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PubMed1980

The effect of growth hormone administration on human sleep: a dose-response study.

Human growth hormone and saline were administered for one night each to normal volunteers in a cross-over study. A dose of 2 units im given 15 min before bedtime had no effect on sleep EEG parameters. In contrast, 5 units resulted in a 19% decrease in slow-wave sleep (p < 0.01) and a 13% increase in REM sleep (p < 0.05). Neither doe, when given during daytime, affected tests of affect or serial learning.

Adolescent↗
PubMed1980

Development and use of pharmacological probes of the CNS in man: evidence of cholinergic abnormality in primary affective illness.

The role of cholinergic mechanisms in the regulation of CNS functions was studied in normal humans. The purpose was to develop in vivo pharmacological techniques to assess central neurotransmitter activity in normals and apply them in primary affective illness and other neuropsychiatric conditions. Central cholinergic stimulation by cholinomimetics induced rapid eye movement (REM) sleep, dreaming, cortical arousal, and accelerated the REM cycle. Effects on memory included enhancement of serial learning, short-term consolidation of low-imagery words, and retrieval of clustered information. Analgesia and reduction of the P100 component of visual EEG evoked responses were also noted after physostigmine. Using the induction of REM sleep by arecoline as a "marker" of central cholinergic functioning, it was possible to (i) demonstrate the phenomenon of pharmacological denervation supersensitivity in normal humans after pretreatment with scopolamine, and (ii) demonstrate a significantly faster REM induction by arecoline in two groups of patients with primary affective illness (remitted and depressed) compared to normals. Rapid REM induction was found, not only in remitted patients who were drug-free for 2 weeks, but in patients who had never received somatic therapy. Pretreatment with scopolamine on three consecutive mornings also induced sleep changes at night in normals similar to several sleep abnormalities reported in primary affective illness. This was confirmed by a multivariate discriminate analysis program, which had previously been shown to separate depressed patients, insomniacs, and normals. On the basis of these data, it is proposed that cholinergic abnormalities may be present in primary affective illness during both the ill and the well states.

Acetylcholine↗
PubMed1994

Effects of target probability and memory demands on the vigilance of adults with and without mental retardation.

The vigilance of young adults with mild mental retardation and without mental retardation was compared in two experiments in which observers performed two memory demanding, cognitively based, 60-minute tests. In Experiment 1, target probability was 5% or 30% with a 1.5-second event rate. Detection by observers with mental retardation declined more rapidly than did that of observers without mental retardation in both target probability conditions; further, their response criterion became increasingly more conservative. In Experiment 2, target probability was 10% or 30% with an 8-second event rate. Observers with mental retardation detected fewer targets under both target probability conditions. Subjects' response criterion differed as a function of level of intelligence from the onset of the vigil and did not change with time on task. Intelligence-related differences in vigilance were explained in terms of subjects' information-processing abilities.

Adolescent↗
PubMed1998

Thalamic amnesia reconsidered: excitotoxic lesions of the intralaminar nuclei, but not the mediodorsal nucleus, disrupt place delayed matching-to-sample performance in rats (Rattus norvegicus).

Rats with large thalamic lesions affecting the mediodorsal (MDn) and intralaminar (ILn) nuclei are impaired performing delayed matching to sample tasks (DMTS). To determine the neurological basis of this deficit, we trained rats to perform a place DMTS task and then compared the effects of excitotoxic lesions of the MDn, the ILn, and the lateral internal medullary lamina (L-IML). The MDn lesion had little effect. The ILn group was significantly impaired throughout 8 months of training. The L-IML group exhibited an intermediate level of impairment. Varying the sample response requirement, retention intervals, and trial-to-trial congruence in the side reinforced, had predicted effects, as did variations in response latency. However, none of these factors interacted with the treatment effects. These findings indicate that DMTS performance is disrupted by lesions of the ILn but not the MDn.

Animals↗
PubMed1995

Serial reaction time learning and Parkinson's disease: evidence for a procedural learning deficit.

