Adaptation of the binocular rivalry mechanism

The completeness of binocular rivalry suppression was measured by recording the fraction of a trial during which targets were perceived as alternating in their entirety, rather than blending together into a composite. It was found that the completeness of rivalry declines with prolonged stimulation. A control condition in which subjects saw the same grating targets, but without rivalry, resulted in no decrement. The phenomenon was spatial-frequency specific. The results suggest that binocular rivalry suppression is mediated by a cooperative mechanism which is susceptible to adaptation

Relationships between climate and winter cereal grain quality in Finland and their potential for forecasting

Many studies have demonstrated the effects of climate on cereal yield, but there has been little work carried out examining the relationships between climate and cereal grain quality on a national scale. In this study national mean hectolitre weight for both rye and winter wheat in Finland was modelled using monthly gridded accumulated snow depth, precipitation rate, solar radiation and temperature over the period 1971 to 2001. Variables with significant relationships in correlation analysis both before and after difference detrending were further investigated using forward stepwise regression. For rye, March snow depth, and June and July solar radiation accounted for 66% of the year-to-year variance in hectolitre weight, and for winter wheat January snow depth, June solar radiation and August temperature accounted for 62% of the interannual variance in hectolitre weight. Further analysis of national variety trials and weather station data was used to support proposed biological mechanisms. Finally a cross validation technique was used to test forecast models with those variables available by early July by making predictions of above or below the mean hectolitre weight. Analysis of the contingency tables for these predictions indicated that national hectolitre weight forecasts are feasible for both cereals in advance of harvest

The vibrations of texture

The Pacinian channel has been implicated in the perception of fine textures (Hollins et al., Somatosens Mot Res 18: 253–262, 2001a). In the present study, we investigate candidate codes for Pacinian-mediated roughness perception. We use a Hall effect transducer to record the vibrations elicited in the skin when a set of textured surfaces is passively presented to the index finger. The peak frequency of the vibrations is found to decrease systematically as spatial period increases. The power of the vibrations—weighted according to the spectral sensitivity of the Pacinian system—increases with spatial period for all but the coarsest surfaces. By varying the scanning velocity, we manipulate the temporal and intensive characteristics of the texture-induced vibrations and assess the effect of the manipulation on perceived roughness. We find that doubling the scanning velocity does not result in the substantial decrease in roughness predicted by a frequency theory of vibrotactile roughness perception. On the other hand, the effects of speed on roughness match those of speed on power. We propose that the roughness of a fine surface (spatial period<200 μm) is a function of the Pacinian-weighted power of the vibrations it elicits

Is touch gating due to sensory or cognitive interference?

Touch gating, the attenuation of tactile sensitivity in the presence of pain, is a well-documented phenomenon but its mechanism is unknown. The ability of pain to capture attention suggests that touch gating may be an example of distraction; but the fact that pain raises tactile but not auditory thresholds argues that touch gating is a form of somatosensory interaction. Therefore, the present study was carried out to determine whether touch gating is the result of sensory or cognitive interference. Touch gating was repeatedly produced by delivering a co-localized painful heat stimulus (45°C) during forced-choice measurements of vibration threshold on the palm. Noxious heat significantly increased thresholds compared to those measured at normal skin temperature, and this interference did not decline over the course of an extended series of experiments during which pain intensity significantly habituated. Touch gating was thus related to the constant physical intensity, rather than the changing subjective intensity, of the noxious stimulus. For comparison, a form of unambiguously cognitive interference, the Stroop effect, was also measured repeatedly; it declined significantly across sessions, unlike touch gating interference. Finally, touch gating was not correlated with measures of participants’ distractibility, fear of pain, hypervigilance, or anxiety – variables previously found to influence pain on a cognitive level. Taken together, the results suggest that touch gating is a robust, stimulus-locked form of sensory interaction, rather than a transitory result of distraction or other cognitive processes

Somatosensory Coding of Roughness: The Effect of Texture Adaptation in Direct and Indirect Touch

To examine somatosensory mechanisms contributing to the perception of roughness, subjects examined surfaces with rigorously specified spatial textures under conditions of direct moving contact between the fingertip and the surface (direct touch) and contact through a rigid probe (indirect touch). Subjects were trained to scan the surfaces along a consistent path and with a speed of 2.7 cm/s. With each mode of touch, periods of prolonged inspection of a single adapting surface were followed by shorter periods in which the roughness of multiple test surfaces was reported. Adaptation caused a drop in perceived roughness under conditions of indirect touch, reflecting the reduced sensitivity of vibrotactile mechanisms that are the main recipients of textural information transmitted through the probe. During direct touch, adaptation had no significant effect on the perception of textures with spatial period >200 mum, which are spatially encoded. The results have an important implication for the physiological basis of the spatial code, which is believed to involve somatosensory cortical neurons with highly structured receptive fields: these cortical populations appear to be less susceptible to adaptation than otherwise similar neuronal populations in the visual system

Changes in pain from a repetitive thermal stimulus: The roles of adaptation and sensitization

