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PubMed2005

Imagination nourishes dietetic practice. 2005 Ryley-Jeffs Memorial Lecture.

Albert Einstein once stated that imagination is more important than knowledge. How important is imagination to the dietetic profession? What have been the imaginations of dietitians over the years? Where would we be today without these imaginations? Can imagination be fostered and developed? What future imaginations will shape the dietetic profession? This article explores the phenomenon of imagination and why it is important to dietetic practice.

Canada↗
PubMed2003

Exploring the role of repetition and sensory elaboration in the imagination inflation effect.

Two experiments were conducted to examine whether a misattribution of specific characteristics or a misattribution of global familiarity underlies false memories as assessed through imagination inflation. Using the paradigm developed by Goff and Roediger (1998), we found that the proportion of false memories increased with repeated imagination, replicating the imagination inflation effect. False memories developed through imagination were greatest in conditions that forced participants to include sensory detail in their imaginings. Finally, conscious recollection more often accompanied false memories in perceptually detailed imagination conditions, whereas feelings of familiarity more often accompanied false memories in conditions that lacked sensory cues. These results suggest that imagination that contains more perceptual information leads to more elaborate memory representations containing specific characteristics that can be confused with actually performed actions. Confusion based on these representations, as opposed to confusion based on processing fluency, is more likely to lead to false memories.

Humans↗
PubMed2001

Imagination inflation: a statistical artifact of regression toward the mean.

In the imagination inflation procedure of Garry, Manning, Loftus, and Sherman (1996), subjects rated a list of events in terms of how likely each was to have occurred in their childhood. Two weeks later, some of the events were imagined; control events were not. The subjects then rated the likelihood of occurrence for each event a second time. Garry et al. (1996) reported that the act of imagining the target events led to increased ratings of likelihood. This finding has been interpreted as indicating that false events can be suggestively planted in memory by simply having people imagine them. The present study tests and confirms the hypothesis that the results that have been attributed to imagination inflation are simply a statistical artifact of regression toward the mean. The experiment of Garry et al. (1996) was reproduced (with some procedural changes), using younger and older adults. The results of Garry et al. (1996) were replicated; likelihood ratings for events initially rated low in likelihood did increase from Time 1 to Time 2. However, ratings for events initially rated high in likelihood decreased under the same conditions, and these results were consistent with the imagined target events, the target events not imagined, and the nontarget events.

Adolescent↗
PubMed2004

Warnings reduce the magnitude of the imagination inflation effect.

Imagination inflation occurs when people increase their confidence that an event actually happened after imagining the details of the event. The purpose of this study was to determine whether warning people about the imagination inflation effect would reduce their tendency to inflate their ratings of the imagined events. In one condition, we warned participants about the deleterious effects of imagining distant events. Compared with a control group that did not receive a warning, this group produced a significantly smaller imagination inflation effect. We discuss these results and the imagination inflation effect in the context of 2 theories designed to explain the cognitive processes that produce this effect.

Cognition↗
PubMed1990

Defective gap-junctional communication associated with imaginal disc overgrowth and degeneration caused by mutations of the dco gene in Drosophila.

The lethal(3)discs overgrown (dco) locus of Drosophila melanogaster, located on the third chromosome at cytogenetic position 100A5,6-100B1,2, is necessary for normal development and growth control in the imaginal discs of the larva. Three recessive lethal alleles (dco2, dco3, and dco18) in heteroallelic combinations and one allele (dco3) when homozygous cause the imaginal discs to continue to grow beyond the normal disc-intrinsic limit during an extended larval period. Some degeneration also occurs in the overgrowing discs. The discs overgrow even when transplanted early in their development into wild-type hosts, whereas normal discs stop growth at about the normal final size under such conditions, indicating that the overgrowth is a disc-autonomous effect of the mutations. During overgrowth the imaginal discs retain their single-layered epithelial structure except near regions of degeneration, and they differentiate into disc-appropriate but abnormal adult structures when transplanted into wild-type larval hosts. When the mutant larvae are reared under certain conditions a small percentage develop to the pharate adult stage, and these animals show a characteristic syndrome of abnormalities including swollen leg segments with many extra bristles, small or missing eyes, duplicated antennae and palpi, and separated vesicles of cuticle. A fourth recessive lethal allele (dcole88), when homozygous or in heteroallelic combination with the overgrowth alleles, causes the imaginal discs to degenerate, producing a "discless" phenotype. Gap junction-mediated communication was assayed by observing the intercellular transfer of injected fluorescein complexon (dye coupling). Dye coupling in the imaginal discs of the dco genotypes that cause overgrowth was dramatically reduced at 4 days after egg laying (AEL) compared with wild-type controls. Coupling was more normal although still significantly reduced at 7-8 and 12-14 days AEL. In c43hs1, another disc overgrowth mutant, the imaginal disc cells also showed very reduced dye coupling at 4 days and incomplete coupling at 9 days. In contrast, discs from wild-type larvae, two other imaginal disc overgrowth mutants, and a cell death mutant showed extensive dye coupling at all stages tested. Electron microscopic morphometry revealed a reduction in gap-junction length per unit lateral plasma membrane length in dco3/dco18 and c43hs1 wing discs, although not in dco2/dco3, compared with wild-type wing discs. The results suggest that gap-junctional cell communication may be involved in the cell interactions that limit cell proliferation in vivo.

