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C J Vierck

Publications and source records attributed to C J Vierck.

At least 55 records · Page 3Linked to original sources
PubMed1988

Neural mechanisms of absolute tactile localization in monkeys.

Macaca nemestrina monkeys were trained to indicate the location of suprathreshold tactile stimuli delivered to the glabrous skin of either foot. The testing paradigm involved self-initiated trials (a bar press), followed by 10-Hz stimulation at one of six locations (e.g., on the distal phalanx of the second toe on the left foot), providing the opportunity for the animal to press one of six buttons located on a facing panel. The buttons were positioned on a picture of a monkey's feet at locations corresponding to the skin loci that were stimulated on different trials. If the animal first pressed the button corresponding to the position stimulated, liquid reward was delivered; responses to any other button terminated stimulation without reward, requiring initiation of another trial for the opportunity to receive reinforcement. The localization errors for normal monkeys were reliably greater along the mediolateral dimension of the foot than they were proximodistally. For example, stimulation of the tip of toe 4 elicited responses to the button at the tip of toe 2 on 25% of the trials, as compared with only 10% errors between the tip of toe 4 and the pad at the base of toe 4. Following unilateral interruption of the dorsal spinal columns at an upper thoracic level, the capacity for absolute tactile localization was unchanged over months of testing. The greater localization accuracy along the proximodistal axis of the foot remained after dorsal column transection. In order to evaluate neural substrates of localization by monkeys, single-neuron receptive field (RF) sizes and distributions within the first somatosensory (SI) cortex were examined to determine the overlap or separation of the representations of different points on glabrous skin. The sample of neurons that provided the RF data was obtained in previous investigations of unanesthetized, neuromuscularly blocked Macaca fascicularis monkeys. Analysis of RF overlap revealed that greater than 50% of cytoarchitectural area 1 units that responded to stimulation of one digit tip also responded to another digit or to the pad at the base of a digit. These large RFs seem poorly suited to subserve a high degree of spatial localization and are compatible with the frequent localization errors by the monkeys in the behavioral experiments. However, the area 1 RF data do not explain the tendency of these animals to exhibit better localization accuracy along the proximodistal axis than along the mediolateral axis of the volar foot.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Sensitivity to painful and nonpainful electrocutaneous stimuli in monkeys: effects of anterolateral chordotomy.

Four Macaca nemestrina monkeys were trained to pull a manipulandum to escape electrocutaneous stimulation (ES) applied to either leg. The intensities of stimulation which the monkeys chose to escape were those that humans identify as painful. The duration of escape trials was inversely related to stimulus intensity, and the force of escape responses was directly related to ES intensity. Reflexive responses were elicited by stimulus intensities below and above the escape threshold, and the force of the flexion reflexes was a negatively accelerating function of stimulus magnitude. The monkeys were also trained to respond, for water reinforcement, to cued, low-intensity ES. The stimulus intensities detected for water reinforcement were 50-100 X less than the escape thresholds. Following unilateral, anterolateral chordotomy, all monkeys demonstrated a large reduction in percentage of escape responding to stimulation of the contralateral leg. When the animals did escape contralateral stimulation, the latencies to respond were longer than preoperatively. The percentage and latency of escape responses to stimulation of the ipsilateral leg were not changed following chordotomy. Despite the depression of contralateral pain reactivity, the animals continued to respond to low levels of stimulation on the detection task, demonstrating that anterolateral chordotomy reduced the painfulness of strong stimulation without eliminating sensibility for low levels of stimulation. However, postoperative detection thresholds were consistently higher contralaterally than ipsilaterally. This effect resulted from slight contralateral decreases and significant ipsilateral increases in sensitivity to low levels of ES (relative to preoperative values). Thus, contralateral axons in the anterolateral column contribute to detection of light cutaneous stimulation, and chordotomy appears to disinhibit inputs from large myelinated afferent fibers to ipsilateral neurons in the spinal gray matter caudal to the lesion. The strictly contralateral slowing and reduction in percentage of pain reactivity by chordotomy correlated with reports from human patients. However, reflexive measures did not suffice as indicants of pain sensitivity. The chordotomies produced bilateral attenuations of reflexive amplitudes. Also, the force of operant escape responses was reduced with stimulation of either side. Thus, the disfacilitation of motoric reactions extended both rostral and caudal to the spinal lesions that interrupted propriospinal axons in the vicinity of the ventral horns.

