Role of dopamine neurons in familiarity.

Dopamine neurons signal the salience of environmental stimuli and influence learning, although it is less clear if these neurons also determine the salience of memories. Ventral tegmental area (VTA) dopamine neurons increase their firing in the presence of new objects and reduce it upon repeated, inconsequential exposures, marking the shift from novelty to familiarity. This study investigates how dopamine neuron activity during repeated familiar object exposure affects an animal's preference for new objects in a subsequent novel object recognition (NOR) test. We hypothesize that a single familiarization session will not sufficiently lower dopamine activity, such that the memory of a familiar object remains salient, leading to equal exploration of familiar and novel objects and weaker NOR discrimination. In contrast, multiple familiarization sessions likely suppress dopamine activity more effectively, reducing the salience of the familiar object and enhancing subsequent novelty discrimination. Our experiments in mice indicated that multiple familiarization sessions reduce VTA dopamine neuron activation, as measured by c-Fos expression, and enhance novelty discrimination compared with a single familiarization session. Dopamine neurons that show responsiveness to novelty were primarily located in the paranigral nucleus of the VTA and expressed vesicular glutamate transporter 2 transcripts, marking them as dopamine-glutamate neurons. Chemogenetic inhibition of dopamine neurons during a single session paralleled the effects of multiple sessions, improving NOR. These findings suggest that a critical role of dopamine neurons during the transition from novelty to familiarity is to modulate the salience of an object's memory.

Identification of Early Hippocampal Dynamics during Recognition Memory with Independent Component Analysis.

The hippocampus is generally considered to have relatively late involvement in recognition memory, its main electrophysiological signature being between 400 and 800 ms after stimulus onset. However, most electrophysiological studies have analyzed the hippocampus as a single responsive area, selecting only a single-site signal exhibiting the strongest effect in terms of amplitude. These classical approaches may not capture all the dynamics of this structure, hindering the contribution of other hippocampal sources that are not located in the vicinity of the selected site. We combined intracerebral electroencephalogram recordings from epileptic patients with independent component analysis during a recognition memory task involving the recognition of old and new images. We identified two sources with different responses emerging from the hippocampus: a fast one (maximal amplitude at ∼250 ms) that could not be directly identified from raw recordings and a latter one, peaking at ∼400 ms. The former component presented different amplitudes between old and new items in 6 out of 10 patients. The latter component had different delays for each condition, with a faster activation (∼290 ms after stimulus onset) for recognized items. We hypothesize that both sources represent two steps of hippocampal recognition memory, the faster reflecting the input from other structures and the latter the hippocampal internal processing. Recognized images evoking early activations would facilitate neural computation in the hippocampus, accelerating memory retrieval of complementary information. Overall, our results suggest that the hippocampal activity is composed of several sources with an early activation related to recognition memory.

Effects of lexical skills and orthographic neighborhood size in word memory.

Two experiments were designed to investigate the relationship between individual lexical skills in young adults and memory performance on words varying by their orthographic neighborhood size. In Experiment 1, a sample of 100 university students were administrated a set of spelling, reading, and vocabulary tests to assess their lexical skills. Then, they had to learn mixed lists of words from high and low neighborhood size and perform free recall and memory recognition tasks. Importantly, high lexical skills were found to enhance free recall and, to a lesser extent, recognition. In addition, a typical mirror effect of neighborhood size was found in recognition as words were better recognized and also produced less false alarms when they had a low neighborhood size. In Experiment 2, pure lists of words were designed and a new sample of 90 university students was assessed. We replicated the effect of lexical skills in free recall and the effect of neighborhood size for hits in recognition. Spelling skills were found to interact with neighborhood size in free recall in that low spelling skills were associated with a facilitatory effect of neighborhood size. In recognition, a relation between reading skills and neighborhood size was found such that the higher the reading skills, the higher was the inhibitory effect of neighborhood size. These results provide new evidence of an influence of lexical skills in word memory performance and underline the role of orthographic neighborhood size in episodic memory tasks.

fMRI evidence of movement familiarization effects on recognition memory in professional dancers.

