitofrontal cortex and the basolateral amygdala. The mirror mechanism is therefore composed and supported by at least two different anatomical pathways: one is concerned with sensorimotor transformation in relation to reaching and hand grasping within the traditional parietal-premotor circuits; the second one is linked to the mouth/face motor control and is connected with limbic structures, involved in communication/emotions and reward processing.

Individual and social learning processes involved in the acquisition and generalization of tool use in macaques.

Macaques can efficiently use several tools, but their capacity to discriminate the relevant physical features of a tool and the social factors contributing to their acquisition are still poorly explored. In a series of studies, we investigated macaques' ability to generalize the use of a stick as a tool to new objects having different physical features (study 1), or to new contexts, requiring them to adapt the previously learned motor strategy (study 2). We then assessed whether the observation of a skilled model might facilitate tool-use learning by naive observer monkeys (study 3). Results of study 1 and study 2 showed that monkeys trained to use a tool generalize this ability to tools of different shape and length, and learn to adapt their motor strategy to a new task. Study 3 demonstrated that observing a skilled model increases the observers' manipulations of a stick, thus facilitating the individual discovery of the relevant properties of this object as a tool. These findings support the view that in macaques, the motor system can be modified through tool use and that it has a limited capacity to adjust the learnt motor skills to a new context. Social factors, although important to facilitate the interaction with tools, are not crucial for tool-use learning.

In vitro biocompatibility of oxirane/polyol dental composites with promising physical properties.

OBJECTIVES: Visible light cure oxirane/polyol resins of Cyracure UVR-6105 with pTHF-250 has been previously shown useful for development of dental composites. This oxirane/polyol (4016) in combination with other oxiranes were formulated into composites (4016E, 4016G and 4016GB) containing 72.9-74.9% quartz filler. The main objective of the study was to evaluate some of the physical properties and the biocompatibility of the composites. RESULTS: PhotoDSC analysis of composites demonstrated twice the enthalphy values of Z100 (31J/g). Composites 4016E and 4016G showed compressive strengths similar to Z100 (337+/-35Mpa), P>0.05. Discs of composite 4016E, containing Epon 825 oxirane (E), and composite 4016G containing Araldite GY 281 oxirane (G) were non-cytotoxic (-) while the composite 4016GB, containing G and Ebecryl 1830 (B), was mildly (+) cytotoxic to L929 cells in the agar diffusion assay. Seven-day extracts of 4016GB composite were cytotoxic while extracts of 4016E and 4016G were less cytotoxic to L929 cells in the MTT assay. Extracts were obtained from 7 day incubations of composite (3 cm(2) surface area/ml) in acetone or ethanol/saline (1:20) at 37 degrees C. All composite extracts were non-mutagenic to Ames strains TA100, TA98, TA97a and TA1535. The overall results with composite 4016GB suggest that leachable components were cytotoxic but non-mutagenic. With the exception of oxirane components, G and E, the oxirane Cyracure UVR-6105 and other components were non-mutagenic. From cytotoxicity studies, the photoinitiator, Sarcat CD 1012, was the most cytotoxic (TC(50)=14 microM) component. Components G (TC(50)=17 microM), E (TC(50)=50 microM) and B (TC(50)=151 microM) were significantly (p < 0.05) more cytotoxic than Cyracure UVR-6105 (1488 microM) and the polyol, pTHF-250 (TC(50)=6072 microM). SIGNIFICANCE: Favorable results obtained with composites 4016G and 4016E indicates that suitable oxirane/polyol formulations can be designed and optimized for development of dental composites with acceptable mechanical properties and biocompatibility. However, leachable analysis of extracts obtained from longer incubation periods is needed before final conclusions could be drawn about the leachability of oxirane components.

Projections from the superior temporal sulcus to the agranular frontal cortex in the macaque.