Alleles↗
PubMed1999

Regulation of imaginal disc cell size, cell number and organ size by Drosophila class I(A) phosphoinositide 3-kinase and its adaptor.

BACKGROUND: Class I(A) phosphoinositide 3-kinases (PI 3-kinases) have been implicated in the regulation of several cellular processes including cell division, cell survival and protein synthesis. The size of Drosophila imaginal discs (epithelial structures that give rise to adult organs) is maintained by factors that can compensate for experimentally induced changes in these PI 3-kinase-regulated processes. Overexpression of the gene encoding the Drosophila class I(A) PI 3-kinase, Dp110, in imaginal discs, however, results in enlarged adult organs. These observations have led us to investigate the role of Dp100 and its adaptor, p60, in the control of imaginal disc cell size, cell number and organ size. RESULTS: Null mutations in Dp110 and p60 were generated and used to demonstrate that they are essential genes that are autonomously required for imaginal disc cells to achieve their normal adult size. In addition, modulating Dp110 activity increases or reduces cell size in the developing imaginal disc, and does so throughout the cell cycle. The inhibition of Dp110 activity reduces the rate of increase in cell number in the imaginal discs, suggesting that Dp110 normally promotes cell division and/or cell survival. Unlike direct manipulation of cell-cycle progression, manipulation of Dp110 activity in one compartment of the disc influences the size of that compartment and the size of the disc as a whole. CONCLUSIONS: We conclude that during imaginal disc development, Dp110 and p60 regulate cell size, cell number and organ size. Our results indicate that Dp110 and p60 signalling can affect growth in multiple ways, which has important implications for the function of signalling through class I(A) PI 3-kinases.

Animals↗
PubMed2002

Ance, a Drosophila angiotensin-converting enzyme homologue, is expressed in imaginal cells during metamorphosis and is regulated by the steroid, 20-hydroxyecdysone.

Ance is a single domain homologue of mammalian angiotensin-converting enzyme (ACE) and is important for normal development and reproduction in Drosophila melanogaster. Mammalian ACE is responsible for the synthesis of angiotensin II and the inactivation of bradykinin and N -acetyl-Ser-Asp-Lys-Pro, but the absence of similar peptide hormones in insects suggests novel functions for Ance. We now provide evidence in support of a role for Ance during Drosophila metamorphosis. The transition of larva to pupa was accompanied by a 3-fold increase in ACE-like activity, which subsequently dropped to larval levels on adult eclosion. This increase was attributed to the induction of Ance expression during the wandering phase of the last larval instar in the imaginal cells (imaginal discs, abdominal histoblasts, gut imaginal cells and imaginal salivary gland). Ance expression was particularly strong in the presumptive adult midgut formed as a result of massive proliferation of the imaginal midgut cells soon after pupariation. No Ance transcripts were detected in the midgut of the fully differentiated adult intestine. Ance protein and mRNA were not detected in imaginal discs from wandering larvae of flies homozygous for the ecd ( 1 ) allele, a temperature-sensitive ecdysone-less mutant, suggesting that Ance expression is ecdysteroid-dependent. Physiological levels of 20-hydroxyecdysone induced the synthesis of ACE-like activity and Ance protein by a wing disc cell line (Cl.8+), confirming that Ance is an ecdysteroid-responsive gene. We propose that the expression of Ance in imaginal cells is co-ordinated by exposure to ecdysteroid (moulting hormone) during the last larval instar moult to increase levels of ACE-like activity during metamorphosis. The enzyme activity may be required for the processing of a developmental peptide hormone or may function in concert with other peptidases to provide amino acids for the synthesis of adult proteins.

