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PubMed2001

A threshold explains modulation of neural responses to opposite-contrast stereograms.

Disparity-sensitive neurons respond to contrast-inverted stereograms (aRDS) that do not evoke depth percepts. This is in conflict with the idea that such neurons are the direct correlate of depth perception. However, the output of neurons responding to aRDS may be further processed: neurons at later processing stages show weaker responses to aRDS than early stage neurons. Here, we show that such a response hierarchy emerges in a three-layered neural network. A numerical analysis demonstrates that threshold operations can largely explain the network's behavior as well as the electrophysiological data. An extension of the energy neuron model for disparity-sensitive neurons predicts increased responses to aRDS for an identifiable sub-class of cells and can thus be tested in electrophysiological experiments.

Action Potentials↗

PubMed2003

Neurocognitive function in HIV-infected patients with low weight and weight loss.

OBJECTIVE: To determine neurocognitive function in HIV-infected subjects with low weight and weight loss. DESIGN: Cross-sectional cohort. METHODS: Baseline data from male and female participants in longitudinal treatment studies of AIDS wasting were analyzed. Fifty-seven HIV-infected women (age: 38 +/- 5 years, education level: 12.3 +/- 2.3 years) and 24 HIV-infected men (age: 37 +/- 5 years, education level: 13.5 +/- 2.9 years) with weight <90% IBW or loss of >10% of preillness weight maximum underwent standardized neurocognitive testing to measure intellectual functioning, attention, memory, and fine motor dexterity. The z scores were determined using age- and gender-specific normative data. RESULTS: Among women, IQ (87 +/- 13, z score: -0.8 +/- 0.8 SD) and executive functioning scores (-0.7 +/- 1.2 SD) were below average but within normal limits. In contrast, performance (z scores) on measures of verbal learning (-2.5 +/- 1.5 SD), visuospatial abilities (-2.5 +/- 2.0 SD), and motor coordination (-2.3 +/- 3.3 SD) fell significantly below normal limits. Among men, IQ score was 96 +/- 13 SD (z score: -0.3 +/- 0.8 SD). Performance was below average on measures of verbal learning (-1.0 +/- 1.7 SD) and visual construction (-1.6 +/- 1.7 SD) but within normal limits on executive functioning (-0.1 +/- 1.0 SD). CONCLUSIONS: HIV-infected women at low weight demonstrate significantly reduced verbal learning, memory, and motor function, whereas HIV-infected men at low weight demonstrate more moderate impairment in verbal learning and other measures of neurocognitive function.

Adolescent↗

PubMed1998

The brain and communication are basic for clinical human sciences.

This article focuses on basic concepts modelled on medical science for the human sciences. This reformulates problems experienced by people who consult counsellors, psychologists, psychiatrists, social workers and other human science clinicians as located in the brain. These troubles can be described as difficulties in social life and human communication, on the one hand, and as varied brain physiology, on the other. These problems and their solutions are not traditionally biological but restrictive views of biology need modification as the brain is obviously the central organ for not only the medical specialities of neurology and psychiatry but for all professionals concerned with social interactions. The human genome determines the brain of each person: each such brain constitutes the latest iteration of ancestral genomes that include species precursor to humans and primates, extending back to unicellular life forms. The genome that determines the human brain confers remarkable flexibility or learning potential. Yet many factors influence what is learned and experienced. Understanding this entails comparing and contrasting humans and non-humans. The genomes of chimpanzees and gorillas differ little from that of humans so most basic plans determining behaviour must be shared. Yet contrasted to these animals, the human brain is three times greater in mass and the human cerebral cortex has four times more area. This increased brain correlated with more social interaction; humans are the story-telling animal, producing, consuming and otherwise using small and large tales intensely and incessantly. But do communicational features resemble each other across species? Commnunicational propensity states in humans compare to those of non-humans. So do those of normal people and psychiatric patients. Psychiatry's efforts at systematic description and nosology provided guidelines to the ethology of ancient but still active communicational propensity states called PSALICs (Gardner, 1988). This double acronym refers to their normal function and prehuman origins; they are defined from a three-legged base in that each exists in psychiatric patients, normal people and non-human animals. This article describes the following psalics: alpha, audience, in-group omega, mating, nurturant, nurturance-eliciting, out-group omega and spacing-avoidant. The article describes psalics' varied expression in people. This basic science formulation and an across-species comparisons approach has implications for treating patients and clients.

