Interhemispheric visual competition after multisensory reversal of hemianopia

Unilateral lesions of visual cortex have the secondary consequence of suppressing visual circuits in the midbrain superior colliculus (SC), collectively producing blindness in contralesional space (“hemianopia”). Recent studies have demonstrated that SC visual responses and contralesional vision can be reinstated by a non‐invasive multisensory training procedure in which spatiotemporally concordant visual‐auditory pairs are repeatedly presented within the blind hemifield. Despite this recovery of visual responsiveness, the loss of visual cortex was expected to result in permanent deficits in that hemifield, especially when visual events in both hemifields compete for attention and access to the brain's visuomotor circuitry. This was evaluated in the present study in a visual choice paradigm in which the two visual hemifields of recovered cats were simultaneously stimulated with equally valent visual targets. Surprisingly, the expected disparity was not found, and some animals even preferred stimuli presented in the previously blind hemifield. This preference persisted across multiple stimulus intensity levels and there was no indication that animals were less aware of cues in the previously blind hemifield than in its spared counterpart. Furthermore, when auditory cues were combined with visual cues, the enhanced performance they produced on a visual task was no greater in the normal than in the previously blind hemifield. These observations suggest that the multisensory rehabilitation paradigm revealed greater inherent visual information processing potential in the previously blind hemifield than was believed possible given the loss of visual cortex.     

耳穴脉冲刺激对Oddi括约肌张力及肌电活动的影响

目的　探讨耳穴脉冲电刺激治疗胆石症 ,胆绞痛的机制 .方法　选用 15条成年杂种犬 ,进行耳穴体表脉冲刺激与缩胆素 (CCK)对在体狗胆囊张力 ,Oddi括约肌张力及肌电活动影响的对比研究 .结果　耳穴脉冲电刺激对胆囊张力无明显影响 [(1.2 7± 0 .2 6 ) k Pa与 (1.2 4± 0 .2 2 ) k Pa,P<0 .0 5 ],CCK注射液能明显提高胆囊张力 [(1.2 7± 0 .2 6 ) k Pa与 (1.91± 0 .39) k Pa,P<0 .0 5 ],CCK注射液能明显降低Oddi括约肌张力 [(2 .2 4± 0 .5 5 ) k Pa与 (1.5 8± 0 .5 6 ) k Pa,P>0 .0 5 ]及肌电活动 .结论　耳穴脉冲电刺激同 CCK一样 ,均对 Oddi括约肌的张力有显著的降低作用 ,并减少 Oddi括约肌的肌电峰电位爆发波的频率与电压值 ,推测其对胆绞痛有治疗作用 ,并有助于胆结石的排石过程 .     

Conditioned locomotion and place preference elicited by tactile cues paired exclusively with morphine in an open field

A novel version of the conditioned place preference (CPP) technique was used in an attempt to determine whether tactile stimuli previously associated with morphine elicit approach and sustained contact. Empirical support for this view has been equivocal, prompting some to question the validity of the CPP technique. In the present study, rats received, during conditioning, morphine (10 mg/kg, IP) paired exclusively with an open field floor made of four quadrants of one texture (CS+) and saline with another floor made of four quadrants of a different texture (CS–). On the test for CPP, rats were given saline and placed in an open field containing either 1, 2, or 4 quadrants of the CS+ (with 3, 2, 0 quadrants of the CS–, respectively). These animals showed high absolute CPP scores on the test, spending, on average, as much as 83% and 75% of their time on the CS+ when two and one CS+ quadrants, respectively, were present. Concurrent measures of activity indicated that animals were most active when all four quadrants were CS+ and least active when zero or one CS+ quadrant was present. Thus, once an animal approached and made contact with the CS+ it tended to maintain contact with this stimulus and to reduce its approach to and contact with other stimuli. The differentiating features of this version of the CPP technique, as well as the relationship between morphine-induced conditioned locomotion and CPP, are discussed.     

Effects of stimulation and blockade of dopamine receptor subtypes on the discriminative stimulus properties of cocaine

The involvement of dopamine (DA) receptor subtypes in the behavioral effects of CNS stimulants was studied in rats trained to discriminate occaine from saline. In substitution tests, the stimulus effects of 10mg/kg of this substance generalized tod-amphetamine (0.25–1.0 mg/kg) and the selective D₂ against LY-171555 (0.05–0.25 mg/kg); but not to the D₁ agonist SKF-38393 (5.0–15.0 mg/kg); in combination tests, the D₁ antagonist Sch-23390 (0.0625–0.5 mg/kg) significantly blocked, and the D₂ antagonist spiperone (0.25–0.5 mg/kg) partially blocked the cocaine cue. These data suggest that the involvement of DA systems in the behavioral effects of cocaine is more complex than either D₁ or D₂ receptor activation; for example, the stimulus properties of this substance might involve both D₁ and D₂ receptor activation.Some of these results were presented at the meeting of the Society for Neuroscience, Toronto, 1988     

刺激兔扣带回对尾核头部痛相关单位电活动的影响

实验在15只家兔上进行。以玻璃微电极记录尾核头部(DHCN)痛相关单位,刺激扣带回,观察痛相关单位电活动的变化。在70只DHCN痛相关单位中,有44个对刺激扣带回表现兴奋反应(62.9％),17个呈抑制反应(24.3％),9个变化不明显(12.8％)。进一步观察了52只痛相关单位,在刺激扣带回后再施伤害刺激,43个原痛兴奋单位中15个转为抑制(34.9％),16个进一步兴奋(37.2％)12个无变化(27.9％);原9个痛抑制单位,8个转为兴奋,1个变化不明显。提示,扣带回可通过其下行活动,调制伤害性冲动在尾核水平上的传递。     

Influence of peripheral afferents on cortical and spinal motoneuron excitability.

