Abstracts

Akira Miyake, University of Colorado at Boulder, USA
Unity and Diversity of Executive Functions: Individual Differences in Inhibition and Interference Control

Michael J. Kane, University of North Carolina at Greensboro, USA
Exploring executive control by exploiting individual differences in working-memory capacity

Working memory (WM) span tasks reflect a domain-general attentional construct that is broadly important to higher level cognition, and so the study of individual differences in WM can inform general theory on executive control.  In support of this argument, I first present a large structural-equation-modeling study demonstrating that verbal and spatial measures of WM span, in contrast to measures of short-term memory (STM) span, are indistinguishable.  Furthermore, this domain-general WM construct is strongly related to general fluid intelligence (Gf), and is also predictive of verbal-specific and spatial-specific reasoning.  In contrast, verbal and spatial tasks of STM span are dissociable and show different patterns of predictive utility: Whereas verbal STM predicts verbal-specific reasoning but not Gf, spatial STM predicts both spatial-specific reasoning and Gf.  Spatial STM, like WM, thus appears to tap general executive functions in ways that verbal STM does not.  I will then discuss experiments in which high- and low-WM subjects differ in attention-control capabilities across antisaccade and Stroop tasks, which both critically require goal-directed responses that conflict with habit.  I will also present data indicating that WM capacity does not predict other varieties of putative “executive” or “controlled” processing, such as task switching and visual search, thus suggesting some boundary conditions to the executive-control construct.

Mariko Osaka, Osaka University of Foreign Studies, Japan
Neural basis of individual differences in the executive function: An fMRI study

Using fMRI, neural substrates of executive function in verbal working memory were investigated with respect to differences in working memory capacity. Listening-span-test (LST), Listen and Remember conditions were performed. Two subjects groups were selected: high-span subjects (HSS) and low-span subjects (LSS) according to working memory span test. Significant activation was found mainly in two regions in comparison with control: left prefrontal cortex (PFC), anterior cingulate cortex (ACC). For both groups, the fMRI signal intensity increased in PFC during the LST condition compared to Listen conditions. A group difference was found in the ACC region, specifically a significant increase in signal intensity was observed in ACC only for the HSS group and not for the LSS group. Moreover, the cross correlation of signal change between ACC and IFG was higher in HSS than in LSS, indicating the network system between ACC and IFG was more connected in HSS compared to that of LSS. These results indicate that the attention control in executive function is more effective in HSS compared to that of LSS.

Robert H. Logie, University of Aberdeen, United Kingdom
Dual task co-ordination as an executive function: Evidence from Alzheimer's disease, healthy ageing, and fMRI investigations

Motoichiro Kato, Keio University, Japan
The role of dorsolateral, orbital and medial frontal lobes in executive functions: A neuropsychological study

Functional neuroimaging studies of the prefrontal function suggested that different executive processes can be related to distinct subdivisions within prefrontal lobes.　However, neuropsychological evidences are rare, because of relative infrequency of patients with limited focal prefrontal lobe lesions. It is necessary for us to compare the neuroimaging data with behavioral findings. In this presentation, I present the performances on executive tasks in four patients whose brain damages existed in the restricted focal prefrontal lobes. The right dorsolateral damaged patient was not impaired on simple verbal and spatial span test, but showed poor performances on delayed response task, Reading span test, and WCST. The patient with lesions of the left ventrolateral frontal lobes including Broca's area demonstrated had good performances on span tests and delayed response task with severe impairment on WCST. On the other hand, the orbitofrontal patient had good performances on classical executive tasks with a little poor performance on the Gambling task.　Moreover, the role of frontal-parietal circuits in dysexecutive syndrome is critical. A patient with the left circumscribed focal angular lesions showed the very similar deficits to prefrontal patients. These findings indicated that the executive disorders linked to dysfunction of corticocortical connection could emerge.

Mark D'Esposito, University of California Berkeley, USA
Towards understanding the role of prefrontal cortex in executive control: Evidence from functional MRI

To this day, the frontal lobes remain a region of human cortex for which It's function continues to elude neuroscientists. Evidence from neuropsychological, electrophysiological and functional neuroimaging supports the notion that the prefrontal cortex (PFC) is necessary for temporarily maintaining relevant information in an active state, a process that is critical for the voluntary control of behavior. The extensive reciprocal connections from PFC to virtually all cortical and subcortical structures places it in a unique anatomical position to monitor and manipulate diverse cognitive processes. However, little is known about the differential contribution of PFC versus other cortical/subcortical areas in implementing executive control. In this talk, I will present evidence from several event-related fMRI studies that support a model of executive control in which PFC biases activity in posterior stimulus-specific association cortex in favor of behaviorally relevant information. Moreover, the temporal dynamics of the signal from the PFC vs. posterior stimulus-specific association cortex is consistent with perceptually-driven bottom-up flow of information when encoding representations that must be maintained, and internally-driven top-down flow of information when decisions and actions are made based on maintained representations. Hopefully, an improved understanding of the physiological basis of executive control derived from powerful techniques such as fMRI and ERP will lead to a narrower and more useful view of frontal lobe function.

Masataka Watanabe, Tokyo Metropolitan Institute of Neuroscience, Japan
Integration of cognitive and motivational operations for goal-directed behavior in the lateral prefrontal cortex

It is well established that the lateral part of the prefrontal cortex (LPFC) plays important roles in cognitive operations, such as retaining information in working memory while the orbital part of the prefrontal cortex (OFC) is indicated to be more concerned with motivational operations.  However human neuroimaging studies also indicate the importance of the LPFC in motivational operations, such as processing reward information. We examined neuronal activities in the primate LPFC and OFC in relation to both motivational and cognitive operations; i.e., in relation to reward processing and working memory.  We found reward- and reward expectancy-related neurons in both the LPFC and OFC while we found working memory-related neurons only in the LPFC.  Furthermore, we found many LPFC neurons that were related to both reward expectancy and working memory.For survival, monkeys work to obtain a goal, such as food, liquid and a mate.  Reward expectancy-related activity and working memory-related activity in LPFC neurons are considered to be concerned with representing what is the goal of a behavior, and representing how the goal can be attained, respectively.  We propose that executive control function for goal-directed behavior is supported not solely by cognitive operations but by the integration of cognitive and motivational operations in the LPFC.

Shoji Tanaka, Sophia University, Japan
Computational study of the circuit mechanisms for spatial working memory processing

Cognitive processes in the brain are emergent properties of the cortical and subcortical networks. My laboratory has developed circuit models for the study of spatial working memory processing. The models include (i) the network of the prefrontal cortex and the posterior parietal cortex, (ii) the cortico-thalamocortical circuit, and (iii) the cortico-mesocortical dopamine system. In this symposium, I am going to show the results of computer simulations with these models.
The prefrontal cortical circuit can store the information of several target locations. The corticocortical connections would mediate working memory loading and feedback control of the processing. The simulation suggests that the feedback connections play critical roles especially when processing multiple targets. By sending feedback bias, the prefrontal cortex contributes to attentional control, being consistent with the notion that working memory and attention share a common circuit. I propose that the feedback connections play wider and critical roles in cognitive operations than merely control the activity of the recipient areas. Our simulation also shows the thalamocortical manipulation of spatial working memory represented in the prefrontal cortex. Lastly, I am going to argue the roles of dopamine in fundamental cognitive operations and the circuit properties of the cortico-mesocortical dopamine system.