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Article ; Online: Active search signatures in a free-viewing task exploiting concurrent EEG and eye movements recordings.

Care, Damián / da Fonseca, María / Ison, Matias J / Kamienkowski, Juan E

2023 Volume 58, Issue 2, Page(s) 2563–2578

Abstract: Tasks we often perform in our everyday lives, such as reading or looking for a friend in the crowd, are seemingly straightforward but they actually require the orchestrated activity of several cognitive processes. Free-viewing visual search requires a ... ...

Abstract	Tasks we often perform in our everyday lives, such as reading or looking for a friend in the crowd, are seemingly straightforward but they actually require the orchestrated activity of several cognitive processes. Free-viewing visual search requires a plan to move our gaze on the different items, identifying them, and deciding on whether to continue with the search. Little is known about the electrophysiological signatures of these processes in free-viewing because there are technical challenges associated with eye movement artefacts. Here, we aimed to study how category information, as well as ecologically relevant variables such as the task performed, influence brain activity in a free-viewing paradigm. Participants were asked to observe/search from an array of faces and objects embedded in random noise. We concurrently recorded electroencephalogram and eye movements and applied a deconvolution analysis approach to estimate the contribution of the different elements embedded in the task. Consistent with classical fixed-gaze experiments and a handful of free-viewing studies, we found a robust categorical effect around 150 ms in occipital and occipitotemporal electrodes. We also report a task effect, more negative in posterior central electrodes in visual search compared with exploration, starting at around 80 ms. We also found significant effects of trial progression and an interaction with the task effect. Overall, these results generalise the characterisation of early visual face processing to a wider range of experiments and show how a suitable analysis approach allows to discern among multiple neural contributions to the signal, preserving key attributes of real-world tasks.
MeSH term(s)	Humans ; Eye Movements ; Electroencephalography ; Visual Perception/physiology ; Facial Recognition ; Fixation, Ocular
Language	English
Publishing date	2023-06-21
Publishing country	France
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	645180-9
ISSN	1460-9568 ; 0953-816X
ISSN (online)	1460-9568
ISSN	0953-816X
DOI	10.1111/ejn.16057
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Zs.A 2548: Show issues

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Article ; Online: Parsing a mental program: Fixation-related brain signatures of unitary operations and routines in natural visual search.

Kamienkowski, Juan E / Varatharajah, Alexander / Sigman, Mariano / Ison, Matias J

NeuroImage

2018 Volume 183, Page(s) 73–86

Abstract: Visual search involves a sequence or routine of unitary operations (i.e. fixations) embedded in a larger mental global program. The process can indeed be seen as a program based on a while loop (while the target is not found), a conditional construct ( ... ...

Abstract	Visual search involves a sequence or routine of unitary operations (i.e. fixations) embedded in a larger mental global program. The process can indeed be seen as a program based on a while loop (while the target is not found), a conditional construct (whether the target is matched or not based on specific recognition algorithms) and a decision making step to determine the position of the next searched location based on existent evidence. Recent developments in our ability to co-register brain scalp potentials (EEG) during free eye movements has allowed investigating brain responses related to fixations (fixation-Related Potentials; fERPs), including the identification of sensory and cognitive local EEG components linked to individual fixations. However, the way in which the mental program guiding the search unfolds has not yet been investigated. We performed an EEG and eye tracking co-registration experiment in which participants searched for a target face in natural images of crowds. Here we show how unitary steps of the program are encoded by specific local target detection signatures and how the positioning of each unitary operation within the global search program can be pinpointed by changes in the EEG signal amplitude as well as the signal power in different frequency bands. By simultaneously studying brain signatures of unitary operations and those occurring during the sequence of fixations, our study sheds light into how local and global properties are combined in implementing visual routines in natural tasks.
MeSH term(s)	Adult ; Attention/physiology ; Cerebral Cortex/physiology ; Electroencephalography/methods ; Evoked Potentials/physiology ; Evoked Potentials, Visual/physiology ; Eye Movement Measurements ; Eye Movements/physiology ; Facial Recognition/physiology ; Female ; Humans ; Male ; Space Perception/physiology ; Young Adult
Language	English
Publishing date	2018-08-08
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	1147767-2
ISSN	1095-9572 ; 1053-8119
ISSN (online)	1095-9572
ISSN	1053-8119
DOI	10.1016/j.neuroimage.2018.08.010
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Zs.A 3664: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (2.OG) ab Jg. 2022: Lesesaal (EG)
Zs.MO 7: Show issues

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Article ; Online: STDP Forms Associations between Memory Traces in Networks of Spiking Neurons.

