1,721,377 research outputs found
Perturbing the Action Observation Network During Perception and Categorization of Actions' Goals and Grips: State-Dependency and Virtual Lesion TMS Effects
Full text linkWatching others grasping and using objects activates an action observation network (AON), including inferior frontal (IFC), anterior intraparietal (AIP), and somatosensory cortices (S1). Yet, causal evidence of the differential involvement of such AON sensorimotor nodes in representing high- and low-level action components (i.e., end-goals and grip type) is meager. To address this issue, we used transcranial magnetic stimulation-adaptation (TMS-A) during 2 novel action perception tasks. Participants were shown adapting movies displaying a demonstrator performing goal-directed actions with a tool, using either power or precision grips. They were then asked to match the end-goal (Goal-recognition task) or the grip (Grip-recognition task) of actions shown in test pictures to the adapting movies. TMS was administered over IFC, AIP, or S1 during presentation of test pictures. Virtual lesion-like effects were found in the Grip-recognition task where IFC stimulation induced a general performance decrease, suggesting a critical role of IFC in perceiving grips. In the Goal-recognition task, IFC and S1 stimulation differently affected the processing of "adapted" and "nonadapted" goals. These "state-dependent" effects suggest that the overall goal of seen actions is encoded into functionally distinct and spatially overlapping neural populations in IFC-S1 and such encoding is critical for recognizing and understanding end-goals
Empatia per il Dolore nella Corteccia Somatosensoriale: uno studio di Potenziali Evocati Somatosensoriali.
No full textAction-related dynamic changes in inferior frontal cortex effective connectivity: A TMS/EEG coregistration study
No full textHumans show exquisite abilities to perform versatile finger movements. The inferior frontal cortex (IFC) plays a pivotal role in the visual control of such movements through connections with other sensorimotor regions. Yet, the dynamics of IFC effective connectivity during action execution are still poorly understood. Using single-pulse TMS and simultaneous EEG recording (i.e., TMS-EEG coregistration), we stimulated the left posterior IFC at rest and during a visuomotor task. We recorded TMS-evoked potentials (TEPs) to assess action-related changes in IFC connectivity and localized their sources using sLORETA. We found two key time windows at ∼60 and ∼80 msec after IFC stimulation in which TEPs were modulated by task conditions in remote electrodes. In the first time window (∼60 msec), action-related changes in TEP amplitudes were observed over frontal and temporo-parietal electrodes, reflecting increased IFC connectivity with fronto-parietal motor areas and decreased IFC connectivity with visual occipito-temporal areas. In the second time window (∼80 msec), action-related TEP increases were observed in frontal, temporal and parietal regions partially overlapping with the default-mode network. No similar effects were observed when TMS was administered over a non-motor control area (the left posterior superior temporal sulcus, STS). These findings highlight dynamic changes in IFC connectivity with motor, sensory and default-mode networks. They suggest sequential stages of task-related changes in IFC connectivity possibly related to controlling and sensing actions and inhibiting default-mode brain activity during motor performance
Early changes in corticospinal excitability when seeing fearful body expressions
Full text linkQuick inhibition of approach tendencies in response to signals of potential threats is thought to promote survival. However, little is known about the effect of viewing fearful expressions on the early dynamics of the human motor system. We used the high temporal resolution of single-pulse and paired-pulse transcranial magnetic stimulation (TMS) over the motor cortex to assess corticospinal excitability (CSE) and intracortical facilitation (ICF) during observation of happy, fearful and neutral body postures. To test motor circuits involved in approach tendencies, CSE and ICF were recorded from the first dorsal interosseous (FDI), a muscle involved in grasping, and the abductor pollicis brevis (APB), which served as a control. To test early motor dynamics, CSE and ICF were measured 70-90 ms after stimulus onset. We found a selective reduction in CSE in the FDI when participants observed fearful body expressions. No changes in ICF or in the excitability of APB were detected. Our study establishes an extremely rapid motor system reaction to observed fearful body expressions. This motor modulation involves corticospinal downstream projections but not cortical excitatory mechanisms, and appears to reflect an inhibition of hand grasping. Our results suggest a fast visuo-motor route that may rapidly inhibit inappropriate approaching actions
Enhanced action performance following TMS manipulation of associative plasticity in ventral premotor-motor pathway
