C A Gleason

Publications of C A Gleason

• Time dependent smooth muscle regeneration and maturation in a bladder acellular matrix graft: histological studies and in vivo functional evaluation.

  Authors: J Wefer, K D Sievert, N Schlote, A E Wefer, L Nunes, R Dahiya, C A Gleason, E A Tanagho

  The Journal of urology. 06/2001; 165(5):1755-9.

  PURPOSE: We evaluated the time dependence of smooth muscle regeneration and restoration of in vivo functional properties in bladder augmented with a bladder acellular matrix graft. MATERIALS ANDPURPOSE: We evaluated the time dependence of smooth muscle regeneration and restoration of in vivo functional properties in bladder augmented with a bladder acellular matrix graft. MATERIALS AND METHODS: A total of 45 Sprague-Dawley rats underwent augmentation cystoplasty with a bladder acellular matrix graft. Two rats each were sacrificed at various intervals within the first 21 days and 6 each were sacrificed at 4, 8 and 12 weeks. This second group underwent preoperative and postoperative assessment of bladder function, including cystometry, electrostimulation and stimulation with ice water, potassium and carbachol, as well as labeling of the bladder wall by the injection of fluorescent microspheres. After sacrifice slides of the bladders prepared for hematoxylin and eosin, trichrome, KI67, vimentin, desmin, smooth muscle specific alpha-actin and fluorescent microspheres were evaluated. RESULTS: Within 2 weeks the number of cells in the matrix as well as the proliferation index increased rapidly and then decreased gradually. Erythrocytes and inflammatory cells were found in the matrix within 2 to 4 days, followed by fibroblasts. A bladder host-to-matrix shift was evident by the appearance of microspheres in the matrix. Cell marker expression indicated the early appearance of vimentin and alpha-actin within the first 10 days. Distinct desmin expression was observed later, when the first smooth muscle cells were recognized. Functional evaluation revealed restored bladder function at 12 weeks. CONCLUSIONS: The time dependent increase of muscle cell markers during smooth muscle cell regeneration in a bladder acellular matrix graft is concordant with the progressive restoration of bladder function. These results may support the bladder acellular matrix graft concept for clinical application.

• Bladder acellular matrix graft: in vivo functional properties of the regenerated rat bladder.

  Authors: H J Piechota, C A Gleason, S E Dahms, R Dahiya, L S Nunes, T F Lue, E A Tanagho

  Urological research. 07/1999; 27(3):206-13.

  The purpose of this study was to determine whether the rat urinary bladder augmented by an acellular matrix graft can restore the bladder's low-pressure reservoir function and preserve normalThe purpose of this study was to determine whether the rat urinary bladder augmented by an acellular matrix graft can restore the bladder's low-pressure reservoir function and preserve normal micturition. After partial cystectomy (> 50%) and grafting with the bladder acellular matrix graft (BAMG), storage and voiding functions were monitored in 20 rats by means of a specially designed "micturition cage," leak-point cystography, and cystometry. After 4 months, sections (n = 6) were examined histologically to evaluate regeneration of bladder wall components within the BAMG. Bladder capacity and compliance increased progressively and were significantly higher in the grafted animals than in controls (partial cystectomy only), and volumes per void were significantly higher than in either control or normal animals. At 4 months, the regenerated urothelium, smooth muscle, blood vessels and nerves within the BAMG were qualitatively identical to normal bladder wall. Augmentation cystoplasty with the homologous BAMG leads to morphologic and functional rat bladder regeneration, thus enhancing low-pressure reservoir function and preserving normal micturition.

• Functional rat bladder regeneration through xenotransplantation of the bladder acellular matrix graft.

  Authors: H J Piechota, S E Dahms, M Probst, C A Gleason, L S Nunes, R Dahiya, T F Lue, E A Tanagho

  British journal of urology. 05/1998; 81(4):548-59.

