诱发性耳声发射的掩蔽

３４例听觉正常受试者（共４８耳）进行疏波短声诱发性耳声发射（ＥＯＡＥ）掩蔽实验,项目包括同侧同时掩蔽、同侧后掩蔽和对倒后掩蔽。同时掩蔽的掩蔽声是稳态白噪声,后掩蔽的掩蔽声是宽带噪声。同侧同时掩蔽强度达３０ｄＢＳＬ时,未观察到对ＥＯＡＥ的掩蔽效应,但对主观听觉感受有掩蔽作用,表明ＥＯＡＥ的客观属性反映听觉行为有其局限性、同侧及对侧后掩蔽出现掩蔽效应时的掩蔽强度分别为３０和５０ｄＢＳＬ,掩蔽阈约分别为５９和６８ｄＢＳＬ。耳蜗的机械特性－非线性或耳蜗内存在的某种功能性的反馈调节系统可能是同侧后掩蔽的作用机理。下行的对侧橄榄耳蜗内侧束对外毛细胞主动收缩的抑制性作用,可有效解释对倒后掩蔽的ＥＯＡＥ变化。     

Backward and forward masking in Macaca mulatta.

8 highly trained rhesus monkeys were examined on both backward and forward masking to determine the feasility of studying masking in unrestrained monkeys and of studying perceptual phenomenon without the confounding of linguistic variables. It was found that monkeys could respond well under the given conditions. The data indicated a more pronounced effect of the masking stimulus on backward masking than on forward masking.     

Proactive and retroactive interference in implicit odor memory

To test the hypothesis that longevity of odor memory is due to strong proactive interference (reduction of new learning by prior learning) and to absence of retroactive interference (reduction of prior memory by new learning), subjects, matched in age and gender with those of a previous experiment, were unknowingly exposed in two sessions to the weak concentrations of lavender or orange used before. Implicit odor memory was later tested in a separate experiment. Comparison of the results with those of the previous experiment showed that both proactive and retroactive interference occurred. These results have implications for the general theory about implicit memory for new associations, which may have to be amended when non-verbal material is used. The longevity of odor memory should be explained by the improbability of occurrence of incidences that provoke retroactive interference rather than by the absence of the retroactive interference itself.     

Contralateral Masking in Bilateral Cochlear Implant Patients: A Model of Medial Olivocochlear Function Loss

Contralateral masking is the phenomenon where a masker presented to one ear affects the ability to detect a signal in the opposite ear. For normal hearing listeners, contralateral masking results in masking patterns that are both sharper and dramatically smaller in magnitude than ipsilateral masking. The goal of this study was to investigate whether medial olivocochlear (MOC) efferents are needed for the sharpness and relatively small magnitude of the contralateral masking function. To do this, bilateral cochlear implant patients were tested because, by directly stimulating the auditory nerve, cochlear implants circumvent the effects of the MOC efferents. The results indicated that, as with normal hearing listeners, the contralateral masking function was sharper than the ipsilateral masking function. However, although there was a reduction in the magnitude of the contralateral masking function compared to the ipsilateral masking function, it was relatively modest. This is in sharp contrast to the results of normal hearing listeners where the magnitude of the contralateral masking function is greatly reduced. These results suggest that MOC function may not play a large role in the sharpness of the contralateral masking function but may play a considerable role in the magnitude of the contralateral masking function.     

Cyclic modulation of H-reflex depression in ipsilateral and contralateral soleus muscles during rhythmic arm swing

The objective of the present study was to investigate the effects of rhythmic arm swing on ipsilateral and contralateral soleus motoneuron pool excitability. Ten healthy human subjects participated in this study. Soleus H-reflexes were recorded from the ipsilateral and contralateral soleus muscles while the subject swung the right arm anteroposteriorly as if during gait. The soleus H-reflex was depressed throughout the whole arm swing cycle except in the ipsilateral leg during the onset of the backward arm swing, and in the contralateral leg during the last half of the backward arm swing and the onset of the forward arm swing. The depression was cyclically modulated in accordance with the time course of the arm swing periods, and the pattern of the modulation was reciprocal between the ipsilateral and contralateral legs. This cyclical and reciprocal modulation may be related to the regulation of soleus motoneuron pool excitability during gait.     

