Sensory lateralization in pain subjective perception for noxious heat stimulus

The aim of the present study was to identify and characterize hemispheric lateralization for pain intensity perception. A sample of 351 healthy volunteers was tested by the immersion of the right hand for 10 s followed by the same test for the left hand (RL group; n = 199) or in a random sequence (RND group; n = 152) into a water bath (48°C, 15 s). Pain intensity was self-reported by the Visual Analogue Scale (VAS). The motor hemispherical Lateralization Index (LI) was obtained by the Edinburgh Inventory. Gender, hand skin fold, interstimulus time and menstrual cycle data in case of female subjects were recorded. The sample, 60.7% females and 39.3% males, 20.4 &#45 0.18 (mean &#45 SEM) years old, showed 92.1% right-handed subjects. Left hand VAS was significantly higher than right hand VAS for RL (7.24 &#45 1.31 vs 6.74 &#45 1.52; p < 0.01) and RND (7.24 &#45 0.82 vs 6.73 &#45 1.25; p < 0.01) both for right- and left-handed subjects. A low but significant correlation for VAS scores and LI was found ( r = 0.14; p < 0.05 or r = 0.18; p < 0.05, for left or right hand, respectively). Skin fold was statistically similar in both hands ( p > 0.05) being highly correlated with each other ( r = 0.68; p < 0.05). Pain subjective perception was not correlated to interstimulus time ( r = -0.01; p > 0.05). Females showed significantly higher values than males for both left and right hand VAS scores. Periovulatory phase VAS value was significantly higher than luteal phase VAS only for the right hand test (7.57 &#45 0.20 vs 6.47 &#45 0.33; p < 0.01). The results of the present study suggest a lateralization of pain intensity perception to the right hemisphere not correlated with the motor hemispheric lateralization.     

Sensory adaptation for timing perception

Recent sensory experience modifies subjective timing perception. For example, when visual events repeatedly lead auditory events, such as when the sound and video tracks of a movie are out of sync, subsequent vision-leads-audio presentations are reported as more simultaneous. This phenomenon could provide insights into the fundamental problem of how timing is represented in the brain, but the underlying mechanisms are poorly understood. Here, we show that the effect of recent experience on timing perception is not just subjective; recent sensory experience also modifies relative timing discrimination. This result indicates that recent sensory history alters the encoding of relative timing in sensory areas, excluding explanations of the subjective phenomenon based only on decision-level changes. The pattern of changes in timing discrimination suggests the existence of two sensory components, similar to those previously reported for visual spatial attributes: a lateral shift in the nonlinear transducer that maps relative timing into perceptual relative timing and an increase in transducer slope around the exposed timing. The existence of these components would suggest that previous explanations of how recent experience may change the sensory encoding of timing, such as changes in sensory latencies or simple implementations of neural population codes, cannot account for the effect of sensory adaptation on timing perception.     

The effects of pentobarbital, fentanyl-droperidol, ketamine-xylazine and ketamine-diazepam on noxious stimulus perception in adult male rats

The increased use of rats for laboratory studies has increased the urgency for a better understanding of their perception of painful or noxious stimuli and the means of obtunding such stimuli. Four different injectable drugs, pentobarbital, fentanyl-droperidol (Innovar-Vet), ketamine-xylazine and ketamine-diazepam, were evaluated in this study. Unlike previous studies in rodents, this study has quantitated noxious stimulus perception following a temporal sequence of observations. Results showed the greatest inhibition of noxious stimulus perception with Innovar-Vet, lesser inhibition with ketamine-xylazine and ketamine-diazepam, and the least obtunding of nociception with pentobarbital. Results of this study also suggested that a spatial orientation, similar to that present in man, exists within the CNS of rats for receipt of noxious stimulation.     