  OBJECTIVE: To determine the decreased antigenicity of the bladder acellular matrix graft (BAMG) through xenotransplantation and to assess the in vivo and in vitro functional properties of the ratOBJECTIVE: To determine the decreased antigenicity of the bladder acellular matrix graft (BAMG) through xenotransplantation and to assess the in vivo and in vitro functional properties of the rat urinary bladder thus regenerated. MATERIALS AND METHODS: After partial cystectomy (> 50%), BAMGs prepared from hamster, rabbit and dog urinary bladders were grafted to male and female Sprague-Dawley rats; 10 control rats underwent partial cystectomy only. Urinary storage and voiding function were monitored in 15 animals using a specially designed 'micturition cage' and cystometry. After 4 months, organ-bath studies and histological techniques were used to evaluate bladder regeneration in vitro in the grafted animals. RESULTS: Clinically relevant antigenicity was not evident; no animal died from rejection and all bladder wall components regenerated in all BAMG xenografts. However, the degree and quality of regeneration varied. Muscularization, peak pressure, and bladder capacity were higher in the hamster BAMG-grafted animals, whereas in vitro contractility and compliance were best in the dog BAMG-regenerated bladders. All grafted bladders had significantly better capacity and compliance than the autoregenerated bladders after partial cystectomy alone. CONCLUSIONS: The present in vivo and in vitro studies show that BAMG-augmentation cystoplasty can lead to morphological and functional regeneration of the rat bladder, preserving its low-pressure reservoir function. Because BAMG-regenerated bladders show functional innervation that is similar to normal bladders, they can work in coordination with the host bladder components, thus generating adequate intravesical pressure to produce sustained voiding. The decreased antigenicity makes heterologous BAMG transplants feasible without immunosuppression.

• Bladder acellular matrix graft in rats: its neurophysiologic properties and mRNA expression of growth factors TGF-alpha and TGF-beta.

  Authors: S E Dahms, H J Piechota, R Dahiya, C A Gleason, M Hohenfellner, E A Tanagho

  Neurourology and urodynamics. 01/1998; 17(1):37-54.

  To assess the neurophysiologic properties and molecular mechanisms of the bladder acellular matrix graft (BAMG), we performed cystometric and neurophysiologic studies in male Sprague-Dawley rats (n =To assess the neurophysiologic properties and molecular mechanisms of the bladder acellular matrix graft (BAMG), we performed cystometric and neurophysiologic studies in male Sprague-Dawley rats (n = 46) at varying intervals. The animals were assigned to 3 groups: 1) normal, 2) partial cystectomy (>50%), and 3) partial cystectomy (>50%) and grafting with a BAMG of equal size. Additionally, matrix-grafted and host bladders were processed for analysis of mRNA expression of transforming growth factor (TGF)-alpha, TGF-beta1, TGF-beta2, and TGF-beta3 by reverse transcriptase polymerase chain reaction. Matrix-grafted bladders showed a significantly higher bladder capacity at 3 and 6 weeks and 4 months than those with partial cystectomy alone, and a significantly higher bladder capacity at 4 months than in normal controls (P < or = 0.01). Residual urine volume was significantly increased at 4 months. Electrostimulation of the pelvic nerve provoked generalized bladder contractions, a response that was reduced by atropine and hexamethonium. Variable induction of TGF-alpha, TGF-beta1, TGF-beta2, and TGF-beta3 gene transcription was evident in the BAMG, with prominent mRNA expression of TGF-alpha and TGF-beta1 6 months after surgery. These cystometric results and detrusor responses to stimulation provide further evidence that graft components do not interfere with host components. Matrix-grafted rat bladders generate, although not increased over time, adequate intravesical pressure responses to produce sustained voiding. Gene expression of different growth factors may be significant in understanding their role in the development and differentiation of the BAMG for partial bladder replacement.

• Neurostimulation for bladder evacuation: is sacral root stimulation a substitute for microstimulation?

  Authors: M Probst, H J Piechota, M Hohenfellner, C A Gleason, E A Tanagho

  British journal of urology. 05/1997; 79(4):554-66.

