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PubMed1996

5-HT2 receptor involvement in conditioned olfactory learning in the neonate rat pup.

These experiments addressed the role of 5-HT2 receptors in conditioned olfactory learning. Ritanserin, a 5-HT2A/2C antagonist, was injected subcutaneously into postnatal day (PND) 7 pups before or after conditioned olfactory training to a peppermint odor. When the pups were tested for olfactory preference on PND 8, those injected with ritanserin before training failed to acquire an odor preference whereas those injected after training learned. This suggested that the 5-HT2 receptor is required only in the acquisition of conditioned olfactory learning. Injection of ritanserin directly into the olfactory bulb before training also blocked preference for the peppermint odor. In pups that had depletion of the 5-HT input to the bulb, subcutaneous injection of a 5-HT2A/2C agonist was sufficient to maintain conditioned olfactory learning, confirming the importance of 5-HT in learning.

Animals↗
PubMed2003

Conditional discrimination learning in patients with bilateral medial temporal lobe amnesia.

The ability of bilateral medial temporal lobe amnesic patients (MT; n=8) and normal participants (NC; n=8) to acquire a conditional discrimination in trace and delay eyeblink conditioning paradigms was investigated. Experiment 1 assessed trace conditional discrimination learning by using a light conditional stimulus (S+/S-) and tone conditioned stimulus (CS) separated by a 1-s trace. NCs responded differentially on S+ trials (mean percent conditioned responses=66) versus S- trials (30). Whereas MTs were impaired in their acquisition of the conditional discrimination (S+ =51, S- =43). In Experiment 2, the temporal separation was eliminated. NCs acquired the conditional discrimination (S+ =70, S- =29). MTs were unable to respond differentially (S+ =42, S- =37). The findings indicate that the hippocampal system is essential in acquiring a conditional discrimination, even in a delay paradigm.

Adult↗
PubMed1998

Serotonin plays a permissive role in conditioned olfactory learning induced by norepinephrine in the neonate rat.

This study examined the role of serotonin (5-hydroxytryptamine; 5-HT) in conditioned olfactory learning in the rat pup. By injecting various combinations of the 5-HT(2A/2C) receptor agonist, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), and the beta adrenoceptor agonist, isoproterenol, we observed that isoproterenol alone acted as an unconditioned stimulus (US) to induce learning, as reported previously, whereas DOI alone did not induce learning. DOI combined with isoproterenol produced a leftward shift in the effective US dose such that suboptimal isoproterenol was effective, and previously optimal levels of isoproterenol were ineffective. Thus, 5-HT plays a facilitative but not an obligatory role in conditioned olfactory learning in the neonate rat.

Animals↗
PubMed1998

Prefrontal cortex and caudate nucleus in conditional associative learning: dissociated effects of selective brain lesions in rats.

Rats with lesions to prefrontal cortex (PFC) or caudate nucleus (CN) were compared on tests of conditional associative learning (CAL) that placed varying demands on conditional rule learning and working-with-memory operations that are essential for response selection. Damage to either structure impaired performance, but the respective deficits resulted from disruption of different processes. CN lesions produced a consistent learning deficit that was thought to reflect a basic impairment in forming stimulus-response (S-R) associations. The behavior of PFC rats was more variable and depended on task requirements. When S-R learning or response selection was relatively easy, the PFC was not critical. However, when either component was made more difficult, thus requiring the contribution of strategic processes, PFC damage produced profound impairments. In addition to clarifying the roles of the PFC and CN in CAL, the results provide further evidence that multiple brain regions participate in relatively simple behavioral tasks and that their respective contributions can be dissociated.

Animals↗
PubMed1998

The effect of right and left hemispheric lesions on effortful and automatic memory tasks.

