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PubMed1994

Behavioral impairment in radial-arm maze learning and acetylcholine content of the hippocampus and cerebral cortex in aged mice.

Age-related changes in spatial learning performance were studied in relation to acetylcholine (ACh) content of brain regions in male aged (28-month-old) and young (5-month-old) mice of BDF1 strain. As there were large individual differences in the spatial performance of aged mice, the aged mice were divided into two subgroups, old A and old B. The old A group included the six best performers out of the 12 aged mice and the old B group included the remaining 6 worst performers. In a radial-arm maze task with 8 baited arms, aged mice in the old B group showed a marked deficit in acquisition performance and habituation to the apparatus. In the more difficult maze task with only 4 baited arms, the aged mice in the old B group exhibited marked impairment both in working memory and reference memory throughout training, whereas the aged mice in the old A group showed deficits in reference memory during the first 20 days of training and working memory during the last 20 days relative to young mice. Neurochemical analysis revealed significant decreases in the ACh content of the hippocampus and striatum in both aged groups, and in the frontal cortex and posterior cortex of the old B group as compared to the young group. Correlational analysis showed significant correlations between learning performance in the spatial task and ACh levels in the hippocampus, frontal cortex, and posterior cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1992

The limbic system and food-anticipatory circadian rhythms in the rat: ablation and dopamine blocking studies.

Rats behaviorally anticipate a fixed, daily opportunity to feed by entrainment of circadian oscillators that are physically separate from the light-entrainable circadian pacemaker that has been localized to the suprachiasmatic nucleus. Neural substrates mediating food-entrained rhythms are unknown. A variety of anatomical and functional observations suggest possible involvement of the limbic system and its dopaminergic component in the regulation of these rhythms. To test this hypothesis, the activity rhythms of rats bearing large, combined ablations of the hippocampus and amygdala or nucleus accumbens and medical forebrain anterior to the thalamus were examined under ad-lib feeding, 2 h daily feeding, and total food deprivation conditions. Some hippocampal-ablated rats showed alterations of free-running rhythms under ad-lib feeding, but none of the ablations impaired the rats' ability to anticipate daily feeding, or 'remember' the phase of feeding time during subsequent food deprivation. Additional groups of intact rats were treated with the dopamine antagonist haloperidol (0.3 mg/kg or 2.0 mg/kg) 30 min prior to daily feeding, but this also did not prevent the emergence of food-entrained rhythms. The limbic and dopamine systems do not appear to play a necessary role in the generation or entrainment of food-anticipatory circadian rhythms.

Amygdala↗

PubMed1990

The effects of reinforcement frequency and response requirements on the maintenance of behavior.

Six rats responded under fixed-interval and tandem fixed-interval fixed-ratio schedules of food reinforcement. Basic fixed-interval schedules alternated over experimental conditions with tandem fixed-interval fixed-ratio schedules with the same fixed-interval value. Fixed-interval length was varied within subjects over pairs of experimental conditions; the ratio requirement of the tandem schedules was varied across subjects. For both subjects with a ratio requirement of 10, overall response rates and running response rates typically were higher under the tandem schedules than under the corresponding basic fixed-interval schedules. For all subjects with ratio requirements of 30 or 60, overall response rates and running response rates were higher under the tandem schedules than under the corresponding basic fixed-interval schedules only with relatively short fixed intervals. At longer fixed intervals, higher overall response rates and running rates were maintained by the basic fixed-interval schedules than by the tandem schedules. These findings support Zeiler and Buchman's (1979) reinforcement-theory account of response strength as an increasing monotonic function of both the response requirement and reinforcement frequency. Small response requirements added in tandem to fixed-interval schedules have little effect on reinforcement frequency and so their net effect is to enhance responding. Larger response requirements reduce reinforcement frequency more substantially; therefore their net effect depends on the length of the fixed interval, which limits overall reinforcement frequency. At the longest fixed intervals studied in the present experiment, reinforcement frequency under the tandem schedules was sufficiently low that responding weakened or ceased altogether.

