Giant central N20-P22 with normal area 3B N20-P20: An argument in favour of an area 3A generator of early median nerve cortical SEPs?

1. Selective ablations of the hand representations in postcentral cortical areas 3a, 3b, 1, and 2 were made in different combinations to determine each area's contribution to the responsivity and modality properties of neurons in the hand representation in SII. 2. Ablations that left intact only the postcentral areas that process predominantly cutaneous inputs (i.e., areas 3b and 1) yielded SII recording sites responsive to cutaneous stimulation and none driven exclusively by high-intensity or "deep" stimulation. Conversely, ablations that left intact only the postcentral areas that process predominantly deep receptor inputs (i.e., areas 3a and 2) yielded mostly SII recording sites that responded exclusively to deep stimulation. 3. Ablations that left intact only area 3a or only area 2 yielded substantial and roughly equal reductions in the number of deep receptive fields in SII. By contrast, ablations that left intact only area 3b or only area 1 yielded unequal reductions in the number of cutaneous receptive fields in SII: a small reduction when area 3b alone was intact but a somewhat larger one when only area 1 was intact. 4. Finally, when the hand representation in area 3b was ablated, leaving areas 3a, 1, and 2 fully intact, there was again a substantial reduction in the encounter rate of cutaneous receptive fields. 5. The partial ablations often led to unresponsive sites in the SII hand representation. In SII representations other than of the hand no such unresponsive sites were found and there were no substantial changes in the ratio of cutaneous to deep receptive fields, indicating that the foregoing results were not due to long-lasting postsurgical depression or effects of anesthesia. 6. The findings indicate that modality-specific information is relayed from postcentral cortical areas to SII along parallel channels, with cutaneous inputs transmitted via areas 3b and 1, and deep inputs via areas 3a and 2. Further, area 3b provides the major source of cutaneous input to SII, directly and perhaps also via area 1. 7. The results are in line with accumulating anatomic and electrophysiologic evidence pointing to an evolutionary shift in the organization of the somatosensory system from the general mammalian plan, in which tactile information is processed in parallel in SI and SII, to a new organization in higher primates in which the processing of tactile information proceeds serially from SI to SII. The presumed functional advantages of this evolutionary shift are unknown.

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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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Dipole source analyses of laser evoked potentials obtained from subdural grid recordings from primary somatic sensory cortex

Journal of Neurophysiology ◽

10.1152/jn.00135.2011 ◽

2011 ◽

Vol 106 (2) ◽

pp. 722-730 ◽

Cited By ~ 21

Author(s):

Ulf Baumgärtner ◽

Hagen Vogel ◽

Shinji Ohara ◽

Rolf-Detlef Treede ◽

Fred Lenz

Keyword(s):

Evoked Potentials ◽

Field Potential ◽

Sensory Cortex ◽

Source Analysis ◽

Spinothalamic Tract ◽

Laser Evoked Potentials ◽

Median Nerve Stimulation ◽

Area 3A ◽

Somatic Sensory Cortex ◽

Area 3B

The cortical potentials evoked by cutaneous application of a laser stimulus (laser evoked potentials, LEP) often include potentials in the primary somatic sensory cortex (S1), which may be located within the subdivisions of S1 including Brodmann areas 3A, 3B, 1, and 2. The precise location of the LEP generator may clarify the pattern of activation of human S1 by painful stimuli. We now test the hypothesis that the generators of the LEP are located in human Brodmann area 1 or 3A within S1. Local field potential (LFP) source analysis of the LEP was obtained from subdural grids over sensorimotor cortex in two patients undergoing epilepsy surgery. The relationship of LEP dipoles was compared with dipoles for somatic sensory potentials evoked by median nerve stimulation (SEP) and recorded in area 3B (see Baumgärtner U, Vogel H, Ohara S, Treede RD, Lenz FA. J Neurophysiol 104: 3029–3041, 2010). Both patients had an early radial dipole in S1. The LEP dipole was located medial, anterior, and deep to the SEP dipole, which suggests a nociceptive dipole in area 3A. One patient had a later tangential dipole with positivity posterior, which is opposite to the orientation of the SEP dipole in area 3B. The reversal of orientations between modalities is consistent with the cortical surface negative orientation resulting from superficial termination of thalamocortical neurons that receive inputs from the spinothalamic tract. Therefore, the present results suggest that the LEP may result in a radial dipole consistent with a generator in area 3A and a putative later tangential generator in area 3B.

