Cortical and Subcortical EEG in Relation to Sleep-Wake Behavior in Mammalian Species

Simultaneous recordings of the EEG and the visual activity of cat dorsal lateral geniculate nucleus (dLGN) relay cells were analysed for covariance. Sliding time‐window analyses were performed in parallel for the EEG power spectrum and single unit visual activity. The EEG power ratio (EEG‐PR) of low (1‐8 Hz) to high (20‐40 Hz) frequencies was chosen to achieve a quantitative measure of the EEG which could be compared with the spike rate of a dLGN unit at any time. A high EEG‐PR value indicates a synchronized EEG dominated by low frequencies (δ waves and sleep spindles), a low value indicates a less synchronized EEG. In the anaesthetized animal, two different underlying patterns of activity in the EEG‐PR were found: slow gradual changes (slow gradations) and oscillatory changes. In many cases both were accompanied by correlated variations in dLGN spike rate, either for overall activity or for burst firing. The slow gradations appear for long time periods of up to 200 s and, in most cases (76·3 %), show a negative correlation between EEG‐PR and overall spike rate, but predominantly a positive correlation for burst firing (85·1 %). The oscillatory changes, which have not previously been reported, appear as temporally well‐coupled variations in EEG‐PR and spike rate with a stable cycle length within the range 4‐10 s. In about 77 % of correlated changes the temporal delay between the change in EEG‐PR and that of the spike rate was less than ± 1·0 s. During simultaneous recordings from two dLGN cells the variations in spike rate tend to show the same sign of correlation with respect to the EEG pattern. This relationship is more pronounced with the slow gradations than with the oscillatory changes. Slow gradations in the spectral composition of the EEG may indicate global transitions between different stages within the sleep‐wake cycle, reflecting the well‐known influences of the brainstem arousal system. The oscillations in the spectral composition of the EEG are accompanied by gradual variations in thalamic transmission mode and are more likely to be due to involvement of a local feedback system via the thalamo‐cortico‐thalamic loop. The difference between the effects on overall and burst firing activity supports the notion that phasic (burst firing) and tonic visual responses may play distinctive roles in information processing, which are functionally related to the animal's behavioural state.

Section: Resultssupporting

confidence: 84%

Section: Discussionmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Correlated variations in EEG pattern and visual responsiveness of cat lateral geniculate relay cells

Funke

Wörgötter

et al. 1999

“…The reason for this may be related to spontaneous changes in EEG. Even during halothane/nitrous oxide anaesthesia, the endogenous sleep–wake rhythm of the cat goes on, leading to spontaneous transitions between high and low delta states about every 30 min (Lancel, 1993) which are not under the control of the experimenter. Thus, the likelihood that an internal state change happens at the same time as a change induced by rTMS is statistically lower for short (1 or 5 min) than for long (20 min) rTMS applications.…”

Section: Discussionmentioning

confidence: 99%

Effects of repetitive TMS on visually evoked potentials and EEG in the anaesthetized cat: dependence on stimulus frequency and train duration

Aydın-Abidin¹,

Moliadze²,

Eysel³

et al. 2006

Repetitive transcranial magnetic stimulation (rTMS) has been shown to alter cortical excitability that lasts beyond the duration of rTMS application itself. High-frequency rTMS leads primarily to facilitation, whereas low-frequency rTMS leads to inhibition of the treated cortex. However, the contribution of rTMS train duration is less clear. In this study, we investigated the effects of nine different rTMS protocols, including low and high frequencies, as well as short and long applications (1, 3 and 10 Hz applied for 1, 5 and 20 min), on visual cortex excitability in anaesthetized and paralysed cats by means of visual evoked potential (VEP) and electroencephalography (EEG) recordings. Our results show that 10 Hz rTMS applied for 1 and 5 min significantly enhanced early VEP amplitudes, while 1 and 3 Hz rTMS applied for 5 and 20 min significantly reduced them. No significant changes were found after 1 and 3 Hz rTMS applied for only 1 min, and 10 Hz rTMS applied for 20 min. EEG activity was only transiently (<20 s) affected, with increased delta activity after 1 and 3 Hz rTMS applied for 1 or 5 min. These findings indicate that the effects of rTMS on cortical excitability depend on the combination of stimulus frequency and duration (or total number of stimuli): short high-frequency trains seem to be more effective than longer trains, and low-frequency rTMS requires longer applications. Changes in the spectral composition of the EEG were not correlated to changes in VEP size. Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive and largely painless technique to stimulate the human brain. It is preferentially applied to cortical areas with the intention to either disturb ongoing processing in the targeted area (virtual lesion) or to modulate the general excitability of the cortical network. Besides transient effects, numerous studies have shown that rTMS has modulatory effects on cortical excitability that last for seconds to many minutes beyond the duration of the rTMS application itself. The primary motor cortex has been used extensively for rTMS studies because the effects of stimulation are easy to quantify by measuring the size of motor-evoked potentials (MEPs). Findings to date suggest that the modulatory effects of rTMS on cortical excitability may be inhibitory or facilitatory depending on the frequency, intensity and duration of the stimulus (see Modugno et al. 2001). A few examples: high-frequency rTMS, especially at high stimulus intensities, leads to facilitation of corticospinal activity; a 10-pulse rTMS train of 20 Hz applied at a strength of 150% resting motor threshold (RMT) caused an increase in MEP size lasting for about 3 min (Pascual-Leone et al. 1994); a 30-pulse rTMS train at 120% RMT and 15 Hz caused a shorter and smaller increase in MEP size for only 90 s (Wu et al. 2000). Stimulation intensities below RMT usually require longer trains before any lasting effect is seen. Maeda et al. (2000a,b) reported a facilitation of MEPs for 2 min after administration of 240 pulses of 20 ...

“…Nevertheless, some fluctuations of response strength and spectral composition of the EEG are always present (Li et al 1999). Complete recording sessions including control measurements, drug applications with different ejection currents and interleaved recoveries, all tested for different stimulus features, lasted for several hours and could be accompanied by spontaneous changes in the EEG pattern that followed the natural sleep‐wake cycle of the cat (Lancel, 1993). Discarding those records with too dissimilar EEG patterns considerably further reduced the sample of usable data.…”

Section: Resultsmentioning

confidence: 99%

D₁ and D₂ receptor‐mediated dopaminergic modulation of visual responses in cat dorsal lateral geniculate nucleus

Zhao

Kerscher

Eysel

et al. 2002

The mean tonic activity of five X-and five Y-cells is plotted over time after onset of QUIN application with 10-20 nA. The curves were slightly smoothed by calculating sliding means from three successive responses. The responses were normalized to the mean of the three first response levels, which were set to 0 on the graph. Continuous lines show Y-cell activity, dashed lines that for the X-cells. The grey lines show overall means for X-and Y-cells. Regression lines have also been added.