The RULER model. Is this how the somatosensory cortex works?

Despite a wealth of information, it is still not known how neurones in the different neocortical layers interact to produce a conscious perception. We now put forward a model for the somatosensory cortex in which a touch is perceived whenever superficial cortical pyramidal cells (in layers II and III) are made to discharge by a recurrent input from deep pyramidal neurones (in layer V). The superficial cells act as biological amplifiers and the number discharging will depend both on the strength of the message from the thalamus and on the variable background depolarisation of their apical dendrites. The recurrent volley arises in the layer V neurones at the end of an IPSP (inhibitory postsynaptic potential), which itself follows an excitatory response induced by the incoming thalamic signal; the IPSP is generated by local basket cells. The duration of the initial excitation--IPSP--late excitation sequence corresponds to a time chunk, that is, the period over which neural activity is integrated to produce a perception. During the time chunk, the superficial cortical pyramids, unlike the deeper ones, can accumulate information as subthreshold excitatory postsynaptic potentials (EPSPs). The relative time at which the information arrived in the cortex is roughly coded by the gradient of EPSPs among cells in an axis perpendicular to the cortical surface. Although developed for the somatosensory cortex, the basic features of the model may well apply to other sensory receiving areas of the cortex.     

Area-specific representation of mechanical nociceptive stimuli within SI cortex of squirrel monkeys

While functional imaging studies in humans have consistently reported activation of primary somatosensory cortex (SI) with painful stimuli, the specific roles of subdivisions of areas 3a, 3b, and 1 within SI during pain perception are largely unknown, particularly in the representation of mechanical evoked pain. In this study, we investigated how modality, location, and intensity of nociceptive stimuli are represented within SI by using high-spatial resolution optical imaging of intrinsic signals in Pentothal-anesthetized squirrel monkeys. Perceptually comparable mechanical nociceptive and innocuous tactile stimuli were delivered by indenting the glabrous skin of the distal finger pads with 0.2 and 2 mm diameter probes, respectively. Within each of areas 3a, 3b, and 1, activations to mechanical nociceptive stimulation of individual distal finger pads were spatially distinct and somatotopically organized. We observed differential cortical activation patterns. Areas 3a, 3b, and 1 were all activated during mechanical nociceptive stimulation and were modulated by nociceptive stimulus intensity. However, with innocuous tactile stimulation, mainly areas 3b and 1 exhibited response modulation with different levels of stimulation. In summary, mechanical nociceptive inputs are area-specific and topographically represented within SI. We propose that all areas of SI are implicated in encoding the features of mechanical nociception, where areas 3a and 3b are distinctively involved in coding nociceptive and pressure sensation components of stimulation.     

新生儿黄疸系统护理措施效果研究

目的探讨有效的新生儿黄疸系统性临床护理措施。方法112例新生儿黄疸患儿被随机分为系统护理组和对照组,系统护理组实施水疗、抚触和光疗,对照组实施常规护理措施,比较两组新生儿排便情况和血清胆红素水平变化。结果系统护理组的新生儿在干预前2天排便次数明显多于对照组,干预后血清总胆红素水平显著低于对照组（P〈0．05）。结论系统护理能有效帮助新生儿快速降低体内胆红素水平,防止并发症的发生。     

Brain dynamics for perception of tactile allodynia (touch-induced pain) in postherpetic neuralgia

Postherpetic neuralgia (PHN) is a debilitating chronic pain condition often accompanied by a sensation of pain when the affected region is touched (tactile allodynia). Here we identify brain regions involved in stimulus-induced touch-evoked pain (dynamical mechanical allodynia, DMA), compare brain activity between DMA and spontaneous pain (described earlier for the same patients in [Geha PY, Baliki MN, Chialvo DR, Harden RN, Paice JA, Apkarian AV. Brain activity for spontaneous pain of postherpetic neuralgia and its modulation by lidocaine patch therapy. Pain 2007;128:88-100]), delineate regions that specifically code the magnitude of perceived allodynia, and show the transformation of allodynia-related information in the brain as a time-evolving network. Eleven PHN patients were studied for DMA and its modulation with Lidoderm therapy (patches of 5% lidocaine applied to the PHN affected body part). Continuous ratings of pain while the affected body part was brushed during fMRI were contrasted with non-painful touch when brushing was applied to an equivalent opposite body site, and with fluctuations of a bar observed during scanning, at three sessions relative to Lidoderm treatment. Lidoderm treatment did not decrease DMA ratings but did decrease spontaneous pain. Multiple brain areas showed preferential activity for allodynia. However, mainly responses in the bilateral putamen and left medial temporal gyrus were related to the magnitude of allodynia. Both DMA and spontaneous pain perceptions were best represented within the same sub-cortical structures but with minimal overlap, implying that PHN pain modulates behavioral learning and hedonics. These results have important clinical implications regarding adequate therapy.     

