Papers by Kazuyuki Imamura
Journal of Motor Behavior, Apr 7, 2022
In this study, we developed an evaluation method using image analysis for reaching tasks. Using t... more In this study, we developed an evaluation method using image analysis for reaching tasks. Using this method, we studied forearm function during the reaching task in rats that received a unilateral injection of 6-OHDA into the striatum. The success ratio of the reaching task reduced to 40.5% seven days after the injection. In addition, significant changes were observed in the pronation angle of the forearm, posture control, and targeting (i.e., the distance between all fingertips and the center of the target pellet). Thus, unilateral injection of 6-OHDA reduces dopaminergic function in the brain and causes deterioration of forearm function and posture control in the reaching task.
Springer eBooks, 2003
How the functional maps develop during the critical period of the visual cortex is one of the maj... more How the functional maps develop during the critical period of the visual cortex is one of the major questions that have challenged many experimental and theoretical investigators. Although it is accepted that visual experience contributes to the maturation of ocular dominance and orientation maps, how and to what extent visual experience affects map formation has not been fully elucidated yet. Blakemore and Cooper [1] have reported that neurons in area 17 exhibited orientation polar histograms strongly biased to the experienced orientation in cats that had been exposed to only vertical or horizontal stripes in a cylindrical room for several hours a day during development. Although such a strong bias of preferred orientations could not be reproduced by other groups following almost the same experimental protocol [2, 3], many investigators were motivated to investigate the role of visual experience for orientation map formation. Recently, Sengpiel et al. [4] have shown by intrinsic optical recording that the basic structure of orientation maps is rather robust even when the experienced orientation is slightly overrepresented in the visual cortex. It is thought that the discrepancy between the results is partly due to the difficulty in achieving perfect restriction of stimulus orientations for a long time. In this study, we mounted chronically special goggles made of cylindrical lenses on kittens to restrict their exposure to a single orientation during development. Only vertically elongated images of the environment could be seen through the goggles. We recorded intrinsic optical signals from the visual cortex of these kittens, and demonstrated that vertical orientation was strongly overrepresented in all the animals examined. The degree of overrepresentation for the goggles-mounted kittens was much stronger than that for a kitten exposed to vertical stripes inside a cylindrical room.
Neuroscience Research, 2000
Information Fusion, Nov 1, 2021
Lecture Notes in Computer Science, 2016
To find out the influences on the emotionality and attentional deployment caused by depression, w... more To find out the influences on the emotionality and attentional deployment caused by depression, we recruited 19 MDD patients and 19 healthy controls, and implemented a task-state fMRI experiment using a distraction task paradigm. Our results showed relatively decreased brain activation in the right precuneus and left DLPFC, in the MDD group compared with the healthy group across the positive, neutral, and negative task conditions. During only the positive condition, decreased subcortical responses and concurrently reduced brain activation in the salience network were found only in MDD patients. Further brain-symptom analysis demonstrated significant correlation between alterations in the key region of the salience network and the depressive severity of the patients. Our findings suggest a crucial role of aberrant salience processes (especially in the anterior insulae) in the abnormal perception of positive stimuli in MDD patients, which is likely to be the underlying pathology of the anhedonia.
Lecture Notes in Computer Science, 2015
Background: Previous studies have demonstrated that structural deficits and functional connectivi... more Background: Previous studies have demonstrated that structural deficits and functional connectivity imbalances might underlie the pathophysiology of obsessive-compulsive disorder (OCD). The purpose of the present study was to investigate gray matter deficits and abnormal resting-state networks in patients with OCD and further investigate the association between the anatomic and functional alterations and clinical symptoms. Methods: Participants were 33 treatment-naïve OCD patients and 33 matched healthy controls. Voxel-based morphometry was used to investigate the regions with gray matter abnormalities and resting-state functional connectivity analysis was further conducted between each gray matter abnormal region and the remaining voxels in the brain. Results: Compared with healthy controls, patients with OCD showed significantly increased gray matter volume in the left caudate, left thalamus, and posterior cingulate cortex, as well as decreased gray matter volume in the bilateral medial orbitofrontal cortex, left anterior cingulate cortex, and left inferior frontal gyrus. By using the above morphologic deficits areas as seed regions, functional connectivity analysis found abnormal functional integration in the cortical-striatum-thalamic-cortical (CSTC) circuits and default mode network. Subsequent correlation analyses revealed that morphologic deficits in the left thalamus and increased functional connectivity within the CSTC circuits positively correlated with the total Y-BOCS score. Conclusion: This study provides evidence that morphologic and functional alterations are seen in CSTC circuits and default mode network in treatment-naïve OCD patients. The association between symptom severity and the CSTC circuits suggests that anatomic and functional alterations in CSTC circuits are especially important in the pathophysiology of OCD.