Animals↗
PubMed1985

Effects of spinal lesions on temporal resolution of cutaneous sensations.

In order to test the possibility that the dorsal columns (DCs) contribute to temporal resolution of tactile stimuli, Macaca speciosa monkeys were trained to discriminate different frequencies of stimulation delivered to the glabrous surface of the left foot. Brief (11-msec) pulses of 550-micron indentation from the skin surface were presented for 1 sec at a standard rate of 10 pulses per second (pps), and subsequent trains of the same duration either were replications of the standard or consisted of a higher (comparison) frequency of up to 35 pps. Correct performance consisted of a lever press in response to the comparison stimulus when it occurred as the second or third train in a trial. Signal detection analysis of response tendencies in the second stimulus interval revealed difference threshold values of 2.8 pps, on the average, for 75% correct responding. Transections of the ipsilateral dorsolateral column or the contralateral anterolateral column or both did not significantly affect discrimination of the frequency of cutaneous stimulation. However, following interruption of the ipsilateral DC, two monkeys could not discriminate 10 from 35 pps throughout testing for more than 1 year. These results contrast with a preservation of spatiotactile resolution that has been demonstrated repeatedly for animals following lesions of the DCs or the lateral columns, indicating that a unique function of the DC pathway relates to temporal coding.

Afferent Pathways↗
PubMed1983

Effects of spinal tractotomy on spatial sequence recognition in macaques.

Five Macaca speciosa monkeys were trained to discriminate between the order of two tactile stimulus presentations (proximal-distal vs. distal-proximal) to the lateral calf. Psychophysical thresholds for tactile sequence recognition were obtained by varying the distance between the spots stimulated. Stabilized preoperative thresholds for stimulation on the lateral calf averaged 10.4 mm, which is comparable to point localization thresholds for sequential contact of the proximal limbs of humans. Complete interruption of the ipsilateral fasciculus gracilis produced elevations of thresholds within the first 3 postoperative weeks to an average of 3.6 times the control values. With training over 6 postoperative months, normal discrimination recovered. In contrast to the effects of dorsal column (DC) lesions, interruption of the lateral and ventral columns ipsilaterally or contralaterally produced no deficit or a mild and transient deficit. Monkeys with isolation of either the ipsilateral dorsolateral column (ILC) or the contralateral ventral quadrant (CVQ) exhibited substantial and enduring deficits. Thresholds were elevated an average of 5 times the control values, and recovery was not observed or was incomplete after months of training. In contrast, isolation of the ipsilateral dorsal column produced little or no threshold elevation. The results of isolating lesions complement the series of primary lesions to each cord sector, showing that spatiotactile sequence recognition for the hindlimb is served more critically by the dorsal columns than by the lateral columns.

Animals↗
PubMed1979

Loss and recovery of reactivity to noxious stimuli in monkeys with primary spinothalamic cordotomies, followed by secondary and tertiary lesions of other cord sectors.

Cebus albifrons monkeys were trained to escape electrical stimulation of either leg at five intensities, spanning a range from mild tingle to intense but tolerable pain, as judged by human observers who experienced the same stimuli. The average duration of stimulation received by the animals at each intensity was plotted for each leg during the period required for recovery of responsiveness to noxious electrical stimulation following ventrolateral spinal cordotomy. Recovery of escape responding was observed similarly following subsequent lesions to the spinal cord, in an attempt to define the pathways that subserve pain conduction after readjustment from cordotomies that produced substantial deficits of escape behaviour. The most enduring elevations of duration of stimulation by lesion I (left cordotomy) were produced by lesions that involved all of the ventrolateral column and most or all of one or both ventral columns. Secondary lesions of the dorsal columns, Lissauer's tract and the dorsolateral columns, in various combinations, did not produce long-term effects on escape responding. In contrast, a complete ventral hemisection produced a pronounced bilateral deficit that did not recover fully over three hundred and five post-operative days. The major conclusions are: (1) that the dorsal pathways do not play a major role in the rostral conduction of information critical for pain perception in monkeys, even though these pathways receive input from high threshold receptors; and (2) in order to produce a lasting decrease of pain sensitivity in primates by spinal surgery, the lesion must be bilateral and must involve both the ventrolateral and ventral columns.

