Scientific Understanding of Consciousness
Consciousness as an Emergent Property of Thalamocortical Activity

Working Memory -- Recent Research

 

Science 13 June 2008: Vol. 320. no. 5882, pp. 1510 - 1512

Transfer of Learning After Updating Training Mediated by the Striatum

Erika Dahlin,^1,2Anna Stigsdotter Neely,³ Anne Larsson,^2,4 Lars Bäckman,⁵ Lars Nyberg^1,2,4

¹ Department of Integrative Medical Biology, Umeå University, 90187 Umeå, Sweden.
² Department of Radiation Sciences, Umeå University, 90187 Umeå, Sweden.
³ Department of Psychology, Umeå University, 90187 Umeå, Sweden.
⁴ Umeå Center for Functional Brain Imaging (UFBI), Umeå University, 90187 Umeå, Sweden.
⁵ Aging Research Center, Karolinska Institute, 11330 Stockholm, Sweden.

(paraphrase)

Task-specific performance enhancement and altered patterns of brain activity have been demonstrated after training on complex executive tasks. Training can also improve performance on untrained transfer tasks, but the magnitude of gain is considerably smaller and often there is no transfer at all. One current hypothesis is that transfer will occur if the criterion and transfer tasks involve overlapping processing components and engage, at least in part, the same brain regions. In the present study, we studied learning and transfer of a specific skill: updating. Updating is a basic executive function related to measures of intelligence and working memory, in particular to working-memory tasks that require manipulation of information. Updating has been associated with the striatum, and, in a recent computational model, striatal neurons serve a gating function for updating in working memory.

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Science 31 January 1992: Vol. 255. no. 5044, pp. 556 - 559
Working memory

By A Baddeley

Book review by Medical Research Council, Applied Psychology Unit, Cambridge, United Kingdom.

(paraphrase)

The term working memory refers to a brain system that provides temporary storage and manipulation of the information necessary for such complex cognitive tasks as language comprehension, learning, and reasoning. This definition has evolved from the concept of a unitary short-term memory system. Working memory has been found to require the simultaneous storage and processing of information. It can be divided into the following three subcomponents: (i) the central executive, which is assumed to be an attentional-controlling system, is important in skills such as chess playing and is particularly susceptible to the effects of Alzheimer's disease; and two slave systems, namely (ii) the visuospatial sketch pad, which manipulates visual images and (iii) the phonological loop, which stores and rehearses speech-based information and is necessary for the acquisition of both native and second-language vocabulary.

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Nature 438, 500-503 (24 November 2005)

Neural measures reveal individual differences in controlling access to working memory

Edward K. Vogel, Andrew W. McCollough and Maro G. Machizawa

(paraphrase)

The capacity of visual short-term memory is highly limited, maintaining only three to four objects simultaneously. This extreme limitation necessitates efficient mechanisms to select only the most relevant objects from the immediate environment to be represented in memory and to restrict irrelevant items from consuming capacity. Here we report a neurophysiological measure of this memory selection mechanism in humans that gauges an individual's efficiency at excluding irrelevant items from being stored in memory. By examining the moment-by-moment contents of visual memory, we observe that selection efficiency varies substantially across individuals and is strongly predicted by the particular memory capacity of each person. Specifically, high capacity individuals are much more efficient at representing only the relevant items than are low capacity individuals, who inefficiently encode and maintain information about the irrelevant items present in the display. These results provide evidence that under many circumstances low capacity individuals may actually store more information in memory than high capacity individuals. Indeed, this ancillary allocation of memory capacity to irrelevant objects may be a primary source of putative differences in overall storage capacity.

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Is Prefrontal Cortex Modular for Sensory Domains?

Here is an interesting article discussing the possible modularity of prefrontal cortex for sensory domains. As is often the case in brain studies, monkeys are used rather than humans.

 

Science 7 November 1997: Vol. 278. no. 5340, pp. 1135 - 1138

Areal Segregation of Face-Processing Neurons in Prefrontal Cortex

Séamas P. Ó Scalaidhe, Fraser A. W. Wilson, Patricia S. Goldman-Rakic

Section of Neurobiology, Yale University Medical School, 333 Cedar Street, New Haven, CT 06510, USA.

(paraphrase)

A central issue in cognitive neuroscience concerns the functional architecture of the prefrontal cortex and the degree to which it is organized by sensory domain. To examine this issue, multiple areas of the macaque monkey prefrontal cortex were mapped for selective responses to visual stimuli that are prototypical of the brain's object vision pathway--pictorial representations of faces. Prefrontal neurons not only selectively process information related to the identity of faces but, importantly, such neurons are localized to a remarkably restricted area. These findings suggest that the prefrontal cortex is functionally compartmentalized with respect to the nature of its inputs.

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Sociopathic behavior - anterior cingulate and the orbitofrontal cortices

Sociopathic behavior is believed to be associated with anterior cingulate and the orbitofrontal cortices. Pineas Gage

 

Science, Vol 313, 1 September 2006, p.1310

A Role for the Macaque Anterior Cingulate Gyrus in Social Valuation

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Complex human social interaction is disrupted when the frontal lobe is damaged in disease, and in extreme cases patients are described as having acquired sociopathy. We compared, in macaques, the effects of lesions in subdivisions of the anterior cingulate and the orbitofrontal cortices believed to be anatomically homologous to those damaged in such patients. We show that the anterior cingulate gyrus in male macaques is critical for normal patterns of social interest in other individual male or female macaques. Conversely, the orbitofrontal cortex lesion had a marked effect only on responses to mildly fear-inducing stimuli. These results suggest that damage to the anterior cingulate gyrus may be the cause of changes in social interaction seen after frontal lobe damage.

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Science 29 October 2004: Vol. 306. no. 5697, pp. 882 - 884

Protein Kinase C Overactivity Impairs Prefrontal Cortical Regulation of Working Memory

S. G. Birnbaum,^1,2 P. X. Yuan,³ M. Wang,¹ S. Vijayraghavan,¹ A. K. Bloom,¹ D. J. Davis,¹ K. T. Gobeske,¹ J. D. Sweatt,² H. K. Manji,³ A. F. T. Arnsten¹

¹ Department of Neurobiology, Yale Medical School, 333 Cedar Street, New Haven, CT 06520–8001, USA.
² Department of Neuroscience, 1 Baylor Plaza, Baylor College of Medicine, Houston TX 77030, USA.
³ Laboratory of Molecular Pathophysiology, National Institute of Mental Health (NIMH), Bethesda, MD 20892–4405, USA.

(paraphrase)

The prefrontal cortex is a higher brain region that regulates thought, behavior, and emotion using representational knowledge, operations often referred to as working memory. We tested the influence of protein kinase C (PKC) intracellular signaling on prefrontal cortical cognitive function and showed that high levels of PKC activity in prefrontal cortex, as seen for example during stress exposure, markedly impair behavioral and electrophysiological measures of working memory. These data suggest that excessive PKC activation can disrupt prefrontal cortical regulation of behavior and thought, possibly contributing to signs of prefrontal cortical dysfunction such as distractibility, impaired judgment, impulsivity, and thought disorder.

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