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PubMed1985

Cognitive processing differences between obese and nonobese subjects.

Research in the area of human obesity has investigated a variety of factors believed to affect food intake. The present study measured free recall of food and nonfood words to explore the cognitive processing of food and nonfood stimuli by 60 obese and nonobese female subjects. Intentional learning conditions were employed to test the obesity compliancy effect, and incidental learning conditions were employed to control for the obesity compliancy effect while assessing recall. No significant memory differences were found. The findings imply that the obese and nonobese do not differ in their cognitive processing of food stimuli as measured by memory. More importantly, the study failed to demonstrate an obesity compliancy effect for memory. The obese and nonobese subjects did differ significantly in their weight fluctuation rating, and this finding was compared to Herman's restrained eating theory. Implications for future research and therapy in the area of human obesity are discussed.

Body Weight↗
PubMed1997

The effect of dizocilpine (MK-801) on conditional discrimination learning in the rat.

The effect of the non-competitive N-methyl-D-aspartate (NMDA)-receptor antagonist, dizocilpine (MK-801) on the acquisition and reversal of conditional tasks was investigated using a Y-maze. Dizocilpine-treated rats were severely impaired on acquisition of a visuo-spatial task and were unable to learn the reversal of this task. 'Worse than chance' performance by dizocilpine-treated (and saline-treated) rats at the beginning of reversal testing, which was given 24 h after achieving criterion on acquisition, indicated that dizocilpine-treated animals simultaneously exhibited good memory but impaired learning for the type of information required for this task. Dizocilpine-treated rats were unable to acquire a visuo-visual conditional discrimination and therefore could not be assessed on reversal of this task. These very substantial impairments were larger than those found in comparable experiments using non-conditional tasks.

Animals↗
PubMed2005

Effects of pentylenetetrazole-induced status epilepticus on behavior, emotional memory and learning in immature rats.

Status epilepticus (SE) can be harmful to the developing brain. Our knowledge of the emotional and behavioral consequences of generalized SE in developing animals remains limited. Therefore, we investigated the short- and long-term effects of pentylenetetrazole (PTZ)-induced SE on emotional memory and learning and behavioral parameters in immature rats. SE was induced in 16- to 20-day-old rats (P16-P20) using intraperitoneal injections of PTZ (n=21); control rats received saline (n=10). All animals were tested using an elevated T-maze and open-field test 2, 14, 30, and 180 days after SE, to evaluate emotional memory and learning and behavior. Anxiety levels decreased 2 and 14 days after SE, and conditioned learning of PTZ-treated immature rats was better than that of the control rats. These results indicate that a decreased anxiety level facilitates conditioned learning. Behavioral changes are transient, and no emotional memory or learning deficits occur following PTZ-induced SE in immature rats.

Animals↗
PubMed1999

Reading and spelling disorders: clinical features and causes.

Developmental dyslexia (specific reading and specific spelling disorder) is thought to stem from specific features in cognitive processing strongly related to biological maturation of the central nervous system which interact with non-biological learning conditions. The specific learning disorder should not be accounted for by mental age, gross neurological deficits, emotional disturbances or inadequate schooling. As a clinical guideline, the child's level in reading and spelling must be significantly below that expected for the population of children of the same mental age. The persistence rate is high and dyslexia is often associated with psychiatric problems. The etiology is not known. From the biological point of view, dyslexia is supposed to have a neurological basis. Neuroanatomical, neurophysiological, and neuropsychological correlates have been studied by means of autopsy, brain imaging, neurophysiological and neuropsychological methods. There is good evidence that dyslexia is determined by heritable cognitive components of reading and spelling processing. Experimental research focuses on characteristics of brain structure and cognitive skills related to the central nervous systems of auditory-phonological and visual information processing.

Brain↗
PubMed1996

Huntington's disease and eyeblink classical conditioning: normal learning but abnormal timing.

On the basis of what is known about the neural circuitry essential or normally involved in eyeblink classical conditioning (EBCC), the pattern of neurodegeneration in Huntington's disease (HD) would not appear to interfere with this type of learning. HD causes severe atrophy of the basal ganglia and thinning and shrinkage of the cerebral cortex. However, the hippocampus and hippocampal cholinergic system remain relatively intact, as does the cerebellum. Because the brain circuitry engaged in EBCC is neither lesioned nor disrupted in HD, it was predicted that HD patients would perform like normal control subjects in the 400-ms delay EBCC paradigm. Performance of seven patients with HD was compared to age-matched normals, with two control subjects matched to each HD patient. There were no differences in production of conditioned responses (CRs) between HD patients and normal control subjects, but the timing of the CR was abnormal in HD. Comparisons of HD patients to patients with other neurodegenerative diseases (probable Alzheimer's disease (pAD) and Down syndrome (DS) over the age of 35 with presumed Alzheimer-like neuropathology) and to patients with cerebellar lesions demonstrated significantly better EBCC performance in HD. Results suggest that the ability to acquire CRs is normal in HD, but the striatum may have some role in optimizing the timing of the CR.