The effect of lateralised cerebral damage on two memory tasks-free recall of words and memory of their temporal order-was investigated under intentional, incidental, and ''true incidental'' learning conditions. Ten Right Brain Damaged patients (RBD), 10 Left Brain Damaged patients (LBD), as well as 15 age-matched and 15 younger control individuals, participated in this study. It was hypothesised that effortful and automatic memory processes involve predominantly the left and right cerebral hemispheres, respectively. Automaticity was defined either by the learning conditions (i.e. incidental-automatic and intentional-effortful) or by the type of task (i.e. temporal-order-automatic and free-recall-effortful) regardless of the learning conditions. In the free recall task the RBD group outperformed the LBD group under all learning conditions. In the temporal order task, the RBD group performed worse than normal controls under all learning conditions while the LBD group performed more poorly than matched controls in the intentional and incidental but not in the ''true incidental'' learning condition. The results are discussed in terms of the relationship between effortful and automatic memory processes and cerebral lateralisation.

Journal Article↗
PubMed1987

Conditional associative learning in drug-free schizophrenic patients.

The performance on spatial and nonspatial associative learning tasks was tested in a sample of male drug-free DSM III-diagnosed schizophrenic patients and in a closely matched normal control group. Schizophrenics showed a worse performance on both versions of the task, but especially on the nonspatial one. A significant correlation was observed between some indices of the nonspatial task and the scores on two subscales (affective flattening and anhedonia) of the scale for the assessment of negative symptoms by Andreasen. These results are consistent with the hypothesis of a dysfunction of dorsolateral prefrontal cortex in schizophrenia and with the postulated linkage between such dysfunction and negative schizophrenic symptomatology.

Adult↗
PubMed2000

Deficit in conditional visuomotor learning by local infusion of bicuculline into the ventral prefrontal cortex in monkeys.

To explore the role of the ventral prefrontal cortex (PFv) in conditional visuomotor learning, we infused locally bicuculline, a GABAergic antagonist, into the PFv of two monkeys, well trained on a two-problem visuomotor task. The task required the monkeys to execute one of two motor actions (moving a handle to the left or to the right) in response to one of two familiar visual patterns (circle or triangle). The two patterns mapped 1:1 onto the two motor actions: for each pattern one and only one motor action was scored, correct and reinforced. In contrast to these sessions with familiar patterns, in the learning sessions the monkeys were presented with one or two novel patterns and required to learn the arbitrarily determined associations between these patterns and the two motor actions. We found that bilateral infusion of bicuculline into PFv dramatically impaired the monkeys' ability to learn novel pattern-response associations: the trials and errors to criterion (90% correct) increased significantly. The errors were mainly an inability to apply 'Win-Stay', 'Lose-Shift' and 'Change-Shift' strategies. There was no effect on the monkeys' performance in responding to familiar patterns. Similar infusion of bicuculline into the dorsal prefrontal cortex was without effect on either novel-pattern learning or familiar-pattern performance. We conclude that the ventral prefrontal cortex is necessary for learning new visuomotor associations, but has less importance, if any, for performing pre-established ones.

Animals↗
PubMed2004

Conditional-associative learning in eating disorders: a comparison with OCD.

The acquisition of conditional associations using neutral and individually threatening verbal stimuli was assessed in 16 females with anorexia nervosa (AN), obsessive-compulsive disorder (OCD), bulimia nervosa and normal controls, respectively. Groups did not differ in terms of age, sex, intelligence, depression, verbal memory and verbal fluency measures. Patients and controls were widely comparable on tests assessing neuropsychological functioning. In the conditional-associative learning (CAL)-task only anorectic and OCD-patients displayed an impaired performance with neutral material but not with individually threatening material. Such a deficit was not evident in bulimics or in normal controls. These findings support the assumptions from functional neuroimaging investigations in AN and OCD and provide evidence that obsessive and compulsive behavior could have its origin within common neurobiological dysfunctions. The CAL possibly serves as a functional correlate of a neurophysiological dysfunction in obsessive-compulsive spectrum disorders.

Adolescent↗
PubMed2004

Afferent and efferent connections of the parvicellular subdivision of iNTS: defining a circuit involved in taste aversion learning.

