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  • 1
    Language: English
    In: Brain Research, 24 January 2012, Vol.1434, pp.34-46
    Description: Humans and other primates move their eyes several times per second to foveate at different locations of a visual scene. What features of a scene guide eye movements in natural vision? We recorded eye movements of three monkeys during free exploration of natural scenes and propose a simple model to explain their dynamics. We use the spatial clustering of fixation positions to define the monkeys' subjective regions-of-interest (ROI) in natural scenes. For most images the subjective ROIs match significantly the computed saliency of the natural scene, except when the image contains human or primate faces. We also investigated the temporal sequence of eye movements by computing the probability that a fixation will be made inside or outside of the ROI, given the current fixation position. We fitted a Markov chain model to the sequence of fixation positions, and find that fixations made inside a ROI are more likely to be followed by another fixation in the same ROI. This is true, independent of the image saliency in the area of the ROI. Our results show that certain regions in a natural scene are explored locally before directing the focus to another local region. This strategy could allow for quick integration of the visual features that constitute an object, and efficient segmentation of objects from other objects and the background during free viewing of natural scenes.
    Keywords: Eye Movement ; Scan Path ; Fixation Map ; Natural Vision ; Monkey ; Anatomy & Physiology
    ISSN: 0006-8993
    E-ISSN: 1872-6240
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  • 2
    Language: English
    In: Brain Research, 1991, Vol.544(2), pp.329-330
    Description: In vivo microdialysis techniques were used to examine whether endogenous excitatory amino acids exert a tonic facilitatory influence on striatal dopamine release. Local application of NMDA and non-NMDA antagonists at 10 μM was without an effect on basal dopamine release while 100 μM and 1 mM of these drugs significantly enhanced the release. Our findings do not support the idea that excitatory amino acids have a tonic excitatory effect on striatal dopamine release.
    Keywords: Excitatory Amino Acid ; Dopamine ; Microdialysis ; Anatomy & Physiology
    ISSN: 0006-8993
    E-ISSN: 1872-6240
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  • 3
    Language: English
    In: Brain Research, 2003, Vol.979(1), pp.57-64
    Description: The mitogen-activated protein kinases (MAPKs) are a family of signal transduction mediators that regulate a host of cellular activities, including cell growth and proliferation, and differentiation and survival, via sequential phosphorylation and activation of a cassette of three protein kinases. MAPKs are also recruited when the brain undergoes synaptic plasticity and remodeling (e.g., during induction of long-term potentiation, learning and memory consolidation). The activities of some of these kinases are altered in response to various acute stimuli such as ischemic insult, visceral pain and electroconvulsive shock. In the present study we used immunoblotting techniques to examine the effects of acute and repeated restraint stress on the phosphorylation state of three MAPKs, the extracellular signal-regulated kinase Erk1/2, c-Jun-N-terminal kinase/stress-activated protein kinase (JNK/SAPK) and p38 MAPK, in different brain regions. A single exposure to 30 min of restraint stress-elevated phospho-Erk1/2 (P-Erk1/2) levels in all three brain regions examined (hippocampus, medial prefrontal cortex and cingulate cortex), but did not alter the phosphorylation pattern of the other two MAPKs in any region. In marked contrast, exposure to restraint for 11 days (30 min/day) reduced the levels of all three MAPKs, but only in the prefrontal cortex. The results are compared to the reported effects of acute and chronic stress on other biochemical and functional measures.
    Keywords: Restraint Stress ; MAP Kinases ; Phosphorylation ; Prefrontal Cortex ; Immunoblotting ; Anatomy & Physiology
    ISSN: 0006-8993
    E-ISSN: 1872-6240
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  • 4
    Language: English
    In: Brain Research, 1992, Vol.599(1), pp.51-56
    Description: At present, it is unclear whether ligands which bind at the benzodiazepine/GABA receptor complex play a tonic modulatory role with regard to striatal dopamine (DA) transmission. The present study was designed to examine the effects of Ro15-1788, a benzodiazepine (BZ) receptor antagonist, and SR 95531, a GABA receptor antagonist, on striatal extracellular DA (DA ) concentrations in anesthetized and awake rats using the technique of in vivo microdialysis. Local administration of Ro15-1788 resulted in a dose-dependent increase in DA in both anesthetized and awake animals. The Ro15-1788-induced increase in DA was blocked by coadministration of the BZ agonist diazepam, as well as GABA. Local administration of SR 95531 also resulted in a dose-dependent alteration in striatal DA levels in both anesthetized and awake animals. The SR 95531-induced increase in DA was blocked by coadministration of GABA. The results suggest that GABA may play a tonic inhibitory role with regard to striatal DA transmission.
