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At least 1,261 records · Page 70Linked to original sources
PubMed2003

Adults' understanding of inversion concepts: how does performance on addition and subtraction inversion problems compare to performance on multiplication and division inversion problems?

Problems of the form a + b - b have been used to assess conceptual understanding of the relationship between addition and subtraction. No study has investigated the same relationship between multiplication and division on problems of the form d x e / e. In both types of inversion problems, no calculation is required if the inverse relationship between the operations is understood. Adult participants solved addition/subtraction and multiplication/division inversion (e.g., 9 x 22 / 22) and standard (e.g., 2 + 27 - 28) problems. Participants started to use the inversion strategy earlier and more frequently on addition/subtraction problems. Participants took longer to solve both types of multiplication/division problems. Overall, conceptual understanding of the relationship between multiplication and division was not as strong as that between addition and subtraction. One explanation for this difference in performance is that the operation of division is more weakly represented and understood than the other operations and that this weakness affects performance on problems of the form d x e / e.

Adolescent↗
PubMed2004

The selective serotonin-2A receptor antagonist M100907 reverses behavioral deficits in dopamine transporter knockout mice.

A hyperdopaminergic state in humans has been hypothesized to contribute to the pathology of a number of psychiatric illnesses, including schizophrenia, bipolar disorder, and attention deficit hyperactivity disorder. Mice that display elevated synaptic levels of dopamine due to a genetically engineered deletion of the dopamine transporter (DAT) model behavioral deficits that simulate the above conditions. As novel treatment strategies for these disorders have focused on the serotonin (5-HT) 2A receptor, we determined the capacity of the highly selective 5-HT(2A) receptor antagonist M100907 to reverse behavioral deficits in DAT knockout (KO) mice. Prior to drug treatment, DAT KO mice exhibited increased levels of locomotor activity and highly linearized movement in a novel environment, as well as reduced prepulse inhibition (PPI) of acoustic startle, compared to wild-type littermates. Treatment with M100907 (0.3-1.0 mg/kg, but not 0.1 mg/kg) reversed locomotor deficits in DAT KO mice. Similarly, treatment with 1.0 mg/kg M100907 reversed the PPI deficits in DAT KO mice. These data indicate that selective 5-HT(2A) receptor antagonists, such as M100907, may represent a class of drugs that can be used to treat conditions in which a chronic, elevated dopaminergic tone is present and contributes to abnormal behavior and sensorimotor gating deficits.

Acoustic Stimulation↗
PubMed2003

Repeated withdrawal from ethanol impairs acquisition but not expression of conditioned fear.

Repeated withdrawal from ethanol impairs acquisition of conditioned fear [Stephens, D.N., Brown, G., Duka, T. & Ripley, T.L. (2001) Eur. J. Neurosci., 14, 2023-2031]. This study further examined the effect of repeated withdrawal from ethanol on the expression and acquisition of fear conditioning. Following training, presentation of a cue associated with footshock (CS+) resulted in a suppression of operant responding for food reinforcement. In different groups, shock thresholds were manipulated to give weak or severe behavioural suppression. Rats were subsequently chronically treated with ethanol-containing liquid diet either continuously (single withdrawal) or with three withdrawal periods (repeated withdrawal). Ethanol treatment and withdrawal had no effect on conditioned suppression of responding tested 2 weeks after the final withdrawal, at either shock intensity. Nevertheless, extinction of conditioned fear was impaired in the repeated withdrawal group exposed to the higher shock intensity. In the high intensity group, the stimulus-shock association was then reversed, so that the previously neutral conditioned stimulus (CS-) became the CS+. Acquisition of suppression to the new CS+ was significantly less in the animals previously given repeated experience of withdrawal, confirming our previous finding. Thus, repeated withdrawal from ethanol lead to disruption in the acquisition of fear conditioning but had no effect on retrieval of an association formed prior to the ethanol-withdrawal experiences.

Animals↗
PubMed1979

Depth inversion despite stereopsis: the appearance of random-dot stereograms on surfaces seen in reverse perspective.

Inside-out relief masks of faces can be depth-inverted (i.e. seen in reverse perspective) during close-up binocular viewing. If a random-dot stereogram is projected onto such a mask, stereopsis can be achieved for the stereogram, and its depth planes are correctly seen while the mask itself, including the region covered by the stereogram, is simultaneously perceived as depth-inverted. This demonstration shows that binocular depth inversion cannot be explained by a complete loss of stereoscopic information (e.g. through monocular suppression), or by a process analogous to pseudoscopic viewing whereby retinal disparities are incorporated into perception, but with their signs uniformly reversed.

Cues↗
PubMed1991

The perception of mirror-reflected objects.

In what ways and under what conditions does an object appear to differ from its enantiomorph (its mirror reflection)? This 'mirror question' or its popular counterpart, "Why does a mirror reverse left and right but not up and down?" is frequently encountered, but an acceptable answer is not to be found in the literature. The question is approached as an experimental problem in visual psychophysics. A mirror optically reverses the axis perpendicular to its surface. What are the perceptual consequences of this stimulus transformation? This question is examined in four experiments by using stimuli of varying complexity and familiarity. Apparent reversals are demonstrated along right-left, front-back, top-bottom, and oblique axes, depending on the perceived asymmetries of the stimulus object. Perceived asymmetry is shown to depend both on structural asymmetries and on canonical axes and orientations defined by social convention. It is concluded that an object appears to differ from its enantiomorph by an apparent reversal along the axis of least perceived asymmetry. Implications for perceptual frames of reference and for the perception of symmetry are discussed.

Adult↗
PubMed2002

Functional equivalence of WAIS-III/WMS-III digit and spatial span under forward and backward recall conditions.

The purpose of the current study was to examine the performance characteristics of the Wechsler Spatial Span subtest in a mixed clinical sample. Contrary to expectation, differential patterns of performance were obtained on the Digit and Spatial Span tasks. Forward Digit Span scores were significantly higher than backward recall scores, but this was not the case for Spatial Span. There were no differences between forward and backward raw Spatial Span scores at the mean level. Further, about one third of the sample showed better performance on backward compared to forward Spatial Span. In addition, performance on the Spatial Span backward task correlated unexpectedly with that of the WMS-III Immediate and Delayed Auditory Index scores. Overall, the findings suggest that clinicians should be hesitant when interpreting the Spatial Span task, and the backward condition in particular, as a measure of working memory. Finally, methodological concerns with the Spatial Span task are noted, raising additional concerns regarding the meaning of this task.

Humans↗