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1.
J Neurosci ; 40(3): 682-693, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31754015

RESUMO

Memory deficits are common in epilepsy patients. In these patients, the interictal EEG commonly shows interictal epileptiform discharges (IEDs). While IEDs are associated with transient cognitive impairments, it remains poorly understood why this is. We investigated the effects of human (male and female) hippocampal IEDs on single-neuron activity during a memory task in patients with medically refractory epilepsy undergoing depth electrode monitoring. We quantified the effects of hippocampal IEDs on single-neuron activity and the impact of this modulation on subjectively declared memory strength. Across all recorded neurons, the activity of 50 of 728 neurons were significantly modulated by IEDs, with the strongest modulation in the medial temporal lobe (33 of 416) and in particular the right hippocampus (12 of 58). Putative inhibitory neurons, as identified by their extracellular signature, were more likely to be modulated by IEDs than putative excitatory neurons (19 of 157 vs 31 of 571). Behaviorally, the occurrence of hippocampal IEDs was accompanied by a disruption of recognition of familiar images only if they occurred up to 2 s before stimulus onset. In contrast, IEDs did not impair encoding or recognition of novel images, indicating high temporal and task specificity of the effects of IEDs. The degree of modulation of individual neurons by an IED correlated with the declared confidence of a retrieval trial, with higher firing rates indicative of reduced confidence. Together, these data link the transient modulation of individual neurons by IEDs to specific declarative memory deficits in specific cell types, thereby revealing a mechanism by which IEDs disrupt medial temporal lobe-dependent declarative memory retrieval processes.SIGNIFICANCE STATEMENT Interictal epileptiform discharges (IEDs) are thought to be a cause of memory deficits in chronic epilepsy patients, but the underlying mechanisms are not understood. Utilizing single-neuron recordings in epilepsy patients, we found that hippocampal IEDs transiently change firing of hippocampal neurons and disrupted selectively the retrieval, but not encoding, of declarative memories. The extent of the modulation of the individual firing of hippocampal neurons by an IED predicted the extent of reduction of subjective retrieval confidence. Together, these data reveal a specific kind of transient cognitive impairment caused by IEDs and link this impairment to the modulation of the activity of individual neurons. Understanding the mechanisms by which IEDs impact memory is critical for understanding memory impairments in epilepsy patients.

2.
Brain ; 142(11): 3530-3549, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31549164

RESUMO

The medial frontal cortex is important for goal-directed behaviours such as visual search. The pre-supplementary motor area (pre-SMA) plays a critical role in linking higher-level goals to actions, but little is known about the responses of individual cells in this area in humans. Pre-SMA dysfunction is thought to be a critical factor in the cognitive deficits that are observed in diseases such as Parkinson's disease and schizophrenia, making it important to develop a better mechanistic understanding of the pre-SMA's role in cognition. We simultaneously recorded single neurons in the human pre-SMA and eye movements while subjects performed goal-directed visual search tasks. We characterized two groups of neurons in the pre-SMA. First, 40% of neurons changed their firing rate whenever a fixation landed on the search target. These neurons responded to targets in an abstract manner across several conditions and tasks. Responses were invariant to motor output (i.e. button press or not), and to different ways of defining the search target (by instruction or pop-out). Second, ∼50% of neurons changed their response as a function of fixation order. Together, our results show that human pre-SMA neurons carry abstract signals during visual search that indicate whether a goal was reached in an action- and cue-independent manner. This suggests that the pre-SMA contributes to goal-directed behaviour by flexibly signalling goal detection and time elapsed since start of the search, and this process occurs regardless of task. These observations provide insights into how pre-SMA dysfunction might impact cognitive function.

3.
Ann N Y Acad Sci ; 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31407811

RESUMO

Recent work has revealed important new discoveries on the cellular mechanisms of working memory (WM). These findings have motivated several seemingly conflicting theories on the mechanisms of short-term memory maintenance. Here, we summarize the key insights gained from these new experiments and critically evaluate them in light of three hypotheses: classical persistent activity, activity-silent, and dynamic coding. The experiments discussed include the first direct demonstration of persistently active neurons in the human medial temporal lobe that form static attractors with relevance to WM, single-neuron recordings in the macaque prefrontal cortex that show evidence for both persistent and more dynamic types of WM representations, and noninvasive neuroimaging in humans that argues for activity-silent representations. A key insight that emerges from these new results is that there are several neural mechanisms that support the maintenance of information in WM. Finally, based on established cognitive theories of WM, we propose a coherent model that encompasses these seemingly contradictory results. We propose that the three neuronal mechanisms of persistent activity, activity-silent, and dynamic coding map well onto the cognitive levels of information processing (within focus of attention, activated long-term memory, and central executive) that Cowan's WM model proposes.

