Functional properties of single neurons in the primate face primary somatosensory cortex. I. Relations with trained orofacial motor behaviors

1994 ◽  
Vol 71 (6) ◽  
pp. 2377-2390 ◽  
Author(s):  
L. D. Lin ◽  
G. M. Murray ◽  
B. J. Sessle
Keyword(s):  
Firing Rate ◽  
Somatosensory Cortex ◽  
Primary Somatosensory Cortex ◽  
Upper Lip ◽  
Tongue Protrusion ◽  
Lower Lip ◽  
Tactile Stimuli ◽  
Significant Difference ◽  
The Face ◽  
Afferent Inputs

1. We have demonstrated recently that reversible, cooling-induced inactivation of the face primary somatosensory cortex (SI) severely impairs the successful performance of a tongue-protrusion task but has relatively minor effects on the performance of a biting task. In an attempt to establish a neuronal correlate for these different behavioral relations, the present study was initiated to document the mechanoreceptive field properties of a population of face SI neurons and their activity during the tongue-protrusion and biting tasks. 2. Within SI, the representation of the face was found immediately lateral to that of the hand, and there was a clear somatotopic pattern of organization within face SI: the periorbital or nose region was located most medially in the face SI, then followed laterally in sequence the representation of the upper lip, lower lip, and intraoral area. A mechanoreceptive field (RF) was identified for 253 neurons, which included 162 “lip RF” neurons receiving mechanosensitive afferent inputs from the upper lip, lower lip, or both; 72 “tongue RF” neurons that received mechanosensitive afferent inputs from the tongue; 11 “periodontium RF” neurons receiving periodontal inputs; and 8 neurons that received inputs from other orofacial regions. 3. Nearly all (249/253) of the face SI neurons responded to light tactile stimuli, and most of them received contralateral inputs (78%) and showed a rapidly adapting (RA) response to tactile stimulation (82%). There was no significant difference in the ratio of slowly adapting (SA) to RA neurons in areas 3b and 1. 4. For 193 neurons studied in one or both of the orofacial tasks, 113 were found, on the basis of histological reconstruction, to be distributed in area 1, 61 in area 3b, and 19 in area 2. 5. The firing rate of most tongue RF (79% of 56) neurons and lip RF (60% of 93) neurons tested was significantly altered during the tongue-protrusion task. Only some (14% of 36 tongue RF neurons and 34% of the 92 lip RF neurons tested) showed a significant change in firing rate during the biting task. Three of 7 periodontium RF neurons studied in the tongue-protrusion task altered their firing rate and 5 of 10 altered their firing rate during the biting task. 6. Most of the 116 face SI neurons studied during both tasks exhibited a preferential relation to the tongue-protrusion task as distinct from the biting task, and none showed task-related activity during the biting task only.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional properties of single neurons in the primate face primary somatosensory cortex. II. Relations with different directions of trained tongue protrusion

1994 ◽  
Vol 71 (6) ◽  
pp. 2391-2400 ◽  
Author(s):  
L. D. Lin ◽  
G. M. Murray ◽  
B. J. Sessle
Keyword(s):  
Firing Rate ◽  
Somatosensory Cortex ◽  
Discharge Frequency ◽  
Primary Somatosensory Cortex ◽  
Electromyographic Activity ◽  
Tongue Protrusion ◽  
Preferred Direction ◽  
Time Interaction ◽  
Task Period ◽  
Significant Difference

