Medial temporal and prefrontal contributions to working memory tasks with novel and familiar stimuli

Abstract

Lesions of parahippocampal structures impair performance of delayed matching tasks in nonhuman primates, suggesting a role for these structures in the maintenance of items in working memory and short-term stimulus matching. However, most human functional imaging studies have not shown medial temporal activation during working memory tasks and have primarily focused on functional magnetic resonance imaging (fMRI) signal intensity changes in the prefrontal and posterior parietal cortex. The goal of this study was to test the hypothesis that the difference between the human and nonhuman primate data results from the use of highly familiar stimuli in human working memory studies and trial-unique stimuli in nonhuman primate studies. We used fMRI to examine prefrontal and temporal lobe activation during performance of a working memory (two-back) task, using blocks of novel and highly familiar complex pictures. Performance of the working memory task with novel complex pictures resulted in greater signal change within medial temporal lobe structures than performance of the task with familiar complex pictures. In contrast, the working memory task with highly familiar stimuli resulted in greater prefrontal activation. These results are consistent without hypothesis that the medial temporal lobe is recruited for the short-term maintenance of information that has no prior representation in the brain, whereas the prefrontal cortex is important for monitoring familiar stimuli that have a high degree of interference. A second set of tasks examined stimulus matching. Subjects performed a target-matching task, during which they identified a single target presented in blocks of novel or familiar stimuli. The results provide evidence of hippocampal and parahippocampal recruitment in the target-matching task with familiar stimuli. These results are consistent with prior animal studies and suggest that prefrontal regions may be important for the monitoring and matching of familiar stimuli which have a high potential for interference, whereas medial temporal regions may become proportionally more important for matching and maintenance of novel stimuli.

Visual Working Memory Is Impaired when the Medial Temporal Lobe Is Damaged

“…Our findings are consistent with recent neuroimaging findings that report activations of the hippocampus during visual WM tasks (Ranganath & D'Esposito, 2005). Some investigators interpreted these activations as establishment of an LTM trace for novel stimuli (Ranganath, Cohen, & Brozinsky, 2005;Ranganath & D'Esposito, 2005;Schon, Hasselmo, LoPresti, Tricarico, & Stern, 2004;Stern, Sherman, Kirchhoff, & Hasselmo, 2001), whereas others suggest that they reflected WM maintenance for certain classes of stimuli (Mitchell, Johnson, Raye, & D'Esposito, 2000). It is difficult to give a strong interpretation to these findings given that the majority of functional magnetic resonance imaging (fMRI) studies have not reported MTL activations during WM tasks (Postle, Stern, Rosen, & Corkin, 2000;Stern, Owen, et al, 2000;Cohen et al, 1997;Owen, Sahakian, Semple, Polkey, & Robbins, 1995).…”

Auditory evoked potentials in females with high and low acceptance of background noise when listening to speech

“…The process of selective attention is one in which an individual "selectively attends to some stimuli, or aspects of stimuli, in preference to others" ͑Kahneman, 1973͒, and is a vital component of one's ability to function in the environment. There are numerous studies emphasizing the role of the cortex in this ability to effectively suppress stimuli that are not relevant to the task at hand ͑e.g., Glosser and Goodglass, 1990;Knight et al, 1999;Rueckert and Grafman, 1996;Stern et al, 2001͒. Reviews of literature in cognitive functioning emphasize that individual differences in behavioral performance might best be explained by underlying differences in cortical inhibition ͑e.g., Dempster, 1992;Harnishfeger and Bjorkland, 1994͒.…”

Reorganization of hippocampal functional connectivity with transition to chronic back pain

“…Both HG and mPFC are implicated in working memory (Stern et al 2001), and recent animal studies have directly linked altered HG-mPFC functional connectivity in chronic pain to spatial working memory deficits (Cardoso-Cruz et al 2013). Additionally, HG-mPFC bidirectional interactions are necessary for making choices between different response strategies (Goto and Grace 2008), suggesting that HG-mPFC interactions are essential for mediating behaviorally relevant spiking patterns to utilize memory in driving goal-directed behavior (Goto and Grace 2008;Squire 1992).…”