This paper presents evidence in support of a serial reaction time (SRT) deficit associated with Parkinson's disease, and related to the acquisition or execution of serial-order information. Eleven patients with idiopathic Parkinson's disease, and 10 age-matched but otherwise healthy control subjects, were compared on a variant of the SRT task introduced by Nissen and Bullemer (Cognit. Psychol. 19, 1-32, 1987). The results of this study clearly demonstrate that PD patients produce a quite different pattern of RT performance to that of control subjects. Such a pattern of results may reflect either: (1) a deficit in the patients' ability to learn the temporal order information provided by a repeating sequence of target locations in the SRT task; or (2) a deficit in the patients' ability to express temporal order information provided by the repeating sequence of target locations in the SRT task.

Aged↗
PubMed1981

Codeine-induced memory changes: nature and relationship to opiate system.

Learning and recall processes were studied in three experiments with 33 subjects, 1 and 3 h after oral administration of codeine phosphate 25 mg, 50 mg and 100 mg. Recall was measured 3 and 24 h after drug administration. Nine subjects received naloxone i.m. with the 50 mg dose of codeine. Learning and memory were assessed by using associative, serial and concept learning tasks. Flicker fusion frequency was measured to assess the general vigilance level of the subjects. Learning performance in the serial learning task was improved 3 h after administration of codeine 100 mg. Recall in the serial learning task was also improved after codeine 25 mg, but only when the material was learnt after 1 hour and was recalled 24 h after drug intake. To demonstrate the enhanced recall both learning and recall had to take place under the same drug condition. The same test showed a tendency to enhanced recall after codeine 50 mg of material learnt 1 hour after drug intake and recalled 24 h later. This effect was counteracted by naloxone. The data are consistent with the hypothesis that codeine may exert its action via opiate receptors and that this system participates in memory functions.

Adult↗
PubMed1997

Two forms of sequential implicit learning.

A serial reaction time (SRT) experiment tested the hypothesis that there are two independent forms of implicit learning: learning that is linked to making judgments about stimuli, and learning that is linked to motor processing. Participants performed 2, 6, or 12 blocks of single task SRT, dual task SRT, or observation with one of five sequence; each sequence had the same underlying structure. Participants then performed two implicit tests, SRT (a motor-linked test) and pattern judgment, as well as a generation test and an explicit knowledge test. There was a double dissociation of the effect of sequence surface structure on SRT and pattern judgment. SRT and pattern judgment competence developed independently of each other across length of acquisition task. Performance on both implicit tasks did not depend on explicit knowledge. These results indicate that the SRT and pattern judgment measures tap independent forms of implicit learning, which is consistent with the modular nature of memory and cognition.

Adult↗
PubMed1997

Temporal specificity in serial feature-positive discrimination learning.

Two experiments examined the temporal specificity of learning in operant serial feature-positive discriminations (feature-->target+/target-). Test performance was better when the target cues were presented at their customary times after the features than when they were presented at earlier or later times. When features trained with one feature-target interval were combined with targets trained with another interval, performance was best when the test interval was the same as the interval associated with the feature, suggesting that the temporal information was coded with the feature cue. Finally, the temporal specificity of the responding controlled by occasion setters was unaffected by feature extinction. Implications for the nature of learning in occasion setting are discussed.

Animals↗
PubMedDate not supplied

Effect of prenatal heat stress on brain growth and serial discrimination reversal learning in the guinea pig.

Exposure of pregnant guinea pigs to an environmental temperature of 42 degrees C for 1 hr daily on Days 20-24 of gestation resulted in a significant reduction in the birthweight and brainweight of newborn offspring. These deficits persisted to early maturity and were still evident at 250 days of age following behavioral testing. Although some degree of postnatal neurogenesis and brain growth had occurred, this was not sufficient to compensate for the retarding influence of prenatal hyperthermia. Heat stress was also observed to seriously impair learning performance on the original discrimination task and this tendency persisted over the subsequent 4 reversals for both initial and perseverative errors. Impaired learning performance was related to reduction in brainweight. Animals with lower brainweights made significantly more initial, perseverative and total number of errors over the 5 problems. In addition, 12 of the 14 behaviorally tested stressed progeny had brainweights that were at least 2 standard deviations below the mean of the controls and as a result were classified as micrencephalic. Although heat stressed animals showed a significant reduction in the number of amacrine synapses in the inner plexiform layer of the retina, performance differences were not atrributed to changes in synaptic organisation of the retinal circuitry or to visual or other ophthalmic defects, but brain function. Animals with higher mean maternal poststressing core temperatures gave birth to progeny which had smaller whole and part wet-brainweights. Examination of the effect of poststressing core temperature on brainweight revealed that brain growth, independent of bodyweight, was retarded when this temperature elevated above 41.5 degrees C. This represented a rise of approximately 2.1 degrees C above normal and for each 1 degree C rise above this temperature, brainweight was reduced by 0.4227 g of the control value. Analysis of the atmospheric content of the incubator during stressing sessions ruled out the possibility that changes in level of oxygen and carbon dioxide may have contributed to the retarding influence on fetal development and learning ability in the guinea pig.