Animals↗

PubMed1991

The latent inhibition model of schizophrenic attention disorder. Haloperidol and sulpiride enhance rats' ability to ignore irrelevant stimuli.

Latent inhibition (LI) is a behavioral paradigm in which prior exposure to a stimulus not followed by reinforcement retards subsequent conditioning to that stimulus when it is paired with reinforcement. The development of LI reflects a process of learning to ignore, or tune out, irrelevant stimuli. Two experiments investigated the effects of haloperidol (0.02, 0.1, and 0.5 mg/kg) and sulpiride (100 mg/kg) administration on LI. The investigation was carried out using a conditioned emotional response (CER) procedure consisting of three stages: (1) preexposure, in which the to-be-conditioned stimulus, tone, was repeatedly presented without reinforcement; (2) conditioning, in which the preexposed stimulus was paired with shock; and (3) test, where LI was indexed by animals' suppression of licking during tone presentation. The three stages were conducted 24 hr apart. In the preexposure stage, only ten nonreinforced stimulus preexposures were given, a procedure known to be insufficient to yield LI in normal animals. In both experiments, LI was indeed absent in the placebo animals. In marked contrast, animals treated with haloperidol (experiment 1) as well as with sulpiride (experiment 2) exhibited LI. These results demonstrate that both typical and atypical neuroleptics enhance animals' capacity to ignore irrelevant stimuli. The implications of this finding for an animal model of schizophrenia and for a novel screening test for antipsychotic drugs are discussed.

Animals↗

PubMed2006

Neurochemical modulation of ingestive behavior in the ventral pallidum.

The nucleus accumbens and its related circuitry have been shown to play an important role in promoting the intake of hedonically desirable food. A previous report has demonstrated that the blockade of GABAA receptors in the ventral pallidum (VP), a target of GABAergic projection from the nucleus accumbens, greatly increases food, but not water, intake in satiated rats [Stratford et al. (1999)Brain Research, 825, 199-203]. The present study examined which neurotransmission in the VP is specifically involved in the intake of normally preferred taste stimuli. Microinjections of the GABAA antagonist bicuculline selectively increased the intake of saccharin solution but not that of water and quinine solution in water-deprived rats. In contrast, the facilitation of GABAA receptors by microinjections of muscimol in the VP generally suppressed the intake of saccharin, water and quinine. The same injections induced strong aversive taste reactivity responses to oral stimulation with not only quinine but also water and saccharin. The local administration of D-Ala2,N-Me-Phe4,Glyol5-enkephalin, a selective micro-opioid receptor agonist, into the VP had time-dependent effects, decreasing saccharine intake early and increasing intake late. Microinjections of SCH-23390, a dopamine D1 receptor antagonist, in the VP suppressed the intake of saccharin but not water or quinine. Microinjections of sulpiride, the dopamine D2 receptor antagonist, and 6-cyano-7-nitroquinoxaline-2,3-dione, the AMPA/kainate glutamate receptor antagonist, had no effect on fluid intake. These results reveal that GABA, opioid and D1 receptors in the VP are involved in the consumption of hedonically positive taste stimuli.

Animals↗

PubMed2005

Skilled reaching impairments from the lateral frontal cortex component of middle cerebral artery stroke: a qualitative and quantitative comparison to focal motor cortex lesions in rats.

The classical approach to investigating brain contributions to behavior has been to localize function to a region. In clinical investigations, however, injury is frequently multifocal, raising the question of how individual brain regions contribute to a resulting behavioral syndrome. For example, middle cerebral artery (MCA) ischemia in humans can concurrently damage a number of cortical and subcortical areas and the same areas are damaged in rat models of MCA stroke. In the rat, MCA occlusion produces severe motor deficits, but the cortical area of damage is the lateral neocortex, sparing motor cortex. This anatomical finding raises the question of whether the rat lateral neocortex contributes to MCA-related motor impairments, a question that was investigated in the present study. Rats received unilateral neocortical lesions via electrocoagulation of the MCA and were compared to rats with standard motor cortex lesions produced by devascaulrization of the overlaying blood vessels. The MCA group was as impaired as the motor cortex group in skilled reaching movements as assessed by quantitative measures of the contralateral-to-lesion forelimb in a single pellet task and in a tray-reaching task. Although there was improvement in success scores over a 2-week period in both groups, the groups were characterized by distinctive and enduring qualitative impairments. The motor cortex deficit was exemplified by use of trunk musculature and head movements to assist the reaching limb while the MCA impairment included sensory abnormalities. The results are discussed in relation to the contribution of lateral frontal cortex injury to MCA stroke sensorimotor syndromes.

