Habituation of the proleg withdrawal reflex in Manduca sexta does not involve changes in motoneuron properties or depression at the sensorimotor synapse

Larvae of the hawkmoth, Manduca sexta, exhibit a defensive proleg withdrawal reflex in which deflection of mechanosensory hairs on the proleg tip (the planta) evokes retraction of the proleg. A previous behavioral study showed that this reflex habituates in response to repeated planta hair deflection and exhibits several other defining features of habituation. In a semi-intact preparation consisting of a proleg and its associated segmental ganglion, repeated deflection of a planta hair or electrical stimulation of its sensory neuron causes a neural correlate of habituation, manifested as a decrease in the number of action potentials evoked in the proleg motor nerve. Monosynaptic connections from planta hair sensory neurons to the principal planta retractor motoneuron exhibit several forms of activity-dependent plasticity. In the present study we recorded intracellularly from this motoneuron during repetitive electrical stimulation of a planta hair sensory neuron. The number of action potentials evoked in the motoneuron decreased significantly, representing a neural correlate of habituation. The motoneuron's resting membrane potential, input resistance. and spike threshold measured before and after repetitive stimulation did not differ between the stimulated group and a control group. Furthermore, the amplitude of the monosynaptic excitatory postsynaptic potential, as well as the magnitude of paired-pulse facilitation, evoked in the motoneuron by the sensory neuron did not change after repetitive stimulation. These results suggest that depression at the sensorimotor synapse does not contribute to reflex habituation. Rather, other mechanisms in the ganglion of the stimulated segment, such as changes in polysynaptic reflex pathways, appear to be responsible.     

The biological efficacy of the transfer function

The most popular neural network strategy is back propagation. This strategy initiated general interest in neural networks among researchers. While back propagation can solve nonlinear problems, it is considered to be a poor example of neuron functioning. Recently, Gardner (1993) has made a strong case for a back propagating phenomenon in networks of living neurons. In this paper, we present a few simple computational examples that investigate another component of the typical back propagation network. The effects of varying transfer functions are illustrated along with the resulting variations in possible synaptic weights. Graphic presentations in 3-D space of the relationship between transfer functions and synaptic weights suggest neural analogies of cell-firing rate and network control.     

Individual differences in concept learning and brain event-related potentials

An irrelevant auditory probe procedure was employed to evoke brain event-related potentials (ERPs) in 56 males while they learned concepts presented to them in study booklets. A mastery test was administered to assess concept acquisition. Ss were divided into two groups according to whether or not their achievement test results were above or below the average score for all learners. A one-way multivariate analysis of variance (MANOVA) was computed for each presentation page employing as multiple dependent measures ERP amplitudes which corresponded to specific concepts. MANOVAs and their subsequent statistics revealed that, as theorized, ERPs evoked at the right frontal, temporal and parietal, as well as the left parietal, regions, significantly distinguished below-from above-average concept learners. As hypothesized, poorer concept learners engaged these hemispheric sites less, and manifested more variability at them, than better learners. It was established that the frontal, temporal and parietal areas which are chiefly implicated in crystallized intelligence are engaged during the actual process of concept learning itself.     

Insights into a molecular switch that gates sensory neuron synapses during habituation in Aplysia

This review focuses on synaptic depression at sensory neuron-to-motor neuron synapses in the defensive withdrawal circuit of Aplysia as a model system for analysis of molecular mechanisms of sensory gating and habituation. We address the following topics:1. Of various possible mechanisms that might underlie depression at these sensory neuron-to-motor neuron synapses in Aplysia, historically the most widely-accepted explanation has been depletion of the readily releasable pool of vesicles. Depletion is also believed to account for synaptic depression at long interstimulus intervals in a variety of other systems.2. Multiple lines of evidence now indicate that vesicle depletion is not an important contributing mechanism to synaptic depression at Aplysia sensory neuron-to-motor neuron synapses. More generally, it appears that vesicle depletion does not contribute substantially to depression that occurs with those stimulus patterns that are typically used in studying behavioral habituation.3. Recent evidence suggests that at these sensory neuron-to-motor neuron synapses in Aplysia, synaptic depression is mediated by an activity-dependent, but release-independent, switching of individual release sites to a silent state. This switching off of release sites is initiated by Ca²⁺ influx during individual action potentials. We discuss signaling proteins that may be regulated by Ca²⁺ during the silencing of release sites that underlies synaptic depression.4. Bursts of 2–4 action potentials in presynaptic sensory neurons in Aplysia prevent the switching off of release sites via a mechanism called “burst-dependent protection” from synaptic depression.5. This molecular switch may explain the sensory gating that allows animals to discriminate which stimuli are innocuous and appropriate to ignore and which stimuli are more important and should continue to elicit responses.     

