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At least 1,531 records · Page 85Linked to original sources
PubMed1988

Hormonal control of sleep-appetitive behaviour and diurnal activity rhythms in the cleaner wrasse Labroides dimidiatus (Labridae, Teleostei).

In its natural environment the cleaner wrasse, Labroides dimidiatus, possesses a hiding place in the reef, where it disappears every night. In my experiments, the Labroides was offered a specific sleeping cave in tanks. Photocells at the entrance to each cave, connected to a printer, counted the sleep-appetitive behaviour (SAB), viz. the investigation of the sleeping-place. Untreated animals visited the cave 45.6 times within 90 min prior to darkness. The swimming activity, which was measured 3 times daily, declined in the course of the light period. During the night the animals are totally motionless. Four substances which are involved in the sleep-influencing processes in mammals were tested. Injection of the neurotransmitter serotonin (0.05-0.5 micrograms/g b.wt. 5-HT) resulted in a decrease of swimming activity and SAB; the 5-HT blocking substance p-chlorophenylalanine (1-8 micrograms/g b.wt. PCPA) intensified this activity and suppressed SAB only in a concentration-range of 10 and 12 micrograms/g b.wt. In addition, the neuromodulatory properties of vasoactive intestinal polypeptide (VIP) and arginine vasotocin (AVT) were investigated. It is noteworthy to mention that VIP (1-1.5 micrograms/g b.wt.) lead to an remarkable increase, and AVT (0.5-4 micrograms/g b.wt.) to a significant reduction of the SAB.

Animals↗
PubMed1990

Radial maze performance following hippocampal kindling.

The relation between hippocampal epileptiform activity and 8-arm radial maze performance was assessed following repetitive afterdischarges (ADs) evoked by stimulation of the hippocampal CA1 region (kindling). Hippocampal kindling, whether to stage V (generalized) convulsions or to a preconvulsive stage, induced deficits in radial maze performance, evaluated by correct arm entries in 8 choices or total maze run (trial) time. The deficits persisted at least until 21 days after the last AD. Hippocampal interictal spikes (ISs) were induced by kindling, but the rate of ISs declined to near zero in a few days. The rate or presence of ISs was not related to maze performance.

Animals↗
PubMed1990

The role of the amygdala and the hippocampus in working memory for spatial and non-spatial information.

Male rats received either electrolytic or sham lesions bilaterally into the amygdala, hippocampus or amygdala plus hippocampus, or were assigned to an unoperated control group. After the postoperative recovery period all lesioned and control animals were tested for the ability to master a spatial delayed non-matching-to-sample (DNMS), a visual DNMS and a visuo-tactile DNMS. Retention of these paradigms was evaluated 24 h after the last respective training session. Bilateral lesions of the amygdala severely disrupted the acquisition and retention of a DNMS paradigm with visual and visuo-tactile cues as discriminative stimuli and had no effect on the acquisition and retention of a spatial DNMS. On the contrary, bilateral lesions of the hippocampus impaired the acquisition and retention of spatial DNMS, but the animals with these lesions showed an acquisition and retention of the visual and visuo-tactile DNMS paradigms significantly better than those of animals with amygdala lesions. Combined lesions of the amygdala and hippocampus severely disrupted the acquisition and retention of the 3 paradigms. The contribution of the amygdala and the hippocampus in the working memory for spatial and non-spatial information is discussed.

Amygdala↗
PubMed1990

Competition for sucrose-pellets in triads of male Wistar rats: disinhibitory effect of individual housing in poor-performing rats.

Within triads of male Wistar rats, some animals almost completely abstain from competition for palatable sucrose-pellets (so-called poor-performing rats). Individual housing temporarily helped these rats to behave more competitively. Such changes in the poor-performing rats' competition-scores are discussed in relation to previously described, isolation-induced alterations in serotonergic and noradrenergic neurotransmission.

Animals↗
PubMed1990

Inhibitory effects of cholecystokinin develop through interaction with duodenal signals.