Animals↗

PubMed2004

Psychometric properties of the Sutter-Eyberg Student Behavior Inventory with rural middle school and high school children.

This study examined the psychometric properties of the Sutter-Eyberg Student Behavior Inventory (SESBI) in a rural sample of children and adolescents. Thirty-eight 5th- through 12th-grade teachers completed the SESBI on 726 children in their classrooms. High Cronbach's alphas supported the reliability of the SESBI scales in this population. Higher SESBI scores were obtained by boys than girls and by African American students than Caucasian students, more so at lower grades. Teacher's race did not affect SESBI scores. In contrast to children with developmental delay, children with learning disabilities obtained higher scores than others on the SESBI Intensity scale but not on the Problem scale. This suggests that teachers of children with learning disabilities recognize the higher frequency of problem behaviors in their students but do not consider these behaviors to be problems for themselves. On both SESBI scales, children with developmental delay were not distinguishable from peers without developmental delays.

Adolescent↗

PubMed2002

Spatial-frequency uncertainty and cuing effects on psychometric functions for contrast detection.

In the present study, the effects of spatial-frequency uncertainty and cuing on psychometric functions for contrast detection of sinusoidal gratings are examined. For this purpose, psychometric functions were collected from 4 subjects under fixed-frequency, randomized-frequency, and cued-frequency conditions. The experiment was conducted with a temporal two-alternative forced-choice task, and five spatial frequencies in the range of 0.5 and 8.0 c/deg and seven contrast levels for each frequency were used. The results showed that the psychometric functions for the randomized-frequency condition were shallower than those for the fixed-frequency condition, supporting the single-band model for the uncertainty effects (Hübner, 1993a, 1993b). For the cued-frequency condition, the slopes of the functions were not clearly different from those for the randomized condition. These results clearly differ from those of Hübner (1996b), which showed, in the spatial two-alternative forced-choice task, steeper psychometric functions for the randomized-frequency condition than those for the fixed- and cued-frequency conditions, supporting the multiple-band model (Hübner, 1993a, 1993b). The difference suggests that the single-band model applies to the uncertainty effects in the temporal forced-choice task, whereas the multiple-band model does so in the spatial forced-choice task.

Adult↗

PubMed1999

Sequential effects in rudimentary auditory and visual tasks.

Three experiments examined sequential effects in choice reaction time tasks. On each trial, a right/left positional judgment was made to a either a pure tone or a luminance increment in a visual array of box elements. In the first two experiments, a preparatory signal was presented prior to each imperative signal to indicate the relevant stimulus modality. At a short stimulus onset asynchrony (SOA) between the preparatory and the imperative signal (i.e., 60 msec), subjects were quicker to repeat the same response than to change their response when presented with successive tones, although no such repetition effect occurred on the visual target trials. Subjects were impaired if the stimulus modality changed across successive trials regardless of the modality of the target. At a longer SOA (i.e., 500 msec), these sequential effects were abolished; subjects were assumed to be able to prepare for the relevant modality because of the presentation of the preparatory signal. When the preparatory signals were omitted, in a final experiment, the modality-switching costs were still evident, but now inhibition of return occurred on both the auditory and the visual target trials-subjects were now impaired in responding when the target reappeared at its immediately previous location. It seems, therefore, that the repetition effect and modality-switching effects do dissociate. The data revealed clear differences between orienting attention to a particular spatial locale and focusing attention to a particular sensory modality.

Attention↗

PubMed1994

Meeting the challenge of the curriculum revolution: problem-based learning in nursing education.

