Howard Bowman

The Simultaneous Type, Serial Token Model of Temporal Attention and Working Memory

A detailed description of the simultaneous type, serial token (ST2) model is presented. ST2 is a model of temporal attention and working memory that encapsulates 5 principles: (a) M. M. Chun and M. C. Potters (1995) 2-stage model, (b) a Stage 1 salience filter, (c) N. G. Kanwishers (1987, 1991) types-tokens distinction, (d) a transient attentional enhancement, and (e) a mechanism for associating types with tokens called the binding pool. The authors instantiate this theoretical position in a connectionist implementation, called neural-ST2, which they illustrate by modeling temporal attention results focused on the attentional blink (AB). They demonstrate that the ST2 model explains a spectrum of AB findings. Furthermore, they highlight a number of new temporal attention predictions arising from the ST2 theory, which are tested in a series of behavioral experiments. Finally, the authors review major AB models and theories and compare them with ST2.

The Attentional Blink Provides Episodic Distinctiveness : Sparing at a Cost

The attentional blink (J. E. Raymond, K. L. Shapiro, & K. M. Arnell, 1992) refers to an apparent gap in perception observed when a second target follows a first within several hundred milliseconds. Theoretical and computational work have provided explanations for early sets of blink data, but more recent data have challenged these accounts by showing that the blink is attenuated when subjects encode strings of stimuli (J. Kawahara, T. Kumada, & V. Di Lollo, 2006; M. R. Nieuwenstein & M. C. Potter, 2006; C. N. Olivers, 2007) or are distracted (C. N. Olivers & S. Nieuwenhuis, 2005) while viewing the rapid serial visual presentation stream. The authors describe the episodic simultaneous type, serial token model, a computational account of encoding visual stimuli into working memory that suggests that the attentional blink is a cognitive strategy rather than a resource limitation. This model is composed of neurobiologically plausible elements and simulates the attentional blink with a competitive attentional mechanism that facilitates the formation of episodically distinct representations within working memory. In addition to addressing the blink, the model addresses the phenomena of repetition blindness and whole report superiority, producing predictions that are supported by experimental work.

Attentional Episodes in Visual Perception

Is ones temporal perception of the world truly as seamless as it appears? This article presents a computationally motivated theory suggesting that visual attention samples information from temporal episodes (episodic simultaneous type/serial token model; Wyble, Bowman, & Nieuwenstein, 2009). Breaks between these episodes are punctuated by periods of suppressed attention, better known as the attentional blink (Raymond, Shapiro, & Arnell, 1992). We test predictions from this model and demonstrate that participants were able to report more letters from a sequence of 4 targets presented in a dense temporal cluster than from a sequence of 4 targets interleaved with nontargets. However, this superior report accuracy comes at a cost in impaired temporal order perception. Further experiments explore the dynamics of multiple episodes and the boundary conditions that trigger episodic breaks. Finally, we contrast the importance of attentional control, limited resources, and memory capacity constructs in the model.

Viewpoint consistency in ODP

Open Distributed Processing (ODP) is a joint ITU/ISO standardisation framework for constructing distributed systems in a multi-vendor environment. Central to the ODP approach is the use of viewpoints for specification and design. Inherent in any viewpoint approach is the need to check and manage the consistency of viewpoints. In previous work we have described techniques for consistency checking, refinement, and translation between viewpoint specifications, in particular for LOTOS and Z/Object-Z. Here we present an overview of our work, motivated by a case study combining these techniques in order to show consistency between viewpoints specified in LOTOS and Object-Z.