Animals↗

PubMed1993

GABA antagonist and benzodiazepine partial inverse agonist reduce motivated responding for ethanol.

Brain gamma-aminobutyric acid (GABA) systems have long been associated with the behavioral actions of ethanol. This study investigated the effects of GABAergic agents on ethanol reinforcement. Rats were trained to orally self-administer ethanol in a 30-min, free-choice operant task. Responses at one of two levers produced contingent access to ethanol (10% w/v) or water. Pretreatment with RO 15-4513, a benzodiazepine inverse agonist (0.375 to 3.0 mg/kg ip), selectively reduced responses for ethanol, and a higher dose of RO 15-4513 (6.0 mg/kg) reduced both ethanol and water responses. Self-administration of saccharin in a free-choice task with access to saccharin (0.05%) and water was unaffected by RO 15-4513, suggesting that the effects of RO 15-4513 on ethanol reinforcement may not necessarily generalize to other reinforcers. Isopropylbicyclophosphate (IPPO), a picrotoxin ligand (5 and 10 micrograms/kg ip), selectively reduced responses for ethanol in alcohol-preferring, nonpreferring and Wistar rats. However, the highest dose of IPPO (20 micrograms/kg) reduced both ethanol and water responses. Chlordiazepoxide, a benzodiazepine, did not reduce responses for ethanol in the selectively bred animals, suggesting that this drug does not substitute for the reinforcing properties associated with acute ethanol intake. Together, these results suggest that compounds that act at the benzodiazepine inverse agonist and picrotoxin sites of the GABA/benzodiazepine receptor complex may decrease motivated responding for ethanol.

Alcohol Drinking↗

PubMed2006

Fix and sample with rats in the dynamics of choice.

The generality of the molar view of behavior was extended to the study of choice with rats, showing the usefulness of studying order at various levels of extendedness. Rats' presses on two levers produced food according to concurrent variable-interval variable-interval schedules. Seven different reinforcer ratios were arranged within each session, without cues identifying them, and separated by blackouts. To alternate between levers, rats pressed on a third changeover lever. Choice changed rapidly with changes in component reinforcer ratio, and more presses occurred on the lever with the higher reinforcer rate. With continuing reinforcers, choice shifted progressively in the direction of the reinforced lever, but shifted more slowly with each new reinforcer. Sensitivity to reinforcer ratio, as estimated by the generalized matching law, reached an average of 0.9 and exceeded that documented in previous studies with pigeons. Visits to the more-reinforced lever preceded by a reinforcer from that lever increased in duration, while all visits to the less-reinforced lever decreased in duration. Thus, the rats' performances moved faster toward fix and sample than did pigeons' performances in previous studies. Analysis of the effects of sequences of reinforcer sources indicated that sequences of five to seven reinforcers might have sufficed for studying local effects of reinforcers with rats. This study supports the idea that reinforcer sequences control choice between reinforcers, pulses in preference, and visits following reinforcers.

Animals↗

PubMed1989

Facilitation of acquisition and retention in preweanling but not postweanling rats by the presence of familiar home-nest material.

