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The brain receives information about the environment from all the sensory modalities, including vision, touch, and audition. To interact efficiently with the environment, this information must eventually converge to form a reliable and accurate multimodal percept. This process is often complicated by the existence of noise at every level of signal processing, which makes the sensory information derived from the world unreliable and inaccurate. There are several ways in which the nervous system may minimize the negative consequences of noise in terms of reliability and accuracy. Two key strategies are to combine redundant sensory estimates and to use prior knowledge. This chapter elaborates further on how these strategies may be used by the nervous system to obtain the best possible estimates from noisy signals.

This chapter argues that cortical networks and the knowledge they represent are hierarchically organized in layers by order of complexity or generality of cognitive content. These layers correspond to cortical stages for the processing and representation of sensory information. Further, the perceptual networks are amply interconnected within and between layers, as well as with the motor networks or cognits of frontal regions. The chapter assembles evidence of an order in the cortical processing of sensory information that corresponds isomorphically to the mental or phenomenal order of perception. The first two sections of the chapter deal with psychological aspects of perception; the last three deal with the mechanisms by which networks of posterior and frontal cortex process sensory information in perception. The limited capacity of sensory systems to process sensory information is the primary reason why selective attention serves the categorizing in one particular sector of perception at the expense of all others. There are two major components of selective attention: inclusion and exclusion. This chapter also discusses gestalt psychology, perceptual binding, and perception-action cycle.

This chapter reviews the role of prior knowledge for the integration of sensory information and discusses how priors can be modified by experience. It shows that prior knowledge affects perception at different levels. First, it often serves as an additional cue at the level of cue integration. Second, prior knowledge of statistical regularities in the world is also important for interpreting cues, because it can provide information needed to disambiguate sensory information and thus determines the shape of the likelihood function. Third, prior knowledge is also effective at a higher cognitive level, where it determines whether and how cues are integrated. The chapter concludes by discussing where prior knowledge comes from and how flexible it is.

The 21st century brought about a shift in the types of models used to explain the processing of sensory information by the cerebral cortex. Until now, these models have overwhelmingly emphasized the feedforward direction for the transfer of sensory information, and it is only recently that a more balanced view of the cortical network has emerged. This chapter summarizes this evolution and focuses on the question of the role of feedback connections in the processing of sensory information. It uses the visual system as a model since most of what is known concerning the processing of sensory inputs by the brain comes from studying that system.

This chapter outlines the important but underrecognized multiple contributions of sensory-perceptual and sensory-motor information to concepts and to thinking. It covers research and findings from developmental psychology, cognitive psychology, philosophical psychology, naturalistic experiments in economics, and other areas to argue for the essential role that “thinking with our senses” assumes in enabling agility of mind. At an abstract level, the chapter is broadly grouped into four sections, concentrating on: the integral contribution of perceptual and action-related information to mental concepts or representations; the ways in which both current perception and current actions (e.g., gestures) may guide and support thinking and insight; the key importance of the “embodied” and “grounded” nature of mental representations in enabling innovative, and even completely novel, uses of language; and the role of so-called epistemic objects in thinking, including the pervasive and sometimes illicit effects of the specifically physical nature of language (the sensory-perceptual aspects of words as objects in the world, that can be heard and/or seen) on the nature and direction of thought.

This chapter reviews the development of the visual system in birds and mammals. It briefly describes the first phase, when the system is organized without much information from sensory organs. It also discusses the period when sensory information starts to affect the wiring of the visual system nuclei, and combine the development of visually guided behavior with that of the visual system. Finally, it deals with the question of how early experience helps birds to recognize and memorize important visual features of their life, as for example, parents or sexual partner; and provides some ideas about the neuronal mechanisms underlying such early learning events, which have been called imprinting because of their extreme stability of memorization.

In order for perception to be effective, many noisy and ambiguous sensory signals across different modalities (for example, vision, audition) must be integrated into stable percepts. This chapter explores dynamic coordination in the integration of sensory information, with an emphasis on why and how the brain integrates sensory signals. It also considers how the brain knows when to integrate signals and when to treat them separately.

All sensory information, except for olfaction, passes through the synaptic network of the thalamus just before reaching the cerebral cortex, suggesting that the thalamus may exert a powerful influence on sensory and motor processing. However, the connection is not unidirectional: layer VI of the cerebral cortex contributes up to 50% of the synapses on thalamic relay neurons, indicating that the thalamus and cerebral cortex are intimately associated in some form of reciprocal loop. Many previous studies have shown the thalamus to be critically involved in a wide variety of phenomena, including the generation of the electroencephalogram (EEG), the blocking of transmission of sensory information during slow-wave sleep, and the generation of generalized seizures. This chapter examines, at the subcellular, cellular, and network levels, the biophysical mechanisms for all three of these and related phenomena.

This chapter discusses the concept of adaptation and how it started out as a threshold shift of the visual system, after exposure to sudden changes in illumination level, to a new steady state—not much different from fatigue. It was eventually found to be a feature of almost all sensory systems, with the exception of a few, such as the nociceptive system. Three sets of experiments are discussed here, relating to the simultaneous difference limen of the visual system, directional hearing in the auditory system, and the time course of adaptation at the peripheral and cortical levels of the auditory system, with a few excursions into the somesthetic system. All three sets lead to the conclusion that adaptation is not a mere loss of sensory information, but, in quite a few situations in sensory systems adaptation, may result in an actual gain in sensory information.

This chapter discusses deficits that reflect a disturbance of the processing of sensory information. Specifically, it discusses the assessment and treatment of defects in visuospatial processes, imaginal processes, and constructional processes.

This chapter examines the effect of temporal preparation on premotor processes. It explains that temporal preparation is a ubiquitous and fundamental feature of human behaviour and it is linked to the ability to anticipate future events and to adjust behaviour accordingly in order to optimize performance. It also mentions the availability of ample evidence that that temporal preparation also operates on premotoric levels by speeding up the duration of these processes. This speeding many not only shorten reaction-time but also enable a more accurate analysis of incoming sensory information.

This chapter provides a brief overview of the “historical” findings and some of the most relevant observations that advance the understanding of the amazing complexity of neuron-astrocyte partnership in the function of the brain. It describes the role of astrocyte in behavior. It discusses the role of astrocytes in epilepsy. This chapter suggests that astrocytes might hold the key to understanding the pathogenesis of brain disorders. It looks at the role of astrocytes in the processing of sensory information and in the genesis of brain disorders.

This book introduces a conceptual framework for brain function based on large populations of neurons. It advances the hypothesis that emergent properties are high-level effects that depend on lower-level phenomena in some systematic way, drawing on the idea that brains are computational in nature. Areas and topics related to computational neuroscience covered in this book include computational mechanisms in neurons, analysis of signal processing in neural circuits, representation of sensory information, systems models of sensorimotor integration, and computational approaches to plasticity. The book emphasizes the importance of single neuron models as the foundation into which network models must eventually fit. It also provides a background discussion on neuroscience and the science of computation.