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Biomedical subjects

Peter D Drummond

Publications and source records attributed to Peter D Drummond.

At least 19 recordsLinked to original sources
PubMed2006

Blushing during social interactions in people with a fear of blushing.

Changes in facial blood flow were investigated during an introductory conversation, delivering a speech, and listening to the speech afterwards in 16 people with a fear of blushing and 16 controls. It was hypothesized that fear of blushing would be associated with high ratings of self-reported blushing intensity and embarrassment during the tasks, and with persistence of the blushing reaction between tasks. Embarrassment and self-reported blushing intensity were greater in the fear-of-blushing group than in controls throughout the experiment. Increases in facial blood flow were similar in the two groups during each of the tasks. However, blushing dissipated more slowly after each task in the fear-of-blushing group than in controls, resulting in an incremental increase in facial blood flow over the course of the experiment. The slow recovery after an episode of blushing might result in physiological or social cues that help to maintain a fear of blushing.

Adult↗
PubMed2006

Many-body quantum dynamics of polarization squeezing in optical fibers.

We report new experiments that test quantum dynamical predictions of polarization squeezing for ultrashort photonic pulses in a birefringent fiber, including all relevant dissipative effects. This exponentially complex many-body problem is solved by means of a stochastic phase-space method. The squeezing is calculated and compared to experimental data, resulting in excellent quantitative agreement. From the simulations, we identify the physical limits to quantum noise reduction in optical fibers. The research represents a significant experimental test of first-principles time-domain quantum dynamics in a one-dimensional interacting Bose gas coupled to dissipative reservoirs.

Journal Article↗
PubMed2006

Immersion of the hand in ice water releases adrenergic vasoconstrictor tone in the ipsilateral temple.

Immersion of the hand in painfully cold water induces cutaneous vasodilatation in the temples, more so ipsilaterally than contralaterally. To investigate the mechanism of this response, guanethidine or saline was administered by transcutaneous iontophoresis to a recording site in the temple of ten participants before they immersed one of their hands in ice water. Guanethidine displaces noradrenaline from sympathetic nerve terminals and inhibits sympathetic noradrenergic neurotransmission. Therefore, it was hypothesized that guanethidine pre-treatment would block vasodilatation mediated by release of sympathetic vasoconstrictor tone in cutaneous vessels in the temple. During hand immersion, increases in the amplitude of the pulse waveform detected by laser Doppler flowmetry were greater in the ipsilateral than contralateral temple (86% vs. 34% above baseline, p<0.05), and pre-treatment with guanethidine prevented this asymmetric response (ipsilateral response 21% above baseline and contralateral response 32%, difference not significant). Guanethidine also inhibited ipsilateral increases in cutaneous blood flow during hand immersion in responsive participants. These findings suggest that limb pain inhibited ipsilateral adrenergic vasoconstrictor outflow in the temple. Thus, the findings challenge the concept of the sympathetic nervous system as a "mass action" system that discharges in unison to meet environmental demands. Instead, they suggest that the sympathetic nervous system is highly differentiated, with separate control of discrete reflex pathways on each side of the body.

Adolescent↗
PubMed2006

Sensory changes in the forehead of patients with complex regional pain syndrome.

The aim of this study was to investigate involvement of central mechanisms in complex regional pain syndrome (CRPS). In particular, we wished to determine whether hyperalgesia extends ipsilaterally from the affected limb to the forehead. The heat-pain threshold, pressure-pain threshold, and ratings of cold and sharpness were investigated on each side of the forehead and in the affected and unaffected limbs of 38 patients with features of CRPS. In addition, touch thresholds were investigated in the limbs. The pressure-pain threshold was lower on the ipsilateral forehead than contralaterally, consistent with the presence of static mechanical hyperalgesia. Although the heat-pain threshold and ratings of sharpness and cold did not differ between the two sides of the forehead in the group as a whole, the sharpness of pinprick sensations in the affected limb was mirrored by similar sensations in the ipsilateral forehead. Conversely, diminished sensitivity to light touch in the affected limb was associated with diminished sensitivity to sharpness, cold and heat-pain in the ipsilateral forehead. These findings suggest that central nociceptive processing is disrupted in CRPS, possibly due to disturbances in the thalamus or higher cortical centres.

Adolescent↗
PubMed2006

Dissociation between pain and the nociceptive blink reflex during psychological arousal.

