Integrated Information Coefficient Estimated from Neuronal Activity in Hippocampus-Amygdala Complex of Rats as a Measure of Learning Success.

BACKGROUND: The goal of the brain is to provide right on time a suitable earlier-acquired model for the future behavior. How a complex structure of neuronal activity underlying a suitable model is selected or fixated is not well understood. Here we propose the integrated information Φ as a possible metric for such complexity of neuronal groups. It quantifies the degree of information integration between different parts of the brain and is lowered when there is a lack of connectivity between different subsets in a system. METHODS: We calculated integrated information coefficient (Φ) for activity of hippocampal and amygdala neurons in rats during acquisition of two tasks: spatial task followed by spatial aversive task. An Autoregressive Φ algorithm was used for time-series spike data. RESULTS: We showed that integrated information coefficient Φ is positively correlated with a metric of learning success (a relative number of rewards). Φ for hippocampal neurons was positively correlated with Φ for amygdalar neurons during the learning requiring the cooperative work of hippocampus and amygdala. CONCLUSIONS: This result suggests that integrated information coefficient Φ may be used as a prediction tool for the suitable level of complexity of neuronal activity and the future success in learning and adaptation and a tool for estimation of interactions between different brain regions during learning.

Neuronal Bases of Systemic Organization of Behavior.

Despite the years of studies in the field of systems neuroscience, functions of neural circuits and behavior-related systems are still not entirely clear. The systems description of brain activity has recently been associated with cognitive concepts, e.g. a cognitive map, reconstructed via place-cell activity analysis and the like, and a cognitive schema, modeled in consolidation research. The issue we find of importance is that a cognitive unit reconstructed in neuroscience research is mainly formulated in terms of environment. In other words, the individual experience is considered as a model or reflection of the outside world and usually lacks a biological meaning, such as describing a given part of the world for the individual. In this chapter, we present the idea of a cognitive component that serves as a model of behavioral interaction with environment, rather than a model of the environment itself. This intangible difference entails the need in substantial revision of several well-known phenomena, including the long-term potentiation.The principal questions developed here are how the cognitive units appear and change upon learning and performance, and how the links between them create the whole structure of individual experience. We argue that a clear distinction between processes that provide the emergence of new components and those underlying the retrieval and/or changes in the existing ones is necessary in learning and memory research. We then describe a view on learning and corresponding neuronal activity analysis that may help set this distinction.

Expression of c-Fos in the rat retrosplenial cortex during instrumental re-learning of appetitive bar-pressing depends on the number of stages of previous training.

Learning is known to be accompanied by induction of c-Fos expression in cortical neurons. However, not all neurons are involved in this process. What the c-Fos expression pattern depends on is still unknown. In the present work we studied whether and to what degree previous animal experience about Task 1 (the first phase of an instrumental learning) influenced neuronal c-Fos expression in the retrosplenial cortex during acquisition of Task 2 (the second phase of an instrumental learning). Animals were progressively shaped across days to bar-press for food at the left side of the experimental chamber (Task 1). This appetitive bar-pressing behavior was shaped by nine stages ("9 stages" group), five stages ("5 stages" group) or one intermediate stage ("1 stage" group). After all animals acquired the first skill and practiced it for five days, the bar and feeder on the left, familiar side of the chamber were inactivated, and the animals were allowed to learn a similar instrumental task at the opposite side of the chamber using another pair of a bar and a feeder (Task 2). The highest number of c-Fos positive neurons was found in the retrosplenial cortex of "1 stage" animals as compared to the other groups. The number of c-Fos positive neurons in "5 stages" group animals was significantly lower than in "1 stage" animals and significantly higher than in "9 stages" animals. The number of c-Fos positive neurons in the cortex of "9 stages" animals was significantly higher than in home caged control animals. At the same time, there were no significant differences between groups in such behavioral variables as the number of entrees into the feeder or bar zones during Task 2 learning. Our results suggest that c-Fos expression in the retrosplenial cortex during Task 2 acquisition was influenced by the previous learning history.