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Showing papers in "Behavioral Neuroscience in 1998"


Journal Article•DOI•
TL;DR: Adult rats with icv-injected STZ developed long-term and progressive deficits in learning, memory, and cognitive behavior, indicated by decreases in working and reference memory in the holeboard task and the passive avoidance paradigm, along with a permanent and ongoing cerebral energy deficit.
Abstract: Drastic abnormalities have been demonstrated to occur in cerebral glucose and energy metabolism in sporadic Alzheimer's disease, pointing to a primary disturbance in neuronal insulin and insulin receptor signal transduction and contributing to the causation of dementia. The compound streptozotocin (STZ) is known to inhibit insulin receptor function. The study was designed to investigate whether intracerebroventricularly (icv) applied STZ would inhibit neuronal insulin receptor function and would induce changes in both behavior and neuronal energy metabolism. Adult rats with icv-injected STZ developed long-term and progressive deficits in learning, memory, and cognitive behavior, indicated by decreases in working and reference memory in the holeboard task and the passive avoidance paradigm, along with a permanent and ongoing cerebral energy deficit. This animal model may be appropriate for investigations related to sporadic Alzheimer's dementia.

510 citations


Journal Article•DOI•
TL;DR: Together, these data dissociate hippocampal and nonhippocampal contributions to contextual conditioning, and they provide direct evidence that the hippocampus plays an essential role in the processing of contextual stimuli.
Abstract: The authors describe how (a) the timing of hippocampal lesions and (b) the behavioral-representational demands of the task affect the requirement for the hippocampus in contextual fear conditioning. Post- but not pretraining lesions of the hippocampus greatly reduced contextual fear conditioning. In contrast, pretraining lesions of the hippocampus abolished context discrimination, a procedure in which mice are trained to discriminate between 2 similar chambers (shock context vs. no-shock context). Whereas either contextual- or cue-based strategies can be used to recognize an aversive context, discrimination between similar contexts is optimally acquired by contextual (hippocampal)-based strategies. In keeping with the lesion results, Nf1(+/-)/Nmdar1(+/-) mutant mice, which have spatial learning deficits, are impaired in context discrimination but not in contextual conditioning. Together, these data dissociate hippocampal and nonhippocampal contributions to contextual conditioning, and they provide direct evidence that the hippocampus plays an essential role in the processing of contextual stimuli.

484 citations


Journal Article•DOI•
TL;DR: Findings demonstrate important relations among extreme asymmetric frontal electrical activity, cortisol levels, and trait-like fear-related behaviors in young rhesus monkeys.
Abstract: The authors examined the hypothesis that rhesus monkeys with extreme fight frontal electroencephalographic activity would have higher cortisol levels and would be more fearful compared with monkeys with extreme left frontal activity. The authors first showed that individual differences in asymmetric frontal electrical activity are a stable characteristic. Next, the authors demonstrated that relative fight asymmetric frontal activity and cortisol levels are correlated in animals 1 year of age. Additionally, extreme fight frontal animals had elevated cortisol concentrations and more intense defensive responses. At 3 years of age, extreme fight frontal animals continued to have elevated cortisol concentrations. These findings demonstrate important relations among extreme asymmetric frontal electrical activity, cortisol levels, and trait-like fear-related behaviors in young rhesus monkeys. Considerable evidence demonstrates that individual differences in temperament are associated with differences in brain and peripheral physiological functioning (e.g., Davidson & Tomarken, 1989; Kagan, Reznick, & Snidman, 1988). Thus, temperament can no longer be viewed simply as a stable trait-like behavioral and emotional style but should be considered as a constellation of stable behavioral, emotional, and physiological characteristics. How these different characteristics interact and the mechanisms underlying the formation of individual differences in temperament are important questions that remain to be answered. To begin to unravel these issues, we have used rhesus monkeys to more completely characterize the physiological concomitants of behavioral responses associated with fearful temperaments. Eventually, this information will guide studies aimed at elucidating the mechanisms underlying the development of individual differences in fear-related temperaments.