4.
J Vis Exp ; (148)2019 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-31259902

RESUMO

Intracranial recordings from patients with intractable epilepsy provide a unique opportunity to study the activity of individual human neurons during active behavior. An important tool for quantifying behavior is eye tracking, which is an indispensable tool for studying visual attention. However, eye tracking is challenging to use concurrently with invasive electrophysiology and this approach has consequently been little used. Here, we present a proven experimental protocol to conduct single-neuron recordings with simultaneous eye tracking in humans. We describe how the systems are connected and the optimal settings to record neurons and eye movements. To illustrate the utility of this method, we summarize results that were made possible by this setup. This data shows how using eye tracking in a memory-guided visual search task allowed us to describe a new class of neurons called target neurons, whose response was reflective of top-down attention to the current search target. Lastly, we discuss the significance and solutions to potential problems of this setup. Together, our protocol and results suggest that single-neuron recordings with simultaneous eye tracking in humans are an effective method to study human brain function. It provides a key missing link between animal neurophysiology and human cognitive neuroscience.

5.
J Cogn Neurosci ; 31(9): 1290-1307, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31037988

RESUMO

Holding information in working memory (WM) is an active and effortful process that is accompanied by sustained load-dependent changes in oscillatory brain activity. These proportional power increases are often reported in EEG studies recording theta over frontal midline sites. Intracranial recordings, however, yield mixed results, depending on the brain area being recorded from. We recorded intracranial EEG with depth electrodes in 13 patients with epilepsy who were performing a Sternberg WM task. Here, we investigated patterns of theta power changes as a function of memory load during maintenance in three areas critical for WM: dorsolateral prefrontal cortex (DLPFC), dorsal ACC (dACC), and hippocampus. Theta frequency power in both hippocampus and dACC increased during maintenance. In contrast, theta frequency power in the DLPFC decreased during maintenance, and this decrease was proportional to memory load. Only the power decreases in DLPFC, but not the power increases in hippocampus and dACC, were predictive of behavior in a given trial. The extent of the load-related theta power decreases in the DLPFC in a given participant predicted a participant's RTs, revealing that DLPFC theta explains individual differences in WM ability between participants. Together, these data reveal a pattern of theta power decreases in the DLPFC that is predictive of behavior and that is opposite of that in other brain areas. This result suggests that theta band power changes serve different cognitive functions in different brain areas and specifically that theta power decreases in DLPFC have an important role in maintenance of information.

6.
Trends Cogn Sci ; 23(6): 510-524, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31031021

RESUMO

Deciphering the mechanisms of declarative memory is a major goal of neuroscience. While much theoretical progress has been made, it has proven difficult to experimentally verify key predictions of some foundational models of memory. Recently, single-neuron recordings in human patients have started to provide direct experimental verification of some theories, including mnemonic evidence accumulation, balance-of-evidence for confidence judgments, sparse coding, contextual reinstatement, and the ventral tegmental area (VTA)-hippocampus loop model. Here, we summarize the cell types that have been described in the medial temporal lobe and posterior parietal cortex, discuss their properties, and reflect on how these findings inform theoretical work. This body of work exemplifies the scientific power of a synergistic combination of modeling and human single-neuron recordings to advance cognitive neuroscience.

7.
Neuron ; 101(1): 165-177.e5, 2019 01 02.
Artigo em Inglês | MEDLINE | ID: mdl-30528064

RESUMO

Humans can self-monitor errors without explicit feedback, resulting in behavioral adjustments on subsequent trials such as post-error slowing (PES). The error-related negativity (ERN) is a well-established macroscopic scalp EEG correlate of error self-monitoring, but its neural origins and relationship to PES remain unknown. We recorded in the frontal cortex of patients performing a Stroop task and found neurons that track self-monitored errors and error history in dorsal anterior cingulate cortex (dACC) and pre-supplementary motor area (pre-SMA). Both the intracranial ERN (iERN) and error neuron responses appeared first in pre-SMA, and ∼50 ms later in dACC. Error neuron responses were correlated with iERN amplitude on individual trials. In dACC, such error neuron-iERN synchrony and responses of error-history neurons predicted the magnitude of PES. These data reveal a human single-neuron correlate of the ERN and suggest that dACC synthesizes error information to recruit behavioral control through coordinated neural activity.


