scholarly journals A theory of working memory without consciousness or sustained activity

2016 ◽  
Author(s):  
Darinka Trübutschek ◽  
Sébastien Marti ◽  
Andrés Ojeda ◽  
Jean-Rémi King ◽  
Yuanyuan Mi ◽  
...  
Keyword(s):  
Working Memory ◽  
Visual Masking ◽  
Target Location ◽  
Chance Level ◽  
Delayed Response ◽  
Conscious Perception ◽  
Neural Firing ◽  
Beta Band ◽  
Sustained Activity ◽  
Response Task

AbstractWorking memory and conscious perception are thought to share similar brain mechanisms, yet recent reports of non-conscious working memory challenge this view. Combining visual masking with magnetoencephalography, we demonstrate the reality of non-conscious working memory and dissect its neural mechanisms. In a spatial delayed-response task, participants reported the location of a subjectively unseen target above chance-level after a long delay. Conscious perception and conscious working memory were characterized by similar signatures: a sustained desynchronization in the alpha/beta band over frontal cortex, and a decodable representation of target location in posterior sensors. During non-conscious working memory, such activity vanished. Our findings contradict models that identify working memory with sustained neural firing, but are compatible with recent proposals of ‘activity-silent’ working memory. We present a theoretical framework and simulations showing how slowly decaying synaptic changes allow cell assemblies to go dormant during the delay, yet be retrieved above chance-level after several seconds.

scholarly journals A theory of working memory without consciousness or sustained activity

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Darinka Trübutschek ◽  
Sébastien Marti ◽  
Andrés Ojeda ◽  
Jean-Rémi King ◽  
Yuanyuan Mi ◽  
...  
Keyword(s):  
Working Memory ◽  
Visual Masking ◽  
Target Location ◽  
Chance Level ◽  
Delayed Response ◽  
Conscious Perception ◽  
Neural Firing ◽  
Beta Band ◽  
Sustained Activity ◽  
Response Task

Working memory and conscious perception are thought to share similar brain mechanisms, yet recent reports of non-conscious working memory challenge this view. Combining visual masking with magnetoencephalography, we investigate the reality of non-conscious working memory and dissect its neural mechanisms. In a spatial delayed-response task, participants reported the location of a subjectively unseen target above chance-level after several seconds. Conscious perception and conscious working memory were characterized by similar signatures: a sustained desynchronization in the alpha/beta band over frontal cortex, and a decodable representation of target location in posterior sensors. During non-conscious working memory, such activity vanished. Our findings contradict models that identify working memory with sustained neural firing, but are compatible with recent proposals of ‘activity-silent’ working memory. We present a theoretical framework and simulations showing how slowly decaying synaptic changes allow cell assemblies to go dormant during the delay, yet be retrieved above chance-level after several seconds.

scholarly journals Dissociative Effects of Methylphenidate in Nonhuman Primates: Trade-offs between Cognitive and Behavioral Performance

2012 ◽  
Vol 24 (6) ◽  
pp. 1371-1381 ◽  
Author(s):  
Abigail Z. Rajala ◽  
Jeffrey B. Henriques ◽  
Luis C. Populin
Keyword(s):  
Working Memory ◽  
Target Location ◽  
Memory Performance ◽  
Memory Task ◽  
Delayed Response ◽  
Impaired Performance ◽  
Healthy Humans ◽  
Trade Offs ◽  
Accuracy And Precision ◽  
Response Task

Low doses of methylphenidate reduce hyperactivity and improve attention in individuals with attention deficit hyperactivity disorder (ADHD) as well as in healthy humans and animals. Despite its extensive use, relatively little is known about its mechanisms of action. This study investigated the effects of methylphenidate on working memory performance, impulsivity, response accuracy and precision, and the ability to stay on task in rhesus monkeys using an oculomotor delayed response task. Methylphenidate affected task performance in an inverted-U manner in all three subjects tested. The improvements resulted from a reduction in premature responses and, importantly, not from improvement in the memory of target location. The length of time subjects participated in each session was also affected dose dependently. However, the dose at which the length of participation was maximally increased significantly impaired performance on the working memory task. This dissociation of effects has implications for the treatment of ADHD, for the nonprescription use of methylphenidate for cognitive enhancement, and for furthering the basic understanding of the neural substrate underlying these processes.