Alleles↗
PubMed1974

Genetic control of imaginal disc development in Drosophila.

Many of the functions required for formation of the imaginal discs of Drosophila melanogaster larvae, from which adult structures are derived, are disc-specific and not required for formation of other larval tissues. Mutants blocked in disc-specific functions can produce mature viable larvae, indicating that larval development is not dependent on concomitant disc development. Some of the mutant larvae have no detectable discs (discless mutants), and other have small discs that cannot differentiate into adult structures (small disc mutants). From the results of genetic complementation and mapping experiments with such mutants, it was estimated that the genome of D. melanogaster contains around a thousand complementation groups, or about a fifth of all complementation groups in the genome, that are essential specifically for the development of all the discs. The developmental defects in some of the disc mutants appear to involve autonomous functions of the imaginal cells, and in other mutants functions provided by the larval environment to support disc development. This distinction was made on the basis of two functional tests. The purpose of one of the tests was to detect the presence in young embryos of determined imaginal cells capable of differentiating after transplantation to a wild-type host; the other test measured the capacity of early third-instar larvae to act as hosts for the further development of immature discs transplanted from a wild-type donor. Three discless mutants that were tested in this way appeared to be defective in autonomous functions of the imaginal cells, since the embryos contained no imaginal cells that could be detected in the first test, whereas the larvae, although devoid of discs, showed a normal capacity to support disc development in the second test. One of the small disc mutants tested was defective in a larval rather than an imaginal cell function, since the embryos had a normal complement of functional imaginal cells, whereas the larvae were incapable of supporting disc development. Thus, both types of disc-specific functions are essential for normal disc development.

Animals↗
PubMed1992

Genetic, cytogenetic and developmental analysis of the Drosophila melanogaster tumor suppressor gene lethal(2)tumorous imaginal discs (1(2)tid).

Three of the twenty recessive-lethal tumor suppressor genes of Drosophila cause imaginal disc tumors in the homozygously mutated state. One of these is the lethal(2)tumorous imaginal discs (l(2)tid) gene. Histological preparations show the tumorous imaginal disc epithelium to consist of a mosaic of cells in monolayer and cells in clumped arrangement. In contrast, the wild-type imaginal disc epithelium is comprised exclusively of cells in monolayer arrangement. Mutant imaginal disc tissue pieces implanted into ready-to-pupariate wild-type larvae fail to differentiate. Implantation of l(2)tid imaginal disc tissue pieces in vivo into wild-type adult flies revealed a lethal, tumorous growth comparable to that in situ, thus characterizing the l(2)tid imaginal discs as truly malignant. The phenotypes of double mutants between two l(2)tid alleles and tumor suppressor genes, such as lethal(2)giant larvae and lethal(2)brain tumor, and the epithelial overgrowth mutant lethal(2)fat are described and discussed. Finally, we present the genetic, cytogenetic and molecular localization of the l(2)tid gene to the giant chromosome bands 59F4-6.

Alleles↗
PubMed2002

Expression profiling of Drosophila imaginal discs.

BACKGROUND: In the Drosophila larva, imaginal discs are programmed to produce adult structures at metamorphosis. Although their fate is precisely determined, these organs remain largely undifferentiated in the larva. To identify genes that establish and express the different states of determination in discs and larval tissues, we used DNA microarrays to analyze mRNAs isolated from single imaginal discs. RESULTS: Linear amplification protocols were used to generate hybridization probes for microarray analysis from poly(A)+ RNA from single imaginal discs containing between 10,000 and 60,000 cells. Probe reproducibility and degree of representation were tested using microarrays with approximately 6,000 different cDNAs. Hybridizations with probes that had been prepared separately from the same starting RNA pool had a correlation coefficient of 0.97. Expression-profile comparisons of the left and right wing imaginal discs from the same larva correlated with a coefficient of 0.99, indicating a high degree of reproducibility of independent amplifications. Using this method, we identified genes with preferential expression in the different imaginal discs using pairwise comparisons of discs and larval organs. Whereas disc-to-disc comparisons revealed only moderate differences, profiles differed substantially between imaginal discs and larval tissues, such as larval endodermal midgut and mesodermal fat body. CONCLUSIONS: The combination of linear RNA amplification and DNA microarray hybridization allowed us to determine the expression profiles of individual imaginal discs and larval tissues and to identify genes expressed in tissue-specific patterns. These methods should be widely applicable to comparisons of expression profiles for tissues or parts of tissues that are available only in small amounts.

