scholarly journals A temporal record of the past with a spectrum of time constants in the monkey entorhinal cortex

2019 ◽  
Author(s):  
Ian M. Bright ◽  
Miriam L.R. Meister ◽  
Nathanael A. Cruzado ◽  
Zoran Tiganj ◽  
Elizabeth A. Buffalo ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Large Deviations ◽  
Time Scales ◽  
Entorhinal Cortex ◽  
Brain Regions ◽  
Relaxation Rates ◽  
Time Constants ◽  
Macaque Monkeys ◽  
The Past ◽  
Memory Code

AbstractEpisodic memory is believed to be intimately related to our experience of the passage of time. Indeed, neurons in the hippocampus and other brain regions critical to episodic memory code for the passage of time at a range of time scales. The origin of this temporal signal, however, remains unclear. Here, we examined temporal responses in the entorhinal cortex of macaque monkeys as they viewed complex images. Many neurons in the entorhinal cortex were responsive to image onset, showing large deviations from baseline firing shortly after image onset but relaxing back to baseline at different rates. This range of relaxation rates allowed for the time since image onset to be decoded on the scale of seconds. Further, these neurons carried information about image content, suggesting that neurons in the entorhinal cortex carry information not only about when an event took place but also the identity of that event. Taken together, these findings suggest that the primate entorhinal cortex uses a spectrum of time constants to construct a temporal record of the past in support of episodic memory.

scholarly journals A temporal record of the past with a spectrum of time constants in the monkey entorhinal cortex

2020 ◽  
Vol 117 (33) ◽  
pp. 20274-20283 ◽  
Author(s):  
Ian M. Bright ◽  
Miriam L. R. Meister ◽  
Nathanael A. Cruzado ◽  
Zoran Tiganj ◽  
Elizabeth A. Buffalo ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Large Deviations ◽  
Entorhinal Cortex ◽  
Brain Regions ◽  
Relaxation Rates ◽  
Image Content ◽  
Time Constants ◽  
Macaque Monkeys ◽  
The Past ◽  
Memory Code

Episodic memory is believed to be intimately related to our experience of the passage of time. Indeed, neurons in the hippocampus and other brain regions critical to episodic memory code for the passage of time at a range of timescales. The origin of this temporal signal, however, remains unclear. Here, we examined temporal responses in the entorhinal cortex of macaque monkeys as they viewed complex images. Many neurons in the entorhinal cortex were responsive to image onset, showing large deviations from baseline firing shortly after image onset but relaxing back to baseline at different rates. This range of relaxation rates allowed for the time since image onset to be decoded on the scale of seconds. Further, these neurons carried information about image content, suggesting that neurons in the entorhinal cortex carry information about not only when an event took place but also, the identity of that event. Taken together, these findings suggest that the primate entorhinal cortex uses a spectrum of time constants to construct a temporal record of the past in support of episodic memory.

scholarly journals Behavioral evidence for memory replay of video episodes in macaque monkeys

2020 ◽  
Author(s):  
Shuzhen Zuo ◽  
Lei Wang ◽  
Junghan Shin ◽  
Yudian Cai ◽  
Sang Wan Lee ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Rhesus Monkeys ◽  
Temporal Order ◽  
Irrelevant Information ◽  
Macaque Monkeys ◽  
The Past ◽  
Non Linear ◽  
Temporal Order Judgement ◽  
Behavioral Evidence ◽  
Past Experiences

ABSTRACTHumans recall the past by replaying fragments of events temporally. Here, we demonstrate a similar effect in macaques. We trained six rhesus monkeys with a temporal-order judgement (TOJ) task and collected 5000 TOJ trials. In each trial, they watched a naturalistic video of about 10 s comprising two across-context clips, and after a 2-s delay, performed TOJ between two frames from the video. The monkeys apply a non-linear forward, time-compressed replay mechanism during the temporal-order judgement. In contrast with humans, such compression of replay is however not sophisticated enough to allow them to skip over irrelevant information by compressing the encoded video globally. We also reveal that the monkeys detect event contextual boundaries and such detection facilitates recall by an increased rate of information accumulation. Demonstration of a time-compressed, forward replay like pattern in the macaque monkeys provides insights into the evolution of episodic memory in our lineage.Impact StatementMacaque monkeys temporally compress past experiences and use a forward-replay mechanism during judgment of temporal-order between episodes.

scholarly journals Metric and chronological time in human episodic memory

2020 ◽  
Author(s):  
Hallvard Røe Evensmoen ◽  
Lars M. Rimol ◽  
Henning Hoel Rise ◽  
Tor Ivar Hansen ◽  
Hamed Nili ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Time Scales ◽  
Entorhinal Cortex ◽  
Medial Temporal Lobe ◽  
Brain Network ◽  
Parahippocampal Cortex ◽  
Temporal Pole ◽  
Episodic Memories ◽  
Short Time ◽  
Chronological Time

The relative contributions of metric and chronological time in the encoding of episodic memories are unknown. One hundred one healthy young adults viewed 48 unique episodes of visual events and were later tested on recall of the order of events (chronological time) and the precise timing of events (metric time). The behavioral results show that metric recall accuracy correlates with chronological accuracy for events within episodes, but does not play a role on larger time-scales across episodes. Functional magnetic resonance imaging during encoding and recall showed that metric time was represented in the posterior medial entorhinal cortex, as well as the temporal pole and the cerebellum, whereas chronological time was represented in a widespread brain network including the anterior lateral entorhinal cortex, hippocampus, parahippocampal cortex and the prefrontal cortex. We conclude that metric time has a role in episodic memory on short time-scales and is mainly subserved by medial temporal lobe structures.

