scholarly journals Persistent hippocampal neural firing and hippocampal-cortical coupling predict verbal working memory load

2019 ◽  
Vol 5 (3) ◽  
pp. eaav3687 ◽  
Author(s):  
Ece Boran ◽  
Tommaso Fedele ◽  
Peter Klaver ◽  
Peter Hilfiker ◽  
Lennart Stieglitz ◽  
...  
Keyword(s):  
Working Memory ◽  
Neural Activity ◽  
Medial Temporal Lobe ◽  
Memory Load ◽  
Human Subjects ◽  
Verbal Working Memory ◽  
Neuronal Firing ◽  
Neural Firing ◽  
Scalp Eeg ◽  
Oscillatory Coupling

The maintenance of items in working memory relies on persistent neural activity in a widespread network of brain areas. To investigate the influence of load on working memory, we asked human subjects to maintain sets of letters in memory while we recorded single neurons and intracranial encephalography (EEG) in the medial temporal lobe and scalp EEG. Along the periods of a trial, hippocampal neural firing differentiated between success and error trials during stimulus encoding, predicted workload during memory maintenance, and predicted the subjects’ behavior during retrieval. During maintenance, neuronal firing was synchronized with intracranial hippocampal EEG. On the network level, synchronization between hippocampal and scalp EEG in the theta-alpha frequency range showed workload dependent oscillatory coupling between hippocampus and cortex. Thus, we found that persistent neural activity in the hippocampus participated in working memory processing that is specific to memory maintenance, load sensitive and synchronized to the cortex.

Brain Signature of Working Memory for Sentence Structure: Enriched Encoding and Facilitated Maintenance

2014 ◽  
Vol 26 (8) ◽  
pp. 1654-1671 ◽  
Author(s):  
Corinna E. Bonhage ◽  
Christian J. Fiebach ◽  
Jörg Bahlmann ◽  
Jutta L. Mueller
Keyword(s):  
Working Memory ◽  
Medial Temporal Lobe ◽  
Memory Load ◽  
Syntactic Structure ◽  
Verbal Working Memory ◽  
Sentence Structure ◽  
Broca’S Area ◽  
Broca's Area ◽  
Superiority Effect ◽  
Load Effect

Sentences are easier to memorize than ungrammatical word strings, a phenomenon known as the sentence superiority effect. Yet, it is unclear how higher-order linguistic information facilitates verbal working memory and how this is implemented in the neural system. The goal of the current fMRI study was to specify the brain mechanisms underlying the sentence superiority effect during encoding and during maintenance in working memory by manipulating syntactic structure and working memory load. The encoding of sentence material, as compared with the encoding of ungrammatical word strings, recruited not only inferior frontal (BA 47) and anterior temporal language-related areas but also the medial-temporal lobe, which is not classically reported for language tasks. During maintenance, it was sentence structure as contrasted with ungrammatical word strings that led to activation decrease in Broca's area, SMA, and parietal regions. Furthermore, in Broca's area, an interaction effect revealed a load effect for ungrammatical word strings but not for sentences. The sentence superiority effect, thus, is neurally reflected in a twofold pattern, consisting of increased activation in classical language as well as memory areas during the encoding phase and decreased maintenance-related activation. This pattern reflects how chunking, based on sentential syntactic and semantic information, alleviates rehearsal demands and thus leads to improved working memory performance.

Modulation of medial temporal lobe activity in epilepsy patients with hippocampal sclerosis during verbal working memory

2009 ◽  
Vol 15 (4) ◽  
pp. 536-546 ◽  
Author(s):  
PABLO CAMPO ◽  
FERNANDO MAESTÚ ◽  
IRENE GARCÍA-MORALES ◽  
ANTONIO GIL-NAGEL ◽  
BRYAN STRANGE ◽  
...  
Keyword(s):  
Working Memory ◽  
Episodic Memory ◽  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Time Course ◽  
Hippocampal Sclerosis ◽  
Stimulus Presentation ◽  
Verbal Working Memory ◽  
Compelling Evidence ◽  
Electrophysiological Studies

