Lateral geniculate nucleus unitary discharge in sleep and waking: state- and rate-specific aspects

Abstract

The relationship between behavioral state, discharge pattern, and discharge rate was investigated in 26 lateral geniculate nucleus (LGN) units recorded in cats in the dark during waking (W), synchronized sleep (S), and desynchronized sleep (D). A distinctive state-dependent discharge pattern was the presence of stereotyped bursts of 2-7 spikes that occurred in 63% of the units. These bursts were most frequent in S, much less frequent in D, and rarely occurred in W. Lack of association with discharge rate changes between states showed the bursting to be a true state-dependent phenomenon. A burst consisted of 2-7 spikes, with each successive interspike interval being longer than the preceding one; in the 200 ms prior to burst occurrence, discharge probability decreased markedly. This structure of burst organization suggested a model of generation wherein each burst was caused by a unitary event of varying intensity, perhaps a rebound following a hyperpolarization. Spectral and autocorrelational analyses showed bursts occurred rhythmically in three cells at a frequency of 3-4 Hz and in two cells at a frequency of 10-12 Hz, indicating a possible linkage with slow-wave generators. While the number of bursts in the various behavioral states was a state-dependent phenomena, other aspects of discharge pattern were shown to be rate dependent. To evaluate discharge pattern apart from the occurrence of bursts, a "primary event spike train" was formed; this consisted of individual spikes and the first spike of each burst. This analysis showed that, within S, the probability of burst occurrence was highest when the primary spike rate was low. Quantitative analyses showed that first-order pattern measures (the form of the interspike interval histogram, IH) were dependent on the mean interspike interval (ISI, the inverse of mean rate). This association explained 83-89% of the variance in a power series approximation of IH form. Joint interval histograms (JIH) were used to evaluate the signature of bursts and of the form of the primary spike train. As with interval histograms, the main features of the form of the primary spike JIH were dependent on the primary spike rate. Thus, we concluded that first- and second-order discharge patterns of primary events were rate dependent and not state dependent. Our data are compatible with a model where in the absence of retinal input, the frequency of LGN primary spikes over behavioral state changes is largely determined by brain stem reticular formation input.(ABSTRACT TRUNCATED AT 400 WORDS)

Visual Response Properties in the Dorsal Lateral Geniculate Nucleus of Mice Lacking the β2 Subunit of the Nicotinic Acetylcholine Receptor

“…These criteria picked out stereotypical patterns of spike firing and identified burst firing with the same properties as those previously recorded in vitro in other mammals. In particular, burst length depended on the duration of the initial within-burst ISI (McCarley et al, 1983;Radhakrishnan et al, 1999), and intraburst ISIs gradually increased in duration (McCarley et al, 1983;Radhakrishnan et al, 1999;Reinagel et al, 1999) (data not shown).…”

Vigilance, alertness, or sustained attention: physiological basis and measurement

“…These changes alter transmission of signals conveying information from external environment and help generate sleep spindles (Steriade, 1999). During slow wave sleep, the thalamocortical activity consists of synchronous rhythmic activity (EEG delta waves and sleep spindles) associated with burst states in thalamic projection neurons (McCarley et al, 1983). During the awake state there is some sort of cortical activation, presumably related to partial neuronal depolarization bringing neurons closer to firing levels (Steriade, 2000).…”

Excitatory Effects of Thyrotropin-Releasing Hormone in the Thalamus

“…In the awake attentive animal, thalamocortical neurons are relatively depolarized, discharge almost exclusively in the single-spike firing mode, and faithfully transfer inputs from the sensorium. With the transition to slowwave sleep, thalamic neurons hyperpolarize and increasingly replace single-spike discharge with rhythmic burst firing, such as spindle waves (McCarley et al, 1983;Domich et al, 1986;Steriade et al, 1986Steriade et al, , 1993. Spindle waves are observed in the electroencephalogram (EEG) as waxing and waning 6 -15 Hz oscillations (Steriade et al, 1993).…”