Adult↗
PubMed1999

The effect of excitotoxic hippocampal lesions on simple and conditional discrimination learning in the rat.

The effect of excitotoxic lesions of the hippocampus on acquisition and reversal of simple and conditional tasks was investigated using a Y-maze. Hippocampal-lesioned rats were severely impaired on acquisition and reversal of a conditional visuo-spatial task (where different pairs of visually distinctive choice arms indicated whether a left or right arm choice was correct on that trial) and were unable to acquire a visuo-visual conditional discrimination (where the appearance of the start arm indicated which of the visually distinctive choice arms was correct irrespective of their left/right position). They were not impaired on acquisition or reversal of a simple spatial left/right discrimination task (where all arms had the same visual appearance) nor on acquisition of a visual discrimination (where the correct, visually distinctive, choice arm varied in its left/right position). Hippocampal-lesioned rats were, however, impaired on reversal of this visual discrimination task and on acquisition and reversal of another visual discrimination task in which the visually distinctive choice arms were less different from each other than in the first version of this task. The degree of impairment in the lesioned rats was related to task difficulty for the sham-operated rats and was not specific to tasks requiring spatial choices, visual discrimination or conditional responding. The impairment on conditional tasks was greater than the impairment on those non-conditional tasks which happened to be matched for task difficulty for the sham-operated rats, suggesting that the conditional demand may target the function of the hippocampus rather closely. Statistically worse than chance performance by hippocampal-lesioned (and sham-operated) rats at the beginning of reversal testing, which was given 24 h after achieving criterion on acquisition of that task, indicated that hippocampal-lesioned rats simultaneously exhibited good memory but impaired learning for the type of information required for those tasks.

Animals↗
PubMed1997

Task difficulty and the specificity of perceptual learning.

Practising simple visual tasks leads to a dramatic improvement in performing them. This learning is specific to the stimuli used for training. We show here that the degree of specificity depends on the difficulty of the training conditions. We find that the pattern of specificities maps onto the pattern of receptive field selectivities along the visual pathway. With easy conditions, learning generalizes across orientation and retinal position, matching the spatial generalization of higher visual areas. As task difficulty increases, learning becomes more specific with respect to both orientation and position, matching the fine spatial retinotopy exhibited by lower areas. Consequently, we enjoy the benefits of learning generalization when possible, and of fine grain but specific training when necessary. The dynamics of learning show a corresponding feature. Improvement begins with easy cases (when the subject is allowed long processing times) and only subsequently proceeds to harder cases. This learning cascade implies that easy conditions guide the learning of hard ones. Taken together, the specificity and dynamics suggest that learning proceeds as a countercurrent along the cortical hierarchy. Improvement begins at higher generalizing levels, which, in turn, direct harder-condition learning to the subdomain of their lower-level inputs. As predicted by this reverse hierarchy model, learning can be effective using only difficult trials, but on condition that learning onset has previously been enabled. A single prolonged presentation suffices to initiate learning. We call this single-encounter enabling effect 'eureka'.

Humans↗
PubMed1979

Conditioned-reflex learning of normal juvenile and adult rats exposed to action of substance P and of an SP analogue.

The actions of both Substance P, a potential neurotransmitter or modulator and of a shortened analogue on learning and memorizing processes are reported in this paper. Sixty male rats, aged 22, 14, and 10 weeks, were exposed to Substance P (Arg-Pro-Gln-Gln-Phe-Gly-Leu-MetNH2) and to a shortened hexapeptide analogue (Lys-Phe-Ile-Gly-Leu-MetNH2), doses being 250 microgram/kg and 500 microgram/kg, to test their action upon learning and memorizing processes, such as acquisition, retention, and ecphoration, by means of a conditioned-reflex locomotor defense method. Response time of all three age groups as well their retention and ecphoration were normal under the impact of hexapeptide. The effects of Substance P were decline of retention in juvenile animals (10 weeks of age) and coupling between the processes of central-nervous afference synthesis, on the one hand, and the efference integral related to motoricity, on the other, in both juvenile and adult animals. A retention test was conducted and showed that discontinuation of application of either peptide over 4 d was followed by complete inhibition of ecphoration. Learning and memorising processes were restorable by reapplication of the peptides. These findings were defined as "state-dependent learning". Only slight variation under the impact of both Substance P and the analogue was recordable by non-invasive measurement of systolic blood pressure.

Aging↗
PubMed2001

Genetic evidence for noradrenergic control of long-term memory consolidation.