OBJECTIVE: To investigate the effect of psychological arousal on pain ratings and the R2 component of the electrically evoked blink reflex to a 'pure' noiciceptive stimulus. METHODS: Pain ratings and R2 to a noiciceptive stimulus (pulse width 0.3ms, 2mA, delivered from a concentric electrode attached to the supraorbital region of the forehead) were investigated in 16 healthy participants before and during a serial subtraction task, and in 16 control participants who sat quietly during nociceptive stimulation. RESULTS: Pain ratings decreased whereas R2 amplitude increased during the serial subtraction task. CONCLUSIONS: Supra-spinal rather than spinal mechanisms inhibited pain perception during psychological arousal. Moreover, psychological arousal facilitated the R2 component of the blink reflex to a nociception-specific stimulus. SIGNIFICANCE: Supra-spinal influences need to be considered during clinical evaluation of the trigeminal nociceptive blink reflex.

Adult↗
PubMed2006

Cognitive behavioural therapy increases re-employment of job seeking worker's compensation clients.

INTRODUCTION: The aim of this study was to determine whether cognitive behavioural therapy (CBT) would enhance employment outcomes in worker's compensation clients who were seeking employment. METHODS: Participants were randomly assigned to a standard job search assistance group that met for 4 hours/week for four weeks, or to a group that received standard job search assistance for 4 hours/week for the first two weeks and CBT for 4 hours/week for the next two weeks. Depression, Anxiety and Stress scores were measured prior to and on completion of the intervention, and employment outcomes were assessed at four- and ten-week follow-up. RESULTS: Affective states decreased and employment was found more rapidly after CBT than after standard job search assistance. CONCLUSION: These findings indicate that CBT has a useful role in the rehabilitation of people on worker's compensation who are seeking employment.

Adult↗
PubMed2005

Interaction between testosterone and apolipoprotein E epsilon4 status on cognition in healthy older men.

CONTEXT: Reduced testosterone levels have been implicated as a potential causative factor in cognitive decline with older age. Men who possess the apolipoprotein E (APOE) epsilon4 allele have an increased risk of developing Alzheimer's disease; however, no studies have examined whether the influence of testosterone on cognition in healthy older men may be modulated by this genetic predisposition. OBJECTIVE: The objective of the study was to investigate the association between serum testosterone concentrations and cognitive performance in healthy older men, taking into account APOE epsilon4 status. DESIGN: This was a cross-sectional study conducted from 2003 to 2004. SETTING: The study population consisted of community-dwelling males residing in Perth, Western Australia. PARTICIPANTS: Healthy men over 55 yr, free of cognitive impairment and dementia (n = 45), were included in the study. MAIN OUTCOME MEASURES: Participants had fasting early morning blood samples for testosterone and SHBG and were assessed for mood as well as indices of general cognition, verbal and visual memory, executive functioning, working memory, and attention. RESULTS: There was a significant interaction between calculated free testosterone (FT) and APOE epsilon4 on general cognition (P = 0.01) and executive functioning, working memory, and attention (P < 0.01). Higher levels of FT were associated with better general cognition in non-epsilon4 carriers (P = 0.01). By contrast, in epsilon4 carriers higher FT levels were associated with lower scores on tests of executive functioning, working memory, and attention (P = 0.02). In men at increased risk for Alzheimer's disease, higher testosterone levels were not associated with better cognitive function. CONCLUSIONS: Cross-sectional and prospective studies of testosterone and cognition in older men should take into account APOE epsilon4 status.

Aged↗
PubMed2005

Effect of tryptophan depletion on symptoms of motion sickness in migraineurs.

Seven hours after 39 migraineurs and 37 controls consumed an amino acid drink that contained or omitted l-tryptophan (thereby reducing brain serotonin synthesis), motion sickness was provoked by the visual illusion of movement. Tryptophan depletion boosted dizziness, nausea, and the illusion of movement in controls to levels that approached those of migraineurs. Thus, reduced brain serotonin activity may promote vestibuloocular disturbances during motion sickness and attacks of migraine.

Adolescent↗
PubMed2005

Universality of quantum critical dynamics in a planar optical parametric oscillator.

We analyze the critical quantum fluctuations in a coherently driven planar optical parametric oscillator. We show that the presence of transverse modes combined with quantum fluctuations changes the behavior of the "quantum image" critical point. This zero-temperature nonequilibrium quantum system has the same universality class as a finite-temperature magnetic Lifshitz transition.

