Biomedical subjects

Laila Craighero

Publications and source records attributed to Laila Craighero.

9 recordsLinked to original sources

PubMed2006

Hand actions and speech representation in Broca's area.

This paper presents data and theoretical framework supporting a new interpretation of the role played by Broca's area. Recent brain imaging studies report that, in addition to speech-related activation, Broca's area is also significantly involved during tasks devoid of verbal content. In consideration of the large variety of experimental paradigms inducing Broca's activation, here we present some neurophysiological data from the monkey homologue of Brodmann's areas (BA) 44 and 45 aiming to integrate on a common ground these apparently different functions. Finally, we will report electrophysiological data on humans which connect speech perception to the more general framework of other's action understanding.

Animals↗

PubMed2005

Human motor cortex excitability during the perception of others' action.

Neuroscience research during the past ten years has fundamentally changed the traditional view of the motor system. In monkeys, the finding that premotor neurons also discharge during visual stimulation (visuomotor neurons) raises new hypotheses about the putative role played by motor representations in perceptual functions. Among visuomotor neurons, mirror neurons might be involved in understanding the actions of others and might, therefore, be crucial in interindividual communication. Functional brain imaging studies enabled us to localize the human mirror system, but the demonstration that the motor cortex dynamically replicates the observed actions, as if they were executed by the observer, can only be given by fast and focal measurements of cortical activity. Transcranial magnetic stimulation enables us to instantaneously estimate corticospinal excitability, and has been used to study the human mirror system at work during the perception of actions performed by other individuals. In the past ten years several TMS experiments have been performed investigating the involvement of motor system during others' action observation. Results suggest that when we observe another individual acting we strongly 'resonate' with his or her action. In other words, our motor system simulates underthreshold the observed action in a strictly congruent fashion. The involved muscles are the same as those used in the observed action and their activation is temporally strictly coupled with the dynamics of the observed action.

Electromagnetic Fields↗

PubMed2004

Corticospinal excitability during painful self-stimulation in humans: a transcranial magnetic stimulation study.

We investigated changes in the corticospinal pattern of activity in healthy volunteers during sustained noxious and non-noxious mechanical stimulation of the first hand digit, resulting from active (self-stimulation) or passive (externally-induced) pressing against a sharp or blunted tip. The results indicate that, in order to press a finger onto a noxious stimulus with the same force generated to press onto a non-noxious one, the motor cortex adopts a peculiar strategy in terms of recruitment of motor units. This is reflected by an increase of corticospinal excitability (as revealed by motor potentials evoked by transcranial magnetic stimulation of the contralateral primary motor cortex) and EMG activity of agonist muscles, possibly related to an increase of motor unit synchronization.

Adult↗

PubMed2004

Eye position affects orienting of visuospatial attention.

The ability to detect an incoming visual stimulus is enhanced by knowledge of stimulus location (orienting of visuospatial attention). Although the brain mechanisms at the basis of this enhancement are not yet fully clarified, there is evidence that orienting of attention is accompanied by the activation of oculomotor circuits. It remains unclear, however, whether this oculomotor activity is an epiphenomenon or is functionally related to the attentional process. Attentional benefits are usually measured by the classical Posner paradigm. When subjects fixate centrally and are requested to detect a visual stimulus that could appear in an attended or unattended location, they react faster to stimuli appearing in the attended one. Here, we demonstrate that in monocular vision visuospatial attention was significantly modulated by the position of the eye in the orbit. When the screen was placed 40 degrees to the right or to the left of subjects' sagittal plane, attentional benefits for stimuli appearing in subjects' temporal spatial hemifield dramatically decayed, even if the retinal stimulation was exactly the same as in the classical paradigm. The finding that eyes and attention show a common limit stop point supports their close functional coupling.

Attention↗

PubMed2004

The mirror-neuron system.

A category of stimuli of great importance for primates, humans in particular, is that formed by actions done by other individuals. If we want to survive, we must understand the actions of others. Furthermore, without action understanding, social organization is impossible. In the case of humans, there is another faculty that depends on the observation of others' actions: imitation learning. Unlike most species, we are able to learn by imitation, and this faculty is at the basis of human culture. In this review we present data on a neurophysiological mechanism--the mirror-neuron mechanism--that appears to play a fundamental role in both action understanding and imitation. We describe first the functional properties of mirror neurons in monkeys. We review next the characteristics of the mirror-neuron system in humans. We stress, in particular, those properties specific to the human mirror-neuron system that might explain the human capacity to learn by imitation. We conclude by discussing the relationship between the mirror-neuron system and language.

