Characteristics of the trigeminal depressor response in cats

We studied the effects of electrical stimulation of the inferior alveolar nerve (IAN) on cardiovascular responses in cats. There was statistical correlation between cardiovascular response and prestimulus mean arterial blood pressure (MABP) and heart rate (HR). A trigeminal depressor response (TDR) was induced when the prestimulus MABP and HR were above 95 mm Hg and 140 beats/min, respectively. We investigated further to identify the vasomotor regulating center and neural transmitters involved in TDR. In the medulla, electrical stimulation of the dorsomedial medulla, the infratrigeminal nucleus (IFT), and the rostral ventrolateral medulla (RVLM) induced a vasopressor response. We confirmed that neurons in the RVLM were retrogradely labeled by wheat germ agglutinin-conjugated horseradish peroxidase injection into the nucleus intermediolateralis of the spinal cord. The vasopressor response induced by IFT stimulation was similar to that induced by IAN stimulation. Vasodepressor responses were induced when the caudal ventrolateral medulla, the nucleus tractus solitarius, the lateral tegmental field, the trigeminal nucleus interpolaris, the trigeminal spinal tract, and the paramedian reticular nucleus were stimulated. These responses, however, were not similar to the vasodepressor response induced by IAN stimulation but were similar to the cardiovascular response induced by vagal afferent stimulation. After spinalization or lesion of the RVLM, MABP and HR decreased and TDR completely disappeared. Inhibitory synaptic ligands and receptors were localized using immunohistochemical techniques. Neurons immunopositive for adrenaline, noradrenaline, and gamma-aminobutyric acid (GABA), and adrenaline alpha(2A), GABA(A), GABA(B), and glycine receptors were distributed along the sympatho-reflexive route including the RVLM and IFT. These results suggest that TDR could be induced as negative feedback to sympathetic hyperactivity whenever MABP and HR are high, because of the inhibitory control of the RVLM.     

Evidence for both reaching and grasping activity in the medial parieto-occipital cortex of the macaque

In humans, the caudal pole of the superior parietal lobule is involved in the control of both reaching and grasping movements, whereas in monkey it is reported to be involved only in the control of reaching. Using single-unit recordings from trained macaque monkeys, we investigated whether area V6A, a visuomotor area located in the caudal part of the posterior parietal cortex, is involved in both components of prehension, the hand transport towards the visual target and the grip formation to secure the grasp. In Experiment 1, neural activity was recorded in V6A while two monkeys performed two instructed-delay reaching tasks (reach-to-point and reach-to-grasp) under controlled conditions in darkness. Fourty-five of 93 tested neurons (48%) were modulated during reach-to-point and 62% (52/84) during reach-to-grasp. In 63% of cells (51/81) neural activity was significantly different between reach-to-point and reach-to-grasp tasks, suggesting that grip formation could influence neural activity. In Experiment 2, two monkeys performed natural reach-to-grasp movements in fully lit environment; V6A neural activity and arm-hand movements were recorded by a digital camcorder and analysed frame-by-frame using a digital video technique. Thirty of the 58 tested neurons (52%) were modulated during natural prehension; about 30% of these neurons (8/30) were modulated only during the last phase of prehension, i.e. during finger flexion around the object to be grasped. This is the first direct demonstration that both reaching and grasping modulate neural activity in the caudal part of the posterior parietal cortex of the macaque. Our work suggests a strict functional homology between human and monkey superior parietal lobule.     