Pokorny, Christoph / Ison, Matias J / Rao, Arjun / Legenstein, Robert / Papadimitriou, Christos / Maass, Wolfgang

Cerebral cortex (New York, N.Y. : 1991)

2019 Volume 30, Issue 3, Page(s) 952–968

Abstract: Memory traces and associations between them are fundamental for cognitive brain function. Neuron recordings suggest that distributed assemblies of neurons in the brain serve as memory traces for spatial information, real-world items, and concepts. ... ...

Abstract	Memory traces and associations between them are fundamental for cognitive brain function. Neuron recordings suggest that distributed assemblies of neurons in the brain serve as memory traces for spatial information, real-world items, and concepts. However, there is conflicting evidence regarding neural codes for associated memory traces. Some studies suggest the emergence of overlaps between assemblies during an association, while others suggest that the assemblies themselves remain largely unchanged and new assemblies emerge as neural codes for associated memory items. Here we study the emergence of neural codes for associated memory items in a generic computational model of recurrent networks of spiking neurons with a data-constrained rule for spike-timing-dependent plasticity. The model depends critically on 2 parameters, which control the excitability of neurons and the scale of initial synaptic weights. By modifying these 2 parameters, the model can reproduce both experimental data from the human brain on the fast formation of associations through emergent overlaps between assemblies, and rodent data where new neurons are recruited to encode the associated memories. Hence, our findings suggest that the brain can use both of these 2 neural codes for associations, and dynamically switch between them during consolidation.
MeSH term(s)	Action Potentials ; Humans ; Learning/physiology ; Memory/physiology ; Models, Neurological ; Neural Networks, Computer ; Neuronal Plasticity ; Neurons/physiology
Language	English
Publishing date	2019-08-10
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	1077450-6
ISSN	1460-2199 ; 1047-3211
ISSN (online)	1460-2199
ISSN	1047-3211
DOI	10.1093/cercor/bhz140
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Zs.A 3235: Show issues

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Article ; Online: Rapid Encoding of New Memories by Individual Neurons in the Human Brain.

Ison, Matias J / Quian Quiroga, Rodrigo / Fried, Itzhak

Neuron

2015 Volume 87, Issue 1, Page(s) 220–230

Abstract: The creation of memories about real-life episodes requires rapid neuronal changes that may appear after a single occurrence of an event. How is such demand met by neurons in the medial temporal lobe (MTL), which plays a fundamental role in episodic ... ...

Abstract	The creation of memories about real-life episodes requires rapid neuronal changes that may appear after a single occurrence of an event. How is such demand met by neurons in the medial temporal lobe (MTL), which plays a fundamental role in episodic memory formation? We recorded the activity of MTL neurons in neurosurgical patients while they learned new associations. Pairs of unrelated pictures, one of a person and another of a place, were used to construct a meaningful association modeling the episodic memory of meeting a person in a particular place. We found that a large proportion of responsive MTL neurons expanded their selectivity to encode these specific associations within a few trials: cells initially responsive to one picture started firing to the associated one but not to others. Our results provide a plausible neural substrate for the inception of associations, which are crucial for the formation of episodic memories.
MeSH term(s)	Adolescent ; Adult ; Amygdala/physiology ; Brain/physiology ; Brain Mapping ; Electrodes, Implanted ; Electroencephalography ; Entorhinal Cortex/physiology ; Epilepsy/physiopathology ; Female ; Hippocampus/cytology ; Hippocampus/physiology ; Humans ; Learning ; Male ; Memory/physiology ; Memory, Episodic ; Middle Aged ; Neurons/physiology ; Parahippocampal Gyrus/physiology ; Recognition, Psychology/physiology ; Temporal Lobe/cytology ; Temporal Lobe/physiology ; Young Adult
Language	English
Publishing date	2015-07-03
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
ZDB-ID	808167-0
ISSN	1097-4199 ; 0896-6273
ISSN (online)	1097-4199
ISSN	0896-6273
DOI	10.1016/j.neuron.2015.06.016
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Zs.A 2496: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (2.OG) ab Jg. 2022: Lesesaal (EG)
Zs.MG 92: Show issues

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Article: Selectivity and invariance for visual object perception.

Ison, Matias J / Quiroga, Rodrigo Quian

Frontiers in bioscience : a journal and virtual library

2008 Volume 13, Page(s) 4889–4903

Abstract: The sight of an object triggers a complex set of processes in the brain. Although it is already well established that object perception is performed by a hierarchical network, the so-called ventral visual pathway, we are only starting to understand how ... ...

Abstract	The sight of an object triggers a complex set of processes in the brain. Although it is already well established that object perception is performed by a hierarchical network, the so-called ventral visual pathway, we are only starting to understand how neurons along this pathway encode visual information at each processing stage. In this review, we discuss basic principles of neural coding for object perception and describe evidence showing that it mainly relies on two principles: selectivity and invariance.
MeSH term(s)	Animals ; Form Perception ; Humans ; Memory ; Neurons/physiology ; Pattern Recognition, Visual ; Retina/physiology ; Temporal Lobe/cytology ; Temporal Lobe/physiology ; Visual Pathways/physiology ; Visual Perception
Language	English
Publishing date	2008-05-01
Publishing country	United States
Document type	Journal Article ; Review
ZDB-ID	2141320-4
ISSN	1093-9946
ISSN	1093-9946
DOI	10.2741/3048
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Zs.A 5867: Show issues

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Article ; Online: Long-term coding of personal and universal associations underlying the memory web in the human brain.

