The Role of the Hippocampus and LIFGs in Working Memory Retrieval

The precise temporal coordination of activity in the brain is thought to be fundamental for memory encoding and retrieval. The medial septum (MS) provides the largest source of innervation to the hippocampus (HPC), and its inhibitory neurons play a major role in controlling HPC theta (~8 Hz) oscillations. While pharmacological inhibition of the MS is associated with memory impairment, the exact role of MS inhibitory neurons in HPC function and memory is not fully understood. While HPC place cells were previously reported to not depend on MS inputs, the exact role of MS inputs on HPC temporal codes is still a matter of debate. Moreover, pharmacological manipulations do not have the temporal resolution to distinguish the role of MS activity on working memory encoding, retention and retrieval. Here we stimulated the MS with optogenetics to either pace or ablate theta, while recording large hippocampal assemblies over time using calcium imaging along with local field potentials to monitor theta control. Using scrambled light stimulation, we could robustly ablate theta signals, which was associated with direct modulation of a subpopulation of neurons in the HPC. We found that such stimulation led to decreased working memory retrieval, but not encoding in both a delayed non-match to sample task and a novel place object recognition task. Strikingly, scrambled stimulations were not associated with disrupted spatiotemporal codes. Importantly, we show that our opsin did not transfect cholinergic cells and stimulation did not disrupt HPC ripple activity or running speed, suggesting a specific role for MS GABAergic cells in memory maintenance and retrieval that is independent from these other potential confounding mechanisms. Our study suggests that theta signals play a specific and essential role in supporting working memory retrieval and maintenance while not being necessary for hippocampal spatiotemporal codes.

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Sustained Activities and Retrieval in a Computational Model of the Perirhinal Cortex

Journal of Cognitive Neuroscience ◽

10.1162/jocn.2008.20147 ◽

2008 ◽

Vol 20 (11) ◽

pp. 1993-2005 ◽

Cited By ~ 4

Author(s):

Julien Vitay ◽

Fred H. Hamker

Keyword(s):

Working Memory ◽

Computational Model ◽

Visual Working Memory ◽

Memory Retrieval ◽

Novelty Detection ◽

Perirhinal Cortex ◽

Global Information ◽

Multimodal Integration ◽

Dopaminergic Modulation

The perirhinal cortex is involved not only in object recognition and novelty detection but also in multimodal integration, reward association, and visual working memory. We propose a computational model that focuses on the role of the perirhinal cortex in working memory, particularly with respect to sustained activities and memory retrieval. This model describes how different partial informations are integrated into assemblies of neurons that represent the identity of an object. Through dopaminergic modulation, the resulting clusters can retrieve the global information with recurrent interactions between neurons. Dopamine leads to sustained activities after stimulus disappearance that form the basis of the involvement of the perirhinal cortex in visual working memory processes. The information carried by a cluster can also be retrieved by a partial thalamic or prefrontal stimulation. Thus, we suggest that areas involved in planning and memory coordination encode a pointer to access the detailed information encoded in the associative cortex such as the perirhinal cortex.

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Working Memory and Number Sense as Predictors of Mathematical (Dis-)Ability

Zeitschrift für Psychologie ◽

10.1027/2151-2604/a000208 ◽

2015 ◽

Vol 223 (2) ◽

pp. 102-109 ◽

Cited By ~ 13

Author(s):

Evelyn H. Kroesbergen ◽

Marloes van Dijk

Keyword(s):

Working Memory ◽

Learning Disabilities ◽

Spatial Working Memory ◽

Number Sense ◽

Mathematical Learning ◽

Visual Spatial ◽

Mathematical Learning Disabilities ◽

Visual Spatial Working Memory ◽

And Mathematics

Recent research has pointed to two possible causes of mathematical (dis-)ability: working memory and number sense, although only few studies have compared the relations between working memory and mathematics and between number sense and mathematics. In this study, both constructs were studied in relation to mathematics in general, and to mathematical learning disabilities (MLD) in particular. The sample consisted of 154 children aged between 6 and 10 years, including 26 children with MLD. Children performing low on either number sense or visual-spatial working memory scored lower on math tests than children without such a weakness. Children with a double weakness scored the lowest. These results confirm the important role of both visual-spatial working memory and number sense in mathematical development.

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Working Memory Capacity and a Notorious Brain Teaser

Experimental Psychology (formerly Zeitschrift für Experimentelle Psychologie) ◽

10.1027/1618-3169.53.1.123 ◽

2006 ◽

Vol 53 (2) ◽

pp. 123-131 ◽

Cited By ~ 29

Author(s):

Wim De Neys ◽

Niki Verschueren

Keyword(s):

Working Memory ◽

Secondary Task ◽

Working Memory Capacity ◽

Memory Capacity ◽

Task Load ◽

Normative Reasoning ◽

Monty Hall Dilemma ◽

Monty Hall ◽

Memory Resources

Abstract. The Monty Hall Dilemma (MHD) is an intriguing example of the discrepancy between people’s intuitions and normative reasoning. This study examines whether the notorious difficulty of the MHD is associated with limitations in working memory resources. Experiment 1 and 2 examined the link between MHD reasoning and working memory capacity. Experiment 3 tested the role of working memory experimentally by burdening the executive resources with a secondary task. Results showed that participants who solved the MHD correctly had a significantly higher working memory capacity than erroneous responders. Correct responding also decreased under secondary task load. Findings indicate that working memory capacity plays a key role in overcoming salient intuitions and selecting the correct switching response during MHD reasoning.

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