Animals↗
PubMed1998

Implicit and explicit learning in an auditory serial reaction time task.

OBJECTIVE: To explore the role of the motor cortex during implicit and explicit learning. MATERIALS AND METHODS: EEG signals were recorded from 30 channels by measuring task-related desynchronization (TRD) when 10 right-handed naive volunteers performed a variation of the serial reaction task. Stimuli, consisting of 4 pure tones of 500, 1000, 1500, and 2000 HZ, lasting 200 ms, were presented binaurally through a pair of tubephones at 60 dB with a 2-s constant interstimulus interval. A series of 10 repetitive tones represented the test sequence; the random sequence was the control. RESULTS: All subjects developed implicit and explicit knowledge reflected by decreased response time, increased accuracy, and the ability to generate the sequence. Six of 10 subjects demonstrated implicit learning without explicit learning during the first 3 blocks. When subjects acquired full explicit learning, 10 Hz TRD at C3 reached a peak amplitude, declining thereafter. CONCLUSIONS: Properties of the sensorimotor cortex change during learning and these changes are independent of stimulus modality.

Adult↗
PubMed1995

Input- and output-monitoring in implicit and explicit memory.

Previous experiments have shown that the procedure of questioning subjects retrospectively about the input and output status of information (input and output monitoring) is a useful method for assessing the awareness states of subjects during implicit and explicit memory tasks. The main purpose of the present study was to investigate whether the previous findings could be extended to other implicit and explicit memory tasks. We were especially interested in whether differences in input- and output-monitoring performance can be observed when both the implicit and explicit memory tasks are conceptual ones. In a final tet phase, the target items from the study phase and new distractor items were presented. In a recognition-like situation, subjects had to decide whether an item had been presented in the study phase (input status), as well as whether they had produced the item in the memory-test phase (output status). In all three experiments judgments about the input status-but only for those items that had been produced in the implicit or in the explicit memory test--were more precise after explicit than after implicit memory testings. This finding was not influenced by the distinction between perceptual and conceptual-memory tasks (Exp. 1), and was obtained under conditions in which the implicit and the explicit memory tasks were both conceptual and differed only in test instructions (Exps. 2 and 3). These results suggest that not only subjects performing a perceptual test of implicit memory, but also subjects in a conceptual implicit test were less aware of using information from a previous study episode than subjects who received memory instructions. It is concluded that requiring judgments about the input status of information is a good method for assessing subjects' test awareness and is preferable to the use of a questionnaire (Exp. 3). In contrast, in all three experiments no differences were found with the output-monitoring measure between implicit and explicit test conditions.

Adult↗
PubMed1990

Further evidence of the intricacy of memory span.

Memory span was measured for lists of verbal items constructed such that the items in the first half of the list were of one category and those of the second half were of another. In Experiment 1, the lists consisted of digits and words (e.g., 2, 8, 7, horse, cow, sheep or horse, cow, sheep, 2, 8, 7); in Experiment 2, they consisted of words from the same semantic domain and words from different semantic domains; in Experiments 3 and 4, they consisted of words that rhymed and words that did not rhyme. A category-order effect occurred in each experiment: Span was larger when the digits, same-domain words, or rhyming words occurred in the first half of the list than when they occurred in the second half. These findings suggest that memory span is more complex than is generally assumed.

Adult↗