De Falco, Emanuela / Ison, Matias J / Fried, Itzhak / Quian Quiroga, Rodrigo

Nature communications

2016 Volume 7, Page(s) 13408

Abstract: Neurons in the medial temporal lobe (MTL), a critical area for declarative memory, have been shown to change their tuning in associative learning tasks. Yet, it is unclear how durable these neuronal representations are and if they outlast the execution ... ...

Abstract	Neurons in the medial temporal lobe (MTL), a critical area for declarative memory, have been shown to change their tuning in associative learning tasks. Yet, it is unclear how durable these neuronal representations are and if they outlast the execution of the task. To address this issue, we studied the responses of MTL neurons in neurosurgical patients to known concepts (people and places). Using association scores provided by the patients and a web-based metric, here we show that whenever MTL neurons respond to more than one concept, these concepts are typically related. Furthermore, the degree of association between concepts could be successfully predicted based on the neurons' response patterns. These results provide evidence for a long-term involvement of MTL neurons in the representation of durable associations, a hallmark of human declarative memory.
MeSH term(s)	Algorithms ; Association Learning/physiology ; Brain/physiopathology ; Brain Mapping ; Electrodes ; Electrophysiology ; Epilepsy/physiopathology ; Humans ; Magnetic Resonance Imaging ; Memory/physiology ; Models, Neurological ; Neurons/physiology ; Photic Stimulation ; Temporal Lobe/physiopathology
Language	English
Publishing date	2016-11-15
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ISSN	2041-1723
ISSN (online)	2041-1723
DOI	10.1038/ncomms13408
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Encoding of long-term associations through neural unitization in the human medial temporal lobe.

Rey, Hernan G / De Falco, Emanuela / Ison, Matias J / Valentin, Antonio / Alarcon, Gonzalo / Selway, Richard / Richardson, Mark P / Quian Quiroga, Rodrigo

Nature communications

2018 Volume 9, Issue 1, Page(s) 4372

Abstract: Besides decades of research showing the role of the medial temporal lobe (MTL) in memory and the encoding of associations, the neural substrates underlying these functions remain unknown. We identified single neurons in the human MTL that responded to ... ...

Abstract	Besides decades of research showing the role of the medial temporal lobe (MTL) in memory and the encoding of associations, the neural substrates underlying these functions remain unknown. We identified single neurons in the human MTL that responded to multiple and, in most cases, associated stimuli. We observed that most of these neurons exhibit no differences in their spike and local field potential (LFP) activity associated with the individual response-eliciting stimuli. In addition, LFP responses in the theta band preceded single neuron responses by ~70 ms, with the single trial phase providing fine tuning of the spike response onset. We postulate that the finding of similar neuronal responses to associated items provides a simple and flexible way of encoding memories in the human MTL, increasing the effective capacity for memory storage and successful retrieval.
MeSH term(s)	Action Potentials/physiology ; Adult ; Electroencephalography ; Female ; Hippocampus/cytology ; Hippocampus/metabolism ; Humans ; Magnetic Resonance Imaging ; Male ; Middle Aged ; Neurons/metabolism ; Temporal Lobe/physiology
Language	English
Publishing date	2018-10-22
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2553671-0
ISSN	2041-1723 ; 2041-1723
ISSN (online)	2041-1723
ISSN	2041-1723
DOI	10.1038/s41467-018-06870-2
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Article ; Online: Fixation-related potentials in visual search: a combined EEG and eye tracking study.

Kamienkowski, Juan E / Ison, Matias J / Quiroga, Rodrigo Quian / Sigman, Mariano

Journal of vision

2012 Volume 12, Issue 7, Page(s) 4

Abstract: We report a study of concurrent eye movements and electroencephalographic (EEG) recordings while subjects freely explored a search array looking for hidden targets. We describe a sequence of fixation-event related potentials (fERPs) that unfolds during ∼ ...

