Anatomical Substrate (anatomical + substrate)

Distribution by Scientific Domains

Selected Abstracts

The role of early neural activity in the maturation of turtle retinal function

In the developing vertebrate retina, ganglion cells fire spontaneous bursts of action potentials long before the eye becomes exposed to sensory experience at birth. These early bursts are synchronised between neighbouring retinal ganglion cells (RGCs), yielding unique spatiotemporal patterns: ,waves' of activity sweep across large retinal areas every few minutes. Both at retinal and extraretinal levels, these embryonic retinal waves are believed to guide the wiring of the visual system using hebbian mechanisms of synaptic strengthening. In the first part of this review, we recapitulate the evidence for a role of these embryonic spontaneous bursts of activity in shaping developing complex receptive field properties of RGCs in the turtle embryonic retina. We also discuss the role of visual experience in establishing RGC visual functions, and how spontaneous activity and visual experience interact to bring developing receptive fields to maturation. We have hypothesised that the physiological changes associated with development reflect modifications in the dendritic arbours of RGCs, the anatomical substrate of their receptive fields. We demonstrate that there is a temporal correlation between the period of receptive field expansion and that of dendritic growth. Moreover, the immature spontaneous activity contributes to dendritic growth in developing RGCs. Intracellular staining of RGCs reveals, however, that immature receptive fields only rarely show direct correlation with the layout of the corresponding dendritic tree. To investigate the possibility that not only the presence of the spontaneous activity, but even the precise spatiotemporal patterns encoded in retinal waves might contribute to the refinement of retinal neural circuitry, first we must clarify the mechanisms mediating the generation and propagation of these waves across development. In the second part of this review, we present evidence that turtle retinal waves, visualised using calcium imaging, exhibit profound changes in their spatiotemporal patterns during development. From fast waves sweeping across large retinal areas and recruiting many cells on their trajectory at early stages, waves become slower and eventually stop propagating towards hatching, when they become stationary patches of neighbouring coactive RGCs. A developmental switch from excitatory to inhibitory GABAA responses appears to mediate the modification in spontaneous activity patterns while the retina develops. Future chronic studies using specific spatiotemporal alterations of the waves will shed a new light on how the wave dynamics help in sculpting retinal receptive fields. [source]

Cognitive disturbances in primary blepharospasm,

Gabriela Gonzalez Alemán PhD
Abstract The common belief that primary dystonia is a purely motor disorder with no anatomical substrate and no other accompanying neurological dysfunction has recently been challenged. In addition, there is increasing evidence that the basal ganglia besides motor control, plays a role in cognitive functioning. However, no systematic cognitive performance evaluation has been carried out in patients with primary blepharospasm (BS), one of the most common forms of adult dystonia. We evaluated a series of 20 patients with primary BS and a group of 17 controls matched by severity of mood symptoms, age, and sex. BS patients performed significantly worse on the Luria sequencing test, Purdue pegboard test, reciprocal coordination, tactile denomination, and reverse visuospatial span and the differences persisted after correction for age, duration of disease, severity of BS, and degree of depression. The Wisconsin card sorting test showed no statistical difference, but BS patients made more errors and more perseverative answers than expected according to population means, whereas the control group performed poorly but within normal parameters. Our findings suggest broad cortical involvement in focal dystonia that is not correlated with the severity or duration of dystonia. © 2009 Movement Disorder Society [source]

Bilateral symmetric organization of neural elements in the visual system of a coelenterate, Tripedalia cystophora (Cubozoa)

Linda Parkefelt
Abstract Cubozoans differ from other cnidarians by their body architecture and nervous system structure. In the medusa stage they possess the most advanced visual system within the phylum, located in sophisticated sensory structures, rhopalia. The rhopalium is a club-shaped structure with paired pit-shaped pigment cup eyes, paired slit-shaped pigment cup eyes, and two complex camera-type eyes: one small upper lens eye and one large lower lens eye. The medusa carries four rhopalia and visual processing and locomotor rhythm generation takes place in the rhopalia. We show here a bilaterally symmetric organization of neurons, with commissures connecting the two sides, in the rhopalium of the cubozoan Tripedalia cystophora. The fortuitous observation that a subset of neurons is strongly immunoreactive for a PCNA (proliferating cell nuclear antigen)-like epitope allowed us to analyze the organization of these neurons in detail. Distinct PCNA-immunoreactive (PCNA-ir) nuclei form six bilateral pairs that are associated with the slit eyes, pit eyes, upper lens eye, and the posterior wall of the rhopalium. Three commissures connect the clusters of the two sides and all clusters in the rhopalium have connections to the area around the base of the stalk. This neuronal system provides an anatomical substrate for integration of visual signals from the different eyes. J. Comp. Neurol. 492:251,262, 2005. © 2005 Wiley-Liss, Inc. [source]

Hippocampal lesions impair spatial memory performance, but not song,A developmental study of independent memory systems in the zebra finch

David J. Bailey
Abstract Songbirds demonstrate song- and spatial-learning, forms of memory that appear distinct in formal characteristics and fitting the descriptions and criteria of procedural and episodic-like memory function, respectively. As in other vertebrates, the neural pathways underlying these forms of memory may also be dissociable, and include the corresponding song circuit and hippocampus (HP). Whether (or not) these two memory systems interact is unknown. Interestingly, the HP distinguishes itself as a site of immediate early gene expression in response to song and as a site of estrogen synthesis, a steroid involved in song learning. Thus, an interaction between these memory systems and their anatomical substrates appears reasonable to hypothesize, particularly during development. To test this idea, juvenile male or female zebra finches received chemical lesions of the HP at various points during song learning, as did adults. Song structure, singing behavior, song preference, and spatial memory were tested in adulthood. Although lesions of the HP severely compromised HP-dependent spatial memory function across all ages and in both sexes, we were unable to detect any effects of HP lesions on song learning, singing, or song structure in males. Interestingly, females lesioned as adults, but not as juveniles, did lose the characteristic preference for their father's song. Since compromise of the neural circuits that subserve episodic-like memory does very little (if anything) to affect procedural-like (song learning) memory, we conclude that these memory systems and their anatomical substrates are well dissociated in the developing male zebra finch. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009 [source]

Brainstem respiratory control: Substrates of respiratory failure of multiple system atrophy

Eduardo E. Benarroch MD
Abstract Multiple system atrophy may manifest with severe respiratory disorders, including sleep apnea and laryngeal stridor, which reflect a failure of automatic control of respiration. This function depends on a pontomedullary network of interconnected neurons located in the parabrachial/Kölliker Fuse nucleus in the pons, nucleus of the solitary tract, and ventrolateral medulla. Neurons in the preBötzinger complex expressing neurokinin-1 receptors are critically involved in respiratory rhythmogenesis, whereas serotonergic neurons in the medullary raphe and glutamatergic neurons located close to the ventral medullary surface are involved in central chemosensitivity to hypercapnia, hypoxia, or both. Pathological studies using selective neurochemical markers indicate that these neuronal groups are affected in multiple system atrophy. This finding may provide potential anatomical substrates for the respiratory manifestations of the disease. © 2006 Movement Disorder Society [source]