I previously reported that cholecystokinin octapeptide (CCK-8) had little effect on feeding motivation as indexed by runway performance, but that substantial impairment resulted from the interaction of CCK-8 and prefeeding of sucrose. If the sucrose was sham-fed, potentiation of the effect of CCK-8 was seen only after large doses. The current experiments examined whether synergy between 1 microgram/kg CCK-8 and prefeeding could be reproduced using gastric, duodenal, or hepatic-portal infusions. Gastric and duodenal infusions of 30% sucrose were effective; in conjunction with CCK-8 they decreased running speed as substantially as prefeeding did. The duodenal effect was specific. Glucose appeared to be as effective as sucrose, whereas equi-osmotic saline and mannitol were not. Intraportal glucose was relatively ineffective; interaction with CCK-8 was seen only after very large infusions, and the resulting running speeds did not approach those seen after prefeeding or gastrointestinal infusions. These results suggest that decreased feeding motivation after 1 microgram/kg CCK-8 develops through synergy between this peptide and a carbohydrate-sensitive signal generated within the small intestine.

Animals↗
PubMed1990

Visual impairments in macaques following inferior temporal lesions are exacerbated selectively by additional damage to superior temporal sulcus.

The present study examined the behavioural effects of removing the inferior temporal cortex (area TE) either on its own or in combination with the adjacent fundus and upper bank of the superior temporal sulcus (area STP). Comparisons with preoperative behaviour showed that the addition of superior temporal sulcal damage led to an increase in visual components of the Klüver-Bucy syndrome, i.e. an increased tendency to touch and examine objects coupled with a decrease in emotional reactivity, but no excessive orality, changes in food preference, or coprophagia. No group differences were found in the learning of 3 pattern discriminations, but the animals with additional superior temporal sulcal lesions were more impaired than the others on 3 colour discriminations, successive reversals of an object discrimination, and a learning-set task. These findings indicate that STP provides an important route, independent of the route via TE, by which visual information can reach limbic structures to evoke affective responses and contribute to visual learning.

Amygdala↗
PubMed1990

Hippocampus and medial temporal cortex: neuronal activity related to behavioural responses during the performance of memory tasks by primates.

Neuronal activity was recorded in the hippocampal formation, the parahippocampal gyrus and medial inferotemporal cortex of monkeys performing memory tasks. In a modified delayed matching to sample task in which 2 sequentially presented stimuli were compared on each trial, a match condition required a right panel press, whereas a non-match condition required a left panel press. The activity of 336/736 (45.7%) neurons was related to the behavioural responses (left or right panel presses) in this task. The incidence of response-related activity was 57.4% in cortical areas adjacent to the rhinal sulcus plus medial inferotemporal cortex, and 40.2% for the hippocampal formation. For 58.9% of these response-related neurons, the activity change associated with the behavioural response was greater than that during presentation of the sensory stimuli, though neurons commonly responded (33.2% of all recorded neurons) to both sensory and motor events. The activity of 198 neurons (26.9%) differed between go-left and go-right trials; such neurons were found in all areas but were nearly twice as common in the posterior as in the anterior hippocampal formation. The importance of visual stimuli for the response-related neuronal activity was examined during the performance of a delayed alternation task without visual cues indicating direction of response. The response-related activity of 8 neurons recorded during the delayed alternation and the delayed matching tasks was similar in both tasks, indicating that memory for the behavioural responses influences the activity of the response-related neurons. In order to test the effects of stimulus familiarity and non-spatial responses on medial temporal neurons, recognition memory and visual discrimination tasks requiring lick responses were performed. The activity of 2/375 (0.5%) neurons was related to the lick responses; 3/68 neurons in the inferomedial temporal cortex responded on the basis of stimulus novelty and none reflected their reinforcement value. It is concluded that the hippocampal formation, the parahippocampal gyrus and medial inferotemporal cortex all have a role in the utilisation of sensory, mnemonic and motor information underlying the selection of spatially-directed behavioural responses.

Animals↗
PubMed1990

The structure of skilled forelimb reaching in the rat: a proximally driven movement with a single distal rotatory component.