1. In previous papers we have presented evidence suggesting an important role for the face primary somatosensory cortex (SI) in the fine control of tongue movements. These findings, plus our earlier evidence that many neurons in face motor cortex (MI) may exhibit firing rates related to the direction of tongue protrusion, led us to test the hypothesis that variations in the direction of a tongue-protrusion movement would be associated with variations in the activity of different face SI neurons. 2. Two monkeys were trained to perform a tongue-protrusion task in each of three directions: the task transducer was positioned at 0 degrees, 30 degrees to the left, or 30 degrees to the right from the midsagittal plane. The latter two positions were termed asymmetrical tongue-protrusion task positions. Single-neuron activity was recorded from face SI during trials of the tongue-protrusion task at each of two or three of the above positions. In addition, the mechanoreceptive field (RF) was delineated for each neuron. 3. Directional relations were found in 25 (58%) of the 43 neurons studied; this included 20 neurons showing a significant direction-by-time interaction in firing rate, i.e., the change of firing rate from the pretrial period to the task period was significantly different between different directions, and 5 showing no direction-by-time interaction but a significant difference in firing rate between different directions of the tongue-protrusion task. 4. Of the 43 neurons investigated, 21 and 20 had a RF on the tongue and lips, respectively (“tongue RF” and “lip RF” neurons), and the remaining 2 received mechanosensitive afferent inputs from other orofacial regions. There was no significant difference in the incidence of directional sensitivity between the neurons with a tongue RF and those with a lip RF (12/21 and 11/20, respectively). 5. Eight of the 25 “directional” neurons were located in area 3b and 17 in area 1. There was no significant difference in the proportion of directional neurons between areas 3b and 1. 6. The increase in discharge frequency at the preferred direction was, on the average for the 25 directional neurons, 39% over the mean discharge frequency observed during the task period for all directions of the tongue-protrusion task. Eight directional neurons showed a significant increase in firing rate during the tongue-protrusion task up to 130 ms before the onset of genioglossus electromyographic activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional properties of single neurons in the primate face primary somatosensory cortex. III. Modulation of responses to peripheral stimuli during trained orofacial motor behaviors

1994 ◽  
Vol 71 (6) ◽  
pp. 2401-2413 ◽  
Author(s):  
L. D. Lin ◽  
B. J. Sessle
Keyword(s):  
Somatosensory Cortex ◽  
Neuronal Activity ◽  
Lingual Nerve ◽  
Primary Somatosensory Cortex ◽  
Single Neurons ◽  
Tongue Protrusion ◽  
Task Period ◽  
The Face ◽  
Evoked Activity ◽  
Two Phases

1. In previous papers we have demonstrated that most single neurons in the face primary somatosensory cortex (SI) alter their firing rate during a trained tongue-protrusion task and some also during a trained biting task. Although the data suggest that some of the task-related activity in face SI might conceivably come from reafferent inputs from moving orofacial structures, it is possible that orofacial inputs are modulated during the trained orofacial movements. This study was initiated to investigate the possible modulation of evoked orofacial somatosensory responses of face SI neurons during trained tongue-protrusion and biting tasks. 2. Two monkeys were trained to perform a tongue-protrusion and a biting task and to accept stimulation applied to the facial skin or the lingual nerve during the tasks. For SI neurons with a tongue mechanoreceptive field (RF), electrical stimulation was applied to the lingual nerve to elicit neuronal activity; for SI neurons with a RF at the other locations, electrical or mechanical stimulation was applied to the RF to elicit neuronal activity. Modulation of neuronal activity evoked by low-threshold stimulation of the RF was tested, during the tongue-protrusion and/or biting tasks, in 44 face SI neurons and an additional 3 forelimb SI neurons with a palm RF (palm RF neurons). The 44 face SI neurons included 13 with a tongue RF (tongue RF neurons), 29 with a lip RF (lip RF neurons), and 2 with a lateral face RF (face RF neurons). 3. For face SI neurons tested during both force dynamic and holding phases of the task period, the evoked activity (i.e., the number of evoked spikes in 50 ms after the onset of stimulation) was decreased in at least one of the two phases for the majority (90%) of 31 neurons studied during the tongue-protrusion task and 61% of 23 studied during the biting task. The proportion of neurons modulated during the tongue-protrusion task was significantly higher than that during the biting task. For the 18 face SI tested during both tasks, a decrease in evoked activity occurred in 10 lip RF neurons for both tasks and in the remaining 5 lip RF and 3 tongue RF neurons for the tongue-protrusion task only. No neurons tested showed a clear facilitation of evoked activity during the task period of either task.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Heterogeneous Integration of Bilateral Whisker Signals by Neurons in Primary Somatosensory Cortex of Awake Rats

2005 ◽  
Vol 93 (5) ◽  
pp. 2966-2973 ◽  
Author(s):  
Michael C. Wiest ◽  
Nick Bentley ◽  
Miguel A. L. Nicolelis
Keyword(s):  
Somatosensory Cortex ◽  
Single Unit ◽  
Temporal Integration ◽  
Primary Somatosensory Cortex ◽  
Neural Responses ◽  
Hemispheric Processing ◽  
Tactile Stimuli ◽  
The Face ◽  
Left And Right ◽  
High Level

