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PubMed2004

Altered representation of the spatial code for odors after olfactory classical conditioning; memory trace formation by synaptic recruitment.

In the olfactory bulb of vertebrates or the homologous antennal lobe of insects, odor quality is represented by stereotyped patterns of neuronal activity that are reproducible within and between individuals. Using optical imaging to monitor synaptic activity in the Drosophila antennal lobe, we show here that classical conditioning rapidly alters the neural code representing the learned odor by recruiting new synapses into that code. Pairing of an odor-conditioned stimulus with an electric shock-unconditioned stimulus causes new projection neuron synapses to respond to the odor along with those normally activated prior to conditioning. Different odors recruit different groups of projection neurons into the spatial code. The change in odor representation after conditioning appears to be intrinsic to projection neurons. The rapid recruitment by conditioning of new synapses into the representation of sensory information may be a general mechanism underlying many forms of short-term memory.

Animals↗
PubMed1996

A primate genesis model of focal dystonia and repetitive strain injury: I. Learning-induced dedifferentiation of the representation of the hand in the primary somatosensory cortex in adult monkeys.

In this study we tested a neuroplasticity/learning origins hypothesis for repetitive strain injuries (RSIs), including occupationally induced focal dystonia. Repetitive movements produced in a specific form and in an appropriate behavioral context cause a degradation of the sensory feedback information controlling fine motor movements, resulting in the "learned" genesis of RSIs. Two adult New World owl monkeys were trained at a behavioral task that required them to maintain an attended grasp on a hand grip that repetitively and rapidly (20 msec) opened and closed over short distances. The monkeys completed 300 behavioral trials per day (1,100 to 3,000 movement events) with an accuracy of 80 to 90%. A movement control disorder was recorded in both monkeys. Training was continued until the performance accuracy dropped to below 50%. We subsequently conducted an electrophysiologic mapping study of the representations of the hand within the primary somatosensory (SI) cortical zone. The hand representation in the true primary somatosensory cortical field, SI area 3b, was found to be markedly degraded in these monkeys, as characterized by (1) a dedifferentiation of cortical representations of the skin of the hand manifested by receptive fields that were 10 to 20 times larger than normal, (2) the emergence of many receptive fields that covered the entire glabrous surface of individual digits or that extended across the surfaces of two or more digits, (3) a breakdown of the normally sharply segregated area 3b representations of volar glabrous and dorsal hairy skin of the hand, and (4) a breakdown of the local shifted-overlap receptive field topography of area 3b, with many digital receptive fields overlapping the fields of neurons sampled in cortical penetrations up to more than four times farther apart than normal. Thus, rapid, repetitive, highly stereotypic movements applied in a learning context can actively degrade cortical representations of sensory information guiding fine motor hand movements. This cortical plasticity/learning-based dedifferentiation of sensory feedback information from the hand contributes to the genesis of occupationally derived repetitive strain injuries, including focal dystonia of the hand. Successful treatment of patients with RSI will plausibly require learning-based restoration of differentiated representations of sensory feedback information from the hand.

Animals↗
PubMed1983

[Teaching and learning in ophthalmology].

The acoustic era is being transformed ever more rapidly into the audiovisual era. This development is also having an increasing effect on training methods in medicine. In ophthalmological training especially, "teaching to see" plays a decisive role. Every newcomer to the specialty first has to learn how to "see" correctly, to judge three-dimensional relationships. The dynamic processes in the retinal and choroidal circulation can easily be demonstrated to students and young ophthalmologists by fluorescein angiography and TV fundus photography. This study illustrates the importance of space and time and shows how they can be integrated into ophthalmological training.

Humans↗
PubMed2001

Neurobiology of Pavlovian fear conditioning.