Electroacupuncture induces c-Fos expression in the rostral ventrolateral medulla and periaqueductal gray in cats: relation to opioid containing neurons

Our previous studies have shown that electroacupuncture (EA) at the Neiguan-Jianshi (P5-P6) acupoints inhibits sympathetic outflow and attenuates excitatory visceral cardiovascular reflexes through enkephalin- or beta-endorphin-related opioid receptors in the rostral ventrolateral medulla (rVLM). It is not known whether EA at these acupoints activates neurons containing enkephalin or beta-endorphin in the rVLM as well as in the periaqueductal gray (PAG) that are involved in EA-mediated central neural regulation of sympathetic activity. The present study evaluated activated neurons in the rVLM and PAG by detecting c-Fos immunoreactivity, and identified the relationship between c-Fos nuclei and neuronal structures containing enkephalin or beta-endorphin in these regions. To enhance the detection of cell bodies containing enkephalin or beta-endorphin, colchicine (90-100 microg/kg) was injected into the subarachnoid space in anesthetized cats 28-30 h prior to EA or the sham-operated control for EA. Following bilateral barodenervation and cervical vagotomy, EA (1-4 mA, 2 Hz, 0.5 ms) was performed at the P5-P6 acupoints (overlying median nerve; n=7) for 30 min. Identical procedures, with the exception of electrical stimulation, were carried out in five control animals. EA decreased blood pressure (BP) in four of seven cats (5-15 mm Hg) while the sham procedure for EA produced no responses. Perikarya containing enkephalin were found in the rVLM and rarely in the PAG, while no cell bodies labeled with beta-endorphin were identified in either region. Compared to animals in the control group, more c-Fos immunoreactivity, located principally in close proximity to fibers containing enkephalin or beta-endorphin, was observed in the rVLM and ventrolateral PAG (vlPAG) in EA-treated cats. Moreover, neurons double-labeled with c-Fos and enkephalin in the rVLM were significantly increased in cats following EA stimulation (P<0.05). These data indicate that EA at the P5-P6 acupoints activates neurons in the rVLM and vlPAG. These activated neurons contain enkephalin in the rVLM, and most likely interact with nerve fibers containing enkephalin or beta-endorphin in both the rVLM and vlPAG. The results from this study provide the first anatomical evidence showing that EA at the P5-P6 acupoints has the potential to influence neuronal structures (perikarya, axons and/or dendrites) containing enkephalin or beta-endorphin in specific regions of the brain stem. These neurons likely form the substrate for EA's influence on sympathoexcitatory cardiovascular reflexes.     

Distribution of corticotectal cells in macaque

We compared the cortical inputs to the superficial and deep compartments of the superior colliculus, asking if the corticotectal system, like the colliculus itself, consists of two functional divisions: visual and visuomotor. We made injections of retrograde tracer extending into both superficial and deep layers in three colliculi: the injection site involved mainly the upper quadrant representation in one case, the lower quadrant representation in a second case, and both quadrants in a third. In a fourth colliculus, the tracer injection was restricted to the lower quadrant representation of the superficial layers. After injections involving both superficial and deep layers, labeled cells were seen over V1, many prestriate visual areas, and in prefrontal and posterior parietal cortex. Both the density of labeled cells and the degree of visuotopic order as inferred from the distribution of labeled cells in cortex varied among areas. In visual areas comprising the lower levels of the cortical hierarchy, visuotopy was preserved, whereas in "higher" areas the distribution of labeled cells did not strongly reflect the visuotopic location of the injection. Despite the widespread distribution of labeled cells, there were several areas with few or no labeled cells: MSTd, 7a, VIP, MIP, and TE. In the case with an injection restricted to superficial layers, labeled cells were seen only in V1 and in striate-recipient areas V2, V3, and MT. The results are consistent with the idea that the corticotectal system consists of two largely nonoverlapping components: a visual component consisting of striate cortex and striate-recipient areas, which projects only to the superficial layers, and a visuomotor component consisting of many other prestriate visual areas as well as frontal and parietal visuomotor areas, which projects to the deep compartment of the colliculus.     