Journal of comparative neurology, Sep 8, 2020
Ocular dominance plasticity (ODP) is a type of cortical plasticity operating in visual cortex of ... more Ocular dominance plasticity (ODP) is a type of cortical plasticity operating in visual cortex of mammals that are endowed with binocular vision based on the competition-driven disparity. Earlier, a molecular mechanism was proposed that catecholamines play an important role in the maintenance of ODP in kittens. Having survived the initial test, the hypothesis was further advanced to identify noradrenaline (NA) as a key factor that regulates ODP in the immature cortex. Later, the ODP-promoting effect of NA is extended to the adult with age-related limitations. Following the enhanced NA availability, the chain events downstream lead to the βadrenoreceptor-induced cAMP accumulation, which in turn activates the protein kinase A. Eventually, the protein kinase translocates to the cell nucleus to activate cAMP responsive element binding protein (CREB). CREB is a cellular transcription factor that controls the transcription of various genes, underpinning neuronal plasticity and long-term memory. In the advent of molecular genetics in that various types of new tools have become available with relative ease, ODP research has lightly adopted in the rodent model the original concepts and methodologies. Here, after briefly tracing the strategic maturation of our quest, the review moves to the later development of the field, with the emphasis placed around the following issues: 1) Are we testing ODP per se? 2) What does monocular deprivation deprive of the immature cortex? 3) The critical importance of binocular competition, 4) What is the adult plasticity? 5) Excitation-Inhibition balance in local circuits, and 6) Species differences in the animal models.
Journal of Physiological Sciences, 2016
Activation to Acquisition, 1991
Sensory cortex is a part of various ascending fiber projection systems, each of which originates ... more Sensory cortex is a part of various ascending fiber projection systems, each of which originates from a relatively small number of chemically identified cells in the basal forebrain, brainstem or medulla. Catecholamine (CA) histochemistry, invented by the Swedish school in the early 1960’s, indeed opened up a new possibility of identifying each neuron based on its chemical signature or transmitter phenotype. The recent advent in development of specific immunological probes has further led to the explosion of detailed cytochemical mapping on the ascending fiber projection systems. Noradrenaline (NA) fibers, originating from the locus coeruleus (LC) in the dorsal tegmentum, mesocortical dopamine (DA) fibers from the mesencephalon, serotonin (5-HT) fibers from the raphe groups in the pons, and the basal forebrain acetylcholine (ACh) system, are among the best characterized ascending projection systems. They consist of slow-conducting, non-myelinated or poorly myelinated axons.
Proceedings of Annual Meeting of the Physiological Society of Japan Proceedings of Annual Meeting of the Physiological Society of Japan, 2004
Advances in Behavioral Biology, 1990
Journal of Integrative Neuroscience, 2021
The rat reaching task is one of the best paradigms from behavioral study of upper limb movements.... more The rat reaching task is one of the best paradigms from behavioral study of upper limb movements. Rats are trained to reach and grab a pellet by extending their hand through a vertical slit. A few conventional imaging systems specific for the rat reaching task are commercially available with a high installation cost. Based on image analysis of video recordings obtained during the reaching task, we, herewith, developed a new, low-cost laboratory system that can be used for the quantitative analysis of ten basic forearm movements, in contrast to subjective assessments used in previous studies. We quantified images of the pronated and supinated palm and the accuracy and speed of reaching the target. Applying this newly developed method, we compared the forearm movements during the reaching task before and after a massive anatomical lesion of the sensorimotor cortex performed by tissue aspiration. We also wanted to investigate the recovery of upper limb function possibly induced by repeating the task for a relatively short term of a few weeks. In the experiment, 7 injured groups and 3 control groups were used. We found characteristic abnormalities of the forearm movements and a significant recovery in the success rate of grasping the target pellet. The present results demonstrate that our method is straightforward for the quantitative evaluation of forearm movements during the reaching task primarily controlled by the sensorimotor cortex.