Learning the relationships between aversive events and the environmental stimuli that predict such events is essential to the survival of organisms throughout the animal kingdom. Pavlovian fear conditioning is an exemplar of this form of learning that is exhibited by both rats and humans. Recent years have seen an incredible surge in interest in the neurobiology of fear conditioning. Neural circuits underlying fear conditioning have been mapped, synaptic plasticity in these circuits has been identified, and biochemical and genetic manipulations are beginning to unravel the molecular machinery responsible for the storage of fear memories. These advances represent an important step in understanding the neural substrates of a rapidly acquired and adaptive form of associative learning and memory in mammals.

Amygdala↗
PubMed2004

Typicality effects in contingency-shaped generalized equivalence classes.

Two experiments were conducted using match-to-sample methodologies in an effort to model lexical classes, which include both arbitrary and perceptual relations between class members. Training in both experiments used a one-to-many mapping procedure with nonsense syllables as samples and eight sets of abstract stimuli as comparisons. These abstract stimuli differed along a number of dimensions, four of which were critical to the experimenter-defined class membership. Stimuli in some comparison sets included only one of the class-defining features, but stimuli in other sets included two, three, or all four of the critical features. After mastery of the baseline training, three types of probe tests were conducted: symmetry, transitivity/equivalence, and novel probe tests in which the training nonsense syllables served as samples, and comparisons were novel abstract stimuli that included one or more of the class-defining features. Symmetry and transitivity/equivalence probe tests showed that the stimuli used in training became members of equivalence classes. The novel stimuli also became class members on the basis of inclusion of any of the critical features. Thus these probe tests revealed the formation of open-ended generalized equivalence classes. In addition, typicality effects were observed such that comparison sets with more critical features were learned with fewer errors, responded to more rapidly, and judged to be better exemplars of the class. Contingency-shaped stimulus classes established through a match-to-sample procedure thus show several important behavioral similarities to natural lexical categories.

Adult↗
PubMedDate not supplied

Do children still pick and choose? The relationship between phonological knowledge and lexical acquisition beyond 50 words.

Previous studies document an influence of phonological knowledge on word learning that differs across development. Specifically, children with expressive lexicons of fewer than 50 words learn words composed of IN sounds more rapidly than those composed of OUT sounds. In contrast, preschool children with larger expressive lexicons show the reverse effect. The goal of the current study was to provide a re-analysis of existing data to determine if this discrepancy across studies may be related to how phonological knowledge has been defined. This study defines knowledge on a continuum from most to more to less. Results showed a continuous inverse relationship between phonological knowledge and word learning by preschool children. Specifically, most phonological knowledge was associated with poorest word learning, more knowledge with intermediate word learning, and less knowledge with best word learning. Theoretical implications are discussed.

Child, Preschool↗
PubMed2002

Implicit and explicit learning in schizophrenics treated with olanzapine and with classic neuroleptics.

OBJECTIVE: Novel and classic neuroleptics differ in their effects on limbic striatal/nucleus accumbens (NA) and prefrontal cortex (PFC) dopamine turnover, suggesting differential effects on implicit and explicit learning as well as on anhedonia. The present study investigates whether such differences can be demonstrated in a naturalistic sample of schizophrenic patients. METHODS: Twenty-five inpatients diagnosed with DSM-IV schizophrenic psychosis and treated for at least 14 days with the novel neuroleptic olanzapine were compared with 25 schizophrenics taking classic neuroleptics and with 25 healthy controls, matched by age and education level. PFC/NA-dependent implicit learning was assessed by a serial reaction time task (SRTT) and compared with cerebellum-mediated classical eye-blink conditioning and explicit visuospatial memory. Anhedonia was measured with the Snaith-Hamilton-Pleasure Scale (SHAPS). RESULTS: Implicit (SRTT) and psychomotor speed, but not explicit (visuospatial) learning were superior in the olanzapine-treated group as compared to the patients on classic neuroleptics. Compared to healthy controls, olanzapine-treated schizophrenics showed similar implicit learning, but reduced explicit (visuospatial) memory performance. Acquisition of eyeblink conditioning was not different between the three groups. There was no difference with regard to anhedonia and SANS scores between the patients. CONCLUSION: Olanzapine seems to interfere less with unattended learning and motor speed than classical neuroleptics. In daily life, this may translate into better adaptation to a rapidly changing environment. The effects seem specific, as in explicit learning and eyeblink conditioning no difference to classic NL was found.

