| 1. |
- Deshpande, J, et al.
(author)
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Ultrastructural changes in the hippocampal CA1 region following transient cerebral ischemia: evidence against programmed cell death.
- 1992
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In: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale. - 0014-4819. ; 88:1, s. 91-105
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Journal article (peer-reviewed)abstract
- The ultrastructural changes in the pyramidal neurons of the CA1 region of the hippocampus were studied 6 h, 24 h, 48 h, and 72 h following a transient 10 min period of cerebral ischemia induced by common carotid occlusion combined with hypotension. The pyramidal neurons showed delayed neuronal death (DND), i.e. at 24 h and 48 h postischemia few structural alterations were noted in the light microscope, while at 72 h extensive neuronal degeneration was apparent. The most prominent early ultrastructural changes were polysome disaggregation, and the appearance of electron-dense fluffy dark material associated with tubular saccules. Mitochondria and nuclear elements appeared intact until frank neuronal degeneration. The dark material accumulated with extended periods of recirculation in soma and in the main trunks of proximal dendrites, often beneath the plasma membrane, less frequently in the distal dendrites and seldom in spines. Protein synthesis inhibitors (anisomycin, cycloheximide) and an RNA synthesis inhibitor (actinomycin D), administered by intrahippocampal injections or subcutaneously, did not mitigate neuronal damage. Therefore, DND is probably not apoptosis or a form of programmed cell death. We propose that the dark material accumulating in the postischemic period represents protein complexes, possibly aggregates of proteins or internalized plasma membrane fragments, which may disrupt vital cellular structure and functions, leading to cell death.
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| 2. |
- Lindeberg, Tony, 1964-, et al.
(author)
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Analysis of brain activation patterns using a 3-D scale-space primal sketch
- 1999
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In: Human Brain Mapping. - 1065-9471 .- 1097-0193. ; 7:3, s. 166-94
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Journal article (peer-reviewed)abstract
- A fundamental problem in brain imaging concerns how to define functional areas consisting of neurons that are activated together as populations. We propose that this issue can be ideally addressed by a computer vision tool referred to as the scale-space primal sketch. This concept has the attractive properties that it allows for automatic and simultaneous extraction of the spatial extent and the significance of regions with locally high activity. In addition, a hierarchical nested tree structure of activated regions and subregions is obtained. The subject in this article is to show how the scale-space primal sketch can be used for automatic determination of the spatial extent and the significance of rCBF changes. Experiments show the result of applying this approach to functional PET data, including a preliminary comparison with two more traditional clustering techniques. Compared to previous approaches, the method overcomes the limitations of performing the analysis at a single scale or assuming specific models of the data.
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| 3. |
- Åkerman, S., et al.
(author)
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Surface Model Generation and Segmentation of the Human Celebral Cortex for the Construction of Unfolded Cortical Maps
- 1996
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In: Proc. 2nd International Conference on Functional Mapping of the Human Brain. ; , s. S126-S126
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Conference paper (peer-reviewed)abstract
- Representing the shape of the human cerebral cortex arises as a basic subproblem in several areas of brain science, such as when describing the anatomy of the cortex and when relating functional measurements to cortical regions. Most current methods for building such representions of the cortical surface are either based on contours from two-dimensional cross sections or landmarks that have been obtained manually.In this article, we outline a methodology for semi-automatic contruction of a solely surface based representation of the human cerebral cortex in vivo for subsequent generation of (unfolded) two-dimensional brain maps.The method is based on input data in the form of three-dimensional NMR images, and comprises the following main steps:suppression of disturbing fine-scale structures by linear and non-linear scale-space techniques,generation of a triangulated surface representation based on either iso-surfaces or three-dimensional edge detection,division of the surface model into smaller segments based on differential invariants computed from the image data.When constructing an unfolded (flattened) surface representation, the instrinsic curvature of the cortex means that such a unfolding cannot be done without introducing distortions. To reduce this problem, we propose to cut the surface into smaller parts, where a ridge detector acts as guideline, and then unfold each patch individually, so as to obtain low distortions.Having a solely surface based representation of the cortex and expressing the image operations using multi-scale differential invariants in terms of scale-space derivatives as done in this work is a natural choice both in terms of conceptual and algorithmic simplicity. Moreover, explicitly handling the multi-scale nature of the data is necessary to obtain robust results.
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| 4. |
- Bentzer, Peter, et al.