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Plasticity of Primary Somatosensory Cortex Paralleling Sensorimotor Skill Recovery From Stroke in Adult Monkeys

Journal of Neurophysiology ◽

10.1152/jn.1998.79.4.2119 ◽

1998 ◽

Vol 79 (4) ◽

pp. 2119-2148 ◽

Cited By ~ 228

Author(s):

Christian Xerri ◽

Michael M. Merzenich ◽

Bret E. Peterson ◽

William Jenkins

Keyword(s):

Somatosensory Cortex ◽

Skill Acquisition ◽

Cortical Area ◽

Receptive Fields ◽

Field Size ◽

Primary Somatosensory Cortex ◽

Small Object ◽

Object Retrieval ◽

Area 3A ◽

Area 3B

Xerri, Christian, Michael M. Merzenich, Bret E. Peterson, and William Jenkins. Plasticity of primary somatosensory cortex paralleling sensorimotor skill recovery from stroke in adult monkeys. J. Neurophysiol. 79: 2119–2148, 1998. Adult owl and squirrel monkeys were trained to master a small-object retrieval sensorimotor skill. Behavioral observations along with positive changes in the cortical area 3b representations of specific skin surfaces implicated specific glabrous finger inputs as important contributors to skill acquisition. The area 3b zones over which behaviorally important surfaces were represented were destroyed by microlesions, which resulted in a degradation of movements that had been developed in the earlier skill acquisition. Monkeys were then retrained at the same behavioral task. They could initially perform it reasonably well using the stereotyped movements that they had learned in prelesion training, although they acted as if key finger surfaces were insensate. However, monkeys soon initiated alternative strategies for small object retrieval that resulted in a performance drop. Over several- to many-week-long period, monkeys again used the fingers for object retrieval that had been used successfully before the lesion, and reacquired the sensorimotor skill. Detailed maps of the representations of the hands in SI somatosensory cortical fields 3b, 3a, and 1 were derived after postlesion functional recovery. Control maps were derived in the same hemispheres before lesions, and in opposite hemispheres. Among other findings, these studies revealed the following 1) there was a postlesion reemergence of the representation of the fingertips engaged in the behavior in novel locations in area 3b in two of five monkeys and a less substantial change in the representation of the hand in the intact parts of area 3b in three of five monkeys. 2) There was a striking emergence of a new representation of the cutaneous fingertips in area 3a in four of five monkeys, predominantly within zones that had formerly been excited only by proprioceptive inputs. This new cutaneous fingertip representation disproportionately represented behaviorally crucial fingertips. 3) There was an approximately two times enlargement of the representation of the fingers recorded in cortical area 1 in postlesion monkeys. The specific finger surfaces employed in small-object retrieval were differentially enlarged in representation. 4) Multiple-digit receptive fields were recorded at a majority of emergent, cutaneous area 3a sites in all monkeys and at a substantial number of area 1 sites in three of five postlesion monkeys. Such fields were uncommon in area 1 in control maps. 5) Single receptive fields and the component fields of multiple-digit fields in postlesion representations were within normal receptive field size ranges. 6) No significant changes were recorded in the SI hand representations in the opposite (untrained, intact) control hemisphere. These findings are consistent with “substitution” and “vicariation” (adaptive plasticity) models of recovery from brain damage and stroke.

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Ipsilateral Area 3b Responses to Median Nerve Somatosensory Stimulation

NeuroImage ◽

10.1006/nimg.2002.1283 ◽

2003 ◽

Vol 18 (1) ◽

pp. 169-177 ◽

Cited By ~ 38

Author(s):

Akitake Kanno ◽

Nobukazu Nakasato ◽

Keisaku Hatanaka ◽

Takashi Yoshimoto

Keyword(s):

Median Nerve ◽

Somatosensory Stimulation ◽

Area 3B

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Vagal Input to Lateral Area 3a in Cat Cortex

Journal of Neurophysiology ◽

10.1152/jn.01054.2002 ◽

2003 ◽

Vol 90 (1) ◽

pp. 143-154 ◽

Cited By ~ 26

Author(s):

Shin-Ichi Ito ◽

A. D. (Bud) Craig

Keyword(s):

Evoked Potential ◽

Receptive Fields ◽

Lateral Part ◽

Afferent Activation ◽

Area 3A ◽

Polarity Reversals ◽

Masseteric Nerve ◽

Somatic Input ◽

Lateral Area ◽

Area 3B

Penfield's sensory homunculus included visceral organs at its lateral extreme, and vagal input was recently identified lateral to the intraoral representation in primary somatosensory cortex (S1) of rats. We tested whether vagal input is similarly located in cats where area 3b (equivalent to S1) is clearly distinguishable from adjacent regions. Field potentials were recorded from the intact dura over the left hemisphere using electrical stimulation of the left or right cervical vagus nerve in seven cats. A surface positive-negative potential was evoked from either side in the lateral part of the sigmoid gyrus. Finer mapping made at the pial surface with a microelectrode identified a focal site anteromedial to the anterior tip of the coronal sulcus. Depth recordings demonstrated polarity reversals and multi-unit vagal responses, indicating that the potentials were generated by an afferent activation focus in the middle layers of the cortex. The S1 mechanoreceptive representation was localized by mapping multi-unit somatosensory receptive fields in the middle cortical layers near the coronal sulcus. The vagal-evoked potential site was distinctly anterior to the intraoral S1 representation and adjacent to the masseteric-nerve-evoked potential focus. Lesions made at the focal site revealed that this site is cytoarchitectonically located in area 3a not area 3b. Thus vagal input to the sensorimotor cortex in cats resembles deep rather than cutaneous somatic input, similar to the localization of nociceptive-specific input to area 3a in monkeys. The possibilities are considered that this vagal input is involved in motor control and in the sensory experience of visceral afferent activity.

