Model-Driven Analysis of Eyeblink Classical Conditioning Reveals the Underlying Structure of Cerebellar Plasticity and Neuronal Activity

The cerebellum plays a critical role in sensorimotor control. However, how the specific circuits and plastic mechanisms of the cerebellum are engaged in closed-loop processing is still unclear. We developed an artificial sensorimotor control system embedding a detailed spiking cerebellar microcircuit with three bidirectional plasticity sites. This proved able to reproduce a cerebellar-driven associative paradigm, the eyeblink classical conditioning (EBCC), in which a precise time relationship between an unconditioned stimulus (US) and a conditioned stimulus (CS) is established. We challenged the spiking model to fit an experimental data set from human subjects. Two subsequent sessions of EBCC acquisition and extinction were recorded and transcranial magnetic stimulation (TMS) was applied on the cerebellum to alter circuit function and plasticity. Evolutionary algorithms were used to find the near-optimal model parameters to reproduce the behaviors of subjects in the different sessions of the protocol. The main finding is that the optimized cerebellar model was able to learn to anticipate (predict) conditioned responses with accurate timing and success rate, demonstrating fast acquisition, memory stabilization, rapid extinction, and faster reacquisition as in EBCC in humans. The firing of Purkinje cells (PCs) and deep cerebellar nuclei (DCN) changed during learning under the control of synaptic plasticity, which evolved at different rates, with a faster acquisition in the cerebellar cortex than in DCN synapses. Eventually, a reduced PC activity released DCN discharge just after the CS, precisely anticipating the US and causing the eyeblink. Moreover, a specific alteration in cortical plasticity explained the EBCC changes induced by cerebellar TMS in humans. In this paper, for the first time, it is shown how closed-loop simulations, using detailed cerebellar microcircuit models, can be successfully used to fit real experimental data sets. Thus, the changes of the model parameters in the different sessions of the protocol unveil how implicit microcircuit mechanisms can generate normal and altered associative behaviors.The cerebellum plays a critical role in sensorimotor control. However, how the specific circuits and plastic mechanisms of the cerebellum are engaged in closed-loop processing is still unclear. We developed an artificial sensorimotor control system embedding a detailed spiking cerebellar microcircuit with three bidirectional plasticity sites. This proved able to reproduce a cerebellar-driven associative paradigm, the eyeblink classical conditioning (EBCC), in which a precise time relationship between an unconditioned stimulus (US) and a conditioned stimulus (CS) is established. We challenged the spiking model to fit an experimental data set from human subjects. Two subsequent sessions of EBCC acquisition and extinction were recorded and transcranial magnetic stimulation (TMS) was applied on the cerebellum to alter circuit function and plasticity. Evolutionary algorithms were used to find the near-optimal model parameters to reproduce the behaviors of subjects in the different sessions of the protocol. The main finding is that the optimized cerebellar model was able to learn to anticipate (predict) conditioned responses with accurate timing and success rate, demonstrating fast acquisition, memory stabilization, rapid extinction, and faster reacquisition as in EBCC in humans. The firing of Purkinje cells (PCs) and deep cerebellar nuclei (DCN) changed during learning under the control of synaptic plasticity, which evolved at different rates, with a faster acquisition in the cerebellar cortex than in DCN synapses. Eventually, a reduced PC activity released DCN discharge just after the CS, precisely anticipating the US and causing the eyeblink. Moreover, a specific alteration in cortical plasticity explained the EBCC changes induced by cerebellar TMS in humans. In this paper, for the first time, it is shown how closed-loop simulations, using detailed cerebellar microcircuit models, can be successfully used to fit real experimental data sets. Thus, the changes of the model parameters in the different sessions of the protocol unveil how implicit microcircuit mechanisms can generate normal and altered associative behaviors.

Frailty and resilience in an older population. The role of resilience during rehabilitation after orthopedic surgery in geriatric patients with multiple comorbidities

Hip fracture is common in the elderly and it is usually associated with comorbidities and physiological changes which may have an impact on functioning and quality of life. The concept of resilience may explain why this impact varies among patients. The aim of this open, prospective cohort study was to explore the relationships between resilience, frailty and quality of life in orthopedic rehabilitation patients, and also to assess whether these factors might affect rehabilitation outcome. Eighty-one patients, older than 60 years, underwent a multidisciplinary assessment at the beginning and at the end of the rehabilitation period following orthopedic surgery to the lower limb. The assessments were performed using the Resilience Scale, the Multidimensional Prognostic Index (as a measure of frailty), the WHO Quality of Life-BRIEF, the Geriatric Depression Scale, and the Functional Independence Frailty and resilience in an older population. The role of resilience during rehabilitation after orthopedic surgery in geriatric patients with multiple comorbidities Measure (as a measure of the rehabilitation outcome). A negative correlation between disability and resilience emerged and this association interacted with frailty level. We also found that resilience and quality of life are positive predictors of functional status at discharge.