Adult↗
PubMed1997

Unilateral striatal lesions in the cat disrupt well-learned motor plans in a GO/NO-GO reaching task.

We examined the changes in learned and spontaneous motor behavior after a unilateral excitotoxin lesion of the neostriatum. Cats were trained to perform a sensory-cued GO/NO-GO reaching task. Success rate, reaction time, movement speed and kinematic patterns were used to characterize motor system properties. In addition, motor properties before and after the lesion were compared by clinical neurological examinations and video tape observations of free-range behavior. We found that in normal animals motor performance in the task was fluent, highly automatic and skillful with consistent patterns from trial to trial and day to day. The striatal lesion resulted in a marked impairment in the animals' ability to perform the automatic response to the sensory cues in the motor task. In contrast, sensorimotor behavior in contexts apart from the task was altered minimally, with changes that were often difficult to detect. The animals recovered their ability to perform the task gradually, although they never reached prelesion performance levels in up to 24 weeks of evaluation. The animals had difficulty making reaching movements in GO trials and, in NO-GO trials failures to withhold movements were more frequent. Failures were due to a specific inability to execute previously well-learned movements in response to cues and not to an inability to recognize and interpret the cues. The lesion effects were restricted to the automatic motor response to the learned cues, as the animals could make reaching movements to the target without obvious impairment in response to novel stimuli. They also made similar spontaneous movements apart from the motor task that appeared to be unimpaired. The unique motor style and strategies that characterized the behavior of individual animals prior to the lesion were still evident after the lesion, even though they were superimposed on lower success rates and slower movement speeds. Our findings suggest that the basal ganglia facilitate the fluent and rapid execution of sequences of well-learned sensorimotor behavior, but the representations of motor plans are not stored in the basal ganglia.

Animals↗
PubMed1996

The recognition and investigation of X-linked learning disability syndromes.

X-linked learning disability syndromes occur in approximately one per 600 live male births and account for 20-30% of all learning disability. Fragile-X syndrome comprises some 40% of all X-linked learning disability, and there are currently about 95 recognized syndromes comprising the rest. Clinicians should be alert to these other forms of X-linked learning disability: families should be offered genetic counselling, including dysmorphology opinion and cytogenetic testing. Gene mapping on the X chromosome is advancing very rapidly and some causative genes for X-linked learning disability are now known. Clinicians involved in the care of patients with X-linked learning disability are encouraged to investigate all families, report new syndromes and those with cytogenetic abnormalities, and collaborate with clinical geneticists and laboratory scientists working on X chromosome gene mapping.

Chromosome Aberrations↗
PubMed2001

A neuropsychological investigation of prefrontal cortex involvement in acute mania.

OBJECTIVE: Mania has received little attention from a contemporary neuropsychological perspective despite its clear resemblance to the disinhibition syndrome sometimes seen after frontal brain injury, particularly injury to the inferior aspect of the prefrontal cortex. The purpose of this investigation was to describe the neuropsychological profile of severe acute mania by using a range of tasks selected primarily for the detection of localized neural disruption within the prefrontal cortex. METHOD: Fifteen acutely manic inpatients were compared with 30 nonpsychiatric subjects on tasks from the Cambridge Automated Neuropsychological Test Battery (Tower of London, spatial working memory, intradimensional-extradimensional attentional shift, and rapid visual information processing tasks) and on the Iowa Gambling Task, Stroop Color and Word Test, a verbal fluency task, and the California Verbal Learning Test. RESULTS: Discriminant function analysis identified deficits in sustained attention (on the rapid visual information processing task) and verbal learning (on the California Verbal Learning Test) as the best indicators of manic performance, rather than deficits on any of the tests of executive functioning. The model correctly classified 91% of subjects overall and 87% of manic subjects. Manic patients did not resemble patients with ventromedial prefrontal cortex damage in their performance on the Iowa Gambling Task. CONCLUSIONS: Acute mania is characterized by core deficits in verbal memory and sustained attention against a background of milder impairments in functions that are traditional measures of prefrontal cortex integrity (attentional set shifting, planning, working memory). The data do not implicate ventral prefrontal cortex disruption as a locus of pathology in acute mania. Verbal memory and sustained attention deficits may relate differentially to the state and trait characteristics of bipolar disorder.