290 citations


Journal Article•DOI•
TL;DR: An animal model of obsessive-compulsive disorder and a role for dopamine in this disorder is suggested and Quinpiroleinduced compulsive checking may be an exaggeration of normal checking of home site in rats.
Abstract: Rats treated chronically with the dopamine agonist quinpirole (05 mg/kg, twice weekly x 10) met 5 criteria for performance of compulsive checking Specifically, in a large open-field with single small objects in 4 of 25 locales, quinpirole rats revisited two places/objects excessively often and rapidly, compared with other locations in the environment or saline controls They performed a ritual-like set of behavioral acts at these two places/objects and stopped in relatively few locales before returning to the preferred places/objects Finally, they shifted their behavior to a new location when the object was moved there Clomipramine (10 mg/kg, daily) postponed but did not prevent the development of the quinpirole effect Quinpirole-induced compulsive checking may be an exaggeration of normal checking of home site in rats Results suggest an animal model of obsessive-compulsive disorder and a role for dopamine in this disorder

276 citations


Journal Article•DOI•
TL;DR: Adult and periadolescents in the latter group exhibited a greater sensitization of the locomotor response, but did not show the compulsive licking typical of adults, and appears to be a useful model to study psychobiological risk factors involved in vulnerability to addiction during human adolescence.
Abstract: Novelty seeking as well as amphetamine sensitization were studied in adult (postnatal day "PND" > 60) and periadolescent (PND 3343) mice treated with saline or amphetamine (2 or 10 mg/kg once per day) for 3 days in a familiar environment. After a 48-hr wash-out period, mice were challenged with either saline or amphetamine (2 mg/kg) in the same environment. When given a choice, animals showed a preference for a novel environment, an effect more marked in periadolescents. Acute amphetamine strongly increased novelty seeking in adults, whereas it had an opposite effect in periadolescents. Adult mice in the chronic amphetamine 2 group showed a conditioned preference for the drug-paired compartment, whereas an aversion characterized adult mice in the amphetamine 10 group. Periadolescents in the latter group exhibited a greater sensitization of the locomotor response, but did not show the compulsive licking typical of adults. This appears to be a useful model to study psychobiological risk factors involved in vulnerability to addiction during human adolescence.

252 citations


Journal Article•DOI•
TL;DR: Olfactory perceptual processing is bidirectional and covers a wide frequency range and gamma band power in olfactory regions is significantly reduced during stimulus presentation as compared with high values during preafferent expectation.
Abstract: Field potentials were recorded simultaneously from the olfactory bulb (OB), prepyriform cortex (PPC), entorhinal cortex (EC), and dentate gyrus (DG) of rats trained to respond to appetitively reinforced odors. Preafferent anticipatory events in the beta band (12-35 Hz) suggest transmission from EC to OB before the odorant stimulus. Gamma band (35-120 Hz) power in olfactory regions is significantly reduced during stimulus presentation as compared with high values during preafferent expectation. High coherence of OB and PPC gamma activity during the preodorant control period is interrupted before the stimulus and is followed by increased gamma coherence among OB, EC, and DG. These results suggest that olfactory perceptual processing is bidirectional and covers a wide frequency range.

233 citations


Journal Article•DOI•
TL;DR: Findings suggest that learning can impact BDNF mRNA expression localized to the brain areas involved in the processing of spatial information and behaviors such as physical activity and learning may help maintain and protect neurons at risk in aging and neurodegenerative disease via increased BDNF expression.
Abstract: Brain-derived neurotrophic factor (BDNF) promotes neuron survival, enhances sprouting, protects neurons against insult, and may be involved in several aspects of learning and memory. In this study, rats trained to locate a submerged platform in a water maze had elevated levels of BDNF messenger ribonucleic acid (mRNA) in the hippocampus (p .05). These findings suggest that learning can impact BDNF mRNA expression localized to the brain areas involved in the processing of spatial information. Furthermore, behaviors such as physical activity and learning may help maintain and protect neurons at risk in aging and neurodegenerative disease via increased BDNF expression.