Abstract	We report a study of concurrent eye movements and electroencephalographic (EEG) recordings while subjects freely explored a search array looking for hidden targets. We describe a sequence of fixation-event related potentials (fERPs) that unfolds during ∼ 400 ms following each fixation. This sequence highly resembles the event-related responses in a replay experiment, in which subjects kept fixation while a sequence of images occurred around the fovea simulating the spatial and temporal patterns during the free viewing experiment. Similar responses were also observed in a second control experiment where the appearance of stimuli was controlled by the experimenters and presented at the center of the screen. We also observed a relatively early component (∼150 ms) that distinguished between targets and distractors only in the freeviewing condition. We present a novel approach to match the critical properties of two conditions (targets/distractors), which can be readily adapted to other paradigms to investigate EEG components during free eye-movements.
MeSH term(s)	Adult ; Attention/physiology ; Electroencephalography/methods ; Evoked Potentials, Visual/physiology ; Eye Movements/physiology ; Female ; Fixation, Ocular/physiology ; Form Perception/physiology ; Fovea Centralis/physiology ; Humans ; Male ; Photic Stimulation/methods ; Reaction Time/physiology ; Space Perception/physiology ; Young Adult
Language	English
Publishing date	2012
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ISSN	1534-7362
ISSN (online)	1534-7362
DOI	10.1167/12.7.4
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: How many neurons can we see with current spike sorting algorithms?

Pedreira, Carlos / Martinez, Juan / Ison, Matias J / Quian Quiroga, Rodrigo

Journal of neuroscience methods

2012 Volume 211, Issue 1, Page(s) 58–65

Abstract: Recent studies highlighted the disagreement between the typical number of neurons observed with extracellular recordings and the ones to be expected based on anatomical and physiological considerations. This disagreement has been mainly attributed to the ...

Abstract	Recent studies highlighted the disagreement between the typical number of neurons observed with extracellular recordings and the ones to be expected based on anatomical and physiological considerations. This disagreement has been mainly attributed to the presence of sparsely firing neurons. However, it is also possible that this is due to limitations of the spike sorting algorithms used to process the data. To address this issue, we used realistic simulations of extracellular recordings and found a relatively poor spike sorting performance for simulations containing a large number of neurons. In fact, the number of correctly identified neurons for single-channel recordings showed an asymptotic behavior saturating at about 8-10 units, when up to 20 units were present in the data. This performance was significantly poorer for neurons with low firing rates, as these units were twice more likely to be missed than the ones with high firing rates in simulations containing many neurons. These results uncover one of the main reasons for the relatively low number of neurons found in extracellular recording and also stress the importance of further developments of spike sorting algorithms.
MeSH term(s)	Algorithms ; Cell Count/methods ; Computer Simulation ; Databases, Factual ; Electrophysiological Phenomena ; Extracellular Space/physiology ; False Positive Reactions ; Microelectrodes ; Neurons/physiology
Language	English
Publishing date	2012-07-25
Publishing country	Netherlands
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	282721-9
ISSN	1872-678X ; 0165-0270
ISSN (online)	1872-678X
ISSN	0165-0270
DOI	10.1016/j.jneumeth.2012.07.010
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Zs.A 1486: Show issues

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Article ; Online: Looking for a face in the crowd: fixation-related potentials in an eye-movement visual search task.

Kaunitz, Lisandro N / Kamienkowski, Juan E / Varatharajah, Alexander / Sigman, Mariano / Quiroga, Rodrigo Quian / Ison, Matias J

NeuroImage

2014 Volume 89, Page(s) 297–305

Abstract: Despite the compelling contribution of the study of event related potentials (ERPs) and eye movements to cognitive neuroscience, these two approaches have largely evolved independently. We designed an eye-movement visual search paradigm that allowed us ... ...

Abstract	Despite the compelling contribution of the study of event related potentials (ERPs) and eye movements to cognitive neuroscience, these two approaches have largely evolved independently. We designed an eye-movement visual search paradigm that allowed us to concurrently record EEG and eye movements while subjects were asked to find a hidden target face in a crowded scene with distractor faces. Fixation event-related potentials (fERPs) to target and distractor stimuli showed the emergence of robust sensory components associated with the perception of stimuli and cognitive components associated with the detection of target faces. We compared those components with the ones obtained in a control task at fixation: qualitative similarities as well as differences in terms of scalp topography and latency emerged between the two. By using single trial analyses, fixations to target and distractors could be decoded from the EEG signals above chance level in 11 out of 12 subjects. Our results show that EEG signatures related to cognitive behavior develop across spatially unconstrained exploration of natural scenes and provide a first step towards understanding the mechanisms of target detection during natural search.
MeSH term(s)	Adult ; Brain/physiology ; Electroencephalography ; Evoked Potentials, Visual ; Face ; Female ; Fixation, Ocular/physiology ; Humans ; Male ; Photic Stimulation ; Saccades/physiology ; Visual Perception/physiology ; Young Adult
Language	English
Publishing date	2014-04-01
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	1147767-2
ISSN	1095-9572 ; 1053-8119
ISSN (online)	1095-9572
ISSN	1053-8119
DOI	10.1016/j.neuroimage.2013.12.006
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Zs.A 3664: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (2.OG) ab Jg. 2022: Lesesaal (EG)
Zs.MO 7: Show issues

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