Clinical significance of knowledge about the structure, function, and impairments of working memory

Abstract

A review of contemporary research on the working memory system (WMS) is important, both due to the need to focus the discussion on further necessary investigations on the structure and function of this key part of the human brain, as well as to share this knowledge with clinicians. In our introduction we try to clarify the actual terminology and provide an intuitively understandable model for 3 basic cognitive operations: perception, recognition, imagery, and manipulation of recalled mental images. We emphasize the importance of knowledge of the structure and function of the WMS for the possibility to demonstrate the links between genetic polymorphisms and the prevalence to some mental disorders. We also review current knowledge of working memory dysfunction in the most common diseases and specific clinical situations such as maturation and aging. Finally, we briefly discuss methods for assessment of WMS capacity. This article establishes a kind of compendium of knowledge for clinicians who are not familiar with the structure and operation of the WMS.

Figure 1

Anatomical locations of elements of the working memory system.

Figure 2

Scheme of a neuron of retina sensitive for a dot pattern.

Figure 3

The function of a neurons of second layer of the visual pathway.

Figure 4

An example of the rule of function for a neuron of third layer of the visual pathway.

Figure 5

The visual pathways does not end in the occipital region, but is prolonged by superior structures placed in the anterior part of the temporal lobe, where so called ‘object neuron’ can be found. The object neurons are connected with the recalling loop of the working memory system.

Figure 6

The representations of the source pattern of information on higher level of the visual pathway are dispersed and different aspect of this source pattern are perceived.

Figure 7

Two kinds of connections reach so called ‘object neurons’. One of them, going from the side of hypothalamus and amygdale is active in the case of emotional arousal and take part in the consolidation of the long- term memory traces. The second connection constitutes the oscillating loop, which cause that the evoked mental image is aroused for the time necessary for the action of the working memory.

Figure 8

The nature of the mental imaginary. A mental image is recalled from the memory, when the activation oscillate down and back to the top of the hierarchical structure owing to so called recurrent axons. Three layers of the hierarchical structure of neurons integrating sensory information, for instance – in the visual pathways. The traces of long term memory are consolidated under the influence of connections from hypothalamus and amygdale (A). There are consolidated through two mappings: weights of receiving, ascending synapses (s_10, s₁₁, s₁₂) and synaptic weights of reproducing connections (s₁, s₂, s₃). The second, cortico – hippocampal loop (B) is necessary for temporary recalling of the mental image. The activation of the object neuron by this indexing loop causes the recurrent reactivation of neurons in lower layers. The doted line indicate the pathways of repetitive circulations of stimuli in the upper layers of the hierarchical structure, what is the essence of mental imaginary. The object neuron can be activated also from the side of speech area (C). Mental imagery is the essence of episodic memory, short term memory and is used for working memory activity.