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In cats with pretrigeminal brainstem transections, reversible inactivation of the primary visual cortex by cooling results in changes of the magnitude of response and spatio-temporal structure of receptive fi elds of neurons from lateral geniculate and perigeniculate nuclei (LGNd and PGN; Waleszczyk et al. 2005). Since cortical inactivation changes also the spontaneous activity of these thalamic neurons, we hypothesized that cortical feedback affects their membrane potential. Both types of investigated cells displayed two modes of activity: a tonic mode, during depolarization; and a burst mode, when the cell is hyperpolarized. In this report we investigated the effect of elimination of cortical feedback by cooling on the temporal pattern of the spontaneous "bursty" activity of single neurons in LGNd and PGN. During such reversible inactivation of areas 17 and 18, in both LGNd and PGN cells, spontaneously occurring bursts exhibited longer interspike intervals (ISIs) and lower number of spikes, while the average burst duration remained unchanged. Longer ISIs suggest that cortical feedback infl uences not only visual responsiveness of thalamic neurons, but also temporal pattern of their spontaneous fi ring, in line with the hypothesis of a tonic cortical modulation of their membrane potential. Supported by the Ministry of Science and Higher Education grant COST/127/2007.
Jerzy Konorski was one of the most eminent world leaders in research on brain physiology, the author of instrumental (Type II) conditioned refl ex theory and the founder of the Polish school of neurophysiology. Already as a student of medicine, Konorski discerned experimentally a new type of conditioned refl exes, which he called motor (Type II) as opposed to classic (Type I) salivary refl exes, studied by I.P. Pavlov. In 1928 he described, for the fi rst time, the specifi city of Type II refl exes and the methods of their training. In 1931–1933 he stayed in Pavlov’s famous laboratory in Petersburg. Since 1933 he was associated with the Nencki Institute of Experimental Biology, where after World War II, he created and became the Head of the Department of Neurophysiology, the research of which was devoted to the analysis of mechanisms controlling voluntary motor behavior. Konorski published more than 180 papers, among them three monographs, concerning principles of brain functioning. His passion for research, creativity and profound knowledge attracted many scientists from around the world who visited him and his Department. In recognition of his scientifi c achievements Konorski’s name was put on a strict list of candidates for Nobel Price. His death in 1973 was a great loss for both the Polish and world scientifi c community. His ideas are still appreciated and continue to inspire further research with the use of modern techniques.
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