Variability of cortical evoked responses in man related to slow wave activity

Pfurtscheller, Gert

doi:10.1007/bf00583647

Cited by 2 publications

(2 citation statements)

References 9 publications

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“…Especially pertinent to the present study, it has been shown that evoked potentials can be modulated by the phase of an ongoing rhythm during which they are presented [for review and alternative viewpoint see Rudell (1980)]. For example, Pfurtscheller (1976) found that an ongoing slow oscillation rhythmically modulated the amplitude of N90 waves recorded from awake subjects.…”

Section: Variability and State-dependent Modulation Of Evoked Responsesmentioning

confidence: 81%

Trial-to-Trial Variability and State-Dependent Modulation of Auditory-Evoked Responses in Cortex

1999

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Recent experimental work has provided evidence that trial-to-trial variability of sensory-evoked responses in cortex can be explained as a linear superposition of random ongoing background activity and a stationary response. While studying single trial variability and state-dependent modulation of evoked responses in auditory cortex of ketamine/xylazine-anesthetized rats, we have observed an apparent violation of this model. Local field potential and unit spike trains were recorded and analyzed during different anesthesia depths-deep, medium, and light-which were defined by the pattern of ongoing cortical activity. Estimation of single trial evoked response was achieved by considering whole waveforms, rather than just one or two peak values from each wave. Principal components analysis was used to quantitatively classify waveforms on the basis of their time courses (i.e., shapes). We found that not only average response but also response variability is modulated by depth of anesthesia. Trial-to-trial variability is highest under medium levels of anesthesia, during which ongoing cortical activity exhibits rhythmic population bursting activity. By triggering the occurrence of stimuli from the spontaneously occurring burst events, we show that the observed variability can be accounted for by the background activity. In particular, the ongoing activity was found to modulate both amplitude and shape (including latency) of evoked local field potentials and evoked unit activity in a manner not predicted by linear superposition of background activity and a stereotyped evoked response. This breakdown of the linear model is likely attributable to rapid transitions between different levels of thalamocortical excitability (e.g., spike-wave discharges), although brain "state" is relatively fixed.

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Section: Variability and State-dependent Modulation Of Evoked Responsesmentioning

confidence: 81%

Trial-to-Trial Variability and State-Dependent Modulation of Auditory-Evoked Responses in Cortex

1999

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“…Our findings bridge the gap between 2 emerging themes in systems neuroscience. On one hand, studies in a variety of disciplines including optical imaging, single-unit recording, and field potential/EEG recording have dramatically underscored the effects of ambient activity on sensory processing (Pfurtscheller 1976;Basar 1993a, 1993b;Steriade et al 1993;Arieli et al 1996;Contreras et al 1996;Polich 1997;Kisley and Gerstein 1999;Sanches-Vives and McCormick 2000;Truccolo et al 2002;Kruglikov and Schiff 2003;Fiser et al 2004;Lakatos et al 2005).…”

Section: Discussionmentioning

confidence: 99%

Transient Cortical Excitation at the Onset of Visual Fixation

et al. 2007

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Primates actively examine the visual world by rapidly shifting gaze (fixation) over the elements in a scene. Despite this fact, we typically study vision by presenting stimuli with gaze held constant. To better understand the dynamics of natural vision, we examined how the onset of visual fixation affects ongoing neuronal activity in the absence of visual stimulation. We used multiunit activity and current source density measurements to index neuronal firing patterns and underlying synaptic processes in macaque V1. Initial averaging of neural activity synchronized to the onset of fixation suggested that a brief period of cortical excitation follows each fixation. Subsequent single-trial analyses revealed that 1) neuronal oscillation phase transits from random to a highly organized state just after the fixation onset, 2) this phase concentration is accompanied by increased spectral power in several frequency bands, and 3) visual response amplitude is enhanced at the specific oscillatory phase associated with fixation. We hypothesize that nonvisual inputs are used by the brain to increase cortical excitability at fixation onset, thus "priming" the system for new visual inputs generated at fixation. Despite remaining mechanistic questions, it appears that analysis of fixation-related responses may be useful in studying natural vision.

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Variability of cortical evoked responses in man related to slow wave activity

Cited by 2 publications

References 9 publications

Trial-to-Trial Variability and State-Dependent Modulation of Auditory-Evoked Responses in Cortex

Trial-to-Trial Variability and State-Dependent Modulation of Auditory-Evoked Responses in Cortex

Transient Cortical Excitation at the Onset of Visual Fixation

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