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W Schultz

Publications and source records attributed to W Schultz.

At least 127 records · Page 7Linked to original sources
PubMed1977

Integration of cerebral and peripheral inputs by interpositus neurons in monkey.

The patterns of convergence of cerebral and peripheral nerve inputs onto interpositus neurons were studied in cebus monkeys. The strongest inputs to interpositus neurons are from motor and somatosensory cortex, with weaker inputs from peripheral nerves and cerebral area 6. The neurons in the anterior portion of interpositus receive cerebral and peripheral inputs primarily representing the hindlimb, while inputs to neurons in the posterior division represent forelimb or mixed forelimb and hindlimb. The hindlimb neurons integrate signals principally from motor cortex, somatosensory cortex, nerves, supplementary motor and medial pre-motor areas, while forelimb neurons receive inputs from motor, somatosensory, lateral premotor cortical areas and nerves. The results from this study are compared with those from studies of interpositus and dentate neurons in cat and monkey in order to determine the role of n. interpositus in movement. It is suggested that the inputs integrated by interpositus neurons are consistent with a role in up-dating skilled movements.

Action Potentials↗
PubMed1977

Metabolism of kinins and angiotensins in the isolated glomerulus and brush border of rat kidney.

In order to localize the activities of kallikrein, kininase, angiotensin I converting enzyme, and angiotensinase in the kidney, rat kidneys were homogenized and glomeruli and brush border were isolated. The yield and purity of glomeruli preparations were high. The similarity of the structure of the isolated glomeruli in situ was established by scanning and transmission electron microscopy and freeze-fracture. The morphology of isolated brush border of proximal tubules was compared to brush border in situ. Isolated brush border, devoid of core material, retained its converting enzyme, kininase, and angiotensinase activity confirming our previous findings that these enzymes are bound to plasma membrane. Isolated glomeruli contained little or no kallikrein. In addition, compared to renal brush border, renal glomeruli contained a relatively low concentration of kininase, angiotensin I converting enzyme, and angiotensinase. The results of these experiments support the idea that the brush border of the proximal tubule is the major site of inactivation of kinins and angiotensins and that renal kallikrein enters the tubular filtrate distal to the glomeruli and proximal tubule.

Angiotensin II↗
PubMed1976

A comparison of primary afferent and cortical neurone activity coding sinus hair movements in the cat.

Responses in the somatosensory cortical area S I to stimulation of facial sinus hairs were recorded in the anaesthetized cat and compared with activity in primary afferent fibres innervating vibrissae follicles. The specific cortical vibrissa area is somatotopically organized; 39% of the cortical units in that area responded to stimulation of only a single sinus hair but in some cases all maxillary vibrissae activated a single cortical neurone. The responses consisted of three major groups; either a phasic discharge in response to the movement part of a stimulus, or an additional tonic discharge related to the steady period of vibrissa deflection, or a tonic discharge. On the basis of a comparison of response and excitability characteristics of primary afferent and cortical neurones it is concluded that all four kinds of peripheral units innervating sinus hair follicles project to the somatosensory cortical area S I. It appears from these findings that some cortical neurones receive a specific input related to a particular component of the complex primary afferent response in fibres innervating sinus hair follicles. The results are discussed with respect to previous reports on the central representation of facial sinus hairs in different species.

Afferent Pathways↗
PubMedDate not supplied

Reward prediction in primate basal ganglia and frontal cortex.

Reward information is processed in a limited number of brain structures, including fronto-basal ganglia systems. Dopamine neurons respond phasically to primary rewards and reward-predicting stimuli depending on reward unpredictability but without discriminating between rewards. These responses reflect 'errors' in the prediction of rewards in correspondence to learning theories and thus may constitute teaching signals for appetitive learning. Neurons in the striatum (caudate, putamen, ventral striatum) code reward predictions in a different manner. They are activated during several seconds when animals expect predicted rewards. During learning, these activations occur initially in rewarded and unrewarded trials and become subsequently restricted to rewarded trials. This occurs in parallel with the adaptation of reward expectations by the animals, as inferred from their behavioral reactions. Neurons in orbitofrontal cortex respond differentially to stimuli predicting different liquid rewards, without coding spatial or visual features. Thus, different structures process reward information processed in different ways. Whereas dopamine neurons emit a reward teaching signal without indicating the specific reward, striatal neurons adapt expectation activity to new reward situations, and orbitofrontal neurons process the specific nature of rewards. These reward signals need to cooperate in order for reward information to be used for learning and maintaining approach behavior.

Animals↗
PubMedDate not supplied

A predictive reinforcement model of dopamine neurons for learning approach behavior.

A neural network model of how dopamine and prefrontal cortex activity guides short- and long-term information processing within the cortico-striatal circuits during reward-related learning of approach behavior is proposed. The model predicts two types of reward-related neuronal responses generated during learning: (1) cell activity signaling errors in the prediction of the expected time of reward delivery and (2) neural activations coding for errors in the prediction of the amount and type of reward or stimulus expectancies. The former type of signal is consistent with the responses of dopaminergic neurons, while the latter signal is consistent with reward expectancy responses reported in the prefrontal cortex. It is shown that a neural network architecture that satisfies the design principles of the adaptive resonance theory of Carpenter and Grossberg (1987) can account for the dopamine responses to novelty, generalization, and discrimination of appetitive and aversive stimuli. These hypotheses are scrutinized via simulations of the model in relation to the delivery of free food outside a task, the timed contingent delivery of appetitive and aversive stimuli, and an asymmetric, instructed delay response task.