Nursing education today faces a great challenge as it reviews the outcomes of traditional teaching strategies and seeks to explore new alternatives in preparing the nursing student for the complex and diverse profession of nursing. Problem-based learning is one alternative to meeting the needs of a society with health requirements as diverse as its population. Nurses must be capable of exploring options, asking questions, articulating explanations, and developing appropriate nursing care plans based on reflective decisions. They must continue to value learning throughout their careers to maintain their expertise. The role of the educator today is to probe student thinking toward conceptual understanding, to increase depth of subject knowledge, to provide student learning opportunities, and, by encouraging the articulation and contrasting of different points of view, to allow the emergence of common understandings. A problem-based curriculum can provide the framework for the revolution in nursing education to occur.

Curriculum↗

PubMed2002

Dominance of global visual properties at birth.

Six experiments are reported that were aimed at demonstrating the presence in newborns of a perceptual dominance of global over local visual information in hierarchical patterns, similar to that observed in adults (D. Navon, 1977, 1981). The first four experiments showed that, even though both levels of visual information were detectable by the newborn (Experiments 1A and 1B), global cues enjoyed some advantage over local cues (Experiments 2 and 3). Experiments 4A and 4B demonstrated that the global bias was strictly dependent on the low spatial frequency content of the stimuli and vanished after selective removal of low spatial frequencies. The results are interpreted as suggesting parallels between newborns' visual processing and processing later in development.

Attention↗

PubMed1966

Behavioral contrast and the peak shift: effects of extended discrimination training.

Behavioral contrast and the peak shift, two widely observed phenomena in experiments on successive discrimination learning, were shown to disappear during extended discrimination training. This finding and an analysis of the conditions under which behavioral contrast and the peak shift occur suggested that both phenomena were by-products of emotional responses that resulted from response suppression and that their disappearance after extended discrimination training could be attributed to the dissipation of such emotional responses.

Animals↗

PubMed2003

Dissociable contributions of the orbitofrontal and infralimbic cortex to pavlovian autoshaping and discrimination reversal learning: further evidence for the functional heterogeneity of the rodent frontal cortex.

To examine possible heterogeneity of function within the ventral regions of the rodent frontal cortex, the present study compared the effects of excitotoxic lesions of the orbitofrontal cortex (OFC) and the infralimbic cortex (ILC) on pavlovian autoshaping and discrimination reversal learning. During the pavlovian autoshaping task, in which rats learn to approach a stimulus predictive of reward [conditional stimulus (CS+)], only the OFC group failed to acquire discriminated approach but was unimpaired when preoperatively trained. In the visual discrimination learning and reversal task, rats were initially required to discriminate a stimulus positively associated with reward. There was no effect of either OFC or ILC lesions on discrimination learning. When the stimulus-reward contingencies were reversed, both groups of animals committed more errors, but only the OFC-lesioned animals were unable to suppress the previously rewarded stimulus-reward association, committing more "stimulus perseverative" errors. In contrast, the ILC group showed a pattern of errors that was more attributable to "learning" than perseveration. These findings suggest two types of dissociation between the effects of OFC and ILC lesions: (1) OFC lesions impaired the learning processes implicated in pavlovian autoshaping but not instrumental simultaneous discrimination learning, whereas ILC lesions were unimpaired at autoshaping and their reversal learning deficit did not reflect perseveration, and (2) OFC lesions induced perseverative responding in reversal learning but did not disinhibit responses to pavlovian CS-. In contrast, the ILC lesion had no effect on response inhibitory control in either of these settings. The findings are discussed in the context of dissociable executive functions in ventral sectors of the rat prefrontal cortex.

Animals↗

PubMed1998

Piracetam inhibits Pavlovian extinction and reversal learning in a spatial task for rats.

Young male rats, trained in a spatial three-choice test, showed improved task acquisition after chronic treatment with piracetam (250 mg kg(-1)). After reaching a learning criterion, one group of animals was observed during Pavlovian extinction of the task skill and another group was assigned to reversal learning. The rate of extinction was slowed down in piracetam treated specimens compared to control animals. During reversal training, a new choice had to be learned while the previously acquired choice was no longer reinforced. Acquisition of the new skill was significantly impeded by piracetam in contrast to acquisition of the first skill, which was facilitated. Also during reversal learning, the piracetam treated group persevered longer than the control group in repeating the first acquired choice at the expense of learning the new choice. It is therefore suggested, that the impediment of reversal learning was caused by inhibition of extinction. In an open-field test, the time spent exploring in motion was increased by piracetam while the velocity of locomotion was unaffected by the drug. In a novelty test, piracetam increased the rate of loss of interactions with the novel object.