The movements of rats trained to reach through an aperture for food pellets, located on a shelf, were videorecorded and filmed from lateral and ventral perspectives for analysis using Eshkol-Wachman Movement Notation (EWMN). Reaching was subdivided into phases of locating the food and advancing the limb to grasp the food, bringing the food to the mouth, and returning to the starting position. Further analysis of the movements comprising these acts revealed a number of novel findings. (1) Most of the first phase of the movement is produced proximally, with the limb lifted, aimed, and advanced from the shoulder. (2) After the limb is lifted from the substrate to initiate reaching, it is carried to a parasagittal position so that the long axis of the forearm is aligned along the midline of the body. This aspect of the movement 'aims' the limb toward the target. (3) The digits are opened as the limb is advanced from the aiming position toward the food. As the paw approaches the food, pronation of the palm is accomplished by abduction of the upper arm. (4) As the limb is retracted, the digits are closed to grasp the food. As retraction ends, the paw is supinated by a rotatory movement at the wrist. This is the only distal rotatory movement. (5) The position taken by the second forelimb, as it is adducted to aid in holding the food pellet for eating, resembles the 'aiming' posture. The results are discussed in reference to the kinematics, neural control, and the evolutionary origins of reaching in the rat and other animals. Additionally, the results provide a framework for analysis of changes in movements produced by physiological manipulations.

Animals↗
PubMed1990

6-Hydroxydopamine lesion of the rat prefrontal cortex increases locomotor activity, impairs acquisition of delayed alternation tasks, but does not affect uninterrupted tasks in the radial maze.

The role of mesocortical dopamine neurons in locomotion and acquisition of various delayed and uninterrupted maze tasks was investigated in the rat. Dopaminergic terminals of the medial prefrontal cortex were lesioned by stereotaxically guided injections of the selective neurotoxin 6-hydroxydopamine (6-OHDA), while noradrenergic neurons were protected by systemically administered desipramine. 6-OHDA lesions resulted in a selective depletion of dopamine and its metabolite, dihydroxyphenylacetic acid, in the prefrontal cortex but not in subcortical structures. Prefrontal serotonin was not depleted. 6-OHDA-cloned rats performed uninterrupted alternation tasks (spontaneous and reinforced alternation) in the radial maze in the same manner as controls, whereas performance of delayed alternation in the T-maze and the radial maze was impaired in lesioned rats. In addition, locomotor activity during maze performance was increased in lesioned rats. Based on the hypothesis that increased motor activity and impaired delayed alternation performance are due to increased susceptibility to interfering stimuli, we propose tentatively that prefrontal dopamine may function to suppress interference during the delay period of certain cognitive tasks.

Afferent Pathways↗
PubMed1990

A further characterization of the spatial problem-solving deficit induced by lesions of the medial frontal cortex in the rat.

Two experiments were conducted to investigate the basis of the spatial impairment displayed by rats with lesions to the medial frontal cortex, using a three-table Y-shaped apparatus. In both experiments, animals were first given an exploratory experience of the maze, followed by a short feeding experience on one of the tables, and were then required to return to the location where they had just been fed. In Expt. 1, a spatial working memory procedure was used in which the location of the goal table was varied from day to day. When compared to normal animals frontal rats showed a marked impairment, despite the addition of (a) distinctive visual cues on the tables and their associated runways, or (b) a conspicuous visual pattern placed directly above the goal. Expt. 2 used a spatial learning procedure, in which the spatial location of the goal table remained constant over days. However, the whole apparatus was daily rotated so that animals could not learn to associate the goal table with specific cues located behind it. This procedure did not prevent frontal animals from learning the consistent location of the food by using the spatial relationships of the environment. These results, together with previous ones, suggest that frontal animals suffer from a specific (though not restricted to the domain of spatial information) working memory deficit, and their spatial reference memory is not impaired.

Animals↗
PubMed1990

No correlations between spatial and non-spatial reference memory in a T-maze task and hippocampal mossy fibre distribution in the mouse.