AbstractIt has been traditionally assumed that medial temporal lobe (MTL) is not required for working memory (WM). However, animal lesion and electrophysiological studies and human neuropsychological and neuroimaging studies have provided increasing evidences of a critical involvement of MTL in WM. Based on previous findings, the central aim of this study was to investigate the contribution of the MTL to verbal WM encoding. Here, we used magnetoencephalography (MEG) to compare the patterns of MTL activation of 9 epilepsy patients suffering from left hippocampal sclerosis with those of 10 healthy matched controls while they performed a verbal WM task. MEG recordings allow detailed tracking of the time course of MTL activation. We observed impaired WM performance associated with changes in the dynamics of MTL activity in epilepsy patients. Specifically, whereas patients showed decreased activity in damaged MTL, activity in the contralateral MTL was enhanced, an effect that became significant in the 600- to 700-ms interval after stimulus presentation. These findings strongly support the crucial contribution of MTL to verbal WM encoding and provide compelling evidence for the proposal that MTL contributes to both episodic memory and WM. Whether this pattern is signaling reorganization or a normal use of a damaged structure is discussed. (JINS, 2009, 15, 536–546.)

Concurrent verbal working memory load constrains cross-linguistic translation activation: A visual world eye-tracking study on Hindi–English bilinguals

2020 ◽  
pp. 1-30
Author(s):  
Seema Prasad ◽  
Ramesh Kumar Mishra
Keyword(s):  
Working Memory ◽  
Memory Load ◽  
Critical Role ◽  
Verbal Working Memory ◽  
Spoken Word ◽  
Cognitive Resources ◽  
Visual World ◽  
Sequence Recognition ◽  
Word Onset ◽  
Study Participants

Abstract Does a concurrent verbal working memory (WM) load constrain cross-linguistic activation? In a visual world study, participants listened to Hindi (L1) or English (L2) spoken words and viewed a display containing the phonological cohort of the translation equivalent (TE cohort) of the spoken word and 3 distractors. Experiment 1 was administered without a load. Participants then maintained two or four letters (Experiment 2) or two, six or eight letters (Experiment 3) in WM and were tested on backward sequence recognition after the visual world display. Greater looks towards TE cohorts were observed in both the language directions in Experiment 1. With a load, TE cohort activation was inhibited in the L2 – L1 direction and observed only in the early stages after word onset in the L1 – L2 direction suggesting a critical role of language direction. These results indicate that cross-linguistic activation as seen through eye movements depends on cognitive resources such as WM.

Brain correlates of action word memory

2018 ◽  
Author(s):  
Zubaida Shebani ◽  
Francesca Carota ◽  
Olaf Hauk ◽  
James B. Rowe ◽  
Lawrence W. Barsalou ◽  
...  
Keyword(s):  
Working Memory ◽  
Motor Cortex ◽  
Verbal Memory ◽  
Memory Load ◽  
Memory Performance ◽  
Verbal Working Memory ◽  
The Body ◽  
Action Perception ◽  
Brain Correlates ◽  
Posterior Parietal

AbstractWhen understanding language semantically related to actions, the motor cortex is active and may be sensitive to semantic information, for example about the body-part-relationship of displayed action-related words. Conversely, movements of the hands or feet can impair memory performance for arm- and leg-related action words respectively, suggesting that the role of motor systems extends to verbal working memory. Here, we studied brain correlates of verbal memory load for action-related words using event-related fMRI during the encoding and memory maintenance of word lists. Seventeen participants saw either four identical or four different words from the same category, semantically related to actions typically performed either with the arms or with the legs. After a variable delay of 4-14 seconds, they performed a nonmatching-to-sample task. Hemodynamic activity related to the information load of words at presentation was most prominent in left temporo-occipital and bilateral posterior-parietal areas. In contrast, larger demand on verbal memory maintenance produced greater activation in left premotor and supplementary motor cortex, along with posterior-parietal areas, indicating that verbal memory circuits for action-related words include the cortical action system. Somatotopic memory load effects of arm- and leg-related words were not present at the typical precentral loci where earlier studies had found such word-category differences in reading tasks, although traces of somatotopic semantic mappings were observed at more anterior cortical regions. These results support a neurocomputational model of distributed action-perception circuits (APCs), according to which language understanding is manifest as full ignition of APCs, whereas working memory is realized as reverberant activity gradually receding to multimodal prefrontal and lateral temporal areas.

