Extraction of all coefficients of coupled-mode equations for natural, single-phase, unidirectional SAW transducers from dispersion characteristics computed by hybrid finite element method

A numerical method is presented for determining all of the coefficients of coupled-mode equations for natural, single-phase, unidirectional SAW transducers (NSP-UDTs). Substituting numerical results computed by the hybrid finite element method for infinite NSPUDTs with shorted and open electric ports into several relations derived from the coupled-mode theory, we can determine all of the coefficients. Specifically, the edge frequencies of a stop-band and the static capacitances yield the self-coupling coefficients and the amplitudes of mutual-coupling and transduction coefficients, and the electric potential standing wave on the substrate surface, which can be derived from the projection of the standing wave distributions of particle displacements and electric potential in the whole substrate onto the set of those predicted by the coupled-mode theory, yields the phases of mutual-coupling and transduction coefficients. NSPUDTs on ST-25 degrees X quartz, Y-51.25 degrees Z LiTaO3, and 50 degrees Y-25 degrees X La3Ga5SiO14 substrates are investigated. Our results agree well with the earlier experimental ones.

Free tensor fasciae latae perforator flap for the reconstruction of defects in the extremities

In the three cases presented in this study, free tensor fasciae latae perforator flaps were used successfully for the coverage of defects in the extremities. This flap has no muscle component and is nourished by muscle perforators of the transverse branch of the lateral circumflex femoral system. The area of skin that can by nourished by these perforators is larger than 15 x 12 cm. The advantages of this flap include minimal donor-site morbidity, the preservation of motor function of the tensor fasciae latae muscle and fascia lata, the ability to thin the flap by removing excess fatty tissue, and a donor scar that can be concealed. In cases that involve transection of the perforator above the deep fascia, the operation can be completed in a very short period of time. This flap is especially suitable as a free flap for young women and children who have scars in the proximal region of the lateral thigh or groin region that were caused by split-thickness skin grafting or full-thickness skin grafting during previous operations.

Free medial plantar perforator flaps for the resurfacing of finger and foot defects

In this article, three cases in which free medial plantar perforator flaps were successfully transferred for coverage of soft-tissue defects in the fingers and foot are described. This perforator flap has no fascial component and is nourished only by perforators of the medial plantar vessel and a cutaneous vein or with a small segment of the medial plantar vessel. The advantages of this flap are minimal donor-site morbidity, minimal damage to both the posterior tibial and medial plantar systems, no need for deep dissection, the ability to thin the flap by primary removal of excess fatty tissue, the use of a large cutaneous vein as a venous drainage system, a good color and texture match for finger pulp repair, short time for flap elevation, possible application as a flow-through flap, and a concealed donor scar.

One-stage facial augmentation with an intraoral groin adipose flap transfer

A free groin adipose flap using an intraoral approach was used to correct facial contour deformities instead of a groin dermis-fat flap. The major disadvantages of the latter flap are that multistage debulking procedures are required and there are wide postoperative donor scars because of the wide skin portion included in the flap. To overcome these weaknesses the authors developed a free groin, customized ("berry picked") adipose flap, which was transferred by an intraoral approach for reconstruction of congenital hemifacial (orbitozygomatic) hypoplasia. The advantages of this method include one-stage augmentation without secondary defatting, no skin grafting of the donor defect, a donor scar in a concealed area, and possible transfer through an intraoral approach that results in minimal invasive surgery with no scar at the graft site.

Combined submental flap with toe web for reconstruction of the lip with oral commissure

We present a new method employing a combined submental island flap and dorsalis pedis flap with the first toe web for reconstruction of a large lip defect including the oral commissure. The advantages of this method are: there is an excellent colour match; an anatomical structure similar to that of the oral commissure produces excellent results; there is superb function of the oral commissure; a donor-scar deformity can be avoided, since both flaps come from concealed areas; and good lining by the thin dorsal skin of the foot and submental skin results in a single-stage operation. The disadvantages are that complicated microvascular anastomoses may be required and there is a possibility of venous congestion of the submental flap in cases with a hypoplastic venous system. The use of the anterior jugular vein within the flap may be a key to overcoming this problem.

