Responses of Human Somatosensory Cortex to Stimuli below Threshold for Conscious Sensation

Libet, Benjamin; Alberts, W. Watson; Wright, Elwood W.; Feinstein, B.

doi:10.1007/978-1-4612-0355-1_4

Cited by 52 publications

(88 citation statements)

References 10 publications

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“…Indeed, studies examining the cortical processing of innocuous somatosensory stimuli (Libet et al, 1967;Meador et al, 2002;Schubert et al, 2006) have also shown that early cortical responses (e.g., the P60 and the N80 waves) are consistently elicited by near-threshold somatosensory stimuli regardless of whether they are perceived, whereas later responses (e.g., the N140 and the P250 wave) become prominent only when the stimulus is perceived.…”

Section: Discussionmentioning

confidence: 99%

Characterizing the Cortical Activity through Which Pain Emerges from Nociception

Lee¹,

Mouraux²,

Iannetti³

2009

Journal of Neuroscience

138

115

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Nociception begins when A␦-and C-nociceptors are activated. However, the processing of nociceptive input by the cortex is required before pain can be consciously experienced from nociception. To characterize the cortical activity related to the emergence of this experience, we recorded, in humans, laser-evoked potentials elicited by physically identical nociceptive stimuli that were either perceived or unperceived. Infrared laser pulses, which selectively activate skin nociceptors, were delivered to the hand dorsum either as a pair of rapidly succeeding and spatially displaced stimuli (two-thirds of trials) or as a single stimulus (one-third of trials). After each trial, subjects reported whether one or two distinct painful pinprick sensations, associated with A␦-nociceptor activation, had been perceived. The psychophysical feedback after each pair of stimuli was used to adjust the interstimulus interval (ISI) of the subsequent pair: when a single percept was reported, ISI was increased by 40 ms; when two distinct percepts were reported, ISI was decreased by 40 ms. This adaptive algorithm ensured that the probability of perceiving the second stimulus of the pair tended toward 0.5. We found that the magnitude of the early-latency N1 wave was similar between perceived and unperceived stimuli, whereas the magnitudes of the later N2 and P2 waves were reduced when stimuli were unperceived. These findings suggest that the N1 wave represents an early stage of sensory processing related to the ascending nociceptive input, whereas the N2 and P2 waves represent a later stage of processing related, directly or indirectly, to the perceptual outcome of this nociceptive input.

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Section: Discussionmentioning

confidence: 99%

Characterizing the Cortical Activity through Which Pain Emerges from Nociception

Lee¹,

Mouraux²,

Iannetti³

2009

Journal of Neuroscience

138

115

View full text Add to dashboard Cite

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“…Traditionally, S1 is considered to be involved in the sensorydiscriminative component of pain processing (Bushnell et al, 1999) and single neurons in monkey S1 code for stimulus intensity, location, and duration (Kaas, 1993;Kenshalo et al, 2000). In neurological patients, somatosensory stimuli below threshold for conscious sensation elicited activation of S1 but not of downstream areas (Libet et al, 1967) and isolated electrical stimulation of S1 did not evoke the sensation of pain (Penfield and Jasper, 1954). The affective-motivational and cognitive evaluative components of pain are only partly understood but have been proposed to depend on insular, anterior cingulate, and posterior parietal cortices (Ingvar, 1999;Treede et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

Cortical Processing of Noxious Somatosensory Stimuli in the Persistent Vegetative State

et al. 2002

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“…Early cortical responses (less than ϳ100 ms from stimulus onset) evoked by somatosensory stimuli have been found to be similar for consciously perceived and unperceived stimuli (Libet et al, 1967;Ray et al, 1999;Meador et al, 2002). The earliest component, N1, of the auditory (Parasuraman and Beatty, 1980) and visual (Supèr et al, 2001;Pins and Ffytche, 2003) evoked responses (ERs) thus far found to reflect stimulus detection peaks at ϳ100 -120 ms after stimulus onset.…”

Section: Introductionmentioning

confidence: 98%

“…The earliest component, N1, of the auditory (Parasuraman and Beatty, 1980) and visual (Supèr et al, 2001;Pins and Ffytche, 2003) evoked responses (ERs) thus far found to reflect stimulus detection peaks at ϳ100 -120 ms after stimulus onset. Electrophysiological and functional imaging studies have shown that not only the processing of the consciously perceived stimuli (Sahraie et al, 1997;Feinstein et al, 2004;Marois et al, 2004) but also the processing of imperceptible sensory stimuli (Libet et al, 1967;Sahraie et al, 1997;Colder and Tanenbaum, 1999;Ray et al, 1999;Meador et al, 2002;Blankenburg et al, 2003) involves a widespread network, including the primary sensory cortex (Libet et al, 1967;Sahraie et al, 1997;Colder and Tanenbaum, 1999;Ray et al, 1999;Meador et al, 2002;Blankenburg et al, 2003), as well as several areas higher in the processing hierarchy (Brazdil et al, 2001;Naccache and Dehaene, 2001;Blankenburg et al, 2003). Together, these data suggest that the neural correlates of conscious perception emerge at later stages and higher levels of sensory processing, after an initial period of 100 -120 ms, during which stimulus-locked neuronal processing does not distinguish the subsequently perceived stimuli from those escaping conscious perception.…”

Section: Introductionmentioning

confidence: 99%

Early Neural Correlates of Conscious Somatosensory Perception

Linkenkaer‐Hansen¹,

Näätänen²,

Palva³

2005

J. Neurosci.

247

224

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The cortical processing of consciously perceived and unperceived somatosensory stimuli is thought to be identical during the first 100 -120 ms after stimulus onset. Thereafter, the electrophysiological correlates of conscious perception have been shown to be reflected in the N1 component of the evoked response as well as in later (Ͼ200 ms) nonstimulus-locked ␥-band (28 -50 Hz) oscillatory activity. To evaluate more specifically the time course and correlation of neuronal oscillations with conscious perception, we recorded neuromagnetic responses to threshold-intensity somatosensory stimuli. We show here that cortical broadband activities phase locked to the subsequently perceived stimuli in somatosensory, frontal, and parietal regions as early as 30 -70 ms from stimulus onset, whereas the phase locking to the unperceived stimuli was weak and primarily restricted to somatosensory regions. Such stimulus locking also preceded the perceived stimuli, indicating that the phase of ongoing cortical activities biases subsequent perception. Furthermore, the data show that the stimulus locking was present in the -(4 -8 Hz), ␣-(8 -14 Hz), ␤-(14 -28 Hz), and ␥-(28 -40 Hz) frequency bands, of which the widespread ␣-band component was dominant for the consciously perceived stimuli but virtually unobservable for the unperceived stimuli. Our results show that the neural correlates of conscious perception are already found during the earliest stages of cortical processing from 30 to 150 ms after stimulus onset and suggest that ␣-frequency-band oscillations have a role in the neural mechanisms of sensory awareness.

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Responses of Human Somatosensory Cortex to Stimuli below Threshold for Conscious Sensation

Cited by 52 publications

References 10 publications

Characterizing the Cortical Activity through Which Pain Emerges from Nociception

Characterizing the Cortical Activity through Which Pain Emerges from Nociception

Cortical Processing of Noxious Somatosensory Stimuli in the Persistent Vegetative State

Early Neural Correlates of Conscious Somatosensory Perception

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