Dual-process theories propose that recognition memory involves recollection and familiarity; however, the impact of motor expertise on memory recognition, especially the interplay between familiarity and recollection, is relatively unexplored. This functional magnetic resonance imaging study used videos of a dancer performing International Latin Dance Styles as stimuli to investigate memory recognition in professional dancers and matched controls. Participants observed and then reported whether they recognized dance actions, recording the level of confidence in their recollections, whereas blood-oxygen-level-dependent signals measured encoding and recognition processes. Professional dancers showed higher accuracy and hit rates for high-confidence judgments, whereas matched controls exhibited the opposite trend for low-confidence judgments. The right putamen and precentral gyrus showed group-based moderation effects, especially for high-confidence (vs. low-confidence) action recognition in professional dancers. During action recognition, the right superior temporal gyrus and insula showed increased activation for accurate recognition and high-confidence retrieval, particularly in matched controls. These findings highlighting enhanced action memory of professional dancers-evident in their heightened recognition confidence-not only supports the dual-processing model but also underscores the crucial role of expertise-driven familiarity in bolstering successful recollection. Additionally, they emphasize the involvement of the action observation network and frontal brain regions in facilitating detailed encoding linked to intention processing.

Role of Dopamine Neurons in Familiarity.

Dopamine neurons signal the salience of environmental stimuli, influencing learning and motivation. However, research has not yet identified whether dopamine neurons also modulate the salience of memory content. Dopamine neuron activity in the ventral tegmental area (VTA) increases in response to novel objects and diminishes as objects become familiar through repeated presentations. We proposed that the declined rate of dopamine neuron activity during familiarization affects the salience of a familiar object's memory. This, in turn, influences the degree to which an animal distinguishes between familiar and novel objects in a subsequent novel object recognition (NOR) test. As such, a single familiarization session may not sufficiently reduce dopamine activity, allowing the memory of a familiar object to maintain its salience and potentially attenuating NOR. In contrast, multiple familiarization sessions could lead to more pronounced dopamine activity suppression, strengthening NOR. Our data in mice reveals that, compared to a single session, multiple sessions result in decreased VTA dopamine neuron activation, as indicated by c-Fos measurements, and enhanced novelty discrimination. Critically, when VTA dopamine neurons are chemogenetically inhibited during a single familiarization session, NOR improves, mirroring the effects of multiple familiarization sessions. In summary, our findings highlight the pivotal function of dopamine neurons in familiarity and suggest a role in modulating the salience of memory content.

Examining levels of processing using verbal & pictorial stimuli with the complex trial protocol in a mock theft scenario.

The Complex Trial Protocol (CTP) is an EEG-based Concealed Information Test (CIT). Depth of processing influences memorability where deeper processing increases recollection. The CTP's performance as a function of shallow versus deep levels of processing has not been explored. Two experiments were conducted, one with verbal stimuli and the other with their pictorial referents. In both experiments, participants were randomly assigned to three groups, Innocent Control (Control) condition, Guilty Immediate Shallow Processing (Shallow) condition, and Guilty Immediate Deep Processing (Deep) condition. Shallow and Deep participants from both experiments underwent the same mock theft scenario and all three groups were later exposed to either a verbal (N = 41) or pictorial (N = 43) stimulus on a computer monitor. In the word study, no differences in CIT effect were found between any of the groups. Areas under the curve (AUCs) did not differ from chance (.624 and .679 for Shallow and Deep groups respectively). In the image study, the CIT effect for the Shallow and Deep groups differed from the Control one. The AUCs (.755 and .943 for the Shallow and Deep groups respectively) differed significantly from each other. Levels of Processing (LOP) did not appear to have any bearing on CTP performance when words were used as probes but did have an effect when images were used. The findings may hint at some of the limitations of the CTP and fail to replicate similar experiments, especially when words are used as probes, from the late Peter Rosenfeld's laboratory.

Brain recognition of previously learned versus novel temporal sequences: a differential simultaneous processing.