Categorisation of tibial artery disease on computer tomography angiography according to the TASC II classification

Purpose Computer tomography angiography is used to assess peripheral arterial disease. Its preference over other imaging modalities is based upon its rapid acquisition and high spatial resolution, along with ease of access. TASC II have recently updated their vascular lesion classification to include infrapopliteal lesions, and our aim is to assess the reproducibility of TASC II on infrapopliteal disease when using computer tomography angiography. Methods A retrospective analysis of a series of consecutive computer tomography angiographies was performed by seven assessors (three consultant radiologists, two consultant vascular surgeons and two vascular specialty trainees). Each assessor was asked to classify the target vessel based on the TASC II classification. Statistical analysis was performed using Cohen's weighted kappa. Results Seven assessors analysed 48 target vessels in 25 patients (20 men), with a mean age of 72.9 years. Twenty posterior tibial, 27 anterior tibial and one peroneal artery were analysed. Poor agreement was demonstrated between the two vascular consultants, with a kappa of 0.094. Weak agreement was demonstrated among the radiologists, with a kappa of 0.547. The total group of assessors had a kappa of 0.176. Conclusion This study showed poor agreement between assessors when applying the TASC II classification to infrapopliteal lesions on computer tomography angiography. TASC II should not be used to classify lesions, for clinical or research purposes, with this image modality.

Representation of Mental Imagery Functions

A questionnaire was administered to 250 undergraduates to study their conceptions about the efficacy of mental images in thinking. Analysis showed that subjects rated differently the usefulness of visual imagery according to the kind of content rather than the mental process involved.

Modeling the Cerebellar Microcircuit: New Strategies for a Long-Standing Issue

The cerebellar microcircuit has been the work bench for theoretical and computational modeling since the beginning of neuroscientific research. The regular neural architecture of the cerebellum inspired different solutions to the long-standing issue of how its circuitry could control motor learning and coordination. Originally, the cerebellar network was modeled using a statistical-topological approach that was later extended by considering the geometrical organization of local microcircuits. However, with the advancement in anatomical and physiological investigations, new discoveries have revealed an unexpected richness of connections, neuronal dynamics and plasticity, calling for a change in modeling strategies, so as to include the multitude of elementary aspects of the network into an integrated and easily updatable computational framework. Recently, biophysically accurate “realistic” models using a bottom-up strategy accounted for both detailed connectivity and neuronal non-linear membrane dynamics. In this perspective review, we will consider the state of the art and discuss how these initial efforts could be further improved. Moreover, we will consider how embodied neurorobotic models including spiking cerebellar networks could help explaining the role and interplay of distributed forms of plasticity. We envisage that realistic modeling, combined with closed-loop simulations, will help to capture the essence of cerebellar computations and could eventually be applied to neurological diseases and neurorobotic control systems.

Healthy and pathological cerebellar Spiking Neural Networks in Vestibulo-Ocular Reflex

Since the Marr-Albus model, computational neuroscientists have been developing a variety of models of the cerebellum, with different approaches and features. In this work, we developed and tested realistic artificial Spiking Neural Networks inspired to this brain region. We tested in computational simulations of the Vestibulo-Ocular Reflex protocol three different models: a network equipped with a single plasticity site, at the cortical level; a network equipped with a distributed plasticity, at both cortical and nuclear levels; a network with a pathological plasticity mechanism at the cortical level. We analyzed the learning performance of the three different models, highlighting the behavioral differences among them. We proved that the model with a distributed plasticity produces a faster and more accurate cerebellar response, especially during a second session of acquisition, compared with the single plasticity model. Furthermore, the pathological model shows an impaired learning capability in Vestibulo-Ocular Reflex acquisition, as found in neurophysiological studies. The effect of the different plasticity conditions, which change fast and slow dynamics, memory consolidation and, in general, learning capabilities of the cerebellar network, explains differences in the behavioral outcome.

Distributed cerebellar plasticity implements generalized multiple-scale memory components in real-robot sensorimotor tasks

The cerebellum plays a crucial role in motor learning and it acts as a predictive controller. Modeling it and embedding it into sensorimotor tasks allows us to create functional links between plasticity mechanisms, neural circuits and behavioral learning. Moreover, if applied to real-time control of a neurorobot, the cerebellar model has to deal with a real noisy and changing environment, thus showing its robustness and effectiveness in learning. A biologically inspired cerebellar model with distributed plasticity, both at cortical and nuclear sites, has been used. Two cerebellum-mediated paradigms have been designed: an associative Pavlovian task and a vestibulo-ocular reflex, with multiple sessions of acquisition and extinction and with different stimuli and perturbation patterns. The cerebellar controller succeeded to generate conditioned responses and finely tuned eye movement compensation, thus reproducing human-like behaviors. Through a productive plasticity transfer from cortical to nuclear sites, the distributed cerebellar controller showed in both tasks the capability to optimize learning on multiple time-scales, to store motor memory and to effectively adapt to dynamic ranges of stimuli.

