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PubMed1978

Failure to replicate negative effects of trace anaesthetics on mental performance.

Twenty-four male subjects individually undertook a selection of cognitive tasks during each of two different 2-h sessions in a climatic chamber. Twelve subjects breathed a mixture of air, nitrous oxide 1600 p.p.m. (v/v) and halothane 16 p.p.m. (v/v) during the first session, and air alone during the second session 1 week later. For the other 12 subjects the order was reversed. The tests comprised learning a list of word-number pairs, solving a set of anagram problems, recognizing words and numbers, recalling word-number pairs and performing a four-choice audiovisual reaction time task. Testing was commenced after 45 min of exposure to the atmospheric conditions. A strong learning effect both within and between sessions was observed on the audiovisual task. None of the tasks, however, reflected any adverse effect of the trace anaesthetics.

Anesthetics↗
PubMed2006

A comparison of adaptive procedures for rapid and reliable threshold assessment and training in naive listeners.

In psychoacoustic studies there is often a need to assess performance indices quickly and reliably. The aim of this study was to establish a quick and reliable procedure for evaluating thresholds in backward masking and frequency discrimination tasks. Based on simulations, four procedures likely to produce the best results were selected, and data collected from 20 naive adult listeners on each. Each procedure used one of two adaptive methods (staircase or maximum-likelihood estimation, each targeting the 79% correct point on the psychometric function) and two response paradigms (3-interval, 2-alternative forced-choice AXB or 3-interval; 3-alternative forced-choice oddball). All procedures yielded statistically equivalent threshold estimates in both backward masking and frequency discrimination, with a trend to lower thresholds for oddball procedures in frequency discrimination. Oddball procedures were both more efficient and more reliable (test-retest) in backward masking, but all four procedures were equally efficient and reliable in frequency discrimination. Fitted psychometric functions yielded similar thresholds to averaging over reversals in staircase procedures. Learning was observed across threshold-assessment blocks and experimental sessions. In four additional groups, each of ten listeners, trained on the different procedures, no differences in performance improvement or rate of learning were observed, suggesting that learning is independent of procedure.

Adult↗
PubMed1970

Unilateral electroconvulsive therapy and cerebral dominance: effect of right- and left-sided electrode placement on verbal memory.

Unilateral electroconvulsive therapy was given to 32 right-handed patients for relief of depression. Sixteen patients received electrode placement on the right side for the first treatment and on the left side for the second treatment. For the other 16 patients the order of sides was reversed. The word Associate Learning subtest of the Wechsler Memory Scale was administered about 20 minutes after each treatment (Wechsler, 1945). Results supported the hypothesis that performance on this test would be better when the electrodes were applied over the right than when they were applied over the right than when they were applied over the left cerebral hemisphere. It is suggested that investigation along these lines could assist in establishing the cerebral dominance of individual patients.

Adult↗
PubMed2006

Sound localization during homotopic and heterotopic bilateral cooling deactivation of primary and nonprimary auditory cortical areas in the cat.

Although the contributions of primary auditory cortex (AI) to sound localization have been extensively studied in a large number of mammals, little is known of the contributions of nonprimary auditory cortex to sound localization. Therefore the purpose of this study was to examine the contributions of both primary and all the recognized regions of acoustically responsive nonprimary auditory cortex to sound localization during both bilateral and unilateral reversible deactivation. The cats learned to make an orienting response (head movement and approach) to a 100-ms broad-band noise stimulus emitted from a central speaker or one of 12 peripheral sites (located in front of the animal, from left 90 degrees to right 90 degrees , at 15 degrees intervals) along the horizontal plane after attending to a central visual stimulus. Twenty-one cats had one or two bilateral pairs of cryoloops chronically implanted over one of ten regions of auditory cortex. We examined AI [which included the dorsal zone (DZ)], the three other tonotopic fields [anterior auditory field (AAF), posterior auditory field (PAF), ventral posterior auditory field (VPAF)], as well as six nontonotopic regions that included second auditory cortex (AII), the anterior ectosylvian sulcus (AES), the insular (IN) region, the temporal (T) region [which included the ventral auditory field (VAF)], the dorsal posterior ectosylvian (dPE) gyrus [which included the intermediate posterior ectosylvian (iPE) gyrus], and the ventral posterior ectosylvian (vPE) gyrus. In accord with earlier studies, unilateral deactivation of AI/DZ caused sound localization deficits in the contralateral field. Bilateral deactivation of AI/DZ resulted in bilateral sound localization deficits throughout the 180 degrees field examined. Of the three other tonotopically organized fields, only deactivation of PAF resulted in sound localization deficits. These deficits were virtually identical to the unilateral and bilateral deactivation results obtained during AI/DZ deactivation. Of the six nontonotopic regions examined, only deactivation of AES resulted in sound localization deficits in the contralateral hemifield during unilateral deactivation. Although bilateral deactivation of AI/DZ, PAF, or AES resulted in profound sound localization deficits throughout the entire field, the cats were generally able to orient toward the hemifield that contained the acoustic stimulus, but not accurately identify the location of the stimulus. Neither unilateral nor bilateral deactivation of areas AAF, VPAF, AII, IN, T, dPE, nor vPE had any effect on the sound localization task. Finally, bilateral heterotopic deactivations of AI/DZ, PAF, or AES yielded deficits that were as profound as bilateral homotopic cooling of any of these sites. The fact that deactivation of any one region (AI/DZ, PAF, or AES) was sufficient to produce a deficit indicated that normal function of all three regions was necessary for normal sound localization. Neither unilateral nor bilateral deactivation of AI/DZ, PAF, or AES affected the accurate localization of a visual target. The results suggest that hemispheric deactivations contribute independently to sound localization deficits.

