What have Klingon letters and faces in common? An fMRI study on content-specific working memory systems

Abstract

Neuroimaging studies show that prefrontal, premotor, and parietal cortical regions are part of a working memory network that supports the active retention of information. In two experiments we used fMRI to examine whether prefrontal and posterior cortical areas are organized in a content‐specific way for object and spatial working memory. Subjects performed a delayed matching‐to‐sample task modified to allow the examination of content‐specific retention processes, independent of perceptual and decision‐related processes. In Experiment 1, either unfamiliar geometrical objects (Klingon letters from an artificial alphabet unknown to the participants) or their spatial locations had to be memorized, whereas in Experiment 2, either unfamiliar faces or biological objects (butterflies) were actively memorized. All tasks activated a similar cortical network including posterior parietal (banks of the intraparietal sulcus), premotor (banks of the inferior precentral sulcus) and prefrontal regions (banks of the inferior frontal sulcus), and the presupplementary motor area (pre‐SMA). For geometrical objects and faces for which strategic semantic processing can be assumed, this activation was larger in the left than in the right hemisphere, whereas a bilateral or right dominant distribution was obtained for butterflies and spatial locations. The present results do not support the process‐specific or content‐specific view of the role of the prefrontal cortex in working memory task. Rather, they suggest that the inferior prefrontal cortex houses nonmemonic strategic processing systems required for response selection and task management that can flexibly be used across a variety of tasks and informational domains. Hum. Brain Mapping 11:146–161, 2000. © 2000 Wiley‐Liss, Inc.

Telling truth from lie in individual subjects with fast event‐related fMRI

“…Remarkably, this definition resonates closely with the Augustinian: deception is denying what is definition [Augustine, [1948]]. If the ultimate goal of detecting a lie is collecting information about what an individual knows, fMRI can be beneficial in conjunction with activation paradigms aimed at brain correlates of semantic memory [Hirsch et al, [2001]; Mecklinger et al, [2000]; Nystrom et al, [2000]]. While a potential confound in characterization of the neural mechanisms of deception, in such case salience could serve as a marker of concealed or unconscious knowledge [Berns et al, [1997]; Tranel and Damasio, [1985]].…”

The neural basis of the bilateral distribution advantage

“…The bilateral frontal activations at the junction of the inferior frontal and inferior precentral sulci may represent the higher executive task demands posed by letter name matching, compared to shape matching (Mecklinger et al 2000). Name matching also elicited an activation in right frontopolar cortex.…”

Dissociable brain mechanisms for inhibitory control: effects of interference content and working memory capacity

“…The present left inferior frontal activation was located more posterior at the junction of the precentral sulcus and the inferior frontal sulcus. Activation in this postero-ventral PFC region has been reported in a variety of tasks with rather different processing demands, including active maintenance [29], set shifting [10,35] or task preparation [3]. A common characteristic of these tasks is the requirement to learn new stimulus-response associations and to adapt them to current task demands [35].…”

“…A modification of this view has recently been proposed by Smith and Jonides [44]. They propose that content-specificity is mainly a laterality effect with the right dorsolateral and ventrolateral PFC being engaged by both, spatial and non-spatial working memory and the corresponding left PFC regions showing involvement only in non-spatial working memory [13,29,38]. The view of a content-specific segregation has recently been extended by the finding that maintaining information about manipulable (tool-like) and non-manipulable objects recruits different neuronal circuitries even though working memory performance was not affected by this object class manipulation [30].…”