Age and gender differences in spatial perspective taking.

Background And Aims: It is often necessary in daily experience to change one's point of view to adopt mentally the spatial perspective of other persons, learn the position of different objects in a new environment or even describe an environment to other persons. Hence, the ability to link spatial information from different perspectives seems to be necessary to orient ourselves in the space. Several studies have found gender-related differences in spatial reasoning in younger adults, but little is known about such effects in middle-aged and older adults.

A virtual-based task to assess place avoidance in humans.

Spatial memory can be assessed by virtual reality-based tasks, some of them similar to those previously used in rodents. In this study a virtual place avoidance task was developed based on a rodent labyrinth to evaluate human spatial memory. The task required subjects to avoid in a virtual room a prohibited zone defined solely by distal cues, while they collected rewards.

Reversal learning impairment and alterations in the prefrontal cortex and the hippocampus in a model of portosystemic hepatic encephalopathy.

Patients with liver dysfunction often suffer from hepatic encephalopathy (HE), a neurological complication that affects attention and memory. Various experimental animal models have been used to study HE, the most frequently used being the portocaval shunt (PCS). In order to determine brain substrates of cognitive impairment in this model, we assessed reversal learning and c-Fos expression in a rat model of portosystemic derivation.

Changes in cytochrome oxidase activity following spatial working memory learning in rats treated with tacrine.

We evaluated change in cytochrome oxidase (COx) activity of the hippocampus and related structures of the limbic system following spatial working memory learning in rats after treatment with tacrine (8.0mg/kg). Control groups treated with saline and tacrine and an untreated group were added.

Memory performance and scopolamine: hypoactivity of the thalamus revealed by cytochrome oxidase histochemistry.

Spatial memory learning is related to the functioning of a neuronal circuit composed of cortical, hippocampal and diencephalic brain regions. The Morris water maze (MWM) is frequently used to assess spatial memory in rats. In this study, the neuronal functional activity of some brain limbic system regions after a memory task in adult male Wistar rats injected with scopolamine (1.

Acetylcholinesterase activity in an experimental rat model of Type C hepatic encephalopathy.

Patients with liver malfunction often suffer from hepatic encephalopathy, a neurological complication which can affect attention and cognition. Diverse experimental models have been used to study brain alterations that may be responsible for hepatic encephalopathy symptoms. The aim of the study was to determine whether cognitive impairment found in cirrhosis could be due to disturbance of acetylcholinesterase activity.

The value of microsurgery in liver research.

The use of an operating microscope in rat liver surgery makes it possible to obtain new experimental models and improve the already existing macrosurgical models. Thus, microsurgery could be a very valuable technique to improve experimental models of hepatic insufficiency. In the current review, we present the microsurgical techniques most frequently used in the rat, such as the portacaval shunt, the extrahepatic biliary tract resection, partial and total hepatectomies and heterotopic and orthotopic liver transplantation.

Sexually dimorphic c-Fos expression following spatial working memory in young and adult rats.

The sex differences in the functional contribution of brain substrates were explored following acquisition of a spatial working memory task using quantification of c-Fos protein. Rats of both sexes were trained during adolescence and adulthood in Morris water maze using a hidden escape platform with different daily location. Two control groups for each sex and age were added to explore the c-Fos activation not specific to the memory process.

Spatial working memory learning in young male and female rats: involvement of different limbic system regions revealed by cytochrome oxidase activity.

Sex differences have been found in the spatial memory which involve several regions of the limbic system. The Morris water maze (MWM) is one of the most widely used tasks in behavioral neuroscience to explore spatial and episodic memory in rats. We evaluated the oxidative metabolic activity of the prefrontal cortex, dorsal hippocampus, anterior thalamic nuclei and mammillary region following the acquisition of a spatial working memory (WM) task in young rats (30 days) of both sexes using quantitative histochemistry of the cytochrome oxidase (COx).

