Electrophysiological correlates of prior training: an in vitro study of an area of the avian brain which is essential for early learning

Learning and memory: traditional and systems approaches

The aims of the present work were to consider the characteristics of learning and memory from the point of view of a systems approach and to compare this view with the traditional approach. Neuron activity is regarded not as a response to the synaptic influx resulting in excitation but as a means of altering the cell's relationship with its environment, whose "action" is to eliminate discordance between the cell's "needs" and its microenvironment. The neuronal mechanisms of learning and consolidation of memory are regarded not as formation of a stable increase in the efficiency of synaptic transmission in circuits of connected neurons, but as a system genesis event which confers new system specializations on neurons which do not have to be directly connected synaptically. The roles of the processes of selection, reconsolidatory modification of previously formed memories, gene activation, neurogenesis, and apoptosis in systems genesis occurring both in normal and pathological conditions are discussed. Individual development is regarded as a sequence of system genesis events. The systems approach is applied to the phenomenon of long-term potentiation. In conclusion, a scheme including different types and stages of memory formation is presented.

Emotion and consciousness: Ends of a continuum

We suggest a united concept of consciousness and emotion, based on the systemic cognitive neuroscience perspective regarding organisms as active and goal-directed. We criticize the idea that consciousness and emotion are psychological phenomena having quite different neurophysiological mechanisms. We argue that both characterize a unified systemic organization of behavior, but at different levels. All systems act to achieve intended behavioral results in interaction with their environment. Differentiation of this interaction increases during individual development. Any behavioral act is a simultaneous realization of systems ranking from the least to the most differentiated. We argue that consciousness and emotion are dynamic systemic characteristics that are prominent at the most and least differentiated systemic levels, correspondingly. These levels are created during development. Our theory is based on both theoretical and empirical research and provides a solid framework for experimental work.

Post-synaptic GABAB receptors—possible controllers of coincidence detection?

Post-synaptic GABA(B) responses (slow, late hyperpolarisations which can be eliminated by perfusion with phaclofen) can be recorded in vitro from many, but not all, neurones in the intermediate medial hyperstriatum ventrale (IMHV). The IMHV is an area of the chick forebrain which is remarkable for its plasticity, and for its essential role in two specific types of early learning-imprinting, and a form of one-trial passive-avoidance learning. Post-synaptic GABA(B) responses are strongly statistically associated with other properties (such as high membrane resistance) which are, themselves, dependent on a bird's past history. There is also evidence that their incidence changes with prior training in vivo and with age. GABA(B) hyperpolarisations are always offset to a varying extent by excitatory NMDA components. These two components follow a very similar time-course, so that the duration and (to a lesser extent), the magnitude of a response is controlled by the balance between the two systems. The evidence suggests that this balance fluctuates, and that its fluctuations determine the extent to which any neurone can function as a coincidence detector.

Low-threshold N-methyl-D-aspartate receptor function correlates negatively with learning

The intermediate, medial hyperstriatum ventrale (IMHV) is an area of the forebrain of the domestic chick which exhibits great plasticity. Moreover, there is a strong link between plasticity in the IMHV and specific changes in behaviour. The IMHV in vitro is still plastic, and many of its physiological properties are age-dependent, peaking in slices taken from 3- or 4-day-old birds. This 'window' coincides with an important transitional period in a chick's normal behavioural development. It has also been claimed that reversal training is at its most effective in 3- and 4-day-old birds - a proposition which was confirmed by the experiments reported here. A combination of in vivo training followed by in vitro electrophysiology also revealed that the function of low-threshold N-methyl-D-aspartate receptors (one of the age-related variables) is negatively related to the effectiveness of reversal training, when age is held constant.

Distinct mechanisms for expression of Fos-like immunoreactivity and synaptic potentiation in telencephalic hyperstriatum of the quail chick

In the intermediate and medial hyperstriatum ventrale (IMHV), a telencephalic region essentially involved in the initial processes of early learning tasks in poultry chicks, induction of an immediate early gene c-fos correlates significantly with the degree of learning (K.V. Anokhin, R. Mileusnic, I.Y. Shamakina, S.P.R. Rose, Effects of early experience on c-fos gene expression in the chick forebrain, Brain Res. 544 (1991) 101-107; B.J. McCabe, G. Horn, Learning-related changes in Fos-like immunoreactivity in the chick forebrain after imprinting, Proc. Natl. Acad. Sci. USA 91 (1994) 11417-11421). In slices of IMHV in vitro, on the other hand, tetanic stimulation at a low frequency induces a potentiation of synaptic responses (P.M. Bradley, B.D. Burns, A.C. Webb, Potentiation of synaptic responses in slices from the chick forebrain, Proc. R. Soc. Lond. B. 243 (1991) 19-24; T. Matsushima, K. Aoki, Potentiation and depotentiation of DNQX-sensitive fast excitatory synaptic transmission in telencephalon of the quail chick, Neurosci. Lett. 185 (1995) 179-182). In this study, we have examined a possible causal link between these two forms of activity-dependent processes, c-fos expression and synaptic potentiation. C-fos was visualized immunohistochemically using antibody raised against the Fos-protein, and potentiation was evaluated on the basis of field potential responses to local electrical stimulation. Tetanic stimulation (5 Hz x 300 pulses) was required for potentiation, but not for c-fos expression. Conversely, a negative correlation appeared between them, and slices with relatively high density of Fos-like immunoreactive cells around the stimulation site failed to show potentiation. Furthermore, drugs similarly effective in blocking potentiation (such as AP5 (NMDA receptor antagonist) and bicuculline (GABA(A) receptor antagonist)) had different effects on the c-fos induction. While AP5 had minor, if any, effects on c-fos expression, bicuculline enhanced it selectively around the site of stimulation. Our results suggest that these two processes are basically distinct, and could represent different aspects in the formation of memory traces in IMHV.

Formation and realization of individual experience

This article describes the methodological approach of systemic psychophysiology. In the framework of this approach a wide range of experimental data is analyzed: results of neuronal recordings in vitro and in awake normal and pathological animals learning to perform and performing both complex instrumental and simple behavioral acts. Another block of analyzed data is based on experiments with human subjects who learn and perform the tasks of categorization of words and operator tasks, participate in group game activity, and answer the questionnaires of psychodiagnostic methods. As a result of this analysis, the systemic psychophysiology approach is used to describe qualitatively and quantitatively the formation and realization of individual experience.