SPRi analysis of molecular interactions of mApoE-functionalized liposomes as drug delivery systems for brain diseases.

The application of liposomes (LPs) to central nervous system disorders could represents a turning point in the therapy and quality of life of patients. Indeed, LPs have demonstrated their ability to cross the blood-brain barrier (BBB) and, as a consequence, to enhance the therapeutics delivery into the brain. Some approaches for BBB crossing involve the modification of LP surfaces with biologically active ligands. Among them, the Apolipoprotein E-modified peptide (mApoE) has been used for several LP-based nanovectors under investigation. In this study, we propose Surface Plasmon Resonance imaging (SPRi) for the characterization of multifunctionalized LPs for Glioblastoma treatment. LPs were functionalized with mApoE and with a metallo-protease sensitive lipopeptide to deliver and guarantee the localized release of an encapsulated drug in diseased areas. The SPRi analysis was optimized in order to evaluate the binding affinity between LPs and mApoE receptors, finding that mApoE-LPs generated SPRi signals referred to interactions between mApoE and receptors mainly present in the brain. Moreover, a significant binding between LPs and VCAM-1 (endothelial receptor) was observed, whereas LPs did not interact significantly with peripheral receptors expressed on monocytes and lymphocytes. SPRi results confirmed not only the presence of mApoE on LP surfaces, but also its binding affinity, thanks to the specific interaction with selected receptors. In conclusion, the high sensitivity and the multiplexing capability associated with the low volumes of sample required and the minimal sample preparation, make SPRi an excellent technique for the characterization of multifunctionalized nanoparticles-based formulations.

Multiplexing Biosensor for the Detection of Extracellular Vesicles as Biomarkers of Tissue Damage and Recovery after Ischemic Stroke.

The inflammatory, reparative and regenerative mechanisms activated in ischemic stroke patients immediately after the event cooperate in the response to injury, in the restoration of functions and in brain remodeling even weeks after the event and can be sustained by the rehabilitation treatment. Nonetheless, patients' response to treatments is difficult to predict because of the lack of specific measurable markers of recovery, which could be complementary to clinical scales in the evaluation of patients. Considering that Extracellular Vesicles (EVs) are carriers of multiple molecules involved in the response to stroke injury, in the present study, we have identified a panel of EV-associated molecules that (i) confirm the crucial involvement of EVs in the processes that follow ischemic stroke, (ii) could possibly profile ischemic stroke patients at the beginning of the rehabilitation program, (iii) could be used in predicting patients' response to treatment. By means of a multiplexing Surface Plasmon Resonance imaging biosensor, subacute ischemic stroke patients were proven to have increased expression of vascular endothelial growth factor receptor 2 (VEGFR2) and translocator protein (TSPO) on the surface of small EVs in blood. Besides, microglia EVs and endothelial EVs were shown to be significantly involved in the intercellular communications that occur more than 10 days after ischemic stroke, thus being potential tools for the profiling of patients in the subacute phase after ischemic stroke and in the prediction of their recovery.

Recent Advances on Surface-Modified GBM Targeted Nanoparticles: Targeting Strategies and Surface Characterization.

Glioblastoma multiforme (GBM) is the most common malignant brain tumor, associated with low long-term survival. Nanoparticles (NPs) developed against GBM are a promising strategy to improve current therapies, by enhancing the brain delivery of active molecules and reducing off-target effects. In particular, NPs hold high potential for the targeted delivery of chemotherapeutics both across the blood-brain barrier (BBB) and specifically to GBM cell receptors, pathways, or the tumor microenvironment (TME). In this review, the most recent strategies to deliver drugs to GBM are explored. The main focus is on how surface functionalizations are essential for BBB crossing and for tumor specific targeting. We give a critical analysis of the various ligand-based approaches that have been used to target specific cancer cell receptors and the TME, or to interfere with the signaling pathways of GBM. Despite the increasing application of NPs in the clinical setting, new methods for ligand and surface characterization are needed to optimize the synthesis, as well as to predict their in vivo behavior. An expert opinion is given on the future of this research and what is still missing to create and characterize a functional NP system for improved GBM targeting.

Implementation of mRNA-Lipid Nanoparticle Technology in Atlantic Salmon (Salmo salar).