Two reference memory tasks were tested in a T-maze, which was placed in a spatially richly structured environment and turned 180 degrees between trials following a semi-random schedule. Male mice from 9 different inbred strains were either trained always to go to the same place (spatial task) or always to make the same turn (non-spatial task). Animals were subsequently processed for Timm's stain and the sizes of their intra- and infrahippocampal mossy fibre terminal fields (ipp-MF) were measured. Significant strain differences were found for this variable and in both learning tasks, but learning and hippocampal variation did not correlate. This disagrees with earlier findings in a radial maze, where significant correlations between the iipMF and spatial reference memory were obtained. Two hypotheses are brought forward to explain this discrepancy. First, in radial mazes (multiple choices) different memory capabilities might be used than in T-mazes (only two choices). Second, a considerable amount of stress appeared to be present in our subjects, possibly induced by the large size of the T-maze. This might have interfered negatively with acquisition. Further experiments will be needed to test these hypotheses.

Animals↗
PubMed1990

Regional cues and visual discrimination in the rabbit.

Rabbits were trained to discriminate patterns consisting of straight bars and rows of dots of different orientation. It was found that using proximal pattern presentation, at a distance of 5 cm in front of the animal, dot rows of different orientation are not discriminated on the basis of tilt extrapolation, but by the use of regional cues.

Animals↗
PubMed1990

Activation of the noradrenergic system facilitates an attentional shift in the rat.

The noradrenergic system was pharmacologically activated with the alpha 2 receptor antagonist, idazoxan (2 mg/kg i.p.), during the acquisition of a complex appetitive task requiring a shift in attention to stimulus dimension and in response strategy. Rats first learned a fixed path of 6 successive choices in a linear maze. The task was then changed to a visual discrimination task in which the spatial configuration of the correct path was indicated by visual cues and changed on each daily trial. During this part of the task, the rats were injected before each trial with idazoxan, a drug which increases the firing rate of neurons in the locus coeruleus and the release of noradrenaline in the cortex and hippocampus. Two control experiments showed that the drug treatment had no effect on the acquisition of either component of the task - the successive place learning or the visual discrimination. The drug was found to be effective only during the shift phase of the experiment, the idazoxan-treated rats taking fewer trials to reach criterion than the saline. A second experiment showed that idazoxan increased the amount of time spent investigating novel and unexpected objects in a familiar hole board. These results implicate the noradrenergic system in problem-solving which requires an attentional shift or a shift in responding from familiar to novel stimuli.

Animals↗
PubMed1990

The effect of unilateral anteromedial cortex lesions on prey-catching and spatio-motor behaviour in the rat.

The neglect which follows a unilateral lesion of anteromedial cortex in rat was examined using two tasks. In the first task animals had to press the left bar of a two-bar Skinner box for food reward. In the second task animals captured live locusts presented in either their right or left visual field. The results showed that in the Skinner box there was a transitory spatial neglect contralateral to the lesion, which disappeared after 2-3 days. In the prey-catching task animals failed to target or track locusts when they were in the field contralateral to the lesion throughout the 4-day testing period. Capture and consummatory responses were normal when the locust was presented (or moved independently) into the ipsilateral (non-neglected) field. 60 days later the asymmetrical response to locusts in the contralateral field had disappeared.

Animals↗
PubMed1990

Regionally selective roles of the rat's striatum in modality-specific discrimination learning and forelimb reaching.

Rats with ibotenate lesions of either the medial striatum or the lateral striatum were trained in a forelimb reaching task and in acquisition, retention and reversal of either turn (left-right) discrimination or brightness (black-white) discrimination in a cross-shape maze. Compared with the controls, the rats with lesions of the medial striatum showed a reliable, modality-selective impairment in reversal of turn discrimination, but no significant impairment of reaching. In contrast, the rats with lateral striatal lesions showed a significant impairment of forelimb reaching, but not of reversal of either discriminations. Neither medial nor lateral lesions significantly affected acquisition and retention of both discriminations. The findings indicate a predominant role of the medial striatum in monitoring of directional responses, confirm the regionally specific role of the lateral striatum in reaching, and are interpreted to support the hypothesis of parallel motor and cognitive forebrain circuits comprising distinctive regions of the striatum.