Spatial working memory in Wistar rats: brain sex differences in metabolic activity.

Several works have shown that males and females differ in the ability to learn spatial locations in mazes. In this study, we used the Morris water maze to assess the acquisition of a spatial working memory (WM) task in adult male and female Wistar rats. The task consisted of a paired sample procedure made up of two daily identical trials, sample and retention.

Hippocampal heterogeneity in spatial memory revealed by cytochrome oxidase.

The oxidative metabolism was assessed in the septal, intermediate and temporal hippocampus in Wistar rats that were trained following a working memory schedule in the Morris water maze. The cytochrome oxidase histochemistry was measured at 90 min, 6, 24 and 48 h post-training. We found an increase in the septal dentate gyrus at 90 min, at 6h the increase was also found in CA3 and CA1 regions and returned to basal levels at 24h.

Associative learning deficit in two experimental models of hepatic encephalopathy.

People with hepatic insufficiency can develop hepatic encephalopathy (HE), a complex neuropsychological syndrome covering a wide range of neurological and cognitive and motor alterations. The cognitive deficits include disturbances in intellectual functions such as memory and learning. In spite of its high prevalence in western societies, the causes of HE have not yet been clearly established.

Basal and learning task-related brain oxidative metabolism in cirrhotic rats.

Hepatic encephalopathy is a neurological complication observed in patients with liver disease. Subjects with hepatic encephalopathy can develop memory alterations. In order to investigate brain oxidative metabolism in an animal model of chronic cirrhosis and its modification after spatial working memory task, we determined the neural metabolic activity of several brain limbic system regions by cytochrome oxidase (COx) histochemistry and assessed the spatial working memory in the Morris water maze of rats with cirrhosis by administration of thioacetamide.

Mammillary body alterations and spatial memory impairment in Wistar rats with thioacetamide-induced cirrhosis.

Brain tissue of patients diagnosed with hepatic encephalopathy exhibits cellular morphological changes that could be associated with memory impairment. The mammillary nuclei, located in the posterior part of the hypothalamus, are important for spatial memory formation. This work aimed to assess spatial reference memory and cellular changes in the mammillary nuclei of cirrhotic rats.

Working memory impairment and reduced hippocampal and prefrontal cortex c-Fos expression in a rat model of cirrhosis.

Hepatic encephalopathy (HE) is a frequent neurological complication observed in patients with liver malfunction. Previous studies have shown memory impairment in these patients. In order to investigate brain substrates of spatial working memory impairment in chronic HE, neuronal expression of c-Fos protein was studied in an experimental model of cirrhosis.

Bilateral and unilateral hippocampal inactivation did not differ in their effect on consolidation processes in the Morris water maze.

Consolidation processes were studied in the rat by using functional inactivation techniques. Previous results showed that unilateral hippocampal inactivation alters consolidation. It is not clear if bilateral treatments increase the impairment.

Spatial memory alterations in three models of hepatic encephalopathy.

A behavioural evaluation was carried out on three chronic models of hepatic encephalopathy: two models of type B HE, portacaval shunt (PCS) and portal hypertension (PH) and one of type C HE with cirrhosis and portal hypertension from thioacetamide intoxication (TAA). The tasks selected cover a wide range of behaviours related to: locomotion (rotarod-accelerod test), anxiety (open field and elevated plus maze) and memory (Morris water maze). The results indicate that neither locomotor activity nor anxiety was affected in our models, in comparison with their respective controls.

Partial portal vein ligation plus thioacetamide: a method to obtain a new model of cirrhosis and chronic portal hypertension in the rat.

To obtain a new model of chronic portal hypertension in the rat, two classical methods to produce portal hypertension, partial portal vein ligation and the oral administration of thioacetamide (TAA), have been combined. Male Wistar rats were divided into four groups: 1 (control; n = 10), 2 [triple partial portal vein ligation (TPVL); n = 9], 3 (TAA; n = 11), and 4 (TPVL plus TAA; n = 9). After 3 months, portal pressure, types of portosystemic collateral circulation, laboratory hepatic function tests (aspartate aminotransferase, alanine aminotransferase, bilirubin, alkaline phosphatase, and gamma-glutamyl transpeptidase) and liver histology were studied.

