We review evidence for partially segregated networks of brain areas that carry out different attentional functions. One system, which includes parts of the intraparietal cortex and superior frontal cortex, is involved in preparing and applying goal-directed (top-down) selection for stimuli and responses. This system is also modulated by the detection of stimuli. The other system, which includes the temporoparietal cortex and inferior frontal cortex, and is largely lateralized to the right hemisphere, is not involved in top-down selection. Instead, this system is specialized for the detection of behaviourally relevant stimuli, particularly when they are salient or unexpected. This ventral frontoparietal network works as a 'circuit breaker' for the dorsal system, directing attention to salient events. Both attentional systems interact during normal vision, and both are disrupted in unilateral spatial neglect.

Control of goal-directed and stimulus-driven attention in the brain

Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

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.

The mirror-neuron system.

The anterior insular cortex (AIC) is implicated in a wide range of conditions and behaviours, from bowel distension and orgasm, to cigarette craving and maternal love, to decision making and sudden insight. Its function in the re-representation of interoception offers one possible basis for its involvement in all subjective feelings. New findings suggest a fundamental role for the AIC (and the von Economo neurons it contains) in awareness, and thus it needs to be considered as a potential neural correlate of consciousness.

How do you feel--now? The anterior insula and human awareness.

Prior to the twentieth century, theories of knowledge were inherently perceptual. Since then, developments in logic, statis- tics, and programming languages have inspired amodal theories that rest on principles fundamentally different from those underlying perception. In addition, perceptual approaches have become widely viewed as untenable because they are assumed to implement record- ing systems, not conceptual systems. A perceptual theory of knowledge is developed here in the context of current cognitive science and neuroscience. During perceptual experience, association areas in the brain capture bottom-up patterns of activation in sensory-motor areas. Later, in a top-down manner, association areas partially reactivate sensory-motor areas to implement perceptual symbols. The stor- age and reactivation of perceptual symbols operates at the level of perceptual components - not at the level of holistic perceptual expe- riences. Through the use of selective attention, schematic representations of perceptual components are extracted from experience and stored in memory (e.g., individual memories of green, purr, hot). As memories of the same component become organized around a com- mon frame, they implement a simulator that produces limitless simulations of the component (e.g., simulations of purr). Not only do such simulators develop for aspects of sensory experience, they also develop for aspects of proprioception (e.g., lift, run) and introspec- tion (e.g., compare, memory, happy, hungry). Once established, these simulators implement a basic conceptual system that represents types, supports categorization, and produces categorical inferences. These simulators further support productivity, propositions, and ab- stract concepts, thereby implementing a fully functional conceptual system. Productivity results from integrating simulators combinato- rially and recursively to produce complex simulations. Propositions result from binding simulators to perceived individuals to represent type-token relations. Abstract concepts are grounded in complex simulations of combined physical and introspective events. Thus, a per- ceptual theory of knowledge can implement a fully functional conceptual system while avoiding problems associated with amodal sym- bol systems. Implications for cognition, neuroscience, evolution, development, and artificial intelligence are explored.

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Perceptual symbol systems.

Imagery and its neurological substrate

Motion detection and optokinetic responses in dark-reared kittens

Publisher Summary This chapter discusses the generation and control of goal-directed arm and hand movements during the action of prehension. This is a fundamental aspect of visuomotor behavior and combines two different types of motor behavior. Reaching as a behavior for interacting with the environment, is mostly effected by the proximal joints of the arm and deals with spatial relations of the objects and the body. Its function is to carry the hand to an appropriate location within extrapersonal space and as such must involve mechanisms for computing distance and direction of the point in space where to move. Grasping is a highly refined skill due to the specialization of the hand in primates and humans, it is effected by the distal joints of the fingers, and deals with intrinsic qualities of objects. The coordinate system in which grasping movements are generated therefore does not relate to the body, it relates to the object and the hand.

Chapter 9 Functional Characteristics of Prehension: From Data to Artificial Neural Networks

Compensation of the effects of hemilabyrinthectomy is a good model for the study of central rearrangements which occur after a lesion. Firstly, the pattern of the labyrinthine connections to the vestibular nuclei and of the commissural connections between the two groups of nuclei begins to be extensively known. Secondly, the state of the vestibular system can be easily tested through its well identified responses for the control of gaze and posture Finally, the existence of many extralabyrinthine afferents to this system raises the possibility of an extrinsic control of its activity.

Supravestibular Control of Vestibular Compensation After Hemilabyrinthectomy in the Cat

Analogical transfer in problem solving is a fundamental aspect of human intelligence that involves exploiting knowledge about the solution for one problem to solve an0ther.l In order to provide a quantifiable measure of analogical transfer in sequence learning (ATSL), we developed a novel extension of the serial reaction time (SRT) paradigm. To quantify the underlying representational and computational requirements for ATSL we extended a neurobiologically based model of primate prefrontal cortex (PFC) and basal ganglia function in visuomotor sequence learning* to address analogical transfer. We compared the behavior of this model with preliminary data from normal subjects and patients with frontostriatal dysfunction [idiopathic dopa-sensitive Parkinson’s disease (PD)] in the ATSL paradigm.

Marc Jeannerod

Papers

Imagery and its neurological substrate

Motion detection and optokinetic responses in dark-reared kittens

Chapter 9 Functional Characteristics of Prehension: From Data to Artificial Neural Networks

Supravestibular Control of Vestibular Compensation After Hemilabyrinthectomy in the Cat

Analogical Transfer in Sequence Learning.