Animals↗
PubMed1993

Allocation of the thoracic imaginal primordia in the Drosophila embryo.

The primordia of the thoracic imaginal discs of the Drosophila embryo originate as groups of cells spanning the parasegment boundary. We present evidence that the thoracic imaginal primordia are allocated in response to signals from the wingless (wg) and decapentaplegic (dpp) gene products. Rows of cells that express wg intersect rows of cells that express dpp to form a ladder-like pattern in the ectoderm of the germ band extended embryo. The imaginal primordia originate as groups of cells which lie near these intersection points. We have used a molecular probe derived from the Distal-less (Dll) gene to show that this population contains progenitor cells for both the dorsal (i.e. wing) and ventral (i.e. leg) discs. Although we show that Dll function is not required for allocation of imaginal cells, activation of an early Dll enhancer may serve as a molecular marker for allocation. A group of cells, which includes the imaginal progenitors, activate this enhancer in response to intercellular signals from wg and perhaps from dpp. We have used a conditional allele of wg to show that wg function is transiently required for both allocation of the imaginal primordia and for initiation of Dll expression in these cells during the brief interval when wg and dpp form the ladder-like pattern. Allocation of the imaginal primordium and activation of Dll expression appear to be parallel responses to a single set of positional cues.

Animals↗
PubMed1996

Larval and imaginal pathways in early development of Drosophila.

In holometabolous development, higher insects have two different life forms, the larva and the imago. Both larval and imaginal cells are derived from cells of the blastoderm stage. After the final embryonic wave of mitosis, however, only the imaginal cells remain diploid, proliferate massively and do not differentiate until metamorphosis. The separation of these two pathways was described by many authors as a fundamental process that must take place at a very early stage of development, most probably the blastoderm stage. Mainly by using single cell transplantations at the blastoderm or early gastrula stages, respectively, we found common cell lineages between larval and imaginal structures by clones overlapping in the ectoderm (i.e. larval epidermal cells and imaginal discs within a segment, or larval and imaginal salivary gland cells), the mesoderm (i.e. larval somatic muscles and adepithelial cells), and the endoderm (i.e. larval and imaginal midgut cells). From these findings we conclude that it seems to be a principle in Drosophila embryogenesis that the separation of larval and imaginal pathways is postponed to a later developmental stage.

Animals↗
PubMed1996

Imagining projective transformations: aligned orientations in spatial organization.

Four experiments were conducted to investigate whether variations in orientation that profoundly affect the ability to imagine rotations also affect the ability to imagine projective transformations. For a basic rectilinear object and the three simpler Platonic Solids, imagining projective transformations (e.g., the casting of a shadow) was quite successful when the objects were aligned with the direction of projection. For the solids, this alignment occurred when the objects were generalized cylinders about axes aligned with the projection. As the objects were made more oblique to the projection, performance deteriorated markedly. When the objects were moderately aligned with the projection, performance depended on the orientation of the object and the orientation of the projection to the environment. We suggest that the imagination of projection and of rotation is a type of problem solving in which spatial structures are organized in relation to initially given properties of the objects and transformations. When there is alignment among the various structural components, this process of imagination works efficiently. Without such alignment, nonexperts often fail. We suggest that aligned (i.e., parallel and perpendicular) orientations are effective in spatial imagination because they are categorically distinct and singular, and they provide a critical form of redundancy.

Adult↗
PubMed2001

Reality monitoring of performed and imagined interactive events: developmental and contextual effects.

Age differences in reality monitoring of interactive events were examined among 4-year-olds, 8-year-olds, 12-year-olds, and adults. Participants engaged in some interactions and imagined others. Afterward, they were asked to determine whether each action was performed, imagined, or new. This memory test was repeated 1 week later. The 4-year-olds had more difficulty discriminating imagined actions than the two oldest age groups. Imagined actions were more often confused with performed ones than the reverse, though this bias was significant only for the two younger age groups. Reality monitoring decreased over time, especially for imagined items. Activities in which the participant was the agent of action were discriminated better than those in which someone else was the agent of action. Object use during the activity increased the discrimination of imagined actions, especially after the delay. Similarity among actions had no effect. Implications for child eyewitness testimony are discussed.