    Keywords: Dopamine ; Γ-Aminobutyric Acid ; Benzodiazepine ; Striatum ; Sr 95531 ; Ro15-1788 ; Microdialysis ; Anatomy & Physiology
    ISSN: 0006-8993
    E-ISSN: 1872-6240
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  • 5
    Language: English
    In: Brain Research, 1999, Vol.825(1), pp.180-182
    Description: The present study examined the effects of repeated exposure to amphetamine on GABA sub(A) receptor binding in cortical and subcortical areas. The goal of the study was to determine whether changes in specific binding were related to behavioral sensitization. Animals were exposed to either saline (0.3 ml, s.c.; n=12) or d -amphetamine (2.5 mg/kg, s.c.; n=12) for 6 consecutive days and sacrificed after a 14-day withdrawal period. Differences in GABA sub(A) receptor binding in these two groups of animals were assessed using the GABA sub(A) receptor antagonist [ super(3) H ]SR 95531. To verify that the preceding treatment regimen led to the development of behavioral sensitization, a separate set of animals (n=8/group) was exposed to the same regimen and challenged with d -amphetamine (2.5 mg/kg, s.c.) after the 14-day withdrawal period. As expected, preexposure to amphetamine led to the development of amphetamine sensitization. There were no differences in GABA sub(A) receptor binding in animals preexposed to saline and amphetamine in the prefrontal cortex, caudate-putamen, hypothalamus, or cerebellum. These findings do not provide support for the idea that changes in GABA sub(A) receptor binding in the medial prefrontal cortex or various subcortical areas are related to the development of behavioral sensitization.
    Keywords: Amphetamine ; Sensitization ; Gamma-Aminobutyric Acid ; Gaba A Receptor ; Locomotion ; Prefrontal Cortex ; Anatomy & Physiology
    ISSN: 0006-8993
    E-ISSN: 1872-6240
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  • 6
    Language: English
    In: Brain Research, 1995, Vol.684(1), pp.112-114
    Description: The present study was designed to examine the effects of chronic stress on GABA receptor binding. Animals were randomly assigned to either a control, acute, or chronic stress condition and changes in specific binding were assessed using the GABA receptor antagonist [ H]SR 95531. Exposure to chronic restraint stress led to a significant reduction in GABA receptor binding in the prefrontal cortex. Alterations in specific binding were not observed in the cerebellum, caudate-putamen, hippocampus, or cingulate cortex however, suggesting that the effects of chronic stress may be regionally specific. Exposure to acute restraint did not lead to a significant alteration in [ H]SR 95531 binding in any brain region examined.
    Keywords: Stress ; Gaba A Receptor ; Prefrontal Cortex ; Sr 95531 ; Restraint ; Anatomy & Physiology
    ISSN: 0006-8993
    E-ISSN: 1872-6240
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  • 7
    Language: English
    In: Brain Research, 04 June 1990, Vol.518(1-2), pp.55-60
    Description: Microdialysis and in vivo voltammetry combined K -selective microelectrodes were utilized to study the effect of -glutamate (GLU) on the in vivo release of dopamine (DA) from the rat striatum. Perfusion of 500 nM–5mM GLU through the microdialysis probe was without an effect on DA outflow whereas 10 mM GLU resulted in a significant (295%) increase in the basal level of DA. This increase was blocked in the presence of 2-amino-5-phosphonopentanoic acid, an (NMDA) receptor antagonist. Repetitive local applications of 10 mM GLU were also required to observe an increase in extracellular DA measured by in vivo voltammetry. These signals were accompanied with a massive increase in extracellular K and a large negative shift in the field potential resembling the ionic changes seen after the phenomenon spreading depression. These studies suggest that high concentrations of GLU are required to enhance the extracellular concentration of DA in vivo. Further, pathophysiological conditions such as spreading depression may be responsible for the observed increase in extracellular DA concentration.
    Keywords: Dopamine ; Glutamate ; Striatum ; N-Methyl-D-Aspartate Receptor ; Microdialysis ; In Vivo Voltammetry ; Potassium ; Anatomy & Physiology
    ISSN: 0006-8993
    E-ISSN: 1872-6240
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