scholarly journals Reunification of Object and View-Center Background Information in the Primate Medial Temporal Lobe

2021 ◽  
Vol 15 ◽  
Author(s):  
He Chen ◽  
Yuji Naya
Keyword(s):  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Large Scale ◽  
Scene Perception ◽  
Background Information ◽  
Background Signal ◽  
Related Information ◽  
Visual Inputs ◽  
Electrophysiological Studies ◽  
Ventral Pathway

Recent work has shown that the medial temporal lobe (MTL), including the hippocampus (HPC) and its surrounding limbic cortices, plays a role in scene perception in addition to episodic memory. The two basic factors of scene perception are the object (“what”) and location (“where”). In this review, we first summarize the anatomical knowledge related to visual inputs to the MTL and physiological studies examining object-related information processed along the ventral pathway briefly. Thereafter, we discuss the space-related information, the processing of which was unclear, presumably because of its multiple aspects and a lack of appropriate task paradigm in contrast to object-related information. Based on recent electrophysiological studies using non-human primates and the existing literature, we proposed the “reunification theory,” which explains brain mechanisms which construct object-location signals at each gaze. In this reunification theory, the ventral pathway signals a large-scale background image of the retina at each gaze position. This view-center background signal reflects the first person’s perspective and specifies the allocentric location in the environment by similarity matching between images. The spatially invariant object signal and view-center background signal, both of which are derived from the same retinal image, are integrated again (i.e., reunification) along the ventral pathway-MTL stream, particularly in the perirhinal cortex. The conjunctive signal, which represents a particular object at a particular location, may play a role in scene perception in the HPC as a key constituent element of an entire scene.

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.)

Forward Processing of Object–Location Association from the Ventral Stream to Medial Temporal Lobe in Nonhuman Primates

2019 ◽  
Vol 30 (3) ◽  
pp. 1260-1271 ◽  
Author(s):  
He Chen ◽  
Yuji Naya
Keyword(s):  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Spatial Information ◽  
Object Location ◽  
Object Identity ◽  
Downstream Target ◽  
Parahippocampal Cortex ◽  
Ventral Pathway ◽  
Additive Form ◽  
Location Association

Abstract While the hippocampus (HPC) is a prime candidate combining object identity and location due to its strong connections to the ventral and dorsal pathways via surrounding medial temporal lobe (MTL) areas, recent physiological studies have reported spatial information in the ventral pathway and its downstream target in MTL. However, it remains unknown whether the object–location association proceeds along the ventral MTL pathway before HPC. To address this question, we recorded neuronal activity from MTL and area anterior inferotemporal cortex (TE) of two macaques gazing at an object to retain its identity and location in each trial. The results showed significant effects of object–location association at a single-unit level in TE, perirhinal cortex (PRC), and HPC, but not in the parahippocampal cortex. Notably, a clear area difference emerged in the association form: 1) representations of object identity were added to those of subjects’ viewing location in TE; 2) PRC signaled both the additive form and the conjunction of the two inputs; and 3) HPC signaled only the conjunction signal. These results suggest that the object and location signals are combined stepwise at TE and PRC each time primates view an object, and PRC may provide HPC with the conjunctional signal, which might be used for encoding episodic memory.

scholarly journals When shared concept cells support associations: theory of overlapping memory engrams

2021 ◽  
Author(s):  
Chiara Gastaldi ◽  
Tilo Schwalger ◽  
Emanuela De Falco ◽  
Rodrigo Quian Quiroga ◽  
Wulfram Gerstner
Keyword(s):  
Experimental Data ◽  
Neural Networks ◽  
Free Recall ◽  
Computational Model ◽  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Background Signal ◽  
Neural Assemblies ◽  
Model Match

AbstractAssemblies of neurons, called concepts cells, encode acquired concepts in human Medial Temporal Lobe. Those concept cells that are shared between two assemblies have been hypothesized to encode associations between concepts. Here we test this hypothesis in a computational model of attractor neural networks. We find that for concepts encoded in sparse neural assemblies there is a minimal fraction cmin of neurons shared between assemblies below which associations cannot be reliably implemented; and a maximal fraction cmax of shared neurons above which single concepts can no longer be retrieved. In the presence of a periodically modulated background signal, such as hippocampal oscillations, recall takes the form of association chains reminiscent of those postulated by theories of free recall of words. Predictions of an iterative overlap-generating model match experimental data on the number of concepts to which a neuron responds.Authors contributionsAll authors contributed to conception of the study and writing of the manuscript. CG and TS developed the theory. CG wrote the code for all figures. EDF and RQQ provided the experimental data. EDF and CG analyzed the data. WG and CG developed algorithms to fit the experimental data.