Assuntos
Eletroencefalografia/métodos , Neurônios/fisiologia , Córtex Pré-Frontal/diagnóstico por imagem , Córtex Pré-Frontal/fisiologia , Desempenho Psicomotor/fisiologia , Tempo de Reação/fisiologia , Potenciais de Ação/fisiologia , Feminino , Humanos , Imagem por Ressonância Magnética/métodos , Masculino , Estimulação Luminosa/métodos
8.
Stereotact Funct Neurosurg ; 96(5): 311-319, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30326475

RESUMO

BACKGROUND: Invasive electrode monitoring provides more precise localization of epileptogenic foci in patients with medically refractory epilepsy. The use of hybrid depth electrodes that include microwires for simultaneous single-neuron monitoring is becoming more widespread. OBJECTIVE: To determine the safety and utility of hybrid depth electrodes for intracranial monitoring of medically refractory epilepsy. METHODS: We reviewed the medical charts of 53 cases of medically refractory epilepsy operated on from 2006 to 2017, where both non-hybrid and hybrid microwire depth electrodes were used for intracranial monitoring. We assessed the localization accuracy and complications that arose to assess the relative safety and utility of hybrid depth electrodes compared with standard electrodes. RESULTS: A total of 555 electrodes were implanted in 52 patients. The overall per-electrode complication rate was 2.3%, with a per-case complication rate of 20.8%. There were no infections or deaths. Serious or hemorrhagic complications occurred in 2 patients (0.4% per-electrode risk). Complications did not correlate with the use of any particular electrode type, and hybrids were equally as reliable as standard electrodes in localizing seizure onset zones. CONCLUSIONS: Hybrid depth electrodes appear to be as safe and effective as standard depth electrodes for intracranial monitoring and provide unique opportunities to study the human brain at single-neuron resolution.


Assuntos
Epilepsia Resistente a Medicamentos/diagnóstico por imagem , Eletrodos Implantados , Monitorização Neurofisiológica Intraoperatória/métodos , Neurônios/fisiologia , Convulsões/diagnóstico por imagem , Adulto , Epilepsia Resistente a Medicamentos/fisiopatologia , Epilepsia Resistente a Medicamentos/cirurgia , Eletrodos Implantados/normas , Eletroencefalografia/métodos , Eletroencefalografia/normas , Feminino , Humanos , Monitorização Neurofisiológica Intraoperatória/normas , Masculino , Pessoa de Meia-Idade , Convulsões/fisiopatologia , Convulsões/cirurgia
9.
Curr Biol ; 28(13): 2058-2069.e4, 2018 07 09.
Artigo em Inglês | MEDLINE | ID: mdl-29910078

RESUMO

Neurons in the primate medial temporal lobe (MTL) respond selectively to visual categories such as faces, contributing to how the brain represents stimulus meaning. However, it remains unknown whether MTL neurons continue to encode stimulus meaning when it changes flexibly as a function of variable task demands imposed by goal-directed behavior. While classically associated with long-term memory, recent lesion and neuroimaging studies show that the MTL also contributes critically to the online guidance of goal-directed behaviors such as visual search. Do such tasks modulate responses of neurons in the MTL, and if so, do their responses mirror bottom-up input from visual cortices or do they reflect more abstract goal-directed properties? To answer these questions, we performed concurrent recordings of eye movements and single neurons in the MTL and medial frontal cortex (MFC) in human neurosurgical patients performing a memory-guided visual search task. We identified a distinct population of target-selective neurons in both the MTL and MFC whose response signaled whether the currently fixated stimulus was a target or distractor. This target-selective response was invariant to visual category and predicted whether a target was detected or missed behaviorally during a given fixation. The response latencies, relative to fixation onset, of MFC target-selective neurons preceded those in the MTL by ∼200 ms, suggesting a frontal origin for the target signal. The human MTL thus represents not only fixed stimulus identity, but also task-specified stimulus relevance due to top-down goal relevance.


