Neuroscience
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In recent years, a growing body of research has addressed the nature and mechanism of material perception. Material perception entails perceiving and recognizing a material, surface quality or internal state of an object based on sensory stimuli such as visual, tactile, and/or auditory sensations. This process is ongoing in every aspect of daily life. ⋯ Our main focus is on vision, but every sensory modality is involved in material perception. Information obtained through different sensory modalities is closely linked in material perception. Such cross-modal processing is another important feature of material perception, and will also be covered in this review.
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Review
Brain Stem Neural Circuits of Horizontal and Vertical Saccade Systems and Their Frame of Reference.
Sensory signals for eye movements (visual and vestibular) are initially coded in different frames of reference but finally translated into common coordinates, and share the same final common pathway, namely the same population of extraocular motoneurons. From clinical studies in humans and lesion studies in animals, it is generally accepted that voluntary saccadic eye movements are organized in horizontal and vertical Cartesian coordinates. However, this issue is not settled yet, because neural circuits for vertical saccades remain unidentified. ⋯ Comparing well-known vestibuloocular pathways with our findings of commissural excitation and inhibition between both superior colliculi, we proposed that the saccade system uses the same frame of reference as the vestibuloocular system, common semicircular canal coordinate. This proposal is mainly based on marked similarities (1) between output neural circuitry from one superior colliculus to extraocular motoneurons and that from a respective canal to its innervating extraocular motoneurons, (2) of patterns of commissural reciprocal inhibitions between upward saccade system on one side and downward system on the other, and between anterior canal system on one side and posterior canal system on the other, and (3) between the neural circuits of saccade and quick phase of vestibular nystagmus sharing brainstem burst neurons. In support of the proposal, commissural excitation of the superior colliculi may help to maintain Listing's law in saccades in spite of using semicircular canal coordinate.
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The human brain is known by its ability to modify and update existing memories, mediated by underlying neuronal plasticity. This ability is facilitated by two main phenomena, interference and generalization. ⋯ While each of these two phenomena may be well known separately, we review recent evidence primarily in perceptual and motor skill memory, spanning synaptic, neural systems-level, and behavioral research, suggesting that although the outcomes are different, the underlying neural and behavioral processes responsible for their inducements share numerous commonalities. The reviewed literature may imply a common mechanism underlying these two phenomena, and suggests a unified framework of memory and learning in the human brain.