Bilateral single-unit recordings in primary somatosensory cortex (S1) of anesthetized rats have revealed substantial cross talk between cortical hemispheres, suggesting the possibility that behaviorally relevant bilateral integration could occur in S1. To determine the extent of bilateral neural responses in awake animals, we recorded S1 multi- and single-unit activity in head-immobilized rats while stimulating groups of 4 whiskers from the same column on both sides of the head. Results from these experiments confirm the widespread presence of single units responding to tactile stimuli on either side of the face in S1 of awake animals. Quantification of bilateral integration by multiunits revealed both facilitative and suppressive integration of bilateral inputs. Varying the interval between left and right whisker stimuli between 0 and 120 ms showed the temporal integration of bilateral stimuli to be dominated on average by suppression at intervals around 30 ms, in agreement with comparable recordings in anesthetized animals. Contrary to the anesthetized data, in the awake animals we observed a high level of heterogeneity of bilateral responses and a strong interaction between synchronous bilateral stimuli. The results challenge the traditional conception of highly segregated hemispheric processing channels in the rat S1 cortex, and support the hypothesis that callosal cross-projections between the two hemispheres mediate rats' known ability to integrate bilateral whisker signals.

The effect of bilateral cold block of the primate face primary somatosensory cortex on the performance of trained tongue-protrusion task and biting tasks

1993 ◽  
Vol 70 (3) ◽  
pp. 985-996 ◽  
Author(s):  
L. D. Lin ◽  
G. M. Murray ◽  
B. J. Sessle
Keyword(s):  
Somatosensory Cortex ◽  
Primary Motor Cortex ◽  
Movement Control ◽  
Primary Somatosensory Cortex ◽  
Emg Activity ◽  
Success Rates ◽  
Tongue Protrusion ◽  
Reversible Inactivation ◽  
Control Series ◽  
Holding Period

1. Studies using ablation, intracortical microstimulation (ICMS) and surface stimulation, and single-neuron recordings have suggested that the primate primary somatosensory cortex (SI) may play an important role in movement control. Our aim was to determine whether bilateral inactivation of face SI would indeed interfere with the control of tongue or jaw-closing movements. 2. Effects of reversible inactivation by cooling of face SI was investigated in two monkeys trained to perform both a tongue-protrusion task and a biting task. The cooling experiments were carried out after the orofacial representation within SI was identified by systematically defining the mechanoreceptive field of single neurons recorded in face SI. The deficits in the tongue or jaw-closing movement were evaluated by the success rates for the monkeys' performance of both tasks and by the force and electromyographic (EMG) activity recorded from the masseter, genioglossus, and digastric muscles associated with the tasks. 3. During bilateral cooling of face SI, there was a statistically significant reduction in the success rates for the performance of the tongue-protrusion task in comparison with control series of trials while the thermodes used to cool face SI were kept at 37 degrees C. Detailed analyses of force and EMG activity showed that the principal deficit was the inability of the monkeys to maintain a steady tongue-protrusive force in the force holding period during each trial and to exert a consistent tongue-protrusion force between different trials. The task performance returned to control protocol levels at 4 min after commencement of rewarming. 4. Identical cooling conditions did not significantly affect the success rates for the performance of the biting task. Although the extent of the deficit was not severe enough to cause a significant reduction in successful rates for the biting task, cooling did significantly affect the ability of the monkeys to maintain a steady force in the holding period during each trial and to exert a consistent force between different trials. In one monkey the success rate of the biting task was also not affected by bilaterally cooling of face SI with a pair of larger thermodes placed on the dura over most of the face SI, face primary motor cortex (face MI), and adjacent cortical regions.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Common Synaptic Input to the Human Hypoglossal Motor Nucleus

2011 ◽  
Vol 105 (1) ◽  
pp. 380-387 ◽  
Author(s):  
Christopher M. Laine ◽  
E. Fiona Bailey
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Synaptic Input ◽  
Motor Units ◽  
Motor Nucleus ◽  
Tongue Protrusion ◽  
Ongoing Research ◽  
Airway Patency ◽  
Significant Difference ◽  
Common Drive