scholarly journals Modelling the influence of the hippocampal memory system on the oculomotor system

2018 ◽  
Author(s):  
Jennifer D. Ryan ◽  
Kelly Shen ◽  
Arber Kacollja ◽  
Heather Tian ◽  
John Griffiths ◽  
...  
Keyword(s):  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Large Scale ◽  
Signal Propagation ◽  
Oculomotor System ◽  
Visual Exploration ◽  
Large Scale Network ◽  
Two Systems ◽  
Scale Network ◽  
Stimulation Of

AbstractVisual exploration is related to activity in the hippocampus (HC) and/or extended medial temporal lobe system (MTL), is influenced by stored memories, and is altered in amnesic cases. An extensive set of polysynaptic connections exists both within and between the HC and oculomotor systems such that investigating how HC responses ultimately influence neural activity in the oculomotor system, and the timing by which such neural modulation could occur is not trivial. We leveraged TheVirtualBrain, a software platform for large-scale network simulations, to model the functional dynamics that govern the interactions between the two systems in the macaque cortex. Evoked responses following the stimulation of the MTL and some, but not all, subfields of the HC resulted in observable responses in oculomotor regions, including the frontal eye fields (FEF), within the time of a gaze fixation. Modeled lesions to some MTL regions slowed the dissipation of HC signal to oculomotor regions, whereas HC lesions generally did not affect the rapid MTL activity propagation to oculomotor regions. These findings provide a framework for investigating how information represented by the HC/MTL may influence the oculomotor system during a fixation and predict how HC lesions may affect visual exploration.Author SummaryNo major account of oculomotor (eye movement) guidance considers the influence of the hippocampus (HC) and broader medial temporal lobe (MTL) system, yet it is clear that information is exchanged between the two systems. Prior experience influences current viewing, and cases of amnesia due to compromised HC/MTL function show specific alterations in viewing behaviour. By modeling large-scale network dynamics, we show that stimulation of subregions of the HC, and of the MTL, rapidly results in observable responses in oculomotor control regions, and that HC/MTL lesions alter signal propagation. These findings suggest that information from memory may readily guide visual exploration, and calls for a reconsideration of the neural circuitry involved in oculomotor guidance.

scholarly journals Large-scale intrinsic functional network organization along the long axis of the human medial temporal lobe

2015 ◽  
Vol 221 (6) ◽  
pp. 3237-3258 ◽  
Author(s):  
Shaozheng Qin ◽  
Xujun Duan ◽  
Kaustubh Supekar ◽  
Huafu Chen ◽  
Tianwen Chen ◽  
...  
Keyword(s):  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Large Scale ◽  
Functional Network ◽  
Network Organization

scholarly journals Visual mental imagery engages the left fusiform gyrus, but not the early visual cortex: a meta-analysis of neuroimaging evidence

2020 ◽  
Author(s):  
Alfredo Spagna ◽  
Dounia Hajhajate ◽  
Jianghao Liu ◽  
Paolo Bartolomeo
Keyword(s):  
Mental Imagery ◽  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Large Scale ◽  
Meta Analysis ◽  
Occipital Cortex ◽  
Neural Model ◽  
Fusiform Gyrus ◽  
Visual Mental Imagery ◽  
Early Visual Cortex

AbstractThe dominant neural model of visual mental imagery (VMI) stipulates that memories from the medial temporal lobe acquire sensory features in early visual areas. However, neurological patients with damage restricted to the occipital cortex typically show perfectly vivid VMI, while more anterior damages extending into the temporal lobe, especially in the left hemisphere, often cause VMI impairments. Here we present two major results reconciling neuroimaging findings in neurotypical subjects with the performance of brain-damaged patients: (1) a large-scale metaanalysis of 46 fMRI studies, of which 27 investigated specifically visual mental imagery, revealed that VMI engages fronto-parietal networks and a well-delimited region in the left fusiform gyrus. (2) A Bayesian analysis showing no evidence for imagery-related activity in early visual cortices. We propose a revised neural model of VMI that draws inspiration from recent cytoarchitectonic and lesion studies, whereby fronto-parietal networks initiate, modulate, and maintain activity in a core temporal network centered on the fusiform imagery node, a high-level visual region in the left fusiform gyrus.

scholarly journals Responses of Human Medial Temporal Lobe Neurons Are Modulated by Stimulus Repetition

2010 ◽  
Vol 103 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Carlos Pedreira ◽  
Florian Mormann ◽  
Alexander Kraskov ◽  
Moran Cerf ◽  
Itzhak Fried ◽  
...  
Keyword(s):  
Firing Rate ◽  
Temporal Lobe ◽  
Neural Activity ◽  
Medial Temporal Lobe ◽  
Declarative Memory ◽  
Stimulus Presentation ◽  
Single Neurons ◽  
Stimulus Repetition ◽  
Repeated Stimulus ◽  
Visual Inputs