Attenuation of Delay-Period Activity of Monkey Prefrontal Neurons by an α2-Adrenergic Antagonist During an Oculomotor Delayed-Response Task

1998 ◽  
Vol 80 (4) ◽  
pp. 2200-2205 ◽  
Author(s):  
T. Sawaguchi
Keyword(s):  
Working Memory ◽  
Target Location ◽  
Spatial Working Memory ◽  
Delay Period ◽  
Delayed Response ◽  
Peripheral Cues ◽  
Adrenergic Antagonist ◽  
Neuronal Processes ◽  
Response Task ◽  
Delayed Response Task

Sawaguchi, T. Attenuation of delay-period activity of monkey prefrontal neurons by an α2-adrenergic antagonist during an oculomotor delayed-response task. J. Neurophysiol. 80: 2200–2205, 1998. To examine the role of norepinephrine receptors in spatial working memory processes mediated by the prefrontal cortex (PFC), noradrenergic antagonists (yohimbine for α2, prazosin for α1, and propranolol for β receptors) were applied iontophoretically to neurons of the dorsolateral PFC in rhesus monkeys that performed an oculomotor delayed-response (ODR) task. The ODR task was initiated when the monkeys fixated on a central spot on a computer monitor and consisted of fixation (1 s), cue (1 of 4 peripheral cues, 0.5 s), delay (fixation cue only, 4 s), and go periods. In the go period, the subject made a memory-guided saccade to the target location that was cued before the delay period. I focused on 49 neurons that showed directional delay-period activity, i.e., a sustained increase in activity during the delay period, the magnitude of which varied significantly with the memorized target location. Iontophoretic (usually 50 nA) application of yohimbine, but not prazosin or propranolol, significantly decreased the activities of most of the neurons with directional delay-period activity ( n = 41/49, 81%). Furthermore, yohimbine attenuated the sharpness of tuning, examined by a tuning index, of delay-period activity and had a greater attenuating effect on delay-period activity than on background activity. These findings suggest that the activation of α2-adrenergic receptors in the dorsolateral PFC plays a modulatory role in neuronal processes for visuospatial working memory.

Prefrontal Cortical Representation of Visuospatial Working Memory in Monkeys Examined by Local Inactivation With Muscimol

2001 ◽  
Vol 86 (4) ◽  
pp. 2041-2053 ◽  
Author(s):  
Toshiyuki Sawaguchi ◽  
Michiyo Iba
Keyword(s):  
Working Memory ◽  
Functional Organization ◽  
Visual Fields ◽  
Local Injection ◽  
Delayed Response ◽  
Visually Guided ◽  
Visuospatial Working Memory ◽  
Prefrontal Cortical ◽  
Response Task ◽  
Spatial Locations

In primates, dorsolateral areas of the prefrontal cortex (PFC) play a major role in visuospatial working memory. To examine the functional organization of the PFC for representing visuospatial working memory, we produced reversible local inactivation, with the local injection of muscimol (5 μg, 1 μl), at various sites ( n = 100) in the dorsolateral PFC of monkeys and observed the behavioral consequences in an oculomotor delayed-response task that required memory-guided saccades for locations throughout both visual fields. At 82 sites, the local injection of muscimol induced deficits in memory-guided saccades to a few specific, usually contralateral, target locations that varied with the location of the injection site. Such deficits depended on the delay length, and longer delays were associated with larger deficits in memory-guided saccades. The injection sites and affected spatial locations of the target showed a gross topographical relationship. No deficits appeared for a control task in which the subject was required to make a visually guided saccade to a visible target. These findings suggest that a specific site in the dorsolateral PFC is responsible for the working memory process for a specific visuospatial coordinate to guide goal-directed behavior. Further, memoranda for specific visuospatial coordinates appear to be represented in a topographical memory mapwithin the dorsolateral PFC to represent visuospatial working memory processes.

Spatial working memory assessment by a visual-manual delayed response task: a controlled study in schizophrenia

1999 ◽  
Vol 275 (1) ◽  
pp. 9-12 ◽  
Author(s):  
P Stratta ◽  
E Daneluzzo ◽  
P Prosperini ◽  
M Bustini ◽  
M.G Marinangeli ◽  
...  
Keyword(s):  
Working Memory ◽  
Spatial Working Memory ◽  
Controlled Study ◽  
Delayed Response ◽  
Memory Assessment ◽  
Response Task ◽  
Delayed Response Task

scholarly journals The lateral intraparietal area codes the location of saccade targets and not the dimension of the saccades that will be made to acquire them

2013 ◽  
Vol 109 (10) ◽  
pp. 2596-2605 ◽  
Author(s):  
Sara C. Steenrod ◽  
Matthew H. Phillips ◽  
Michael E. Goldberg
Keyword(s):  
Target Location ◽  
Rhesus Macaques ◽  
Oculomotor System ◽  
Saccade Target ◽  
Delayed Response ◽  
Lateral Intraparietal Area ◽  
Saccadic Adaptation ◽  
End Point ◽  
Priority Map ◽  
Response Task