Acoustic Stimulation↗
PubMed2004

Task-specific sensorimotor adaptation to reversing prisms.

We tested between three levels of visuospatial adaptation (global map, parallel feature modules, and parallel sensorimotor transformations) by training subjects to reach and grasp virtual objects viewed through a left-right reversing prism, with either visual location or orientation feedback. Even though spatial information about the global left-right reversal was present in every training session, subjects trained with location feedback reached to the correct location but with the wrong (reversed) grasp orientation. Subjects trained with orientation feedback showed the opposite pattern. These errors were task-specific and not feature-specific; subjects trained to correctly grasp visually reversed-oriented bars failed to show knowledge of the reversal when asked to point to the end locations of these bars. These results show that adaptation to visuospatial distortion--even global reversals--is implemented through learning rules that operate on parallel sensorimotor transformations (e.g., reach vs. grasp).

Adaptation, Physiological↗
PubMed2004

Lessons to be learned: a case study approach. Bronchiolitis obliterans organising pneumonia: a reversible cause of respiratory failure.

A 70-year-old lady was admitted to hospital through the casualty department with suspected bilateral community acquired pneumonia. Although she received intravenous antibiotics, high concentrations of supplemental inhaled oxygen and continuous positive airway pressure therapy there was failure to respond. Abnormal levels of peripheral blood neutrophil and eosinophil counts as well as computerised tomography chest scan appearances suggested bronchiolitis obliterans organising pneumonia. The diagnosis was confirmed by a lung biopsy obtained by video-assisted thoracoscopy under general anaesthesia. She made a prompt and complete recovery with oral steroid treatment.

Aged↗
PubMed1994

Place recognition and way finding by children and adults.

Children and adults were escorted on their first walk across our university campus and were periodically led off the original route during the return trip. During the return, we stopped prior to intersections on and off the original route to obtain estimates of place recognition accuracy and confidence. The subjects were then asked to point to the path that led back to the start and were corrected if wrong. Accuracy of place recognition was intermediate in a way-finding task requiring reversal of an incidentally learned novel route. However, accuracy increased as subjects were farther from the original route, indicating that the presence of novel landmarks boosted the discrimination of old and new places. Eight-year-old children were less accurate than 12-year-old children and 25-year-old adults, who did not differ in accuracy. There was a similar age difference in the ability to point to the direction to return when subjects correctly recognized that they were off route. The results are used to develop a model of way finding by place recognition.

Adult↗
PubMed1969

Learning sets in an invertebrate.

Eight isopods, Porcellio scaber, were trained with water reinforcement to turn in a T-maze to criterion of correct responses. They were then tested through nine reversals of the turning response. An analysis of variance indicated that mean errors to criterion declined significantly over reversals (F = 4.78, d.f. = 9/63, P < .001).

Analysis of Variance↗
PubMed2004

NMDA lesions in the medial prefrontal cortex impair the ability to inhibit responses during reversal of a simple spatial discrimination.

Although lesion studies suggest that the rat medial prefrontal cortex (mPFc) is involved in the process necessary for reversal of a particular set of contingencies, the nature of lesion-induced deficits is unclear. The involvement of rat mPFc in reversal of a simple spatial discrimination was examined in the present study. Our hypothesis was that lesion-induced deficits may reflect a failure to inhibit a learned instrumental response. Lister Hooded rats were trained on a spatial discrimination task (SD), which required a correct barpress matching the cue location, then they were trained on reversal of SD (SDR), which required a correct barpress opposite to the cue location. Rats with mPFc lesions showed a slower learning rate compared to the controls. However, behavior of the lesioned rats during early and later reversal differed. During the initial SDR, the lesioned rats showed a greater number of barpresses during the intertrial interval and a slightly higher percent correct responses than that of the controls. Our data suggest that damage to mPFc may produce a lack of response inhibition, leading to an increase in nondiscriminated bapresses, thereby yielding a 'facilitation' during early reversal. mPFc lesion did not affect either open field activity or prepulse inhibition (PPI), a frequently used measure of sensorimotor gating. Disruption of reversal learning following damage to mPFc is partly due to a failure to inhibit instrumental responses, rather than to disruption of other processes involved in sensorimotor gating or general activity.

Analysis of Variance↗
PubMed2003

Empirical and theoretical implications of additivity between reinstatement and renewal after interference in causal learning.

