Mass correlograms of multiple neuronal activity in the cat's extrastriate cortex

Journal of Neurophysiology

1992

177

163

1. The discharge of individual neurons in the visual cortex and lateral geniculate nucleus (LGN) of anesthetized and paralyzed cats and kittens was examined for the presence of oscillatory activity. Neural firing was evoked through the monoptic or dichoptic presentation of drifting gratings and random sequences of flashed bars. The degree to which different oscillatory frequencies were present in neural discharge was quantified by computation of the power spectra of impulse train responses. 2. Action potentials from single cells were recorded extracellularly and isolated on the basis of amplitude. Receptive-field properties of the neurons under study were characterized initially by their discharge in response to gratings of sinusoidal luminance. By varying orientation and spatial frequency, optimal stimulus characteristics were determined. Oscillation analysis was performed on spike trains acquired during repeated presentations of the optimal stimulus by identification of power spectra peaks in the frequency range of rhythmic potentials observed in electroencephalograph studies (30-80 Hz). The amplitude and frequency of the largest peak in this range was used to characterize oscillatory strength and frequency. All discharge in which the peak amplitude exceeded the high-frequency noise by a factor > 1.5 was classified as oscillatory. 3. Of the 342 cortical cells examined, 147 cells displayed oscillatory activity in the 30 to 80-Hz range during portions of their visual response. Sixty out of 169 simple cells, 82 out of 166 complex cells, and 5 out of 7 special complex cells exhibited oscillations. There was no laminar bias in the distribution of oscillatory cells; the proportions of oscillatory cells were similar in all layers. All oscillatory discharge was variable with respect to frequency and strength between successive presentations of the same optimal stimulus. In as little as 10 s, for example, peak frequencies shifted by a factor of two. For many cells, these trial-to-trial variations obscured detectable oscillations when all trials were averaged together. 4. The potential role of neuronal maturation in the generation of oscillatory activity was investigated by studying neuronal responses from kittens at 4 wk postnatal. Of the 80 kitten cells studied, 27 exhibited oscillatory discharge. Although oscillations in the kitten visual cortex spanned the same frequency range as that seen in the adult, oscillations in the midfrequency range (36-44 Hz) are more common in the adult cortex. 5. To explore the possibility that oscillations might play a functional role in vision, we investigated the dependence of oscillations on different stimulus parameters.(ABSTRACT TRUNCATED AT 400 WORDS)

Section: Oscillation Frequenciesmentioning

confidence: 96%

Oscillatory discharge in the visual system: does it have a functional role?

Journal of Neurophysiology

1992

177

163

“…7 were seen from 6 to 9. Local field potentials can reflect synaptic activity in addition to Single unit discharge (Reinis et al, 1988). Consistent behavior was obtained when t 0 was varied between 15 and 25 ms. Below 15 ms, oscillations were weak and had frequencies higher than 30 Hz.…”

Section: V(t) = V(t)mentioning

confidence: 59%

“…30-Hz oscillations have not been reported in local field potential recordings (Engel et al, 1990). Local field potentials can reflect synaptic activity in addition to Single unit discharge (Reinis et al, 1988). Given the lack of low-frequency oscillatory EPSPs (Jagadeesh et al, 1992), oscillatory synaptic activity might predominantly reflect the higher frequency oscillations associated with the LGN.…”

Section: V(t)mentioning

confidence: 99%

Intracortical connections are not required for oscillatory activity in the visual cortex

1997

Vis Neurosci

Synchronized oscillatory discharge in the visual cortex has been proposed to underlie the linking of retinotopically disparate features into perceptually coherent objects. These proposals have largely relied on the premise that the oscillations arise from intracortical circuitry. However, strong oscillations within both the retina and the lateral geniculate nucleus (LGN) have been reported recently. To evaluate the possibility that cortical oscillations arise from peripheral pathways, we have developed two plausible modeis of Single cell oscillatory discharge that specifically exclude intracortical networks. In the first model, cortical oscillatory discharge near 50 Hz in frequency arises from the integration of Signals from strongly oscillatory cells within the LGN. The model also predicts the incidence of 50-Hz oscillatory cells within the cortex. Oscillatory discharge around 30 Hz is explained in a second model by the presence of intrinsically oscillatory cells within cortical layer 5. Both modeis generate spike trains whose power spectra and mean firing rates are in close agreement with experimental observations of simple and complex cells. Considered together, the two modeis can largely account for the nature and incidence of oscillatory discharge in the cat's visual cortex. The validity of these modeis is consistent with the possibility that oscillations are generated independently of intracortical interactions. Because these modeis rely on intrinsic stimulus-independent oscillators within the retina and cortex, the results further suggest that oscillatory activity within the cortex is not necessarily associated with the processing of high-order visual information.

“…Thirty Hz oscillations have not been reported in local field potential recordings (Engel et al, 1990). Local field potentials can reflect synaptic activity in addition to single unit discharge (Reinis et al, 1988). Given the lack of low frequency oscillatory EPSPs (Jagadeesh et al 1992), oscillatory synaptic activity might predominantly reflect the higher frequency oscillations associated with the…”

Section: Model 2: Intrinsic Oscillatorsmentioning

confidence: 99%

Intracortical connections are not required for oscillatory activity in the visual cortex

1997

Vis Neurosci

Synchronized oscillatory discharge in the visual cortex has been proposed to underlie the linking of retinotopically disparate features into perceptually coherent objects. These proposals have largely relied on the premise that the oscillations arise from intracortical circuitry. However, strong oscillations within both the retina and the lateral geniculate nucleus (LGN) have been reported recently. To evaluate the possibility that cortical oscillations arise from peripheral pathways, we have developed two plausible models of single cell oscillatory discharge that specifically exclude intracortical networks. In the first model, cortical oscillatory discharge near 50 Hz in frequency arises from the integration of signals from strongly oscillatory cells within the LGN. The model also predicts the incidence of 50-Hz oscillatory cells within the cortex. Oscillatory discharge around 30 Hz is explained in a second model by the presence of intrinsically oscillatory cells within cortical layer 5. Both models generate spike trains whose power spectra and mean firing rates are in close agreement with experimental observations of simple and complex cells. Considered together, the two models can largely account for the nature and incidence of oscillatory discharge in the cat's visual cortex. The validity of these models is consistent with the possibility that oscillations are generated independently of intracortical interactions. Because these models rely on intrinsic stimulus-independent oscillators within the retina and cortex, the results further suggest that oscillatory activity within the cortex is not necessarily associated with the processing of high-order visual information.