Acute Disease↗
PubMedDate not supplied

[Capacity for learning and extrapolation of mice selected for having different brain weights].

Ability for learning a simple food-searching reaction, and for extrapolation of a food stimulus movement has been studied in two lines of laboratory mice selected throughout 15 generations for high (H-line) and low (L-line) brain weight. It has been found that the mice from H-line learn the food-searching reaction more rapidly than those from L-line. In first presentation of the extrapolation task, the percentage of right solvings by mice from H- and L-lines does not differ from the 50%, expected for the random alternative choice. In subsequent presentations, the percentage of right solvings steadily increases in both lines, and taken over all presentations significantly exceeds the 50% random level, while the mean time of performance gradually grows shorter. Thus, no difference is observed between H- and L-lines either in solving the extrapolation task or in learning this practice, in contrast to a noticeable superiority of H-line in learning a simple motor reaction.

Animals↗
PubMed2000

Avoidance task training potentiates phasic pontine-wave density in the rat: A mechanism for sleep-dependent plasticity.

Behavioral studies of learning and memory in both humans and animals support a role for sleep in the consolidation and integration of memories. The present study explored possible physiological mechanisms of sleep-dependent behavioral plasticity by examining the relationship between learning and state-dependent phasic signs of rapid eye movement (REM) sleep. Cortical electroencephalogram, electromyogram, eye movement, hippocampal theta-wave, and pontine-wave (P-wave) measures were recorded simultaneously in freely moving rats after a session of conditioned avoidance learning or a control session. After learning trials, rats spent 25.5% more time in REM sleep and 180.6% more time in a transitional state between slow-wave sleep and REM sleep (tS-R) compared with that in control trials. Both REM sleep and tS-R behavioral states are characterized by the presence of P-waves. P-wave density was significantly greater in the first four episodes of REM sleep after the learning session compared with the control session. Furthermore, the P-wave density change between the first and third REM sleep episodes was proportional to the improvement of task performance between the initial training session and the post-sleep retest session. These findings show that the increase in P-wave density during the post-training REM sleep episodes is correlated with the effective consolidation and retention of avoidance task learning.

Animals↗
PubMed1981

Rapid forgetting of a spatial habit in rats with hippocampal lesions.

Rats with lesions of the hippocampus or mammillary bodies were impaired in learning reversal problems in a T-maze. Test trials given after learning each reversal disclosed little forgetting in the mammillary body group but rapid forgetting in the hippocampal group. These findings resemble those recently reported in patients with amnestic syndromes.

Animals↗
PubMed1989

Abnormal optokinetic and perceptual span parameters in cerebellar-vestibular dysfunction and learning disabilities or dyslexia.

To measure the ocular fixation and sequential scanning dysfunction assumed responsible for the visual reading symptoms which characterize dyslexia or learning disabilities, an optokinetically based tracking method was devised. This method quantitatively demonstrated significantly reduced fixation, tracking, and perceptual or visual-span scores as well as "movement illusions" for 70 cerebellar-vestibular dysfunctioning persons with learning disabilities vs 70 controls. Such data tended to validate the hypothesis that cerebellar-vestibular-determined fixation and tracking mechanisms predispose dyslexic or learning disabled individuals to visual reading disorders. Moreover, a newly revised method is presented which may prove useful in rapidly screening and diagnosing cerebellar-vestibular-determined reading and learning disorders from those of other origins. Additional independent studies using significantly larger samples and asymptomatic or "normal" controls are required for further validation and development of the method.

