Experimental and clinical studies in primates indicate that visual information is stored and retrieved by interactions between the temporal association area and the medial temporal lobe structures including hippocampus. Recent findings from single-neuron recordings have provided new evidence that perceptuai aspects of the temporal neocortex are closely related to its memory function based on association. On the grounds that long-term memory of objects is acquired and organized by neuronal tuning and associative mechanisms, I further present a model of the cognitive memory system that unifies perception and imagery.

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Recent neurophysiological as well as neuropsychological studies provided several hypotheses on how motor programs are generated in the central nervous system. Amajor conclusion emerged from neurophysiological studies on the premotor cortex (PM)of monkeys that each of movement parameters such as amplitude and direction is distinctively programmed in the PM by serial integration, rather than by parallel distributed processing.

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The brain adopts various kind of neural coding in accordance with the structure of the external information space and the property of the required information processing. In peripheral regions, rigidly structured codings such as columnar or hypercolumnar structures are known. On the other hand, there are experimental results which suggest that a more flexible and loose codings are used in the brain area where associative information processing and memory are included. In this paper, it is proposed that a sparsely coded associative memory using a non-monotonic neuron model is a promising candidate of the brain coding in the inferio-temporal area which takes an important role in the delayed matching task.

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This paper describes a computational approach to the study of visual information processing. Computational studies have shown that many vision problems do not have a unique solution using information available in the retinal images. Most computational models therefore impose additional physically plausible constraints. In this paper, we provide a computational framework for visual motion analysis, in particular models of 2D velocity field computation and recovery of 3D structure from motion information. We also illustrate how computational models provide insights on the neural mechanisms and simulate physiological and psychophysical data.

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Most neurons in the prestriate area MT of the macaque monkey exhibit direction selectivity to moving visual stimuli. Deficits in the initiation of pursuit eye movements and those in the discrimination of the direction of moving random dot stimuli have been produced by MT lesion. Also, facilitation of the direction discrimination has been produced by MT microstimulation. These experiments provide evidence of causal relation between activities of MT neurons and motion perception. However, recent studies have shown that MT neurons are also affected by visual cues that are not directly involved in the motion perception. It is suggested that integration of motion-related inputs and other inputs observed in MT neurons is important for the segmentation of visual images into different objects.

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This paper summarizes a series of psychophysical studies to suggest representation of visible surfaces at an early level in the visual pathway, taking two phenomena as subjects; the depth propagation effect, where quite localized binocular disparity determines the perceived depth of the surrounding surface by means of extrapolation, and the neon effect, where localized figural cues to transparency have an effect on perceived color and brightness of the surrounding surface by filling-in or spreading. Critical roles of monocular-level information in occurrence of these effects suggest early origin of these perceptual surface formation.

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Functional mapping of human brain with ultrafast MRI is reviewed. The method is based on measuring the loc al changes in the magnetic properties of the hemoglobin in blood while the subject performs a task or receives sensory stimulation.

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For the elucidation of higher brain functions, it seems to be indispensable to introduce the new methods which enable to measure the neural activity from 2 or 3-dimensional space of a part of brain simultaneously. An optical measurement of neural activity with a voltage-sensitive dye is one of such technique developed in the rccent years. The optical recordings (imagings) offer the new aspect of thhe study of brain functions.

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A non-invasive technique, magnetoencephalography (MEG) can measure magnetic fields originating mainly from the intracellular current flow through the apical dendrites of cortical pyramidal neurons, which is caused by excitatory synaptic inputs. Our recent MEG studies on sensory and motor functions of the human brain are reviewed. MEG provides an effective non-invasive approach to the studies of human brain functions, especially when combined with appropriate animal experiments.

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