Conditioned taste aversion (CTA) expression is associated with strong increases in Fos-like immunoreactivity (FLI) in a region of the brainstem identified as the parvicellular subdivision of the intermediate nucleus of the solitary tract (iNTSpc). To identify the projections to and from cells in iNTSpc which display strong FLI in response to expression of a CTA, anterograde and retrograde tract tracing was used. When appropriate, tract tracing was combined with double labeling for FLI in animals which received CTA training as well as tracer injections and were re-exposed to the CS taste. With respect to afferent projections, iNTSpc receives a strong, direct, ipsilateral projection from amygdala and the distribution of the fiber terminals yields a striking match to that of cells expressing FLI after CTA expression. As for efferent projections, these cells in iNTSpc are characterized by a mixed, rather than homogeneous, projection pattern. Targets of these cells include pons and forebrain as well as local medullary sites, all of which are known to be involved in gastrointestinal function. Thus, activation of these cells may provide a circuit through which gastrointestinal/visceral responses are coordinated as a component of the conditioned aversion.

Afferent Pathways↗
PubMed1988

GABAergic modulation of memory with regard to passive avoidance and conditioned suppression task in mice.

The role of GABAergic neuronal system in learning and memory was investigated using the step-down typed passive avoidance and rapidly learned conditioned suppression tasks in mice. GABA antagonists, picrotoxin and bicuculline, or a GABA synthesis inhibitor, 3-mercaptopropionic acid (3-MP), were administered just after the training test. All of these drugs caused amnesia: they shortened the step-down latency (SDL) and attenuated the conditioned suppression of motility in the retention test conducted 24 h after the administration. Furthermore, we investigated the effect of GABA receptor agonists, muscimol and baclofen, or a GABA transaminase inhibitor, aminooxyacetic acid (AOAA), on these amnesia models. GABA agonists showed an antiamnesic action as follows: in the passive avoidance task, 1) picrotoxin-induced amnesia was antagonized by muscimol, baclofen and AOAA. 2) Bicuculline-induced amnesia was antagonized by muscimol and AOAA but not by baclofen. 3) 3-MP-induced amnesia was antagonized only by muscimol. 4) In the rapidly learned conditioned suppression task, picrotoxin-, bicuculline- and 3-MP-induced amnesia were antagonized by muscimol, baclofen and AOAA. These results suggest that the GABAergic neuronal system plays an important role in the memory retention of passive avoidance and rapidly learned conditioned suppression tasks.

4-Aminobutyrate Transaminase↗
PubMed2005

Limitations to the spacing effect: demonstration of an inverted u-shaped relationship between interrepetition spacing and free recall.

The spacing effect refers to the finding that memory for repeated items improves when the interrepetition interval increases. To explain the spacing effect in free-recall tasks, a two-factor model has been put forward that combines mechanisms of contextual variability and study-phase retrieval (e.g., Raaijmakers, 2003; Verkoeijen, Rikers, & Schmidt, 2004). An important, yet untested, implication of this model is that free recall of repetitions should follow an inverted u-shaped relationship with interrepetition spacing. To demonstrate the suggested relationship an experiment was conducted. Participants studied a word list, consisting of items repeated at different interrepetition intervals, either under incidental or under intentional learn instructions. Subsequently, participants received a free-recall test. The results revealed an inverted u-shaped relationship between free recall and interrepetition spacing in both the incidental-learning condition and the intentional-learning condition. Moreover, for intentionally learned repetitions, the maximum free-recall performance was located at a longer interrepetition interval than for incidentally learned repetitions. These findings are interpreted in terms of the two-factor model of spacing effects in free-recall tasks.

Humans↗
PubMed1996

The effects of lesions to the mammillary region and the hippocampus on conditional associative learning by rats.

Rats with extensive lesions to the mammillary body region, the hippocampus, or rats which had received a control operation were trained postoperatively on two visuo-spatial conditional associative learning tasks in which they had to learn to associate spatial cues with particular visual/auditory stimuli. The animals were subsequently trained on a spatial working memory task, the eight-arm radial maze. Rats with lesions to the mammillary body region were able to acquire the conditional associative learning tasks at a rate comparable to that of operated control animals, whereas those with hippocampal lesions were not. By contrast, rats with a lesion of the mammillary body region or the hippocampus were significantly impaired in comparison with the operated control animals in the radial maze. The findings suggest that lesions to the mammillary body region impair spatial working memory without affecting the capacity to associate particular exteroceptive cues with spatial locations.