232 citations


Journal Article•DOI•
TL;DR: Despite the lack of correlations between temporally contiguous burst and pause combinations, mean BS decreased and pause duration increased as meals progressed, implying that this microstructural parameter is influenced in part by taste.
Abstract: A microstructural analysis of licking behavior in nondeprived and 23-hr food-deprived rats (n = 15) presented with various sucrose solutions (0.03-1.0 M) in daily single-bottle, 1-hr sessions was conducted. Food deprivation and concentration interacted to increase total licks. The effects of food deprivation and concentration on burst size (BS), burst number (BN), and other parameters varied as a function of the pause criterion (PC; 0.3-100 s) used to define licking bursts. A rationale for selecting a 1-s PC for further analysis is presented. Despite the lack of correlations between temporally contiguous burst and pause combinations, mean BS decreased and pause duration increased as meals progressed. At the 1-s PC, BS increased linearly with concentration, implying that this microstructural parameter is influenced in part by taste. Food deprivation did not affect BS but rather increased BN and proportionally extended the meal duration.

228 citations


Journal Article•DOI•
TL;DR: Characterizing the level of specificity of the human newborn's response to an odor experienced in utero is consistent with the hypothesis that the human fetus can detect and store the unique chemosensory information available in the prenatal environment and that this information becomes coupled with positive control of behavior.
Abstract: This study was aimed at characterizing the level of specificity of the human newborn's response to an odor experienced in utero. Three groups of breast-fed infants and 3 groups of bottle-fed infants were examined on Postnatal Day 3 for their differential head-turning response when exposed to paired-choice tests contrasting the odors of either familiar (f) amniotic fluid (AF) or nonfamiliar (nf) AF or either of these AF odors and a control (C) stimulus. In fAF versus nfAF tests, the infants oriented preferentially to the odor of fAF, regardless of their feeding regimen (i.e., of their postnatal reexposure to AF-like cues in maternal milk). The fAF or nfAF versus C tests showed that this response pattern was caused by a true positive orientation toward fAF and not by avoidance from nfAF odor. This highly selective neonatal response to fAF odor is consistent with the hypothesis that the human fetus can detect and store the unique chemosensory information available in the prenatal environment and that this information becomes coupled with positive control of behavior.

196 citations


Journal Article•DOI•
TL;DR: In this paper, the extent of conditioned fear and the levels of plasma corticosterone in rats, after context exposure at training and at different posttraining times (24 hr and 7 days), depended on the intensity of the unconditional stimulus (footshock).
Abstract: A role for corticosterone in the consolidation of contextual fear conditioning has previously been proposed. In this study, physiological evidence was found to support this view. The extent of conditioned fear and the levels of plasma corticosterone in rats, after context exposure at training and at different posttraining times (24 hr and 7 days), depended on the intensity of the unconditional stimulus (footshock). In each experimental session, a positive correlation was found between the magnitude of corticosterone levels and the fear-related behavioral inhibition exhibited in the context. Results support the involvement of corticosterone on the processes that occur during consolidation in determining the strength at which the contextual fear conditioning is stored as a long-term memory.

193 citations


Journal Article•DOI•
TL;DR: The results argue against the idea that the mnemonic contributions of the rhinal cortex and hippocampus are limited to object and spatial domains, respectively.
Abstract: Rhesus monkeys (Macaca mulatta) with lesions of the rhinal cortex or parahippocampal gyrus (made by aspiration) or hippocampus (made with ibotenic acid) and unoperated controls were tested on object discrimination and reversal, place discrimination and reversal, and spatial scene learning to determine the contribution of these temporal lobe structures to these forms of learning and memory. Rhinal cortex lesions produced a severe deficit in object reversal learning; hippocampal lesions produced a milder deficit. Monkeys with rhinal cortex removals and those with hippocampal lesions were equally impaired on spatial scene learning. None of the lesions impaired place discrimination or reversal. These results argue against the idea that the mnemonic contributions of the rhinal cortex and hippocampus are limited to object and spatial domains, respectively.