Animals↗
PubMed1978

Comparison of forelimb and hindlimb motor deficits following dorsal column section in monkeys.

Macaca speciosa monkeys were trained to acquire food reinforcement with motor responses that were defined by 4 different tasks. The effects of dorsal column lesions on the speed of these responses were compared for the forelimbs vs. the hindlimbs. Enduring impairments were not seen for any limb when the animal was required to accurately project a limb to different points in space, even with exclusion of visual guidance and with random variation of the start and stop points for each movement. Similarly, when the task required that the animals emit rapid response sequences, the forelimbs were impaired temporarily, but no long-term deficits were seen for the forelimbs or the hindlimbs. Although these impositions of spatial and temporal demands did not reveal striking disruptions of whole-limb movements, hindlimb grasp responses were shown to be impaired over long periods of postoperative testing. This corroborates previous findings for the forelimb and indicates that facility of distal extremity movement depends crucially on dorsal column-lemniscal input.

Animals↗
PubMed1977

Absolute and differential sensitivities to touch stimuli after spinal cord lesions in monkeys.

Concurrent two-choice and go--no-go procedures were used to measure difference thresholds (DLs) for discrimination of touch intensities and absolute thresholds (RLs) for detection of light tactile stimuli by Macaca speciosa monkeys. Consistent with the classical proposition that the spinothalamic tracts of primates contain sufficient tactile input to support simple recognition of light skin contact, RLs were not affected by lesions of the ipsilateral dorsal column or by subsequent section of the ipsilateral dorsolateral column. There was, however, a clear dissociation of the effects of the spinal lesions on the absolute and difference thresholds. DLs were elevated ipsilaterally by lesions of the dorsal column and, after long periods of postoperative testing (more than 6 months), the DLs returned to postoperative levels. Subsequent interruption of the dorsolateral column again elevated DLs ipsilaterally and with extensive testing DLs again returned to preoperative levels.

Animals↗
PubMed1975

Attenuation of pain reactivity by caudate nucleus stimulation in monkeys.

The effect of caudate nucleus stimulation on reactivity to painful stimuli was investigated in Macaca speciosa monkeys chronically implanted with electrodes in the right caudate nucleus. The force with which subjects escaped from electrocutaneous leg shock was used as a measure of pain reactivity and was decreased by caudate stimulation. Escape threshold and latencies were not influenced by the brain stimulation. Decreased escape force was obtained only when 50 msec trains of caudate stimulation preceded 20 msec trains of leg shock by 0-100 msec. Pain reactivity was not affected if brain stimulation followed leg shock or if leg shock followed brain stimulation by more than 100 msec. Intershock response distributions indcated that direct motor inhibition was not responsible for the depression of escape force, and the effectiveness of a restricted range of caudate-leg stimulation intervals ruled out generalized effects on arousal. The results indicate that the effect of caudate stimulation is to reduce the affective components of pain elicited by noxious electrocutaneous stimuli. The time course of this caudate effect parallels that previously reported for the caudate-induced depression of evoked activity in the non-specific somatosensory projections of the reticular formation and thalamus.

Animals↗
PubMed1973

Behavioral assessment of pain detection and tolerance in monkeys.

Cebus albifrons monkeys received electrical stimulation of the hindlimbs over a wide range of intensities. On trials signalled by a blue light, the animals were permitted to escape shock by pressing a disc, or shock was terminated after 8 sec (free escape). Escape force (disc pressure) was found to increase as stimulation intensity increased well beyond escape threshold, while shock duration curves reached plateau at the mid-range of intensities. The shock duration curves generated by free escape responses should be comparable to pain detection functions obtained by similar operations in humans, and the curves were stable over months of testing, as is generally found in pain-detection studies. On trials signalled by a red light, the animals received intense tail shock immediately after escape responses (punished escape), or, if they endured leg shock for 8 sec without escaping, then they could avoid tail shock with a panel press. The shock duration curves generated by punished escape responses should be comparable to pain tolerance functions as defined for human subjects, and the escape thresholds were considerably higher on red-light trials. As in human studies, the tolerance curves were not stable over repeated testing sessions, and some feature of the paradigm forced a progression toward extremely high levels of tolerance.

Animals↗