Memory formation involves dynamic interactions among many brain structures and their linking pathways. The noradrenaline (NA) system in the CNS plays an important role in a wide variety of neurological and psychological functions. Alteration in the NA system is implicated in the pathological states of some neuropsychiatric disorders. Tyrosine hydroxylase (TH) is the initial and rate-limiting enzyme for the biosynthesis of catecholamines. The regulatory mechanism of the TH reaction is generally considered to play a key role in controlling the catecholaminergic actions. Mice heterozygous for the mutation of the gene encoding TH exhibit the reduced TH activity in tissues. These mice have a moderate reduction in NA accumulation and release in brain regions. The mutant mice exhibit deficits in the water-finding task associated with latent learning performance, suggesting the impairment in memory formation. Spatial learning performance measured by the water maze task is normal in the mutants. However, they display deficits in long-term memory formation of conditioned learning evaluated with three distinct behavioral paradigms, including active avoidance, cued fear conditioning, and conditioned taste aversion, without affecting short-term memory. These memory deficits are restored by the drug-induced stimulation of NA activity at the postconditioning phase. Analysis of the mutant mice indicates that the central NA system is essential for the consolidation process in long-term memory of conditioned learning. The process appears to be implicated in the NA activity in the cerebral cortex and/or amygdaloid complex.

Amygdala↗
PubMed1996

Learning test on expressive phonetic symbolism.

We asked 249 students to learn three different vocabulary lists, each containing 19 word pairs (Indonesian, Suaheli, and one mixed list composed of items from 13 different languages) in three versions: "normal" (factual classification), "reversed" (opposite classification), and "disarranged" (word meaning imputed in a completely different dimension). That those word-pairs with "normal" classification would lead to best learning was not generally confirmed but was corroborated for favourable learning conditions (items at the top of the list, items at the beginning of the questioning, easy to learn items), whereas the effect of phonetic symbolism combined with "normal" presentation proved rather abstruse. We assume that in the latter cases encoding worked rather automatically, and additional information used energy. The encoding process uses so much energy that further information is not useful under unfavourable learning conditions. We found a relation between performance on each mode of presentation and sex. Independent of presentation mode, learning depends on age, sex, membership in a seminar, and subject matter studied. Therefore, we examined the distribution of these in our nine groups (three languages by three versions). Since no statistically relevant differences in distribution arose, our results do not have to be qualified.

Adult↗
PubMed1975

Studies in the neurophysiology of learning: IX. Conditioning of evoked potentials due to cerebral stimulation.

The hypothesis to be tested was that if characteristic undulatory evoked potentials could be produced by electrical stimulation of the lateral hypothalamus, sensory stimuli originally neutral should evoke such potentials, if only of smaller amplitude. The results of experiments on four albino rats are reported. Stimulation of the lateral hypothalamus by electrical current at 200 biphasic rectangular pulses per second results in 7-12 cycles-per-second undulations persisting for about .5 second and derivable from several regions of the cerbrum. By means of the Pavlovian paradigm, it was possible to condition these to an auditory and to a visual stimulus. The conditioned undulations had smaller amplitudes, did not persist as long to CS as to US, and were characterized by considerable lability. From 100 to 300 CS-US pairings were required.

Animals↗
PubMed1994

Conditional associative learning is impaired in cerebellar disease in humans.

Eight patients with lesions restricted to the cerebellum were compared with a total of 25 age-matched controls on a reaction time (RT) task allowing the recording of simple and choice RTs as well as RTs to abstract visual patterns signifying the particular movement to be performed. In all conditions the actual movements required (either a left or a right button press) remained the same, but the cognitive requirements of the task varied. In the abstract patterns condition, the significance of the various patterns with regard to the required movement had to be learned by the subjects. The patients with cerebellar lesions were particularly impaired in this condition. It is concluded that the cerebellum is involved not just in the timing of movements but also in the decision process as to which movement should be performed under particular circumstances.

Adult↗
PubMed2006

Differential hippocampal and prefrontal-striatal contributions to instance-based and rule-based learning.

It is a topic of current interest whether learning in humans relies on the acquisition of abstract rule knowledge (rule-based learning) or whether it depends on superficial item-specific information (instance-based learning). Here, we identified brain regions that mediate either of the two learning mechanisms by combining fMRI with an experimental protocol shown to be able to dissociate both learning mechanisms. Subjects had to learn object-position conjunctions in several trials and blocks. In a learning condition, either objects (Experiment 1) or positions (Experiment 2) were held constant within-blocks. In contrast to a control condition in which object-position conjunctions were trial-unique, a performance increase within and across-blocks was observed in the learning condition of both experiments. We hypothesized that within-block learning mainly relies on instance-based processes, whereas across-block learning might depend on rule-based mechanisms. A within-block parametric fMRI analysis revealed a learning-related increase of lateral prefrontal and striatal activity and a learning-related decrease of hippocampal activity in both experiments. By contrast, across-block learning was associated with an activation modulation in distinct prefrontal-striatal brain regions, but not in the hippocampus. These data indicate that hippocampal and prefrontal-striatal brain regions differentially contribute to instance-based and rule-based learning.

Adult↗