On the interplay between working memory consolidation and attentional selection in controlling conscious access: parallel processing at a cost—a comment on ‘The interplay of attention and consciousness in visual search, attentional blink and working memory consolidation’

Abstract

Theories of human cognition generally agree in assuming the existence of a fundamental limit in information processing, but these theories are challenged by findings that appear to circumvent these limitations. We argue that theories are needed that offer a principled account of why the limitations become manifest in some cases but not others.Raffone et al.[1] present a comprehensive theoretical framework that links behavioural effects, such as the attentional blink (AB), visual search and inattentional blindness, to an overarching theory of the neurobiological substrates of consciousness and attention. Central to their model is the global workspace (GW), which is predicated on the notion that working memory, attention and consciousness arise from a network of neurons that can only focus on one representation at any time. This inability to simultaneously process multiple stimuli has been suggested to explain the AB as well as visual search behaviour.However, there is mounting evidence that the brain is capable of encoding multiple items into short-term memory (STM) at once, such as lag-1 sparing, in which two targets are apparently encoded together [2]. Owing to its strictly winner-take-all behaviour, previous GW-based computational accounts of the AB [3,4] had particular difficulty explaining this effect.Raffone et al.[1] respond to this evidence by attempting to reconcile the GW theory with such evidence. The theory of attentional control (TAC) boldly pushes the unitary nature of cognition even further by proposing that STM encoding and attentional selection also time-share central processing capacity, so that only one of them can occur at a time. TAC permits lag-1 sparing through an intermediate buffer that can hold multiple items concurrently, as they await an opportunity to be encoded into STM. Thereby, the AB is not caused by direct competition between target one (T1) and T2, but rather by competition between attentional selection and STM encoding.In this respect, TAC is similar to computational models that we have previously proposed [5][6][7]. In the episodic Simultaneous Type Serial Token model (eSTST), ongoing consolidation has an inhibitory effect on attentional selection. Furthermore, like TAC, we proposed that attention can remain engaged over several consecutive targets to produce spreading of sparing (see [8] and also figure 1).However, the theories differ dramatically in that the eSTST model permits parallel encoding of multiple targets. Furthermore, attentional selection is possible during encoding; it is just reduced in strength. We argue that permissiveness of parallel processing is essential to accommodate the full range of available data concerning the attentional blink. In particular, there are two specific empirical benchmarks that seem unattainable by TAC.

Rapid switching and complementary evidence accumulation enable flexibility of an all-or-none global workspace for control of attentional and conscious processing: a reply to Wyble et al .

“…First of all, we note that the TAC as described in Raffone et al [6], in spite of the claims in Wyble et al's [7] comment, is in principle neutral with respect to serial versus parallel consolidation in WM. These issues are not explicitly addressed in the current, first formulation of the theory, which is to be developed further in order to account for a broader set of data, including divided attention and multitasking paradigms (e.g.…”

“…TAC provides a unified neurocognitive account of several phenomena associated with visual search, attentional blink (AB), and working memory (WM) consolidation. Wyble et al [7] commented on our TAC proposal, focusing on WM consolidation and AB effects.…”

“…With respect to WM consolidation, which corresponds to short-term memory (STM) encoding in their framework, Wyble et al [7] observe that there is mounting evidence for parallel processing of multiple targets. In the lag-1 sparing condition of the AB paradigm, two targets are apparently encoded together [8].…”

“…Instead, in their previously proposed Episodic Simultaneous Type Serial Token (eSTST) model [10 -12], competition for resources between encoding in STM and attentional selection is not winner-take-all but leads to attenuation of these processes. Wyble et al [7] emphasize that, unlike TAC, the eSTST model permits parallel encoding of multiple targets into STM.…”

“…[2]) face particular difficulties in accounting for such evidence, given that their processing limitations are based on a strict winner-take-all principle (however, see [9] for a neural model enabling parallel target encoding in the GW). Wyble et al [7] acknowledge that while retaining the notion of GW, TAC attempts to go beyond such models, in particular by introducing an 'intermediate buffer' mechanism. This mechanism operates in tandem with a winner-take-all competition in the GW between higher order executive routers for attentional selection and consolidation in WM.…”