Animals↗
PubMed2002

Dissociated conditional-associative learning in anorexia nervosa.

This study assessed the acquisition of conditional-associations using neutral and individually threatening nouns in 16 females with anorexia nervosa (AN), 16 females with bulimia nervosa (BN) and 16 normal controls (NC). Groups did not differ in terms of age, sex, handedness, depression, intelligence, verbal memory and verbal fluency measures. Furthermore, patients and controls were widely comparable on any test assessing neuropsychological functioning. In the conditional-associative learning (CAL) task, anorexic patients displayed an impaired performance with neutral material but not with individually threatening material. Such a deficit was not evident in bulimics or in normal controls. Only anorexics showed a dissociation in the CAL of material with different emotional valence. These findings support the assumptions from functional neuroimaging investigations in AN and justify the assignment of this disorder to the obsessive-compulsive spectrum disorders.

Adolescent↗
PubMed2002

Fornix transection impairs conditional visuomotor learning in tasks involving nonspatially differentiated responses.

Rhesus monkeys learned a series of conditional visuomotor associations involving two-dimensional "objects" that instructed one of three responses: tapping a touch screen, steady contact with the screen for a brief period, or steady contact for a longer period. Relative to controls, fornix-transected monkeys were impaired in the acquisition of new associations and in the retention of preoperatively learned ones. These findings challenge the view that the hippocampal system participates in associative learning only when spatial information is relevant to either the stimulus or the response.

Animals↗
PubMed2000

Arbitrary associations between antecedents and actions.

The arbitrary linkage of sensory cues to actions and goals represents one of the most-flexible capabilities in the behavioral repertoire of mammals. This ability has been termed 'conditional motor learning', 'conditional discrimination' or, more recently, 'arbitrary visuomotor mapping'. Unlike other forms of visuomotor guidance, in arbitrary mapping the location of the sensory cue lacks any systematic spatial relationship with the action or its goal. Recent work has identified much of the neural network that underlies this behavior. It consists of parts of the frontal cortex, hippocampal system and basal ganglia, each of which has neurons whose activity undergoes systematic evolution during learning.

Animals↗
PubMed2004

Memory priming and trial spacing effects in Pavlovian learning.

Conditioning trials that are massed in time produce less conditioning than those that are spaced in time. Four experiments with rat subjects examined whether a recent conditioning trial interferes with conditioning on the next trial by temporarily "priming" information in short-term memory (e.g., Wagner, 1978, 1981). We used appetitive conditioning procedures in which priming trials preceded target trials by 60 sec. When the priming trials were nonreinforced presentations of a conditioned stimulus (CS), the CS had to be the same CS as the one on the target trial to interfere with conditioning. When priming trials were actual CS-unconditioned stimulus (US) pairings, the CS identity did not matter, the US was the event that interfered with conditioning on the next trial. Reinforced trials reduced performance in a way that did not depend on context blocking. The results suggest that CS and US priming effects do contribute to conditioning deficits observed with massed trial procedures. The results are consistent with Wagner's (1981) "sometimes opponent process," or SOP, model, although a result that is paradoxical for the model suggests that recent USs may have motivational as well as memory effects.

Analysis of Variance↗
PubMedDate not supplied

The effect of L-tryptophan on conditioned reflex learning and behavior in rats with experimental pathology of the thyroid gland.

The effects of L-tryptophan on conditioned reflex learning and behavior were studied in male rats with deficient and excess thyroid hormones levels. The learning process was studied using a model consisting of a conditioned active avoidance response; animal behavior was assessed in an open field test. These studies showed that in conditions of thyroid hormone deficiency. L-tryptophan had positive effects on the acquisition and reproduction of the active avoidance reflex, restoring the ability of the animals to learn actively; L-tryptophan increased investigative activity in the open field test. In conditions of increased thyroid hormone levels, L-tryptophan reversed the mild stimulating effects of thyroid hormones on the processes of developing and performing the active avoidance habit, and increased investigative activity, but decreased the amount of grooming.

Animals↗