No full textSkillful goal-directed manual actions such as grasping and manipulating objects are supported by a large sensorimotor network. Within this network, the ventral premotor cortex (PMv) transforms visual information about objects into motor commands that are conveyed to the primary motor cortex (M1), allowing fine control of finger movements. However, it is unknown whether transcranial magnetic stimulation (TMS) of this PMv-to-M1 hierarchical pathway improves action performance. To fill in this gap, here, we used cortico-cortical paired associative stimulation (ccPAS) with the aim of manipulating synaptic efficacy in the human PMv-to-M1 pathway. We found that repeatedly pairing TMS of pre-and post-synaptic nodes of the PMv-to-M1 pathway (i.e., PMv-to-M1 ccPAS) increased motor excitability and enhanced performance on the 9-Hole Peg Test (9-HPT), which taps into PMv-M1 functioning. These effects were specific to the ccPAS protocol consistent with the direction of the PMv-to-M1 hierarchy, as no effects were observed when reversing the order of the paired TMS pulses (i.e., following a M1-to-PMv ccPAS) or when administering sham ccPAS. Additionally, the effect of PMv-to-M1 ccPAS appeared functionally specific, as no behavioral enhancement was observed in a visuomotor control task. We therefore provide novel causal evidence that the PMv-to-M1 pathway, which is instrumental to object-oriented hand actions, is sensitive to TMS manipulations of associative plasticity. Our study highlights the causal role of the PMv-to-M1 pathway in controlling skillful object-oriented hand actions and suggests that ccPAS might be a useful tool for investigating the functional relevance of directional connectivity in humans. These findings may have implications for designing novel therapeutic strategies based on the manipulation of associative plasticity in cortico-cortical networks
Stimulus-driven modulation of motor- evoked potentials during observation of others’ pain.
No full text"Action simulation plays a critical role in deceptive action recognition" Poster Presentation - 8th IBRO Conference, Florence-Italy, July 14-18, 2011.
No full textCortisol Imbalance and Fear Learning in PTSD: Therapeutic Approaches to Control Abnormal Fear Responses
No full textPost-Traumatic Stress Disorder (PTSD) is mainly characterized by dysregulated fear responses, including hyperarousal and intrusive re-experiencing of traumatic memories. This work delves into the intricate interplay between abnormal fear responses, cortisol dysregulation, and the Hypothalamic-Pituitary-Adrenal (HPA) axis, elucidating their role in the manifestation of PTSD. Given the persistent nature of PTSD symptoms and the limitations of conventional therapies, innovative interventions are urgently needed. One promising avenue of research revolves around the modulation of cortisol through targeting receptors, with dexamethasone emerging as a critical agent capable of reducing cortisol levels, thus potentially aiding in the extinction of fear. In this study, we emphasize the need for innovative interventions in the neuropharmacological treatment of PTSD, focusing on cortisol modulation and its impact on fear regulation mechanisms. The complex interplay between the HPA axis, cortisol modulation, and fear dysregulation not only broadens our comprehension but also reveals promising paths to enhance therapeutic outcomes for individuals struggling with PTSD, underscoring a crucial need for more effective treatment strategies
Enhancing Motor Brain Activity Improves Memory for Action Language: A tDCS Study
No full textThe embodied cognition approach to linguistic meaning posits that action language understanding is grounded in sensory-motor systems. However, evidence that the human motor cortex is necessary for action language memory is meager. To address this issue, in two groups of healthy individuals, we perturbed the left primary motor cortex (M1) by means of either anodal or cathodal transcranial direct current stimulation (tDCS), before participants had to memorize lists of manual action and attentional sentences. In each group, participants received sham and active tDCS in two separate sessions. Following anodal tDCS (a-tDCS), participants improved the recall of action sentences compared with sham tDCS. No similar effects were detected following cathodal tDCS (c-tDCS). Both a-tDCS and c-tDCS induced variable changes in motor excitability, as measured by motor-evoked potentials induced by transcranial magnetic stimulation. Remarkably, across groups, action-specific memory improvements were positively predicted by changes in motor excitability. We provide evidence that excitatory modulation of the motor cortex selectively improves performance in a task requiring comprehension and memory of action sentences. These findings indicate that M1 is necessary for accurate processing of linguistic meanings and thus provide causal evidence that high-order cognitive functions are grounded in the human motor system
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