Cyclic modulation of H-reflex depression in ipsilateral and contralateral soleus muscles during rhythmic arm swing

The objective of the present study was to investigate the effects of rhythmic arm swing on ipsilateral and contralateral soleus motoneuron pool excitability. Ten healthy human subjects participated in this study. Soleus H-reflexes were recorded from the ipsilateral and contralateral soleus muscles while the subject swung the right arm anteroposteriorly as if during gait. The soleus H-reflex was depressed throughout the whole arm swing cycle except in the ipsilateral leg during the onset of the backward arm swing, and in the contralateral leg during the last half of the backward arm swing and the onset of the forward arm swing. The depression was cyclically modulated in accordance with the time course of the arm swing periods, and the pattern of the modulation was reciprocal between the ipsilateral and contralateral legs. This cyclical and reciprocal modulation may be related to the regulation of soleus motoneuron pool excitability during gait.     

Recognition of forward-masked complex and simple images

The accuracy and time of motor response in tests for visual recognition of simple (sets of horizontal and vertical lines, angles, and crosses) and complex (contour images of animate and inanimate objects) images forward-masked with stimuli of varying complexity were estimated in psychophysiological experiments. It was found that forward masking impaired recognition, the mask whose complexity was close to that of the given test image being the most efficient in each particular case. The masking effect was the strongest in the experiments where the sets of test and masking images coincided. Recognition of complex images proved to be more resistant to masking than recognition of simple images. The observed effects of forward masking are assumed to be determined by lateral inhibition and changes in the excitability cycle. The relative contributions of these mechanisms depend on the degree of similarity between the test and masking stimuli, as well as the hierarchical level of the visual cortex at which the test stimulus is “targeted.”     

Modulation of backward pattern masking by focal visual attention

The effect of focal visual attention on backward pattern masking was investigated using an orientation discrimination task. The results show that attention reduces primarily the effect of interruption masking, the later component of pattern masking, which occurs when the delay between the target and mask onset is about 50-150 ms. The strongest spatial cueing effect, i.e. the strongest reduction of the orientation discrimination threshold due to focal attention, was observed at intermediate (approximately 100 ms) target-to-mask stimulus onset asynchrony (SOA). There was a weak effect of cueing at shorter SOAs, and no or a very weak attentional effect was present at longer target-to-mask SOAs, where the pattern masking effect is absent. The dynamics of attentional modulation of backward pattern masking correlates closely with the dynamics of the attentional modulation of neuronal responses in the early visual cortex.     

Use of backward masking test for the study of visual information processing in healthy subjects and schizophrenic patients

The study of 14 healthy subjects and 15 schizophrenic patients was conducted under visual backward masking conditions. Sensory thresholds were identified using the method of constant stimuli. A special modification of the backward masking technique with lateralized presentation of test and masking stimuli was used to study the lateral characteristics of visual attention. It was found that the thresholds of letter stimulus identification were significantly higher in patients with schizophrenia than in healthy subjects. Only in patients the asymmetry of visual perception was revealed with the higher recognition thresholds in the left visual hemifield. The overall data analysis suggests an association between increased recognition thresholds in schizophrenic patients and changes in the interruption mechanism functioning at the neocortex level.     

Rapid iconic erasure without masking

We report on the erasure of the iconic memory of an array of 12 black letters flashed on a continuously- present white field. Erasure is accomplished by replacing the 16 ms letter array (frame 1) with a blank white frame for 16 ms (frame 2). The letter array returns in frame 3, with from one to six letters missing. Report of the missing letters is accurate without the blank white frame but is impoverished with it, as if interposing the blank erases the icon. Erasure occurs without any obvious luminance masking, 'mud splashes', pattern masking (backward, forward, or metacontrast), lateral masking, or masking by object substitution. Erasure is greatly decreased if the blank is presented one frame earlier or later. We speculate that erasure is due to a rapid reset of the icon produced by an informational mis-match.     

