Biomedical subjects

C Spence

Publications and source records attributed to C Spence.

At least 19 recordsLinked to original sources

PubMed2002

A collaborative approach to the implementation of clinical supervision.

AIM: This paper discusses a collaborative approach to implementing clinical supervision, which was initiated between a primary care trust and a school of nursing and midwifery. BACKGROUND: To enable clinical supervision to proceed successfully and to be perceived as beneficial, this necessitates a collaborative partnership between clinicians, managers and educationalists. KEY ISSUES: The different stages of the initiative will be explored and the paper will consider examples of the collaborative processes involved. The evaluation of the project is examined and suggestions for the future continuation of the initiative are discussed. CONCLUSION: There is evidence that this has been a successful initiative and that a collaborative way of working can be beneficial when implementing clinical supervision.

Attitude of Health Personnel↗

PubMed2001

Tactile-visual links in exogenous spatial attention under different postures: convergent evidence from psychophysics and ERPs.

Tactile-visual links in spatial attention were examined by presenting spatially nonpredictive tactile cues to the left or right hand, shortly prior to visual targets in the left or right hemifield. To examine the spatial coordinates of any crossmodal links, different postures were examined. The hands were either uncrossed, or crossed so that the left hand lay in the right visual field and vice versa. Visual judgments were better on the side where the stimulated hand lay, though this effect was somewhat smaller with longer intervals between cue and target, and with crossed hands. Event-related brain potentials (ERPs) showed a similar pattern. Larger amplitude occipital N1 components were obtained for visual events on the same side as the preceding tactile cue, at ipsilateral electrode sites. Negativities in the Nd2 interval at midline and lateral central sites, and in the Nd1 interval at electrode Pz, were also enhanced for the cued side. As in the psychophysical results, ERP cueing effects during the crossed posture were determined by the side of space in which the stimulated hand lay, not by the anatomical side of the initial hemispheric projection for the tactile cue. These results demonstrate that crossmodal links in spatial attention can influence sensory brain responses as early as the N1, and that these links operate in a spatial frame-of-reference that can remap between the modalities across changes in posture.

Adult↗

PubMed2001

Isolation and phenotypic characterization of Pseudomonas aeruginosa pseudorevertants containing suppressors of the catabolite repression control-defective crc-10 allele.

The amiE gene encodes an aliphatic amidase capable of converting fluoroacetamide to the toxic compound fluoroacetate and is one of many genes whose expression is subject to catabolite repression control in Pseudomonas aeruginosa. The protein product of the crc gene, Crc, is required for repression of amiE and most other genes subject to catabolite repression control in this bacterium. When grown in a carbon source such as succinate, wild-type P. aeruginosa is insensitive to fluoroacetamide (due to repression of amiE expression). In contrast, mutants harboring the crc-10 null allele cannot grow in the presence of fluoroacetamide (due to lack of repression of amiE). Selection for succinate-dependent, fluoroacetamide-resistant derivatives of the crc-10 mutant yielded three independent pseudorevertants containing suppressors that restored a degree of catabolite repression control. Synthesis of Crc protein was not reestablished in these pseudorevertants. All three suppressors of crc-10 were extragenic, and all three also suppressed a Delta crc::tetA allele. In each of the three pseudorevertants, catabolite repression control of amidase expression was restored. Catabolite repression control of mannitol dehydrogenase production was also restored in two of the three isolates. None of the suppressors restored repression of glucose-6-phosphate dehydrogenase or pyocyanin production.

Amidohydrolases↗

PubMed2001

Attention to olfaction. A psychophysical investigation.

Olfaction is unique among the senses in that signals from the peripheral sensory receptors bypass the thalamus on their way to the cortex. The fact that olfactory stimuli are not gated by the thalamus has led some researchers to suggest that people may be unable to selectively direct their attention toward the olfactory modality. We examined this issue in an experiment where participants made speeded intensity (strong vs weak)-discrimination responses to an unpredictable sequence of olfactory and visual stimuli. Attention was directed to either olfaction or to vision by means of an informative cue that predicted the likely modality for the upcoming target on the majority of trials. Participants responded more rapidly when the target was presented in the expected rather than the unexpected modality, showing that people can selectively attend to olfaction.

Adult↗

PubMed2001

Reflexive spatial orienting of tactile attention.

We investigated the covert reflexive (exogenous) orienting of tactile spatial attention. Participants made speeded discrimination responses (up vs down) to a series of tactile targets presented randomly to the index finger or thumb of either hand. These targets were preceded at a variable stimulus onset asynchrony (200, 300, or 400 ms) by a spatially nonpredictive tactile cue (presented to both finger and thumb of one or other hand) on either the same or opposite side as the target. Tactile elevation discrimination responses were more rapid and accurate when the cue and target appeared on the same side than when they appeared on opposite sides. Our results provide the first direct empirical evidence that tactile spatial attention can be reflexively directed toward peripheral tactile cues leading to the facilitation of subsequent responses to stimuli presented at that body site.