The objective of this study was to establish to what extent muscle, cutaneous, and joint afferents alter the excitability of spinal and cortical motor neurons. This question was examined by studying the impact of electrical stimulation of the second and third digits, the median nerve at the wrist, and the recurrent thenar motor branch on the F/H and magneto-electrical cortical motor responses (MEPs) of the thenar muscles. The firing frequencies of single F/H motor unit action potentials were unaltered by the foregoing conditioning peripheral stimuli. MEPs conditioned by motor threshold stimulation of the median nerve at the wrist or the recurrent motor branch were significantly increased in size at conditioning to test intervals of 50 to 80 milliseconds. No significant change in MEP size resulted from conditioning stimulation of the digital nerves. We conclude that muscle afferents were primarily responsible for the increase in MEP size. Conditioning stimuli may allow examiners to assess central motor conduction where it would otherwise be impossible.     

The shell region of the nucleus ovoidalis: a subdivision of the avian auditory thalamus.

The connectivity of a region surrounding the established thalamic auditory nuclei, n. ovoidalis (Ov) and n. semilunaris parovoidalis (SPO), was explored in the ring dove by using the anterograde tracers, Phaseolus vulgaris leucoagglutinin (PHAL) and biocytin, and the retrograde tracer, fluorogold. The Ov-SPO surround received a projection from a cell group along the interface of the auditory midbrain and the n. intercollicularis, as revealed with PHAL and biocytin, and was composed of neurons exhibiting a common morphology. These features and the presence of overlapping projections from different portions of the Ov-SPO surround suggest that this region comprises a functionally discrete area, which we term the Ov shell. Single unit recording within the shell established the existence of acoustically responsive units. Both PHAL and fluorogold labeling revealed a robust projection from the Ov shell to the caudomedial hypothalamus. Major telencephalic projections of the shell terminated within the ventral paleostriatal complex, "end-zones" of the field L, the caudomedial hyperstriatum ventrale, and regions immediately dorsal and lateral to the auditory neostriatum. Except for a portion of the shell bordering medial ovoidalis, PHAL injections into the shell also labeled fibers within the caudolateral neostriatum and along the lateral neostriatal rim. The connectivity of the Ov shell suggests that this region may integrate auditory pathways with brain regions associated with endocrine mediated behavior. In addition, the shell may constitute a source of converging input to several levels of central auditory pathways.     

阅读困难儿童脑功能侧化的研究—汉语双耳分听测试

本研究以汉语字词作为刺激材料，利用双耳分听的手段，探讨阅读困难儿童脑功能侧化，发现阅读困难儿童处理简单汉语刺激表现出左耳优势（ｌｅｆｔｅａｒａｄｖａｎｔａｇｅ），与对照组没有差异，而处理复杂汉语刺激则未表现出耳优势（Ｎｏｅａｒａｄｖａｎｔａｇｅ），与对照组差异有显著性。支持阅读困难儿童双侧半球均过度激活的假说。     

THE INTERACTION OF RESPONSES IN THE BRAIN TO SEMANTIC STIMULI

Long time-constant EEG recording during paired stimuli has led to the discovery of the contingent negative variation or expectancy wave (Walter, 1964). This effect is produced when a conditional stimulus signals that an imperative stimulus demanding action, decision, or attention will follow at a short, constant time interval. Symbolic and meaningful stimuli were presented to subjects tachistoscopically, and the evoked responses in the brain were electronically averaged. The cerebral evoked responses to such psychological stimuli are more complex than to flashes. A slow negative DC potential shift (CNV) was seen during the interval between an auditory ready signal and the visual exposure if recognition of the stimulus was required, or if it was interesting. Following the visual exposure, a slow positive DC shift occurred. The method has been developed to study the brain responses to psychological stimuli. The amplitude of the responses relates to the information content and subjective factors rather than to the physical strength of the stimulus.     

Conditioned taste aversions: generalization to taste mixtures

Rats were trained to take their daily water ration within a 30-min session, during which the number of licks per 10-sec presentation of a drinking tube could be recorded. During one of these sessions, one of three stimuli (sucrose, NaCl or HCl) was presented, followed by the administration of cyclophosphamide to produce a conditioned taste aversion. When tested with mixtures of the conditioned stimulus (CS) with the other two stimuli and also with quinine hydrochloride, the animals avoided mixtures containing the CS in proportion to its concentration in the mixture. Although the natural preferences and aversions for these stimuli interacted somewhat with the learned taste aversions, rats responded to the presence of a CS in a mixture and did not generalize to other stimuli not containing the CS. Thus, the generalization of conditioned taste aversions provides a good measure of the behavioral similarities among gustatory stimuli.