Adolescent↗
PubMed2006

Facilitation and reciprocal inhibition by imagining thumb abduction.

It is well known that motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) of the motor cortex are facilitated by voluntary muscle contraction. We evaluated the effects of imagination of movements on MEP latencies of agonist and antagonist muscles in the hand using TMS. Twenty-two healthy volunteers were studied. TMS delivered at rest and while imagining tonic abduction of the right thumb. MEPs were recorded in response to magnetic stimulation over the scalp and cervical spine (C7-T1), and central motor conduction times (CMCT) were calculated. MEPs were recorded from right abductor pollicis brevis muscle (APB) and adductor pollicis muscle (AP) simultaneously. Imagination of abduction resulted in a shortened latency of MEPs in the APB muscle, and a prolonged latency in the AP muscle. But the imagination caused no significant change in the latency of MEPs elicited by stimulation over the cervical spine. The changes of the CMCT may account for these latency changes with imagination of movement. These findings indicate that imagination of thumb abduction facilitates motoneurons of agonist muscle and has an inhibitory effect on those of antagonist muscle (reciprocal inhibition).

Adult↗
PubMed2005

Imagined rotations of self versus objects: an fMRI study.

This study used functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms underlying two types of spatial transformations: imagined object rotations and imagined rotations of the self about an object. Participants viewed depictions of single three-dimensional Shepard--Metzler objects situated within a sphere. A T-shaped prompt appeared outside of the sphere at different locations across trials. In the object rotation task, participants imagined rotating the object so that one of its ends was aligned with the prompt. They then judged whether a textured portion of the object would be visible in its new orientation. In the self rotation task, they imagined rotating themselves to the location of the T-prompt, and then judged whether a textured portion of the object would be visible from the new viewpoint. Activation in both tasks was compared to respective control conditions in which identical judgments were made without rotation. A direct comparison of self and object rotation tasks revealed activation spreading from left premotor to left primary motor (M1) cortex (areas 6/4) for imagined object rotations, but not imagined self rotations. In contrast, the self rotation task activated left supplementary motor area (SMA; area 6). In both transformations, activation also occurred in other regions. These findings provide evidence for multiple spatial-transformation mechanisms within the human cognitive system.

Adult↗
PubMed2005

The 'physical prophet' and the powers of the imagination. Part II: a case-study on dowsing and the naturalisation of the moral, 1685-1710.

In the first paper of this pair, I argued the importance of theories of the imagination in debates on divination [Vermeir, K. (2004). The 'physical prophet' and the powers of the imagination. Part I: A case-study on prophecy, vapours and the imagination (1685-1710). Studies in History and Philosophy of Science C, 35, 561-591]. In the present article, I will rely on these results in order to unearth the role of the imagination in a discussion on dowsing. References to the imagination were often implicit because of its negative associations, but I show in detail how the imagination was used to negotiate between the material and the spiritual, and between the natural, the supernatural and the moral. Natural philosophers, theologians and moralists all struggled for authority over divinatory phenomena. The debate evolved around the questions whether moral states could be naturalised and whether subtle material vapours could have moral qualities.

France↗
PubMed2000

The voluntary control of motor imagery. Imagined movements in individuals with feigned motor impairment and conversion disorder.

The ability to volitionally control motor imagery was investigated by comparing the chronometry of real and imagined movements in a patient (AB) with conversion disorder who presented with paralysis of the left arm and hand and in a patient (MM) with an actual injury to the left arm. Control experiments investigated voluntary control of motor imagery in a group of healthy individuals who feigned a motor impairment with one limb and in one group who were instructed to move carefully and slowly. The visually guided pointing task was used to investigate the speed for accuracy trade-offs that occur as target size is varied for both real and imagined performance. In the healthy individuals, the speed for accuracy trade-off for both real and imagined performance on the motor task conformed to Fitts' law provided both the speed and accuracy of movements was emphasised. In MM, real and imagined performance was also within normal limits despite considerable pain and discomfort. In AB and in subjects feigning a motor impairment, motor task performance with the affected limb was slow and did not conform to Fitts' law. However, although imagined performance with the affected limb was generally slower than with the unaffected limb, it did conform to Fitts' law. These results suggest subjects cannot anticipate the effects of an actual limb injury. Furthermore, while they are able to control the general duration of imagined movements they have little voluntary control over their relative timing.

Adult↗