  OBJECTIVE: To determine by anatomical and functional studies whether stimulation of sacral rootlets might permit selective stimulation of autonomic fibres, thus avoiding the detrusor/sphincterOBJECTIVE: To determine by anatomical and functional studies whether stimulation of sacral rootlets might permit selective stimulation of autonomic fibres, thus avoiding the detrusor/sphincter dyssynergia characteristic of current techniques of neurostimulation for bladder evacuation. MATERIALS AND METHODS: In 10 male mongrel dogs, the S2 root was isolated and its constituent rootlets followed from their origin in the spinal cord to the point of exit from the dura. The entire root and the individual rootlets were then stimulated, including intra- and extra-dural stimulation and at proximal, mid and distal levels. RESULTS: Neuroanatomical and histological findings showed that rootlets of ventral S2 maintain their identity throughout their intradural course; some carry predominantly autonomic fibres, some predominantly somatic and some a mixture of the two. CONCLUSION: It appears surgically feasible to identify, isolate and sever the predominantly somatic rootlets intradurally, sparing the predominantly autonomic rootlets for inclusion in extradural electrode placement around the entire sacral root, thus eliminating sphincteric interference with detrusor contraction for voiding at low pressure.

• Reinnervation of the rat bladder with a somatic nerve and a striated muscle flap.

  Authors: M Hohenfellner, C A Gleason, L Nunes, P C Goldsmith, C A Malcamp, R A Schmidt, J W Thüroff, E A Tanagho

  The Journal of urology. 01/1996; 154(6):2164-9.

  PURPOSE: Current techniques of ventral sacral root stimulation to regain voluntary motor control of the decentralized urinary bladder depend upon intact parasympathetic innervation of the detrusor.PURPOSE: Current techniques of ventral sacral root stimulation to regain voluntary motor control of the decentralized urinary bladder depend upon intact parasympathetic innervation of the detrusor. We investigated techniques that might allow restoration of motor control of the bladder after efferent parasympathetic impairment. MATERIALS AND METHODS: In a chronic rat model, we evaluated whether motor control of a peripherally denervated bladder could be restored by transplantation of autologous excitable tissues and subsequent electrostimulation. Either a somatic nerve or a striated muscle flap was used as the transplant. RESULTS: Four months after the initial surgery, electrostimulation of the somatic nerve implant provoked bladder contractions--a response that was blocked by atropine. Stimulation of the nerve innervating the striated muscle flap also provoked bladder contractions; these were not affected by atropine and were slightly reduced by hexamethonium. CONCLUSION: Reinnervation of the bladder with somatic nerves or striated muscles is possible in principle. Future experiments will clarify the clinical significance of electrostimulation of such implants.

• Intraoperative electrostimulation of the cavernous nerve: technique, results and limitations.

  Authors: T F Lue, C A Gleason, G B Brock, P R Carroll, E A Tanagho

  The Journal of urology. 11/1995; 154(4):1426-8.

  PURPOSE: We studied the feasibility of inducing penile erection intraoperatively by stimulation of the cavernous nerves. MATERIALS AND METHODS: In 16 men undergoing retropubic radical prostatectomyPURPOSE: We studied the feasibility of inducing penile erection intraoperatively by stimulation of the cavernous nerves. MATERIALS AND METHODS: In 16 men undergoing retropubic radical prostatectomy and 6 undergoing penile surgery for venous leakage electrostimulation was applied to both sides of the prostatic apex (prostatectomy group) or the hilum of the penis (venous surgery group). RESULTS: Electrostimulation produced visible erection in 8 of the 16 prostatectomy patients and an increase in intracavernous pressure in 5 of the 6 venous surgery patients. CONCLUSIONS: Electrostimulation of the cavernous nerves intraoperatively to produce penile erection is feasible. However, the technique must be further refined to be clinically useful, that is to localize the neurovascular bundle in men undergoing prostatectomy.

• Recombinant human erythropoietin stimulates erythropoiesis and reduces erythrocyte transfusions in very low birth weight preterm infants.

  Authors: K M Shannon, J F Keith, W C Mentzer, R A Ehrenkranz, M S Brown, J A Widness, C A Gleason, E M Bifano, D D Millard, C B Davis

  Pediatrics. 02/1995; 95(1):1-8.