Application of the RealAudio package to computerized medical lectures

We created a multimedia system to computerize past lectures using RealAudio software. Physicians, medical researchers and students can browse the contents of lecture slides and handouts with synchronous audio using the Internet. The audience can easily review the most interesting parts of lectures and medical students can listen to complete medical lectures from remote sites with narration and slide depiction, whenever convenient. We have created three multimedia programs; the memorial lecture of a professor's retirement, a new method of hand washing for surgical procedures and a lecture on medical informatics. The cost of this system and the results of the evaluation by medical students are described. The ease of using this application makes it a potentially valuable tool for clinicians and researchers.

Supermicrosurgical lymphaticovenular anastomosis for the treatment of lymphedema in the upper extremities

Over the last eight years, the authors analyzed obstructive lymphedema of a unilateral upper extremity in a total of 27 females, comparing the use of supramicrosurgical lymphaticovenule anastomoses and/or conservative treatment. The most common cause of edema was mastectomy, with or without subsequent radiation therapy for breast cancer. As an objective assessment of the extent of edema, the circumferences of the affected and opposite normal forearms were measured at 10 cm below the olecranon of the arm. Twelve of these patients received continual bandaging. In these patients, the average excess circumference of the affected arm was 6.4 cm over that of the normal forearm; the average duration of edema before treatment was 3.5 years; the average period for conservative treatment was 10.6 months; and the average decrease in circumference was 0.8 cm (11.7 percent of the preoperative excess). Twelve patients underwent surgery and postoperative continual bandaging. In these patients, the average excess circumference was 8.9 cm; the average duration of edema before surgery was 8.2 years; the average follow-up after surgery was 2.2 years; and the average decrease in circumference was 4.1 cm (47.3 percent of the preoperative excess). These results indicated that supermicrolymphaticovenular anastomoses with postoperative bandaging have a valuable place in the treatment of obstructive lymphedema.

Deep inferior epigastric perforator dermal-fat or adiposal flap for correction of craniofacial contour deformities

Craniofacial contour deformities are difficult to reconstruct. This article summarizes the authors' use of deep inferior epigastric perforator dermal-fat or adiposal flaps in eight patients with such deformities. Of these patients, three had traumatic craniofacial or facial deformities, one had congenital craniofacial deformity, two had hemifacial atrophy (one because of radiation), one had hemifacial microsomia, and one had localized frontonasal lipodystrophy. Stable restoration of the facial contour was achieved in all eight patients. The advantages of this flap are numerous. It has minimal donor-site morbidity, because the rectus abdominis muscle is preserved as a whole, and it accommodates pregnancy in female patients. Simultaneous elevation of this flap during preparation of the recipient site makes it possible to complete surgery in a shorter time than with the scapular flap. Furthermore, a considerable amount of the superficial or deep fatty layer can be removed primarily, making a bulky flap into a thinner one. This flap also allows the use of a large transverse abdominal ellipse of skin, fat, and Scarpa's fascia with abdominoplasty closure. Conversely, it requires a technically difficult dissection of the muscle perforator and skin grafting of donor defects in patients with a large dermal-fat flap. Also, additional minor operations may be necessary to reduce fat volume around the perforator. Ultimately, the deep inferior epigastric perforator adiposal flap seems to be suitable for craniofacial contouring surgery. It is especially indicated for use in children and female patients who are expecting to have children.

New microsurgical breast reconstruction using free paraumbilical perforator adiposal flaps

Pedicled transverse rectus abdominis musculocutaneous (TRAM) flaps have generally been used for bilateral breast losses. The major disadvantages of this method are the total or partial loss of the rectus abdominis muscles and various resulting postoperative complications, such as abdominal bulging and lumbar pain. With the recent development of perforator flaps and supermicrosurgery with anastomosis of 0.5-mm caliber vessels, these serious complications can be overcome with a paraumbilical perforator adiposal flap, without sacrificing the rectus abdominis muscle. The breasts of a 57-year-old woman who had undergone a bilateral subcutaneous mastectomy, including silicone prostheses, were repaired simultaneously with this new method using free paraumbilical perforator adiposal flaps. This new method of breast augmentation with a vascularized adiposal flap and without any muscle component is minimally invasive; its advantages are the preservation of the rectus abdominis muscles and the short time elevation for the adiposal flap.

