Raymond Pavloski

The utility of currently available cortical prosthetic vision systems is disappointing. The essential features of a neuromorphic device that is predicted to enhance vision provided by available systems follow from a hypothesis which states that the objective and subjective aspects of cortical prosthetic vision jointly constitute patterns that emerge from specified synaptic interactions. The research reported here completes several required steps in developing an emulation of this device: (1) replication of small-scale simulations that are consistent with the hypothesis using the NEST (Écublens, Vaud, Switzerland) simulator, which can also be used for full-scale network emulation by a neuromorphic computer; (2) testing whether results consistent with the hypothesis survive increasing the scale and duration of simulations; (3) establishing a method that uses numbers of spikes produced by network neurons to report the number of phosphenes produced by cortical stimulation; and (4) simulating essential functions of a neuromorphic device which is predicted to enhance current prosthetic systems. NEST simulations replicated early results and increasing their scale and duration produced results consistent with the hypothesis. A decision function created using multinomial logistic regression correctly reported the expected number of phosphenes for three sets of 2080 spike number distributions in which half of each set arises from simulations expected to yield continuous visual forms by engaging a desired visual geometry. A process for modulating electrical stimulation amplitude based on intermittent population recordings that is predicted to produce desired visual geometries was successfully simulated. Implications of these results for future research are discussed.

Sense element engagement theory explains how neural networks produce cortical prosthetic vision. A major prediction of the theory can be tested by developing a device which is expected to enable perception of continuous forms in altered visual geometries. The research reported here completes several essential steps in developing this device: (1) replication of simulations that are consistent with the theory using the NEST simulator, which can also be used for full-scale network emulation by a neuromorphic computer; (2) testing whether results consistent with the theory survive increasing the scale and duration of simulations; (3) establishing a method that uses numbers of spikes produced by network neurons to report the number of phosphenes produced by cortical stimulation; and (4) simulating essential functions of the prosthetic device. NEST simulations replicated early results and increasing their scale and duration produced results consistent with the theory. A decision function created using multinomial logistic regression correctly classified the expected number of phosphenes for 2080 spike number distributions for each of three sets of data, half of which arise from simulations expected to yield continuous visual forms on an altered visual geometry. A process for modulating electrical stimulation amplitude based on intermittent population recordings that is predicted to produce continuous visual forms was successfully simulated. The classification function developed using logistic regression will be used to tune this process as the scale of simulations is further increased.

Demonstrating that an understanding of how neural networks produce a specific quality of experience has been achieved would provide a foundation for new research programs and neurotechnologies. The phenomena that comprise cortical prosthetic vision have two desirable properties for the pursuit of this goal: 1) Models of the subjective qualities of cortical prosthetic vision can be constructed; and 2) These models can be related in a natural way to models of the objective aspects of cortical prosthetic vision. Sense element engagement theory portrays the qualities of cortical prosthetic vision together with coordinated objective neural phenomena as constituting sensible spatiotemporal patterns that are produced by neural interactions. Small-scale neural network simulations are used to illustrate how these patterns are thought to arise. It is proposed that simulations and an electronic neural network (ENN) should be employed in devising tests of the theory. Large-scale simulations can provide estimates of parameter values that are required to construct an ENN. The ENN will be used to develop a prosthetic device that is predicted by the theory to produce visual forms in a novel fashion. According to the theory, confirmation of this prediction would also provide evidence that this ENN is a sentient device.

A lattice model is developed to clarify the concept of latent or intrinsic emergent order. This is motivated by the theory of primary mental models, which proposes that conscious experience is an emergent macrostate of its neural substrate characterized by such order. Elements of the model interact to reduce an energy that depends on the relation-ships among elements comprising clusters rather than on the states of the elements themselves. Simulations confirm that macroscopic order emerges: two attractors develop at a critical noise level, and the macrostate predicts its own future. Descriptive analyses demonstrate that this macrostate possesses latent order: each emergent state is characterized by degenerate state vectors that are nearly orthogonal, and singular value decomposition of a matrix of frequencies of occurrence of states of the overlapping clusters of elements occurring in the attractor states detects two latent dimensions that reveal the model's two attractors.

