The LIDA model

05/08/2011 by admin.

Madl, Baars and Franklin have proposed a model of cognition they call LIDA (Learning Intelligent Distribution Agent). It is a series of cycles, each cycle preforming an ‘atom’ of cognition. (see citation below) A series of these ‘atoms’ would make up the performance of a cognitive task (problem solving, deliberation, volitional decision making for example). LIDA is an elaboration of the global workspace theory but takes under its wing other theories – they site embodied cognition, perceptual symbol systems, working memory, memory by affordances, long-term working memory, transient episodic memory, H-CogAff cognitive architecture, and Action Selection paradigm as contributing.

Here is their description of the Global Workspace idea:

The global workspace theory can be thought of as ‘‘… a theater of mental functioning. Consciousness in this metaphor resembles a bright spot on the stage of immediate memory, directed there by a spotlight of attention under executive guidance. Only the bright spot is conscious, while the rest of the theater is dark and unconscious’’. In case of sensory consciousness, the stage corresponds to the sensory projection areas of the cortex, its activation coming either from senses or from internal sources. After a conscious sensory content is established, it is distributed to a decentralized ‘‘audience’’ of expert networks sitting in the darkened theater. Thus, the primary functional purpose of consciousness is to integrate, provide access, and coordinate the functioning of very large numbers of specialized networks that otherwise operate autonomously. In the neuroscientific study of consciousness, this idea of consciousness having an integrative function has proven very useful, and is supported by much recent evidence.

This global workspace is where consciousness occurs, just once in each cognitive cycle. The cycle goes through perceive – understand – act and back to perceive. They strongly state that in LIDA these three types of process run continuously and are not confined to a particular block of time. But consciousness does occur only once and for a limited time in each cycle.

The most impressive aspect of this paper for me was their review of many published measurements of timing in the brain. The LIDA cycle is based on the theta rhythm and the gamma rhythm synchronizations phase locked to it. In the end they settle on a timing for a cycle based on their review:

t0 stimulus start

perception (80-100ms)

understanding (perception & understanding together = unconscious processing)

unconscious processing (260-280ms)

conscious broadcasting

action selection (60-110ms) (cannot start before conscious broadcasting)

total cognitive cycle (260-390ms)

I may return to this paper in future postings as there are some very interesting corners in it. This model has consciousness as distinct frames, however they do allow for elements from previous frames to linger. It also has a number of memory stores in its scheme: sensory memory, perceptual associative memory, transient episodic memory, declarative memory, procedural memory, sensory-motor memory. These are for future postings.

The LIDA model has been stimulated by computer programs and tested in very simple scenarios in preparation for more elaborate stimulations.

Here is the abstract :

We propose that human cognition consists of cascading cycles of recurring brain events. Each cognitive cycle senses the current situation, interprets it with reference to ongoing goals, and then selects an internal or external action in response. While most aspects of the cognitive cycle are unconscious, each cycle also yields a momentary ‘‘ignition’’ of conscious broadcasting. Neuroscientists have independently proposed ideas similar to the cognitive cycle, the fundamental hypothesis of the LIDA model of cognition. High-level cognition, such as deliberation, planning, etc., is typically enabled by multiple cognitive cycles. In this paper we describe a timing model LIDA’s cognitive cycle. Based on empirical and simulation data we propose that an initial phase of perception (stimulus recognition) occurs 80–100 ms from stimulus onset under optimal conditions. It is followed by a conscious episode (broadcast) 200–280 ms after stimulus onset, and an action selection phase 60–110 ms from the start of the conscious phase. One cognitive cycle would therefore take 260–390 ms. The LIDA timing model is consistent with brain evidence indicating a fundamental role for a theta-gamma wave, spreading forward from sensory cortices to rostral corticothalamic regions. This posteriofrontal theta-gamma wave may be experienced as a conscious perceptual event starting at 200–280 ms post stimulus. The action selection component of the cycle is proposed to involve frontal, striatal and cerebellar regions. Thus the cycle is inherently recurrent, as the anatomy of the thalamocortical system suggests. The LIDA model fits a large body of cognitive and neuroscientific evidence. Finally, we describe two LIDA-based software agents: the LIDA Reaction Time agent that simulates human performance in a simple reaction time task, and the LIDA Allport agent which models phenomenal simultaneity within timeframes comparable to human subjects. While there are many models of reaction time performance, these results fall naturally out of a biologically and computationally plausible cognitive architecture.

I was a bit surprised that there was no mention of a small prediction being built into the workspace contents. This is really needed for error monitoring in cognition and action. Surely this will be part of the model at some point in its development.

Madl, T., Baars, B., & Franklin, S. (2011). The Timing of the Cognitive Cycle PLoS ONE, 6 (4) DOI: 10.1371/journal.pone.0014803

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