Memory for sequences is a central topic in neuroscience, and decades of studies have investigated the neural mechanisms underlying the coding of a wide array of sequences extended over time. Yet, little is known on the brain mechanisms underlying the recognition of previously memorized versus novel temporal sequences. Moreover, the differential brain processing of single items in an auditory temporal sequence compared to the whole superordinate sequence is not fully understood. In this magnetoencephalography (MEG) study, the items of the temporal sequence were independently linked to local and rapid (2-8 Hz) brain processing, while the whole sequence was associated with concurrent global and slower (0.1-1 Hz) processing involving a widespread network of sequentially active brain regions. Notably, the recognition of previously memorized temporal sequences was associated to stronger activity in the slow brain processing, while the novel sequences required a greater involvement of the faster brain processing. Overall, the results expand on well-known information flow from lower- to higher order brain regions. In fact, they reveal the differential involvement of slow and faster whole brain processing to recognize previously learned versus novel temporal information.

Remembering a Virtual Museum Tour: Viewing Time, Memory Reactivation, and Memory Distortion.

A variety of evidence demonstrates that memory is a reconstructive process prone to errors and distortions. However, the complex relationship between memory encoding, strength of memory reactivation, and the likelihood of reporting true or false memories has yet to be ascertained. We address this issue in a setting that mimics a real-life experience: We asked participants to take a virtual museum tour in which they freely explored artworks included in the exhibit, while we measured the participants' spontaneous viewing time of each explored artwork. In a following memory reactivation phase, participants were presented again with explored artworks (reactivated targets), followed by novel artworks not belonging to the same exhibit (activated lures). For each of these objects, participants provided a reliving rating that indexed the strength of memory reactivation. In the final memory recognition phase, participants underwent an old/new memory task, involving reactivated vs. baseline (i.e., non-reactivated) targets, and activated and baseline lures. The results showed that those targets that were spontaneously viewed for a longer amount of time were more frequently correctly recognized. This pattern was particularly true for reactivated targets associated with greater memory strength (a higher reliving rating). Paradoxically, however, lures that were presented after targets associated with higher reliving ratings in the reactivation phase were more often erroneously recognized as artworks encountered during the tour. This latter finding indicates that memory intrusions, irrespective of the viewing time, are more likely to take place and be incorporated into true memories when the strength of target memory is higher.

Effect of intermittent isometric handgrip exercise protocol with short exercise duration on cognitive performance.

The handgrip exercise, a small muscle exercise, is useful for exercise therapy, particularly in the elderly and bedridden patients. The isometric handgrip (IHG) exercise has been utilized in training programs to reduce resting blood pressure; however, the acute effects of the IHG exercise on cognitive performance are not fully understood. The present study aimed to investigate the effect of an intermittent IHG exercise protocol with short exercise duration, which minimizes the arterial blood pressure response to exercise, on cognitive performance. Twenty-two young healthy subjects performed the intermittent IHG exercise protocol, which consisted of 30-s IHG and 45-s recovery × 16 trials; the exercise intensity of the IHG exercise was 30% of the maximal voluntary contraction. Cognitive performance was evaluated before and after the exercise with the Go/No-Go and memory recognition tasks. Specifically, the reaction time (RT) and performance accuracy were measured. The intermittent IHG exercise protocol did not change the RT or performance accuracy of either the Go/No-Go task (P = 0.222 and P = 0.260, respectively) or the memory recognition task (P = 0.427 and P = 0.245, respectively). These findings suggest that the intermittent IHG exercise protocol with short exercise duration may not provide enough stimulation to improve cognitive performance despite being useful as a safe exercise therapy in the elderly and in patients with cardiovascular disease.

An Independent Validation of the EEG-Based Complex Trial Protocol with Autobiographical Data and Corroboration of its Resistance to a Cognitively Charged Countermeasure.

The Complex Trial Protocol (CTP) is a P300-based Concealed Information Test (CIT). The theoretical underpinnings of the CIT in the context of law enforcement usage are sound. The CTP is said to effectively discriminate individuals who recognize novel and meaningful stimuli and to be countermeasure resistant. Forty-five undergraduate students were assigned to three groups and instructed to perform a computer task using autobiographical data in connection to a mock burglary script. P300 peak-to-peak amplitude differences between probe (surname) and irrelevant (patronymic foils) items accurately identified 100% (14/14) of Innocent Controls (IC), 94% (15/16) of Simply Guilty (SG) participants, and 93% (14/15) of Guilty Countermeasure (GCM) subjects who were asked to counter all stimuli by mentally counting backwards continuously during their test presentation. Increased number of mistakes during the test, from combined cognitive erroneous responses to pop quizzes and behavioral errors with button presses, significantly discriminated GCM from IC and SG individuals. GCM participants committed more errors than IC and SG which did not differ from one another. Reaction Time (RT) was only significant between GCM and IC groups. Implications for forensic issues are discussed.

