Showing papers on "Topographic map (neuroanatomy) published in 2003"
TL;DR: The ephrin-As are differentially expressed in distinct subpopulations of neurons and are likely to participate, along with the ORs, as one of a complement of guidance receptors governing the targeting of like axons to precise locations in the olfactory bulb.
207 citations
TL;DR: There was still considerable mis-targeting after four months of regeneration of the P2-tau:LacZ line of mice because the regenerating P2 axons now terminated in numerous inappropriate glomeruli which were widely dispersed over the olfactory bulb.
Abstract: During development, primary olfactory axons typically grow to their topographically correct target zone without extensive remodelling. Similarly, in adults, new axons arising from the normal turnover of sensory neurons essentially project to their target without error. In the present study we have examined axon targeting in the olfactory pathway following extensive chemical ablation of the olfactory neuroepithelium in the P2-tau:LacZ line of mice. These mice express LacZ in the P2 subpopulation of primary olfactory neurons whose axons target topographically fixed glomeruli on the medial and lateral surfaces of the olfactory bulb. Intraperitoneal injections of dichlobenil selectively destroyed the sensory neuroepithelium of the nasal cavity without direct physical insult to the olfactory neuron pathway. Primary olfactory neurons regenerated and LacZ staining revealed the trajectory of the P2 axons. Rather than project solely to their topographically appropriate glomeruli, the regenerating P2 axons now terminated in numerous inappropriate glomeruli which were widely dispersed over the olfactory bulb. While these errors in targeting were refined over time, there was still considerable mis-targeting after four months of regeneration.
38 citations
TL;DR: Data suggest that 1-2 months post-lesion the deafferented cortex behaves like normal visual cortex, in contrast to remote, non-deprived cortex, and that LTP-like mechanisms, and thereby cortical reorganization, might still be facilitated, while possible excessive hyperexcitability is balanced by the moderately increased GABAergic control.
32 citations
TL;DR: Results not only suggest an activity-dependent regulation of the glutamate levels in visual cortex but also imply a role for perilesional cortical regions in topographic map reorganization following sensory deafferentation.
26 citations
TL;DR: The conclusion is drawn that the phosphorylation changes observed at 14 days are related to a delayed reorganization of the retinotopic map of the striate cortex.
14 citations
TL;DR: The results raise the possibility that Pax6 is upstream of EphB2 and that its graded expression defines the dorso-ventral axis of the retino-tectal projection.
13 citations
20 Mar 2003
TL;DR: The directional tuning of neurons and local field potentials recorded in the motor cortex of monkeys performing center out arm movements is found to be more similar than expected by chance to that of nearby neurons and single neurons recorded from the same electrodes.
Abstract: The spatial organization of tuning properties of neurons in the primate motor cortex is still unknown. Here, we analyze the directional tuning of neurons and local field potentials recorded in the motor cortex of monkeys performing center out arm movements. We found that the tuning of nearby neurons, and of single neurons and local field potentials recorded from the same electrodes is more similar than expected by chance. These findings are in agreement with a spatial organization of the tuning properties in motor cortex.
4 citations
15 Apr 2003
TL;DR: The auditory system makes it possible to identify and localize sounds and their sources from a complex and dynamic acoustic environment and must encode the relevant cues and appropriately distribute that information among a myriad of auditory processing centers in the brain.
Abstract: The auditory system makes it possible to identify and localize sounds and their sources from a complex and dynamic acoustic environment To accomplish these tasks, the auditory system must encode the relevant cues and appropriately distribute that information among a myriad of auditory processing centers in the brain These events are accomplished in multiple parallel pathways involving an extensive array of interconnected nuclei and fields in the brainstem, thalamus, and cerebral cortex Both ascending and descending channels contribute to a dynamic exchange in which the response properties of neurons at every level of processing can be modified as needed Among mammals, the organization of subcortical auditory nuclei and associated pathways is highly conserved By comparison, the number and organization of auditory fields in cortex varies across taxonomic groups In nonhuman primates, three major regions containing some 12 subdivisions occupy the superior temporal region where auditory inputs are processed in serial and parallel Outputs target multiple auditory-related domains in temporal, prefrontal, and posterior parietal cortex From these many interactions information concerning the identity and location of acoustic objects is extracted and used to guide behavior
Keywords:
auditory;
brainstem;
cortex;
hearing;
monkey;
temporal;
thalamus
3 citations