Recent studies have reported the presence of single neurons with strong responses to visual inputs in the human medial temporal lobe. Here we show how repeated stimulus presentation—photos of celebrities and familiar individuals, landmark buildings, animals, and objects—modulates the firing rate of these cells: a consistent decrease in the neural activity was registered as images were repeatedly shown during experimental sessions. The effect of repeated stimulus presentation was not the same for all medial temporal lobe areas. These findings are consistent with the view that medial temporal lobe neurons link visual percepts to declarative memory.

scholarly journals Dissociable roles of the inferior longitudinal fasciculus and fornix in face and place perception

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Carl J Hodgetts ◽  
Mark Postans ◽  
Jonathan P Shine ◽  
Derek K Jones ◽  
Andrew D Lawrence ◽  
...  
Keyword(s):  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Scene Perception ◽  
Diffusion Tensor ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen ◽  
Bold Response ◽  
Blood Oxygen Level ◽  
Inferior Longitudinal Fasciculus ◽  
Healthy Participants

We tested a novel hypothesis, generated from representational accounts of medial temporal lobe (MTL) function, that the major white matter tracts converging on perirhinal cortex (PrC) and hippocampus (HC) would be differentially involved in face and scene perception, respectively. Diffusion tensor imaging was applied in healthy participants alongside an odd-one-out paradigm sensitive to PrC and HC lesions in animals and humans. Microstructure of inferior longitudinal fasciculus (ILF, connecting occipital and ventro-anterior temporal lobe, including PrC) and fornix (the main HC input/output pathway) correlated with accuracy on odd-one-out judgements involving faces and scenes, respectively. Similarly, blood oxygen level-dependent (BOLD) response in PrC and HC, elicited during oddity judgements, was correlated with face and scene oddity performance, respectively. We also observed associations between ILF and fornix microstructure and category-selective BOLD response in PrC and HC, respectively. These striking three-way associations highlight functionally dissociable, structurally instantiated MTL neurocognitive networks for complex face and scene perception.

Decoding Visual Inputs From Multiple Neurons in the Human Temporal Lobe

2007 ◽  
Vol 98 (4) ◽  
pp. 1997-2007 ◽  
Author(s):  
R. Quian Quiroga ◽  
L. Reddy ◽  
C. Koch ◽  
I. Fried
Keyword(s):  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Sensory Information ◽  
Single Neurons ◽  
Brain Machine Interfaces ◽  
Extracellular Recordings ◽  
Firing Rates ◽  
Visual Inputs ◽  
Human Temporal Lobe

We investigated the representation of visual inputs by multiple simultaneously recorded single neurons in the human medial temporal lobe, using their firing rates to infer which images were shown to subjects. The selectivity of these neurons was quantified with a novel measure. About four spikes per neuron, triggered between 300 and 600 ms after image onset in a handful of units (7.8 on average), predicted the identity of images far above chance. Decoding performance increased linearly with the number of units considered, peaked between 400 and 500 ms, did not improve when considering correlations among simultaneously recorded units, and generalized to very different images. The feasibility of decoding sensory information from human extracellular recordings has implications for the development of brain–machine interfaces.

scholarly journals When shared concept cells support associations: Theory of overlapping memory engrams

2021 ◽  
Vol 17 (12) ◽  
pp. e1009691
Author(s):  
Chiara Gastaldi ◽  
Tilo Schwalger ◽  
Emanuela De Falco ◽  
Rodrigo Quian Quiroga ◽  
Wulfram Gerstner
Keyword(s):  
Experimental Data ◽  
Neural Networks ◽  
Free Recall ◽  
Computational Model ◽  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Background Signal ◽  
Neural Assemblies ◽  
Model Match

Assemblies of neurons, called concepts cells, encode acquired concepts in human Medial Temporal Lobe. Those concept cells that are shared between two assemblies have been hypothesized to encode associations between concepts. Here we test this hypothesis in a computational model of attractor neural networks. We find that for concepts encoded in sparse neural assemblies there is a minimal fraction cmin of neurons shared between assemblies below which associations cannot be reliably implemented; and a maximal fraction cmax of shared neurons above which single concepts can no longer be retrieved. In the presence of a periodically modulated background signal, such as hippocampal oscillations, recall takes the form of association chains reminiscent of those postulated by theories of free recall of words. Predictions of an iterative overlap-generating model match experimental data on the number of concepts to which a neuron responds.

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