Somatosensory cortical input to the striatum

The information from whiskers is processed in layer IV of the cortex by groups of neurones arranged in discrete functional units known as barrels. Each barrel processes input obtained from a single whisker. The barrel cortex can be differentiated into the cytochrome rich barrel centres and the septal cells surrounding the barrels. Previous work in the laboratory had established two cortical inputs to striatum from the barrel cortex. One of these arises from septal cells and is bilateral and composed of thin calibre fibres. The other route involves the barrel centres, is only unilaterally represented and is composed of topographically arranged, thick fibres. Based on these morphological differences, the postsynaptic targets of the two pathways with reference to the two output pathways of the striatum were examined. A method was also developed to examine the physiological consequences of stimulation of the two pathways upon the striatal output cells of the anaesthetised rat in both normal and dopamine-depleted animals. An anatomical study of the cortical input to the GABAergic intemeurones was also undertaken as these cells strongly modulate the output of striatal neurones.The pathways differ in their connectivity, with the bilateral pathway contacting the neurones of the striatopallidal pathway more often than the fibres of the topographic system. The stimulation of the two pathways can depolarise striatal cells and give rise to EPSPs, which can be differentiated based on their rise times. EPSPs in response to whisker pad stimulation have a rapid rise time, while the contralateral cortically derived EPSPs are slower to rise and the spike initiation latency more variable. Both pathways interacted at the level of a single striatal cell and gave rise to a summation of EPSPs at a time interval of 10ms, followed by a period of inhibition, the extent of which was dependent on the order and source of the stimuli. This pattern ofinteraction was not seen in cortical neurones. In dopamine depleted animals both stimuli were also able to depolarise the spiny neurones to their firing threshold. However the EPSPs to whisker pad stimulation were significantly slower to rise compared to control animals and were similar to the rise times of EPSPs in response to contralateral cortical stimulation. The interaction of the two pathways was also affected by the loss of dopamine and the summation of EPSP amplitude observed when stimuli were delivered 1 Oms apart in control animals was no longer present. The anatomical study revealed that GABAergic intemeurones receive convergent cortical input from both motor and sensory cortices and that their pattern of innervation is different from the cortical innervation of striatal output neuronesThe results of this thesis suggest that the two inputs from the barrel cortex differ in their physiological influence on striatal neurones, and that they might convey different aspects of somatosensory information to the striatum. The changes observed in dopamine-lesioned animals indicate that the topographic, ipsilateral pathway is selectively affected by the loss of dopamine suggesting that dopaminedepletion does not have a generalized action that is independent of presynaptic or postsynaptic origins. Rather its effects are specific to the neuronal subtype affected as well to the origin of the synapses. The complex pattern of innervation of striatal intemeurones suggests that these cells play a very important role in striatal physiology and that their modulation by dopamine may serve as a possible explanation for the effects seen after lesion in this stud

Visual Cortex

The neurosciences have experienced tremendous and wonderful progress in many areas, and the spectrum encompassing the neurosciences is expansive. Suffice it to mention a few classical fields: electrophysiology, genetics, physics, computer sciences, and more recently, social and marketing neurosciences. Of course, this large growth resulted in the production of many books. Perhaps the visual system and the visual cortex were in the vanguard because most animals do not produce their own light and offer thus the invaluable advantage of allowing investigators to conduct experiments in full control of the stimulus. In addition, the fascinating evolution of scientific techniques, the immense productivity of recent research, and the ensuing literature make it virtually impossible to publish in a single volume all worthwhile work accomplished throughout the scientific world. The days when a single individual, as Diderot, could undertake the production of an encyclopedia are gone forever. Indeed most approaches to studying the nervous system are valid and neuroscientists produce an almost astronomical number of interesting data accompanied by extremely worthy hypotheses which in turn generate new ventures in search of brain functions. Yet, it is fully justified to make an encore and to publish a book dedicated to visual cortex and beyond. Many reasons validate a book assembling chapters written by active researchers. Each has the opportunity to bind together data and explore original ideas whose fate will not fall into the hands of uncompromising reviewers of traditional journals. This book focuses on the cerebral cortex with a large emphasis on vision. Yet it offers the reader diverse approaches employed to investigate the brain, for instance, computer simulation, cellular responses, or rivalry between various targets and goal directed actions. This volume thus covers a large spectrum of research even though it is impossible to include all topics in the extremely diverse field of neurosciences