Assuntos
Encéfalo/fisiologia , Memória/fisiologia , Neurônios/fisiologia , Tempo de Reação/fisiologia , Lobo Temporal/fisiologia , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
10.
J Neurosci ; 38(17): 4200-4211, 2018 04 25.
Artigo em Inglês | MEDLINE | ID: mdl-29615486

RESUMO

Cognitive psychologists have long hypothesized that experiences are encoded in a temporal context that changes gradually over time. When an episodic memory is retrieved, the state of context is recovered-a jump back in time. We recorded from single units in the medial temporal lobe of epilepsy patients performing an item recognition task. The population vector changed gradually over minutes during presentation of the list. When a probe from the list was remembered with high confidence, the population vector reinstated the temporal context of the original presentation of that probe during study, a neural contiguity effect that provides a possible mechanism for behavioral contiguity effects. This pattern was only observed for well remembered probes; old probes that were not well remembered showed an anti-contiguity effect. These results constitute the first direct evidence that recovery of an episodic memory in humans is associated with retrieval of a gradually changing state of temporal context, a neural "jump back in time" that parallels the act of remembering.SIGNIFICANCE STATEMENT Episodic memory is the ability to relive a specific experience from one's life. For decades, researchers have hypothesized that, unlike other forms of memory that can be described as simple associations between stimuli, episodic memory depends on the recovery of a neural representation of spatiotemporal context. During study of a sequence of stimuli, the brain state of epilepsy patients changed slowly over at least a minute. When the participant remembered a particular event from the list, this gradually changing state was recovered. This provides direct confirmation of the prediction from computational models of episodic memory. The resolution of this point means that the study of episodic memory can focus on the mechanisms by which this representation of spatiotemporal context is maintained and sometimes recovered.


Assuntos
Memória Episódica , Lobo Temporal/fisiologia , Epilepsia do Lobo Temporal/fisiopatologia , Feminino , Humanos , Masculino , Rememoração Mental , Reconhecimento Visual de Modelos , Lobo Temporal/fisiopatologia
11.
Curr Biol ; 28(9): 1333-1343.e4, 2018 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-29657115

RESUMO

The encoding of information into long-term declarative memory is facilitated by dopamine. This process depends on hippocampal novelty signals, but it remains unknown how midbrain dopaminergic neurons are modulated by declarative-memory-based information. We recorded individual substantia nigra (SN) neurons and cortical field potentials in human patients performing a recognition memory task. We found that 25% of SN neurons were modulated by stimulus novelty. Extracellular waveform shape and anatomical location indicated that these memory-selective neurons were putatively dopaminergic. The responses of memory-selective neurons appeared 527 ms after stimulus onset, changed after a single trial, and were indicative of recognition accuracy. SN neurons phase locked to frontal cortical theta-frequency oscillations, and the extent of this coordination predicted successful memory formation. These data reveal that dopaminergic neurons in the human SN are modulated by memory signals and demonstrate a progression of information flow in the hippocampal-basal ganglia-frontal cortex loop for memory encoding.


Assuntos
Córtex Cerebral/fisiopatologia , Neurônios Dopaminérgicos/patologia , Tremor Essencial/fisiopatologia , Memória/fisiologia , Doença de Parkinson/fisiopatologia , Tempo de Reação , Substância Negra/patologia , Eletrodos , Tremor Essencial/psicologia , Humanos , Doença de Parkinson/psicologia , Estimulação Luminosa , Análise e Desempenho de Tarefas
12.
Neural Comput ; 30(5): 1359-1393, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29566357

RESUMO

Finding actions that satisfy the constraints imposed by both external inputs and internal representations is central to decision making. We demonstrate that some important classes of constraint satisfaction problems (CSPs) can be solved by networks composed of homogeneous cooperative-competitive modules that have connectivity similar to motifs observed in the superficial layers of neocortex. The winner-take-all modules are sparsely coupled by programming neurons that embed the constraints onto the otherwise homogeneous modular computational substrate. We show rules that embed any instance of the CSP's planar four-color graph coloring, maximum independent set, and sudoku on this substrate and provide mathematical proofs that guarantee these graph coloring problems will convergence to a solution. The network is composed of nonsaturating linear threshold neurons. Their lack of right saturation allows the overall network to explore the problem space driven through the unstable dynamics generated by recurrent excitation. The direction of exploration is steered by the constraint neurons. While many problems can be solved using only linear inhibitory constraints, network performance on hard problems benefits significantly when these negative constraints are implemented by nonlinear multiplicative inhibition. Overall, our results demonstrate the importance of instability rather than stability in network computation and offer insight into the computational role of dual inhibitory mechanisms in neural circuits.


