Neural Activation in the Somatosensory Cortex by Electrotactile Stimulation of the Fingers: A Human fMRI Study

Functional magnetic resonance imaging (fMRI) was used to measure activity in human somatosensory cortex and to test for cross-digit suppression. Subjects received stimulation (vibration of varying amplitudes) to the right thumb (target) with or without concurrent stimulation of the right middle finger (mask). Subjects were less sensitive to target stimulation (psychophysical detection thresholds were higher) when target and mask digits were stimulated concurrently compared with when the target was stimulated in isolation. fMRI voxels in a region of the left postcentral gyrus each responded when either digit was stimulated. A regression model (called a forward model) was used to separate the fMRI measurements from these voxels into two hypothetical channels, each of which responded selectively to only one of the two digits. For the channel tuned to the target digit, responses in the left postcentral gyrus increased with target stimulus amplitude but were suppressed by concurrent stimulation to the mask digit, evident as a shift in the gain of the response functions. For the channel tuned to the mask digit, a constant baseline response was evoked for all target amplitudes when the mask was absent and responses decreased with increasing target amplitude when the mask was concurrently presented. A computational model based on divisive normalization provided a good fit to the measurements for both mask-absent and target + mask stimulation. We conclude that the normalization model can explain cross-digit suppression in human somatosensory cortex, supporting the hypothesis that normalization is a canonical neural computation.

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Activation of thalamic ventroposteriolateral neurons by phrenic nerve afferents in cats and rats

Journal of Applied Physiology ◽

10.1152/japplphysiol.00334.2002 ◽

2003 ◽

Vol 94 (1) ◽

pp. 220-226 ◽

Cited By ~ 12

Author(s):

Weirong Zhang ◽

Paul W. Davenport

Keyword(s):

Electrical Stimulation ◽

Somatosensory Cortex ◽

Phrenic Nerve ◽

Proprioceptive Information ◽

Neural Responses ◽

Afferent Stimulation ◽

Physiological Conditions ◽

Sensory Pathways ◽

Increased Activity ◽

Stimulation Of

It has been demonstrated that phrenic nerve afferents project to somatosensory cortex, yet the sensory pathways are still poorly understood. This study investigated the neural responses in the thalamic ventroposteriolateral (VPL) nucleus after phrenic afferent stimulation in cats and rats. Activation of VPL neurons was observed after electrical stimulation of the contralateral phrenic nerve. Direct mechanical stimulation of the diaphragm also elicited increased activity in the same VPL neurons that were activated by electrical stimulation of the phrenic nerve. Some VPL neurons responded to both phrenic afferent stimulation and shoulder probing. In rats, VPL neurons activated by inspiratory occlusion also responded to stimulation on phrenic afferents. These results demonstrate that phrenic afferents can reach the VPL thalamus under physiological conditions and support the hypothesis that the thalamic VPL nucleus functions as a relay for the conduction of proprioceptive information from the diaphragm to the contralateral somatosensory cortex.

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Human proprioceptive adaptations during states of height-induced fear and anxiety

Journal of Neurophysiology ◽

10.1152/jn.01030.2010 ◽

2011 ◽

Vol 106 (6) ◽

pp. 3082-3090 ◽

Cited By ~ 30

Author(s):

Justin R. Davis ◽

Brian C. Horslen ◽

Kei Nishikawa ◽

Katie Fukushima ◽

Romeo Chua ◽

...

Keyword(s):

Evoked Potentials ◽

Somatosensory Cortex ◽

Somatosensory Evoked Potentials ◽

Emotional Experience ◽

Afferent Feedback ◽

Triceps Surae ◽

Feedback Gain ◽

Postural Threat ◽

Fear And Anxiety ◽

Stimulation Of

Clinical and experimental research has demonstrated that the emotional experience of fear and anxiety impairs postural stability in humans. The current study investigated whether changes in fear and anxiety can also modulate spinal stretch reflexes and the gain of afferent inputs to the primary somatosensory cortex. To do so, two separate experiments were performed on two separate groups of participants while they stood under conditions of low and high postural threat. In experiment 1, the proprioceptive system was probed using phasic mechanical stimulation of the Achilles tendon while simultaneously recording the ensuing tendon reflexes in the soleus muscle and cortical-evoked potentials over the somatosensory cortex during low and high threat conditions. In experiment 2, phasic electrical stimulation of the tibial nerve was used to examine the effect of postural threat on somatosensory evoked potentials. Results from experiment 1 demonstrated that soleus tendon reflex excitability was facilitated during states of height-induced fear and anxiety while the magnitude of the tendon-tap-evoked cortical potential was not significantly different between threat conditions. Results from experiment 2 demonstrated that the amplitudes of somatosensory-evoked potentials were also unchanged between threat conditions. The results support the hypothesis that muscle spindle sensitivity in the triceps surae muscles may be facilitated when humans stand under conditions of elevated postural threat, although the presumed increase in spindle sensitivity does not result in higher afferent feedback gain at the level of the somatosensory cortex.