Animals↗

PubMed2003

New insights on sensorimotor integration: from hand action to speech perception.

In the last two decades the integrative role of the frontal premotor cortex (a mosaic of agranular/disgranular areas lying in front of the primary motor cortex) have been more and more elucidated. Among its various functions, sensorimotor transformation, and action representation storage, also for nonstrictly motor purposes, are the most intriguing properties of this region, as shown by several researches. In this article we will mainly focus on the ventro-rostral part of the monkey premotor cortex (area F5) in which visual information describing objects and others' acting hands are associated with goal-directed motor representations of hand movements. We will describe the main characteristics of F5 premotor neurons and we will provide evidence in favor of a parallelism between monkeys and humans on the basis of new experimental observations. Finally, we will present some data indicating that, both in humans and in monkeys, action-related sensorimotor transformations are not restricted to visual information but concern also acoustic information.

Functional Laterality↗

PubMed2002

Hand action preparation influences the responses to hand pictures.

The relations between stimuli triggering a hand grasping movement and the subsequent action were studied in normal human participants. Participants were instructed to prepare to grasp a bar, oriented either clockwise or counterclockwise, and to grasp it as fast as possible on presentation of a visual stimulus with their right hand. The visual stimuli were pictures of the right hand as seen in a mirror. In Experiment 1, they represented the mirror image of the hand final posture as achieved in grasping the bar oriented either clockwise or counterclockwise. In Experiment 2, in addition to the pictures of Experiment 1, another two pictures, obtained rotating the hands represented in the previous ones of 90 degrees, were also used. Both experiments showed that the reaction times were faster when there was a similarity between hand position as depicted in the triggering visual stimulus and the grasping hand final position, the fastest responses being those where this similarity was the closest. In addition, Experiment 2 showed that reaction times to not rotated stimuli were faster than reaction times to the rotated stimuli, thus excluding a simple stimulus-response compatibility explanation of the findings. The data are interpreted as behavioral evidence that there is a close link between specific visual stimuli and specific motor actions. A neurophysiological model for this visuo-motor link is presented.

Adult↗

PubMed2002

Speech listening specifically modulates the excitability of tongue muscles: a TMS study.

The precise neural mechanisms underlying speech perception are still to a large extent unknown. The most accepted view is that speech perception depends on auditory-cognitive mechanisms specifically devoted to the analysis of speech sounds. An alternative view is that, crucial for speech perception, it is the activation of the articulatory (motor) gestures that generate these sounds. The listener understands the speaker when his/her articulatory gestures are activated (motor theory of speech perception). Here, by using transcranial magnetic stimulation (TMS), we demonstrate that, during speech listening, there is an increase of motor-evoked potentials recorded from the listeners' tongue muscles when the presented words strongly involve, when pronounced, tongue movements. Although these data do not prove the motor theory of speech perception, they demonstrate for the first time that word listening produces a phoneme specific activation of speech motor centres.

Acoustic Stimulation↗

PubMedDate not supplied

Electrophysiology of action representation.

We continuously act on objects, on other individuals, and on ourselves, and actions represent the only way we have to manifest our own desires and goals. In the last two decades, electrophysiological experiments have demonstrated that actions are stored in the brain according to a goal-related organization. The authors review a series of experimental data showing that this "vocabulary of motor schemata" could also be used for non-strictly motor purposes. In the first section, they present data from monkey experiments describing the functional properties of inferior premotor cortex and, in more detail, the properties of visuomotor neurons responding to objects and others' actions observation (mirror neurons). In the second section, human data are reviewed, with particular regard to electrophysiological experiments aiming to investigate how action representations are stored and addressed. The specific facilitatory effect of motor imagery, action/object observation, and speech listening on motor excitability shown by these experiments provides strong evidence that the motor system is constantly involved whenever the idea of an action is evoked.

Animals↗