Adult↗

PubMed2001

Multisensory prior entry.

Despite 2 centuries of research, the question of whether attending to a sensory modality speeds the perception of stimuli in that modality has yet to be resolved. The authors highlight weaknesses inherent in this previous research and report the results of 4 experiments in which a novel methodology was used to investigate the effects on temporal order judgments (TOJs) of attending to a particular sensory modality or spatial location. Participants were presented with pairs of visual and tactile stimuli from the left and/or right at varying stimulus onset asynchronies and were required to make unspeeded TOJs regarding which stimulus appeared first. The results provide the strongest evidence to date for the existence of multisensory prior entry and support previous claims for attentional biases toward the visual modality and toward the right side of space. These findings have important implications for studies in many areas of human and animal cognition.

Adolescent↗

PubMed2001

Failure to remap visuotactile space across the midline in the split-brain.

We examined the effect of posture change on the representation of visuotactile space in a split-brain patient using a cross-modal congruency task. Split-brain patient J.W. made speeded elevation discrimination responses (up versus down) to a series of tactile targets presented to the index finger or thumb of his right hand. We report congruency effects elicited by irrelevant visual distractors placed either close to, or far from, the stimulated hand. These cross-modal congruency effects followed the right hand as it moved within the right hemispace, but failed to do so when the hand crossed the midline into left hemispace. These results support recent claims that interhemispheric connections are required to maintain an accurate representation of visuotactile space.

Attention↗

PubMed2001

Shared attentional resources for processing visual and chemosensory information.

For many years, researchers have argued that we have separate attentional resources for the processing of information impinging on each of our sensory receptor systems. However, a number of recent studies have demonstrated the existence of shared attentional resources for the processing of auditory, visual and tactile stimuli. In the present study, we examined whether there are also common attentional resources for the processing of chemosensory stimuli. Participants made speeded (left vs. right) footpedal discrimination responses to an unpredictable sequence of visual and chemosensory stimuli presented to either nostril. The participants' attention was directed to one or the other modality by means of a symbolic auditory cue (high or low tone) at the start of each trial, which predicted the likely modality for the upcoming target on the majority (80%) of trials. Participants responded more rapidly when the target occurred in the expected modality than when it occurred in the unexpected modality, implying the existence of shared attentional resources for the processing of chemosensory and visual stimuli.

Attention↗

PubMed2001

Spatial modulation of repetition blindness and repetition deafness.

When two identical visual items are presented in rapid succession, people often fail to report the second instance when trying to recall both (e.g., Kanwisher, 1987). We investigated whether this temporal processing deficit is modulated by the spatial separation between the repeated stimuli within both audition and vision. In Experiment 1, lists of one to three digits were rapidly presented from loudspeaker cones arranged in a semicircle around the participant. Recall accuracy was lower when repeated digits were presented from different positions rather than from the same position, as compared to unrepeated control pairs, demonstrating that auditory repetition deafness (RD) is modulated by the spatial displacement between repeated items. A similar spatial modulation of visual repetition blindness (RB) was reported when pairs of masked letters were presented visually from either the same or different positions arranged on a semicircle around fixation (Experiment 2). These results cannot easily be accounted for by the token individuation hypothesis of RB (Kanwisher, 1987; Park & Kanwisher, 1994) and instead support a recognition failure account (Hochhaus & Johnston, 1996; Luo & Caramazza, 1995, 1996).

Auditory Perception↗

PubMed2001

Representation of visuotactile space in the split brain.

Recent neurophysiological research in the monkey has revealed bimodal neuronal cells with both tactile receptive fields on the hand and visual receptive fields that follow the hands as they move, suggesting the existence of a bimodal map of visuotactile space. Using a cross-modal congruency task, we examined the representation of visuotactile space in normal people and in a split-brain patient (J. W.) as the right arm assumed different postures. The results showed that the congruency effects from distracting lights followed the hand around in space in normal people, but failed to do so in the split-brain patient when the hand crossed the midline. This suggests that cross-cortical connections are required to remap visual space to the current hand position when the hand crosses the midline.

Brain↗

PubMed2001

Visual prior entry.

It has long been claimed that attended stimuli are perceived prior to unattended stimuli--doctrine of prior entry. Most, if not all, studies on which such claims have been based, however, are open to a nonattentional interpretation involving response bias, leading some researchers to assert that prior entry may not exist. Given this controversy, we introduce a novel methodology to minimize the effect of response bias by manipulating attention and response demands in orthogonal dimensions. Attention was oriented to the left or right (ie., spatially), but instead of reporting on the basis of location, observers reported the order (first or second) of vertical versus horizontal line segments. Although second-order response biases were demonstrated, effects of attention in accordance with the law of prior entry were clearly obtained following both exogenous and endogenous attentional cuing.

Adult↗

PubMed2001

The cost of expecting events in the wrong sensory modality.

