Martti Penttonen

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Fast spiking interneurons in the CA1 area of the dorsal hippocampus were recorded from and filled with biocytin in anesthetized rats. The full extent of their dendrites and axonal arborizations as well as their calcium binding protein content were examined. Based on the spatial extent of axon collaterals, local circuit cells (basket and O-LM neurons) and(More)
The following two computational problems are studied: Duplicate grouping: Assume that n items are given, each of which is labeled by an integer key from the set {0, . . . , U − 1}. Store the items in an array of size n such that items with the same key occupy a contiguous segment of the array. Closest pair: Assume that a multiset of n points in the(More)
Gamma frequency field oscillations reflect synchronized synaptic potentials in neuronal populations within the approximately 10-40 ms range. The generation of gamma activity in the hippocampus was investigated by intracellular recording from principal cells and basket cells in urethane anaesthetized rats. The recorded neurones were verified by intracellular(More)
The invasion of sodium spikes from the soma into dendrites was studied in hippocampal pyramidal cells by simultaneous extracellular and intracellular recordings in anesthetized rats and by simultaneous extracellular recordings of the somatic and dendritic potentials in freely behaving animals. During complex-spike patterns, recorded in the immobile or(More)
The cellular-synaptic generation of rhythmic slow activity (RSA or theta) in the hippocampus has been investigated by intracellular recording from principal cells and basket cells in anesthetized rats. In addition, the voltage-, coherence-, and phase versus depth profiles were examined by simultaneously recording field activity at 16 sites in the intact(More)
Interneurons in the dentate area were characterized physiologically and filled with biocytin in urethane-anaesthetized rats. On the basis of axonal targets the following groups could be distinguished. (i) Large multipolar interneurons with spiny dendrites in the deep hilar region densely innervated the outer molecular layer and contacted both granule cells(More)
Dendritic morphology and passive cable properties determine many aspects of synaptic integration in complex neurons, together with voltage-dependent membrane conductances. We investigated dendritic properties of CA1 pyramidal neurons intracellularly labeled during in vivo and in vitro physiologic recordings, by using similar intracellular staining and(More)
The contribution of the various hippocampal regions to the maintenance of epileptic activity, induced by stimulation of the perforant path or commissural system, was examined in the awake rat. Combination of multiple-site recordings with silicon probes, current source density analysis and unit recordings allowed for a high spatial resolution of the field(More)
Intermittently occurring field events, dentate spikes (DS), and sharp waves (SPW) in the hippocampus reflect population synchrony of principal cells and interneurons along the entorhinal cortex-hippocampus axis. We have investigated the cellular-synaptic generation of DSs and SPWs by intracellular recording from granule cells, pyramidal cells, and(More)
The organization of the hippocampus is generally thought of as a series of cell groups that form a unidirectionally excited chain, regulated by localized inhibitory circuits. With the use of in vivo intracellular labeling, histochemical, and extracellular tracing methods, a longitudinally widespread, inhibitory feedback in rat brain from the CA1 area to the(More)