  DESIGN AND METHODS. We hypothesized that treatment with recombinant human erythropoietin (r-HuEPO) would stimulate erythropoiesis and would thereby reduce the need for erythrocyte transfusions inDESIGN AND METHODS. We hypothesized that treatment with recombinant human erythropoietin (r-HuEPO) would stimulate erythropoiesis and would thereby reduce the need for erythrocyte transfusions in preterm infants. We treated 157 preterm infants born at 26.9 +/- 1.6 weeks of gestation who weighed 924 +/- 183 g at birth with either subcutaneous r-HuEPO (100 U/kg/d, 5 days per week) or placebo for 6 weeks in a randomized, double-blind, controlled clinical trial. All patients received oral iron and were managed according to uniform conservative transfusion guidelines. RESULTS. Treatment with r-HuEPO was associated with fewer erythrocyte transfusions (1.1 +/- 1.5 per infant in the r-HuEPO group versus 1.6 +/- 1.7 per infant in the placebo group; P = .046) and with a reduction in the volume of packed erythrocytes transfused (16.5 +/- 23.0 mL versus 23.9 +/- 25.7 mL per infant; P = .023). Overall, 43% of the infants in the r-HuEPO group and 31% of placebo-treated infants were transfusion-free during the study (P = .18). The volume of blood removed for laboratory tests and the need for respiratory support at the start of treatment had major effects on transfusion requirements independent of r-HuEPO. Reticulocyte counts were higher during treatment in the r-HuEPO group (P = .0001), and r-HuEPO-treated infants had higher hematocrit values at the end of the study (32% versus 27.3% in the placebo group; P = .0001). We found no differences in the incidence of major complications of prematurity between the treatment groups. CONCLUSION. We conclude that treatment with r-HuEPO at a weekly dose of 500 U/kg stimulates erythropoiesis, moderates the course of anemia, is associated with a reduction in erythrocyte transfusions, and appears safe in very low birth weight preterm infants who are receiving iron supplements. Conservative transfusion criteria, minimization of phlebotomy losses, and treatment with r-HuEPO are complementary strategies to reduce erythrocyte transfusions in these infants.

• Laparoscopically implantable nerve-stimulating electrode (LINSE): application to the cavernous nerve in acute and chronic canine models.

  Authors: J S Wolf, G B Brock, C A Gleason, P Zvara, T F Lue, P R Carroll

  Journal of endourology / Endourological Society. 11/1994; 8(5):375-8.

  Using a new laparoscopic procedure, we investigated stimulation of the cavernous nerves to achieve erection in a canine model. The technique was developed during acute experiments in four dogs,Using a new laparoscopic procedure, we investigated stimulation of the cavernous nerves to achieve erection in a canine model. The technique was developed during acute experiments in four dogs, following which, chronic studies (4- to 6-weeks survival after surgery) were undertaken in three dogs. A monopolar cuff electrode was inserted laparoscopically by a transperitoneal approach and placed around the cavernous nerve. The leads were brought out to the subcutaneous space, where they were attached to stimulation receivers that could be activated by an external radiofrequency transmitter. An intracavernous pressure elevation indicative of successful stimulation was obtained acutely in five of eight cavernous nerves in the four acute-study dogs and in four of six nerves in the three chronic-study dogs. The implanted equipment associated with four of six cavernous nerves failed mechanically in the chronic-study animals, such that only two receiver-electrode sites were intact at the time of sacrifice 4 to 6 weeks later. Transmitter-driven stimulation of one of these two sets produced an intracavernous pressure rise above 100 cm H2O. We present this technique as part of the continuing evolution of laparoscopy as both a research and a clinical tool. The present use of the laparoscopically implantable nerve-stimulating electrode is a new animal research tool and a potential first step in the human application of the technology.

• The human locus coeruleus and anxiogenesis.

  Authors: B Libet, C A Gleason

  Brain research. 02/1994; 634(1):178-80.

  Electrical stimulation of locus coeruleus (LC), via permanently implanted electrodes with confirmed localization and effectiveness, did not elicit any subjective or behavioral manifestations ofElectrical stimulation of locus coeruleus (LC), via permanently implanted electrodes with confirmed localization and effectiveness, did not elicit any subjective or behavioral manifestations of anxiety. This is evidence against the hypothesis that LC is a mediator of anxiogenesis in man.

• The effect of magnetic resonance imagers on implanted neurostimulators.

  Authors: C A Gleason, N F Kaula, H Hricak, R A Schmidt, E A Tanagho

  Pacing and clinical electrophysiology : PACE. 02/1992; 15(1):81-94.

