The symbolic working memory system

The capacity of the brain in maintenance of task-relevant information over a short period of time is known to be crucial for performing a wide range of activities from low-level perception-action routines in lower animals to high-level intellectual tasks in human. “Working memory” is the common term that has been used among different communities to refer to the manifestation of this feature across different domains. However, despite this common agreement, dominant theoretical paradigms for describing working memory management systems in the domains of low-level/perception-action and high-level/intellectual functions follow drastically different principles: embedded and distributed in the low-level domain, disembodied and centralized in the high-level domain. Given that the human cognitive system functions at both levels in different contexts simultaneously this question arises whether indeed there are two types of working memory systems running in parallel under two different operational principles in human brain or, a more parsimonious account can explain all different manifestations of working memory in all domains. In attempt to achieve a more parsimonious account, a theory is developed for functioning of working memory in the context of high-level and intellectual domain which accounts for information management during those tasks that feature symbolic information processing. This effort was partially motivated by theoretical inconsistencies and biological/evolutionary implausibility of standard models of working memory in cognitive psychology with centralized executive paradigm. The proposed framework demonstrates how novel assemblage of embedded schemas in existing sensorimotor systems may supply a system for management of symbolically represented sensory and motor information serving intellectual tasks. In the proposed framework, strategic and evolutionarily-constrained reuse of sensorimotor resources for management of respectively spatially-organized and temporally-sensitive information support random access and serial access schemas for management of symbolic information. Through grounding access schemas for management of symbolic information in sensorimotor systems we are able to predict ramifications of working memory management during the performance of mental tasks at behavioral and neural levels. A detailed example in applying this methodology in well-studied cases of forward and backward recall tasks will be presented with additional computational modeling and the results of simulations. Our systematic approach in mapping spatial/temporal characteristics of sensorimotor systems onto access modes provides a symbolic interface to other frameworks and architectures for describing the symbolically-intelligent mind. Proposed framework provides for the first time a neurally-grounded and sensorimotor-based account for management of symbolic information with embodied cognition prospects with opportunities for experimental validations and applications. Proposed theory offers ample opportunities for experimental validations and predicts novel sources of working memory for symbolic tasks. Moreover, through providing a mechanistic account for management of working memory, the proposed theory, defines a practical framework for optimization of working memory resources for performing mental tasks which has potential educational consequences in measuring IQ and optimal designing of mental operations. Mechanistic specifications of the model about details of interactions between functioning of visuospatial systems as the main supplier of random access to symbolic working memory in normal subjects has allowed a number of predictions that are validated in experimental studies. Four chapters in part of this dissertation report the results of experimental studies under four different experimental paradigms. These studies have been able to generate significant result in support of proposed theory.