Activity in the lateral intraparietal area (LIP) represents a priority map that can be used to direct attention and guide eye movements. However, it is not known whether this activity represents the location of saccade targets or the actual eye movement made to acquire them. We recorded single neurons from rhesus macaques ( Macaca mulatta) while they performed memory-guided delayed saccades to characterize the response profiles of LIP cells. We then separated the saccade target from the saccade end point by saccadic adaptation, a method that induces a change in the gain of the oculomotor system. We plotted LIP activity for all three epochs of the memory-guided delayed-response task (visual, delay period, and presaccadic responses) as a function of target location and saccade end point. We found that under saccadic adaptation the response profile for all three epochs was unchanged as a function of target location. We conclude that neurons in LIP reliably represent the locations of saccade targets, not the amplitude of the saccade required to acquire those targets. Although LIP transmits target information to the motor system, that information represents the location of the target and not the amplitude of the saccade that the monkey will make.

Self-Corrected Reaching in a Three-Location Delayed-Response Search Task

1998 ◽  
Vol 9 (1) ◽  
pp. 66-70 ◽  
Author(s):  
J. Steven Reznick ◽  
J. J. Fueser ◽  
Michelle Bosquet
Keyword(s):  
Working Memory ◽  
Spatial Orientation ◽  
Search Task ◽  
Chance Level ◽  
Delayed Response ◽  
Age Group ◽  
Cause Of Error ◽  
Better Than

Infants watched an experimenter hide a toy in one of three wells and then attempted to retrieve it after a brief delay. Seven-month-olds performed at chance. Nine-month-olds reached correctly on 43% of trials, which is significantly better than chance. After an incorrect reach, infants were allowed to choose between the two remaining locations. Seven-month-olds responded at a chance level on their second reach, but 9-month-olds chose correctly more often than would be expected by chance despite a 10- to 20-s delay between hiding and search. One cause of error on the initial reach was a profound bias toward the center well. In Experiment 2, the wells were covered simultaneously, and the infant's spatial orientation was disrupted during the delay; this procedure eliminated the centripetal bias. Nine-month-olds still responded correctly more often than would be expected by chance on their second reach. These findings suggest that 9-month-olds sometimes have a more durable working memory for location than is generally reported for that age group.

The role of D1-dopamine receptor in working memory: local injections of dopamine antagonists into the prefrontal cortex of rhesus monkeys performing an oculomotor delayed-response task

1994 ◽  
Vol 71 (2) ◽  
pp. 515-528 ◽  
Author(s):  
T. Sawaguchi ◽  
P. S. Goldman-Rakic
Keyword(s):  
Working Memory ◽  
Prefrontal Cortex ◽  
Injection Site ◽  
Target Location ◽  
Dopamine Antagonists ◽  
Dopamine Antagonist ◽  
Delayed Response ◽  
Intracerebral Injection ◽  
Control Task

1. To examine the role of dopamine receptors in the prefrontal cortex (PFC) on working memory, we injected dopamine antagonists (SCH23390, SCH39166, haloperidol, sulpiride, and raclopride) locally into the dorsolateral PFC in two monkeys trained to perform an oculomotor delayed-response (ODR) task. In the ODR task, monkeys fixate a central spot on a cathode ray tube (CRT) monitor while a visual cue is briefly (300 ms) presented in one of several peripheral locations in the visual field. After a delay of 1.5-6 s, the fixation spot is turned off, instructing the monkey to move its eyes to the target location that had been indicated by the visuospatial cue before the delay. Each monkey also performed a control task in which the cue remained on during the delay period. In this task the monkey's response was sensory rather than memory guided. 2. Local intracerebral injection of the selective dopamine antagonists SCH23390 (10-80 micrograms) and SCH39166 (1-5 micrograms) and/or the nonselective dopamine antagonist haloperidol (10-100 micrograms) induced deficits in ODR task performance at a total of 22 sites in the dorsolateral PFC. The deficit was characterized by a decrease in the accuracy of the memory-guided saccade as well as an increase in the latency of the response. The deficit usually appeared within 1-3 min after the injection, reached a peak at 20-40 min, and recovered at 60-90 min. 3. Performance change was restricted to a few specific target locations, which varied with the injection site and were most often contralateral to the injection site. 4. The degree of impairment in the ODR task occasioned by the injection of the dopamine antagonists was sensitive to the duration of delay; longer delays were associated with larger decreases in the accuracy and delayed onset of the memory-guided saccade. 5. The deficit was dose dependent; higher doses induced larger errors and increases in the onset of the memory-guided saccade. 6. Dopamine antagonists did not affect performance on the control task, which required the same eye movements but was sensory guided. Thus, in the same experimental session in which ODR performance was impaired, the accuracy and the latency of the sensory-guided saccades were normal for every target location.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Chemogenetic actuator drugs impair prefrontal cortex-dependent working memory in rhesus monkeys