Vergleich zweier Modelle für laterale Inhibition

Summary Two semi-linear models for lateral inhibition are discussed. The interaction between receptor units is assumed to be linear, as demonstrated by Hartline and Ratliff in the eye of the horseshoe crab Limulus polyphemus. Yet a model of such an inhibitory system must be nonlinear, since the output values correspond to nerve activities, which cannot be negativ. Models with forward inhibition were used often to describe contrast phenomena in the human nervous system. However, in order to simulate the input-output relation in systems similar to the eye of Limulus, a model with backward inhibition must be constructed. Two important properties of backward inhibition not shared by forward inhibition are: (1) Inhibition in a receptor unit has an influence upon its excitation, as well as upon its ability to inhibit other units (Disinhibition). (2) The range of interaction between sensory units is not necessarily the same as the range of direct cross connections. It is shown in this paper, that also forward inhibition may possess these two properties, provided that it is repeated on subsequent levels. Some properties of systems with backward and forward inhibition are studied and compared in models consisting of three units. The input-output relation for large systems with backward inhibition was calculated under special assumptions concerning the inhibitory coefficients. If the inhibitory coefficients in a system with backward inhibition decrease like a power series, as a function of the distance between receptor units, only neighboring receptors have an effect upon each other. That is, in an equivalent system with forward inhibition the inhibitory interaction is confined to neighbouring receptors. Conversely, when backward inhibition exists only between neighbouring receptors, the inhibitory coefficients in an equivalent system with forward inhibition are described, as a function of the distance between the receptor units, by a power series with alternating sign.     

Changes in the direct and interhemispheric responses of the pyramidal tract after tetanization of the cortex and lateral hypothalamus

Changes in pyramidal tract response after unilateral neocortical and lateral hypothalamic tetanization were analyzed in unanesthetized and nonimmobilized rabbits. Membrane and synaptic modifications were revealed in intra- and interhemispheric connections. Changes in excitability of callosal collaterals of pyramidal tract neurons in contralateral hemisphere and changes in somatodendritic excitability in ipsilateral hemisphere could be oppositely directed. Plasticity of callosal connections may contribute to the interhemispheric asymmetry during learning.     

Associative interference between cues and between outcomes presented together and presented apart: an integration

In recent years, 'stimulus competition' in the study of acquired behavior has referred exclusively to (a) associative competition between cues trained in compound (e.g. overshadowing and blocking). Rarely cited are older experiments cast in the verbal learning tradition, now complemented with data from humans and rats in Pavlovian preparations, that demonstrate (b) competition between cues separately trained with a common outcome (i.e. proactive and retroactive interference). Similarly neglected are numerous examples of (c) competition between outcomes separately trained with a common cue within the verbal learning literature (also proactive and retroactive interference) as well as within the Pavlovian literature (i.e. counterconditioning). Recent data demonstrate (d) competition between outcomes trained in compound, thereby completing the four cells of a 2x2 matrix (competing stimuli trained together vs. trained apart and the competing stimuli being cues or outcomes) which highlights the ubiquitous nature of associative stimulus interference/competition. Most contemporary theories of acquired behavior can account for the phenomena in one or at most two cells of this matrix. Whether a common mechanism underlies the phenomena in all four cells of the matrix is currently unclear, but until such time as data preclude a common mechanism, parsimony encourages efforts to develop a model that encompasses all four cells. Here we offer a tentative model that addresses all four cells, albeit with two processes.     

Critical ratio: effects of contralateral masking on normal and pathological ears]

In order to evaluate the central interferences on the auditory efficiency, the effect of contralateral masking noise on Critical Ratio (CR) has been studied in 14 normal ears (control group), in 12 ears with cochlear disorders and in 6 with retrocochlear lesion (acoustic neuromas); in all cases the impairment was unilateral, while the other ear was normal. CR values were calculated for 1 KHz pulsed tones (duration 500 ms, rise/fall 25 ms, duty cycle of 50%); the masking noise was a wide band (90-20,000 Hz) delivered at 40 dB SL. The results have demonstrated that in the presence of contralateral masking noise, CRs don't modify both in the normal ears and in those with retrocochlear disorder, whereas they increase, almost always, in ears with cochlear deafness. These results demonstrate that the involvement of central auditory pathways, because of contralateral noise, makes the auditory efficiency worse, only in ears with cochlear dysfunctions; this behaviour seems to confirm the peripheral origin of CR.     