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Sensory Afferent Projections and Area 3b Somatotopy following Median Nerve Cut and Repair in Macaque Monkeys

Cerebral Cortex ◽

10.1093/cercor/4.4.391 ◽

1994 ◽

Vol 4 (4) ◽

pp. 391-407 ◽

Cited By ~ 40

Author(s):

S. L. Florence ◽

P. E. Garraghty ◽

J. T. Wall ◽

J. H. Kaas

Keyword(s):

Median Nerve ◽

Macaque Monkeys ◽

Afferent Projections ◽

Area 3B

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

Journal of Neurophysiology ◽

10.1152/jn.1989.62.3.694 ◽

1989 ◽

Vol 62 (3) ◽

pp. 694-710 ◽

Cited By ~ 420

Author(s):

T. Allison ◽

G. McCarthy ◽

C. C. Wood ◽

T. M. Darcey ◽

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.(ABSTRACT TRUNCATED AT 400 WORDS)

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Response of Anterior Parietal Cortex to Different Modes of Same-Site Skin Stimulation

Journal of Neurophysiology ◽

10.1152/jn.1998.80.6.3272 ◽

1998 ◽

Vol 80 (6) ◽

pp. 3272-3283 ◽

Cited By ~ 75

Author(s):

M. Tommerdahl ◽

K. A. Delemos ◽

O. V. Favorov ◽

C. B. Metz ◽

C. J. Vierck ◽

...

Keyword(s):

Parietal Cortex ◽

Optical Signal ◽

Stimulus Onset ◽

Neuron Activity ◽

Skin Site ◽

Intrinsic Signal ◽

Leading Role ◽

Lower Amplitude ◽

Area 3A ◽

Area 3B

Tommerdahl, M., K. A. Delemos, O. V. Favorov, C. B. Metz, C. J. Viereck, Jr., and B. L. Whitsel. Response of anterior parietal cortex to different modes of same-site skin stimulation. J. Neurophysiol. 80: 3272–3283, 1998. Intrinsic optical signal (IOS) imaging was used to study responses of the anterior parietal cortical hindlimb region (1 subject) and forelimb region (3 subjects) to repetitive skin stimulation. Subjects were four squirrel monkeys anesthetized with a halothane/nitrous oxide/oxygen gas mixtures. Cutaneous flutter of 25 Hz evoked a reflectance decrease in the sectors of cytoarchitectonic areas 3b and/or 1 that receive input from the stimulated skin site. The intrinsic signal evoked by 25-Hz flutter attained maximal intensity ≤2.5–3.5 s after stimulus onset, remained well maintained as long as stimulation was continued, and disappeared rapidly (usually ≤2–5 s) after stimulus termination. Repetitive skin heating stimuli were delivered via a probe/thermode in stationary contact with the skin (6 temperature ramps/trial; within-trial ramp frequency 0.42 Hz; intertrial interval 180 s; initial temperature 32–36°C; maximal temperature 48–52°C; rate of temperature change 19°C/s). Skin heating led to a large-amplitude reflectance decrease within a zone of area 3a, which neighbored the region in areas 3b/1 that emitted an intrinsic signal in response to same-site 25-Hz flutter in the same subject. In three of four subjects a lower-amplitude decrease in reflectance also occurred in a region of area 4 continuous with the area 3a region that responded maximally to same-site skin heating. The reflectance decrease evoked in areas 3a/4 by skin heating consistently exceeded in both intensity and spatial extent the decrease in reflectance evoked in areas 3b/1 by same-site 25-Hz cutaneous flutter. These findings are viewed as consistent with the proposal that area 3a plays a leading role in the anterior parietal cortical processing of the afferent drive evoked by skin-heating stimuli perceived as painful. In all four subjects the reflectance decrease evoked in areas 3a/4 by skin heating was accompanied by a simultaneous but opposite change in reflectance (a reflectance increase) within a large territory located immediately posterior to the regions that responded with a decrease in reflectance—an observation that raised the possibility that skin heating evoked opposing influences on the activity of area 3a and 3b/1 regions that receive input from the stimulated skin site. This was evaluated with the method of correlation mapping. The observations obtained with correlation mapping appear consistent with demonstrations by others that skin-heating stimuli perceived as painful by conscious subjects suppress/inhibit the anterior parietal response to innocuous mechanical skin stimulation. The opposing (relative to the response of area 3a) optical response of area 1 and/or area 3b during skin heating stimulation is attributed to suppression/inhibition of area 1 and/or area 3b neuron activity.

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