Effects of acute interval handgrip exercise on cognitive performance.

Previous studies have reported that even a single bout of dynamic exercise improves cognitive performance. However, the acute effect of the interval handgrip (HG) exercise protocol, which is effective in reducing resting blood pressure, on cognitive performance is poorly understood. Cognitive performance was assessed in 17 young healthy subjects before and after a resting control (e.g., time control) and the interval HG exercise (Exercise), which consisted of four trials of 2-min HG exercise at 25% of maximum voluntary contraction with 3-min recovery in between each trial. Mean arterial blood pressure (MAP) and middle cerebral artery blood velocity (MCA V) were measured continuously throughout the experiment. Memory recognition and executive function were assessed using memory recognition and Go/No-Go tasks, respectively. During interval HG exercise, MAP and mean MCA V increased from the resting baseline condition (both P < 0.049) and returned to the resting baseline levels during recovery after the interval HG exercise (both P = 1.000). The reaction time and performance accuracy of the memory recognition task did not change in either the time control condition or Exercise condition (P = 0.514 and P = 0.414 respectively). However, the changes in reaction time of Go/No-Go task from the baseline in Exercise condition was significantly shorter than that in time-control condition (P = 0.004) without affecting performance accuracy (P = 0.482). The results of the present study show that an acute interval HG exercise could improve the processing speed in executive function despite no post-exercise improvement in hemodynamic parameters in young healthy subjects. These findings suggest that the interval HG exercise is a useful exercise mode that can be expected to have a positive effect on the processing speed in executive function regardless of cardiovascular adaptation to exercise.

Cognitive processing characteristics of depression in emotional Stroop and memory recognition / 中华行为医学与脑科学杂志

Objective:To explore the cognitive processing characteristics of semantic emotion Stroop and memory recognition in pilots with depression, and to systematically reveal the cognitive processing characteristics of attention and memory.Methods:The semantic emotional Stroop task and memory recognition test were performed in 36 depressed pilots and 36 healthy pilots.The results of attention and memory in cognitive processing were analyzed by repeated measurement analysis of variance using SPSS 18.0 software.Results:In the semantic emotion Stroop, the response time of the depression group was longer than that of the control group ( F(1, 70)=7.03, P=0.008), and the response time of the depression group(579.55±141.62)ms ) was longer than that of the neutral words (565.66±132.60)ms, P=0.003) and positive words (563.09±138.88)ms, P<0.01). In memory recognition, the accuracy of response to emotion words in the depressed group was higher than that in the control group ( F(1, 70)=23.15, P<0.01). The accuracy of response to negative words was higher in the depressed group than that to positive words ((0.50±0.32) vs (0.32±0.21), P=0.006) and neutral words ((0.50±0.32) vs (0.33±0.23), P=0.007). The depression group showed a conservative bias towards negative words ((1.46±0.40), P<0.01), and negative words compared with neutral words ((0.63±0.24), P<0.01) and positive words ((0.57±0.27), P<0.01) were cautious and conservative. Conclusion:Patients with depression have attention bias toward the negative information in semantic information processing, and negative memory bias in memory recognition.

How Does Gender Stereotype Affect the Memory of Advertisements? A Behavioral and Electroencephalography Study.

Previous studies have shown equivocal results about whether atypical or unusual events, compared with typical ones, facilitate or inhibit memory. We suspect that the indefinite findings could be partly due to the recall task used in these studies, as the participants might have used inference instead of recall in their responses. In the present study, we tested the recognition memory for real (Experiment 1) and fabricated (Experiment 2) advertisements, which could be congruent or incongruent with gender stereotypes. In congruent advertisements, a female endorser presented a traditionally considered feminine product or a male endorser presented a traditionally considered masculine product, whereas the gender-product type matching reversed in incongruent advertisements. The results of both behavioral experiments revealed that the participants' memory performance for stereotype-incongruent advertisements was higher than for congruent ones. In the event-related potential (ERP) recordings in Experiment 3, larger positive amplitudes were found for stereotype-incongruent advertisements than for congruent advertisements on the left parietal sites, suggesting a deeper encoding process for stereotype-incongruent information than for stereotype-congruent information.