Animals↗

PubMed1995

Verbal short-term memory and vocabulary learning in polyglots.

Polyglot and non-polyglot Italian subjects were given tests assessing verbal (phonological) and visuo-spatial short-term and long-term memory, general intelligence, and vocabulary knowledge in their native language. Polyglots had a superior level of performance in verbal short-term memory tasks (auditory digit span and nonword repetition) and in a paired-associate learning test, which assessed the subjects' ability to acquire new (Russian) words. By contrast, the two groups had comparable performance levels in tasks assessing general intelligence, visuo-spatial short-term memory and learning, and paired-associate learning of Italian words. These findings, which are in line with neuropsychological and developmental evidence, as well as with data from normal subjects, suggest a close relationship between the capacity of phonological memory and the acquisition of foreign languages.

Adult↗

PubMed2005

Complex-environment rearing prevents prenatal hypoxia-induced deficits in hippocampal cellular mechanisms necessary for memory consolidation in the adult Wistar rat.

Hypoxic episodes in utero can result in enduring and debilitating neurological sequelae that include nonprogressive motor disorders and/or significant learning deficits. The extent of long-term disruption of synaptic function following prenatal hypoxia and its subsequent effect on learning ability, however, remain to be established. Polysialylation of the neural cell adhesion molecule, a cellular event integral to the consolidation of diverse learning paradigms, was used to correlate cellular end points with learning deficits as a consequence of prenatal hypoxia. Pregnant Wistar dams exposed to hypobaric hypoxia during gestational days 10-20 had significantly reduced litter sizes, but the lack of effect on subsequent pup weight gain suggested no gross developmental deficit. By contrast, adult animals with prior in utero hypoxia exhibited significant learning difficulties in both acquisition of a water maze spatial learning task and recall of a passive avoidance paradigm. Learning deficits correlated with a significant reduction in the frequency of polysialylated neurons in the dentate infragranular zone and a blunting of their transient activation 12 hr following task acquisition. Rearing animals with prior prenatal hypoxia in a complex environment, however, eliminated the task acquisition and recall deficits and restored dentate polysialylated cell frequency and their transient posttraining increase.

Animals↗

PubMed2007

The disruptive effects of the CB1 receptor antagonist rimonabant on extinction learning in mice are task-specific.

RATIONALE: Disruption of CB(1) receptor signaling through the use of CB(1) (-/-) mice or the CB(1) receptor antagonist rimonabant (SR141716) has been demonstrated to impair extinction of learned responses in conditioned fear and Morris water maze tasks. In contrast, CB(1) (-/-) mice exhibited normal extinction rates in an appetitively motivated operant conditioning task. OBJECTIVES: The purpose of this study was to test whether rimonabant would differentially disrupt extinction learning between fear-motivated and food-motivated tasks. MATERIALS AND METHODS: Separate groups of C57BL/6J mice were trained in two aversively motivated tasks, conditioned freezing and passive avoidance, and an appetitively motivated operant conditioning task at a fixed ratio (FR-5) schedule of food reinforcement. After acquisition, the respective reinforcers in each task were withheld, and an intraperitoneal injection of vehicle or rimonabant was given 30 min before each extinction session. RESULTS: Rimonabant (3 mg/kg) treatment significantly disrupted extinction in both the conditioned freezing and passive avoidance tasks but failed to affect extinction rates in the operant conditioning task, whether using daily or weekly extinction sessions. Interestingly, rimonabant (3 mg/kg) prevented the significant increases in lever pressing (i.e., extinction burst) that occurred during the first extinction session of the operant conditioning task. CONCLUSIONS: These results support the hypothesis that the CB(1) receptor plays a vital role in the extinction of aversive memories but is not essential for extinction of learned responses in appetitively motivated tasks.