BACKGROUND: This study was conducted to investigate whether mRNA vaccine technology could be adapted for the ectothermic vertebrate Atlantic salmon (Salmo salar). Lipid nanoparticle (LNP) technology has been developed and optimized for mRNA vaccines in mammals, stabilizing mRNA and facilitating its delivery into cells. However, its utility at the temperatures and specific biological environments present in ectotherms remains unclear. In addition, it is unknown if modified mRNA containing non-canonical nucleotides can correctly translate in salmonid cells. METHODS: We used an mRNA transcript coding for enhanced green fluorescence protein, flanked by the untranslated regions of the hemagglutinin-esterase gene of the infectious salmon anemia virus, and a 120-base-long poly(A) tail. The mRNA was generated via in vitro transcription where uridine residues were replaced with N1-methyl-pseudouridines, and then encapsulated in LNPs. RESULTS: When transfected into the salmonid cell line CHH-1, the mRNA-LNP construct induced expression of EGFP. Furthermore, when mRNA-LNPs were injected intramuscularly into salmon, in vivo protein expression was demonstrated via immunohistochemistry. EGFP was observed in cells infiltrating the spaces between muscle cells in a focal inflammatory response. CONCLUSION: The results indicate that N1-methyl-pseudouridine-modified mRNA encapsulated in LNPs can be used to express antigens of interest in salmonid fish.

Freeze Drying of Polymer Nanoparticles and Liposomes Exploiting Different Saccharide-Based Approaches.

Biodegradable nanocarriers represent promising tools for controlled drug delivery. However, one major drawback related to their use is the long-term stability, which is largely influenced by the presence of water in the formulations, so to solve this problem, freeze-drying with cryoprotectants has been proposed. In the present study, the influence of the freeze-drying procedure on the storage stability of poly(lactide-co-glycolide) (PLGA) nanoparticles and liposomes was evaluated. In particular, conventional cryoprotectants were added to PLGA nanoparticle and liposome formulations in various conditions. Additionally, hyaluronic acid (HA), known for its ability to target the CD44 receptor, was assessed as a cryoprotective excipient: it was added to the nanocarriers as either a free molecule or conjugated to a phospholipid to increase the interaction with the polymer or lipid matrix while exposing HA on the nanocarrier surface. The formulations were resuspended and characterized for size, polydispersity index, zeta potential and morphology. It was demonstrated that only the highest percentages of cryoprotectants allowed the resuspension of stable nanocarriers. Moreover, unlike free HA, HA-phospholipid conjugates were able to maintain the particle mean size after the reconstitution of lyophilized nanoparticles and liposomes. This study paves the way for the use of HA-phospholipids to achieve, at the same time, nanocarrier cryoprotection and active targeting.

Post-COVID-19 Ongoing Symptoms and Health-Related Quality of Life: Does Rehabilitation Matter?: Preliminary Evidence.

OBJECTIVE: Individuals with persisting symptoms after coronavirus disease 2019 have reported a decrease in health-related quality of life. This study explores the outcome of 50 subjects with post-coronavirus disease 2019 ongoing symptoms including "long COVID"(symptoms lasting over 3 mos), after a rehabilitation program focused on three symptoms: fatigue, breathlessness, and pain. The aims were as follows: to assess the feasibility of the program, to observe a possible change in symptoms and quality of life (null hypothesis: no differences in variables before and after treatment), and to investigate a possible relationship between symptoms and quality of life. DESIGN: This is a retrospective observational study. RESULTS: Symptoms intensity measured with numeric rating scale decreased. Mean differences are as follows: breathlessness, -2.91; fatigue, -2.05; and pain, -2.41 ( P > 0.001). Quality of life measured with Euroqol-5D improved. Mean differences are as follows: Euroqol-5D index, 0.104, and Euroqol-5D visual analog scale, 19.21 ( P < 0.001). Effect size of these changings is classifiable as large (Cohen d > 0.8 and <1.3) except for Euroqol-5D index (Cohen d = -0.575), resulting medium (>0.5 and <0.8). Correlation (Pearson r ) between symptoms and Euroqol-5D resulted moderate for pain and fatigue (-0.609 and -0.531, P < 0.001) and low for breathlessness (-0.533, P < 0.001). CONCLUSIONS: Rehabilitation can be feasible and may improve symptoms and quality of life. Further research is needed.

Biochemical Characterization of Human Salivary Extracellular Vesicles as a Valuable Source of Biomarkers.