Adaptive robotic control driven by a versatile spiking cerebellar network

The cerebellum is involved in a large number of different neural processes, especially in associative learning and in fine motor control. To develop a comprehensive theory of sensorimotor learning and control, it is crucial to determine the neural basis of coding and plasticity embedded into the cerebellar neural circuit and how they are translated into behavioral outcomes in learning paradigms. Learning has to be inferred from the interaction of an embodied system with its real environment, and the same cerebellar principles derived from cell physiology have to be able to drive a variety of tasks of different nature, calling for complex timing and movement patterns. We have coupled a realistic cerebellar spiking neural network (SNN) with a real robot and challenged it in multiple diverse sensorimotor tasks. Encoding and decoding strategies based on neuronal firing rates were applied. Adaptive motor control protocols with acquisition and extinction phases have been designed and tested, including an associative Pavlovian task (Eye blinking classical conditioning), a vestibulo-ocular task and a perturbed arm reaching task operating in closed-loop. The SNN processed in real-time mossy fiber inputs as arbitrary contextual signals, irrespective of whether they conveyed a tone, a vestibular stimulus or the position of a limb. A bidirectional long-term plasticity rule implemented at parallel fibers-Purkinje cell synapses modulated the output activity in the deep cerebellar nuclei. In all tasks, the neurorobot learned to adjust timing and gain of the motor responses by tuning its output discharge. It succeeded in reproducing how human biological systems acquire, extinguish and express knowledge of a noisy and changing world. By varying stimuli and perturbations patterns, real-time control robustness and generalizability were validated. The implicit spiking dynamics of the cerebellar model fulfill timing, prediction and learning functions.

Prostatic artery embolization in benign prostatic hyperplasia: preliminary results in 13 patients

AIM

The aim of the paper is to report the clinical outcome after prostatic artery embolisation (PAE) in 13 consecutive patients with benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS).

MATERIALS AND METHODS

From May 2012 to October 2013, we performed PAE in 13 consecutive patients (mean age 75.9 years) with BPH and LUTS and refractory to medical therapy; seven patients had an indwelling bladder catheter. Clinical follow-up (mean follow-up time 244 days) was performed using the international prostate symptoms score (IPSS), quality of life (QoL), the international index of erectile function (IIEF), blood prostatic specific antigen (PSA) testing and transrectal prostatic ultrasound (US) scan with volume and weight calculation at 3, 6 and 12 months. Pre-procedural CT angiography (CTA) was done for vascular mapping. Embolisation was performed using Embosphere (300-500 micron). Technical success was defined when selective prostatic arterial embolisation was completed in at least one pelvic side. Clinical success was defined when symptoms and quality of life were improved.

RESULTS

PAE was technically successful in 12/13 patients (92%). In one patient, PAE was not performed because of tortuosity and atherosclerosis of iliac arteries. PAE was completed bilaterally in 9/13 (75%) patients and unilaterally in three (27%). All patients removed the bladder catheter from 4 days to 4 weeks after PAE. We obtained a reduction in IPSS (mean, 17.1 points), an increase in IIEF (mean, 2.6 points), an improvement in Qol (mean, 2.6 points) and a volume reduction (mean, 28%) at 12 months.

CONCLUSIONS

Consistent with the literature, our experience showed the feasibility, safety and efficacy of PAE in the management of patients with LUTS related to BPH. PAE may play an important role in patients in whom medical therapy has failed, who are not candidates for surgery or transurethral prostatic resection (TURP) or refuse any surgical treatment. Larger case series and comparative studies with standard TURP can confirm the validity of the technique.

Endovascular treatment of visceral artery aneurysms and pseudoaneurysms: our experience

PURPOSE

The aim of this study was to analyse our 8 years of experience with endovascular treatment of visceral aneurysms and pseudoaneurysms.