A series of four experiments examined the effect of the presence of stimuli from the home nest on the acquisition and retention of aversively motivated behaviors in preweanling and adult rats. In Experiment 1, training in the presence of home-nest shavings facilitated acquisition of a T-maze discrimination to escape footshock for 16-day-old rats but not for adults. Experiment 2 demonstrated that the extent to which preweanlings were familiar with the home shavings determines the degree to which these stimuli facilitate spatial discrimination learning. When clean shavings were made more familiar than soiled home-nest stimuli (by changing the shavings every day) clean shavings enhanced discrimination performance, whereas no enhancement of learning by home shavings was observed. Experiment 3 extended the generality of the enhancement effect to a conditioned location aversion and examined the extent to which this facilitative effect was due to the tendency for home-nest shavings to elicit approach responses. Expression of the conditioned aversion was enhanced in subjects conditioned in the presence of home shavings, regardless of whether the home shavings were presented with the CS+, the CS-, or both. Experiment 4 determined that the enhanced expression of learning in the context of home-nest stimuli observed for preweanlings did not occur among subjects trained shortly after weaning. Collectively, these data suggest that whereas the enhancement of learning and retention by familiar home-nest stimuli enjoys generality across a number of conditioning situations, the effect may be limited to a relatively brief period during ontogeny.

Aging↗

PubMed2006

Ghrelin and the short- and long-term regulation of appetite and body weight.

Ghrelin, an acylated upper gastrointestinal peptide, is the only known orexigenic hormone. Considerable evidence implicates ghrelin in mealtime hunger and meal initiation. Circulating levels decrease with feeding and increase before meals, achieving concentrations sufficient to stimulate hunger and food intake. Preprandial ghrelin surges occur before every meal on various fixed feeding schedules and also among individuals initiating meals voluntarily without time- or food-related cues. Ghrelin injections stimulate food intake rapidly and transiently, primarily by increasing appetitive feeding behaviors and the number of meals. Preprandial ghrelin surges are probably triggered by sympathetic nervous output. Postprandial suppression is not mediated by nutrients in the stomach or duodenum, where most ghrelin is produced. Rather, it results from post-ingestive increases in lower intestinal osmolarity (information probably relayed to the foregut via enteric nervous signaling), as well as from insulin surges. Consequently, ingested lipids suppress ghrelin poorly compared with other macronutrients. Beyond a probable role in meal initiation, ghrelin also fulfills established criteria for an adiposity-related hormone involved in long-term body-weight regulation. Ghrelin levels circulate in relation to energy stores and manifest compensatory changes in response to body-weight alterations. Ghrelin crosses the blood-brain barrier and stimulates food intake by acting on several classical body-weight regulatory centers, including the hypothalamus, hindbrain, and mesolimbic reward system. Chronic ghrelin administration increases body weight via diverse, concerted actions on food intake, energy expenditure, and fuel utilization. Congenital ablation of the ghrelin or ghrelin-receptor gene causes resistance to diet-induced obesity, and pharmacologic ghrelin blockade reduces food intake and body weight. Ghrelin levels are high in Prader-Willi syndrome and low after gastric bypass surgery, possibly contributing to body-weight alterations in these settings. Extant evidence favors roles for ghrelin in both short-term meal initiation and long-term energy homeostasis, making it an attractive target for drugs to treat obesity and/or wasting disorders.

Animals↗

PubMed1990

Fixed-consecutive-number performance in male and female Wistar rats.

The present experiment was designed to investigate whether or not response rate differences between male and female Wistar rats observed in many different experimental procedures could be attributed to sex differences in behavioral perseverance, as has been suggested by the results of previous experiments. Male and female Wistar rats were thus exposed to different fixed-consecutive-number schedules of reinforcement. Fixed-consecutive-number schedules require subjects to emit a specified number of responses on one (work) lever, before a response on another (food) lever results in the presentation of reinforcement. The response requirement on the work lever was manipulated in different experimental conditions. Subjects had to emit between 3 and 7, 8 and 12 or 13 and 17 responses on the work lever before a response on the food lever produced reinforcement. When subjects emitted fewer or more than the required number of responses on the work lever, a 5-s time-out period was presented. Males responded at higher rates than females during all experimental conditions; response rates of males and females increased as the response requirement on the work lever was increased. Sex differences in response efficiency were not observed, but males seemed to reach final response efficiency faster than females. Response efficiency decreased as the response requirement on the work lever was increased. Error analysis showed that both males and females made more errors by not producing enough responses on the work lever than by producing too many. However, males were more likely than females to emit more responses than the requirement on the work lever, while females were more likely than males not to produce enough responses on the work lever.