An experiment explored the effects of context change (renewal) and presentation of the outcome (reinstatement) upon retroactive interference in causal learning. An interference task was used where a sequential relationship between the name of a food and two different outcomes was established (A+|A*). Renewal and reinstatement effects appeared as partial attenuation of retroactive interference. The combination of both treatments produced complete recovery of first-learned information (A+). This complete reversal on the estimations of participants suggests that renewal and reinstatement effects within this paradigm imply partial recovery of the first-learned information, rather than response at a chance level emitted by confused participants. On the other hand, additivity between reinstatement and renewal suggests that reinstatement may be due to the combined effect of different underlying processes.

Journal Article↗
PubMed1991

Pharmacological consequences of cholinergic plus serotonergic manipulations.

The present study investigated pharmacological consequences of combined cholinergic and serotonergic blockade. Raphe medianus (RM) lesions (5,7-DHT) had no effect on spatial learning, but augmented scopolamine 0.8 mg/kg induced learning deficit. Pilocarpine (4 mg/kg) could reverse scopolamine (0.8 mg/kg), but not scopolamine (0.8 mg/kg) + RM lesion induced spatial learning impairment. However, a higher dose of pilocarpine could restore spatial learning deficit induced by scopolamine (0.8 mg/kg) and RM lesions. These findings support the important role of cholinergic-serotonergic interaction in the regulation of spatial learning and suggests that the combined cholinergic-serotonergic deficit in patient's with Alzheimer's disease may have an impact on therapeutic approaches which seek to normalize AD related cognitive impairments.

5,7-Dihydroxytryptamine↗
PubMed1975

Effects of dorsomedial thalamic lesions on spatial discrimination reversal in the rat.

Eight rats with lesions of the dorsomedial thalamus and 10 rats with sham operations were compared on acquisition and subsequent reversals of a spatial discrimination. The rats with thalamic damage showed greater perseveration to the incorrect choices (p less than 0.002) and made fewer reversals (p less than 0.05) and more errors (p less than 0.02) during the 100 reversal trials following initial acquisition than did the sham-operated animals. The two groups did not differ on the original acquisition.

Animals↗
PubMed2005

Proteomic analysis of specific brain proteins in aged SAMP8 mice treated with alpha-lipoic acid: implications for aging and age-related neurodegenerative disorders.

Free radical-mediated damage to neuronal membrane components has been implicated in the etiology of Alzheimer's disease (AD) and aging. The senescence accelerated prone mouse strain 8 (SAMP8) exhibits age-related deterioration in memory and learning along with increased oxidative markers. Therefore, SAMP8 is a suitable model to study brain aging and, since aging is the major risk factor for AD and SAMP8 exhibits many of the biochemical findings of AD, perhaps as a model for and the early phase of AD. Our previous studies reported higher oxidative stress markers in brains of 12-month-old SAMP8 mice when compared to that of 4-month-old SAMP8 mice. Further, we have previously shown that injecting the mice with alpha-lipoic acid (LA) reversed brain lipid peroxidation, protein oxidation, as well as the learning and memory impairments in SAMP8 mice. Recently, we reported the use of proteomics to identify proteins that are expressed differently and/or modified oxidatively in aged SAMP8 brains. In order to understand how LA reverses the learning and memory deficits of aged SAMP8 mice, in the current study, we used proteomics to compare the expression levels and specific carbonyl levels of proteins in brains from 12-month-old SAMP8 mice treated or not treated with LA. We found that the expressions of the three brain proteins (neurofilament triplet L protein, alpha-enolase, and ubiquitous mitochondrial creatine kinase) were increased significantly and that the specific carbonyl levels of the three brain proteins (lactate dehydrogenase B, dihydropyrimidinase-like protein 2, and alpha-enolase) were significantly decreased in the aged SAMP8 mice treated with LA. These findings suggest that the improved learning and memory observed in LA-injected SAMP8 mice may be related to the restoration of the normal condition of specific proteins in aged SAMP8 mouse brain. Moreover, our current study implicates neurofilament triplet L protein, alpha-enolase, ubiquitous mitochondrial creatine kinase, lactate dehydrogenase B, and dihydropyrimidinase-like protein 2 in process associated with learning and memory of SAMP8 mice.

Aging↗
PubMed2001

Facilitated stimulus-response associative learning and long-term memory in mice lacking the NTAN1 amidase of the N-end rule pathway.

The N-end rule relates the in vivo half-life of a protein to the identity of its N-terminal residue. Inactivation of the NTAN1 gene encoding the asparagine-specific N-terminal amidase in mice results in impaired spatial memory [26]. The studies described here were designed to further characterize the effects upon learning and memory of inactivating the NTAN1 gene. NTAN1-deficient mice were found to be better than wild-type mice on black-white and horizontal-vertical discrimination learning. They were also better at 8-week Morris maze retention testing when a reversal trial was not included in the testing procedures. In all three tasks NTAN1-deficient mice appeared to use a strong win-stay strategy. It is concluded that inactivating the asparagine-specific branch of the N-end rule pathway in mice results in impaired spatial learning with concomitant compensatory restructuring of the nervous system in favor of non-spatial (stimulus-response) learning.

Amidohydrolases↗