The tongue plays a key role in various volitional and automatic functions such as swallowing, maintenance of airway patency, and speech. Precisely how hypoglossal motor neurons, which control the tongue, receive and process their often concurrent input drives is a subject of ongoing research. We investigated common synaptic input to the hypoglossal motor nucleus by measuring the coordination of spike timing, firing rate, and oscillatory activity across motor units recorded from unilateral (i.e., within a belly) or bilateral (i.e., across both bellies) locations within the genioglossus (GG), the primary protruder muscle of the tongue. Simultaneously recorded pairs of motor units were obtained from 14 healthy adult volunteers using tungsten microelectrodes inserted percutaneously into the GG while the subjects were engaged in volitional tongue protrusion or rest breathing. Bilateral motor unit pairs showed concurrent low frequency alterations in firing rate (common drive) with no significant difference between tasks. Unilateral motor unit pairs showed significantly stronger common drive in the protrusion task compared with rest breathing, as well as higher indices of synchronous spiking (short-term synchrony). Common oscillatory input was assessed using coherence analysis and was observed in all conditions for frequencies up to ∼5 Hz. Coherence at frequencies up to ∼10 Hz was strongest in motor unit pairs recorded from the same GG belly in tongue protrusion. Taken together, our results suggest that cortical drive increases motor unit coordination within but not across GG bellies, while input drive during rest breathing is distributed uniformly to both bellies of the muscle.

scholarly journals Computational Role of Large Receptive Fields in the Primary Somatosensory Cortex

2008 ◽  
Vol 100 (1) ◽  
pp. 268-280 ◽  
Author(s):  
Guglielmo Foffani ◽  
John K. Chapin ◽  
Karen A. Moxon
Keyword(s):  
Somatosensory Cortex ◽  
Receptive Fields ◽  
Spike Timing ◽  
Spike Count ◽  
Primary Somatosensory Cortex ◽  
Single Neurons ◽  
Tuning Curves ◽  
Tactile Stimuli ◽  
Somatosensory Information

Computational studies are challenging the intuitive view that neurons with broad tuning curves are necessarily less discriminative than neurons with sharp tuning curves. In the context of somatosensory processing, broad tuning curves are equivalent to large receptive fields. To clarify the computational role of large receptive fields for cortical processing of somatosensory information, we recorded ensembles of single neurons from the infragranular forelimb/forepaw region of the rat primary somatosensory cortex while tactile stimuli were separately delivered to different locations on the forelimbs/forepaws under light anesthesia. We specifically adopted the perspective of individual columns/segregates receiving inputs from multiple body location. Using single-trial analyses of many single-neuron responses, we obtained two main results. 1) The responses of even small populations of neurons recorded from within the same estimated column/segregate can be used to discriminate between stimuli delivered to different surround locations in the excitatory receptive fields. 2) The temporal precision of surround responses is sufficiently high for spike timing to add information over spike count in the discrimination between surround locations. This surround spike-timing code (i) is particularly informative when spike count is ambiguous, e.g., in the discrimination between close locations or when receptive fields are large, (ii) becomes progressively more informative as the number of neurons increases, (iii) is a first-spike code, and (iv) is not limited by the assumption that the time of stimulus onset is known. These results suggest that even though large receptive fields result in a loss of spatial selectivity of single neurons, they can provide as a counterpart a sophisticated temporal code based on latency differences in large populations of neurons without necessarily sacrificing basic information about stimulus location.

EMG Feedback and Recovery of Facial and Speech Gestures Following Neural Anastomosis

1978 ◽  
Vol 43 (1) ◽  
pp. 9-20 ◽  
Author(s):  
Billie Daniel ◽  
Barry Guitar
Keyword(s):  
Muscle Activity ◽  
Action Potentials ◽  
Substantial Improvement ◽  
Upper Lip ◽  
Lower Lip ◽  
Feedback Training ◽  
The Face ◽  
The Subject ◽  
The Right ◽  
Lifting Task

A case report is presented of an attempt to increase muscle activity during non-speech and speech activities through surface electromyographic feedback. The subject, a 25-year-old male, had a surgical anastomosis of the seventh cranial to the twelfth cranial nerve five years prior to the initiation of this therapy. The right side of the face was immobile. Frequency analogs of muscle action potentials from the right lower lip during pressing, retraction, eversion, and speech were presented to the subject. His task was to increase the frequency of the tone thereby increasing muscle activity. The subject made substantial improvement in the gestures listed above. Electrodes also were placed in various infraorbital positions for an upper lip lifting task. This gesture was unimproved. Pre- and posttherapy independence of facial gestures from conscious tongue contraction was found. Possible explanations were proposed for (1) increases of muscle activity in the lower lip, (2) lack of change of MAPs in the upper lip, (3) independence of the facial muscle activity from conscious tongue contraction, and (4) effectiveness of this feedback training.

