Three different approaches, each with different theoretical assumptions, were used to show that mammalian neuronal spike trains contain serial ordering. When intervals are categorized according to whether their durati...
详细信息
Three different approaches, each with different theoretical assumptions, were used to show that mammalian neuronal spike trains contain serial ordering. When intervals are categorized according to whether their durations are short, medium or long, sequential groupings of adjacent interval categories exhibit Markov dependencies, extending to at least the 4th order. The observed incidence of specified patterns of these groups of adjacent interval categories differs from the independent case, based on Chi square goodness-of-fit tests, and by using similar procedures. There is divergence from independence when adjacent interval patterns are described in terms of relative lengths of adjacent intervals. The statistical indicators of serial dependence were significantly greater when applied to the original data than when applied to the same data after shuffling. Each of these approaches leads to the notion that information is carried in clusters of adjacent intervals (bytes or words) and the specific patterns of interspike intervals which contribute most to the statistical significance (i.e., those clusters that are potential candidates for information carriers). In most of the 10 neurons, the memory of the system appears to be at least 36-45 ms.
Properties of the human mechanoreceptors in the hairy skin of the back of the hand were studied by microelectrode measurements from the radial nerve. Correlations of unit activity with sensations elicited by tactile p...
详细信息
Properties of the human mechanoreceptors in the hairy skin of the back of the hand were studied by microelectrode measurements from the radial nerve. Correlations of unit activity with sensations elicited by tactile pulses (single cycle sinusoids of 20, 60 and 150 Hz) were examined with simultaneous measurements of unit activity and sensation thresholds and magnitude. A total of 264 mechanoreceptive units was identified. Of all units, 66% were classified as slowly adapting (SA) and 34% as rapidly adapting (RA) units. Mechanical thresholds of the units as well as simultaneously measured sensation thresholds decreased with increasing frequency of the pulse. The thresholds of several SA units were identical with the subjective thresholds. The responses of the units to supraliminal pulses consisted maximally of 7 impulses. Most SAI and RA units were able to code to some extent the stimulus amplitude on the basis of number of impulses, but only RA units had stimulus-response functions indicating velocity coding. Comparisons of the estimates of sensation magnitude with the number of impulses in the response indicated that the estimate may be based mainly on activity in a population of RA units. The comparison of the present results with earlier reports on properties of receptors in the glabrous skin of the human hand indicates that there are some differences between the characteristics of receptors in the hairy and glabrous skin. Human receptors in the hairy skin do not seem to differ from the corresponding receptors in the animals.
The time required for rats to make a behavioral taste discrimination was predicted from neural discharge rates and tested using conditioned aversion. Predictions were based on the hypothesis that the responses evoked ...
详细信息
The time required for rats to make a behavioral taste discrimination was predicted from neural discharge rates and tested using conditioned aversion. Predictions were based on the hypothesis that the responses evoked from a neural population by two different chemicals must diverge by a certain critical total number of spikes before the chemicals are discriminable. This total could be derived from the responses of all neurons in the population. Behavioral discrimination times generally supported predictions made from second-order (bulbar) neural responses, but were ambiguous concerning predictions based on fourth-order (thalamic) responses. The implications of these results for the possible functions of bulbar and thalamic taste neurons is discussed.
The roles of the geniculostriate system and the superior colliculus in determining the critical flicker frequency (CFF) in cats were studied by subtotal lesions and electrical recordings in these respective areas. Les...
详细信息
The roles of the geniculostriate system and the superior colliculus in determining the critical flicker frequency (CFF) in cats were studied by subtotal lesions and electrical recordings in these respective areas. Lesions in the former uniformly decreased CFF; lesions in the latter usually were followed by increased CFF, which could have been due to continued training. These results suggested that the geniculostriate system mediated high frequencies of flicker, while the colliculus could mediate only lower frequencies. Photic following activity, defined as time-integrated power measurements of the fundamental flicker frequencies in the EEGs of these two areas, occurred reliably at suprathreshold frequencies in the cortex and at much lower frequencies in the colliculus. A quantitative relationship between CFF and photic following activity by these visual mechanisms was also noted. The data further support the view that the function of these visual components in the determination of CFF in the intact cat differ, and suggest the possibility that the colliculus may serve as a filter to limit the the discrimination of high flicker rates.
The broad responsiveness of single taste fibers to different classes of chemical stimuli has provided strong evidence against interpretations according to the classical doctrine of quality-specific fiber types. An alt...
详细信息
The broad responsiveness of single taste fibers to different classes of chemical stimuli has provided strong evidence against interpretations according to the classical doctrine of quality-specific fiber types. An alternative suggested by Pfaffmann was later developed as an "across-fiber patterning'' model by Erickson. Rats were found able to behaviorally discriminate among taste stimuli in accord with predictions based on comparing the responses of many single fibers to several different stimuli;with many fibers responding to a particular stimulus, the differential responsiveness of each fiber to a number of stimuli thus appeared to be the basis for encoding stimulus quality. The replicability and generality of Erickson''s finding was tested using the Virginia opossum as an experimental subject;a behavioral measure suitable to this species was developed for the purpose. The results are in aggrement with those obtained from rats and offer evidence for the generality of across-fiber pattern coding in mammalian gustation. Although certain differences appear in comparing single fiber data from rat and opossum, results of a "neural response function" analysis do not suggest any fundamental differences in the gustatory coding mechanisms of the 2 species.
Application of a brief stimulus produces long-lasting changes in the transmembrane potential of a Limulus retinular cell when steady hyperpolarizing current is also being applied. The steady current holds the cell in ...
详细信息
Application of a brief stimulus produces long-lasting changes in the transmembrane potential of a Limulus retinular cell when steady hyperpolarizing current is also being applied. The steady current holds the cell in one of two stable states, depending upon current strength. Any brief stimulus can trigger the cell from either state into the other for long periods of time, after which the cell returns to the pre-stimulus state. A sensitivity change is associated with the state change; this suggests that such activity might be a means of information storage.
Laboratory rats, either made anosmic or subjected to sham operations, were later rendered capable of discriminative preference for NaCl over an equimolar LiCl solution. During a series of two-bottle tests (NaCl opposi...
详细信息
Laboratory rats, either made anosmic or subjected to sham operations, were later rendered capable of discriminative preference for NaCl over an equimolar LiCl solution. During a series of two-bottle tests (NaCl opposite LiCl), the importance of olfaction relative to that of taste in the discrimination was determined by such measures as initial fluid intakes, first min alternations, and first min fluid intakes. The rats proved able to distinguish by taste between the solutions, and olfactory cues were neither required nor important in the discrimination.
The hyperpolarizing response (HPR), an increase in membrane resistance elicited by extrinsic current, is associated with an inexcitable state of the neuronal membrane. This change in membrane excitability suggests a m...
详细信息
The hyperpolarizing response (HPR), an increase in membrane resistance elicited by extrinsic current, is associated with an inexcitable state of the neuronal membrane. This change in membrane excitability suggests a mechanism wherein the HPR could serve as the memory trace.
We have studied the response properties of peripheral myelinated fibers ending in the hairy skin of the Rhesus monkey, activated by sinusoidal mechanical stimulation. In parallel experiments we measured thresholds of ...
详细信息
The human capacity to scale the intensity of brief mechanical indentations of the hairy skin was measured by the method of subjective magnitude estimation. The afferent discharges evoked by nearly identical stimuli de...
详细信息
暂无评论