The effect of stimulation rate on the signal-to-noise ratio of evoked responses

Ahlfors, Seppo P.; Ilmoniemi, Risto J.; Portin, K.

doi:10.1016/0168-5597(93)90058-w

Cited by 12 publications

(9 citation statements)

References 12 publications

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“…In contrast to Blankenburg et al (2003), who studied the compound neuronal activity of the stimulus pair because individual responses to prime and test stimuli cannot be disentangled in fMRI due to the long time constant of the BOLD response, we presented stimulus pairs with ISIs ≥150 ms that enabled us to study cortical responses to the individual stimuli without any overlap of cortical activations (Ahlfors et al, 1993).…”

Section: Methodsmentioning

confidence: 99%

Cortical processing of near-threshold tactile stimuli: An MEG study

et al. 2010

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In the present study we tested the applicability of a paired-stimulus paradigm for the investigation of near-threshold (NT) stimulus processing in the somatosensory system using magnetoencephalography. Cortical processing of the NT stimuli was studied indirectly by investigating the impact of NT stimuli on the source activity of succeeding suprathreshold test stimuli. We hypothesized that cortical responses evoked by test stimuli are reduced due to the preactivation of the same finger representation by the preceding NT stimulus. We observed attenuation of the magnetic responses in the secondary somatosensory (SII) cortex, with stronger decreases for perceived than for missed NT stimuli. Our data suggest that processing in the primary somatosensory cortex including recovery lasts for <200 ms. Conversely, the occupancy of SII lasts >/=500 ms, which points to its role in temporal integration and conscious perception of sensory input.

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Section: Methodsmentioning

confidence: 99%

Cortical processing of near-threshold tactile stimuli: An MEG study

et al. 2010

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“…In such a case, the noise should be inversely proportional to the square root of the number of trials [31]. While this is roughly true for the EEG [32], we also need to take into account that some of the noise might depend on the amplitude of the P300 and thus on the stimulus probability.…”

Section: Introductionmentioning

confidence: 98%

Signal and noise in P300 recordings to visual stimuli

Heinrich¹,

Bach²

2008

Doc Ophthalmol

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The P300 of the event-related potential is typically obtained for infrequent target stimuli that are embedded in a sequence of frequent irrelevant stimuli. The P300 has been suggested as a marker of high-level cognitive processing and might be useful in ophthalmology to confirm the diagnosis of a functional disorder. However, typical P300 measurements require relatively lengthy recording sessions. It would therefore be desirable to minimize the required time and to maximize the signal-to-noise ratio by finding the optimal balance between parameters such as stimulus probability and the number of target trials or the recording time. This is different from previous studies, which assessed the amplitude only. We recorded event-related potentials to visual stimuli using standard oddball paradigms with various target frequencies ranging from 2:1 (target majority) to 1:16 (massive non-target majority). We compared the signal-to-noise ratios for a fixed number of target trials as well as for a fixed total recording time and assessed effects of the immediate stimulus history. As expected, P300 amplitudes depend strongly on target infrequency. This did not reach saturation within the range tested. For a given number of target trials, the signal-to-noise ratio also increases with target infrequency. For a given recording duration, the signal-to-noise ratio is optimal around 1:8. In the 1:4 condition, the signal-to-noise ratio can be improved by excluding trials that were preceded by a target trial.

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“…Moreover, we used a 4.3–4.8 s interstimulus interval (ISI) between pulse trains because previous MEG studies have found that: (1) the benefit of longer ISIs falls off exponentially after ∼4.0 s (Ahlfors et al . ; Raij et al . ); (2) studies of somatosensory responses from the secondary cortices have found such responses are strongest when using ISIs around 5.0 s (Wikström et al .…”

Section: Methodsmentioning

confidence: 99%

Oscillatory dynamics and functional connectivity during gating of primary somatosensory responses

Wiesman¹,

Heinrichs‐Graham²,

Coolidge³

et al. 2016

The Journal of Physiology

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Key Pointsr Sensory gating is important for preventing excessive environmental stimulation from overloading neural resources.r Gating in the human somatosensory cortices is a critically understudied topic, particularly in the lower extremities.r We utilize the unique capabilities of magnetoencephalographic neuroimaging to quantify the normative neural population responses and dynamic functional connectivity of somatosensory gating in the lower extremities of healthy human participants.r We show that somatosensory processing is subserved by a robust gating effect in the oscillatory domain, as well as a dynamic effect on interhemispheric functional connectivity between primary sensory cortices.r These results provide novel insight into the dynamic neural mechanisms that underlie the processing of somatosensory information in the human brain, and will be vital in better understanding the neural responses that are aberrant in gait-related neurological disorders (e.g. cerebral palsy).Abstract Sensory gating (SG) is a phenomenon in which neuronal responses to subsequent similar stimuli are weaker, and is considered to be an important mechanism for preventing excessive environmental stimulation from overloading shared neural resources. Although gating has been demonstrated in multiple sensory systems, the neural dynamics and developmental trajectory underlying SG remain poorly understood. In the present study, we adopt a data-driven approach to map the spectrotemporal amplitude and functional connectivity (FC) dynamics that support gating in the somatosensory system (somato-SG) in healthy children and adolescents using magnetoencephalography (MEG). These data underwent time-frequency decomposition and the significant signal changes were imaged using a beamformer. Voxel time series were then extracted from the peak voxels and these signals were examined in the time and time-frequency domains, and then subjected to dynamic FC analysis. The results obtained indicate a significant decrease in the amplitude of the neural response following the second stimulation relative to the first in the primary somatosensory cortex (SI). A significant decrease in response latency was also found between stimulations, and each stimulation induced a sharp decrease in FC between somatosensory cortical areas. Furthermore, there were no significant correlations between somato-SG metrics and age. We conclude that somato-SG can be observed in SI in both the time and oscillatory domains, with rich dynamics and alterations in inter-hemispheric FC, and that this phenomenon has already matured by early childhood. A better understanding of these dynamics may provide insight to the numerous psychiatric and neurologic conditions that have been associated with aberrant SG across multiple modalities.

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The effect of stimulation rate on the signal-to-noise ratio of evoked responses

Cited by 12 publications

References 12 publications

Cortical processing of near-threshold tactile stimuli: An MEG study

Cortical processing of near-threshold tactile stimuli: An MEG study

Signal and noise in P300 recordings to visual stimuli

Oscillatory dynamics and functional connectivity during gating of primary somatosensory responses

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