Fingertip reconstructions using partial-toe transfers

Fifty-six partial toes were transferred to reconstruct fingertip deficits. The transfers from the big toe mainly consisted of 3 trimmed big toetips, 3 vascularized nail grafts, 3 onychocutaneous flaps, 19 thin osteo-onychocutaneous flaps, and 2 hemipulp flaps. The transfers from the second toe mainly consisted of 8 trimmed second toetips, 5 reduced second toes, and 9 whole distal phalanges. The average values of postoperative sensory recovery of the osteo-onychocutaneous flaps including the vascularized nail grafts were 3.1 (Semmes-Weinstein test) and 6.3 mm (moving two-point discrimination) at 2.6 years after the transfer; those of the thin osteo-onychocutaneous flaps were 3.1 and 7.2 mm at 2.0 years after surgery; those of the trimmed big toe tip transfers were 3.61 and 6.5 mm at 1.8 years after surgery; and those of the trimmed second toetip transfers were 3.37 and 6.3 mm at 2.6 years after transfer. Those of the distal phalanx of the second toe were 3.41 and 7.9 mm at 1.2 years after surgery, and those of the reduced second toe were 3.2 and 6.7 mm at 10.6 months after surgery.

[Supramicrosurgical lymphaticovenular anastomosis for the treatment of lymphedema in the extremities]

During the past eight years, we treated obstructive lymphedema of a unilateral upper extremity in 27 females and of a unilateral or bilateral lower extremity in 35 males and females with supramicrosurgical lymphaticovenular anastomoses and/or conservative treatment. The most common cause of upper limb edema was mastectomy with or without subsequent radiation therapy for breast cancer, and that of lower limb edema was hysterectomy with radiation. As an objective assessment of edema, the circumferences of the affected and opposite normal forearms or lower legs were measured 10 cm below the olecranon of the arm or the lower border of the patella. In patients who received conservative treatment (12 arms and 12 legs), the average excess circumferential length of the affected arm and leg was 6.4 and 7.1 cm over that of normal extremities, average duration of edema before treatment was 3.5 and 5.2 years, average period for conservative treatment was 10.6 months and 1.5 years, and average decreased circumferential length was 0.8 and 0.6 cm, respectively. The rate of circumferential decrease over 4 cm was none in arm and 16.7% in leg edema. In patients who underwent surgery (12 arms and 16 legs), the average excess circumferencial length was 8.9 and 9.8 cm, average duration of edema before surgery was 8.2 and 8.9 years, average follow-up after surgery was 2.2 and 3.3 years, and average decrease in excess circumference was 4.1 and 2.7 cm, respectively. The rate of circumferential decrease over 4 cm was 58.3% in arms and 50% in legs. These results indicate that supramicrolymphaticovenular anastomoses have a valuable place in the treatment of obstructive lymphedema.

Dynamic reconstruction of the abdominal wall using a reinnervated free rectus femoris muscle transfer

Dynamic reconstruction of the abdominal wall using a free reinnervated rectus femoris muscle and an island tensor fascia lata transfer was performed for a large herniation with loss of the bilateral rectus abdominis muscles of the abdominal wall. The tensor fascia lata transfer was used to close an inner side of the abdominal defect, and the rectus femoris muscle replaced the rectus abdominis muscle deficit. The motor nerve of the rectus femoris muscle was sutured to the motor branch of the intercostal nerve. Postoperatively, the transferred rectus femoris muscle was reinnervated via electromyography, and there was no abdominal protrusion and no hernia recurrence.

Free vascularized appendix transfer for reconstruction of penile urethras with severe fibrosis

Despite the development of newer techniques with a free radial forearm tube flaps for phallus reconstruction, severe urethral strictures are still seen in such cases after irradiation or repeated infection because of the paucity of healthy, well-vascularized tissue. For urethral reconstruction in cases with poorly vascularized tissue as well as for total penile creation, a new technique involving a free vascularized appendix transfer combined with a radial forearm osteocutaneous flap was successfully used in two cases. The appendix provides a normal tube structure composed of a muscular tubular layer lined with mucosal epithelium. It has no hair and has rich vascularization. This results in little stricture at the junction with the original urethra, no occurrence of urethral stones, and possible postoperative enlargement of the diameter with changes in catheters. This method will allow a patient with severe fibrosis around the urethra to undergo one-stage phallus reconstruction with minimal complications.

