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From spatial attention to attention to objects: An extension of the premotor theory of attention
No full textThis article is subdivided into two parts. In the first part, we review recent data showing that in the cerebral cortex there are multiple parallel space coding circuits, each of them related to the organization of a particular action. We argue that this architecture fit well modular theories of attention, and in particular that known as the premotor theory of attention, whereas it is hardly compatible with the view that spatial attention is a unitary system. In the second part, we present experiments showing that preparation to act toward an object (e.g., grasping an object) determines automatically a facilitation to detect and discriminate visual shapes congruent with the object acted upon. This top-down facilitation is due to an activation of post-central areas involved in the visual analysis of the stimulus and it is observed also when effecters, other than that prepared for responding, are used. These new findings confirm and greatly enlarge the explanatory value of the premotor t..
Premotor theory of attention
No full textSpatial attention is the capacity to improve the processing of sensory information coming from a specific part of the space surrounding the observer. Classically, spatial attention was thought of as a dedicated supramodal control mechanism, anatomically distinct from the circuits underlying sensorimotor processing (see Posner and Dehaene, 1994). In the late eighties Rizzolatti et al. (1987) challenged this view. On the basis of some behavioral experiments (see below) they argued that there is no need to postulate two control mechanisms, one for action and one for attention. According to them spatial attention does not result from a dedicated control mechanism, but derives from a weaker activation of the same frontal-parietal circuits that, in other conditions, determine motor behavior toward specific spatial locations. This theory, known as the “premotor theory of attention”, has received in these last years a tremendous support from electrophysiological and brain imaging studies and has been extended from spatial attention to attention directed to objects (Rizzolatti and Craighero, 1998)
Do Perception and Action Result from Different Brain Circuits? The Three Visual Systems Hypothesis
No full textThis chapter argues that the separation of the cortical visual processing into two streams is insufficient and, in the version where perception and action are kept separated, leads to a misunderstanding of the true nature of perceptual processes. It shows that the processing carried out in the inferior parietal lobule is different from that performed in the inferior parietal lobe, and that the so-called dorsal stream is in fact formed by two streams: the dorsodorsal stream (D-D) and the ventrodorsal stream (V-D). The chapter also discusses the relation between action and perception as it emerges from neurophysiological data on the V-D stream. It proposes that both action perception and space perception derive from a preceding motor knowledge based on self-generated actions
Binocularly driven neurons in visual cortex of split-chiasm cats
No full textIn cats with midsagittal section of the optic chiasm, some visual cortex neurons can be driven not only by the ipsilateral eye, through the direct geniculocortical pathways, but also by the contralateral eye, through the opposite visual cortex and corpus callosum. The receptive fields and the response characteristics observed upon stimulation of the contralateral eye are very similar to those observed upon stimulation of the ipsilateral eye; the two monocular receptive fields of a given cell lie in corresponding points of heteronymous halves of the visual field in close contact with the vertical meridian, thus adding in visual space and forming a binocular receptive area which crosses the vertical meridian and extends equally on either side of it
Effect of the probability of the appearance of stimulus on voluntary movements of attention
Full text linkThe use of action observation treatment to restore motor functions in patients with neurological disorders
No full textGrasping objects and grasping action meanings: the dual role of monkey rostroventral premotor cortex (area F5)
No full textMonkey area F5 consists of two main histochemical sectors, one buried inside the arcuate sulcus, the other located on the cortical convexity. Neurons of both sectors discharge during hand movements. Many of them also fire in response to the presentation of visual stimuli. However, the visual stimuli effective for triggering the neurons in each sector are markedly different. Neurons located in the bank of the arcuate sulcus respond to the observation of 3D objects, provided that object size and shape is congruent with the prehension type coded by the neuron ('canonical' F5 neurons). Neurons of the convexity discharge when the monkey observes band actions performed by another individual, provided that they are similar to the motor action coded by the neuron ('mirror' neurons). What do the canonical F5 neurons and the surprising mirror neurons have in common? The interpretation we propose is that these two categories of F5 neurons both generate an internal copy of a potential hand action...
Evolution of Mirror Neuron Mechanism in Primates
No full textThe mirror mechanism is a basic mechanism that transforms sensory representations of the observed or listened actions into motor representations of the same actions. In the present chapter we review evidence for the role of the mirror mechanism in emotion and in goal-directed actions in nonhuman primates and humans. We examine the functions, such as imitation and language, which are present exclusively or almost exclusively in humans and discuss the role of the mirror mechanism in these functions
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