Journal Article↗
PubMed2005

Signature of Mott-insulator transition with ultracold fermions in a one-dimensional optical lattice.

Using the exact Bethe ansatz solution of the Hubbard model and Luttinger liquid theory, we investigate the density profiles and collective modes of one-dimensional ultracold fermions confined in an optical lattice with a harmonic trapping potential. We determine a generic phase diagram in terms of a characteristic filling factor and a dimensionless coupling constant. The collective oscillations of the atomic mass density, a technique that is commonly used in experiments, provide a signature of the quantum phase transition from the metallic phase to the Mott-insulator phase. A detailed experimental implementation is proposed.

Journal Article↗
PubMed2005

Time-reversal test for stochastic quantum dynamics.

The calculation of quantum dynamics is currently a central issue in theoretical physics, with diverse applications ranging from ultracold atomic Bose-Einstein condensates to condensed matter, biology, and even astrophysics. Here we demonstrate a conceptually simple method of determining the regime of validity of stochastic simulations of unitary quantum dynamics by employing a time-reversal test. We apply this test to a simulation of the evolution of a quantum anharmonic oscillator with up to 6.022x10(23) (Avogadro's number) of particles. This system is realizable as a Bose-Einstein condensate in an optical lattice, for which the time-reversal procedure could be implemented experimentally.

Journal Article↗
PubMed2005

The effect of glucose and mental stress on cutaneous microvascular endothelial function.

Glucose and mental stress, independently, have been found to impair arterial endothelial function (an indicator of vascular health). The present study sought to determine whether the combination of glucose and stress would have a greater effect on microvascular endothelial function than each on its own. To assess endothelial function, surges in skin blood flow (reactive hyperemia), following the release of cuff pressure to the upper arm at 200 mmHg for 5 min, were measured with laser Doppler flowmetry in 40 young, healthy females. Endothelial function did not change significantly following a 5-min mathematics stressor or the consumption of 75 g of glucose. However, the combination of glucose and stress impaired endothelium-dependent dilatation 30 min after glucose consumption. These findings suggest that combinations of vascular risk factors may be more threatening to cardiovascular health than singularly occurring factors.

Adult↗
PubMed2005

Triggers of motion sickness in migraine sufferers.

OBJECTIVE: To determine whether susceptibility to motion sickness provoked by unexpected movement is associated with susceptibility to visually induced motion sickness in migraine sufferers. BACKGROUND: Migraine sufferers are unusually susceptible to motion sickness, but the mechanism of this susceptibility is not well understood. Possibilities include vestibular dysfunction secondary to vasomotor disturbances during migraine attacks, hyperexcitability of brainstem circuits that produce symptoms of motion sickness and migraine, and heightened susceptibility to visual illusions of movement. METHOD: A motion sickness susceptibility questionnaire that listed common triggers of motion sickness was filled out by 42 migraine sufferers and 39 headache-free controls of similar age and sex distribution to migraine sufferers. RESULTS: A greater proportion of migraine sufferers than controls reported that traveling in cars and buses, reading in the car, using playground equipment, watching wide-screen movies and movement simulators, induced motion sickness. However, visually induced motion sickness appeared to be independent of motion sickness to most movement-related stimuli in migraine sufferers. CONCLUSIONS: The lack of association between susceptibility to movement-induced and visually induced motion sickness implies that more than one mechanism increases susceptibility to motion sickness in migraine sufferers.

Adult↗
PubMed2004

Facial pain increases nausea and headache during motion sickness in migraine sufferers.