Adolescent↗
PubMed2006

Contextual and temporal modulation of extinction: behavioral and biological mechanisms.

Extinction depends, at least partly, on new learning that is specific to the context in which it is learned. Several behavioral phenomena (renewal, reinstatement, spontaneous recovery, and rapid reacquisition) suggest the importance of context in extinction. The present article reviews research on the behavioral and neurobiological mechanisms of contextual influences on extinction learning and retrieval. Contexts appear to select or retrieve the current relationship of the conditional stimulus (CS) with the unconditional stimulus (US), and they are provided by physical background cues, interoceptive drug cues, emotions, recent trials, and the passage of time. The current article pays particular attention to the effects of recent trials and trial spacing. Control of fear extinction by physical context involves interactions between the dorsal hippocampus and the lateral nucleus of the amygdala. This interaction may be mediated by gamma-aminobutyric acid (GABA)-ergic and adrenergic mechanisms.

Amygdala↗
PubMed2003

Sleep-dependent learning: a nap is as good as a night.

The learning of perceptual skills has been shown in some cases to depend on the plasticity of the visual cortex and to require post-training nocturnal sleep. We now report that sleep-dependent learning of a texture discrimination task can be accomplished in humans by brief (60- 90 min) naps containing both slow-wave sleep (SWS) and rapid eye movement (REM) sleep. This nap-dependent learning closely resembled that previously reported for an 8-h night of sleep in terms of magnitude, sleep-stage dependency and retinotopic specificity, and it was additive to subsequent sleep-dependent improvement, such that performance over 24 h showed as much learning as is normally seen after twice that length of time. Thus, from the perspective of behavioral improvement, a nap is as good as a night of sleep for learning on this perceptual task.

Discrimination Learning↗
PubMed1999

Early learning and the development of filial preferences in the chick.

Newly hatched domestic chicks (Gallus gallus domesticus) rapidly form a social preference for a conspicuous stimulus to which they are exposed. The learning process involved is known as filial imprinting. When chicks are exposed to an audio-visual compound stimulus, both auditory and visual learning are enhanced. The enhancement of visual imprinting is virtually abolished when chicks are exposed separately to the auditory element, either before or after training with the audio-visual compound. Simultaneous exposure to the two elements of the compound is superior to sequential exposure in achieving the enhancement of visual learning. These results are unlike Pavlovian conditioning, but are consistent with an interpretation of imprinting as a form of within-event learning, where links are formed between the representations of the elements of the compound, that can be weakened by separate exposure to an element. Apart from imprinting, chicks may show a developing predisposition to approach stimuli resembling conspecifics. The predisposition emerges in dark-reared chicks given some non-specific experience during a sensitive period, and is expressed as a relatively general preference for stimuli with a head and neck region. In the natural situation, the animal's response may be biased by the predisposition, and through imprinting it then learns the characteristics of individuals.

Animals↗
PubMed1998

Effect of entorhinal cortex lesion on hippocampal cholinergic system in rat in operant learning task as studied by in vivo brain microdialysis.

An in vivo microdialysis method was used to study the cholinergic alteration of the hippocampus in entorhinal cortex-lesioned rats performing a positive reinforcement operant learning task. Rats with bilateral entorhinal cortex lesions were implanted with a dialysis probe into the hippocampal CA3 after ten learning sessions. After 7 days, the bilateral entorhinal cortex-lesioned rats showed impaired acquisition of positive reinforcement operant learning. The basal level of the acetylcholine efflux decreased within 30 min before the beginning of a learning session. The hippocampal acetylcholine efflux showed a significantly diminished increase and rapidly returned to the basal level during the 60 min after the beginning of a learning session. These results suggested that enorhinal cortex lesion may cause damage to the hippocampal cholinergic system with disruption of the entorhinal cortex-hippocampus relay passage.

Acetylcholine↗