后掩蔽效应对大棕蝠下丘神经元声反应的影响

以回声定位蝙蝠为模式动物,采用在体动物细胞外单位记录法,研究了后掩蔽效应对下丘神经元声反应的影响。结果显示,部分神经元(38％,12／31)对测试声刺激的反应明显受到掩蔽声的抑制,其后掩蔽效应强弱与掩蔽声和测试声的相对强度差(inter-stimulus level difference,SLD),以及测试声与掩蔽声之间的间隔时间(inter-stimulus onset asynchrony,SOA)有关：当掩蔽声强度升高或测试声强度降低时,后掩蔽效应增强;而SOA的缩短,亦可见后掩蔽效应增强。另外,相当数量的神经元(52%,16／31)对测试声刺激的反应并不受掩蔽声的影响,其中有的神经元只有在特定SLD和SOA时,才表现出后掩蔽效应。而少数下丘神经元(10％,3／31)在特定SLD和SOA时,掩蔽声对测试声反应有易化作用。上述结果表明,部分下丘神经元参与了声认知活动中的后掩蔽形成过程,推测下丘神经元在定型声反应特性中,对掩蔽声诱导的兴奋前抑制性输入与测试声诱导的兴奋性输入之间的时相性动态整合起关键作用。     

Spectrum and coherent characteristics of bioelectric activity of the brain in women with normal and complicated pregnancy

Spectrum and coherent EEG analysis was performed in 86 pregnant women on the 35-36th week of gestation. It was shown that functional interhemispheric brain asymmetry is a sensitive index of normal and complicated gestation. It was found out that activation prevailing in the central and temporal brain areas contralateral to the side of placenta localization in the uterus was characteristic of the normal pregnancy. The development of gestation complications was accompanied by the inversion of interhemispheric asymmetry of EEG activation. It was suggested that correlative properties of bioelectric brain activity in women with normal gestation are an indicator of the left-hemispheric dominance of brain centers in the integration process.     

Asymmetry of Tactile Perception and Interhemispheric Interactions in Stutterers

The effect of inverse masking on the skin of the left and right hands and of bimanual reverse masking during coordinated work of both hands in stutterers was studied to detect the changes in cerebral asymmetry related to stuttering. The study showed that (1) asymmetry of tactile perception is absent in stutterers in the conditions of masking; it is supposed that when stuttering begins in early childhood, the formation of the hemispheric specialization in performing both sensory (all modalities) and speech functions is interrupted; (2) stuttering right-handers demonstrate a strongly levotropic nature of the interhemispheric interactions under conditions of bimanual masking, which testifies to a more considerable retardation of the perception of a test stimulus in the stutterers' left hemisphere under the influence of the masking stimulus in the right hemisphere than in right-handers with normal speech. It is assumed on this basis that stuttering begins because of the combination of symmetry and asymmetry in the interhemispheric relations. There is a hypothetical model that supposes that the phenomenon of stuttering is caused by two fundamental factors, namely, bilateral symmetry (existence of two identical speech centers in the right and left hemispheres) and a specific levotropic asymmetry of the interhemispheric relations, i.e., a more manifest influence of the right hemisphere on the left hemisphere in stutterers. This conditions the emergence of two identical speech impulses that appear with long intervals between them, which cause a dissonance in the functioning of the speech-forming apparatus.     

Interhemispheric motor asymmetry of conditioned feedback

The interhemispheric asymmetry and lateralization of motor functions, as applied to backward conditioning, was studied in two dogs that afterwards turned to be a right-hander and a left-hander. In the process of food-procuring instrumental conditioning it was revealed that one of the dogs predominantly used the right paw (with the dominance of the left hemisphere) and the second animal used the left paw (the right brain hemisphere dominated). The earliest signs of lateralization of the motor functions were observed in the backward conditioned connections (which had been formed earlier than the direct connections or direct conditioned reflexes). Consequently, the presence and sign of asymmetry can be predicted on the basis of manifestation of the backward connections observed at the early stages of acquisition of food-procuring behavior. The backward connections are strictly specific and have the same lateralization as the direct ones.     

The status of conditioned reflex activity in cats after unilateral vestibular neurotomy]

In chronic experiments on 6 cats the influence was studied of unilateral vestibular neurotomy on conditioned, oculographic and electrocardiographic reactions. In operated animals appeared sharply expressed posetonic and oculomotor disturbances, lowered general functional brain state, what was manifested in an increase of specific weight of slow spindle-shaped rhythmics and lowering of the conditioned activity level. Against the background of the lowered functional brain state interhemispheric asymmetry developed with relative predominance of the contralateral hemisphere, what was reflected in electrocorticographic manifestations and disturbance of conditioned spatial differentiations. Significance is grounded of the appearing interhemispheric asymmetry in the development of disturbances of spatial analysis in operated animals.