Animals↗

PubMed2002

The anxiety of learning. Interview by Diane L. Coutu.

Despite all the time, money, and energy that executives pour into corporate change programs, the stark reality is that few companies ever succeed in genuinely reinventing themselves. That's because the people at those companies rarely master the art of transformational learning--that is, eagerly challenging deeply held assumptions about a company's processes and, in response, altering their thoughts and actions. Instead, most people just end up doing the same old things in superficially tweaked ways. Why is transformational learning so hard to achieve? HBR senior editor Diane Coutu explores this question with psychologist and MIT professor Edgar Schein, a world-renowned expert on organizational development. In sharp contrast to the optimistic rhetoric that permeates the debate on corporate learning and change, Schein is cautious about what companies can and cannot accomplish. Corporate culture can change, he says, but this kind of learning takes time, and it isn't fun. Learning is a coercive process, Schein argues, that requires blood, sweat, tears, and a certain level of anxiety to achieve the desired effect. In this article, he describes two basic types of anxiety--learning anxiety and survival anxiety--that drive radical relearning in organizations. Schein's theories spring from his early research on how American prisoners of war in Korea had been brainwashed by their captors. He cites the parallels between the "coercive persuasion" tactics the Chinese communists used to control their prisoners (isolating powerful ones and overseeing all communications) and the corporate boot camps that American companies use to indoctrinate their managers. Indeed, heavy socialization is back in style in U.S. corporations today, Schein says, even if no one is calling it that.

Commerce↗

PubMed2000

Effects of prenatal dexamethasone on spatial learning and response to stress is influenced by maternal factors.

The present study investigated the effect of prenatal dexamethasone (Dex) exposure on early perinatal events, hippocampal function, and response to stress. Pregnant rats received Dex in the evening water (2.5 microg/ml) or tap water (Veh) from gestational day 15 until delivery. On the day of parturition, pups were randomized, cross-fostered, and reduced to eight or nine per dam. Four groups resulted: Veh-Veh (offspring exposed to Veh in utero, rearing mother treated with Veh during gestation), Veh-Dex, Dex-Veh, and Dex-Dex. Spatial visual memory was evaluated with the Morris water maze. The corticosterone response to restraint stress was examined, and the expression of hippocampal glucocorticoid and mineralocorticoid receptors mRNA was determined by in situ hybridization. Exposure to Dex caused restlessness in mothers, low birth weights, and poor weight gain in the offspring. The Dex-Dex males had impaired spatial learning, inability to rapidly terminate the adrenocortical response to stress, and decreased hippocampal glucocorticoid receptor (GR) mRNA expression. In contrast, Dex-exposed animals reared by Veh-treated mothers had adequate spatial learning, enhanced glucocorticoid feedback, and increased hippocampal GR mRNA. We conclude that the environment provided by a healthy mother during the postnatal period can prevent the detrimental effects of prenatal Dex administration on cognition, GR mRNA expression of the hippocampus, and the quality of the stress response.

Adrenal Cortex↗

PubMed1997

Infants listen for more phonetic detail in speech perception than in word-learning tasks.

Infants aged 4-6 months discriminate the fine phonetic differences that distinguish syllables in both their native and unfamiliar languages, but by 10-12 months their perceptual sensitivities are reorganized so that they discriminate only the phonetic variations that are used to distinguish meaning in their native language. It would seem, then, that infants apply their well honed phonetic sensitivities as they advance and begin to associate words with objects, but the question of how speech perception sensitivities are used in early word learning has not yet been answered. Here we use a recently developed technique to show that when they are required to pair words with objects, infants of 14 months fail to use the fine phonetic detail they detect in syllable discrimination tasks. In contrast, infants of 8 months--who are not yet readily learning words--successfully discriminate phonetic detail in the same task in which infants aged 14 months fail. Taken together, these results suggest a second reorganization in infants's use of phonetic detail as they move from listening to syllables to learning words.

Aging↗

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↗