Animals↗

PubMed2001

Behavioral and pharmacological variables affecting risky choice in rats.

The effects of manipulations of response requirement, intertrial interval (ITI), and psychoactive drugs (ethanol, phencyclidine, and d-amphetamine) on lever choice under concurrent fixed-ratio schedules were investigated in rats. Responding on the "certain'' lever produced three 45-mg pellets, whereas responding on the "risky" lever produced either 15 pellets (p = .33) or no pellets (p .67). Rats earned all food during the session, which ended after 12 forced trials and 93 choice trials or 90 min, whichever occurred first. When the response requirement was increased from 1 to 16 and the ITI was 20 s, percentage of risky choice was inversely related to fixed-ratio value. When only a single response was required but the ITI was manipulated between 20 and 120 s (with maximum session duration held constant), percentage of risky choice was directly related to length of the ITI. The effects of the drugs were investigated first at an ITI of 20 s, when risky choice was low for most rats, and then at an ITI of 80 s, when risky choice was higher for most rats. Ethanol usually decreased risky choice. Phencyclidine did not usually affect risky choice when the ITI was 20 s but decreased it in half the rats when the ITI was 80 s. For d-amphetamine, the effects appeared to he related to baseline probability of risky choice; that is, low probabilities were increased and high probabilities were decreased. Although increase in risky choice as a function of the ITI is at variance with previous ITI data, it is consistent with foraging data showing that risk aversion decreases as food availability decreases. The pharmacological manipulations showed that drug effects on risky choice may be influenced by the baseline probability of risky choice, just as drug effects can be a function of baseline response rate.

Animals↗

PubMed1997

The nitric oxide synthase inhibitor L-NAME (N omega-nitro-L-arginine methyl ester) does not produce discriminative stimulus effects similar to ethanol.

N-methyl-D-aspartate (NMDA) antagonists substitute for the discriminative stimulus effects of ethanol, indicating that a component of ethanol's behavioral activity is produced via blockade of NMDA receptor/channel function. Recently, it has been reported that ethanol inhibits NMDA-stimulated nitric oxide synthase (NOS) activity in cortical neurons, thereby decreasing the formation of nitric oxide (NO) in the brain. These findings suggest that some of the behavioral effects of ethanol may be mediated by inactivation of NOS. The present study examined the role of NO formation in mediating the discriminative stimulus effects of ethanol. To address this hypothesis, an NOS inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME) and an NMDA competitive antagonist, (D)-4-(3-phosphonoprop-2-enyl) piperazine-2-carboxylic acid (CPPene), were administered to two groups of rats trained to discriminate 1.5 g/kg of ethanol (n = 6) or 2.0 g/kg (n = 7) of ethanol from water. After training, dose ranges of CPPene (3 to 17 mg/kg, ip) and L-NAME (100 to 780 mg/kg, ip) were tested for ethanol-like effects. L-NAME was also tested under a range of pretreatment times (20, 60, 90, and 120 min). An additional group of rats trained to discriminate 2.0 g/kg (n = 7) of ethanol from water was also tested with CPPene (10 mg/kg, ip) and L-NAME (100 and 300 mg/kg, ip) to verify data gathered from the original 2.0 g/kg of ethanol group tested with L-NAME after a 20-minute pretreatment. Although overall, 17 of 20 animals trained to discriminate ethanol from water exhibited complete substitution of CPPene for ethanol, L-NAME, without affecting response rates, did not consistently substitute for either 1.5 g/kg or 2.0 g/kg of ethanol. These results indicate that inhibition of NO formation is less effective than direct NMDA receptor antagonism in producing ethanol-like discriminative stimulus effects.

Animals↗

PubMed1987

The echolocation and hunting behavior of the bat, Pipistrellus kuhli.