Before and beyond dialogicality: Transformative trialectics of human dialogues

I first revisit Bakhtin's discourse-driven account of dialogue to situate the concept in its broad sociohistorical, political, and philosophical (i.e., epistemology-ontology-ethics-aesthetics-praxis) meaning context. Not only is the concept of dialogicality highly relevant for the psychology of difference but it also poses many strong meta/theoretical challenges. Second, therefore, I rapidly evaluate psychology's disciplinary developmental status and transformative potentials of Bakhtinian dialogicalism in/for psychological discourses. I pay particular attention to the (im)possibilities of a potential dialogue between psycho-logic/-logy and dia-logic/-logue in reference to our biosociocultural (real-symbolic-imaginary) human be(com)ings. Thus, while triangulating, reframing and refracting with/in my seemingly more radically pluralist and dynamic perspective, using some core notions from its conceptual matrix for(potentially) self-reflective transformative-transformations, such as triopus and transformational trialectics, it is hoped that the fascination with pragmatics of dialogicality would not overshadow the concept's hermeneutically transformative utility which asks for serious dialogical confrontations, insights, bold philosophical commitments and consistent knowledge-practices in/towards all areas of our human(e) worlds.     

记忆过程中海马CA1区神经元的集群放电特征

观察空间工作记忆过程中海马CA1区神经元群的放电特征。应用多通道神经元集群放电记录技术, 同步观察和记录清醒大鼠在执行延迟选择任务时的行为轨迹以及海马CA1区神经元的放电活动。发现：海马CA1区位置细胞的位置野是在学习过程中逐渐形成并可消退; 部分位置细胞的放电对未来目标定向性行为具有预测作用; 在空间工作记忆过程中, 神经元放电之间的相关性加强, 神经元之间以及神经元与局部场电位之间存在相位编码方式。结果提示海马CA1区神经元参与对空间信息的初级编码和加工, 并为未来行为决策提供有效信息, 而且海马对信息的加工是通过局部神经网络进行, 时间编码可能是海马信息加工的重要方式之一。     

Neuronal manifestation of two-way connections in conditioning

Neuronal characteristics of two-way conditional connections were studied in chronic experiments with alert cats during different types of alimentary conditional reflexes. Single unit and multi-unit activities were chronically recorded in the visual and motor cortex and the lateral hypothalamic nucleus. Cross-correlational analysis of neuronal impulse trains was used to characterize the organization of neuron groups in brain structures involved in the formation of a conditional reflex. The experimental data showed an increase in the number of neuronal two-way connections after learning in all three investigated coordinations: visual-motor, visual-hypothalamic, and motor-hypothalamic. With visual-motor interneuronal coordination, the strengthening of two-way connections was due to the enhancement of connections from the motor to the visual neuron (backward connections); with visual- and motor-hypothalamic coordination, the number of interneuronal connections was equal in both directions. In all investigated coordinations, the analysis of the temporal parameters of the interactions between the neurons of different groups showed a dependence of the conditioning procedure on delays of up to 30 ms and a dependence of the motivational state on the interval range of 90–100 ms. The polyfunctional and polycomponent character of two-way neuronal connections in conditioning can be inferred from these data. Evaluation of the activity of neurons of different brain structures suggests the specific organization of intracortical and cortical-subcortical integrity in learning.     

Ludwik Fleck and the concept of style in the natural sciences

Ludwik Fleck is a pioneer of the contemporary social constructionist trend in scientific theory, where his central concept of thinking style has become standard fare. Yet the concept is too often misunderstood and simplified with serious consequences not only for Fleck studies. My essay situates Fleck??s concept of thinking style in the historical context of the 1920s and ??30s, when the notion of style was first applied to the natural sciences, in order to illustrate the uniqueness of Fleck??s concept among the uses of style by his contemporaries and, finally, to examine the epistemological, methodological, and political consequences of this distinction.     

