The reflection of the operations of comparing afferent flow with internal pretuning in the neuronal impulse activity of the frontal cortex in the dog

From 192 neurons, recorded in the frontal cortex of dogs trained for differential classical conditioning of salivary reflex, 24 cells were identified related to the detection of matching-mismatching conditioned and unconditioned stimuli (CS and US) to internal set. Impulse reactions of the 1-st group of neurones (11 cells) to US disappeared, when any deviation from standard pattern of CS-US pairing occurred or when US characteristics were suddenly changed. These reactions developed again at the 3-5th repeated presentation of the stimuli delivered in "new" regime. Neurones of the 2-nd group (13 cells) were activated in response to CS only when two sequential CSs had different meaning. The 1-st group of neurones is considered as detectors of matching, and the 2-nd group--as detectors of mismatching the stimulus to its neural model, formed by mechanism of reinforcement.     

Changes produced in neuronal excitability by subthreshold depolarization as a possible mechanism of interval selective relationships within the central nervous system

A neuronal process was identified inLymnaea stagnalis nerve cells which may be viewed as one of the mechanisms underlying the interval selectivity previously described in research into the functional relationships between mammalian brain cells. This process takes the form of regularly-occurring changes in excitability resulting in a high probability (of 0.6–1) of neuronal spike response to what had previously been subthreshold depolarizing current pulses following similar subthreshold (conditioning) pulses at intervals specific to each individual neuron. It was found that the cycle of change in neuronal excitability following threshold depolarization did not arise from temporal summation of electrotonic local or postsynaptic neuronal potentials; it was an endogenous (cytoplasmic) process insensitive to transmitter (acetylcholine) application but altering irreversibly under the effects of bombesin, one of the modulator peptides.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad; Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologya, Vol. 21, No. 3, pp. 291–299, May–June, 1989.     

Participation of frontal lobe neurons in the organization of successive inhibition and disinhibition of conditioned reflexes in the dog

Neuronal activity in g. proreus was studied during classical secretory conditioning and its differentiation in dogs. Three types of changes in neuronal reaction pattern were identified during differential conditioned stimulus compared to the pattern observed during positive conditioned stimulus. It has been shown that signal significance of the conditioned stimulus may be coded by specific distribution of interspike intervals in response to different conditioned stimuli. In situation of successive inhibition or disinhibition of the differentiation some neurones displayed simultaneous appearance of interspike intervals specific for responses to current and previously presented conditioned stimuli.     

Studies on projections of somatic afferentation in the neocortex of the hedgehog Erinaceus europaeus]

Cortical projections of the somatic system in the hedgehog cortex were studied by means of the evoked potential (EP) technique. The EPs were shown to arise at a large area of the lateral cortex, the area in question being enlarged under chloralose anaesthesia. In the focus of projection of corresponding modalities the EPs posessed the least latency. Functional differences in the EP generation system both in the focus of projection and outside it are discussed. The wide EPs spreading in the lateral cortex as well as the presence of relatively differentiated projections is supposed to depend on the afferent volley dispersion to the polysynaptic pathways at the thalamic level. Considerable overlapping of sensory projection zones in the cortex is conditioned by the latter and indicates low degree of the somatic analyser organization.     

Mitochondria as a target for neuroprotection

Despite all the efforts of modern medical and biomedical sciences, the effective therapeutic treatments that would restore the brain functions lost after stroke have not been found yet. At the same time, experimental preclinical studies revealed an arsenal of effectors having potential for clinical applications. Identification of the key signaling pathways, both damaging and protective, can accelerate the development and implementation of new effective neuroprotectors. One of the key elements of these pathways is mitochondrion. In this context, we studied various therapeutic approaches to the treatment and prevention of cerebral ischemia, which are aimed at modulation of mitochondrial functions. The spectrum of tested neuroprotectors included antioxidants, uncouplers of respiration and phosphorylation, as well as ischemic, remote, and pharmacological preconditioning. Their efficacy and therapeutic windows were compared and the possibility of combining different methods in order to maximize their efficiency was considered.