scholarly journals Variations in soft facial tissue by using the interocclusal stabilization splint: 3d stereophotogrammetry

2015 ◽  
Vol 18 (4) ◽  
pp. 32
Author(s):  
Ana Maria Bettoni Rodrigues Da Silva ◽  
Laís Valencise Magri ◽  
Álvaro Augusto Junqueira Júnior ◽  
Mateus Sgobi Cazal ◽  
Marco Antônio Moreira Rodrigues Da Silva
Keyword(s):  
Temporomandibular Disorder ◽  
Reference Points ◽  
Facial Morphology ◽  
Upper Lip ◽  
3D Images ◽  
Stabilization Splint ◽  
Significant Difference ◽  
The Face ◽  
3D Stereophotogrammetry ◽  
The Times

<strong>Objective: </strong>To analyze variations in soft facial tissue by using the interocclusal stabilization splint (ISS) through the 3D stereophotogrammetry technique in a group of young women with temporomandibular disorder (TMD). <strong>Material and Methods: </strong>20 females between 20 and 60 years of age (39.3 ± 12.5) and TMD diagnosis based on the criteria of the RDC/TMD, received treatment with ISS. Reference points were marked on the face and photos were performed twice using the Vectra (M3–Canfield<sup>®</sup>): with and without ISS. In the 3D images the following variables were measured: area of the cheeks and lips (cm<sup>3</sup>), linear labial distances (Ls-Cph, Cph-Ch, Li-Ch, Ls-Li, Ch-Ch), lower third of the face (Sn-Me), height of the upper lip (Sn-Ls)/lower (Li-Me) and the angles C-Sn-Ls, N-Sn-Pg and Li-Sl-Pg. The data were analyzed in a descriptive manner, the times with and without ISS were compared using the t-test and the Pearson's correlation was employed in order to correlate the ISS thickness with the facial measurements (5% significance). <strong>Results: </strong>A statistically significant difference was found only for the variables of the lip area (p= 0.01) and Ls-Li (p=0.006) in comparison with/without ISS. No correlation was found between the ISS thickness and the lip area for both face sides, right (p=0.7; r=0.07) and left (p=0.9; r=-0.001). <strong>Conclusions: </strong>The use of interocclusal stabilization splint does not provide large changes in facial morphology, with the exception of the lip area and height.

Differential Organization of Touch and Pain in Human Primary Somatosensory Cortex

2000 ◽  
Vol 83 (3) ◽  
pp. 1770-1776 ◽  
Author(s):  
Markus Ploner ◽  
Frank Schmitz ◽  
Hans-Joachim Freund ◽  
Alfons Schnitzler
Keyword(s):  
Somatosensory Cortex ◽  
Pain Perception ◽  
Hierarchical Organization ◽  
Primary Somatosensory Cortex ◽  
Nociceptive Response ◽  
Tactile Stimuli ◽  
Somatosensory Cortices ◽  
Cortical Responses ◽  
Nociceptive Processing ◽  
Nociceptive Afferents

Processing of tactile stimuli within somatosensory cortices has been shown to be complex and hierarchically organized. However, the precise organization of nociceptive processing within these cortices has remained largely unknown. We used whole-head magnetoencephalography to directly compare cortical responses to stimulation of tactile and nociceptive afferents of the dorsum of the hand in humans. Within the primary somatosensory cortex (SI), nociceptive stimuli activated a single source whereas tactile stimuli activated two sequentially peaking sources. Along the postcentral gyrus, the nociceptive SI source was located 10 mm more medially than the early tactile SI response arising from cytoarchitectonical area 3b and corresponded spatially to the later tactile SI response. Considering a mediolateral location difference between the hand representations of cytoarchitectonical areas 3b and 1, the present results suggest generation of the single nociceptive response in area 1, whereas tactile stimuli activate sequentially peaking sources in areas 3b and 1. Thus nociceptive processing apparently does not share the complex and hierarchical organization of tactile processing subserving elaborated sensory capacities. This difference in the organization of both modalities may reflect that pain perception rather requires reactions to and avoidance of harmful stimuli than sophisticated sensory capacities.

