187,970 research outputs found
Cornelius P. Haggard - Portrait
No full textHaggard, Cornelius P.; Training School for Christian Workers President; Pacific Bible College President; Azusa College President; Azusa Pacific College Presidenthttps://digitalarchives.apu.edu/presidential-portrait/1032/thumbnail.jp
Don't do it! Cortical inhibition and self-attribution during action observation
No full textNumerous studies suggest that both self-generated and observed actions of others activate overlapping neural networks, implying a shared, agent-neutral representation of self and other. Contrary to the shared representation hypothesis, we recently showed that the human motor system is not neutral with respect to the agent of an observed action [Schütz-Bosbach, S., Mancini, B., Aglioti, S. M., & Haggard, P. Self and other in the human motor system. Current Biology, 16, 1830–1834, 2006]. Observation of actions attributed to another agent facilitated the motor system, whereas observation of identical actions linked to the self did not. Here we investigate whether the absence of motor facilitation for observing one’s own actions reflects a specific process of cortical inhibition associated with self-representation. We analyzed the duration of the silent period induced by transcranial magnetic stimulation of the motor cortex in active muscles as an indicator of motor inhibition. We manipulated whether an observed action was attributed to another agent, or to the subjects themselves, using a manipulation of body ownership on the basis of the rubber hand illusion. Observation of actions linked to the self led to longer silent periods than observation of a static hand, but the opposite effect occurred when observing identical actions attributed to another agent. This finding suggests a specific inhibition of the motor system associated with self-representation. Cortical suppression for actions linked to the self might prevent inappropriate perseveration within the motor system
From Freedom From to Freedom To: New Perspectives on Intentional Action
No full textThere are few concepts as relevant as that of intentional action in shaping our sense of self and the interaction with the environment. At the same time, few concepts are so elusive. Indeed, both conceptual and neuroscientific accounts of intentional agency have proven to be problematic. On the one hand, most conceptual views struggle in defining how agents can adequately exert control over their actions. On the other hand, neuroscience settles for definitions by exclusion whereby key features of human intentional actions, including goal-directness, remain underspecified. This paper reviews the existing literature and sketches how this gap might be filled. In particular, we defend a gradualist notion of intentional behavior, which revolves around the following key features: autonomy, flexibility in the integration of causal vectors, and control
Visually induced analgesia: seeing the body reduces pain
No full textGiven previous reports of strong interactions between vision and somatic senses, we investigated whether vision of the body modulates pain perception. Participants looked into a mirror aligned with their body midline at either the reflection of their own left hand (creating the illusion that they were looking directly at their own right hand) or the reflection of a neutral object. We induced pain using an infrared laser and recorded nociceptive laser-evoked potentials (LEPs). We also collected subjective ratings of pain intensity and unpleasantness. Vision of the body produced clear analgesic effects on both subjective ratings of pain and the N2/P2 complex of LEPs. Similar results were found during direct vision of the hand, without the mirror. Furthermore, these effects were specific to vision of one’s own hand and were absent when viewing another person’s hand. These results demonstrate a novel analgesic effect of non-informative vision of the body
Viewing the body prepares the brain for touch: effects of TMS over somatosensory cortex
No full textViewing the body can improve tactile perception. We investigated whether this could be due to a remodeling of somatosensory cortical areas during vision of the body. Single-pulse transcranial magnetic stimulation (TMS) was delivered over the primary and secondary somatosensory areas of subjects who showed clear visual-tactile enhancement while they performed a tactile grating discrimination task. Before the tactile stimulus, subjects viewed either their right index finger through a semisilvered mirror or an object reflected by the mirror and positioned to appear in the same location as the finger. In a first experiment we observed that TMS over primary somatosensory cortex significantly reduced subjects' accuracy whilst viewing the hand. No such reduction was found when subjects viewed a neutral object. In a second experiment, we disrupted the activity of primary and secondary somatosensory areas in different sessions. When stimulating the primary somatosensory cortex, a reduction in accuracy was again found while viewing the hand, but not a neutral object. TMS over secondary somatosensory cortex had no effect in any condition. Our results show that vision of the body may act at an early stage in stimulus elaboration and perception, allowing an anticipatory tuning of the neural circuits in primary somatosensory cortex that underlie tactile acuity