Extracellular vesicles (EVs) are natural nanoparticles secreted under physiological and pathological conditions. Thanks to their diagnostic potential, EVs are increasingly being studied as biomarkers of a variety of diseases, including neurological disorders. To date, most studies on EV biomarkers use blood as the source, despite different disadvantages that may cause an impure isolation of the EVs. In the present article, we propose the use of saliva as a valuable source of EVs that could be studied as biomarkers in an easily accessible biofluid. Using a comparable protocol for the isolation of EVs from both liquid biopsies, salivary EVs showed greater purity in terms of co-isolates (evaluated by nanoparticle tracking analysis and Conan test). In addition, Raman spectroscopy was used for the identification of the overall biochemical composition of EVs coming from the two different biofluids. Even considering the limited amount of EVs that can be isolated from saliva, the use of Raman spectroscopy was not hampered, and it was able to provide a comprehensive characterization of EVs in a high throughput and repeatable manner. Raman spectroscopy can thus represent a turning point in the application of salivary EVs in clinics, taking advantage of the simple method of collection of the liquid biopsy and of the quick, sensitive and label-free biophotonics-based approach.

Raman Spectroscopy Characterization of Multi-Functionalized Liposomes as Drug-Delivery Systems for Neurological Disorders.

The characterization of nanoparticle-based drug-delivery systems represents a crucial step in achieving a comprehensive overview of their physical, chemical, and biological features and evaluating their efficacy and safety in biological systems. We propose Raman Spectroscopy (RS) for the characterization of liposomes (LPs) to be tested for the control of neuroinflammation and microglial dysfunctions in Glioblastoma multiforme and Alzheimer's disease. Drug-loaded LPs were functionalized to cross the blood-brain barrier and to guarantee localized and controlled drug release. The Raman spectra of each LP component were used to evaluate their contribution in the LP Raman fingerprint. Raman data analysis made it possible to statistically discriminate LPs with different functionalization patterns, showing that each molecular component has an influence in the Raman spectrum of the final LP formulation. Moreover, CLS analysis on Raman data revealed a good level of synthetic reproducibility of the formulations and confirmed their stability within one month from their synthesis, demonstrating the ability of the technique to evaluate the efficacy of LP synthesis using small amount of sample. RS represents a valuable tool for a fast, sensitive and label free biochemical characterization of LPs that could be used for quality control of nanoparticle-based therapeutics.

Microglial-Targeted nSMase2 Inhibitor Fails to Reduce Tau Propagation in PS19 Mice.

The progression of Alzheimer's disease (AD) correlates with the propagation of hyperphosphorylated tau (pTau) from the entorhinal cortex to the hippocampus and neocortex. Neutral sphingomyelinase2 (nSMase2) is critical in the biosynthesis of extracellular vesicles (EVs), which play a role in pTau propagation. We recently conjugated DPTIP, a potent nSMase2 inhibitor, to hydroxyl-PAMAM-dendrimer nanoparticles that can improve brain delivery. We showed that dendrimer-conjugated DPTIP (D-DPTIP) robustly inhibited the spread of pTau in an AAV-pTau propagation model. To further evaluate its efficacy, we tested D-DPTIP in the PS19 transgenic mouse model. Unexpectantly, D-DPTIP showed no beneficial effect. To understand this discrepancy, we assessed D-DPTIP's brain localization. Using immunofluorescence and fluorescence-activated cell-sorting, D-DPTIP was found to be primarily internalized by microglia, where it selectively inhibited microglial nSMase2 activity with no effect on other cell types. Furthermore, D-DPTIP inhibited microglia-derived EV release into plasma without affecting other brain-derived EVs. We hypothesize that microglial targeting allowed D-DPTIP to inhibit tau propagation in the AAV-hTau model, where microglial EVs play a central role in propagation. However, in PS19 mice, where tau propagation is independent of microglial EVs, it had a limited effect. Our findings confirm microglial targeting with hydroxyl-PAMAM dendrimers and highlight the importance of understanding cell-specific mechanisms when designing targeted AD therapies.

Anatomo-functional organization of the ventral primary motor and premotor cortex in the macaque monkey.

