Browsing by Author "Aboitiz, F"

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    A new sign of callosal disconnection syndrome
    (2002) Lavados, M; Carrasco, X; Peña, M; Zaidel, E; Zaidel, D; Aboitiz, F
    We report a patient with callosal haemorrhage and no extracallosal involvement who developed a unique form of intermanual conflict. In the acute phase the patient showed a mild speech disturbance and right hemiparesis, and in her right hand, a grasp reflex and compulsive manipulation of tools, all attributable to transient frontal involvement. In the chronic phase there was intermanual conflict occasionally associated with the sensation of a second left hand. The patient also presented a sign consisting of compulsive, automatic execution of orders by one hand (the left or the right) when the patient was specifically asked to perform the movement with the other hand (the right or the left, respectively). There was no left-right confusion in this patient. We call this condition agonistic dyspraxia. In contrast with diagonistic dyspraxia, this consists of the agonistic behaviour of the other hand under conditions in which the hand that has been instructed to respond cannot execute the request.
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    AChE-rich magnopyramidal neurons have a left-right size asymmetry in Broca's area
    (ELSEVIER SCIENCE BV, 2004) Garcia, RR; Montiel, JF; Villalon, AU; Gatica, MA; Aboitiz, F
    Acetylcholinesterase-rich neurons (AChERN) are a particular group of pyramidal neurons, displaying a specific laminar and ontogenetic pattern in the cerebral cortex of human and nonhuman primates. Using histochemistry and morphometrical methods, we have found a layer 3 magnopyramidal AChERN left-right size asymmetry restricted to Brodmann's area 45, a component of Broca's language area. This structural feature could be related to functional lateralization associated to syntactic processing and phonological working memory, and is consistent with a non-cholinergic role of AChE possibly linked to neuroplastic processes in the human neocortex. (C) 2004 Elsevier B.V. All rights reserved.
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    Chronic stress impairs acoustic conditioning more than visual conditioning in rats: Morphological and behavioural evidence
    (PERGAMON-ELSEVIER SCIENCE LTD, 2005) Dagnino Subiabre, A; Terreros, G; Carmona Fontaine, C; Zepeda, R; Orellana, JA; Diaz Veliz, G; Mora, S; Aboitiz, F
    Chronic stress affects brain areas involved in learning and emotional responses. These alterations have been related with the development of cognitive deficits in major depression. The aim of this study was to determine the effect of chronic immobilization stress on the auditory and visual mesencephalic regions in the rat brain. We analyzed in Golgi preparations whether stress impairs the neuronal morphology of the inferior (auditory processing) and superior colliculi (visual processing). Afterward, we examined the effect of stress on acoustic and visual conditioning using an avoidance conditioning test. We found that stress induced dendritic atrophy in inferior colliculus neurons and did not affect neuronal morphology in the superior colliculus. Furthermore, stressed rats showed a stronger impairment in acoustic conditioning than in visual conditioning. Fifteen days post-stress the inferior colliculus neurons completely restored their dendritic structure, showing a high level of neural plasticity that is correlated with an improvement in acoustic learning. These results suggest that chronic stress has more deleterious effects in the subcortical auditory system than in the visual system and may affect the aversive system and fear-like behaviors. Our study opens a new approach to understand the pathophysiology of stress and stress-related disorders such as major depression. (c) 2005 Published by Elsevier Ltd on behalf of IBRO.