Cortical mechanisms underlying tactile discrimination in the monkey. I. Role of primary somatosensory cortex in passive texture discrimination

1996 ◽  
Vol 76 (5) ◽  
pp. 3382-3403 ◽  
Author(s):  
F. Tremblay ◽  
S. A. Ageranioti-Belanger ◽  
C. E. Chapman
Keyword(s):  
Somatosensory Cortex ◽  
Contact Force ◽  
Discharge Rate ◽  
The Other ◽  
Primary Somatosensory Cortex ◽  
Spatial Period ◽  
Motor Speed ◽  
Texture Discrimination ◽  
Significant Difference ◽  
Area 3B

1. The discharge patterns of 359 single neurons in the hand representation of primary somatosensory cortex (SI) of two monkeys (Macaca mulatta) were recorded during the performance of a passive texture discrimination task with the contralateral hand (104 in area 3b, 149 in area 1, and 106 in area 2). Three nyloprint surfaces were mounted on a drum that was rotated under the digit tips. One surface was entirely smooth, whereas the other two were smooth over the first half and rough over the second half (smooth/ rough) (raised dots, 1 mm high and 1 mm diam, in a rectangular array; spatial period of 3 mm across the rows and columns for most recordings; 9 mm between columns for selected recordings). The monkeys were trained to distinguish between the smooth and smooth/rough surfaces. After the surface presentation, the monkey indicated the texture of the second half of the surface by pushing or pulling, respectively, on a lever with the other arm. For most recordings an average tangential speed of 49 mm/s was tested. For selected recordings motor speed was incremented (63, 75, or 89 mm/s). 2. Two hundred eighty-three neurons had a cutaneous receptive field (RF) on the hand (96 in area 3b, 120 in area 1, and 67 in area 2). Thirty-five neurons had a deep RF (4 in area 3b, 15 in area 1, and 16 in area 2). Seven neurons had mixed cutaneous and deep RFs (4 in area 1, 3 in area 2). Thirty-four neurons had no identifiable RF (4 in area 3b, 10 in area 1, and 20 in area 2). 3. The discharge of 185 of 359 neurons was significantly modulated during the presentation of one or both surfaces compared with the discharge at rest. Cells with a cutaneous RF that included part or all of the distal phalangeal pads of the digits used in the task (usually digits III and IV) were more likely to be modulated during surface presentation (132 of 179, 74%) than those with a cutaneous RF not in contact with the surfaces (24 of 104, 23%). The remaining neurons (mixed, deep, or no RF) were also infrequently modulated (29 of 76, 38%). 4. Of the 185 modulated units, 118 cells were classified as texture related because there was a significant difference in the discharge rate evoked by the smooth/rough and smooth surfaces. Cells with a cutaneous RF that included the digital pads in contact with the surfaces were frequently texture related (100 of 132, 76%). Texture sensitivity was less frequently observed in the remaining modulated neurons (18 of 53, 34%: cutaneous RF not in contact with the surfaces, deep RF, mixed cutaneous and deep RF, no identifiable RF). 5. Texture-related neurons were found in areas 3b, 1, and 2. Two patterns of texture-related responses were observed in the 100 cutaneous units with an RF in contact with the surfaces. Thirty-one units were classified as showing a phasic response at the time the digits encountered the leading edge of the rough half of the surface. Fifty-eight cells were classified as phasic-tonic (or sometimes tonic at the slowest motor speeds) because the response lasted for the duration of the presentation of the rough portion of the surface. The remaining 11 neurons could not be readily classified into one or the other category and, indeed, generally showed clear texture-related responses only at higher motor speeds (> 49 mm/s, 9 of 11). 6. Speed sensitivity was systematically evaluated in 41 of 100 texture-related units with a cutaneous RF in contact with the surfaces. The discharge of 66% of the units (27 of 41) varied significantly with the speed of surface presentation, with discharge increasing at higher speeds. Speed sensitivity was found in all three cytoarchitectonic areas (6 of 6 cells in area 3b, 11 of 22 in area 1, and 10 of 13 in area 2). 7. Contact force was also systematically monitored in these experiments (69 of 100 texture-related cells with a cutaneous RF in contact with the surfaces). Linear regression analyses indicated than 22% (15 of 69) of the texture-related units were sensitive to contact force (13

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