Prehepatic portal hypertension induces alterations in cytochrome oxidase activity in the rat adrenal gland.

One approach to assess neuroendocrine response to portal hypertension in short-term portal vein-stenosed rats consists in studying metabolic and functional activity patterns in adrenal glands using mitochondrial enzyme cytochrome c oxidase (COX) as a histochemical marker. Male Wistar rats were divided into two groups: a control group (Group I; n = 8), in which the animals did not undergo any operative intervention, and a triple calibrated portal vein stenosis group (TPVS) (Group II; n = 7). The sections of suprarenal glands were histochemically stained for COX and the optical densitometry was measured by a computer image analyzer attached to a microscope.

Increased cytochrome oxidase activity in adrenal glands of thioacetamide-cirrhotic rats.

Objectives: Cytochrome oxidase activity has been determined in the adrenal glands of thioacetamide (TAA)-cirrhotic rats.

Material And Methods: Two groups of animals (Control group; n=10 and TAA group; n=11) of three months evolution were used to study the cytochrome oxidase activity in the suprarenal cortex (glomerular, fascicular and reticular layers) and medulla. TAA was administered orally and cytochrome oxidase (COX) activity was assayed by an immunohistochemical technique.

Partial unilateral inactivation of the dorsal hippocampus impairs spatial memory in the MWM.

The hippocampus is one of the more widely studied structures related with spatial memory. In this study, we assessed the effect of unilateral inactivation of the dorsal hippocampus with tetrodotoxin (TTX) on the performance displayed by Wistar rats in the spatial version of the Morris water maze. In experiment 1, we injected into the dorsal hippocampus in two different groups of rats 1 microl of saline solution or 5 ng of TTX in 1 microl of saline each day immediately after the training during four consecutive days.

Quantitative changes in neuronal and glial cells in the suprachiasmatic nucleus as a function of the lighting conditions during weaning.

To examine whether lighting conditions during the development of the rat circadian system affect the morphology of the suprachiasmatic nucleus (SCN), three groups of rats were born and maintained until they were 24 days old under constant light (LL), constant darkness (DD) or 24-h light-dark cycles (LD, 12-h light and 12-h darkness). We applied a stereological method to study whether these conditions lead to alterations in the volume of the SCN and changes in the total number of neurons and glial cells. While lighting conditions did not induce differences in the SCN volume, the number of both neurons and glial cells did differ between groups.

Effects of Pavlovian fear conditioning on septohippocampal metabolism in rats.

The effects of classical fear conditioning in different regions of the limbic system were analysed using cytochrome oxidase (CO) histochemistry. Wistar rats were submitted to different conditions. Rats in the group Paired received tone-shock pairing, to elicit conditioned suppression of lever pressing (i.

Diurnal locomotor activity and oxidative metabolism of the suprachiasmatic nucleus in two models of hepatic insufficiency.

Subjects with hepatic cirrhosis develop alterations of several rhythmic behavioural and biochemical patterns. Since most cirrhotic patients combine portal hypertension and hepatic impairment, our work aims to assess the extent to which rhythmical changes can be due to hepatic insufficiency or portal hypertension. This was done using two experimental models in rats, portacaval shunt model (PC) and portal hypertension by a triple stenosing ligature of the portal vein (PH).

Cognitive deficits in patients with hepatic cirrhosis and in liver transplant recipients.

This study assessed cognitive deficit in patients diagnosed with different stages of hepatic cirrhosis and in liver transplant recipients. A short protocol consisting of several psychometric tests was used. Cirrhotic patients showed a degree of mental impairment in all the functions studied.