(author)
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Supersensitivity in rat micro-arteries after short-term denervation
- 1997
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In: Acta Physiologica Scandinavica. - 0001-6772. ; 161:2, s. 125-133
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Journal article (peer-reviewed)abstract
- Contractile responses to phenylephrine and high-K+ were investigated in vitro in microvascular preparations from the rat medial plantar artery, a branch from the saphenous artery, obtained after short-term denervation in vivo. Two groups of animals were studied: (1) animals undergoing surgical resection of the saphenous nerve, and (2) animals undergoing surgical resection of both the sciatic and saphenous nerves. The animals were operated on one side only. Microvascular preparations (diameter about 325 microns) were obtained 10 days after surgery. Vessels from the non-operated side served as controls. Immunocytochemistry showed a decreased number of both neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) immunoreactive nerve fibres in vessels after resection of the saphenous nerve only. Resection of both the saphenous and the sciatic nerve caused a complete loss of immunoreactive nerve fibres. Mechanical measurements were performed using a wire myograph. In vessels subjected to resection of the saphenous nerve the sensitivity to phenylephrine was similar to controls. Vessels denervated by resection of both the saphenous and sciatic nerves showed significant increases in phenylephrine and potassium sensitivity. When depolarized in high-K+ solution the denervated vessels showed an increased sensitivity to extracellular Ca2+. The results show that complete short-term denervation of the rat medial plantar artery in vivo causes a pronounced supersensitivity in the vascular smooth muscle. The supersensitivity appears not to be restricted to the sympathetic alpha-receptors but also associated with changes in the cellular excitation-contraction coupling. Such altered reactivity of the vascular smooth muscle may contribute to vascular disturbances observed in vivo after nerve damage or surgical denervation.
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| 5. |
- Malmgren, Helge, 1945
(author)
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Perceptual expectations and the learning of temporal sequences.
- 1996
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In: Philosophical Communications, Red Series. - 0347-5794. ; :35
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Journal article (other academic/artistic)abstract
- The paper starts with an overview of some central unsolved problems of intentionality. Partly basing my argument on an analysis of how the heard temporal Gestalt develops during the listenting to a musical phrase, I then present my model of mental simulation and associative learning through "natural resonance" in considerable detail.
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| 6. |
- Johansson, C, et al.
(author)
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Nitric oxide synthase inhibition blocks phencyclidine-induced behavioural effects on prepulse inhibition and locomotor activity in the rat.
- 1997
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In: Psychopharmacology. - 0033-3158. ; 131:2, s. 167-73
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Journal article (peer-reviewed)abstract
- The ability of the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), to block the behavioural effects of the potent psychotomimetic, phencyclidine, was tested in rats using two different behavioural models. L-NAME was found to block both phencyclidine-induced disruption of prepulse inhibition of acoustic startle and phencyclidine-induced stimulation of locomotor activity. A selective action of L-NAME on the effects of phencyclidine was indicated, since L-NAME did not alter the effects of amphetamine, another potent psychotomimetic, in these behavioural models. These observations suggest that a nitric oxide-dependent mechanism may be involved in the effects of phencyclidine in the central nervous system.
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| 7. |
- Zhang, Jianhua, 1961, et al.
(author)
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Repeated administration of amphetamine induces sensitisation to its disruptive effect on prepulse inhibition in the rat.
- 1998
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In: Psychopharmacology. - 0033-3158. ; 135:4, s. 401-6
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Journal article (peer-reviewed)abstract
- Male Sprague-Dawley rats were repeatedly treated with amphetamine (AMP, 1 mg/kg, SC) at 3- day intervals for 15 days and tested for prepulse inhibition of acoustic startle after each treatment. This treatment regimen induced sensitisation in the animals as evidenced by a progressive increase in the disruptive effect of AMP on prepulse inhibition. Persistent changes in brain function was indicated, since an increase in disruptive effect was observed in sensitised animals also after a 22-day-long drug- and test-free period. The development of sensitisation was blocked by pretreatment with haloperidol (HPD, 0.1 mg/kg, SC), which suggests that sensitisation to the disruptive effect of AMP was dependent on dopamine (DA) D2 receptor activation. Furthermore, the development of sensitisation was blocked by adrenalectomy, which suggests that sensitisation was dependent also on circulating adrenal hormones. Increased DA-ergic activity has been implicated in the pathophysiology of schizophrenia and AMP-induced sensitisation to the neuronal functions that modulate prepulse inhibition may be an experimental model to investigate this hypothesis.
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| 8. |
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| 9. |
- Lindeberg, Tony, 1964-, et al.
(author)
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Foveal scale-space and the linear increase of receptive field size as a function of eccentricity
- 1994
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Reports (other academic/artistic)abstract
- This paper addresses the formulation of a foveal scale-space and its relation to the scaling property of receptive field sizes with eccentricity. It is shown how the notion of a fovea can be incorporated into conventional scale-space theory leading to a foveal log-polar scale-space. Natural assumptions about uniform treatment of structures over scales and finite processing capacity imply a linear increase of minimum receptive field size as a function of eccentricity. These assumptions are similar to the ones used for deriving linear scale-space theory and the Gaussian receptive field model for an idealized visual front-end.
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