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

Abstract

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.

Thalamic filtering of retinal spike trains by postsynaptic summation

“…Stimuli that invade the receptive field surround would involve antagonistic inputs from additional retinal afferents, and likely a more significant role for signals from thalamus and cortex (Wang et al, 2006). Indeed, numerous behavioral and physiological variables can affect LGN integration and transmission of retinal inputs (Mukherjee & Kaplan, 1995), including anesthesia (Li, Funke, Worgotter, & Eysel, 1999), wakefulness (Weyand, Boudreaux, & Guido, 2001), alertness (Cano, Bezdudnaya, Swadlow, & Alonso, 2006), attention (O'Connor, Fukui, Pinsk, & Kastner, 2002), and binocular rivalry (Haynes, Deichmann, & Rees, 2005;Wunderlich, Schneider, & Kastner, 2005). We suggest that our model provides a foundation upon which to describe and to understand the effects of these numerous factors, thus helping to clarify their underlying biophysical mechanisms and computational roles.…”

Noise‐improved signal detection in cat primary visual cortex via a well‐balanced stochastic resonance‐like procedure

“…These 24 different stimulus situations were presented in an interleaved manner to minimize effects related to response variability, e.g. changes in EEG state (Li et al. , 1999).…”

“…These 24 different stimulus situations were presented in an interleaved manner to minimize effects related to response variability, e.g. changes in EEG state (Li et al, 1999). For reasons of better distinction from other possible noise sources, we will call the spatial noise (jitter) 'stimulus tremor' throughout the article.…”

Thalamocortical dynamics of sleep: Roles of purinergic neuromodulation

“…Neocortical evolution has been matched by evolution and expansion of thalamic projections [29, 30]. While thalamocortical projections are classically thought to relay information to the neocortex, recent evidence suggests that thalamocortical neuronal firing impacts neocortical states [31, 32]. Depending on their initial resting membrane potential, thalamocortical (TC) neurons are able to either reliably transmit spike trains or initiate oscillatory burst firing in response to the incoming synaptic drive [33].…”