A Formal Framework for Viewpoint Consistency

Multiple Viewpoint models of system development are becoming increasingly important. Each viewpoint offers a different perspective on the target system and system development involves parallel refinement of the multiple views. Viewpoints related approaches have been considered in a number of different guises by a spectrum of researchers. Our work particularly focuses on the use of viewpoints in Open Distributed Processing (ODP) which is an ISO/ITU standardisation framework. The requirements of viewpoints modelling in ODP are very broad and, hence, demanding. Multiple viewpoints, though, prompt the issue of consistency between viewpoints. This paper describes a very general interpretation of consistency which we argue is broad enough to meet the requirements of consistency in ODP. We present a formal framework for this general interpretation; highlight basic properties of the interpretation and locate restricted classes of consistency. Strategies for checking consistency are also investigated. Throughout we illustrate our theory using the formal description technique LOTOS. Thus, the paper also characterises the nature of and options for consistency checking in LOTOS.

Oscillations and Episodic Memory: Addressing the Synchronization/Desynchronization Conundrum.

Brain oscillations are one of the core mechanisms underlying episodic memory. However, while some studies highlight the role of synchronized oscillatory activity, others highlight the role of desynchronized activity. We here describe a framework to resolve this conundrum and integrate these two opposing oscillatory behaviors. Specifically, we argue that the synchronization and desynchronization reflect a division of labor between a hippocampal and a neocortical system, respectively. We describe a novel oscillatory framework that integrates synchronization and desynchronization mechanisms to explain how the two systems interact in the service of episodic memory.

A Decision Procedure and Complete Axiomatization of Finite Interval Temporal Logic with Projection

This paper presents a complete axiomatization for propositional interval temporal logic (PITL) with projection. The axiomatization is based on a tableau decision procedure for the logic, which in turn is founded upon a normal form for PITL formulae. The construction of the axiomatization provides a general mechanism for generating axiomatizations thus: given a normal form for a new connective, axioms can be generated for the connective from the tableau construction using that normal form. The paper concludes with a discussion of aspects of compositionality for PITL with projection.

Dissociating Local and Global Levels of Perceptuo-Motor Control in Masked Priming.

Masked prime stimuli presented near the threshold of conscious awareness affect responses to subsequent targets. The direction of these priming effects depends on the interval between masked prime and target. With short intervals, benefits for compatible trials (primes and targets mapped to the same response) and costs for incompatible trials are observed. This pattern reverses with longer intervals. We argue (a) that these effects reflect the initial activation and subsequent self-inhibition of the primed response, and the corresponding inhibition and subsequent disinhibition of the nonprimed response, and (b) that they are generated at dissociable local (within response channels) and global (between channels) levels of motor control. In two experiments, global-level priming effects were modulated by changing the number of response alternatives, whereas local-level effects remained unaffected. These experiments suggest that low-level motor control mechanisms can be successfully decomposed into separable subcomponents, operating at different levels within the motor system.

A neural network model of inhibitory processes in subliminal priming

Masked priming experiments have revealed a precise set of facilitatory and inhibitory visuomotor control processes. Most notably, inhibitory effects have been identified in which prime-target compatibility induces performance costs and prime-target incompatibility induces performance benefits. We argue that this profile of data is commensurate with an “emergency braking mechanism”, whereby responses can be retracted as a result of changing sensory evidence. The main contribution of this paper is to provide a neural network-based explanation of this phenomenon. This is obtained through the use of feedforward inhibition to implement backward masking, lateral inhibition to implement response competition, and opponent processing mechanisms to implement response retraction. Although the model remains simple, it does a very good job of reproducing the available masked priming data. For example, it reproduces a large spectrum of reaction time data across a number of different experimental conditions. Perhaps most notably, however, it also reproduces lateralized readiness potentials that have been recorded while subjects perform different conditions. In addition, it provides a concrete set of testable predictions.

FDTs for ODP

Abstract This paper discusses the use and integration of formal techniques into the Open Distributed Processing (ODP) standardization initiative. The ODP reference model is a natural progression from OSI. Multiple viewpoints are used to specify complex ODP systems. Formal methods are playing an increasing role within ODP. We provide an overview of the ODP reference model, before discussing the ODP requirements on FDTs, and the role such techniques play. Finally, we discuss the use of formalisms in the central problem of maintaining cross viewpoint consistency.