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    Dendritic morphology and orientation of pyramidal cells of the neocortex in two groups of early postnatal undernourished-rehabilitated rats
    (2003) Cordero, ME; Valenzuela, CY; Rodriguez, A; Aboitiz, F
    Postnatal undernutrition in animals and in humans leads to significant reduction in basal dendritic arborization of layer Vth pyramidal cells of the neocortex. Under the hypothesis that there are critical developmental periods for undernutrition to produce alterations in dendritic differentiation, we studied apical dendritic morphology and orientation of pyramidal cells from the deeper layers of the neocortex in rats undernourished until day 10 (UP10), until weaning (UP21) and in a control group (Q. Neurons were stained by the Golgi-Cox method. The main findings are: (i) an increased number of atypically oriented pyramids with apical dendrites extremely short in (UP10) and (UP21) groups and, (ii) the presence of classical pyramids with significantly longer apical dendrites in layers V and VI in (UP10) and (UP21) groups than in the control group (Q. We believe that undernutrition may disturb critically the early postnatal brain development by altering intrinsic factors and extracellular molecular signals that guide and regulate the apical dendritic growth of neocortex large pyramidal cells. (C) 2003 Elsevier Science B.V. All rights reserved.
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    Effect of psychostimulants on distinct attentional parameters in attentional deficit/hyperactivity disorder
    (SOC BIOLGIA CHILE, 2004) Lopez, J; Lopez, V; Rojas, D; Carrasco, X; Rothhammer, P; Garcia, R; Rothhammer, F; Aboitiz, F
    Although there is extensive literature about the effects of stimulants on sustained attention tasks in attentional deficit/hyperactivity disorder (ADHD), little is known about the effect of these drugs on other attentional tasks involving different neural systems. In this study we measured the effect of stimulants on ADHD children, both in the electroencephalographic (EEG) activity during sustained attentional tasks and in psychometric performance during selective attentional tasks. These tasks are known to rely on different cortical networks. Our results in children medicated with 10 mg of d-amphetamine administered 60 min before the study indicate (i) a significant increase in amplitude but not latency of the P300 component of the event-related potential (ERP) during the sustained attentional task and (ii) a significant improvement in the reaction times and correct responses in the selective attentional task. In addition to supporting the use of stimulants in children with attentional deficit/hyperactivity disorder, these results show a multifocal activity improvement of cortical structures linked to dopamine, and interestingly, to attention. All these analyses are framed in a wider study of diverse attentional functions in this syndrome.
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    Genotypic interaction between DRD4 and DAT1 loci is a high risk factor for attention-deficit/hyperactivity disorder in Chilean families
    (WILEY, 2006) Carrasco, X; Rothhammer, P; Moraga, M; Henriquez, H; Chakraborty, R; Aboitiz, F; Rothhammer, F
    Attention-deficit/hyperactivity disorder, ADHD [MIM 126452], is a common, highly heritable neurobiological disorder of childhood onset, characterized by hyperactivity, impulsiveness, and/or inattentiveness. As part of an ongoing study of AMID, we carried out a family-based discordant sib-pair analysis to detect possible associations between dopamine receptor D4 (DRD4) and dopamine transporter 1 (DAT1) polymorphisms and ADHD in Chilean families. Both loci individually classified as homozygotes or heterozygotes for the DRD4 7-repeat and DAT1 10-repeat alleles, did not exhibit genotype frequency differences between affected children and their healthy siblings (Fisher's exact test P > 0.25 in both cases). However, the simultaneous presence of both DRD4 7-repeat heterozygosity and DAT1 10 allele homozygosity were significantly higher (34.6%) in cases (26), compared with their unaffected siblings (25) (4%; Fisher's exact test P = 0.0096; odds-ratio, OR = 12.71). Increased density of dopamine transporter in ADHD brains, along with abundance of 7-repeat D4 receptors in prefrontal cortex, which is impaired in ADHD patients, make the observed gene-gene interaction worthy of further incisive studies. (C) 2005 Wiley-Liss, Inc.
