The use of transcutaneous electrical nerve stimulation (TENS) to aid perceptual embodiment of prosthetic limbs.

Integration of prosthetic limb awareness into body schema is likely to aid manual control of the prosthesis. Physiotherapists and prosthetists use techniques to generate mechanical, visual and/or auditory feedback related to stimulation of the stump and proximal residual limb to improve prosthetic limb awareness. Electrical stimulation of afferent nerves using implanted electrodes can generate sensations of touch, joint movement, and position, in the missing, phantom limbs of amputees. We report here a novel hypothesis that non-invasive transcutaneous electrical nerve stimulation (TENS) could be used to facilitate the process of perceptual embodiment of a prosthesis into the body schema of amputees. Using a modified version of the rubber hand illusion (RHI), we have found that TENS paraesthesiae can be made to feel like it is emanating from a prosthetic hand in healthy participants with intact limbs. In addition, participants reported perceptual embodiment of the prosthetic hand into their body schema, i.e. it felt as if it is part of their body. We predict that projecting TENS paraesthesiae into the prosthetic limb(s) of amputees will provide sufficient sensory input to facilitate perceptual embodiment. This could prove to be a simple and inexpensive training aid to improve ambulation and prosthesis success.

Some effects of epidermal growth factor on reproductive function in Merino sheep.

During the i.v. infusion of a depilatory dose (100 micrograms/kg bodyweight) of mouse epidermal growth factor (EGF) into ovariectomized Merino ewes the frequency of pulsatile LH release was significantly reduced. However, the amplitude of pulses of LH secretion, either those naturally occurring or those induced by LHRH injection, was unchanged or only slightly reduced. Similar infusions of mouse EGF were made in progestagen-treated anoestrous Merino ewes in which LH secretion was maintained by injections of LHRH. These ewes did not experience oestrus or ovulate in response to PMSG injected 1 day after mouse EGF treatment (2 days before progestagen withdrawal); both responses occurred in controls. The EGF-treated ewes experienced oestrus and ovulated following progestagen-PMSG treatment 6 weeks later. These results suggest that mouse EGF inhibits the hypothalamic pulse generator responsible for LH release in the ewe but has little if any effect on pituitary sensitivity to LHRH; and mouse EGF apparently has a direct effect on the ovaries, temporarily impairing their ability to ovulate in response to exogenous gonadotrophin.

The effect of hypothalamic lesions on estradiol-induced changes in LH release in the ewe.

The effect of hypothalamic lesions on estradiol-induced changes in plasma luteinizing hormone (LH) concentration was studied in ovariectomized ewes. The ewes had stainless steel electrodes chronically implanted in the hypothalamus (HYP), and electrolytic lesions were made within 1 h after the injection of 50 microgram estradial benzoate (EB) i.m. Blood samples were collected at 2--6 h intervals for 30 h after EB, and the plasma was subsequently assayed for LH. None of the lesions produced had any effect on the normal immediate (within 12 h after injection) inhibitory effect of estrogen on LH release. However basal hyothalamic lesions, ranging from the suprachiamatic region back over the optic chiasma down to include the anterior tuberal region, effectively inhibited the normal stimulatory effect of estrogen (12--30 h after injection) on LH release. The results are consistent with the interpretation that, in the normal biphasic LH response to injected estrogen in the ewe, the early inhibition of LH release results from direct inhibition of pituitary sensitivity to endogenous LH-releasing factor (LRF). On the other hand the estrogen-induced LH release which occurs subsequent to this inhibitory phase is principally the result of increased LRF secretion by the HYP.

Effects of intraventricular injections of norepinephrine on brain-pituitary-ovarian function in the rabbit.

In estrous estrogen-primed female rabbits with electrodes chronically implanted in various subcortical regions of the brain, the intraventricular injection of an ovulation-inducing dose of norepinephrine (NE) stimulated a prolonged episode of high amplitude 40-60 cps electroencephalographic (EEG) activity in the olfactory bulb (OB) and its projections. This activity, which started usually between 30 and 60 min after NE injection and was maintained continously for periods up to an hour thereafter, was regularly absent in the same rabbits when they were pseudopregnant and non-ovulatory to NE. Similar OB-EEG activity and ovulation had been observed earlier in response to intraventricular histamine under light pentobarbital anesthesia. The ovulatory response to histamine was eliminated by massive midbrain lesions or removal of the olfactory bulb, but intraventricular NE still induced ovulation after such losses. The ovulatory effectiveness of NE was blocked, however, by low doses of pentobarbital or high doses of atropine, neither of which inhibited the ovulatory response to intraventricular epinephrine. Atropine and alpha-adrenergic blocking agents also prevented the ovulatory response to intraventricular histamine. It is suggested that histamine activates pituitary-ovarian function by stimulating central noradrenergic elements and that NE has more of the physiological-pharmacological characteristics of a natural central nervous activator of luteinizing hormone-releasing hormone than has epinephrine.

The function of antidiuretic hormone in the sheep.

1. With the aim of producing diabetes insipidus in sheep, electrolytic lesions were placed in the ventral medial hypothalamus immediately posterior to the optic chiasm.2. After formation of lesions, the pattern of urine excretion showed a triphasic response consisting of (i) an immediate diuresis reaching a maximum within 4 days, (ii) an interphase of about 12 days wherein rates of urine flow were normal, and (iii) a final phase of permanent polyuria. With the four sheep used in this work, the time between placement of the lesions and onset of permanent hyposthenuria was 19-22 days.3. In the final polyuric phase, the sheep were unable to concentrate their urine in response to dehydration or to feeding.4. Infusions of arginine vasopressin restored the ability of these animals to excrete urine that was hypertonic to plasma.5. The evidence showed that the hypothalamic lesions were effective in producing permanent diabetes insipidus. It was concluded that anti-diuretic hormone (ADH) has essentially the same function in sheep as it has in other mammalian species; that is, the hormone facilitates the elaboration of hypertonic urine. There was no evidence to suggest that ADH had a special effect on potassium excretion in the sheep.