Journal Article•DOI•
TL;DR: It is suggested that the prelimbic-infralimbic cortices, but not the anterior cingulate cortex, are important in spatial working memory.
Abstract: The present study examined the effects of quinolinic acid lesions of the dorsal anterior cingulate and prelimbic-infralimbic cornices on spatial working memory and spatial discrimination using go/no-go procedures. All testing occurred in a 12-arm radial maze. In a working memory task, rats were allowed to enter 12 arms for a cereal reward. Three or 4 arms were presented for a 2nd time in a session, which did not result in a reward. In a spatial discrimination task, rats had successive access to 2 different arms. One arm always contained a reward, and the other never contained a reward. Prelimbic-infralimbic lesions impaired spatial working memory but only produced a transient spatial discrimination deficit. Dorsal anterior cingulate lesions did not induce a deficit in either task. These findings suggest that the prelimbic-infralimbic cortices, but not the anterior cingulate cortex, are important in spatial working memory.

Journal Article•DOI•
TL;DR: The results show that the dorsal hippocampus is one area that can mediate anxiogenic effects in the social interaction test, but the brain region mediating anxiolytic effects remains to be identified.
Abstract: In conditions generating moderate levels of anxiety in the social interaction test (low light, unfamiliar arena or high light, familiar arena), parenteral administration of nicotine had bimodal actions, low doses (0.01 and 0.1 mg/kg i.p.) had anxiolytic effects and high doses (0.5 and 1.0 mg/kg i.p.) had anxiogenic effects. In test conditions where anxiety was lowest (low light, familiar arena) and highest (high light, unfamiliar arena), nicotine was without effect after intraperitoneal or hippocampal administration. Thus, nicotine plays a modulatory role in which the activity of other neurotransmitters is crucial to its expression. After bilateral administration to the dorsal hippocampus, nicotine (0.1-8.0 microg) had anxiogenic effects in conditions of moderate anxiety; mecamylamine (30 ng) was silent in these conditions, indicating no intrinsic tone. Our results show that the dorsal hippocampus is one area that can mediate anxiogenic effects in the social interaction test, but the brain region mediating anxiolytic effects remains to be identified.

Journal Article•DOI•
TL;DR: After visual input was eliminated by blindfolding the rats, HD cells maintained direction-specific discharge, but their preferred firing directions became less stable, indicating that HD cells rely on a rapid learning mechanism to develop associations with landmark cues.
Abstract: Previous research has shown that head direction (HD) cells in both the anterior dorsal thalamus (ADN) and the postsubiculum (PoS) in rats discharge in relation to familiar, visual landmarks in the environment. This study assessed whether PoS and ADN HD cells would be similarly responsive to nonvisual or unfamiliar environmental cues. After visual input was eliminated by blindfolding the rats, HD cells maintained direction-specific discharge, but their preferred firing directions became less stable. In addition, rotations of the behavioral apparatus indicated that some nonvisual cues (presumably tactile, olfactory, or both) exerted above chance stimulus control over a cell's preferred firing direction. However, a prominent auditory cue was not effective in exerting stimulus control over a cell's preferred direction. HD cell activity also was assessed after rotation of a novel visual cue exposed to the rat for 1, 3, or 8 min. An 8-min exposure was enough time for a novel visual cue to gain control over a cell's preferred direction, whereas an exposure of 1 or 3 min led to control in only about half the sessions. These latter results indicate that HD cells rely on a rapid learning mechanism to develop associations with landmark cues.

Journal Article•DOI•
TL;DR: There was no evidence that performances differed with menstrual cycle phase, and results from younger women, combined with previous results from older women, may help establish the boundaries for hormonal influences on cognitive and motor-skill behavior.
Abstract: This study validated 6 cognitive and motor-skill tasks as sex-sensitive and used them to investigate whether women's performance changed across the menstrual cycle. Three putative female-advantage tasks and 3 putative male-advantage tasks were administered twice, at 6-week intervals, to young college women and men. Counterbalanced for order, women received the tests once during menstruation and once during the midluteal phase. The midluteal phase was determined by projection from day of ovulation, as verified by ovulation detection kits, and by confirmation of subsequent menstruation. Results revealed a significant sex difference for 5 of the 6 tasks. However, there was no evidence that performances differed with menstrual cycle phase. These results from younger women, combined with previous results from older women, may help establish the boundaries for hormonal influences on cognitive and motor-skill behavior.