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Human cortical potentials evoked by stimulation of the median nerve. II. Cytoarchitectonic areas generating long-latency activity

Journal of Neurophysiology ◽

10.1152/jn.1989.62.3.711 ◽

1989 ◽

Vol 62 (3) ◽

pp. 711-722 ◽

Cited By ~ 225

Author(s):

T. Allison ◽

G. McCarthy ◽

C. C. Wood ◽

P. D. Williamson ◽

D. D. Spencer

Keyword(s):

Spatial Distribution ◽

Median Nerve ◽

Somatosensory Cortex ◽

Sensorimotor Cortex ◽

Preceding Paper ◽

Short Latency ◽

Cortical Surface ◽

Long Latency ◽

Area 3B ◽

Stimulation Of

1. The anatomic generators of human median nerve somatosensory evoked potentials (SEPs) in the 40 to 250-ms latency range were investigated in 54 patients by means of cortical-surface and transcortical recordings obtained during neurosurgery. 2. Contralateral stimulation evoked three groups of SEPs recorded from the hand representation area of sensorimotor cortex: P45-N80-P180, recorded anterior to the central sulcus (CS) and maximal on the precentral gyrus; N45-P80-N180, recorded posterior to the CS and maximal on the postcentral gyrus; and P50-N90-P190, recorded near and on either side of the CS. 3. P45-N80-P180 inverted in polarity to N45-P80-N180 across the CS but was similar in polarity from the cortical surface and white matter in transcortical recordings. These spatial distributions were similar to those of the short-latency P20-N30 and N20-P30 potentials described in the preceding paper, suggesting that these long-latency potentials are generated in area 3b of somatosensory cortex. 4. P50-N90-P190 was largest over the anterior one-half of somatosensory cortex and did not show polarity inversion across the CS. This spatial distribution was similar to that of the short-latency P25-N35 potentials described in the preceding paper and, together with our and Goldring et al. 1970; Stohr and Goldring 1969 transcortical recordings, suggest that these long-latency potentials are generated in area 1 of somatosensory cortex. 5. SEPs of apparently local origin were recorded from several regions of sensorimotor cortex to stimulation of the ipsilateral median nerve. Surface and transcortical recordings suggest that the ipsilateral potentials are generated not in area 3b, but rather in other regions of sensorimotor cortex perhaps including areas 4, 1, 2, and 7. This spatial distribution suggests that the ipsilateral potentials are generated by transcallosal input from the contralateral hemisphere. 6. Recordings from the periSylvian region were characterized by P100 and N100, recorded above and below the Sylvian sulcus (SS) respectively. This distribution suggests a tangential generator located in the upper wall of the SS in the second somatosensory area (SII). In addition, N125 and P200, recorded near and on either side of the SS, suggest a radial generator in a portion of SII located in surface cortex above the SS. 7. In comparison with the short-latency SEPs described in the preceding paper, the long-latency potentials were more variable and were more affected by intraoperative conditions.

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Cholinergic upregulation by optogenetic stimulation of nucleus basalis after photothrombotic stroke in forelimb somatosensory cortex improves endpoint and motor but not sensory control of skilled reaching in mice

10.1101/2020.06.09.143354 ◽

2020 ◽

Author(s):

Behroo Mirza Agha ◽

Roya Akbary ◽

Arashk Ghasroddashti ◽

Mojtaba Nazari-Ahangarkolaee ◽

Ian Q. Whishaw ◽

...

Keyword(s):

Somatosensory Cortex ◽

Sensorimotor Integration ◽

Motor Behavior ◽

Field Potential ◽

Cholinergic Neurons ◽

Nucleus Basalis ◽

Optogenetic Stimulation ◽

Photothrombotic Stroke ◽

Skilled Reaching ◽

Stimulation Of

AbstractA network of cholinergic neurons in the basal forebrain innerve the forebrain and are proposed to contribute to a variety of functions including attention, and cortical plasticity. This study examined the contribution of the nucleus basalis cholinergic projection to the sensorimotor cortex on recovery on a skilled reach-to-eat task following photothrombotic stroke in the forelimb region of the somatosensory cortex. Mice were trained to perform a single-pellet skilled reaching task and their pre and poststroke performance, from Day 4 to Day 28 poststroke, was assessed frame-by-frame by video analysis with end point, movement and sensorimotor integration measures. Somatosensory forelimb lesions produced impairments in endpoint and movement component measures of reaching and increased the incidence of fictive eating, a sensory impairment in mistaking a missed reach for a successful reach. Upregulated acetylcholine (ACh) release, as measured by local field potential recording, elicited via optogenetic stimulation of the nucleus basalis improved recovery of reaching and improved movement scores but did not affect a sensorimotor integration impairment poststroke. The results show that the mouse cortical forelimb somatosensory region contributes to forelimb motor behavior and suggest that ACh upregulation could serve as an adjunct to behavioral therapy for the acute treatment of stroke.

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