The aim of this study was to determine whether trigeminal nerve discharge associated with painful stimulation of the temple would intensify symptoms of motion sickness in migraine sufferers. If so, this would support the notion that symptoms such as nausea and headache interact with each other during attacks of migraine. Symptoms of motion sickness were rated at 2 min intervals during 15 min of optokinetic stimulation in 27 migraine sufferers and 23 age- and sex-matched controls. To document changes in frontotemporal blood flow, pulse amplitude was monitored with photoelectric pulse transducers. To induce facial pain, ice was applied to the temple for 30 s, three times at 4 min intervals during optokinetic stimulation. On another occasion, pain was induced during optokinetic stimulation by immersing the non-dominant hand in 2 degrees C ice water for 30 s, three times at 4 min intervals. On a third occasion, measures were obtained during optokinetic stimulation alone. Migraine sufferers rated themselves as being generally more susceptible to motion sickness than controls. In addition, symptoms of motion sickness provoked by optokinetic stimulation were greater in migraine sufferers than in controls. Painful stimulation of the temple intensified nausea and headache during optokinetic stimulation, whereas painful stimulation of the hand did not. Since nausea also intensifies facial pain during motion sickness, nausea and headache may reinforce each other in a vicious circle. In the absence of painful stimulation, increases in pulse amplitude during optokinetic stimulation were greater in migraine sufferers than controls, possibly because the discomfort associated with motion sickness triggered extracranial vasodilatation in migraine sufferers as part of a fight-or-flight (defense) response. Extracranial vasodilatation did not differ between migraine sufferers and controls when ice was applied to the temple or hand during optokinetic stimulation, implying that the additional discomfort associated with painful stimulation of the head and hand evoked a defense response in controls. These findings suggest that a mechanism which boosts extracranial neurovascular reflexes to stress and which heightens symptoms of motion sickness, increases susceptibility to migraine.

Adult↗
PubMed2004

Staring at one side of the face increases blood flow on that side of the face.

To investigate the effect of observation on blushing, an experimenter sat next to 28 participants and looked closely at one cheek while the participant sang (embarrassing) or read aloud (not embarrassing). Increases in cheek temperature were greater on the observed than the unobserved side during both tasks. Changes in cheek temperature were symmetrical when the experimenter sat next to another 23 participants and looked straight ahead, as well as when the experimenter stared at one side of the participant's face through a glass window while the participant sang. However, increases in cutaneous blood flow were greater on the observed than the unobserved side of the forehead during singing. These findings suggest that staring at one side of the face triggers an ipsilateral increase in facial blood flow.

Adolescent↗
PubMed2004

Involvement of the sympathetic nervous system in complex regional pain syndrome.

Complex regional pain syndrome (CRPS) occasionally develops as a complication of limb trauma. Sympathetic neurotransmitter release is compromised in the affected limb of at least a subgroup of patients throughout the course of the disorder, whereas signs of sympathetic deficit (a warm flushed limb) often evolve into signs of sympathetic overactivity (a cool moist limb) due to the development of adrenergic supersensitivity. Cross-talk between sympathetic neurotransmitters and the sensory neurons that signal pain appears to contribute to CRPS in a subgroup of patients. In addition, sympathetic activity may retard normal healing by aggravating the vascular disturbances associated with inflammation. Sympathetic dysfunction seems to originate from within the central nervous system in patients without peripheral nerve injury, possibly in association with chronic activation of the "defeat" response associated with inhibitory opioid-mediated pain modulation. Fatigue of this inhibitory process may unmask a facilitatory influence of arousal on nociceptive transmission in the thalamus and cortex that contributes to stress-induced pain.

Journal Article↗
PubMed2003

Facilitation of extracranial vasodilatation to limb pain in migraine sufferers.

BACKGROUND: Dilatation of pain-sensitized scalp vessels can cause pain in migraine headache, and extracranial vascular hyperreactivity to psychological stress and head pain could increase susceptibility to attacks. OBJECTIVE: To determine whether changes in facial blood flow differed between migraine sufferers and control subjects during painful stimulation of a limb. METHODS: To document changes in facial blood flow, pulse amplitude was monitored with photoelectric pulse transducers from the frontotemporal region of 23 migraine sufferers and 22 age- and sex-matched control subjects before, during, and after immersion of the nondominant hand in ice water at 2 degrees C for 30 seconds. The hand was immersed three times at 4-minute intervals. RESULTS: Migraine sufferers rated the pain of the ice-water immersion to be more intense and unpleasant than control subjects, and pain radiated further up the arm. Increases in pulse amplitude were greater ipsilateral than contralateral to painful stimulation (25.1 +/- 2.9 vs 13.7 +/- 4.4%; p < 0.01). Pulse amplitude increased over repeated immersions (p < 0.01) and peaked after the hand was removed from the ice water (p < 0.001), more so ipsilaterally than contralaterally (p < 0.001). Pulse amplitude increased 26.3 +/- 4.3% in migraine sufferers compared with 12.6 +/- 4.4% in control subjects (p < 0.05), and this group difference persisted 8 minutes after the final immersion. CONCLUSION: Limb pain triggers increases in facial blood flow and might exacerbate the vascular component of headache during attacks of migraine.

Adolescent↗