We discuss the role of synchrony of activationin higher-level cognitive processes. Inparticular, we analyze the question of whethersynchrony of activation provides a mechanismfor compositional representation in neuralsystems. We will argue that synchrony ofactivation does not provide a mechanism forcompositional representation in neural systems.At face value, one can identify a level ofcompositional representation in the models thatintroduce synchrony of activation for thispurpose. But behavior in these models isalways produced by means conjunctiverepresentations in the form of coincidencedetectors. Therefore, models that rely onsynchrony (...) of activation lack the systematicityand productivity of true compositional systems.As a result, they cannot distinguish betweentype and token representations, which resultsin misrepresentations of spatial relations andpropositions. Furthermore, higher-levelcognitive processes will likely integrateinformation from widely distributed areas inthe brain, which puts severe restrictions onthe underlying neural dynamics if synchrony ofactivation is to play a role in theseprocesses. We will briefly discuss theserestrictions in the case of feature binding invisual cognition. (shrink)
Cognitive agents are dynamical systems but not quantitative dynamical systems. Quantitative systems are forms of analogue computation, which is physically too unreliable as a basis for cognition. Instead, cognitive agents are dynamical systems that implement discrete forms of computation. Only such a synthesis of discrete computation and dynamical systems can provide the mathematical basis for modeling cognitive behavior.
Various issues concerning the neural blackboard architectures for combinatorial structures are discussed and clarified. They range from issues related to neural dynamics, the structure of the architectures for language and vision, and alternative architectures, to linguistic issues concerning the language architecture. Particular attention is given to the nature of true combinatorial structures and the way in which information can be retrieved from them in a productive and systematic manner.
_Abstract_: This article discusses the unity of cognitive science that seemed to emerge in the 1950s, based on the computational view of cognition. This unity would entail that there is a single set of mechanisms (i.e. algorithms) for all cognitive behavior, in particular at the level of productive human cognition as exemplified in language and reasoning. In turn, this would imply that theories in psychology, and cognitive science in general, would consist of algorithms based on symbol manipulation as found in (...) digital computing. However, a number of developments in recent decades cast doubt on this unity of cognitive science. Also, there are fundamental problems with the claim that cognitive theories are just algorithms. This article discusses some of these problems and suggests that, instead of unified theories of cognition, specific mechanisms for cognitive behavior in specific cognitive domains could be needed, with architectures that are tailor-made for specific forms of implementation. A sketch of such an architecture for language is presented, based on modifiable connection paths in small-world like network structures. _Keywords_: Connection Paths; Control of Activation; Small-world Networks; Symbol Manipulation; Unity of Cognition _Dalle teoria unificate della cognizione a quelle specifiche_ _Riassunto_: Questo articolo discute l’unità della scienza cognitiva che sembrava emergere negli Anni ’50 e che era basata su una concezione computazionale della cognizione. Questa unità prevedeva l’esistenza di un singolo insieme di meccanismi (algoritmi) per tutti i comportamenti cognitivi, in particolare al livello della cognizione umana produttiva come, per esempio, linguaggio e ragionamento. A sua volta ciò implicava che le teorie psicologiche e, più in generale della scienza cognitiva, prevedessero algoritmi basati sulla manipolazione di simboli come nella computazione digitale. E, tuttavia, diversi sviluppi degli ultimi decenni hanno messo in dubbio questa unità della scienza cognitiva. Affermare che le teorie cognitive sarebbero solo algoritmi presenta problemi di fondo. Questo articolo discute alcuni di questi problemi, suggerendo che, invece di teorie della cognizione unificata, si potrebbe aver bisogno di meccanismi specifici per il comportamento cognitivo in specifici domini cognitivi, con architetture ritagliate per specifiche forme di implementazione. Questo articolo presenta uno schizzo di una simile architettura per il linguaggio, basata su vie di connessione modificabili in piccoli mondi come le strutture di reti. _Parole chiave_: Vie di connessione; Controllo dell’attivazione; Reti di piccoli mondi; Manipolazione di simboli; Unità della cognizione. (shrink)
We discuss a visual blackboard architecture that could be involved in imagery. In this architecture, networks that process identity information interact with networks that process location information, in a manner that produces structural (compositional) forms of representation. Architectures of this kind can be identified in the visual cortex, but perhaps also in prefrontal cortex areas related with working memory.
The idea of representing words with cell assemblies is very appealing. However, syntactic sequences need to be represented as well. This cannot be done by using the activity levels of assemblies. Instead, structural relations and operations between assemblies are needed to achieve serial order in syntactic word strings.