The ventral agranular frontal cortex of the macaque monkey is formed by a mosaic of anatomically distinct areas. Although each area has been explored by several neurophysiological studies, most of them focused on small sectors of single areas, thus leaving to be clarified which is the general anatomo-functional organization of this wide region. To fill this gap, we studied the ventral convexity of the frontal cortex in two macaque monkeys (Macaca nemestrina) using intracortical microstimulation and extracellular recording. Functional data were then matched with the cytoarchitectonic parcellation of the recorded region. The results demonstrated the existence of a dorso-ventral functional border, encompassing the anatomical boundary between areas F4 and F1, and a rostro-caudal anatomo-functional border between areas F5 and F4. The ventral subdivision of areas F4 and F1 was highly electrically excitable, represented simple mouth movements and lacked visual properties; in contrast, their dorsal counterpart showed a higher stimulation threshold, represented forelimb and mouth motor acts and hosted different types of visual properties. The data also showed that area F5 was scarcely excitable, and displayed various motor specificity (e.g. for the type of grip) and complex visual (i.e. mirror responses) properties. Overall, the posterior areas F4 and F1 appear to be involved in organizing and controlling goal-directed mouth motor acts and simple movements within different parts of the external (dorsal sector) and internal (ventral sector) space, whereas area F5 code motor acts at a more abstract level, thus enabling the emergence of higher order socio-cognitive functions.

Advances in the Field of Micro- and Nanotechnologies Applied to Extracellular Vesicle Research: Take-Home Message from ISEV2021.

Extracellular Vesicles (EVs) are naturally secreted nanoparticles with a plethora of functions in the human body and remarkable potential as diagnostic and therapeutic tools. Starting from their discovery, EV nanoscale dimensions have hampered and slowed new discoveries in the field, sometimes generating confusion and controversies among experts. Microtechnological and especially nanotechnological advances have sped up biomedical research dealing with EVs, but efforts are needed to further clarify doubts and knowledge gaps. In the present review, we summarize some of the most interesting data presented in the Annual Meeting of the International Society for Extracellular Vesicles (ISEV), ISEV2021, to stimulate discussion and to share knowledge with experts from all fields of research. Indeed, EV research requires a multidisciplinary knowledge exchange and effort. EVs have demonstrated their importance and significant biological role; still, further technological achievements are crucial to avoid artifacts and misleading conclusions in order to enable outstanding discoveries.

Extracellular Vesicles in Regeneration and Rehabilitation Recovery after Stroke.

Patients that survive after a stroke event may present disabilities that can persist for a long time or permanently after it. If stroke prevention fails, the prompt and combinatorial intervention with pharmacological and rehabilitation therapy is pivotal for the optimal recovery of patients and the reduction of disabilities. In the present review, we summarize some key features of the complex events that occur in the brain during and after the stroke event, with a special focus on extracellular vesicles (EVs) and their role as both carriers of biomarkers and potential therapeutics. EVs have already demonstrated their ability to be used for diagnostic purposes for multiple brain disorders and could represent valuable tools to track the regenerative and inflammatory processes occurring in the injured brain after stroke. Last, but not least, the use of artificial or stem cell-derived EVs were proved to be effective in stimulating brain remodeling and ameliorating recovery after stroke. Still, effective biomarkers of recovery are needed to design robust trials for the validation of innovative therapeutic strategies, such as regenerative rehabilitation approaches.

Biophotonics for diagnostic detection of extracellular vesicles.

Extracellular Vesicles (EVs) are versatile carriers for biomarkers involved in the pathogenesis of multiple human disorders. Despite the increasing scientific and commercial interest in EV application in diagnostics, traditional biomolecular techniques usually require consistent sample amount, rely on operator-dependent and time- consuming procedures and cannot cope with the nano-size range of EVs, limiting both sensitivity and reproducibility of results. The application of biophotonics, i.e. light-based methods, for the diagnostic detection of EVs has brought to the development of innovative platforms with excellent sensitivity. In this review, we propose an overview of the most promising and emerging technologies used in the field of EV-related biomarker discovery. When tested on clinical samples, the reported biophotonic approaches in most cases have managed to discriminate between nanovesicles and contaminants, achieved much higher resolution compared to traditional procedures, and reached moderate to excellent diagnostic accuracy, thus demonstrating great potentialities for their clinical translation.

Characterization of the COPD Salivary Fingerprint through Surface Enhanced Raman Spectroscopy: A Pilot Study.