The echolocation and hunting behavior of Pipistrellus kuhli was studied in the field using multi-exposure photography synchronized with high-speed tape recordings. During the search phase, the bats used 8-12 ms signals with sweeps (sweep width 3-6 kHz) and pulse intervals near 100 ms or less often near 200 ms. The bats seemed to have individual terminal frequencies that could lie between 35 and 40 kHz. The duty cycle of searching signals was about 8%. The flight speed of hunting bats was between 4.0 and 4.5 m/s. The bats reacted to insect prey at distances of about 70 to 120 cm. Given the flight speed, the detection distance was estimated to about 110 to 160 cm. Following detection the bat went into the approach phase where the FM sweep steepened (to about 60 kHz bandwidth) and the repetition rate increased (to about 30 Hz). The terminal phase or 'buzz', which indicates prey capture (or attempted capture), was composed of two sections. The first section contained signals similar to those in the approach phase except that the pulse duration decreased and the repetition rate increased. The second section was characterized by a sharp drop in the terminal frequency (to about 20 kHz) and by very short pulses (0.3 ms) at rates of up to 200 Hz. Near the beginning of the buzz the bat prepared for capturing the prey by extending the wings and forming a tail pouch. A pause of about 100 ms in sound emission after the buzz indicated a successful capture (Fig. 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2005

A specific limbic circuit underlies opiate withdrawal memories.

Compulsive drug-seeking behavior and its renewal in former drug addicts is promoted by several situations, among which reactivation of drug withdrawal memories plays a crucial role. A neural hypothesis is that such memories reactivate the circuits involved in withdrawal itself and promote a motivational state leading to drug seeking or taking. To test this hypothesis, we have analyzed the neural circuits and cell populations recruited when opiate-dependent rats are reexposed to stimuli previously paired with withdrawal (memory retrieval) and compared them with those underlying acute withdrawal during conditioning (memory formation). Using in situ hybridization for c-fos expression, we report here that reexposure to a withdrawal-paired environment induced conditioned c-fos responses in a specific limbic circuit, which can be partially dissociated from the structures involved in acute withdrawal. At the amygdala level, c-fos responses were doubly dissociated between the central and basolateral (BLA) nuclei, when comparing the two situations. Detailed phenotypical analyses in the amygdala and ventral tegmental area (VTA) show that specific subpopulations in the BLA are differentially involved in the formation and retrieval of withdrawal memories, and strikingly that a population of VTA dopamine neurons is activated in both situations. Together, this indicates that withdrawal memories can drive activity changes in specific neuronal populations of interconnected limbic areas known to be involved in aversive motivational processes. This first study on the neural substrates of withdrawal memories strongly supports an incentive-motivational view of withdrawal in opiate addiction that could be crucial in compulsive drug seeking and relapse.

Amygdala↗

PubMed2000

The chemical defense ecology of marine unicellular plankton: constraints, mechanisms, and impacts.

The activities of unicellular microbes dominate the ecology of the marine environment, but the chemical signals that determine behavioral interactions are poorly known. In particular, chemical signals between microbial predators and prey contribute to food selection or avoidance and to defense, factors that probably affect trophic structure and such large-scale features as algal blooms. Using defense as an example, I consider physical constraints on the transmission of chemical information, and strategies and mechanisms that microbes might use to send chemical signals. Chemical signals in a low Re, viscosity-dominated physical environment are transferred by molecular diffusion and laminar advection, and may be perceived at nanomolar levels or lower. Events that occur on small temporal and physical scales in the "near-field" of prey are likely to play a role in cell-cell interactions. On the basis of cost-benefit optimization and the need for rapid activation, I suggest that microbial defense system strategies might be highly dynamic. These strategies include compartmented and activated reactions, utilizing both pulsed release of dissolved signals and contact-activated signals at the cell surface. Bioluminescence and extrusome discharge are two visible manifestations of rapidly activated microbial defenses that may serve as models for other chemical reactions as yet undetected due to the technical problems of measuring transient chemical gradients around single cells. As an example, I detail an algal dimethylsulfoniopropionate (DMSP) cleavage reaction that appears to deter protozoan feeding and explore it as a possible model for a rapidly activated, short-range chemical defense system. Although the exploration of chemical interactions among planktonic microbes is in its infancy, ecological models from macroorganisms provide useful hints of the complexity likely to be found.