The Keio Journal of Medicine, 2002
How the functional maps develop during the critical period of the visual cortex is one of the maj... more How the functional maps develop during the critical period of the visual cortex is one of the major questions that have challenged many experimental and theoretical investigators. Although it is accepted that visual experience contributes to the maturation of ocular dominance and orientation maps, how and to what extent visual experience affects map formation has not been fully elucidated yet. Blakemore and Cooper [1] have reported that neurons in area 17 exhibited orientation polar histograms strongly biased to the experienced orientation in cats that had been exposed to only vertical or horizontal stripes in a cylindrical room for several hours a day during development. Although such a strong bias of preferred orientations could not be reproduced by other groups following almost the same experimental protocol [2, 3], many investigators were motivated to investigate the role of visual experience for orientation map formation. Recently, Sengpiel et al. [4] have shown by intrinsic optical recording that the basic structure of orientation maps is rather robust even when the experienced orientation is slightly overrepresented in the visual cortex. It is thought that the discrepancy between the results is partly due to the difficulty in achieving perfect restriction of stimulus orientations for a long time. In this study, we mounted chronically special goggles made of cylindrical lenses on kittens to restrict their exposure to a single orientation during development. Only vertically elongated images of the environment could be seen through the goggles. We recorded intrinsic optical signals from the visual cortex of these kittens, and demonstrated that vertical orientation was strongly overrepresented in all the animals examined. The degree of overrepresentation for the goggles-mounted kittens was much stronger than that for a kitten exposed to vertical stripes inside a cylindrical room.
Neuroscience Research Supplements, 1989
PLoS ONE, 2012
We examined lateral geniculate nucleus (LGN) degeneration as an indicator for possible diagnosis ... more We examined lateral geniculate nucleus (LGN) degeneration as an indicator for possible diagnosis of glaucoma in experimental glaucoma monkeys using positron emission tomography (PET). Chronic intraocular pressure (IOP) elevation was induced by laser trabeculoplasty in the left eyes of 5 cynomolgus monkeys. Glial cell activation was detected by PET imaging with [ 11 C]PK11195, a PET ligand for peripheral-type benzodiazepine receptor (PBR), before and at 4 weeks after laser treatment (moderate glaucoma stage). At mild, moderate, and advanced experimental glaucoma stages (classified by histological changes based on the extent of axonal loss), brains were stained with cresyl violet, or antibodies against PBR, Iba-1 (a microglial marker), and GFAP (an activated astrocyte marker). In laser-treated eyes, IOP was persistently elevated throughout all observation periods. PET imaging showed increased [ 11 C]PK11195 binding potential in the bilateral LGN at 4 weeks after laser treatment; the increase in the ipsilateral LGN was statistically significant (P,0.05, n = 4). Immunostaining showed bilateral activations of microglia and astrocytes in LGN layers receiving input from the laser-treated eye. PBRpositive cells were observed in LGN layers receiving input from laser-treated eye at all experimental glaucoma stages including the mild glaucoma stage and their localization coincided with Iba-1 positive microglia and GFAP-positive astrocytes. These data suggest that glial activation occurs in the LGN at a mild glaucoma stage, and that the LGN degeneration could be detected by a PET imaging with [ 11 C]PK11195 during the moderate experimental glaucoma stage after unilateral ocular hypertension. Therefore, activated glial markers such as PBR in the LGN may be useful in noninvasive molecular imaging for diagnosis of glaucoma.
Neurobiology of Aging, 2000
The Japanese Journal of Physiology, 1984
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Papers by Kazuyuki Imamura