2019 ◽  
Author(s):  
Nicholas A. Upright ◽  
Mark G. Baxter
Keyword(s):  
Working Memory ◽  
Prefrontal Cortex ◽  
Rhesus Monkeys ◽  
Memory Performance ◽  
Memory Function ◽  
Muscarinic Acetylcholine Receptor ◽  
Designer Drugs ◽  
Delayed Response ◽  
Response Task ◽  
Delayed Response Task

AbstractThe most common chemogenetic neuromodulatory system, Designer Receptors Exclusively Activated by Designer Drugs (DREADDs), uses a non-endogenous actuator ligand to activate a modified muscarinic acetylcholine receptor that is no longer sensitive to acetylcholine. It is crucial in studies using these systems to test the potential effects of DREADD actuators prior to any DREADD transduction, so that effects of DREADDs can be attributed to the chemogenetic system rather than the actuator drug. We investigated working memory performance after injections of three DREADD agonists, clozapine, olanzapine, and deschloroclozapine, in male rhesus monkeys tested in a spatial delayed response task. Performance at 0.1 mg/kg clozapine and 0.1 mg/kg deschloroclozapine did not differ from mean performance after vehicle in any of the four subjects. Administration of 0.2 mg/kg clozapine impaired working memory function in three of the four monkeys. Two monkeys were impaired after administration of 0.1 mg/kg olanzapine and two monkeys were impaired after the 0.3 mg/kg dose of deschloroclozapine. We speculate that the unique neuropharmacology of prefrontal cortex function makes the primate prefrontal cortex especially vulnerable to off-target effects of DREADD actuator drugs with affinity for endogenous monoaminergic receptor systems. These findings underscore the importance of within-subject controls for DREADD actuator drugs to confirm that effects following DREADD receptor transduction are not due to the actuator drug itself, as well as validating the behavioral pharmacology of DREADD actuator drugs in the specific tasks under study.Significance StatementChemogenetic technologies, such as Designer Receptors Exclusively Activated by Designer Drugs (DREADDs), allow for precise and remote manipulation of neuronal circuits. In the present study, we tested monkeys in a spatial delayed response task after injections of three actuator drugs – clozapine, olanzapine, and deschloroclozapine. We found that monkeys showed significant working memory impairments after 0.2 mg/kg clozapine, 0.1 mg/kg olanzapine, and 0.3 mg/kg deschloroclozapine compared to vehicle performance. In monkeys that showed impairments, these deficits were particularly apparent at longer delay periods. It is imperative to validate the drugs and dosages in the particular behavioral test to ensure any behavior after DREADD transduction can be attributed to activation of the receptors and not administration of the actuator drug itself.

Transition of target-location signaling in activity of macaque lateral intraparietal neurons during delayed-response visual search

2014 ◽  
Vol 112 (6) ◽  
pp. 1516-1527 ◽  
Author(s):  
Satoshi Nishida ◽  
Tomohiro Tanaka ◽  
Tadashi Ogawa
Keyword(s):  
Working Memory ◽  
Visual Search ◽  
Cognitive Processes ◽  
Visual Discrimination ◽  
Target Location ◽  
Real Life ◽  
Neural Representation ◽  
Delayed Response ◽  
Response Modulation ◽  
Stimulus Offset

Neurons in the lateral intraparietal area (LIP) are involved in signaling the location of behaviorally relevant objects during visual discrimination and working memory maintenance. Although previous studies have examined these cognitive processes separately, they often appear as inseparable sequential processes in real-life situations. Little is known about how the neural representation of the target location is altered when both cognitive processes are continuously required for executing a task. We investigated this issue by recording single-unit activity from LIP of monkeys performing a delayed-response visual search task in which they were required to discriminate the target from distractors in the stimulus period, remember the location at which the extinguished target had been presented in the delay period, and make a saccade to that location in the response period. Target-location signaling was assessed using response modulations contingent on whether the target location was inside or opposite the receptive field. Although the population-averaged response modulation was consistent and changed only slightly during a trial, the across-neuron pattern of response modulations showed a marked and abrupt change around 170 ms after stimulus offset due to concurrent changes in the response modulations of a subset of LIP neurons, which manifested heterogeneous patterns of activity changes during the task. Our findings suggest that target-location signaling by the across-neuron pattern of LIP activity discretely changes after the stimulus disappearance under conditions that continuously require visual discrimination and working memory to perform a single behavioral task.

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