Animals↗

PubMed1988

Food wrenching and dodging: a neuroethological test of cortical and dopaminergic contributions to sensorimotor behavior in the rat.

Sensorimotor behavior in unilateral decorticate and unilateral dopamine-depleted rats was studied in a naturally occurring social interaction in which rats compete for food with relatively stereotyped species-typical responses. In the interaction a "robber" attempts to wrest food from a feeding "victim," which in turn protects the food by making rapid contralateral dodges. Hemidecortication abolished dodging to food wrenching attempts made by a rat approaching contralaterally to the lesion, so that the food was stolen, but recovery occurred between 15 and 60 days after surgery. Use of the side contralateral to the lesion to wrest food was moderately impaired, and recovery of food wresting was more rapid than recovery of dodging. There were no impairments in dodging to approaches to the side of the body ipsilateral to the lesion, nor were there impairments in using that side of the body to wrest food from other rats. Unilateral dopamine depletion produced dodging impairments to food-wresting attempts that were made both ipsilateral and contralateral to the side of the lesion, and the deficits endured over 60 test days. The food was frequently lost to food-wrenching attempts made contralateral to the lesion, whereas the direction of dodges to approaches ipsilateral to the lesion was reversed. Food wresting was also bilaterally impaired. In conclusion, the study shows (a) there are differences in the sensorimotor impairments that follow unilateral neocortical damage and unilateral dopamine depletion, (b) the neural organization of orienting and dodging is different, and (c) the form of the sensorimotor impairments as well as the processes of recovery can be usefully analyzed by using species-typical social interactions.

Animals↗

PubMed1987

Edge preference of retinal and tectal neurons in common toads (Bufo bufo) in response to worm-like moving stripes: the question of behaviorally relevant 'position indicators'.

Previous experiments have shown that during prey-catching behavior (orienting, snapping) in response to a worm-like moving stripe common toads, Bufo bufo (L.) exhibit a contrast- and direction-dependent edge preference. To a black (b) stripe moving against a white (w) background (b/w), they respond (R*) preferably toward the leading (l) rather the trailing (t) edge (Rl* greater than Rt*), thus displaying 'head preference'. If the contrast-direction is reversed (w/b), the stripe's trailing edge is preferred (Rl* less than Rt*), hence showing 'tail preference'. In the present study, neuronal activities of retinal classes R2 and R3 and tectal classes T5(2) and T7 have been extracellularly recorded in response to leading and trailing edges of a 3 degrees X 30 degrees stripe simulating a worm and traversing the centers of their excitatory receptive fields (ERF) horizontally at a constant angular velocity in variable movement direction (temporo-nasal or naso-temporal). The behavioral contrast-direction dependent edge preferences are best resembled by the responses (R) of prey-selective class T5(2) neurons (Rl:Rt = 10:1 for b/w, 0.3:1 for w/b) and T7 neurons (Rl:Rt = 6:1 for b/w, 0.4:1 for w/b); the T7 responses may be dendritic spikes. This property can be traced back to off-responses dominated retinal class R3 neurons (Rl:Rt = 6:1 for b/w, 0.5:1 for w/b), but not to class R2 (Rl:Rt = 1.2:1 for b/w and 0.9:1 for w/b). The respective edge preference phenomena are independent of the direction of movement. When stimuli were moved against a stationary black-white structured background, the 'head preference' to the black stripe and the 'tail preference' to the white stripe were maintained in class R3, T5(2), and T7 neurons. If the stripe traversed the ERF together with the structured background in the same direction at the same velocity, the responses of tectal class T5(2) and T7 neurons were strongly inhibited, particularly in the former. Responses of retinal R2 neurons in comparable situations could be reduced by about 50%, while class R3 neurons responded to both the stimulus and the moving background structure. The results support the concept that the prey feature analyzing system in toads applies principles of (i) 'parallel' and (ii) 'hierarchial' information processing. These are (i) divergence of retinal R3 neuronal output contributes to stimulus edge positioning and (in combination with R2 output) area evaluation in tectal neurons and to stimulus area evaluation and (in combination with R4 output) sensitivity for moving background structures in pretectal neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