scholarly journals Visual Working Memory Load-Related Changes in Neural Activity and Functional Connectivity

PLoS ONE ◽  
2011 ◽  
Vol 6 (7) ◽  
pp. e22357 ◽  
Author(s):  
Ling Li ◽  
Jin-Xiang Zhang ◽  
Tao Jiang
Keyword(s):  
Working Memory ◽  
Functional Connectivity ◽  
Visual Working Memory ◽  
Neural Activity ◽  
Memory Load ◽  
Working Memory Load

Assessing the effect of verbal working memory load on visuo-spatial exogenous orienting

2007 ◽  
Vol 413 (2) ◽  
pp. 105-109 ◽  
Author(s):  
Valerio Santangelo ◽  
Charles Spence
Keyword(s):  
Working Memory ◽  
Memory Load ◽  
Verbal Working Memory ◽  
Exogenous Orienting ◽  
Working Memory Load

Verbal Working Memory Load Affects Regional Brain Activation as Measured by PET

1997 ◽  
Vol 9 (4) ◽  
pp. 462-475 ◽  
Author(s):  
John Jonides ◽  
Eric H. Schumacher ◽  
Edward E. Smith ◽  
Erick J. Lauber ◽  
Edward Awh ◽  
...  
Keyword(s):  
Working Memory ◽  
Task Difficulty ◽  
Memory Load ◽  
Brain Activation ◽  
Verbal Working Memory ◽  
Behavioral Performance ◽  
Executive Processes ◽  
Working Memory Load ◽  
The One ◽  
Reliable Increase

We report an experiment that assesses the effect of variations in memory load on brain activations that mediate verbal working memory. The paradigm that forms the basis of this experiment is the “n-back” task in which subjects must decide for each letter in a series whether it matches the one presented n items back in the series. This task is of interest because it recruits processes involved in both the storage and manipulation of information in working memory. Variations in task difficulty were accomplished by varying the value of n. As n increased, subjects showed poorer behavioral performance as well as monotonically increasing magnitudes of brain activation in a large number of sites that together have been identified with verbal working-memory processes. By contrast, there was no reliable increase in activation in sites that are unrelated to working memory. These results validate the use of parametric manipulation of task variables in neuroimaging research, and they converge with the subtraction paradigm used most often in neuroimaging. In addition, the data support a model of working memory that includes both storage and executive processes that recruit a network of brain areas, all of which are involved in task performance.

scholarly journals Phase-tuned neuronal firing encodes human contextual representations for navigational goals

2017 ◽  
Author(s):  
Andrew J Watrous ◽  
Jonathan Miller ◽  
Salman E Qasim ◽  
Itzhak Fried ◽  
Joshua Jacobs
Keyword(s):  
Firing Rate ◽  
Medial Temporal Lobe ◽  
Single Neuron ◽  
Detection Algorithm ◽  
Neuronal Firing ◽  
Neural Firing ◽  
Categorical Information ◽  
High Frequency Activity ◽  
Oscillation Detection ◽  
Intracranial Recordings

AbstractWe previously demonstrated that the phase of oscillations modulates neural activity representing categorical information using human intracranial recordings and high-frequency activity from local field potentials (Watrous et al., 2015b). We extend these findings here using human single-neuron recordings during a navigation task. We identify neurons in the medial temporal lobe with firing-rate modulations for specific navigational goals, as well as for navigational planning and goal arrival. Going beyond this work, using a novel oscillation detection algorithm, we identify phase-locked neural firing that encodes information about a person’s prospective navigational goal in the absence of firing rate changes. These results provide evidence for navigational planning and contextual accounts of human MTL function at the single-neuron level. More generally, our findings identify phase-coded neuronal firing as a component of the human neural code.

scholarly journals Effect of verbal working memory load during the oculomotor activity in visual search