Expression and plasticity of galanin systems in cortical neurons, oligodendrocyte progenitors and proliferative zones in normal brain and after spreading depression

Neocortex contains very few galanin neurons but receives a moderate galanin innervation from various subcortical loci. Recent data suggest that galanin helps regulate the tonic neuronal excitability of hippocampus and probably cerebral cortex but relatively little is known about the anatomy and functional regulation of cortical galanin systems. Therefore, we examined, in the rat, the effect of the intense but benign stimulus, cortical spreading depression (CSD), on the expression of galanin and galanin receptors (GalR1 and GalR2) in the neocortex and associated regions, revealing complex, multicellular responses. Thus, following acute, unilateral KCl-induced CSD, a delayed and transient induction (onset after 48 h, lasting approximately 24 h) of galanin mRNA and peptide production occurred across the ipsilateral cerebral cortex in activated oligodendrocyte progenitor cells (OPCs), identified by specific NG2 proteoglycan immunostaining. An increase in GalR1 mRNA, immunoreactivity and receptor binding occurred in neurons within layers II and V of neocortex and in piriform cortex at 7-28 days after CSD, associated with a long-lasting depletion of galanin-positive nerve fibres in these regions. In contrast, GalR2 mRNA expression was largely unaltered after CSD. Additional novel findings in normal, adult brain were the detection of galanin mRNA and immunoreactivity in OPCs within the medial corpus callosum and in immature progenitor cells in the subventricular zone and rostral migratory stream. GalR1 and GalR2 mRNA was also present in these latter regions. These findings and the complex modulation of galanin and galanin receptors in multiple cell types (neurons/OPCs) following acute cortical activation/depression further demonstrate the potential plasticity of neuronal and non-neuronal galanin systems under physiological and pathological conditions and strongly suggest additional functions for this pleiotropic peptide in mammalian brain.     

Generalized deficits in visual selective attention after V4 and TEO lesions in macaques

To test the role of areas V4 and TEO in the attentional filtering of distracting information, we studied the effects of lesions in these areas, in monkeys discriminating target stimuli surrounded by irrelevant distracters. The lesions were restricted, such that a single visual field quadrant was affected by a V4 lesion alone, a TEO lesion alone, or a combined lesion in V4 and TEO, while one quadrant served as a normal control. The monkeys fixated a spot while discriminating the orientation, colour or motion of target stimuli presented extrafoveally in each quadrant. When the target was presented alone, discrimination deficits in the quadrants affected by the lesions were generally small. However, these deficits were substantially increased by surrounding the target with luminance, colour or motion distracters. The discrimination of target orientation was more impaired than the discrimination of target colour or motion, irrespective of distracter type. The discrimination of target motion was strongly affected only by motion distracters. The magnitude of the impairments increased with distracter strength and with the extent to which the distracters conveyed information conflicting with the target. Deficits in the quadrant affected by combined V4 and TEO lesions were twice as large as those in quadrants affected by V4 or TEO lesions alone. The results suggest that in the absence of V4 and TEO, information from both relevant and irrelevant stimuli is 'averaged' together across several different feature domains, impairing the discrimination of the relevant target features. The results suggest a broad role of V4 and TEO in visual selective attention.     

Spatiotemporal activation of the two visual pathways in form discrimination and spatial location: a brain mapping study

To address the question of the relationship between the two visual pathways, a ventral stream for object and form vision and a dorsal stream for spatial and motion vision, we measured the spatiotemporal activation patterns in the two pathways responding to an integrated visuospatial task to which form discrimination and spatial location were assigned simultaneously. The two cognitive components of form discrimination and spatial location were interwoven in the task; however, the fMRI data demonstrated that such a task still activated both ventral GTi/GF (the inferior temporal gyrus/the fusiform gyrus) and dorsal Ga/PCu (the angular gyrus/Precuneus), which are supposed to mediate form discrimination and spatial location, respectively. In addition, the source waveforms of the fMRI foci based on the source analysis of the fMRI-seeded dipole modeling and the moving dipole modeling indicated that in responding to the task combining simultaneously form perception and spatial location, the activity in Ga/PCu begins earlier than that in GTi/GF, but it peaks later and lasts longer.     