Information encoding in short firing rate epochs by single neurons in the primate temporal visual cortex

Abstract

The information available about face identity from the firing rate and from temporal encoding in the spike train of single neurons recorded in the temporal lobe visual cortical areas of rhesus macaques was analysed using principal component and information theory analyses of smoothed spike trains. The neurons analysed had responses selective for faces. The stimulus set consisted of 20 different faces. The first principal component provided by a considerable extent the most information (57%) available in principal components 1–5, with the second adding 18%, the third 16%, and the fourth and fifth adding 9%. For each image, the weighting on the first principal component was highly correlated with the mean firing rate of the neuron to that image. The information available from the firing rate of the neuron was very close to that available in the first principal component. Information theory analysis showed that in short epochs (e.g. 50 msec) the information available from the firing rate can be as high, on average, as 65% of that available from the firing rate calculated over 400 msec, and 38% of that available from principal components 1–3 in the 400-msec period. It was also found that 30% of the information calculated from the first three principal components is available in the firing rates calculated over epochs as short as 20 msec. More information was available near the start of the neuronal response, and the information available from short epochs became less later in the neuronal response. Taken together, these analyses provide evidence that a short period of firing taken close to the start of the neuronal response provides a reasonable proportion of the total information that would be available if a long period of neuronal firing (e.g. 400 msec) were utilized to extract it, even if temporal encoding were used. The implications of these and related findings are that at least for rapid object recognition, each cortical stage provides information to the next in a short period of 20–50 msec, does not rely on temporal encoding, and completes sufficient computation to provide an output to the next stage in this same 20- to 50-msec period.     

Coherence versus fragmentation in the development of the concept of force

This article aims to contribute to the literature on conceptual change by engaging in direct theoretical and empirical comparison of contrasting views. We take up the question of whether naïve physical ideas are coherent or fragmented, building specifically on recent work supporting claims of coherence with respect to the concept of force by Ioannides and Vosniadou [Ioannides, C., & Vosniadou, C. (2002). The changing meanings of force. Cognitive Science Quarterly 2, 5-61]. We first engage in a theoretical inquiry on the nature of coherence and fragmentation, concluding that these terms are not well-defined, and proposing a set of issues that may be better specified. The issues have to do with contextuality, which concerns the range of contexts in which a concept (meaning, model, theory) applies, and relational structure, which is how elements of a concept (meaning, model, or theory) relate to one another. We further propose an enhanced theoretical and empirical accountability for what and how much one needs to say in order to have specified a concept. Vague specification of the meaning of a concept can lead to many kinds of difficulties.Empirically, we conducted two studies. A study patterned closely on Ioannides and Vosniadou's work (which we call a quasi-replication) failed to confirm their operationalizations of “coherent.” An extension study, based on a more encompassing specification of the concept of force, showed three kinds of results: (1) Subjects attend to more features than mentioned by Ioannides and Vosniadou, and they changed answers systematically based on these features; (2) We found substantial differences in the way subjects thought about the new contexts we asked about, which undermined claims for homogeneity within even the category of subjects (having one particular meaning associated with “force”) that best survived our quasi-replication; (3) We found much reasoning of subjects about forces that cannot be accounted for by the meanings specified by Ioannides and Vosniadou. All in all, we argue that, with a greater attention to contextuality and with an appropriately broad specification of the meaning of a concept like force, Ioannides and Vosniadou's claims to have demonstrated coherence seem strongly undermined. Students’ ideas are not random and chaotic; but neither are they simply described and strongly systematic.     