  This in-vitro study was designed to investigate the safety of various implanted neurostimulators in magnetic resonance (MR) imagers. The effects of the static and changing magnetic fields and theThis in-vitro study was designed to investigate the safety of various implanted neurostimulators in magnetic resonance (MR) imagers. The effects of the static and changing magnetic fields and the radio frequency (RF) electromagnetic field generated by 0.35 and 1.5 T MR imagers on the voltage output of four models of implantable passive neurostimulators and two models of implantable self-powered neurostimulators was studied. The neurostimulators were mounted on a support and placed in the imagers. An oscilloscope monitored the voltages at the outputs of the neurostimulators. For an Avery single-channel stimulator, located at the isocenter, the amplitude of the output pulses induced by the 0.35 T imager was 6V; from a 1.5 T imager, it was 12 V. These amplitudes can cause discomfort and possible harm to a patient if the typical therapeutic value is 1-5 V. The amplitude of the stimulator receiver's output decreased to relatively safe values beyond 40 cm from the isocenter. By contrast, there was no significant voltage output from the Medtronic SE-4 receiver. For two models of self-powered neurostimulators, the Medtronic Itrel and the Cordis MK II, the programmed stimulus parameters were not affected by the pulsed magnetic fields of the MR imagers. However, the RF fields at the isocenter heated the metal case of the stimulators. The rotational and linear forces produced by the fixed magnet on the Cordis MK II were judged to be too strong for a patient with this implant to be scanned. The study showed that patients with certain types of implanted neurostimulators can be scanned safely under certain conditions.

• Control of the transition from sensory detection to sensory awareness in man by the duration of a thalamic stimulus. The cerebral 'time-on' factor.

  Authors: B Libet, D K Pearl, D E Morledge, C A Gleason, Y Hosobuchi, N M Barbaro

  Brain : a journal of neurology. 09/1991; 114 ( Pt 4):1731-57.

  A 'time-on' theory to explain the cerebral distinction between conscious and unconscious mental functions proposes that a substantial minimum duration ('time-on') of appropriate neuronal activationsA 'time-on' theory to explain the cerebral distinction between conscious and unconscious mental functions proposes that a substantial minimum duration ('time-on') of appropriate neuronal activations up to about 0.5 s is required to elicit conscious sensory experience, but that durations distinctly below that minimum can mediate sensory detection without awareness. A direct experimental test of this proposal is reported here. Stimuli (72 pulses/s) above and below such minimum train durations (0-750 ms) were delivered to the ventrobasal thalamus via electrodes chronically implanted for the therapeutic control of intractable pain. Detection was measured by the subject's forced choice as to stimulus delivery in one of two intervals, regardless of any presence or absence of sensory awareness. Subjects also indicated their awareness level of any stimulus-induced sensation in each and every trial. The results show (1) that detection (correct greater than 50%) occurred even with stimulus durations too brief to elicit awareness, and (2) that to move from mere detection to even an uncertain and often questionable sensory awareness required a significantly larger additional duration of pulses. Thus simply increasing duration ('time-on') of the same repetitive inputs to cerebral cortex can convert an unconscious cognitive mental function (detection without awareness) to a conscious one (detection with awareness).

• Stimulation of locus coeruleus in man. Preliminary trials for spasticity and epilepsy.

  Authors: B Feinstein, C A Gleason, B Libet

  Stereotactic and functional neurosurgery. 02/1989; 52(1):26-41.

  Stimulating electrodes were chronically implanted unilaterally (in 1975-1977) in the vicinity of the locus coeruleus (LC) in three patients, one with cerebral palsy-spastic quadriplegia, two withStimulating electrodes were chronically implanted unilaterally (in 1975-1977) in the vicinity of the locus coeruleus (LC) in three patients, one with cerebral palsy-spastic quadriplegia, two with epilepsy (one grand mal, one psychomotor). Effective excitation of efferent LC axons was indicated by measuring rises in 3-methoxy-4-hydroxyphenylethyleneglycol in the jugular and systemic venous blood following a 6-min stimulus with discontinuous bursts of pulses. There was a substantial reduction of spasticity during and after stimulation. Improvement was verified by double-blind failures of the stimulator, and the stimulus therapy is still in use after 9 years. There appeared to be a reduction in incidence and severity of both types of epileptic seizures, although this was not rigorously established. The patient with psychomotor epilepsy reported a considerable lengthening of preseizure auras (to 15-30 min), an unusual number of which terminated without a seizure.

