No description available.

Biophysical simulations of memory must choose which aspects of known neurophysiology and neuroanatomy to model. Relevant aspects were constrained by functional requirements determined for on-line acquisition in context dependent memory, memory that is retrieved by contextual cues. In an on-line task, the protocol of data presentation and the tunes at which encoding or retrieval in memory is needed are not predetermined. A sequence of neuronal spike patterns representing items may be presented only once. Yet, episodic memory of the sequence immediately encodes the temporal context of familiar items, a process known to depend on hippocampal function. For this, interference caused by overlapping spike patterns must be avoided, a requirement that suggested the relevance of coincidental spiking. Overlap in the input to the hippocampus was reduced by recruiting such spikes in a model of encoding in dentate gyrus. Durable encoding is required in the hippocampus, since hippocampal damage can cause retrograde amnesia in context dependent memory that spans years. Long-lasting synaptic changes involved modeling relevant neurophysiology concerning protein production elicited by the spaced reactivation of spike patterns. The likelihood of reactivation was increased by the well-known process of long-term potentiation of synaptic transmission. Such potentiation is elicited when a presynaptic spike precedes a postsynaptic spike within a specific time window repeatedly. The intervals in a sequence of spike patterns must be compressed and the sequence repeated, requirements that were achieved with a model of short-term memory based on persistent spiking. Retrieval may be concurrent with these encoding processes due to effects of different phases of a brain rhythm at theta frequency (3-12 Hz) that modulate transmission and plasticity. A model of short-term memory by Lisman and Idiart (Science 267:1512-15), extended by Jensen et al. (Learning and Memory 3:243

The idea that the limbic system is involved in the mediation of emotional and motivational behavior is one which is now quite common in the literature. Since the early work of Klüver and Bucy (1937) and Papez (1937), a great deal of experimentation has centered on this particular region of the brain. There now appears to be at least some general agreement on the gross changes in behavior which follow lesions and stimulation in the various areas of the limbic system. But in most cases precisely how these general changes in emotionality affect behavior in specifie circumstances is still not known, and how the limbic system functions, in whole or in part, to modify behavior is far from clear. [...]

Electrical stimulation of the brain (ESB) of unanesthetized animals offers a powerful technique for the study of brain structure and function. The method was originally employed by physiologists interested in determining the functional organization of the nervous system (Hess, 1957; Ranson 5 Magoun, 1939). But recently, psychologists have utilized stimulation with the object of determining the role of the central nervous system in the control of behavior. [...]

A test of preference for accepting or rejecting electrical stimulation of the rat's septal area revealed individual differences: "positive" reactors sought the stimulation; "negative" reactors escaped from it. All animals escaped from electrical stimulation of the dorsal tegmental area. [...]

Since the cortex is the highest integrating center in the mammal and the most accessible, it is natural that it should have been the object of much experimentation. One way of investigating the functions of the cortex is to remove it entirely, and study the behavior of the decorticate animal. [...]

Recent research has suggested disrupted interactions between brain regions may contribute to some of the symptoms of motor disorders such as Parkinson’s Disease (PD). It is therefore important to develop models for inferring brain functional connectivity from data obtained through non-invasive imaging technologies, such as functional magnetic resonance imaging (fMRI). The complexity of brain activities as well as the dynamic nature of motor disorders require such models to be able to perform complex, large-scale, and dynamic system computation. Traditional models proposed in the literature such as structural equation modeling (SEM), multivariate autoregressive models (MAR), dynamic causal modeling (DCM), and dynamic Bayesian networks (DBNs) have all been suggested as suitable for fMRI data analysis. However, they suffer from their own disadvantages such as high computational cost (e.g. DBNs), inability to deal with non-linear case (e.g. MAR), large sample size requirement (e.g. SEM), et., al. In this research, we propose applying Probabilistic Boolean Network (PBN) for modeling brain connectivity due to its solid stochastic properties, computational simplicity, robustness to uncertainty, and capability to deal with small-size data, typical for fIVIRI data sets. Applying the proposed PBN framework to real fMRI data recorded from PD subjects enables us to identify statistically significant abnormality in PD connectivity by comparing it with normal subjects. The PBN results also suggest a mechanism of evaluating the effectiveness of L-dopa, the principal treatment for PD. In addition to PBNs’ promising application in inferring brain connectivity, PBN modeling for brain ROTs also enables researchers to study dynamic activities of the system under stochastic conditions, gaining essential information regarding asymptotic behaviors of ROTs for potential therapeutic intervention in PD. The results indicate significant difference in feature states between PD patients and normal subjects. Hypothesizing the observed feature states for normal subject as the desired functional states, we further explore possible methods to manipulate the dynamic network behavior of PD patients in the favor of the desired states from the view of random perturbation as well as intervention. Results identified a target ROT with the best intervention performance, and that ROl is a potential candidate for therapeutic exercise.

This thesis contains two studies. The first study consisted of a prospective, randomized, clinical trial involving twenty-five client-owned dogs with intracranial disease. Each dog was randomly assigned to receive propofol or isoflurane for maintenance of anesthesia, without premedication. All dogs received propofol IV to effect, were intubated and mechanically ventilated (end-tidal carbon dioxide [ETCO2] 30-35 mmHg). Temperature and cardiac output were measured pre- and post-magnetic resonance imaging (MRI). Scores for mentation, neurological status, maintenance, and recovery were obtained. Pulse oximetry, end tidal gases, arterial blood pressure (AP), heart rate (HR) and requirements for dopamine administration to maintain mean AP > 60 mmHg were recorded throughout anesthesia. Cardiac index was higher, while HR was lower, with propofol in dogs younger than 5 years. Dogs receiving isoflurane were 14.7 times more likely to require dopamine. Sedation and maintenance scores and temperature were not different. Mean and diastolic AP were higher in the propofol group. Recovery scores were better with propofol. Change in neurological score from pre- to post-anesthesia was not different between treatments. In the second study, blood and CSF were collected from 11 dogs with intracranial disease after MRI (Group ID-MRI), in 10 healthy dogs post-MRI (Group H-MRI), and in 39 healthy dogs after induction of anesthesia (Group H-Anesth). Groups ID-MRI and H-MRI were induced to anesthesia with propofol, IV to effect, and maintained on isoflurane or propofol. Dogs in H-Anesth were premedicated with acepromazine and hydromorphone, induced with propofol or thiopental, IV to effect, and maintained on isoflurane. Neurologic scores (NS) and sedation scores (SS) were assessed pre-anesthesia in ID-MRI dogs. There was a tendency for higher cerebrospinal fluid lactate (CSFL) in ID-MRI than H-MRI or H-Anesth (p = 0.12). There was agreement between CSFL and plasma lactate (PL) in ID-MRI dogs (p = 0.007), but not in H-MRI (p = 0.45) or H-Anesth (p = 0.15). Of the ID-MRI dogs, those with worse NS had higher CSFL (r2 = 0.44). Propofol showed some advantages to isoflurane in this patient population for maintenance of blood pressure and recovery. The results of the second study warrant further investigation. / OVC Pet Trust

No description available.

No description available.