Assuntos
Modelos Neurológicos , Neocórtex/citologia , Rede Nervosa/fisiologia , Neurônios/fisiologia , Resolução de Problemas/fisiologia , Animais , Simulação por Computador , Humanos , Dinâmica não Linear
13.
Sci Data ; 5: 180010, 2018 02 13.
Artigo em Inglês | MEDLINE | ID: mdl-29437158

RESUMO

We present a dataset of 1,576 single neurons recorded from the human amygdala and hippocampus in 65 sessions from 42 patients undergoing intracranial monitoring for localization of epileptic seizures. Subjects performed a recognition memory task with pictures as stimuli. Subjects were asked to identify whether they had seen a particular image the first time ('new') or second time ('old') on a 1-6 confidence scale. This comprehensive dataset includes the spike times of all neurons and their extracellular waveforms, behavior, electrode locations determined from post-operative MRI scans, demographics, and the stimuli shown. As technical validation, we provide spike sorting quality metrics and assessment of tuning of cells to verify the presence of visually-and memory selective cells. We also provide analysis code that reproduces key scientific findings published previously on a smaller version of this dataset. Together, this large dataset will facilitate the investigation of the neural mechanism of declarative memory by providing a substantial number of hard to obtain human single-neuron recordings during a well characterized behavioral task.


Assuntos
Tonsila do Cerebelo , Hipocampo , Memória , Neurônios , Lobo Temporal , Tonsila do Cerebelo/citologia , Tonsila do Cerebelo/fisiologia , Hipocampo/citologia , Hipocampo/fisiologia , Humanos , Imagem por Ressonância Magnética , Neurônios/fisiologia , Lobo Temporal/citologia , Lobo Temporal/fisiologia
14.
Trends Cogn Sci ; 22(1): 5-7, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29100736

RESUMO

A recent single-neuron study revealed an anatomical anterior-to-posterior gradient of awareness-related responses by 'concept neurons' in the human medial temporal lobe (MTL). Delayed and weaker responses were indicative of the failure of a stimulus to reach awareness, suggesting that reliable fast responses are a critical aspect of the neural mechanisms of consciousness.


Assuntos
Intermitência na Atenção Visual , Estado de Consciência , Conscientização , Humanos , Neurônios , Lobo Temporal
15.
Neuron ; 97(1): 209-220.e3, 2018 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-29249283

RESUMO

The human posterior parietal cortex (PPC) is thought to contribute to memory retrieval, but little is known about its specific role. We recorded single PPC neurons of two human tetraplegic subjects implanted with microelectrode arrays, who performed a recognition memory task. We found two groups of neurons that signaled memory-based choices. Memory-selective neurons preferred either novel or familiar stimuli, scaled their response as a function of confidence, and signaled subjective choices regardless of truth. Confidence-selective neurons signaled confidence regardless of stimulus familiarity. Memory-selective signals appeared 553 ms after stimulus onset, but before action onset. Neurons also encoded spoken numbers, but these number-tuned neurons did not carry recognition signals. Together, this functional separation reveals action-independent coding of declarative memory-based familiarity and confidence of choices in human PPC. These data suggest that, in addition to sensory-motor integration, a function of human PPC is to utilize memory signals to make choices.


Assuntos
Comportamento de Escolha/fisiologia , Memória/fisiologia , Neurônios/fisiologia , Lobo Parietal/fisiologia , /fisiologia , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
17.
Nat Commun ; 8: 14821, 2017 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-28429707

RESUMO

The human amygdala is a key structure for processing emotional facial expressions, but it remains unclear what aspects of emotion are processed. We investigated this question with three different approaches: behavioural analysis of 3 amygdala lesion patients, neuroimaging of 19 healthy adults, and single-neuron recordings in 9 neurosurgical patients. The lesion patients showed a shift in behavioural sensitivity to fear, and amygdala BOLD responses were modulated by both fear and emotion ambiguity (the uncertainty that a facial expression is categorized as fearful or happy). We found two populations of neurons, one whose response correlated with increasing degree of fear, or happiness, and a second whose response primarily decreased as a linear function of emotion ambiguity. Together, our results indicate that the human amygdala processes both the degree of emotion in facial expressions and the categorical ambiguity of the emotion shown and that these two aspects of amygdala processing can be most clearly distinguished at the level of single neurons.


