Time-dependence of SI RA neuron response to cutaneous flutter stimulation

Abstract

Spike discharge activity of RA-type SI cortical neurons was recorded extracellularly in anesthetized monkeys and cats. Multiple applications (trials) of 10-50 Hz sinusoidal vertical skin displacement stimulation ("flutter") were delivered to the receptive field (RF). Analysis revealed large and systematic temporal trends not only in SI RA neuron responsivity (measured as spikes/s and as spikes/stimulus cycle), but also in entrainment, and in phase angle of the entrained responses. In contrast to SI RA neurons, the response of RA skin afferents to comparable conditions of skin flutter stimulation exhibited little or no dynamics. The occurrence and form of the SI RA neuron response dynamics that accompany skin flutter stimulation are shown to depend on factors such as stimulus frequency and the locus of the recording site in the global cortical response pattern. Comparison of recordings obtained in near-radial vs tangential microelectrode penetrations further reveals that the SI RA neuron response dynamics that occur during skin flutter stimulation are relatively consistent within, but heterogeneous across column-sized regions. The observed SI RA neuron response dynamics are suggested to account, in part, for the improved capacity to discriminate stimulus frequency after an exposure ("adaptation") to skin flutter stimulation (Goble and Hollins, J Acoust Soc Am 96: 771-780, 1994). Parallels with recent proposals about the contributions to visual perception of short-term primary sensory cortical neuron dynamics and synchrony in multineuron spike activity patterns are identified and discussed.

Tactile Perception in Adults with Autism: a Multidimensional Psychophysical Study

“…3B, the autism group shows an adaptation-related elevation in threshold during the second block of trials, and then returns to the baseline threshold, as do controls. While it has long been demonstrated that peripheral afferents demonstrate fatigue in response to vibration exposure (Lundstrom & Johansson, 1986), the adaptation tapped by this protocol is likely to reflect both peripheral and central neuronal activity (Bensmaia, Leung, Hsiao, & Johnson, 2005;Goble & Hollins, 1993;Whitsel et al, 2003). Thus, failure of central neurons to adapt to somatosensory stimulation does not appear to account for reports of tactile hypersensitivity in autism.…”

Ipsilateral Input Modifies the Primary Somatosensory Cortex Response to Contralateral Skin Flutter

“…First, they provide unambiguous evidence that a skin flutter stimulus to the ipsilateral thenar eminence of the squirrel monkey evokes a statistically significant optical response (OIS; an absorbance increase) within the same SI territory than in previous combined OIS-neurophysiological studies (Shoham and Grinvald, 2001;Whitsel et al, 2001Whitsel et al, , 2003Tommerdahl et al, 2002) was shown to undergo increased single-neuron spike discharge activity in response to flutter stimulation of the contralateral hand. Second, our experiments demonstrate that simultaneous bilateral stimulation of both the ipsilateral and contralateral hand sites evokes an SI response significantly smaller and spatially less coherent than the response evoked in the same SI region by stimulation of only a site on the contralateral hand, a finding that strongly suggests that input from the ipsilateral hand can modify the ability of SI to process information about the status of mechanoreceptors in the skin of the contralateral hand.…”

Effects of adaptation on the capacity to differentiate simultaneously delivered dual-site vibrotactile stimuli

“…This enhancement of discrimination capacity could be due at least in part to the moment-to-moment changes that occur in the spatio-temporal patterns of response with repetitive vibrotactile stimulation. For example, repetitive vibrotactile stimulation of the skin leads not only to a more funneled SI cortical response (Chen et al, 2003;Juliano et al, 1989;LaMotte and Mountcastle, 1975;Tommerdahl et al, 2002;Tommerdahl et al, 1993;Tommerdahl et al, 1996;Whitsel et al, 1991) but to changes in the temporal Whitsel et al, 2003) as well as the spatial pattern of cortical activity evoked (Simons et al, 2007;Simons et al, 2005;Tommerdahl et al, 2002). Thus, the patterns of evoked SI cortical response maintain a number of spatial features that could provide the context in which subsequent stimuli are interpreted.…”