The Role of the Electrophysiological Properties of Neurons in the Mechanisms Grouping Their Discharges in the Cerebral Cortex

Neuroscience and Behavioral Physiology, Vol. 34, No. 9, 2004The Role of the Electrophysiological Properties of Neurons

in the Mechanisms Grouping Their Discharges in the

Cerebral CortexN. N. Karpuk and V. V. Vorobev UDC 612.822.3+612.825.1Translated from Zhurnal Vysshei Nervnoi Deyatelnosti, Vol. 53, No. 5, pp. 595603, OctoberNovember,

2003. Original article submitted April 4, 2002, accepted November 28, 2002.Studies using intracellular recording in living slices of rat sensorimotor cortex addressed the interaction

between the properties of neuron spike activity (n = 80) and the membrane potentials of the neurons. Spike

sequences containing discharges with regularly increasing and decreasing interspike intervals were analyzed. Parameters were identified which were closely associated with the mean neuron discharge frequency: the number of spikes in sequences (530% of the total number of spikes recorded), the amplitude

of oscillations in the afterhyperpolarization potential (01.5 mV), etc. There was a biphasic relationship

in changes in the number of spikes in sequences with a critical mean discharge frequency over the range

57 Hz. Groups of cells without and with a depolarization component in conditions of afterhyperpolarization had different morphological and electrophysiological properties, though the relationships between

their parameter and mean discharge frequency were similar. The possible roles of spike sequences and

these regular features in the formation of rhythmic processes in the neocortex are discussed.KEY WORDS: neuron spike activity and adaptation, spike sequences, membrane potential, intracellular recording,

theta rhythm, neocortex.One of the most dynamic parameters, closely associated with information processes in the brain, is the spike activity of neurons, where the discharge frequencies reflect the

level of neuron excitation. In brain associative activity, spike

frequency increases, resulting in increases in the rhythmicity of discharges and discharge grouping over the frequency

range 25 Hz [1, p. 317]. However, it has been noted that the

mechanisms forming rhythmicity have different characteristics in different brain areas [7], which is evidenced particularly by the specific formation of local neural networks.

Insufficient attention has been paid to the role of the properties of the neurons themselves in these processes, though

without this factor it is difficult to explain how brain structures generate rhythms of the same frequency in different

types of afferent signals. Thus, in particular, theta rhythms,

which are widespread in the brain, arise in the corresponding structures in...