The effect of threatening facial expressions on inhibition-induced forgetting depends on their task-relevance.

Inhibition-induced forgetting refers to impaired memory for the stimuli to which responses were inhibited. The present study aimed to examine if it would be modulated by the processing of threatening facial expressions. Angry and neutral faces were presented in a go/no-go task and subsequent memory for faces was measured in a surprise recognition task. In Experiment 1, task-irrelevant angry and neutral faces appeared randomly, and participants responded to the gender of the faces during the go/no-go task. Results showed that the perception of neutral faces was possibly biased by angry faces. So, in Experiment 2, angry and neutral faces were given in separate blocks while participants still responded to the gender. Inhibition-induced forgetting was not modulated by facial expressions, as it was observed for both angry and neutral faces. Finally, in Experiment 3, where participants were assigned to respond to either angry or neutral faces, so that facial expressions were relevant, inhibition-induced forgetting was negated only in the group in whom responses to angry faces were inhibited. The findings suggest that task-relevance plays a key role in the way the processing of emotional information influences the interaction between cognitive control and memory encoding.

Effect of acute eye fatigue on cognition for young females: a pilot study.

The number of people suffering from eye fatigue induced by visual display terminal (VDT) viewing is expected to increase in the modern world. Eye dysfunction is suggested to induce a decrease in cognitive function, at least in the long term. Furthermore, considering other previous findings, it may be reasonable to think that acute or relatively short-term eye dysfunction attenuates cognitive function for not only older but also young individuals. Hence, clarification of the effect of eye fatigue induced by VDT viewing on cognitive performance is essential in order to maintain and/or improve our quality of life in the modern world regardless of age. The present study investigated the effect of eye fatigue induced by 1-h VDT viewing on cognitive performance, to test the hypothesis that such eye fatigue impairs cognitive performance in young individuals. A total of 19 healthy female university students voluntarily participated in this study. Before and after the 1-h VDT viewing or resting, the degree of eye fatigue and cognitive performance were evaluated. Refractive error measurement was performed to assess the degree of eye fatigue using a binocular auto refractometer, and a memory recognition task and Go/NoGo task were used to estimate cognitive performance. Response accuracy and reaction time were evaluated in the two tasks. Due to difficulty in interpreting the data of refractive error for one participant from the perspective of eye fatigue, the data for 18 participants were used for further analysis. The refractive error was significantly lower after than before the VDT viewing, but a corresponding change was not found before and after resting. Regarding cognitive performance, only the reaction time in the memory recognition task varied with the VDT viewing or resting. The reaction time was significantly longer after than before resting, without a corresponding difference before and after the VDT viewing. Thus, the 1-h VDT viewing induced eye fatigue, but relatively improved rather than attenuated reaction time in the memory recognition task. These results suggest that the effect of the increase in arousal level induced by the present VDT viewing on memory recognition compensated for the negative effect of 1-h resting of the eyes. We conclude that the acute eye fatigue induced by the 1-h VDT viewing does not have detrimental effects on cognition in young females at least under the present conditions.

Cross-talk between guanidinoacetate neurotoxicity, memory and possible neuroprotective role of creatine.