Poke and pop: Tactile–visual synchrony increases visual saliency

The majority of studies investigating interactions between vision and touch have typically explored single events, presenting one object at a time. The present study investigates how tactile–visual interactions affect competition between multiple visual objects in more dynamic cluttered environments. Participants searched for a horizontal or vertical line segment among distractor line segments of various orientations, all continuously changing color. Search times and search slopes were substantially reduced when the target color change was accompanied by a tactile signal. These benefits were observed even though the tactile signal was uninformative about the location, orientation, or color of the visual target. We conclude that tactile–visual synchrony guides attention in multiple object environments by increasing the saliency of the visual event.     

Visuotactile temporal order judgments in ageing

We report an experiment on the effects of ageing on crossmodal temporal perception. Young (mean age = 21.7 years) and old (mean age = 75.1 years) participants were presented with pairs of visual and vibrotactile stimuli to either hand and required to make unspeeded temporal order judgments (TOJs) regarding which sensory modality appeared to have been presented first. The stimulus onset asynchrony (SOA) between the two stimuli was varied using the method of constant stimuli. Temporal precision, as indexed by the just noticeable difference (JND), was better (i.e., JNDs were lower) when the stimuli were presented from different positions (M = 101 ms) rather than from the same position (M = 120 ms), as has been demonstrated previously. Additionally, older observers required more time (i.e., their JNDs were larger) to accurately perceive the temporal order (M = 131 ms) as compared to younger observers (M = 98 ms). Our results confirm that ageing deleteriously affects crossmodal temporal processing even when the spatial confound inherent in previous research has been ruled out.     

Shifts of attention in the early blind: an erp study of attentional control processes in the absence of visual spatial information

To investigate the role of visual spatial information in the control of spatial attention, event-related brain potentials (ERPs) were recorded during a tactile attention task for a group of totally blind participants who were either congenitally blind or had lost vision during infancy, and for an age-matched, sighted control group who performed the task in the dark. Participants had to shift attention to the left or right hand (as indicated by an auditory cue presented at the start of each trial) in order to detect infrequent tactile targets delivered to this hand. Effects of tactile attention on the processing of tactile events, as reflected by attentional modulations of somatosensory ERPs to tactile stimuli, were very similar for early blind and sighted participants, suggesting that the capacity to selectively process tactile information from one hand versus the other does not differ systematically between the blind and the sighted. ERPs measured during the cue-target interval revealed an anterior directing attention negativity (ADAN) that was present for the early blind group as well as for the sighted control group. In contrast, the subsequent posterior late direction attention negativity (LDAP) was absent in both groups. These results suggest that these two components reflect functionally distinct attentional control mechanisms which differ in their dependence on the availability of visually coded representations of external space.     

Tactile intensity and population codes

An important question in neuroscience is how different aspects of a stimulus are encoded at different stages of neural processing. In this review, I discuss studies investigating the peripheral neural code for perceived intensity in touch. One of the recurrent themes in this line of research is that information about stimulus intensity is encoded in the activity of populations of neurons. Not only is information integrated across afferents of a given type, but information is also combined across submodalities to yield a unified percept of stimulus intensity. The convergence of information stemming from multiple submodalities is particularly interesting in light of the fact that these are generally thought to be parallel sensory channels with distinct sensory functions and little cross-channel interactions. I discuss implications of a recently proposed model of intensity coding for psychophysical functions and for the coding of intensity in cortex. I also briefly review the peripheral coding of intensity in other sensory modalities.     

乳腺癌前哨淋巴结术中印片细胞学评估

目的评价印片细胞学在乳腺癌前哨淋巴结活检术中的病理诊断价值。方法选择105例早期乳腺癌患者行前哨淋巴结活检,其中成功101例。沿前哨淋巴结长轴每隔2～3 mm剖开,每个剖面均进行印片细胞学检查,印片使用HE染色,印片后的淋巴结分别送石蜡切片,将印片结果与石蜡的HE染色结果进行比对比较。结果105例患者前哨淋巴结活检的检出率为96.2%(101/ 105),101例患者中共检出202枚前哨淋巴结。在常规石蜡切片作为诊断标准时,前哨淋巴结术中印片细胞学的敏感性、特异性、准确性、阳性及阴性预测值分别为92.1%、98.8%、97.5%、94.6%和98.2%,101例患者的印片敏感性、特异性、准确性、阳性及阴性预测值分别为89.3%、98.6%、96.0%、96.2%和96.0%。将术中印片结果与进一步的连续切片结果进行比对,前哨淋巴结印片的敏感性、特异性、准确性、阳性及阴性预测值分别为83.3%、98.8%、95.5%、94.6%和95.8%,101例患者的印片敏感性、特异性、准确性、阳性及阴性预测值分别为81.3%、100.0%、94.1%、100.0%和92.0%。结论印片细胞学对乳腺癌前哨淋巴结术中病理诊断有较高的价值,可以准确提供术中诊断信息,与石蜡切片有很高的一致性。