In adult dogs and puppies ranging in age from 1 day up to 3 months the functional organization of the motor cortex has been investigated with 50 or 60 cycle a-c stimulation under Nembutal anesthesia. In adult dogs two separate, somatotopically organized motor areas have been differentiated (i) the "precentral" motor area (MI) which occupies mainly the rostral half of the gyrus sigmoideus posterior, and (ii) the supplementary motor area (MII) located in the lateral two-thirds of the gyrus sigmoideus anterior. In addition, stimulation of the somatosensory area I (SI) in the caudal half of the gyrus sigmoideus posterior elicited somatic movements. Stimulation of MI produced low threshold, relatively simple movements of the contralateral extremities. Movements obtained from SI were similar, but had much higher thresholds. Stimulation of MII yielded high threshold, complex and often bilateral movements. In puppies up to 3 weeks of age cortical stimulation elicited bilateral movements which showed no definite projection pattern. From the 4th week of life a somatotopic organization and contralateral representation of the body began to appear and then gradually to evolve in the direction of the adult pattern. At the end of the 3rd month movements in puppies were essentially similar to those of adult dogs. However some minor differences were still present, suggesting that the process of maturation of cortical motor areas were not yet completed at this age.
The role of age in the recovery of motor functions following unilateral pyramidotomy was studied in groups of puppies operated on at the age of 1, 2, 3 and 5 mo. The animals were trained postoperatively to retrieve with their forepaw morsels of food from test devices varying in shape, diameter and depth. Groups of normal animals of similar ages were trained in parallel. In all age groups the motor impairment following pyramidotomy was proportional to the digital involvement in a given task. Furthermore, the performance of operated dogs was essentially similar in all age groups and no better recovery of function was observed in animals operated on at the age of 1 than at 5 mo. The results are discussed in view of conflicting data concerning the age related differences in the recovery of motor functions after destruction of the pyramidal system in various species.
The aim of the experiments was to check the validity of the method of contact electrodes for studying overground locomotion in the rat. The basic indices of locomotion, obtained in 7 intact rats with at least 100 steps recorded in each, were analysed and compared with those described by other authors using different methods of movement recording. It was found that the method of contact electrodes gives reproducible and reliable results and may thus be used in further experiments of rat locomotion after CNS lesions.
Abstract Corticothalamic projections from postcruciate area 4, located on the rostral part of the posterior sigmoid gyms, were traced with the autora‐diographic technique in the dog. Injections of tritiated amino acids were made into the lateral and medial parts of area 4 in regions corresponding to the forelimb and hindlimb areas of the primary motor cortex, respectively. In cases with injections placed in the lateral part of areas, dense accu‐mulations of label were present in the lateral part of the ventral anterior nucleus (VA), the central part of the ventral lateral nucleus (VL), the ventral half of the ventral posterior inferior nucleus (VPI), the caudal part of the central lateral nucleus (CL), and the centrum medianum (CM). Lighter label was also present in the lateral part of the cytoarchitectonically distinct VL region bordering the ventrobasal complex (VB), as well as in the ventro‐lateral part of the mediodorsal nucleus (MD), and in the lateral posterior nucleus (LP). In one case in which the injection site involved an adjacent part of area 3a, label was also seen ventrally in the medial division of the posterior nuclear group (POm). However, no detectable differences in VL, MD, or intralaminar labeling patterns were noted between this case and the four other cases with injections confined to the lateral part of area 4. In two cases with injections restricted to the medial part of area 4, dense label was present in the lateralmost part of VL, the ventral part of VPI, the caudal part of CL, and CM. Lighter label was also present in the VL region bordering the dorsolateral edge of VB and in LP. An additional case in which the injection also involved the rostral border of area 3a showed a similar pattern cf thalamic labeling. Projections from both the lateral and medial parts of area 4 were also noted in the subthalamic nucleus, zona incerta, and nucleus of Darkschewitsch. These results suggest that Corticothalamic projections from postcruciate area 4 to VL are organized topographically such that projections from the lateral part of area 4 project centrally within VL while those from the medial part of area 4 project more laterally. Both parts of area 4 also project top‐ographically to a cytoarchitectonically distinct region of VL located im‐mediately adjacent to VB, In contrast, the projections to the intralaminar nuclei do not appear to be topographically organized. The data from cases involving spread of the injection into area 3a suggest that projection pat‐terns from area 3a to ventral, intralaminar, and medial thalamic nuclei are similar to those from area 4. However, it appears that at least the lateral part of area 3a also projects to POm.