Journal Article•DOI•
Graham Cousens1, Tim Otto•
TL;DR: Data support the notion that the basolateral amygdaloid complex participates in an enduring manner in the expression of conditioned freezing behavior elicited by both olfactory and contextual stimuli.
Abstract: The present study examined whether the basolateral amygdaloid complex (BLA) participates in the expression of fear conditioned to both an olfactory conditioned stimulus (CS) and the training context. In Experiment 1, pretraining excitotoxic lesions of the BLA abolished immediate postshock freezing, conditioned freezing to an olfactory CS, and conditioned freezing to the training context. Control experiments indicated that lesioned and sham-lesioned subjects did not differ in locomotor activity or in acquisition of a successive-cue odor discrimination task, suggesting that deficits in freezing behavior exhibited by BLA subjects were not due to an impairment in primary aspects of olfaction or to a general enhancement of locomotor activity. In Experiment 2, excitotoxic lesions of the BLA produced either 1 day or 15 days after olfactory fear conditioning abolished both odor-elicited and contextual freezing. Collectively, these data support the notion that the BLA participates in an enduring manner in the expression of conditioned freezing behavior elicited by both olfactory and contextual stimuli.

Journal Article•DOI•
TL;DR: It is demonstrated that less extensive cortical cholinergic deafferentation, produced by intracortical infusions of a relatively small concentration of 192 IgG-saporin, resulted in a significant impairment in sustained attention, but the administration of neither physostigmine nor FG 7142 benefited the performance of the animals.
Abstract: Rats with extensive lesions of cortical cholinergic afferents as a result of infusions of 192 IgG-saporin into the basal forebrain show persistent impairments in sustained attention performance (J. McGaughy, T. Kaiser, & M. Sarter, 1996). However, the administration of neither the cholinesterase inhibitor physostigmine nor the benzodiazepine receptor partial inverse agonist FG 7142 attenuated the lesion-induced impairments in performance. The present study demonstrated that less extensive cortical cholinergic deafferentation, produced by intracortical infusions of a relatively small concentration of 192 IgG-saporin, resulted in a significant impairment in sustained attention. However, the administration of neither physostigmine (0.01-0.1 mg/kg) nor FG 7142 (0.1-1.0 mg/kg) benefited the performance of the animals. Because neither compound selectively augments performance-associated increases in acetylcholine release from residual neurons, beneficial effects on cortical cholinergic deafferentation-based impairments in attention may remain limited.

Journal Article•DOI•
TL;DR: Analysis of freezing behavior in infant rhesus monkeys and their mothers suggested a link between basal cortisol levels and an animal's propensity to freeze, as well as a mechanism by which maternal experience may affect infants' cortisol levels.
Abstract: Freezing is an adaptive defensive behavior that is expressed in response to an imminent threat. In prior studies with rhesus monkeys, stable individual differences in animals' propensities to freeze have been demonstrated. To understand the factors associated with these individual differences, freezing behavior was examined in infant rhesus monkeys and their mothers, in conjunction with levels of the stress-related hormone cortisol. In both mothers and infants, basal cortisol levels were positively correlated with freezing duration. Additionally, the number of offspring a mother had was negatively correlated with her infant's cortisol level. These findings suggest a link between basal cortisol levels and an animal's propensity to freeze, as well as a mechanism by which maternal experience may affect infants' cortisol levels.

Journal Article•DOI•
TL;DR: In this article, the authors examined whether pairing a tone with activation of the nucleus basalis could induce receptive field (RF) plasticity in the waking guinea pig and, if so, whether it could be retained for 24 hours.
Abstract: Learning induces neuronal receptive field (RF) plasticity in primary auditory cortex. This plasticity constitutes physiological memory as it is associative, highly specific, discriminative, developes rapidly, and is retained indefinitely. This study examined whether pairing a tone with activation of the nucleus basalis could induce RF plasticity in the waking guinea pig and, if so, whether it could be retained for 24 hr. Subjects received 40 trials of a single frequency paired with electrical stimulation of the nucleus basalis (NB) at tone offset. The physiological effectiveness of NB stimulation was assessed later while subjects were anesthetized with urethane by noting whether stimulation produced cortical desynchronization. Subjects in which NB stimulation was effective did develop RF plasticity and this was retained for 24 hr. Thus, activation of the NB during normal learning may be sufficient to induce enduring physiological memory in auditory cortex. The search for the mechanisms of learning and memory continues to be a central problem in neuroscience. The approach of recording neurophysiological correlates of behavioral leaming is advantageous in potentially locating a site of (probably distributed) storage and in providing an approximation of the actual acquired information. A combination of neurophysiological correlates of behavioral learning with a controlled stimulation of designated circuits has the additional benefit of providing for tests of candidate mechanisms of a behaviorally induced neurophysiological index of information storage by determining whether direct activation of a designated brain circuit produces the same neurophysiological correlates as those that are induced during behavioral learning. However, there are actually very few neurophysiological correlates of behavioral learning that meet the criteria for indexing the storage of memories, particularly in the cerebral neocortex, which is generally agreed to be a major site of acquired information. In the case of associative declarative memory (as opposed to procedural or sensorimotor skill memory), these criteria include the following: The neurophysiological phenomenon must be (a) induced during normal leaming in behaving subjects, (b) associative, (c) highly specific to the information acquired, (d) induced very