Beyond sensorimotor segregation: On mirror neurons and social affordance space tracking

Mirror neuron research has come a long way since the early 1990s, and many theorists are now stressing the heterogeneity and complexity of the sensorimotor properties of fronto-parietal circuits. However, core aspects of the initial ‘mirror mechanism’ theory, i.e. the idea of a symmetric encapsulated mirroring function translating sensory action perceptions into motor formats, still appears to be shaping much of the debate. This article challenges the empirical plausibility of the sensorimotor segregation implicit in the original mirror metaphor. It is proposed instead that the teleological organization found in the broader fronto-parietal circuits might be inherently sensorimotor. Thus the idea of an independent ‘purely perceptual’ goal understanding process is questioned. Further, it is hypothesized that the often asymmetric, heterogeneous and contextually modulated mirror and canonical neurons support a function of multisensory mapping and tracking of the perceiving agents affordance space. Such a shift in the interpretative framework offers a different theoretical handle on how sensorimotor processes might ground various aspects of intentional action choice and social cognition. Mirror neurons would under the proposed “social affordance model” be seen as dynamic parts of larger circuits, which support tracking of currently shared and competing action possibilities. These circuits support action selection processes—but also our understanding of the options and action potentials that we and perhaps others have in the affordance space. In terms of social cognition ‘mirror’ circuits might thus help us understand not only the intentional actions others are actually performing—but also what they could have done, did not do and might do shortly.     

Locus of the redundant-signals effect in bimodal divided attention: A neurophysiological analysis

We reanalyzed the data from the study of Lamarre, Busby, and Spidalieri (1983). In that study, the activity of single neurons in area 4 of the motor cortex was recorded during a bimodal detection task in which a monkey (Macaca mulatta)had to respond as quickly as possible to a visual or an auditory signal or to both (redundant trials). Manual responses on redundant trials were speeded by the presence of both signals, as is typically found. The times between signal onsets and the first changes in neuronal activity were also speeded by redundant signals, but there was no difference between redundant-signals and single-signal trials in the time between the change in neuronal activity and movement onset. These results suggest that late motor processes are not speeded by redundant signals in bimodal detection tasks.     

What kinds of alternative possibilities are required of the folk concept(s) of choice?

Our concept of choice is integral to the way we understand others and ourselves, especially when considering ourselves as free and responsible agents. Despite the importance of this concept, there has been little empirical work on it. In this paper we report four experiments that provide evidence for two concepts of choice—namely, a concept of choice that is operative in the phrase having a choice and another that is operative in the phrase making a choice. The experiments indicate that the two concepts of choice can be differentiated from each other on the basis of the kind of alternatives to which each is sensitive. The results indicate that the folk concept of choice is more nuanced than has been assumed. This new, empirically informed understanding of the folk concept of choice has important implications for debates concerning free will, responsibility, and other debates spanning psychology and philosophy.     

Coding of luminance and color differences on neurons in the rabbit's visual system

The neuronal activity in the rabbit's visual cortex, lateral geniculate nucleus and superior colliculus was investigated in responses to 8 color stimuli changes in pairs. This activity consisted of phasic responses (50-90 and 130-300 Ms after stimuli changes) and tonic response (after 300 Ms). The phasic responses used as a basis for the matrices (8 x 8) constructed for each neuron included the average of spikes/sec in responses to all stimuli changes. All matrices were treated by factor analysis and the basic axes of sensory spaces were revealed. Sensory spaces reconstructed from neuronal spike discharges had a two-dimensional (with brightness and darkness axes) or four-dimensional (with two color and two achromatic axes) structure. Thus it allowed us to split neurons into groups measuring only brightness differences and the measuring of color and brightness differences between stimuli. The tonic component of most of the neurons in the lateral geniculate nucleus showed linear correlation with changes in intensities; therefore, these neurons could be characterized as pre-detectors for cortical selective detectors. The neuronal spaces demonstrated a coincidence with spaces revealed by other methods. This fact may reflect the general principle of vector coding (Sokolov, 2000) of sensory information in the visual system.     

Operant conditioning of an in vitro CNS-pneumostome preparation of Lymnaea

Operant conditioning of aerial respiratory behaviour and its consolidation into long-term memory in Lymnaea has been previously studied in both intact, freely moving snails and in in vitro preparations made from previously trained snails. Here, we show in previously untrained semi-intact in vitro Lymnaea preparations that aerial respiratory behaviour can also be operantly conditioned. Neither yoked control nor 'run-down' control procedures in these in vitro preparations result in an alteration of aerial respiratory behaviour. Memory in the operantly trained semi-intact preparations persists for at least 1h after training. Intracellular recordings made from RPeD1, one of the 3-CPG neurons and the neuron that initiates CPG activity; show that there are specific changes in central excitatory input to this neuron concurrent with learning and its consolidation into memory. In addition following the acquisition of learning and its consolidation into memory the ability of RPeD1 and VI/J neurons when depolarized to cause a pneumostome opening is significantly decreased. Thus, previously untrained in vitro semi-intact preparations can be used to study changes in neuronal activity in a neuron known to be both necessary for the behaviour and for memory formation.     