Animals↗
PubMedDate not supplied

[Long-term results of the Blauth knee prosthesis--current status of hinged knee prostheses].

AIM: Currently there is widespread use of unconstrained knee arthroplasty even in severe deformities of the knee. In order to ascertain the value and future of constrained knee prostheses, we have assessed the results of the Blauth knee prosthesis and compared them with the results of unconstrained knee prostheses. METHODS: In a retrospective analysis we examined 227 Blauth knee prosthesis implantations performed between 1985 and 1997. Using endpoints of prosthesis removal, infection and aseptic loosening, the 10-year survivorship analysis was evaluated. RESULTS: The analysis shows a 10-year survivorship of 90.1 % using aseptic loosening or infection as an endpoint and 96.2 % using removal as an endpoint. CONCLUSION: The first designs of constrained knee prostheses were associated with a high failure rate, while more recent designs like the St. Georg knee prosthesis and the Blauth knee prosthesis show long-term results similar to condylar designs. Since there has been a large increase of knee endoprosthesis implantations in the last years, a constrained knee prosthesis with excellent long-term results remains a valuable implant in cases of revisions and difficult knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMedDate not supplied

[Current status of wrist arthrodesis].

AIM: In order to ascertain the value and future of wrist arthrodesis we assessed the results of 47 wrist arthrodeses performed at the Departments of Orthopaedic and Trauma Surgery of the University of Goettingen between 1980 and 1998. METHOD: In a retrospective analysis we examined the patients clinical and radiological records. Evaluating the results we used the score described by Lohmann and Buck-Gramcko in order to consider function, pain, strength and assessment of the patient him/herself. RESULTS: 93.6 % of all cases could be examined. We found a wrist arthrodesis in posttraumatic arthritis in 22 cases and in rheumatoid arthritis in 25 cases. Plate (n = 30) and Rush-Pin osteosynthesis (n = 17) were used as surgical procedures. In all patients we found a successfully stabilised wrist, although in 3 trauma cases a further surgical procedure was necessary. A better function of the wrist was reached in every patient. The majority of the patients had no pain and an acceptable strength. The results obtained showed good and excellent results in 86.4 % of the wrist arthrodesis for post-traumatic arthritis and in 90.9 % for rheumatoid arthritis. CONCLUSION: The increase in quality of life, especially in patients suffering from rheumatoid arthritis, shows the procedure of wrist arthrodesis to be a still worthwile surgery.

Adolescent↗
PubMedDate not supplied

[Orthopaedic surgery residency: comparison between the German and the North American system].

AIM: On the way to the unification of the European Union (EU), Germany has passed a new medical professional education system at the 106 (th) German medical board in Cologne in 2003. The medical board has established a new residency programme for the specialty of orthopaedic surgery, which was previously separated into orthopaedic and trauma surgery. An exchange of orthopaedic surgeons within the EU is therefore less complicated. For an exchange outside the EU, an international comparison especially with the USA is warranted. METHOD: We analysed and compared the German "Assistenzarzt System" with the residency programme of the USA regarding the specialty of orthopaedic surgery and further sub-specialisation programmes. RESULTS: After evaluation of both systems, a high conformity in the basic training for orthopaedic surgery was demonstrated. However, there is a difference between the two systems regarding specialisation after residency training with the German "Oberarzt" on the one side and the American fellow system on the other side. CONCLUSION: This study demonstrates that the German orthopaedic training matches well with the American residency programs. There is potential for acknowledgement of the German title "Orthopaedic surgeon" in the USA. In some states, such as Pennsylvania, European medical specialists are given institutionally restricted work permission for limited periods of time. It remains, however, questionable if there is a general political intent for the USA to acknowledge German or European residency programs.

Curriculum↗
PubMedDate not supplied

Neural correlates of learning in the prefrontal cortex of the monkey: a predictive model.

The principles underlying the organization and operation of the prefrontal cortex have been addressed by neural network modeling. The involvement of the prefrontal cortex in the temporal organization of behavior can be defined by processing units that switch between two stable states of activity (bistable behavior) in response to synaptic inputs. Long-term representation of programs requiring short-term memory can result from activity-dependent modifications of the synaptic transmission controlling the bistable behavior. After learning, the sustained activity of a given neuron represents the selective memorization of a past event, the selective anticipation of a future event, and the predictability of reinforcement. A simulated neural network illustrates the abilities of the model (1) to learn, via a natural step-by-step training protocol, the paradigmatic task (delayed response) used for testing prefrontal neurons in primates, (2) to display the same categories of neuronal activities, and (3) to predict how they change during learning. In agreement with experimental data, two main types of activity contribute to the adaptive properties of the network. The first is transient activity time-locked to events of the task and its profile remains constant during successive training stages. The second is sustained activity that undergoes nonmonotonic changes with changes in reward contingency that occur during the transition between stages.

Animals↗