Neuro-Clinical Signatures of Language Impairments: A Theoretical Framework for Function-to-structure Mapping in Clinics

2020 ◽  
Vol 20 (9) ◽  
pp. 800-811 ◽  
Author(s):  
Ferath Kherif ◽  
Sandrine Muller
Keyword(s):  
Brain Mapping ◽  
Theoretical Framework ◽  
Brain Regions ◽  
Language Impairments ◽  
Structure Mapping ◽  
Language Functions ◽  
The Past ◽  
Language Recovery ◽  
The Brain ◽  
Bow Tie

In the past decades, neuroscientists and clinicians have collected a considerable amount of data and drastically increased our knowledge about the mapping of language in the brain. The emerging picture from the accumulated knowledge is that there are complex and combinatorial relationships between language functions and anatomical brain regions. Understanding the underlying principles of this complex mapping is of paramount importance for the identification of the brain signature of language and Neuro-Clinical signatures that explain language impairments and predict language recovery after stroke. We review recent attempts to addresses this question of language-brain mapping. We introduce the different concepts of mapping (from diffeomorphic one-to-one mapping to many-to-many mapping). We build those different forms of mapping to derive a theoretical framework where the current principles of brain architectures including redundancy, degeneracy, pluri-potentiality and bow-tie network are described.

scholarly journals Emotional Reactions to Music in Dementia Patients and Healthy Controls: Differential Responding Depends on the Mechanism

2021 ◽  
Vol 4 ◽  
pp. 205920432110101
Author(s):  
Gonçalo T. Barradas ◽  
Patrik N. Juslin ◽  
Sergi Bermúdez i Badia
Keyword(s):  
Episodic Memory ◽  
Brain Stem ◽  
Geriatric Depression Scale ◽  
Depression Scale ◽  
Basic Research ◽  
Brain Regions ◽  
Emotional Reactions ◽  
Dementia Patients ◽  
Significant Difference ◽  
Brain Stem Reflex

Music is frequently regarded as a unique way to connect with dementia patients. Yet little is known about how persons with dementia respond emotionally to music. Are their responses different from those of healthy listeners? If so, why? The present study makes a first attempt to tackle these issues in a Portuguese context, with a focus on psychological mechanisms. In Experiment 1, featuring 20 young and healthy adults, we found that musical excerpts which have previously been shown to activate specific emotion induction mechanisms (brain stem reflex, contagion, episodic memory, musical expectancy) in Sweden were valid and yielded predicted emotions also in Portugal, as indexed by self-reported feelings, psychophysiology, and post hoc mechanism indices. In Experiment 2, we used the same stimuli to compare the responses of 20 elderly listeners diagnosed with Alzheimer’s disease (AD) with those of 20 healthy listeners. We controlled for cognitive functioning (Mini-Mental State Examination) and depression (Geriatric Depression Scale). Our predictions about how mechanisms would be differentially affected by decline in brain regions associated with AD received support in that AD patients reported significantly lower levels of (a) sadness in the contagion condition, (b) happiness and nostalgia in the episodic memory condition, and (c) anxiety in the musical expectancy condition. By contrast, no significant difference in reported surprise was found in the brain stem reflex condition. Implications for musical interventions aimed at dementia are discussed, highlighting the key role that basic research may play in developing applications.

scholarly journals Entorhinal cortex volume is associated with episodic memory related brain activation in normal aging and amnesic mild cognitive impairment

2011 ◽  
Vol 5 (2) ◽  
pp. 126-136 ◽  
Author(s):  
Mehul A. Trivedi ◽  
Travis R. Stoub ◽  
Christopher M. Murphy ◽  
Sarah George ◽  
Leyla deToledo-Morrell ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
Mild Cognitive Impairment ◽  
Episodic Memory ◽  
Entorhinal Cortex ◽  
Brain Activation ◽  
Normal Aging ◽  
Amnesic Mild Cognitive Impairment

scholarly journals Effects of amnesia on processing in the hippocampus and default mode network during a naturalistic memory task: a case study

2018 ◽  
Author(s):  
Christiane Oedekoven ◽  
James L. Keidel ◽  
Stuart Anderson ◽  
Angus Nisbet ◽  
Chris Bird
Keyword(s):  
Functional Connectivity ◽  
Episodic Memory ◽  
Memory Performance ◽  
Memory Task ◽  
Structural Mri ◽  
Brain Regions ◽  
Left Hippocampus ◽  
Cortical Regions ◽  
The Right ◽  
Encoding And Retrieval

Despite their severely impaired episodic memory, individuals with amnesia are able to comprehend ongoing events. Online representations of a current event are thought to be supported by a network of regions centred on the posterior midline cortex (PMC). By contrast, episodic memory is widely believed to be supported by interactions between the hippocampus and these cortical regions. In this MRI study, we investigated the encoding and retrieval of lifelike events (video clips) in a patient with severe amnesia likely resulting from a stroke to the right thalamus, and a group of 20 age-matched controls. Structural MRI revealed grey matter reductions in left hippocampus and left thalamus in comparison to controls. We first characterised the regions activated in the controls while they watched and retrieved the videos. There were no differences in activation between the patient and controls in any of the regions. We then identified a widespread network of brain regions, including the hippocampus, that were functionally connected with the PMC in controls. However, in the patient there was a specific reduction in functional connectivity between the PMC and a region of left hippocampus when both watching and attempting to retrieve the videos. A follow up analysis revealed that in controls the functional connectivity between these regions when watching the videos was correlated with memory performance. Taken together, these findings support the view that the interactions between the PMC and the hippocampus enable the encoding and retrieval of multimodal representations of the contents of an event.

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