This study examined processes that contribute to the changing painfulness of a repeatedly presented thermal (heat) stimulus. The 3-s pulses were presented to the side of the hand at a rate of 4/min, too slow to engage wind-up. Over the course of 32 trials, pain intensity (measured by verbal report on a 0–100 scale) first declined and then (in most cases) rose again, indicating adaptation and sensitization, respectively. The magnitude of adaptation grew across a series of three runs, indicating that adaptation has a slow as well as a fast component. The rate of sensitization depended on stimulus temperature, but not on subjective pain intensity; this result implies that sensitization takes place at an early processing stage. Adaptation and sensitization were comparable in participants with fibromyalgia (FM), temporomandibular disorders (TMD), and in healthy controls (HC), indicating these processes occur before the perceptual amplification that characterizes FM and TMD. The ability of vibration to reduce pain has previously been shown to involve segmental inhibition; the finding in the present study that vibratory gating of pain is significantly (inversely) related to the rate of sensitization suggests that the latter also reflects segmental processes. Several lines of evidence thus point to the conclusion that adaptation and sensitization occur at early stages of sensory information processing

Temporomandibular Disorder Modifies Cortical Response to Tactile Stimulation

Individuals with temporomandibular disorder (TMD) suffer from persistent facial pain and exhibit abnormal sensitivity to tactile stimulation. To better understand the pathophysiological mechanisms underlying TMD, we investigated cortical correlates of this abnormal sensitivity to touch. Using functional magnetic resonance imaging (fMRI), we recorded cortical responses evoked by low frequency vibration of the index finger in subjects with TMD and in healthy controls (HC). Distinct subregions of contralateral SI, SII, and insular cortex responded maximally for each group. Although the stimulus was inaudible, primary auditory cortex was activated in TMDs. TMDs also showed greater activation bilaterally in anterior cingulate cortex and contralaterally in the amygdala. Differences between TMDs and HCs in responses evoked by innocuous vibrotactile stimulation within SI, SII, and the insula paralleled previously reported differences in responses evoked by noxious and innocuous stimulation, respectively, in healthy individuals. This unexpected result may reflect a disruption of the normal balance between central resources dedicated to processing innocuous and noxious input, manifesting itself as increased readiness of the pain matrix for activation by even innocuous input. Activation of the amygdala in our TMD group could reflect the establishment of aversive associations with tactile stimulation due to the persistence of pain

Compassion for others, self-compassion, quality of life and mental well-being measures and their association with compassion fatigue and burnout in student midwives: A quantitative survey

Backgroundcompassion fatigue and burnout can impact on the performance of midwives, with this quantitative paper exploring the relationship between self-compassion, burnout, compassion fatigue, self-judgement, self-kindness, compassion for others, professional quality of life and well-being of student midwives.Methoda quantitative survey measured relationships using questionnaires: (1) Professional Quality of Life Scale; (2) Self-Compassion Scale; (3) Short Warwick and Edinburgh Mental Well-being Scale; (4) Compassion For Others Scale.Participantsa purposive and convenience sample of student midwives (n=103) studying at university participated in the study.Resultsjust over half of the sample reported above average scores for burnout. The results indicate that student midwives who report higher scores on the self-judgement sub-scale are less compassionate towards both themselves and others, have reduced well-being, and report greater burnout and compassion fatigue. Student midwives who report high on measures of self-compassion and well-being report less compassion fatigue and burnout.Conclusionstudent midwives may find benefit from ‘being kinder to self’ in times of suffering, which could potentially help them to prepare for the emotional demands of practice and study.Implicationsdeveloping, creating and cultivating environments that foster compassionate care for self and others may play a significant role in helping midwives face the rigours of education and clinical practice during their degree programm

A pilot study exploring the relationship between self-compassion, self-judgement, self-kindness, compassion, professional quality of life and wellbeing among UK community nurses

Background: Compassion fatigue and burnout can impact on performance of nurses. This paper explores the relationship between self-compassion, self-judgement, self-kindness, compassion, professional quality of life, and wellbeing among community nurses.Aim: To measure associations between self-compassion, compassion fatigue, wellbeing, and burnout in community nurses.Method: Quantitative data were collected using standardised psychometric questionnaires: (1) Professional Quality of Life Scale; (2) Self-Compassion Scale; (3) short Warwick Edinburgh Mental Wellbeing Scale; (4) Compassion For Others Scale, used to measure relationships between self-compassion, compassion fatigue, wellbeing, and burnout. Participants: A cross sectional sample of registered community nurses (n=37) studying for a postgraduate diploma at a University in the North of England took part in this study.Results: Results show that community nurses who score high on measures of self-compassion and wellbeing, also report less burnout. Greater compassion satisfaction was also positively associated with compassion for others, and wellbeing, whilst also being negatively correlated with burnout. Conclusion: High levels of self-compassion were linked with lower levels of burnout. Furthermore when community nurses have greater compassion satisfaction they also report more compassion for others, increased wellbeing, and less burnout. The implications of this are discussed alongside suggestions for the promotion of greater compassion