Spectral contrasts underlying auditory stream segregation in goldfish (Carassius auratus)

This study investigates the effects of spectral separation of sounds on the ability of goldfish to acquire independent information about two simultaneous complex sources. Goldfish were conditioned to a complex sound made up of two sets of repeated acoustic pulses: a high-frequency pulse with a spectral envelope centered at 625 Hz, and a low-frequency pulse type centered at 240, 305, 390, or 500 Hz. The pulses were presented with each pulse type alternating with an overall pulse repetition rate of 40 pulses per second (pps), and a 20-pps rate between identical pulses. Two control groups were conditioned to the 625-Hz pulse alone, repeated at 40 and 20 pps, respectively. All groups were tested for generalization to the 625-Hz pulse repeated alone at several rates. If the two pulse types in the complex resulted in independent auditory streams, the animals were expected to generalize to the 625-Hz pulse trains as if they were repeated at 20 pps during conditioning. It was hypothesized that as the center frequency of the low-frequency pulse approached that of the 625-Hz pulse, the alternating trains would be perceived as a single auditory stream with a repetition rate of 40 pps. The group conditioned to alternating 625- and 240-Hz pulses generalized least, with maximum generalization at 20 Hz, suggesting that the animals formed at least one perceptual stream with a repetition rate of 20 pps. The other alternating pulse groups generalized to intermediate degrees. Goldfish can segregate at least one "auditory stream" from a complex mixture of sources. Segregation can be based on spectral envelope and grows more robust with growing spectral separation between the simultaneous sources. Auditory stream segregation and auditory scene analysis are shared among human listeners, European starlings, and goldfish, and may be primitive characteristics of the vertebrate sense of hearing.     

人工寒潮对易卒中型肾血管性高血压大鼠凝血和纤溶系统的变化研究

目的观察寒潮时易卒中型肾血管性高血压大鼠（RHRSP）血液中凝血和纤溶系统的活性改变。方法双肾双夹法制作RHRSP模型,分别于寒潮前后取血,酶联免疫吸附测定（ELISA）法检测P-选择素（Ps）、纤维蛋白肽A（FPA）和D-二聚体（DD）含量。结果造模8周后RHRSP血浆中Ps、FPA、DD含量逐渐增高,与假手术组相比差异有统计学意义（P〈0.05）。且Ps、FPA、DD水平在寒潮3 h最高,6 h1、2 h逐渐下降,与RHRSP非寒潮组相比差异有统计学意义（P〈0.05）。结论寒潮时血液中凝血系统和纤溶系统活性改变可能是RHRSP出现脑梗死和/或脑出血,甚至混合性中风的原因之一。     

Self-referential processing influences functional activation during cognitive control: an fMRI study

Rostral anterior cingulate cortex (rACC) plays a central role in the pathophysiology of major depressive disorder (MDD). As we reported in our previous study (Wagner et al., 2006), patients with MDD were characterized by an inability to deactivate this region during cognitive processing leading to a compensatory prefrontal hyperactivation. This hyperactivation in rACC may be related to a deficient inhibitory control of negative self-referential processes, which in turn may interfere with cognitive control task execution and the underlying fronto-cingulate network activation. To test this assumption, a functional magnetic resonance imaging study was conducted in 34 healthy subjects. Univariate and functional connectivity analyses in statistical parametric mapping software 8 were used. Self-referential stimuli and the Stroop task were presented in an event-related design. As hypothesized, rACC was specifically engaged during negative self-referential processing (SRP) and was significantly related to the degree of depressive symptoms in participants. BOLD signal in rACC showed increased valence-dependent (negative vs neutral SRP) interaction with BOLD signal in prefrontal and dorsal anterior cingulate regions during Stroop task performance. This result provides strong support for the notion that enhanced rACC interacts with brain regions involved in cognitive control processes and substantiates our previous interpretation of increased rACC and prefrontal activation in patients during Stroop task.