Assuntos
Tonsila do Cerebelo/fisiologia , Emoções/fisiologia , Expressão Facial , Potenciais de Ação , Adolescente , Adulto , Tonsila do Cerebelo/citologia , Tonsila do Cerebelo/patologia , Estudos de Casos e Controles , Medo/fisiologia , Feminino , Felicidade , Humanos , Imagem por Ressonância Magnética/métodos , Masculino , Neurônios/fisiologia , Adulto Jovem
18.
J Neurosci Methods ; 282: 1-8, 2017 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-28238858

RESUMO

BACKGROUND: An automated process for sleep staging based on intracranial EEG data alone is needed to facilitate research into the neural processes occurring during slow wave sleep (SWS). Current manual methods for sleep scoring require a full polysomnography (PSG) set-up, including electrooculography (EOG), electromyography (EMG), and scalp electroencephalography (EEG). This set-up can be technically difficult to place in the presence of intracranial EEG electrodes. There is thus a need for a method for sleep staging based on intracranial recordings alone. NEW METHOD: Here we show a reliable automated method for the detection of periods of SWS solely based on intracranial EEG recordings. The method utilizes the ratio of spectral power in delta, theta, and spindle frequencies relative to alpha and beta frequencies to classify 30-s segments as SWS or not. RESULTS: We evaluated this new method by comparing its performance against visually scored patients (n=9), in which we also recorded EOG and EMG simultaneously. Our method had a mean positive predictive value of 64% across all nights. Also, an ROC analysis of the performance of our algorithm compared to manually labeled nights revealed a mean average area under the curve of 0.91 across all nights. COMPARISON WITH EXISTING METHOD: Our method had an average kappa score of 0.72 when compared to visual sleep scoring by an independent blinded sleep scorer. CONCLUSION: This shows that this simple method is capable of differentiating between SWS and non-SWS epochs reliably based solely on intracranial EEG recordings.


Assuntos
Algoritmos , Eletrocorticografia/métodos , Reconhecimento Automatizado de Padrão/métodos , Processamento de Sinais Assistido por Computador , Sono , Área Sob a Curva , Artefatos , Encéfalo/fisiopatologia , Ritmo Delta , Epilepsia/fisiopatologia , Humanos , Curva ROC , Convulsões/fisiopatologia , Sono/fisiologia , Ritmo Teta
19.
Nat Neurosci ; 20(4): 590-601, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28218914

RESUMO

Persistent neural activity is a putative mechanism for the maintenance of working memories. Persistent activity relies on the activity of a distributed network of areas, but the differential contribution of each area remains unclear. We recorded single neurons in the human medial frontal cortex and medial temporal lobe while subjects held up to three items in memory. We found persistently active neurons in both areas. Persistent activity of hippocampal and amygdala neurons was stimulus-specific, formed stable attractors and was predictive of memory content. Medial frontal cortex persistent activity, on the other hand, was modulated by memory load and task set but was not stimulus-specific. Trial-by-trial variability in persistent activity in both areas was related to memory strength, because it predicted the speed and accuracy by which stimuli were remembered. This work reveals, in humans, direct evidence for a distributed network of persistently active neurons supporting working memory maintenance.


Assuntos
Lobo Frontal/fisiologia , Memória de Curto Prazo/fisiologia , Neurônios/fisiologia , Lobo Temporal/fisiologia , Tonsila do Cerebelo/fisiologia , Giro do Cíngulo/fisiologia , Hipocampo/fisiologia , Humanos , Córtex Motor/fisiologia , Estimulação Luminosa
20.
Cell Rep ; 18(4): 878-891, 2017 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-28122239

RESUMO

Neurons in the primate amygdala respond prominently to faces. This implicates the amygdala in the processing of socially significant stimuli, yet its contribution to social perception remains poorly understood. We evaluated the representation of faces in the primate amygdala during naturalistic conditions by recording from both human and macaque amygdala neurons during free viewing of identical arrays of images with concurrent eye tracking. Neurons responded to faces only when they were fixated, suggesting that neuronal activity was gated by visual attention. Further experiments in humans utilizing covert attention confirmed this hypothesis. In both species, the majority of face-selective neurons preferred faces of conspecifics, a bias also seen behaviorally in first fixation preferences. Response latencies, relative to fixation onset, were shortest for conspecific-selective neurons and were ∼100 ms shorter in monkeys compared to humans. This argues that attention to faces gates amygdala responses, which in turn prioritize species-typical information for further processing.


Assuntos
Tonsila do Cerebelo/fisiologia , Macaca mulatta/fisiologia , Neurônios/fisiologia , Animais , Área Sob a Curva , Comportamento , Epilepsia/fisiopatologia , Humanos , Estimulação Luminosa , Curva ROC , Tempo de Reação/fisiologia
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