MATERIALS AND METHODS

From January 2002 to September 2009, we used an endovascular approach to treat 30 patients (22 men, eight women) affected by aneurysm (n=18) or pseudoaneurysm (n=13) of the splenic (n=11), hepatic (n=6), renal (n=5), pancreaticoduodenal (n=3), left gastric (n=2), gastroduodenal (n=1), rectal (n=1) or middle colic (n=1) arteries and the coeliac axis (n=1). Of these, 26/31 were treated with metal coils, 3/31 with Cardiatis multilayer stent, 1/31 with a coated stent and 1/31 with coils and Amplatzer plug. Procedures were performed electively in 10/30 cases and during haemorrhage in 20/30 cases. Follow-up was performed clinically (cessation of bleeding) and at 1, 6 and 12 months by colour-Doppler ultrasound (CDUS) and computed tomography (CT) angiography.

RESULTS

In 31/31 aneurysms and pseudoaneurysms we obtained immediate exclusion. In four patients with aneurysm and in four with pseudoaneurysm, parenchymal ischaemia occurred; one was treated with surgical splenectomy. One patient with pseudoaneurysm of the coeliac axis died 10 days later because of new bleeding. During follow-up, all aneurysms and pseudoaneurysms remained excluded.

CONCLUSIONS

Percutaneous treatment is effective and safe, with a small number of complications, especially when compared with traditional surgery.

Accessing source information in analogical problem-solving

Several studies showed that people presented with source information fail to apply it to an analogous target problem unless they are instructed to use the source. Seven experiments were carried out to assess whether such a lack of spontaneous transfer occurs because individuals do not activate the source during the target task or because they do not realize the source-target relationship. Experiment 1 compared a condition in which the source was activated with no cue about the source-target connection to conditions in which subjects were informed about this connection. Results suggested that the lack of spontaneous transfer does not depend on failure in activating source information. Experiments 2, 3, and 4 were devised to falsify this finding by activating the source closer and closer to the target and by focusing participants' attention toward the relevant aspects of the source. Experiments 5, 6, and 7 were aimed at stressing source-target correspondences by introducing surface similarities. All experiments showed that the mere activation of the source does not facilitate analogical transfer. Results suggested that two processes should be distinguished in the access phase of analogical problem-solving: Source retrieval and identification of the source-target connection.

Suggesting strategies improves creative visual synthesis

An experiment assessed whether a figural or an interpretative strategy can enhance creative visual synthesis. 45 undergraduates were presented a set of simple figures and asked to imagine combining them to obtain a whole pattern corresponding to a creative product. In the figurative condition participants were instructed to combine figures in unusual ways; in the interpretative condition they were induced to look for unusual meanings embedded in the combinations; in the control condition no strategy was suggested. Results showed that certain strategies induced a more flexible visual synthesis.

Metacognitive knowledge about problem-solving methods

BACKGROUND

The effective application of a problem-solving method requires the knowledge of what task is relevant, what the abilities involved are and how much effort is needed. However, as yet too little is known about these metacognitive representations.

AIM

This study was aimed at describing beliefs about problem-solving methods and at assessing whether they vary according to the kind of method and of problem and are modified by psychological courses attended.

SAMPLE

Forty-six Italian undergraduates in psychology and 37 in non-psychological disciplines.

METHODS

Participants had to rate how frequently each of five problem-solving methods (free production, analogy, step-by-step analysis, visualisation and combining) is employed and how effective and easy each one is to apply. Ratings were requested for interpersonal, practical and study problems. Participants were also asked to identify which abilities they thought would be involved in each method.

RESULTS

According to students' ratings, the most frequently used problem-solving method was analogy, which was also considered the easiest method to apply, whereas step-by-step analysis and combining were considered the most difficult. Problem-solving techniques were perceived as being relevant above all for practical problems, whereas they were conceived as less suitable for interpersonal problems. For study problems the most relevant strategy was step-by-step analysis. Students were aware of the abilities relevant to each problem-solving method.

CONCLUSIONS

Undergraduates both in psychology and non-psychological disciplines can identify some critical features in the methods used to solve problems, even though some misconceptions emerged. Since metacognition plays a causal role in problem-solving, trainers should take into account trainees' folk representations of problem-solving strategies.

The Verbalizer-Visualizer Questionnaire: a review

The psychometric properties of Richardson's 1977 Verbalizer-Visualizer Questionnaire have been studied by analyzing papers in which this questionnaire was employed. Such review showed that the Verbalizer-Visualizer Questionnaire does not measure a unidimensional construct and does not predict the actual use of mental imagery in thinking. Further, a lack of long-term reliability of the questionnaire emerged. In conclusion, use of the questionnaire to assess the verbal-visual cognitive style appears questionable.

Creative synthesis of visual images is not associated with individual differences

50 undergraduates were tested on a mental synthesis task aimed at producing creative visual patterns and were administered three questionnaires measuring imagery vividness and control. Analysis did not support a relationship between scores on visual synthesis and imagery and showed that neither kind of score was influenced by sex and studies attended.