Repetitive noxious stimulus altered the shadow-induced withdrawal behavior in Lymnaea

Stress alters adaptive behaviors including vigilance behaviors. In Lymnaea one of these vigilance behavior is a heightened withdrawal response to a shadow. The shadow withdrawal response (SWR) is mediated by dermal photoreceptors located primarily on the foot, mantle cavity, and skin around the pneumostome area. Here we asked whether we could obtain a neural correlate of the heightened SWR and other essential behaviors following traumatic stress. We measured the electrophysiological properties of 'Right Pedal Dorsal 11 (RPeD11)', the interneuron that plays a major role in mediating the whole-body withdrawal response. In traumatized snails 24 hours after the trauma they responded not only to a shadow stimulus with an augmented withdrawal response, but suppressed in locomotive, feeding and respiratory behavior. Their behavioral change lasted at least one week. Accompanying the behavioral change in these 'traumatized' preparations there are a number of significant changes in the neuronal properties of RPeD11 compared to na?ve preparations. For example, RPeD11 is significantly more depolarized (～10 mV) has significantly larger input resistance, and the duration of the response elicited by the shadow persists longer. All these changes result in an increased RPeD11 response and seem to raise their defensive alert level.     

The effect of stimulus number on the stability of responses for an extensive heat pain test

Background.?The use of relatively lower stimulus presentation numbers in quantitative sensory testing may influence the computation accuracy of participants’ discriminability. The minimum trial number for obtaining a stabilized participant discrimination ability was determined.

Materials and methods.?Twelve participants’ ability to discriminate between noxious heat stimuli pairs (45°C/46°C, 46°C/47°C, and 47°C/48°C) was assessed using a six-category confidence rating scale. Heat stimuli were administered to the forearm. Two conditions with presentation numbers of 17 trials per stimulus (representing the median number of trials in previous studies) and 40 trials per stimulus (used in a previous study with a similar protocol) were used.

Results and discussion.?Participants’ discriminability stabilized at approximately the 20th trial based on the lowest frequency of indeterminate and non-model conforming results under both conditions. A simple linear regression model showed a statistically significant positive relationship between discriminability for the two conditions (slope?=?0.65, p?<?0.001; constant?=?0.33, p?=?0.02; r^2?=?0.51). As a rule of thumb, approximately 20 trials per stimulus intensity could be used to obtain a stabilized discriminability outcome.     

Sensory modality and time perception in children and adults

This experiment investigated the effect of signal modality on time perception in 5- and 8-year-old children as well as young adults using a duration bisection task in which auditory and visual signals were presented in the same test session and shared common anchor durations. Durations were judged shorter for visual than for auditory signals by all age groups. However, the magnitude of this modality difference was larger in the children than in the adults. Sensitivity to time was also observed to increase with age for both modalities. Taken together, these two observations suggest that the greater modality effect on duration judgments for the children, for whom attentional abilities are considered limited, is the result of visual signals requiring more attentional resources than are needed for the processing of auditory signals. Within the framework of the information-processing model of Scalar Timing Theory, these effects are consistent with a developmental difference in the operation of the "attentional switch" used to transfer pulses from the pacemaker into the accumulator. Specifically, although timing is more automatic for auditory than visual signals in both children and young adults, children have greater difficulty in keeping the switch in the closed state during the timing of visual signals.     

Sound-induced brain activity depends on stimulus subjective salience in female zebra finches

A key point in the study of acoustic perception is whether brain responsiveness to sounds depends on sound acoustic structure or sound perceptive salience. Songbirds provide some evidence that higher auditory regions are sensitive to the subjective importance of the stimulus for the subject. In the present paper, we compare brain activation elicited by mate versus non-mate calls in female zebra finches Taeniopygia guttata. Using playback, we examined the responsiveness of the caudal telencephalon by measuring the evoked expression of the immediate early gene ZENK. Our results show that mate calls elicit a significantly higher ZENK expression than the calls of another male in hippocampus, but not in auditory areas. Using a hierarchical ascending classification, we show that this difference in brain activation is not explained by call acoustic structure, but relies on call identity. Thus, these results give evidence for a genomic response to calls in hippocampus that differentiate between call identity, and not between call structure. Our study gives further insight into the implication of the hippocampus in sound recognition in female songbirds.     