The control system mode of analysis of organism-environment interactions is described and used to derive an explanation of cardiovascular reactivity. This description reveals that a negative feedback control system continuously realizes a goal or purpose over time by producing output that negates the effects of unpredictable and uncontrollable disturbances on a physical variable corresponding to that purpose. Data from tracking experiments fit the control system analysis, but cannot be described by S-O-R analyses or by cognitive analyses that, unlike the control system analysis, do not correctly introduce physical time. Simple computer simulations of negative feedback control systems produce data that are almost perfectly correlated with each subject's behavior over time--these models behave. The existence of consistent behavioral results despite uncontrollable and unpredictable influences, the simple requirements for a negative feedback system, and the identification of continuously varying purposes as representing the unfolding of behavioral events over time argue for the testable hypothesis that most behavior is produced by negative feedback control. It is suggested that error in the operation of negative feedback control systems modulates cardiac performance. The ability of control systems to behave gives this explanation advantages over other theories of reactivity. A program for testing this explanation is described.

McKinney et al. (1980) reported large-magnitude reductions in heart rate (HR) from resting baseline levels, employing shaping and fading techniques and a reinforcement program in which a secondary reinforcer was awarded both contingently and immediately during training. The four male subjects in this group showed significantly greater HR decreases than a group of four males receiving beat-by-beat analogue HR feedback. The present study compared decreases in HR in 20 male subjects receiving the contingently faded biofeedback procedure to those shown by 10 male subjects for whom reinforcement was contingent on vigilant observation of a visual display, and independent of HR. The former group showed significantly greater decreases in HR that could not be attributed to elevated baseline levels. However, the decreases in HR were not as large as those reported by McKinney et al. (1980). It is argued that future research should assess variables contributing to individual differences in performance.

Tested the hypothesis that discrimination of a response automatically leads to control over that response. 24 Ss participated in 2 experiments, with occipital alpha EEG activity being the discriminative stimulus. Results indicate that holding the probabilities of alpha and nonalpha discrimination trials near .50 results in an absence of learning curves, but leaves open the possibility that sophisticated Ss are capable of discriminating alpha and nonalpha activity. However, learning to increase percent-time nonalpha or decrease percent-time alpha with respect to baseline levels by means of EEG-contingent stimulation provides Ss with the ability to suppress percent-time alpha in the absence of feedback. Interview information indicates that Ss most often acquired their control of alpha activity during feedback by a specific strategy, and then used the strategy during the stimulus-control tests. (33 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Reports an experiment based on the idea that a joint manipulation of both cognitive and physiological (i.e., alpha EEG) variables would provide information required for an explication of the process involved in subjective mood change. 40 Ss, mostly high school students, participated. Three main variables were considered. First, the instructions were designed to induce a "set" or expectations for either positive or negative changes in subjective mood. Second, the type of feedback (alpha or not alpha) was varied, contingent on the presence or absence of alpha activity. Third, an estimate of each individual's baseline alpha density was obtained, and on this basis Ss were classified as high- or low-baseline. Baseline alpha density, alpha density during training, and subjective mood were all considered as continuous variables. Results indicate that biofeedback of the cortical alpha rhythm is neither a sufficient nor a necessary condition for changes in subjective mood. In addition, the type of instructions designed to set Ss for alterations in subjective states is predictive of changes in subjective state reported during alpha biofeedback training, as well as of success at controlling and changing EEG during feedback training. These data permit a direct examination of the actual relationship of EEG changes to changes in subjective mood state. Both positive and negative subjective experiences can be associated with increases in alpha activity. (33 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Operant conditioning of the sensorimotor rhythm of the human electroencephalogram with time-outs contingent on epileptiform activity reduces epileptic seizure rates in patients whose seizures are not well controlled by medication. A comparison of this procedure with time-out training alone demonstrates that operant conditioning of the sensorimotor rhythm is neither necessary nor sufficient for seizure reduction.