Brain Computations and Connectivity [2nd edition]

This is an open access title available under the terms of a CC BY-NC-ND 4.0 International licence. It is free to read on the Oxford Academic platform and offered as a free PDF download from OUP and selected open access locations. Brain Computations and Connectivity is about how the brain works. In order to understand this, it is essential to know what is computed by different brain systems; and how the computations are performed. The aim of this book is to elucidate what is computed in different brain systems; and to describe current biologically plausible computational approaches and models of how each of these brain systems computes. Understanding the brain in this way has enormous potential for understanding ourselves better in health and in disease. Potential applications of this understanding are to the treatment of the brain in disease; and to artificial intelligence which will benefit from knowledge of how the brain performs many of its extraordinarily impressive functions. This book is pioneering in taking this approach to brain function: to consider what is computed by many of our brain systems; and how it is computed, and updates by much new evidence including the connectivity of the human brain the earlier book: Rolls (2021) Brain Computations: What and How, Oxford University Press. Brain Computations and Connectivity will be of interest to all scientists interested in brain function and how the brain works, whether they are from neuroscience, or from medical sciences including neurology and psychiatry, or from the area of computational science including machine learning and artificial intelligence, or from areas such as theoretical physics

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 267, January 1985

This publication is a cumulative index to the abstracts contained in the Supplements 255 through 266 of Aerospace Medicine and Biology: A Continuing Bibliography. It includes seven indexes--subject, personal author, corporate source, foreign technology, contract number, report number, and accession number

Life Sciences Program Tasks and Bibliography for FY 1996

This document includes information on all peer reviewed projects funded by the Office of Life and Microgravity Sciences and Applications, Life Sciences Division during fiscal year 1996. This document will be published annually and made available to scientists in the space life sciences field both as a hard copy and as an interactive Internet web page

Life Sciences Program Tasks and Bibliography for FY 1997

This document includes information on all peer reviewed projects funded by the Office of Life and Microgravity Sciences and Applications, Life Sciences Division during fiscal year 1997. This document will be published annually and made available to scientists in the space life sciences field both as a hard copy and as an interactive internet web page

The role of phonology in visual word recognition: evidence from Chinese

Posters - Letter/Word Processing V: abstract no. 5024The hypothesis of bidirectional coupling of orthography and phonology predicts that phonology plays a role in visual word recognition, as observed in the effects of feedforward and feedback spelling to sound consistency on lexical decision. However, because orthography and phonology are closely related in alphabetic languages (homophones in alphabetic languages are usually orthographically similar), it is difficult to exclude an influence of orthography on phonological effects in visual word recognition. Chinese languages contain many written homophones that are orthographically dissimilar, allowing a test of the claim that phonological effects can be independent of orthographic similarity. We report a study of visual word recognition in Chinese based on a mega-analysis of lexical decision performance with 500 characters. The results from multiple regression analyses, after controlling for orthographic frequency, stroke number, and radical frequency, showed main effects of feedforward and feedback consistency, as well as interactions between these variables and phonological frequency and number of homophones. Implications of these results for resonance models of visual word recognition are discussed.postprin

Interactive effects of orthography and semantics in Chinese picture naming

Posters - Language Production/Writing: abstract no. 4035Picture-naming performance in English and Dutch is enhanced by presentation of a word that is similar in form to the picture name. However, it is unclear whether facilitation has an orthographic or a phonological locus. We investigated the loci of the facilitation effect in Cantonese Chinese speakers by manipulating—at three SOAs (2100, 0, and 1100 msec)—semantic, orthographic, and phonological similarity. We identified an effect of orthographic facilitation that was independent of and larger than phonological facilitation across all SOAs. Semantic interference was also found at SOAs of 2100 and 0 msec. Critically, an interaction of semantics and orthography was observed at an SOA of 1100 msec. This interaction suggests that independent effects of orthographic facilitation on picture naming are located either at the level of semantic processing or at the lemma level and are not due to the activation of picture name segments at the level of phonological retrieval.postprin