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Area V1 (area + v1)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Centre-surround interactions in response to natural scene stimulation in the primary visual cortex

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2005
Kun Guo
Abstract Centre,surround interaction in the primary visual cortex (area V1) has been studied extensively using artificial, abstract stimulus patterns, such as bars, gratings and simple texture patterns. In this experiment, we extend the study of centre,surround interaction by using natural scene images. We systematically varied the contrast of natural image surrounds presented outside the classical receptive field (CRF), and recorded neuronal response to a natural image patch presented within the CRF in area V1 of awake, fixating macaques. For the majority of neurons (67 out of 111), the natural image surrounds profoundly modulated, mainly by suppressing, neuronal responses to CRF images. These modulatory effects started at the earliest stage of neuronal responses, and often depended on the contrast and higher-order structures of the surrounds. For 47 out of 67 neurons, randomising the phases of the Fourier spectrum of the natural image surround diminished the centre,surround interaction. Our results suggest that the centre,surround interaction in area V1 can be extended to natural vision, and is sensitive to the higher-order structures of natural scene images, such as image contours. [source]

Cortical inhibitory circuits in eye-movement generation

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003
Peter H. Schiller
Abstract The role inhibitory circuits play in target selection with saccadic eye movements was examined in area V1, the frontal eye fields (FEF) and the lateral intraparietal sulcus (LIP) of the Rhesus Macaque monkey by making local infusions of the GABA agonist muscimol and antagonist bicuculline. In V1, both agents greatly interfered with target selection and visual discrimination of stimuli placed into the receptive field of the affected neurons. In the FEF, bicuculline facilitated target selection without affecting visual discrimination and generated many spontaneous saccades. Muscimol in the FEF interfered with saccadic eye-movement generation. In the LIP, bicuculline was ineffective and muscimol had only a small effect. These findings suggest that in the FEF GABAergic inhibitory circuits play a central role in eye-movement generation whereas in V1 these circuits are essential for visual analysis. Inhibitory circuits in the LIP do not appear to play a central role in target selection and in visual discrimination. [source]

Saccadic eye movements evoked by microstimulation of striate cortex

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2003
Edward J. Tehovnik
Abstract Experiments were performed to assess the excitability of neural elements activated while inducing saccadic eye movements electrically from different cortical layers of striate cortex (area V1) in rhesus monkeys. Excitability was assessed by measuring current thresholds, saccadic latencies, chronaxies, and the effectiveness of anode-first vs. cathode-first pulses. Minimum current thresholds for the evocation of saccades (i.e. less than 5 µA) were observed when the deepest layers of V1 were stimulated. The shortest saccadic latencies were also observed at these depths. The shortest latency at 10 times the threshold current was 49 ms on average. The chronaxies of the elements mediating saccades were less in deep V1 (i.e. 0.17 ms) than in superficial V1 (i.e. 0.23 ms). Anode-first pulses were more effective at evoking saccades from superficial V1, whereas cathode-first pulses were more effective at evoking saccades from deep V1. These results indicate that the excitability properties of superficial and deep V1 are distinct for the generation of saccades. Moreover, the excitability of elements mediating saccades in V1 of monkeys is comparable to that of elements mediating phosphenes in human V1. [source]

Developmental and activity-dependent genomic occupancy profiles of CREB in monkey area V1

GENES, BRAIN AND BEHAVIOR, Issue 2 2009
J. Lalonde
The mammalian neocortex displays significant plastic rearrangement in response to altered sensory input, especially during early postnatal development. It is believed that cyclic AMP-response element-binding (CREB) plays an important role in orchestrating the molecular events that guide neuroplastic change, although the details of its genomic targets during normal postnatal development or in response to sensory deprivation remain unknown. Here, we performed CREB chromatin immunoprecipitation (ChIP) from monkey area V1 tissue and hybridized enriched DNA fragments to promoter microarrays (ChIP chip analysis). Our goal was to determine and categorize the CREB regulon in monkey area V1 at two distinct developmental stages (peak of critical period vs. adulthood) and after 5 days of monocular enucleation (ME) at both ages. Classification of enriched candidates showed that the majority of isolated promoter loci (n = 795) were common to all four conditions. A particularly interesting group of candidates (n = 192) was specific to samples derived from enucleated infant area V1. Gene ontology analysis of CREB targets during early postnatal development showed a subgroup of genes implicated in cytoskeleton-based structural modification. Analysis of messenger RNA expression (quantitative real-time,polymerase chain reaction) of candidate genes showed striking differences in expression profiles between infant and adult area V1 after ME. Our study represents the first extensive genomic analysis of CREB DNA occupancy in monkey neocortex and provides new insight into the multifaceted transcriptional role of CREB in guiding neuroplastic change. [source]