Transforming the Thermal Grill Effect by Crossing the Fingers
No full textSummaryThe relation between pain perception and spatial representation of the body is poorly understood. In the thermal grill illusion (TGI), alternating non-noxious warm and cold temperatures cause a paradoxical, sometimes painful, sensation of burning heat [1]. We combined thermal grill stimulation with crossing the fingers to investigate whether nociceptively mediated sensation depends on the somatotopic or spatiotopic configuration of thermal inputs. We stimulated the index, middle, and ring fingers when the middle finger either was or was not crossed over the index to generate “warm-cold-warm” patterns in either somatotopic or spatiotopic coordinates. Participants adjusted a temperature delivered to the other hand until it matched their perception of the cold target finger (index or middle). We found significant temperature overestimation when the target was central within the spatial configuration (warm-cold-warm) compared to when it was peripheral (cold-warm-warm). Crucially, this effect depended on the spatiotopic configuration of thermal inputs, but it was independent of the finger posture and present for both index and middle target fingers—the thermal grill effect for the middle finger was abolished when it was crossed over the index to adopt a spatiotopically peripheral position, while the same effect was newly generated for the index finger by the same postural change. Our results suggest that the locations of multiple stimuli are remapped into external space as a group; nociceptively mediated sensations depended not on the body posture, but rather on the external spatial configuration formed by the pattern of thermal stimuli in each posture
Don't do it! Cortical inhibition and self-attribution during action observation
No full textNumerous studies suggest that both self-generated and observed actions of others activate overlapping neural networks, implying a shared, agent-neutral representation of self and other. Contrary to the shared representation hypothesis, we recently showed that the human motor system is not neutral with respect to the agent of an observed action [Schütz-Bosbach, S., Mancini, B., Aglioti, S. M., & Haggard, P. Self and other in the human motor system. Current Biology, 16, 1830-1834, 2006]. Observation of actions attributed to another agent facilitated the motor system, whereas observation of identical actions linked to the self did not. Here we investigate whether the absence of motor facilitation for observing one's own actions reflects a specific process of cortical inhibition associated with self-representation. We analyzed the duration of the silent period induced by transcranial magnetic stimulation of the motor cortex in active muscles as an indicator of motor inhibition. We manipulated whether an observed action was attributed to another agent, or to the subjects themselves, using a manipulation of body ownership on the basis of the rubber hand illusion. Observation of actions linked to the self led to longer silent periods than observation of a static hand, but the opposite effect occurred when observing identical actions attributed to another agent. This finding suggests a specific inhibition of the motor system associated with self-representation. Cortical suppression for actions linked to the self might prevent inappropriate perseveration within the motor system. © 2008 Massachusetts Institute of Technology
IMITATION WITHOUT AWARENESS
No full textmitation is a characteristic but little-understood function of the human brain and of some higher animals. The direct matching hypothesis suggests that a specialised brain circuit is able to extract and directly copy the motor commands of another person's observed actions. Here we investigate how conscious people are of this kind of imitation. We first showed that imitation reactions are faster than simple visual reaction times, consistent with a direct matching circuit in the CNS. We next compared the perceived time of imitation reactions in 17 healthy subjects with other kinds of actions. We found a significant delay in subjects' awareness of their own imitation reactions. Thus, while imitation reactions are unusually fast, subjects are not aware of this. The brain's direct-matching circuit for imitation partly bypasses conscious awareness
An object-centred reference frame for control of grasping:effects of grasping a distractor object on visuomotor control
No full textPrevious evidence based on perceptual integration and arbitrary responses suggests extensive cross-modal links in attention across the various modalities. Attention typically shifts to a common location across the modalities, despite the vast differences in their initial coding of space. An issue that remains unclear is whether or not these effects of multisensory coding occur during more natural tasks, such as grasping and manipulating three-dimensional objects. Using kinematic measures, we found strong effects of the diameter of a grasped distractor object on the aperture used to grasp a target object at both coincident and non-coincident locations. These results suggest that interference effects can occur between proprioceptive and visuomotor signals in grasping. Unlike other interference effects in cross-modal attention, these effects do not depend on the spatial relation between target and distractor, but occur within an object-based frame of reference
- …