Sex differences of functional lateralization in the perception of verbal and emotional information in ontogeny

Experimental data show certain differences between men and women in perception of verbal and emotional information. They are revealed in the ability of correct perception of definite kind of information, in the degree of brain functional asymmetry in perception of the given information, in prevalence of domination type. The character of sex differences in functional asymmetry changes little with the age; quantitative correlations of the coefficient of asymmetry diminish with the age.     

The cerebral signature for pain perception and its modulation

Our understanding of the neural correlates of pain perception in humans has increased significantly since the advent of neuroimaging. Relating neural activity changes to the varied pain experiences has led to an increased awareness of how factors (e.g., cognition, emotion, context, injury) can separately influence pain perception. Tying this body of knowledge in humans to work in animal models of pain provides an opportunity to determine common features that reliably contribute to pain perception and its modulation. One key system that underpins the ability to change pain intensity is the brainstem's descending modulatory network with its pro- and antinociceptive components. We discuss not only the latest data describing the cerebral signature of pain and its modulation in humans, but also suggest that the brainstem plays a pivotal role in gating the degree of nociceptive transmission so that the resultant pain experienced is appropriate for the particular situation of the individual.     

Aromatization of androgens into estrogens reduces response latency to a noxious thermal stimulus in male quail

We recently demonstrated the presence of estrogen synthase (aromatase) and of estrogen receptors in the dorsal horn (laminae I-II) throughout the rostrocaudal extent of the spinal cord in male and female Japanese quail. The spinal laminae I-II receive and process abundant sensory information elicited, among others, by acute noxious stimulation of the skin and resulting in rapid, reflex-like withdrawal behavior. In the present study, we demonstrate that systemic treatment with estradiol or testosterone markedly decreases the latency of the foot withdrawal in the hot water test. A simultaneous treatment with an aromatase inhibitor blocks the effects of testosterone demonstrating, hence, that they are mediated by a conversion of testosterone into an estrogen by aromatase. Furthermore, the testosterone- or estradiol-induced decrease in foot withdrawal latency is blocked by a treatment with the estradiol receptor antagonist, tamoxifen, indicating that the effects are largely mediated by the interaction of estradiol with estrogen receptors. Together, these data suggest that sex steroids modulate sensitivity to noxious stimuli possibly by a direct action at the level of the dorsal horn of the spinal cord.     

Expertise modulates the perception of pain in others

Perceiving the pain of others activates a large part of the pain matrix in the observer [1]. Because this shared neural representation can lead to empathy or personal distress [2, 3], regulatory mechanisms must operate in people who inflict painful procedures in their practice with patient populations in order to prevent their distress from impairing their ability to be of assistance. In this functional magnetic resonance imaging MRI study, physicians who practice acupuncture were compared to naive participants while observing animated visual stimuli depicting needles being inserted into different body parts, including the mouth region, hands, and feet. Results indicate that the anterior insula somatosensory cortex, periaqueducal gray, and anterior cingulate cortex were significantly activated in the control group, but not in the expert group, who instead showed activation of the medial and superior prefrontal cortices and the temporoparietal junction, involved in emotion regulation and theory of mind.     

TRPM3 is a nociceptor channel involved in the detection of noxious heat

Transient receptor potential melastatin-3 (TRPM3) is a broadly expressed Ca(2+)-permeable nonselective cation channel. Previous work has demonstrated robust activation of TRPM3 by the neuroactive steroid pregnenolone sulfate (PS), but its in?vivo gating mechanisms and functions remained poorly understood. Here, we provide evidence that TRPM3 functions as a chemo- and thermosensor in the somatosensory system. TRPM3 is molecularly and functionally expressed in a large subset of small-diameter sensory neurons from dorsal root and trigeminal ganglia, and mediates the aversive and nocifensive behavioral responses to PS. Moreover, we demonstrate that TRPM3 is steeply activated by heating and underlies heat sensitivity in a subset of sensory neurons. TRPM3-deficient mice exhibited clear deficits in their avoidance responses to noxious heat and in the development of inflammatory heat hyperalgesia. These experiments reveal an unanticipated role for TRPM3 as a thermosensitive nociceptor channel implicated in the detection of noxious heat.