In the course of investigations of interstriatal relationships, studied with electrical stimulation, small unilateral lesions were placed into the dorsomedial reticular formation of rats at the superior collicular level. Following the placement of these lesions, the amplitudes of the summed and averaged interstriatal responses were greatly increased. A clinical correlate was reduction of the speed of locomotion, at times advancing to complete akinesia, catatonia, and frequently generalized clonus. The acetylcholine (Ach) level (as determined in five control animals) rose from the mean striatal level of 6.5 µg/g (±1.02) by 100% to 13.3 µg/g (±1.16) 6–8 h after the reticular lesion was placed. The Ach level was determined according to the method of Crossland after the animals were killed in liquid nitrogen. We then placed in a series of other rats large lesions into the amygdaloid complex, including the origin of the stria terminalis. Catalepsy did not occur when this procedure was followed by injury to the midbrain tegmentum. These rats showed spontaneous locomotion, and clonic seizures appeared only infrequently. In these animals, the mean amount of Ach in the striata was only slightly elevated to 7.1 µg/g (±0.76). The elevation of Ach in the striate, produced in the previous set of experiments by lesions in the reticular formations, was prevented by the prior placement of amygdaloid lesions. In addition, the amygdaloid lesion prevented an increase of amplitude of the interstriatally evoked and recorded responses. Symmetrel (amantadine hydrochloride) is known to enhance dopamine turnover in the striata of untreated rats. It also increases spontaneous running speed during the initial dosages. Thereafter, repeated daily administration of large doses of Symmetrel was followed by decreased locomotion and eventually bradykinesia or akinesia with rigidity. In these rats, the striatal Ach level increased to 10.7 µg/g (± 0.92). Since the above mentioned experimental catatonia developed as a consequence of striatal excitation associated with Ach increase, we followed this line of experiments in another group of rats with subcutaneous injections of small amounts of bulbocapnine measuring 11.5 µg/g (±0.91). This finding raised the possibility that the catatonia produced by bulbocapnine is the consequence of an elevation in the striatal levels of Ach and accompanying physiological events in the striatal system. The catatonia produced by the various manipulations described could be reversed by the injection of 80–100 mg L-dopa in solution, i.p. and sometimes locomotor activity was even greater than that observed in the control period.
Published studies of the anatomy and variability of the dentate nucleus in relation to landmarks of the fourth ventricle are few in number and limited in extent. To determine the variability of this structure, measurements have been made in sufficient numbers of specimens to be statistically significant. Finite radiological relationships were established and the variability of possible radiological reference planes estimated from 48 stereotaxic ventriculograms. Thirty cerebellar hemispheres obtained without special methods of fixation were sectioned at 1-mm intervals and the nuclear variability measured from the most reliable reference plane. A high degree of variability was found which may explain the varying therapeutic effect of dentatotomy and the dissimilar physiological effects reported. To further eliminate anatomical variability due to distortion during fixation, a further 30 cerebellar specimens obtained by a partial decapitation technique with fixation in situ in the skull have been sectioned after stereotaxic marking in a sarcophagus [Andrew and Watkins, 1969] and the dentate and roof nuclear measurements and variability established.
The physiological basis for the interruption of pain by acupuncture for anesthesia and analgesia has been of great interest in the last few years, since communications with Red China have become more common. The physiological basis for the effect of acupuncture on pain is still conjectural, but may well be related to a peripheral field effect from differential sensory input. To study this phenomenon, twelve cats were used in an acute preparation. Responses to C fiber input were recorded in the medial thalamus, both by average evoked responses and by single cell recordings with microelectrodes. When large myelinated fiber input from a different portion of the body was used in conjunction with noxious input, gross evoked responses to pain were clearly diminished, and single cell responses were altered. This modulation of C fiber input by large fibers was long lasting – a single interaction between two inputs led to a diminution of evoked responses to the noxious stimulus alone lasting up to 1 h. Analysis of single cell responses to noxious and non-noxious input to the thalamus suggested that a supraspinal gating mechanism was responsible for the different types of cellular responses being recorded in the centre median pulvinar and parafascicularis area. This supraspinal gating is discussed in relation to the analgesic effect of acupuncture nerve stimulation and other methods of pain relief as well as the theoretical method of processing sensory information in the thalamus.
Twenty-one patients with torticollis have been operated upon during the 1946–1973 period. The site of surgical attack has changed with time and better understanding of physiopathology. Thus the first 8 patients had had cervical motor rhizotomies plus accessory neurotomies. The remaining 13 cases all had stereotactic lesions 6 of them complemented with peripheral procedures. In the first group with exclusive stereotactic destructions the disease type was: (a) rotational torticollis with dystonic background in 6 patients and (b) 1 pure horizontal form. In the first subgroup (a) all had VO thalamotomies bilaterally in all but 2 cases which were combined with pallidotomy or nucleus preinterstitialis. The second subgroup (b) had subthalamotomy. In the second group the disease type was: retrocollis in 2 cases and rotational torticollis in 4, all of them with severe myoclonic component. All had bilateral VO thalamotomies and all had additional bilateral motor rhizotomies combined in 4 cases with XIth neurotomy. Results for the first group were fair for the 6 cases (a) with dystonic component and excellent for the (b) pure horizontal form. However in the second group we were forced to add cervical motor rhizotomies and/or accessory neurotomy to improve results. The patients seem to do better with the lower stereotactic targets.
Ten patients undergoing stereotaxic thalamotomies had electroencephalograms and computer averaging of cortical responses evoked by left and right median nerve stimulation preoperatively peroperatively and postoperatively. Most of the thalamotomies were performed to relieve rigidity or abnormal movements. All thalamotomies were performed by the posterior trajectory using radiologic and electrophysiologic techniques to localize the targets which were usually V.O.p. and V.O.a. nuclei. Evoked responses were also obtained from V.P. The postoperative EEG changes were minor in general but the somatosensory-evoked responses showed variable changes with some showing general simplification on the side of the lesion with contralateral stimulation. This finding was seen with no apparent clinical deficit. A lesion for pain in CM-Pf. region produced bilateral changes. Four thalamotomies with V.O.p. lesions and V.O.a. lesions or V.O.p. lesions alone produced amplitude increases in late components on the lesion side with ipsilateral stimulation. The findings suggest that somatosensory evoked responses may be abnormal in the absence of any objective neurologic deficit or EEG changes following thalamotomy.
Single or repetitive stimulation of the thalamic nucleus has been performed during stereotaxic surgery for over 250 patients with extrapyramidal disorders or intractable pain in our service for the last 7 years, because the stimulation has been encountered as a useful tool for determination of the stereotaxic target. Aside from such direct therapeutic considerations, computer analysis of the cortical evoked responses has brought us much interesting information regarding the physiological mechanism of the thalamo-cortical relations in man. Thus, bilateral, three-negative, cortically evoked responses after single stimulation of the unilateral VL nucleus of the thalamus and differences of augmenting and recruiting responses between the human and the laboratory animal have been reported in the last symposium. In our recent study further investigation of the possible pathway from the stimulated unilateral VL nucleus to bilateral cortex and some analysis of augmenting response were carried out with 50 parkinsonism patients. The impulse which provokes the first positive wave of the contralateral side was thought to be transmitted from stimulated VL nucleus to the contralateral cortex directly via corpus callosum with a velocity of 36–43 m/sec. Repetitive stimulation of the VL nucleus showed typical augmenting or recruiting-like augmenting responses under a certain condition.