Animals↗
PubMed1990

Effects of peripherally administered arginine-vasopressin on learning, retention and forgetting in mice.

The effects of peripheral injections of (Arg)-vasopressin were investigated on different stages of memory processes using an appetitive visual discrimination task and a one-trial passive avoidance conditioning in mice. The peptide was administered at one of two doses: 50 micrograms/kg or 25 micrograms/kg. The main effects of vasopressin were observed only for the higher dose. Concerning pre-session vasopressin administration in the visual discrimination task, the effect of the peptide seemed to depend on the level of learning reached at the time of treatment. Indeed, we observed a deleterious effect of vasopressin on learning capacities when the peptide was administered before the first learning session, a bimodal effect (either an improvement or an impairment) on performance when the peptide was administered before the second learning session and an important enhancement of retention performance when the peptide was administered before the retention session, performed 24 days after training. When post-session vasopressin administration was assessed, an improvement of performance was observed indicating a facilitatory effect of vasopressin on consolidation processes. When passive avoidance conditioning was used, an enhancement of retention performance was registered only when the peptide was injected before the retention session at the 50 micrograms/kg dose. No facilitation was observed for the 25 micrograms/kg dose whatever the experimental condition was, i.e. post-learning or pre-retention injection. In order to test eventual non-specific effects of vasopressin, the influence of the peptide on locomotor activity was assessed before the two doses. The results show an important reduction of locomotor activity with the 50 micrograms/kg dose, during 4 h following vasopressin injection. No effect was observed with the 25 micrograms/kg dose. The whole results suggest that vasopressin-induced hypoactivity can directly influence the subsequent learning performance when the treatment was performed in pre-session situations. However, when the level of information is sufficient and beyond the direct effect of the drug, a memory effect may be considered with the 50 micrograms/kg dose independently from the locomotor effect, when the treatment was delivered during consolidation period (post-session) or in long-term retrieval situation (pre-session).

Animals↗
PubMed1990

Effects of GABAergic drugs, fornicotomy, hippocampectomy and septal lesions on the extinction of a discrete-trial fixed ratio 5 lever-press response.

The effects of certain GABA-modulating drugs, fornicotomy, hippocampectomy and various septal lesions were analysed in a discrete-trial fixed ratio 5 (FR5) bar-press paradigm. Chlordiazepoxide, fornicotomy, hippocampectomy, electrolytic lateral septal lesions and ibotenic acid medial septal lesions facilitate extinction of the FR5 response. Some of these treatments (chlordiazepoxide, hippocampectomy, electrolytic lateral septal lesions) have previously been found to increase resistance to extinction of alley-running after continuously reinforced (CRF) acquisition training. The treatments which facilitated extinction in the discrete-trial FR5 paradigm have been found to reduce or abolish the partial reinforcement extinction effect in the alley. These results indicate that the discrete-trial FR5 paradigm is not analogous to a runway CRF schedule, but may be analogous to a runway partial reinforcement schedule.

Animals↗
PubMed1990

The NMDA antagonist dizocilpine (MK-801) reverses haloperidol-induced movement initiation deficits.

The present study shows that systemic dopamine receptor blockade impaired movement initiation of rats, trained in a simple reaction time task for rapid initiation of locomotion in response to a combined optic/acoustic cue. Reaction time, movement time and the accelerative force were recorded for each initiation of locomotion. Results indicate a dose-related increase of reaction time following systemic administration of haloperidol (0.1, 0.15, 0.3 mg/kg i.p.). Measures derived from resulting force-time patterns showed a haloperidol-induced decrease (0.15 mg/kg i.p.) of the mean rate of force development, indicating a decreased initial acceleration. These effects were reversed by systemic co-administration of dizocilpine (MK-801) (0.08 mg/kg i.p.), a selective non-competitive N-methyl-D-aspartate (NMDA) antagonist. The haloperidol-induced movement initiation deficits in this task are in part comparable to akinesia seen in Parkinson's disease and their reversal by dizocilpine has implications for the treatment of this disease.

Animals↗