• Indomethacin and patent ductus arteriosus: effects on renal function in preterm lambs.

  Authors: C A Gleason, R I Clyman, M A Heymann, F Mauray, R Leake, C Roman

  The American journal of physiology. 02/1988; 254(1 Pt 2):F38-44.

  To examine the independent effects of a patent ductus arteriosus and of indomethacin therapy on the renal function of the preterm newborn, we created a preterm lamb model in which ductus diameterTo examine the independent effects of a patent ductus arteriosus and of indomethacin therapy on the renal function of the preterm newborn, we created a preterm lamb model in which ductus diameter could be regulated. We studied 24 preterm newborn lambs. Eight lambs (group 1) had their ductus closed at delivery and received no indomethacin. Eight lambs (group 2) had their ductus closed and then received indomethacin (0.3 mg/kg) at 5.5 h; eight lambs (group 3) had their ductus kept open and then received indomethacin at 5.5 h. Hemodynamic and renal function measurements were made at 5 h (pretreatment) and at 12.5 h. In group 2 lambs there was a significant reduction in inulin clearance (GFR) and osmolal clearance after indomethacin. In contrast, lambs with an open ductus (group 3), when compared with lambs with a closed ductus (groups 1 and 2) at 5 h, already had significantly decreased blood pressure, GFR, urine volume, and osmolal clearance. Following indomethacin treatment, group 3 lambs showed no further decrease in renal function. We suggest that in preterm lambs with patent ductus, the apparent lack of renal dysfunction following indomethacin treatment reflects underlying diminished renal function.

• Preparation- or intention-to-act, in relation to pre-event potentials recorded at the vertex.

  Authors: B Libet, E W Wright, C A Gleason

  Electroencephalography and clinical neurophysiology. 11/1983; 56(4):367-72.

  Pre-event potentials were compared in the same subject, for 3 types of forewarned events, in which the foreperiod for orienting or attention began several seconds before the event. All of thesePre-event potentials were compared in the same subject, for 3 types of forewarned events, in which the foreperiod for orienting or attention began several seconds before the event. All of these trials involved similar non-motor components (expectancy, attentiveness, general orienting to a salient stimulus) but differed in whether motor or non-motor responses were required. A prominent and consistent slow negative shift preceded the pre-set time for a motor response, even when the subject 'vetoed' his intention to act shortly before the pre-set time. Pre-event potentials were absent, or small and brief, when the event was a task-related skin stimulus not involving preparation to move. The findings selectively support the view that mental preparation/intention to act is a necessary and perhaps dominant process associated with the vertex-recorded pre-event, slow negative potential. They also show that such a pre-event potential can appear even when the subject knows he is going to veto his developing intention to act and does not actually move.

• Time of conscious intention to act in relation to onset of cerebral activity (readiness-potential). The unconscious initiation of a freely voluntary act.

  Authors: B Libet, C A Gleason, E W Wright, D K Pearl

  Brain : a journal of neurology. 10/1983; 106 (Pt 3):623-42.

  The recordable cerebral activity (readiness-potential, RP) that precedes a freely voluntary, fully endogenous motor act was directly compared with the reportable time (W) for appearance of theThe recordable cerebral activity (readiness-potential, RP) that precedes a freely voluntary, fully endogenous motor act was directly compared with the reportable time (W) for appearance of the subjective experience of 'wanting' or intending to act. The onset of cerebral activity clearly preceded by at least several hundred milliseconds the reported time of conscious intention to act. This relationship held even for those series (with 'type II' RPs) in which subjects reported that all of the 40 self-initiated movements in the series appeared 'spontaneously' and capriciously. Data were obtained in at least 6 different experimental sessions with each of 5 subjects. In series with type II RPs, onset of the main negative shift in each RP preceded the corresponding mean W value by an average of about 350 ms, and by a minimum of about 150 ms. In series with type I RPs, in which an experience of preplanning occurred in some of the 40 self-initiated acts, onset of RP preceded W by an average of about 800 ms (or by 500 ms, taking onset of RP at 90 per cent of its area). Reports of W time depended upon the subject's recall of the spatial 'clock-position' of a revolving spot at the time of his initial awareness of wanting or intending to move. Two different modes of recall produced similar values. Subjects distinguished awareness of wanting to move (W) from awareness of actually moving (M). W times were consistently and substantially negative to, in advance of, mean times reported for M and also those for S, the sensation elicited by a task-related skin stimulus delivered at irregular times that were unknown to the subject. It is concluded that cerebral initiation of a spontaneous, freely voluntary act can begin unconsciously, that is, before there is any (at least recallable) subjective awareness that a 'decision' to act has already been initiated cerebrally. This introduces certain constraints on the potentiality for conscious initiation and control of voluntary acts.