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    Human-like rodent amyloid-β-peptide determines Alzheimer pathology in aged wild-type Octodon degu
    (2005) Inestrosa, NC; Reyes, AE; Chacón, MA; Cerpa, W; Villalón, A; Montiel, J; Merabachvili, G; Aldunate, R; Bozinovic, F; Aboitiz, F
    It is generally accepted that human Alzheimer's disease (AD) neuropathology markers are completely absent in rodent brains. We report here that an aged wild-type South American rodent, Octodon degu, expresses neuronal beta-amyloid precursor protein (beta-APP695) displaying both intracellular and extracellular deposits of amyloid-beta-peptide (A beta), intracellular accumulations of tau-protein and ubiquitin, a strong astrocytic response and acetylcholinesterase (AChE)-rich pyramidal neurons. The high amino acid homology (97.5%) between deguA beta and humanA beta sequences is probably a major factor in the appearance of AD markers in this aged rodent. Our results indicate that aged 0. degu constitutes the first wild-type rodent model for neurodegenerative processes associated to AD. (c) 2004 Elsevier Inc. All rights reserved.
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    Long distance communication in the human brain: timing constraints for inter-hemispheric synchrony and the origin of brain lateralization
    (SOCIEDAD BIOLGIA CHILE, 2003) Aboitiz, F; Lopez, J; Montiel, J
    Analysis of corpus callosum fiber composition reveals that inter-hemispheric transmission time may put constraints on the development of inter-hemispheric synchronic ensembles, especially in species with large brains like humans. In order to overcome this limitation, a subset of large-diameter callosal fibers are specialized for fast interhemispheric transmission, particularly in large-brained species. Nevertheless, the constraints on fast interhemispheric communication in large-brained species can somehow contribute to the development of ipsilateral, intrahemispheric networks, which might promote the development of brain lateralization.
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    The alien hand syndrome
    (2003) Aboitiz, F; Carrasco, X; Schröter, C; Zaidel, D; Zaidel, E; Lavados, M
    The term "alien hand" refers to a variety of clinical conditions whose common characteristic is the uncontrolled behavior or the feeling of strangeness of one extremity, most commonly the left hand. A common classification distinguishes between the posterior or sensory form of the alien hand, and the anterior or motor form of this condition. However, there are inconsistencies, such as the phenomenon of diagonistic dyspraxia, which is largely a motor syndrome despite being more frequently associated with posterior callosal lesions. We discuss critically the existing nomenclature and we also describe a case recently reported by us which does not fit any previously reported condition, termed agonistic dyspraxia. We propose that the cases of alien hand described in the literature can be classified into at least five broad categories: (i) diagonistic dyspraxia and related syndromes, (ii) alien hand, (iii) way-ward hand and related syndromes, (iv) supernumerary hands and (v) agonistic dyspraxia.
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    Williams syndrome: Pediatric, neurologic, and cognitive development
    (ELSEVIER SCIENCE INC, 2005) Carrasco, X; Castillo, S; Aravena, T; Rothhammer, P; Aboitiz, F
    This study examines the developmental history of 32 Williams syndrome patients, positive to the fluorescence in situ hybridization (FISH) test. The information is intended to provide help for early diagnosis and appropriate stimulation of these patients. In the sample reported here, only about half of the patients referred with presumptive diagnosis were in fact (FISH), indicating that facial dysmorphism may not be the most reliable sign for diagnosis. Initial pediatric signs are developmental delay and nocturnal irritability. In consultation, facial dysmorphies and heart murmur are detected. There is also low birth weight, failure to thrive, unsuccessful breastfeeding, and gastroesophageal reflux. All these symptoms are strongly suggestive of Williams syndrome. Subsequent steps consist of cardiologic studies. Our results indicate that the triad of symptoms consisting of infantile hypercalcemia, dysmorphic facies, and supravalvular aortic stenosis, which until recently was considered fundamental for Williams syndrome diagnosis, is not usually present and does not lead to an early diagnosis. Cognitively, these children are characterized by hypersociability, hyperacusia, deficient visuoconstructive abilities, attentional deficit and hyperactivity, and in some cases, spontaneous musical interests. There are no special verbal skills. The results of this study indicate that the concept of Williams syndrome patients as language-and musically-gifted is not fully accurate. (c) 2005 by Elsevier Inc. All rights reserved.