Chronic Obstructive Pulmonary Disease (COPD) is a debilitating pathology characterized by reduced lung function, breathlessness and rapid and unrelenting decrease in quality of life. The severity rate and the therapy selection are strictly dependent on various parameters verifiable after years of clinical observations, missing a direct biomarker associated with COPD. In this work, we report the methodological application of Surface Enhanced Raman Spectroscopy combined with Multivariate statistics for the analysis of saliva samples collected from 15 patients affected by COPD and 15 related healthy subjects in a pilot study. The comparative Raman analysis allowed to determine a specific signature of the pathological saliva, highlighting differences in determined biological species, already studied and characterized in COPD onset, compared to the Raman signature of healthy samples. The unsupervised principal component analysis and hierarchical clustering revealed a sharp data dispersion between the two experimental groups. Using the linear discriminant analysis, we created a classification model able to discriminate the collected signals with accuracies, specificities, and sensitivities of more than 98%. The results of this preliminary study are promising for further applications of Raman spectroscopy in the COPD clinical field.

Identification of the Raman Salivary Fingerprint of Parkinson's Disease Through the Spectroscopic- Computational Combinatory Approach.

Despite the wide range of proposed biomarkers for Parkinson's disease (PD), there are no specific molecules or signals able to early and uniquely identify the pathology onset, progression and stratification. Saliva is a complex biofluid, containing a wide range of biological molecules shared with blood and cerebrospinal fluid. By means of an optimized Raman spectroscopy procedure, the salivary Raman signature of PD can be characterized and used to create a classification model. Raman analysis was applied to collect the global signal from the saliva of 23 PD patients and related pathological and healthy controls. The acquired spectra were computed using machine and deep learning approaches. The Raman database was used to create a classification model able to discriminate each spectrum to the correct belonging group, with accuracy, specificity, and sensitivity of more than 97% for the single spectra attribution. Similarly, each patient was correctly assigned with discriminatory power of more than 90%. Moreover, the extracted data were significantly correlated with clinical data used nowadays for the PD diagnosis and monitoring. The preliminary data reported highlight the potentialities of the proposed methodology that, once validated in larger cohorts and with multi-centered studies, could represent an innovative minimally invasive and accurate procedure to determine the PD onset, progression and to monitor therapies and rehabilitation efficacy.

Appropriateness of admission to rehabilitation: definition of a set of criteria and rules through the application of the Delphi method.

BACKGROUND: Controlling inappropriateness of care is an essential issue, especially in rehabilitation medicine. In fact, admitting a patient to a rehabilitation hospital or unit is a complex decision also due to the absence of shared and objective admission criteria. AIM: The aim was to define clinical admission criteria and rules in rehabilitation medicine. DESIGN: Survey based on the application of the Delphi method on a sample of rehabilitation medicine experts. SETTING: Administration of electronic online questionnaires concerning appropriateness of admission to intensive rehabilitation. POPULATION: Volunteer sample of 53 experts with the following inclusion criteria: being members of the Italian Society of Physical and Rehabilitation Medicine, having practical experience in the research field, agreeing to the confidentiality of the information and being skilled in both rehabilitation and healthcare organization. METHODS: A three-round Delphi survey was conducted according to international guidelines. The two initial rounds consisted of an electronic online questionnaire while in the third one a report of the results was provided to the participants. The experts had to score their agreement with each item in the questionnaires, based on either a Likert scale or a dichotomous statement. Consensus between the experts was assessed. RESULTS: A total of 53 health professionals completed the Delphi survey. 19 out of 20 Italian regions were represented. The first round consisted of 8 multiple-choice questions. The second round was designed according to the suggestions provided by the panelists in the previous one and consisted of a twelve items questionnaire. At the end of the survey, seven criteria of appropriateness of admission to rehabilitation were identified and five rules defining an appropriate admission to a rehabilitation facility were elaborated. CONCLUSIONS: This study represents an attempt to create a worthwhile and reliable tool for a more conscious clinical practice in admission to rehabilitation, based on a set of shared criteria and rules. CLINICAL REHABILITATION IMPACT: To increase appropriateness of admission to rehabilitation. Improving appropriateness in healthcare delivery must be a primary goal in order to improve healthcare quality, save money and ensure system sustainability.

Learning new sport actions: Pilot study to investigate the imitative and the verbal instructive teaching methods in motor education.