Journal Article•DOI•
TL;DR: The cPAG plays a multifaceted role in parturient rats; it is involved in the mediation of nursing, sexual, aggressive, and fear behaviors.
Abstract: Severe impairment of the kyphotic nursing posture in lactating rats found previously after prepartum lesions of the caudal intercollicular periaqueductal gray (cPAG-x) was confirmed and was extended to a continuous 24-hr period. Litters of cPAG-x dams gained ~ 10% less weight postnatally than controls, which was in part related to their dams' compensatory prone nursing posture that was ineffective for milk letdown. Sexual proceptivity and receptivity (lordosis) during the postpartum estrus were virtually eliminated in subjects with relatively large bilateral cPAG lesions. The doubling of maternal attacks toward a male intruder after lesioning was also confirmed and was related to reduced tearfulness in an elevated plus-maze. Thus, the cPAG plays a multifaceted role in parturient rats; it is involved in the mediation of nursing, sexual, aggressive, and fear behaviors. During the early postpartum (PP) period, lactating rats are in physical contact with their litters for approximately

Journal Article•DOI•
TL;DR: Findings indicate that systemic injection of EPI increases release of NE in the amygdala and suggest that the effects are mediated in part by activation of brainstem neurons in the NTS that project to the amygdala.
Abstract: Several findings based largely on lesions and drug manipulations within the amygdala suggest that norepinephrine (NE) systems in the amygdala contribute to enhancement of memory processes by epinephrine (EPI). However, no studies to date have directly measured changes in the release of NE in the amygdala after EPI injection. In Experiment 1, in vivo microdialysis was used to assess amygdala NE release after systemic injection of saline, EPI (0.1 or 0.3 mg/kg), and administration of an escapable footshock (0.8 mA, 1 s). Both doses of EPI produced a significant elevation in NE release that persisted for up to 60 min. In Experiment 2, the local anesthetic lidocaine (2%) was infused (0.5 microl) into the nucleus of the solitary tract (NTS) immediately before injection of 0.3 mg/kg EPI. The EPI-induced elevation in amygdala NE release observed in Experiment I was attenuated by inactivation of the NTS. These findings indicate that systemic injection of EPI increases release of NE in the amygdala and suggest that the effects are mediated in part by activation of brainstem neurons in the NTS that project to the amygdala.

Journal Article•DOI•
TL;DR: Experiment 4 showed that shock onset contributes more to learning than does shock offset, and disrupting response-outcome contiguity by delaying the onset and offset of shock by 100 ms eliminated learning.
Abstract: Four experiments are reported that explore whether spinal neurons can support instrumental learning. During training, one group of spinal rats (master) received legshock whenever one hindlimb was extended. Another group (yoked) received legshock independent of leg position. Master, but not yoked, rats learned to maintain their leg in a flexed position, exhibiting progressively longer flexions as a function of training (Experiment 1). All subjects were then tested by applying controllable shock to the same leg (Experiment 2). Master rats reacquired the instrumental response more rapidly (positive transfer), whereas yoked rats failed to learn (a learned helplessness-like effect). Disrupting response-outcome contiguity by delaying the onset and offset of shock by 100 ms eliminated learning (Experiment 3). Experiment 4 showed that shock onset contributes more to learning than does shock offset.