Free combined anterolateral thigh flap and vascularized fibula for wide, through-and-through oromandibular defects

Through-and-through oromandibular defects require the greatest amount of soft-tissue volume among the transfers for head and neck defects. A new method, a large anterolateral thigh flap combined with a vascularized fibula graft in a chimera fashion, has been used for two patients with wide through-and-through oromandibular defects. Among the candidates for such a large skin flap, the anterolateral thigh flap seems to be the best, for the following reasons. (1) Its pedicle, the lateral circumflex femoral system, has several major branches of equal size of anastomosis of the peroneal vessels. (2) As the majority of such patients with multiple previous surgery have lost recipient vessels near the mandible, the longest vascular pedicle is required. (3) There is no need for positional changes, and simultaneous flap elevation with the tumor resectioning is possible. (4) Use of the fibula allows for reconstruction of the entire mandible, if necessary. (5) Some of the shortcomings of individual donor sites for massive composite osteocutaneous flaps are minimized, because each component consists of two donor sites. (6) Operating time for this flap elevation is minimized, compared to that for massive composite osteocutaneous flaps, because the individual components can be obtained simultaneously by two teams.

Flow-through vascularized toe-joint transfer for reconstruction of segmental loss of an amputated finger

A segmental finger defect was reconstructed in a 46-year-old woman with a free flow-through vascularized toe-joint, including the proximal interphalangeal joint, the plantar digital nerve, and tendons of the second toe. The advantages of this composite flap are: (1) The segmental loss of the finger can be easily reconstructed to achieve a normal anatomic structure. (2) Excellent cosmesis is achieved, compared with conventional flaps such as the groin flap. (3) The distal segment of the donor toe can be preserved. (4) The transected digital arteries of the amputated finger can be simultaneously reconstructed with a flow-through arterial interposition. (5) The digital nerve can be repaired with a vascularized plantar digital nerve graft.

Paraumbilical perforator flap without deep inferior epigastric vessels

With the introduction of supramicrosurgery, a new paraumbilical perforator flap without a deep inferior epigastric vessel and with very small perforator anastomoses was used for nine patients. The abdominal defects of two patients, the lower leg or foot defects of five patients, and the scalp defects of two patients were repaired with an island perforator flap. The advantages of the paraumbilical perforator flap are as follows: (1) there is a very short operating time for flap elevation; (2) there is no invasion or sacrifice of any rectus abdominis muscle; (3) for middle-aged, obese patients, the donor site may be the best from the cosmetic point of view; (4) many small recipient vessels to anastomose the perforator exist throughout the body; (5) a thin skin flap with adequate thickness can be created easily with simultaneous removal of fatty tissue; (6) secondary defatting around the perforator can be done by minor surgery under local anesthesia; and (7) a vascularized adiposal flap with adequate thickness can be created easily. This flap seems to be indicated for female patients with defects in the abdominal wall and the lower leg. The island flap can easily resurface abdominal skin defects, such as intestinal fistula or radiation ulcers. The free flap is suitable for covering defects in the lower leg, foot, and scalp temporarily before administration of a tissue expander.

Free medial thigh perforator-based flaps: new definition of the pedicle vessels and versatile application

The medial thigh flap is a perforator-based flap nourished with septocutaneous or muscle perforators originating from the femoral vessels. To date, 8 patients have been repaired with this flap and extended or connected flaps including this flap: 4 patients with lower leg defects and 4 patients with intraoral and neck defects. The advantages of this flap are (1) several pedicle perforators exist for this flap, which makes possible duplicated vascular anastomoses to establish reliable circulation of the transferred flap; (2) the flap can be extended or connected to other neighboring flaps in the anterior thigh, so that extensively wide defects can be closed in one stage; (3) the great saphenous vein can be simultaneously used as a vein graft or for venous drainage for the flap; (4) the anterior branch of the femoral nerve can be used for sensory potential; and (5) there is minimum morbidity of the donor defect and a large dominant vessel for the leg can be preserved. The suitable indications for this flap are defects after removal of skin cancer in the foot or lower leg and wide defects after resection of head and neck cancer, which can be reconstructed with the flap connected to neighboring skin flaps. The disadvantages of this flap are that it has a small, short vascular pedicle and the bulkiness of the flap's fatty tissue often requires thinning.