The aim of the project was to investigate the effects of two strategies of teaching new sport actions on performance of eight-year-old children: observational-imitative method (OIM) and descriptive-directive method (DDM). The OIM group was provided with a pre-practice instruction in the form of expert modeling observation by an expert athlete. The DDM group received only verbal explanations of few selected static images. Thirty-six children (18 males and 18 females, mean age = 8,8) participated in the experiment. Subjects were randomly assigned to the OIM or DDM groups. Participants were instructed to perform four sport motor sequences never performed before (shoulder stand, soccer action, vortex howler throw, step action). Actions were videotaped and 2D kinematic analysis performed. A 10-point Likert questionnaire was administered to blind sport experts to assess the correctness and accuracy of each action. Results suggest that the OIM is the most effective instruction method when participants have no experience with the sport action to be performed. On the contrary, if the athlete needs to learn specific aspects of an exercise (such as grasping a tool) the best method is the DDM. In fact, detailed information on how to grab the vortex helped children in throwing it. We also found gender differences which might reflect cultural influences in specific sports (e.g. soccer). Finally, repetition of the exercise also improved the DDM group's performance. This has potential applications in sport teaching, suggesting that in the absence of a model performing the action to be imitated, the DDM can be as effective as the OIM if the observer repeats the sport action many times.

Rehabilitative treatment of patients with COVID-19 infection: the P.A.R.M.A. evidence based clinical practice protocol.

BACKGROUND: The impact of the SARS-CoV-2 on the National Health System (NHS) required a reorganization of the various levels of care, which also involved the rehabilitation reality. AIM OF THE WORK: A clinical practice review of the literature was conducted to provide operational-rehabilitation guidelines adapted to the local reality and to the recent corporate reorganization in the context of the COVID-19 emergency. METHODS: A practice review of the available scientific evidence was regularly conducted from the start of the COVID-19 pandemic to periodically update the clinical practice guidelines. Articles that met the following inclusion criteria were included: studies conducted on human adult subjects with COVID-19 infection, undergoing rehabilitation in any hospitalization setting. RESULTS: The results of this clinical practice update were periodically discussed with colleagues and collaborators in a multi-professional team, in order to guarantee a good clinical practice protocol, named P.A.R.M.A. CONCLUSIONS: The P.A.R.M.A. protocol is the result of a periodic review literature update, which has allowed us to take charge of patients affected by COVID-19 according to the most up-to-date clinical evidences, guaranteeing a shared and uniform treatment within a local reality in an era of health emergency.

Cortical and subcortical connections of parietal and premotor nodes of the monkey hand mirror neuron network.

Mirror neurons (MNs) are a class of cells originally discovered in the monkey ventral premotor cortex (PMv) and inferior parietal lobule (IPL). They discharge during both action execution and action observation and appear to play a crucial role in understanding others' actions. It has been proposed that the mirror mechanism is based on a match between the visual description of actions, encoded in temporal cortical regions, and their motor representation, provided by PMv and IPL. However, neurons responding to action observation have been recently found in other cortical regions, suggesting that the mirror mechanism relies on a wider network. Here we provide the first description of this network by injecting neural tracers into physiologically identified IPL and PMv sectors containing hand MNs. Our results show that these sectors are reciprocally connected, in line with the current view, but IPL MN sectors showed virtually no direct connection with temporal visual areas. In addition, we found that PMv and IPL MN sectors share connections with several cortical regions, including the dorsal and mesial premotor cortex, the primary motor cortex, the secondary somatosensory cortex, the mid-dorsal insula and the ventrolateral prefrontal cortex, as well as subcortical structures, such as motor and polysensory thalamic nuclei and the mid-dorsal claustrum. We propose that each of these regions constitutes a node of an "extended network", through which information relative to ongoing movements, social context, environmental contingencies, abstract rules, and internal states can influence MN activity and contribute to several socio-cognitive functions.

Action observation activates neurons of the monkey ventrolateral prefrontal cortex.

Prefrontal cortex is crucial for exploiting contextual information for the planning and guidance of behavioral responses. Among contextual cues, those provided by others' behavior are particularly important, in primates, for selecting appropriate reactions and suppressing the inappropriate ones. These latter functions deeply rely on the ability to understand others' actions. However, it is largely unknown whether prefrontal neurons are activated by action observation. To address this issue, we recorded the activity of ventrolateral prefrontal (VLPF) neurons of macaque monkeys during the observation of videos depicting biological movements performed by a monkey or a human agent, and object motion. Our results show that a population of VLPF neurons respond to the observation of biological movements, in particular those representing goal directed actions. Many of these neurons also show a preference for the agent performing the action. The neural response is present also when part of the observed movement is obscured, suggesting that these VLPF neurons code a high order representation of the observed action rather than a simple visual description of it.