Guanidinoacetate Methyltransferase deficiency is an inborn error of metabolism that results in decreased creatine and increased guanidinoacetate (GAA) levels. Patients present neurological symptoms whose mechanisms are unclear. We investigated the effects of an intrastriatal administration of 10 µM of GAA (0.02 nmol/striatum) on energy metabolism, redox state, inflammation, glutamate homeostasis, and activities/immunocontents of acetylcholinesterase and Na+,K+-ATPase, as well as on memory acquisition. The neuroprotective role of creatine was also investigated. Male Wistar rats were pretreated with creatine (50 mg/kg) or saline for 7 days underwenting stereotactic surgery. Forty-eight hours after surgery, the animals (then sixty-days-old) were divided into groups: Control, GAA, GAA + Creatine, and Creatine. Experiments were performed 30 min after intrastriatal infusion. GAA decreased SDH, complexes II and IV activities, and ATP levels, but had no effect on mitochondrial mass/membrane potential. Creatine totally prevented SDH and complex II, and partially prevented COX and ATP alterations. GAA increased dichlorofluorescein levels and decreased superoxide dismutase and catalase activities. Creatine only prevented catalase and dichlorofluorescein alterations. GAA increased cytokines, nitrites levels and acetylcholinesterase activity, but not its immunocontent. Creatine prevented such effects, except nitrite levels. GAA decreased glutamate uptake, but had no effect on the immunocontent of its transporters. GAA decreased Na+,K+-ATPase activity and increased the immunocontent of its α3 subunit. The performance on the novel object recognition task was also impaired. Creatine partially prevented the changes in glutamate uptake and Na+,K+-ATPase activity, and completely prevented the memory impairment. This study helps to elucidate the protective effects of creatine against the damage caused by GAA.

On the effects of regional accents on memory and credibility.

The information we obtain from how speakers sound-for example their accent-affects how we interpret the messages they convey. A clear example is foreign accented speech, where reduced intelligibility and speaker's social categorization (out-group member) affect memory and the credibility of the message (e.g., less trustworthiness). In the present study, we go one step further and ask whether evaluations of messages are also affected by regional accents-accents from a different region than the listener. In the current study, we report results from three experiments on immediate memory recognition and immediate credibility assessments as well as the illusory truth effect. These revealed no differences between messages conveyed in local-from the same region as the participant-and regional accents-from native speakers of a different country than the participants. Our results suggest that when the accent of a speaker has high intelligibility, social categorization by accent does not seem to negatively affect how we treat the speakers' messages.

Estimation of effective connectivity using multi-layer perceptron artificial neural network.

Studies on interactions between brain regions estimate effective connectivity, (usually) based on the causality inferences made on the basis of temporal precedence. In this study, the causal relationship is modeled by a multi-layer perceptron feed-forward artificial neural network, because of the ANN's ability to generate appropriate input-output mapping and to learn from training examples without the need of detailed knowledge of the underlying system. At any time instant, the past samples of data are placed in the network input, and the subsequent values are predicted at its output. To estimate the strength of interactions, the measure of "Causality coefficient" is defined based on the network structure, the connecting weights and the parameters of hidden layer activation function. Simulation analysis demonstrates that the method, called "CREANN" (Causal Relationship Estimation by Artificial Neural Network), can estimate time-invariant and time-varying effective connectivity in terms of MVAR coefficients. The method shows robustness with respect to noise level of data. Furthermore, the estimations are not significantly influenced by the model order (considered time-lag), and the different initial conditions (initial random weights and parameters of the network). CREANN is also applied to EEG data collected during a memory recognition task. The results implicate that it can show changes in the information flow between brain regions, involving in the episodic memory retrieval process. These convincing results emphasize that CREANN can be used as an appropriate method to estimate the causal relationship among brain signals.

Sensorimotor Learning Enhances Expectations During Auditory Perception.

Sounds that have been produced with one's own motor system tend to be remembered better than sounds that have only been perceived, suggesting a role of motor information in memory for auditory stimuli. To address potential contributions of the motor network to the recognition of previously produced sounds, we used event-related potential, electric current density, and behavioral measures to investigate memory for produced and perceived melodies. Musicians performed or listened to novel melodies, and then heard the melodies either in their original version or with single pitch alterations. Production learning enhanced subsequent recognition accuracy and increased amplitudes of N200, P300, and N400 responses to pitch alterations. Premotor and supplementary motor regions showed greater current density during the initial detection of alterations in previously produced melodies than in previously perceived melodies, associated with the N200. Primary motor cortex was more strongly engaged by alterations in previously produced melodies within the P300 and N400 timeframes. Motor memory traces may therefore interface with auditory pitch percepts in premotor regions as early as 200 ms following perceived pitch onsets. Outcomes suggest that auditory-motor interactions contribute to memory benefits conferred by production experience, and support a role of motor prediction mechanisms in the production effect.