Journal Article•DOI•
TL;DR: It is argued that ILn lesions disrupt remembering through their effects on the recurrent, feedback pathways that link functionally related areas of the basal ganglia and cortex.
Abstract: Lesions of the intralaminar thalamic nuclei (ILn), the medial wall (MW) area of prefrontal cortex, and the hippocampus were compared and found to have distinct effects on delayed matching-to-sample (DMS) and delayed non-matching-to-sample (DNMS) tasks based on different types of stimulus cues. Hippocampal lesions impaired DNMS trained in a radial arm maze but had little effect on DMS trained with retractable levers or olfactory DNMS. MW lesions affected the DMS task but had limited effects on olfactory DNMS and radial arm maze DNMS. ILn lesions resulted in a more generalized pattern of impairment for radial maze tasks and (in previous studies) for the DMS and olfactory DNMS tasks. Only the hippocampal lesion was associated with a delay-dependent impairment. It is argued that ILn lesions disrupt remembering through their effects on the recurrent, feedback pathways that link functionally related areas of the basal ganglia and cortex.

Journal Article•DOI•
TL;DR: Dorsal hippocampal cholinergic modulation of behavior in different tests of anxiety was investigated by direct injection of the muscarinic M1 and M2 receptor antagonists, pirenzepine and gallamine, and the nicotinic receptor antagonist mecamylamine, finding that M2 receptors in this brain region do not play a significant role in this behavioral test.
Abstract: Dorsal hippocampal cholinergic modulation of behavior in different tests of anxiety was investigated by direct injection of the muscarinic M 1 and M 2 receptor antagonists, pirenzepine and gallamine, and the nicotinic receptor antagonist mecamylamine. In the social interaction test, the anxiogenic effect of pirenzepine (30-100 ng) provided evidence for a tonic cholinergic anxiolytic action mediated by postsynaptic M 1 receptors. The anxiogenic action of mecamylamine (30 and 100 ng) was most likely mediated by its action of presynaptic nicotinic receptors to reduce acetylcholine release. Gallamine (10-1,000 ng) was without effect, suggesting that M 2 receptors in this brain region do not play a significant role in this behavioral test. On Trial I in the elevated plus-maze, the receptor antagonists were without any effect, but in those with a previous 5-min experience of the plus-maze pirenzepine and mecamylamine had anxiogenic effects in the dose range of 30-300 ng; gallamine (100 and 300 ng) was without significant effect.

Journal Article•DOI•
TL;DR: Meal patterns recorded before and after lesioning showed no change in total food intake, but a striking behavioral syndrome in which the lesioned rats took smaller meals 2-3 times as frequently and showed a similar change in drinking.
Abstract: Lesions of both dorsal and ventral hippocampus were produced by multiple infusions of the excitotoxin AMPA. Meal patterns recorded before and after lesioning showed no change in total food intake, but a striking behavioral syndrome in which the lesioned rats took smaller meals 2-3 times as frequently and showed a similar change in drinking. In addition, lesioned rats alternated more frequently between feeding and drinking during a single bout of ingestive behavior. There were no group differences in the satiety sequence that followed a meal. In an open field test, lesioned rats showed enhanced locomotion in the periphery and reduced rearing. An olfactory habituation-dishabituation task showed that the lesioned rats investigated olfactory stimuli less but dishabituation to a changed stimulus was normal. The data are discussed in terms of changes in behavioral switching or a possible interoceptive agnosia following hippocampal damage.

Journal Article•DOI•
TL;DR: PPI in Lewis rats is relatively unaffected by either a pharmacological or a developmental manipulation, both of which disrupt PPI in Sprague-Dawley and Fischer F344 rats.
Abstract: This study compared the interaction of strain with isolation rearing on startle reactivity, habituation, and prepulse inhibition (PPI) in male Lewis, Sprague-Dawley, and Fischer F344 rats tested as adults. Lewis and Fischer rats exhibited lower startle reactivity than Sprague-Dawley rats. Lewis rats displayed more rapid habituation than the other strains. Most important, isolation rearing produced deficits in PPI in both Sprague-Dawley and Fischer rats but had no effect in Lewis rats. By contrast, isolation rearing had no effect on startle reactivity or habituation. In a separate study, 0.5 mg/kg apomorphine disrupted PPI in Fischer but not in Lewis rats. Thus, PPI in Lewis rats is relatively unaffected by either a pharmacological or a developmental manipulation, both of which disrupt PPI in Sprague-Dawley and Fischer F344 rats.