2015 ◽  
Vol 8 (2) ◽  
pp. 21-35 ◽  
Author(s):  
B.B. Velichkovsky ◽  
A.I. Izmalkova
Keyword(s):  
Working Memory ◽  
Visual Search ◽  
Spatial Working Memory ◽  
Memory Load ◽  
Mutual Influence ◽  
Verbal Working Memory ◽  
Working Memory Load ◽  
Visual Spatial ◽  
Visual Spatial Working Memory ◽  
Oculomotor Activity

The structure of working memory has components responsible for the storage of verbal and visualspatial information; despite the fairly detailed study of the functions and mechanisms of their work, the question of their mutual influence is still open. Studies on the verbal working memory load influence on visual search performance (a task requiring the use of visual-spatial working memory resources) it was found that the load on the verbal working memory leads to increased efficiency of target detection. The results of the analysis of oculomotor activity during visual search also point out that the implementation of such tasks under verbal working memory load is accompanied by an increase in cognitive tension and of the degree of search automaticity. The results may indicate the interaction of verbal and visual-spatial working memory components that share non-specific cognitive resources.

scholarly journals Functional synchronization between hippocampal sEEG, parietal ECoG and scalp EEG during a verbal working memory task

2020 ◽  
Author(s):  
Vasileios Dimakopoulos ◽  
Ece Boran ◽  
Peter Hilfiker ◽  
Lennart Stieglitz ◽  
Thomas Grunwald ◽  
...  
Keyword(s):  
Working Memory ◽  
Auditory Cortex ◽  
Information Flow ◽  
Verbal Working Memory ◽  
Oscillatory Activity ◽  
Functional Coupling ◽  
Maintenance Period ◽  
Physiological Basis ◽  
Cortical Areas ◽  
Scalp Eeg

ABSTRACTBackgroundThe maintenance of items in working memory (WM) relies on a widespread network of brain areas where synchronization between electrophysiological recordings may reflect functional coupling. While the coupling from hippocampus to scalp EEG is well established, we provide here direct cortical recordings for a fine-grained analysis.MethodsA patient performed a WM task where a string of letters was presented all at once, thus separating the encoding period from the maintenance period. We recorded sEEG from the hippocampus, temporo-parietal ECoG from a 64-contact grid electrode, and scalp EEG.ResultsPower spectral density (PSD) showed a clear task dependence: PSD in the posterior parietal lobe (10 Hz) and in the hippocampus (20 Hz) peaked towards the end of the maintenance period.Inter-area synchronization was characterized by the phase locking value (PLV). WM maintenance enhanced PLV between hippocampal sEEG and scalp EEG specifically in the theta range [6 7] Hz.PLV from hippocampus to parietal cortex increased during maintenance in the [9 10] Hz alpha and the 20 Hz range.When analyzing the information flow to and from auditory cortex by Granger causality, the flow was from auditory cortex to hippocampus with a peak in the [8 18] Hz range while letters were presented, and this flow was subsequently reversed during maintenance, while letters were maintained in memory.ConclusionsThe increased functional interaction between hippocampus and cortex through synchronized oscillatory activity and the directed information flow provide physiological basis for reverberation of memory items during maintenance. This points to a network for working memory that is bound by coherent oscillations involving cortical areas and hippocampus.SIGNIFICANCE STATEMENTHippocampal activity is known for its role in cognitive tasks involving episodic memory or spatial navigation, but its role in working memory and its sensitivity to workload is still under debate. Here, we investigated hippocampal and cortical activity while a subject maintained sets of letters in verbal working memory for a few seconds to guide action.After confirming the coupling between hippocampal oscillations and oscillations on the scalp, we found during maintenance that hippocampal oscillations increased coupling differentially to several areas of cortex by recording directly from the cortex.. During encoding of the letters, information flow was from auditory cortex to hippocampus and subsequently reversed during maintenance, thus providing a physiological basis for memory encoding and maintenance.This demonstrates a network for working memory that is bound by coherent oscillations that underlie the functional connectivity between cortical areas and hippocampus.

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