We examined the effects of modality expectancy on human performance. Participants judged azimuth (left vs. right location) for an unpredictable sequence of auditory, visual, and tactile targets. In some blocks, equal numbers of targets were presented in each modality. In others, the majority (75%) of the targets were presented in just one expected modality. Reaction times (RTs) for targets in an unexpected modality were slower than when that modality was expected or when no expectancy applied. RT costs associated with shifting attention from the tactile modality were greater than those for shifts from either audition or vision. Any RT benefits for the most likely modality were due to priming from an event in the same modality on the previous trial, not to the expectancy per se. These results show that stimulus-driven and expectancy-driven effects must be distinguished in studies of attending to different sensory modalities.

Adult↗

PubMed2000

Vision and touch through the looking glass in a case of crossmodal extinction.

When observing ourselves in a mirror, we see our body and adjacent objects (e.g. a comb or razor) projecting the image of distant objects. Are these recoded by the brain as reflecting stimuli in peripersonal space? To address this, we exploited the neuropsychological phenomenon of crossmodal, visual-tactile extinction, as shown by patient BV following right-hemisphere stroke. In such crossmodal extinction, a right visual event impairs the perception of a simultaneous left tactile event. In BV, the right visual stimulus (an LED flash) induced more extinction of touch on the contralesional left hand when presented near the ipsilesional right hand, than when distant from it. This agrees with previous data in patients and monkeys showing that visual-tactile interactions are strongest within peripersonal space. Crucially, we also found that an ipsilesional flash produced more extinction when observed as the distant mirror-reflection of an LED that lay close to the ipsilesional hand, rather than as a distant LED flash projecting an equivalent visual image directly. This suggests that in BV, seeing his own hand via a mirror activates a representation of peripersonal space around that hand, not of the extrapersonal space suggested by the distant visual image in the mirror. We discuss the possible neural basis of interpreting mirror reflections.

Aged↗

PubMed2000

Multisensory perception: beyond modularity and convergence.

Recent research on multisensory perception suggests a number of general principles for crossmodal integration and that the standard model in the field--feedforward convergence of information--must be modified to include a role for feedback projections from multimodal to unimodal brain areas.

Brain↗

PubMed2000

Inhibition of return and oculomotor control in the blind.

Our attentional systems orient reflexively to novel environmental stimuli. Such attentive orienting is typically followed by a prolonged period of inhibition, known as inhibition of return (IOR), thought to be linked to the eye movement system. It is widely believed that IOR may provide a tagging mechanism that prevents perseveration, and thus facilitates attentional search. Using a tactile variant of the peripheral spatial cuing paradigm, we show IOR in congenitally blind adults and in an individual who had no eyes. These results demonstrate for the first time that spatial IOR can occur in the absence of oculomotor control.

Adult↗

PubMed2000

Attracting attention to the illusory location of a sound: reflexive crossmodal orienting and ventriloquism.

Sound localization can be affected by vision; in the ventriloquism effect, sounds that are hard to localize within hearing become mislocalized toward the location of concurrent visual events. Here we tested whether spatial attention is drawn to the illusory location of a ventriloquized sound. The study exploited our previous finding that visual cues do not attract auditory attention. We report an important exception to this rule; auditory attention can be drawn to the location of a visual cue when it is paired with a concurrent unlocalizable sound, to produce ventriloquism. This demonstrates that crossmodal integration can precede reflexive shifts of attention, with such shifts taking place toward the crossmodally determined illusory location of a sound. It also shows that ventriloquism arises automatically, with objective as well as subjective consequences.

Adolescent↗

PubMed2000

Telomere maintenance and length regulation in Trypanosoma brucei.

Transcription of telomere proximal variant surface glycoprotein genes is mono-allelic in bloodstream-form Trypanosoma brucei. The terminal DNA sequence at these telomeres consists of tandem T(2)AG(3) repeats, which increase in length by approximately 8 bp per cell division balanced by occasional loss of large numbers of repeats. Here we have used targeted chromosome fragmentation to investigate the sequence requirements for telomere formation in T. brucei. Telomere formation is most efficient on tandem T(2)AG(3) repeats, but can also occur on specific templates found within 'random' sequence substrates and on G-rich motifs proximal to a double-strand break. Newly formed telomeres are extended faster than other native telomeres, but as the telomere becomes longer the rate of extension declines. Telomere length regulation in T.brucei is discussed in the context of recent results from other cell types.

Animals↗

PubMed2000

Inhibition of return is supramodal: a demonstration between all possible pairings of vision, touch, and audition.

Inhibition of return' (IOR) refers to the delayed detection often found for targets at the same location as a preceding event. We examined whether IOR reflects a truly supramodal phenomenon, in an experiment designed to avoid criticisms of previous crossmodal research. We presented a random sequence of visual, tactile, and auditory targets to either the left or right of central fixation, and tested for IOR between targets in all three modalities when presented successively to the same versus different side. Speeded detection for targets in all three modalities was indeed slower if the preceding target had been presented from the same position, regardless of the modality, of this preceding target. These results demonstrate for the first time that IOR is truly supramodal.

Acoustic Stimulation↗