Behavioral effects of HT-90B, a putative novel anxiolytic agent with potent antidepressive activity

1. HT-90B,((-)-N-[2-(8-methyl-1,4-benzodioxane-2-ylmethyl)am in o]ethyl]tricyclo[3,3,1,1(3,7)] decane-1-carboxamide), is a novel serotonin 5-HT(1A) full agonist with serotonin 5-HT(2) antagonistic action. 2. In a water licking conflict test, HT-90B (3-30 mg/kg, po) was more effective than buspirone in abolishing response suppression. 3. In a forced swim test, HT-90B (3-30 mg/kg, po) reduced the duration of immobility after a single oral dose, which contrasts with the requirement of multiple doses for desipramine (as a standard antidepressant) to produce the effect. 4. These two behavioral effects of HT-90B (20 mg/kg,po) were still evident even 4 hr after oral administration. And no tolerance was observed for these behavioral effects after repeated oral administration (10 mg/kg, b.i.d., 2 weeks). 5. HT-90B hardly produced any diazepam- or buspirone-like side effects. 6. In conclusion, it is suggested HT-90B is a potent anti-depressive anxiolytic with minimal side effects.

Scarpa's adipofascial flap for repair of wide scalp defects

Scarpa's fascia is a prominent superficial fascial system of the body. It consists of a single membrane between the superficial fatty layer and deep fatty layer, and lies widely in the lower abdominal wall. We describe a case with a wide scalp defect resulting from a resection of a dermatofibrosarcoma, and reconstruction of the defect with Scarpa's adipofascial flap (i.e., a combined paraumbilical perforator-based adipofascial flap-groin adipofascial flap). The primary advantage of Scarpa's adipofascial flap for scalp defects is that (1) the donor site is most acceptable for a free flap with a minimal donor scar and minimal dysfunction; (2) even in cases in which large flaps are used, donor defects can be closed directly without skin grafting; (3) in the obese patient, this flap is preferable because of cosmetic improvement of the abdominal wall; (4) the donor area has so many perforators that an extended adipofascial flap can be obtained with a combination of these perforators; and (5) the flap may be nourished with one of several arteries, such as the superficial or deep inferior epigastric artery, or the superficial or deep circumflex iliac artery. The disadvantages of this flap are that the territory with a single artery may be smaller than a skin flap with the same artery and oversurfacing of the graft results in a poor cosmetic appearance. Scarpa's adipofascial flap is indicated when the defects are in an exposed area, especially in children, young patients, and females, and when this procedure is combined with a skin-expanding method in the secondary repair.

Pharmacological profile of (-)HT-90B, a novel 5-HT1A receptor agonist/5-HT2 receptor antagonist

1. HT-90B ((-)-N-([2-(8-methyl-l, 4-benzodioxane-2-ylmethyl)amino]ethyl) tricyclo[3,3,1,1(3.7)] decane-1-carboxamide) had high affinities for the 5-HT1A (Ki = 0.18 nM) and 5-HT2 (Ki = 9.2 nM) receptors. 2. HT-90B inhibited forskolin activated adenylate cyclase in rat hippocampal membranes as a 5-HT1A full agonist (IC50 = 2 nM), and the potency of the drug was higher than that of 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), a standard 5-HT1A agonist. 3. In the serotonin syndrome test, HT-90B behaved as a weak partial 5-HT1A agonist in reserpinized rats. 4. 5-HT2 receptor-mediated potentiation of rabbit platelet aggregation by serotonin (5-HT) was reduced by HT-90B (IC50 = 1.73 microM). 5. Head twitch response induced by 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), a 5-HT2 agonist, was inhibited by HT-90B in mice. 6. It is concluded that HT-90B has potent 5-HT1A receptor agonist as well as 5-HT2 receptor antagonist properties in vitro and in vivo.

Impairment of spatial working memory of rats in radial maze performance induced by ethylcholine mustard aziridinium picrylsulfonate (AF64A-P): retention curve analysis