Clarifying and measuring the concept of traditional vs. egalitarian roles in marriages

To clarify and develop a measure of the concept of traditional vs. egalitarian marriages, a 13-item scale was developed and administered to two traditional groups (N=35) and three egalitarian groups (N=51), and then to four cross-validation groups (N=52). Two distinct factors or dimensions were identified. In both analyses the traditional and egalitarian groups were significantly different on the first factor, designated “the leader,” and not on the second, socioemotional factor. Reliability and initial validity of the scale in measuring leadership in the marital dyad are thus demonstrated. However, the concept of traditional vs. egalitarian marriages either needs to be narrowed to refer to leadership only or there needs to be empirical demonstration that other dimensions can be fruitfully included.     

Storage and later recognition of exemplars of concepts

This paper concerns the problem of abstraction: whether when we encounter several exemplars of a concept, we retain only the abstracted concept, only the exemplars, or both. Although many studies concur that both are stored, a recent article argued strongly that only the abstracted concept is stored. The present study, aimed at replication of this recent finding, follows the earlier procedural details but adds appropriate controls and uses simpler material. A set of 24 exemplars of four concepts, in the form of four-tuples of letters and numbers, was presented to Ss who, after presentation, rated a larger set of exemplars for recognition. One group of Ss experienced the conceptual exemplars; control group Ss experienced items that were similar in composition but not exemplars of a concept. Two major results appeared: Unlike the study on which this was based, all Ss were able to distinguish those items that were originally experienced from those that were not. And, the more completely an exemplar fit the concept (the longer the item), the more confident the S was that it had been presented. In contrast, in the control condition, the longer the item, the more confident the S was that it had not been presented earlier. Two models are described to account for these results. One is based on the S's initial storage of the exemplars in a concept-plus-correction format; the other is based on a procedure whereby the S can make recognition judgments without having previously abstracted and retained the concepts.     

Electroconvulsive stimulations prevent stress-induced morphological changes in the hippocampus

Stress can precipitate major depression and other disorders linked to hippocampal shrinkage. It is hypothesized but not established that treatment of these disorders reverses and prevents the hippocampal changes. Dendritic retraction of individual neurons might in concert with other pathophysiological events contribute to the shrinkage phenomenon. Animal studies have shown that various stress paradigms can induce dendritic retraction in the CA3 pyramidal neurons of the hippocampus. Since electroconvulsive treatment is the most effective treatment in humans with major depression, we investigated whether repeated electroconvulsive stimulations (ECSs) could influence such changes in stressed rats. Furthermore, we investigated whether ECSs per se could influence neuronal branching and total length of the CA3 hippocampal neuronal dendritic tree in normal rats. Rats were stressed using the 21-day 6 h daily restraint stress paradigm. The study shows that stress caused remodelling of the pyramidal neurons by significantly reducing the number of dendritic branch points and total length of the apical dendritic tree. Concomitant administration of ECSs prevented these effects. ECSs had no effect on pyramidal neuron dendrites in normal rats.     

A neuronal model of vowel normalization and representation

A speculative neuronal model for vowel normalization and representation is offered. The neurophysiological basis for the premise is the "combination-sensitive" neuron recently documented in the auditory cortex of the mustached bat (N. Suga, W. E. O'Neill, K. Kujirai, and T. Manabe, 1983, Journal of Neurophysiology, 49, 1573-1627). These neurons are specialized to respond to either precise frequency, amplitude, or time differentials between specific harmonic components of the pulse-echo pair comprising the biosonar signal of the bat. Such multiple frequency comparisons lie at the heart of human vowel perception and categorization. A representative vowel normalization algorithm is used to illustrate the operational principles of the neuronal model in accomplishing both normalization and categorization in early infancy. The neurological precursors to a phonemic vocalic system is described based on the neurobiological events characterizing regressive neurogenesis.