The aim of this study was to investigate the organization of the projections from the superior temporal sulcus (STS) to the various areas forming the agranular frontal cortex. Injections of retrograde neuronal tracers were made in the various agranular areas, in nine macaque monkeys. The results showed that two rostral premotor areas, F6 (pre-SMA) and F7, and the ventrorostral part of area F2 (F2vr) are targets of projections from the upper bank of the STS (uSTS). F6 and the dorsorostral part of F7 (supplementary eye field, SEF) are targets of projections from the rostral part of the uSTS, corresponding to the so-called 'superior temporal polysensory area' (STP). In contrast, the ventral part of area F7 (not including the SEF) and F2vr are targets of afferents from the caudal part of the uSTS. Ventral F7 is the target of weak afferents from the caudalmost and dorsalmost part of the uSTS (area 7a), whilst F2vr is the target of projections from a relatively more rostral and ventral sector of the uSTS, close to the fundus of the sulcus. This sector should correspond to area MST. In conclusion, F6 and SEF receive high order information from STP, whereas ventral F7 and F2vr receive information from areas of the dorsal visual stream.

Changes in lymphocyte subsets in depressed HIV-infected patients without antiretroviral therapy.

The authors studied the effects of major depression on lymphocyte subsets by comparing depressed and matched control subjects in a population of HIV-seropositive outpatients not treated with antiretroviral therapy. Twelve patients with major depression, as determined by the Structured Clinical Interview for DSM-III-R, were assessed in comparison with 15 matched nondepressed control subjects. Flow cytometric analysis of peripheral blood lymphocyte subsets together with immunological parameters were performed. In HIV-infected patients, major depression was significantly (P=0.001) associated with a reduction in natural killer cell absolute count and percentage. This report suggests that depression may alter the natural killer cell population that provides a cytotoxic defense against HIV infection.

In vitro inhibition of enamel demineralization by a polymerizable amphiphilic film.

An amphiphilic coating is configured as a substantive film that has a tendency for an in-plane two-dimensional polymerization. This coating is hypothesized to protect enamel from in vitro acid decalcification, assessed through the following artificial caries model. Three regions on labial enamel of eight bovine incisors were treated with an acid resistant varnish (A), the amphiphilic coating (B), or left undisturbed (C), and the teeth were immersed for 3 wk in lactic acid gel. Mineral loss (deltaZ-value) was determined by a cross-sectional microhardness technique. deltaZ-values (mean +/- SD; volume percent mineral-microm) were: -4 +/- 24 (A), 29 +/- 69 (B), and 7,372 +/- 1,766 (C). deltaZ-value of the uncoated enamel (C) was significantly different from the other groups. Scanning electron microscopy showed enamel etched pattern from citric acid, and the coating firmly attached on enamel surface. This amphiphilic coating can inhibit enamel decalcification under the present experimental condition.

Balance training for persons with functionally unstable ankles.

STUDY DESIGN: A nonrandomized 2-group pretest-posttest design. OBJECTIVES: To determine the effects of a 4-week balance training program during stance on a single leg. BACKGROUND: Individuals who have experienced multiple episodes of inversion ankle sprains often participate in balance training programs. Balance training is performed to treat existing proprioceptive deficits and to restore ankle joint stability, presumably by retraining altered afferent neuromuscular pathways. The effectiveness of such programs on individuals with functionally unstable ankles has yet to be established. METHODS AND MEASURES: Prior to and following training, subjects with self-reported functionally unstable ankles (5 women and 8 men, mean age = 21.9 +/- 3.1 years) and nonimpaired subjects (6 women and 7 men, mean age = 21.2 +/- 2.5 years) completed a static balance assessment for both limbs as well as the ankle joint functional assessment tool questionnaire (AJFAT). The subjects from both groups participated in a unilateral, multilevel, static and dynamic balance training program 3 times a week for 4 weeks. Subjects from the experimental group trained only the involved limb, and the nonimpaired group trained a randomly selected limb. A stability index (SI) was calculated during the balance assessment to indicate the amount of platform motion. Compared to low stability indices, high stability indices indicate greater platform motion during stance and therefore less stability. RESULTS: Following training, subjects from both groups demonstrated significant improvements in balance ability. When balance was assessed at a low resistance to platform tilt (stability level 2), the posttraining scores of both the subjects with unstable ankles (mean SI = 2.63 +/- 1.92) and the nonimpaired subjects (mean SI = 2.69 +/- 2.32) were significantly better than their pretraining scores (mean SIs = 5.93 +/- 3.65 and 4.67 +/- 3.43, respectively). Assessed at a high resistance to platform tilt (stability level 6), the posttraining scores of both subjects with unstable ankles (mean SI = 1.27 +/- 0.66) and the nonimpaired subjects (mean SI = 1.37 +/- 0.66) were significantly better than their pretraining scores (mean SIs = 2.30 +/- 1.88 and 2.04 +/- 1.43, respectively). Additionally, the posttraining AJFAT scores of subjects with unstable ankles (25.78 +/- 3.80) and the nonimpaired subjects (29.15 +/- 5.27) were significantly greater than their pretraining scores (17.11 +/- 3.44 and 22.92 +/- 5.22, respectively), indicating an overall improvement in perceived ankle joint functional stability. CONCLUSIONS: This study suggests that balance training is an effective means of improving joint proprioception and single-leg standing ability in subjects with unstable and nonimpaired ankles.