• Readiness-potentials preceding unrestricted 'spontaneous' vs. pre-planned voluntary acts.

  Authors: B Libet, E W Wright, C A Gleason

  Electroencephalography and clinical neurophysiology. 10/1982; 54(3):322-35.

  The nature of readiness-potentials (RPs) that may be associated with fully endogenous, 'freely' voluntary acts was investigated. Restriction on when to act were eliminated and instructions fosteredThe nature of readiness-potentials (RPs) that may be associated with fully endogenous, 'freely' voluntary acts was investigated. Restriction on when to act were eliminated and instructions fostered 'spontaneity.' The 'self-initiated' RPs exhibited in these conditions were categorizable into two (possibly three) types, all of which could be exhibited by the same subject. Type I had an early onset at about -1050 +/- 175 msec and a long ramp-like form, resembling self-paced RPs. In type II the main negative shift began at about -575 +/- 150 msec, and at about -240 +/- 50 msec in type III. Type II partially resembled the similarly timed NS' component in self-paced RPs. For acts produced at known, preset times, in which freedom of choice was eliminated but planning to act was required, RPs resembled self-initiated type I RPs and self-paced RPs. All RPs were maximal at the vertex, especially type II even though it was also bilaterally asymmetrical. These distributions suggest that cortical areas other than area 4 and 6 contribute importantly, especially to type II. All RPs, whether in self-initiated or pre-planned acts, appear related specifically to preparation for a motor action. When task-related skin stimuli replaced self-initiated movements, under similar conditions of attentiveness (and expectancy), there were either no or relatively small event-preceding-slow potential shifts. All post-stimulus P300 waves were very large. Two volitional processes are postulated: process I is associated with development of pre-planning or preparation to act in the near future (seconds), whether voluntary choice is present (type I RPs) or absent (pre-set RPs); process II, with an onset at roughly 0.5 sec before the act, is associated more uniquely with voluntary choice and with the more specific as well as endogenous urge or intention to act; it can be present in the comparative absence of or in sequence and overlapping with process I.

• CT-directed stereotactic surgery in the management of brain abscess.

  Authors: B L Wise, C A Gleason

  Annals of neurology. 12/1979; 6(5):457.

• Suppression of an eplieptiform type of electrocortical activity in the rat by stimulation in the vicinity of locus coeruleus.

  Authors: B Libet, C A Gleason, E W Wright, B Feinstein

  Epilepsia. 01/1978; 18(4):451-62.

  Stimulation of the locus coeruleus, or in the vicinity of this nucleus or of its ascending tracts, could markedly suppress the appearance of epileptiform-like ECoG bursts. The latter were induced inStimulation of the locus coeruleus, or in the vicinity of this nucleus or of its ascending tracts, could markedly suppress the appearance of epileptiform-like ECoG bursts. The latter were induced in rats by a subconvulsive dose of pentylenetetrazol. Electrode sites were identified histologically. A unilateral stimulus suppressed bursts bilaterally. An individual burst already in progress could be aborted, stopping within less than 0.5-1 sec after onset of a stimulus train. The antiepileptiform actions occurred with no evidence of any desynchronizing effect of the stimulus on the resting ECoG; they appear to be different in sites of origin and nature from those reported for stimulation of the reticular activating system. It is proposed that stimulation of the ascending noradrenergic system in the brain stem may limit the development and spread of hyperexcitatory, epileptiform states.

• Computer-aided localization techniques for stereotaxic surgery.

  Authors: E Colloff, C A Gleason, W W Alberts, E W Wright

  Confinia neurologica. 02/1973; 35(2):65-80.