The effects of the cholinergic neurotoxin, ethylcholine mustard aziridinium picrylsulfonate (AF64A-P), on the spatial working memory in eight-arm radial maze performance were studied. Rats well-trained on radial maze performance were injected intracerebroventricularly with AF64A-P (0.05 nmol/each side) or artificial cerebrospinal fluid (A-CSF, 5 microliters). AF64A-P produced a selective reduction of choline acetyltransferase activity in the hippocampus. Rats treated with AF64A-P showed a significant decrease in the number of correct responses in baseline performance compared to rats injected with A-CSF. To examine whether the deficits might result from the disruption of memory, tests of memory retention were studied. Various delay intervals (45, 90, 180, or 360 min) were interposed between the fourth and the fifth choice, and the number of correct responses in the choices 5-8 were then examined as a function of retention intervals. Significant interaction of deficits in arm-choice accuracy induced by AF64A-P with retention intervals in the choices 5-8 was observed. Oxotremorine, a muscarinic receptor agonist (0.025, 0.05 and 0.1 mg/kg, ip), was able to reverse this deficit in a dose-dependent manner. These observations reveal a pattern of impairment of spatial working memory during prolonged states of central cholinergic hypofunction induced by intracerebroventricular administration of AF64A-P, which binds irreversibly to its receptor site.

Cholinergic modulation of spatial working memory of mice in radial maze performance: retention curve analysis

Cholinergic modulation of the spatial working memory of mice was investigated in an eight-arm radial maze. The mice were trained to achieve a stable baseline level of performance, and the retention of spatial working memory was then examined by means of imposition of retention intervals of 45, 90, 180, and 360 min between choices four and five. The animals were removed from the apparatus during these intervals. The effects of oxotremorine (0.025-0.1 mg/kg, ip), physostigmine (0.025-0.1 mg/kg, ip), and scopolamine (0.1-0.4 mg/kg, ip) on the number of the correct responses after the various time intervals (5-8 choices) were studied. Mice received drug injections 30 min prior to the first four arm-choices before delay intervals (1-4 choices). The number of correct responses after the intervals decreased with the increased length of the retention interval. Oxotremorine and physostigmine exhibited dose-dependent stimulating effects of resistance to decreases in the number of correct responses, but scopolamine potentiated the decline in a dose-dependent manner. Significant interactions between the effects of cholinergic drugs and the length of retention over time were also observed. These observations indicate a cholinergic modulation of spatial working memory in mice engaged in radial maze performance, as assessed by means of retention curve analysis.

[Discriminative stimulus properties of D-amphetamine: a neuropharmacological review]

It has been reported that laboratory animals can discriminate the presence of the psychomotor stimulant, D-amphetamine, from a non-drug or another drug condition. Under test conditions, doses lower than the training dose typically result in proportional decreases in D-amphetamine-appropriate responding, that is, dose-response curve is obtained. When drugs other than the training drug (D-amphetamine) are tested, they produced drug-appropriate responding to the extent that they resemble D-amphetamine (generalization or substitution test). And some antagonists (e.g., chlorpromazine) attenuate the stimulus effects of training drug. In the present review, the attempt to characterize the neuropharmacological characteristics of the discriminative stimulus properties of D-amphetamine is presented. The neural processes due to the transduction of D-amphetamine into stimulus properties may primarily involve central dopaminergic nervous system. Furthermore, drugs that share the discriminative stimulus properties in laboratory animals often produce similar subjective effects in human.

Effects of diazepam and chlorpromazine on socially induced anxiety in pigeons

The effects of diazepam and chlorpromazine on response suppression in a social situation were studied in pigeons. Three groups of pigeons were trained to peck a key on a variable-interval 60-s schedule of reinforcement, then exposed to the pain reaction of adjoining pigeon to electric shock. Although every pigeon showed suppression of response, the suppression decreased with repeated exposures. A conditioning group received the electric shock with the exposure to the pain reaction of adjoining bird; a shock exposure group received the electric shock without any explicit conditioned stimulus; and a control group did not receive any shock. After these treatments every group was exposed to the pain reaction of the adjoining bird. The conditioning group and the shock exposure group showed clear response suppression, but the control group did not. Although chlorpromazine generally reduced response rate in all groups, diazepam selectively abolished the response suppression.

The role of myelination in learning performance observed in two strains of myelin-deficient mutant mice (shiverer and mld)

In order to study whether myelination is involved in learning performance, the behavior of myelin-deficient mutant mice (shiverer and mld) was examined. Shiverer is a deletion mutant of the myelin basic protein (MBP) gene causing severe myelin deficits due to the complete absence of MBP, while mld, allelic mutant to shiverer, shows lowered MBP expression, resulting in less severe effects. Shiverer clearly showed deficits in successive reversal learning, while mld showed less deficits in the learning performance. Both mutant mice showed no deficits in the radial maze performance, which is though to show the natural foraging behavior of rodents. These results suggest that myelin formation is related to learning but not to natural behavior.