Knee joint laxity and neuromuscular characteristics of male and female soccer and basketball players.

Anterior cruciate ligament injuries are occurring at a higher rate in female athletes compared with their male counterparts. Research in the area of anterior cruciate ligament injury has increasingly focused on the role of joint proprioception and muscle activity in promoting knee joint stability. We measured knee joint laxity, joint kinesthesia, lower extremity balance, the amount of time required to generate peak torque of the knee flexor and extensor musculature, and electromyographically assessed muscle activity in 34 healthy, collegiate-level athletes (average age, 19.6 +/- 1.5 years) who played soccer or basketball or both. Independent t-tests were used to determine significant sex differences. Results revealed that women inherently possess significantly greater knee joint laxity values, demonstrate a significantly longer time to detect the knee joint motion moving into extension, possess significantly superior single-legged balance ability, and produce significantly greater electromyographic peak amplitude and area of the lateral hamstring muscle subsequent to landing a jump. The excessive joint laxity of women appears to contribute to diminished joint proprioception, rendering the knee less sensitive to potentially damaging forces and possibly at risk for injury. Unable to rely on ligamentous structures, healthy female athletes appear to have adopted compensatory mechanisms of increased hamstring activity to achieve functional joint stabilization.

Effects of muscular fatigue on knee joint laxity and neuromuscular characteristics of male and female athletes.

OBJECTIVE: To elucidate the effects of muscular fatigue on knee joint laxity and the neuromuscular characteristics of male and female athletes. We were particularly interested in determining whether such effects would be more pronounced in female athletes than in males participating in the same sport. DESIGN AND SETTING: Subjects were assessed on 4 dependent variables during a rested and an isokinetically induced muscular fatigue state. We ensured that posttesting measurements were obtained in the fatigued state by testing only 2 dependent variables after each exercise bout. SUBJECTS: We recruited male (n = 17) and female (n = 17) subjects from a population of healthy collegiate basketball and soccer players. MEASUREMENTS: MEASURED DEPENDENT VARIABLES WERE AS FOLLOWS: anterior tibial translation, kinesthesia determined by assessing the threshold to detection of passive motion moving into knee flexion and extension; lower extremity balance ability quantified through a stability index value; and the electromyography-measured muscle activity of 6 knee-stabilizing muscles. RESULTS: In response to muscular fatigue, subjects demonstrated an overall decrease in the ability to detect joint motion moving into the direction of extension, an increase in the onset of contraction time for the medial hamstring and lateral gastrocnemius muscles, and an increase in the first contraction area of the vastus medialis and vastus lateralis muscles. Additionally, the increase in area of the vastus lateralis was greater for the males compared with the females. CONCLUSIONS: Our results suggest that both male and female athletes exhibit decrements in proprioceptive ability and alterations in muscular activity subsequent to muscular fatigue.

Proprioception of the ankle and knee.

Proprioception and accompanying neuromuscular feedback mechanisms provide an important component for the establishment and maintenance of functional joint stability. Neuromuscular control and joint stabilisation is mediated primarily by the central nervous system. Multisite sensory input, originating from the somatosensory, visual and vestibular systems, is received and processed by the brain and spinal cord. The culmination of gathered and processed information results in conscious awareness of joint position and motion, unconscious joint stabilisation through protective spinal-mediated reflexes and the maintenance of posture and balance. Clinical research aimed at determining the effects of articular musculoskeletal injury, surgery and rehabilitation, on joint proprioception, neuromuscular control and balance has focused on the knee and ankle joints. Such studies have demonstrated alterations in proprioception subsequent to capsulo-ligamentous injury, partial restoration of proprioceptive acuity following ligamentous reconstruction, and have suggested beneficial proprioceptive changes resulting from comprehensive rehabilitation programmes.