Journal Article•DOI•
TL;DR: The findings suggest that the impairing effects of immediate posttraining sulpiride in the spatial task are due to interference with spatial water maze-specific consolidation processes involving the NA.
Abstract: A variety of nucleus accumbens (NA) manipulations induce deficits in spatial learning and memory tasks. It is not known, however, if these deficits reflect influences on memory or on other processes affecting performance. The experiments in this article were undertaken to examine the involvement of the NA in memory consolidation in a spatial task. Rats were given 1 training session in a spatial water maze immediately followed by intra-NA infusions of sulpiride or saline vehicle. A probe test 2 days later revealed an impairing effect of sulpiride on several retention measures. Sulpiride infused into the NA either 2 hr posttraining in the spatial task or immediately posttraining in a cued water maze task did not affect retention performance. These findings suggest that the impairing effects of immediate posttraining sulpiride in the spatial task are due to interference with spatial water maze-specific consolidation processes involving the NA.

Journal Article•DOI•
TL;DR: A pattern of results supports the view that cell bodies within the PBN are essential for the associative processes that govern CTA learning.
Abstract: Rats with extensive ibotenic acid lesions centered in the gustatory zone of the pontine parabrachial nucleus (PBN) failed to acquire a conditioned taste aversion (CTA) induced by lithium chloride (LiCl) toxicosis (Experiments 1 and 4). This deficit cannot be explained as an inability to either perceive or process gustatory information because lesioned rats that failed to acquire a CTA readily acquired a conditioned flavor preference (Experiment 2). Similarly, the CTA deficit cannot be attributed to an inability to experience or process visceral input because PBN-lesioned rats that failed to acquire a CTA successfully learned an aversion to a trigeminal stimulus, capsaicin, when paired with LiCl-induced illness (Experiment 3). This pattern of results supports the view that cell bodies within the PBN are essential for the associative processes that govern CTA learning.

Journal Article•DOI•
TL;DR: None of the lesions in either study affected the ability to learn a 2-choice odor discrimination using go/no-go procedures comparable with the DNMTS task.
Abstract: We conducted 2 studies to determine the importance of several brain systems for remembering odorants in a go/no-go delayed nonmatching-to-sample (DNMTS) task. In Experiment 1, impairments were observed for lesions of pyriform cortex or (to a lesser extent) the lateral internal medullary lamina of thalamus. Lesions of the entorhinal cortex or the mediodorsal (MDn) or the paracentral and centrolateral (PC-CL) thalamic nuclei did not affect DNMTS. In Experiment 2, an impairment comparable to the pyriform lesion was observed for a lesion of the intralaminar nuclei (PC-CL plus the central medial nucleus) but not for a larger lesion of MDn. None of the lesions in either study affected the ability to learn a 2-choice odor discrimination using go/no-go procedures comparable with the DNMTS task.

Journal Article•DOI•
TL;DR: Reward-related units were found that anticipated reward encounter, that responded during reward consumption, and that differentiated between high and low reward magnitude, consistent with the hypothesis that BLA neurons may provide the VS with reward-related information that could then be integrated with spatial information to ultimately affect goal-directed behavior.
Abstract: Previous research has shown that spatial, movement, and reward information is integrated within the ventral striatum (VS). The present study examined the possible contribution of the basolateral nuclei of the amygdala (BLA) to this interaction by examining behavioral correlates of BLA neurons while rats performed multiple memory trials on an 8-arm radial maze. Alternate arms consistently held 1 of 2 different amounts of reward. Recorded cells were correlated with motion, auditory input, space, and reward acquisition. Reward-related units were found that anticipated reward encounter, that responded during reward consumption, and that differentiated between high and low reward magnitude. This is consistent with the hypothesis that BLA neurons may provide the VS with reward-related information that could then be integrated with spatial information to ultimately affect goal-directed behavior.