Attention improves memory by suppressing spiking-neuron activity in the human anterior temporal lobe

The role of the parahippocampal cortex in memory consolidation for scenes

Classic models propose that forming lasting visual memories involves coordinated interactions between visually selective neocortical structures and the hippocampus during memory consolidation. However, the precise role of visually selective neocortical structures in memory consolidation remains elusive, given their potential contributions spanning from initial perceptual encoding to subsequent memory reactivation. We capitalized on a unique opportunity, involving direct recording from the posterior parahippocampus and its subsequent resection in a neurological patient, to investigate the impact of scene-selective neocortical lesions on visual memory consolidation. First, with intracranial EEG, we confirmed the functional relevance of the patient's resected tissues in representing a specific visual category, in this case, scene images. Subsequently, we identified disruption of memory for scenes relative to faces and objects during the participant's postoperative visit. This finding prompted a comprehensive analysis of visual memory across different visual categories in this participant, as well as an examination of similar functions in other neurological patients with intact parahippocampi and a cohort of online participants. Through these within- and between-participant comparisons, we identified greater time-dependent reduction in visual memory for scene images following the resection of the posterior parahippocampus. Importantly, these changes in memory retention could not be attributed to a general reduction in initial memory encoding following neocortical lesions. Our findings, therefore, suggest that reactivating scene-selective neocortical areas is essential for converting transient visual perceptual experiences into lasting long-term scene memories.

Attention to memory content enhances single-unit spike sequence fidelity in the human anterior temporal lobe

Attention aids in prioritizing information relevant to our present goals. For example, attention may augment sensory processing by modulating neural activity for low-level features of the attended items. Attention can also prioritize the contents of memory, facilitating our ability to remember some pieces of information while ignoring others. Here, we examine how using attention to modulate the contents of memory affects temporally organized sequences of neuronal spiking in the human anterior temporal lobe. These spike sequences represent higher-level semantic information and occur repeatedly and consistently as participants process and encode words into memory. Our results demonstrate that attention deployed to prioritize words for memory increases the consistency of these spike sequences. Further, retroactively cueing words elicits the replay of these sequences. Our data, therefore, suggest that paying attention to prioritizing semantic content for memory may improve the temporal organization of neural spiking representations of semantic information in the anterior temporal lobe.

Neural Correlates of Category Learning in Monkey Inferior Temporal Cortex

Area TE is required for normal learning of visual categories based on perceptual similarity. To evaluate whether category learning changes neural activity in area TE, we trained two monkeys (both male) implanted with multielectrode arrays to categorize natural images of cats and dogs. Neural activity during a passive viewing task was compared pre- and post-training. After the category training, the accuracy of abstract category decoding improved. Single units became more category selective, the proportion of single units with category selectivity increased, and units sustained their category-specific responses for longer. Visual category learning thus appears to enhance category separability in area TE by driving changes in the stimulus selectivity of individual neurons and by recruiting more units to the active network.

Psychometric properties of the Arabic version of the everyday memory questionnaire - revised (EMQ-R) among the Lebanese population

Objective: This study aimed to evaluate the psychometric properties of the Arabic version of the Everyday Memory Questionnaire- Revised (EMQ-R-A) in a sample of Lebanese adults. Methods: A cross-sectional study was conducted in August 2023. A diverse sample of 483 Lebanese adults aged 18 to 60 years from all Lebanese governorates was recruited. Participants completed an Arabic-language questionnaire comprising three sections: socio-demographic characteristics, health-related inquiries, the EMQ-R-A and the Arabic version of the Prospective and Retrospective Memory Questionnaire (PRMQ). Results: The study's findings indicated that the EMQ-R-A displayed strong internal consistency (Cronbach's alpha = 0.925). Convergent validity was supported by a significant correlation with PRMQ. Test-retest results demonstrated strong reliability with a Cronbach's alpha of 0.925. Confirmatory factor analysis revealed a three-factor model including retrieval related factors, attentional tracking related factors, and other factors. The factors labeled "Retrieval" and "Attentional Tracking" elucidate aspects of memory retrieval system efficacy and attention-related challenges. Higher EMQ-R-A scores were found to be associated with the female gender, lower attention, physical inactivity, lower educational levels, and higher number of comorbid disorders. Conclusion: The EMQ-R-A exhibits good validity and reliability. The identified factors associated with memory decline underscore the importance of addressing lifestyle factors, such as promoting physical activity, better educational attainment, and addressing comorbid health conditions, to potentially mitigate memory challenges.

Neuronal sequences in population bursts encode information in human cortex

Neural coding has traditionally been examined through changes in firing rates and latencies in response to different stimuli1-5. However, populations of neurons can also exhibit transient bursts of spiking activity, wherein neurons fire in a specific temporal order or sequence6-8. The human brain may utilize these neuronal sequences within population bursts to efficiently represent information9-12, thereby complementing the well-known neural code based on spike rate or latency. Here we examined this possibility by recording the spiking activity of populations of single units in the human anterior temporal lobe as eight participants performed a visual categorization task. We find that population spiking activity organizes into bursts during the task. The temporal order of spiking across the activated units within each burst varies across stimulus categories, creating unique stereotypical sequences for individual categories as well as for individual exemplars within a category. The information conveyed by the temporal order of spiking activity is separable from and complements the information conveyed by the units' spike rates or latencies following stimulus onset. Collectively, our data provide evidence that the human brain contains a complementary code based on the neuronal sequence within bursts of population spiking to represent information.

Toward a mechanistic understanding of the role of error monitoring and memory in social anxiety

Cognitive models state that social anxiety (SA) involves biased cognitive processing that impacts what is learned and remembered within social situations, leading to the maintenance of SA. Neuroscience work links SA to enhanced error monitoring, reflected in error-related neural responses arising from mediofrontal cortex (MFC). Yet, the role of error monitoring in SA remains unclear, as it is unknown whether error monitoring can drive changes in memory, biasing what is learned or remembered about social situations. Motivated by the longer-term goal of identifying mechanisms implicated in SA, in the current study we developed and validated a novel paradigm for probing the role of error-related MFC theta oscillations (associated with error monitoring) and incidental memory biases in SA. Electroencephalography (EEG) data were collected while participants completed a novel Face-Flanker task, involving presentation of task-unrelated, trial-unique faces behind target/flanker arrows on each trial. A subsequent incidental memory assessment evaluated memory biases for error events. Severity of SA symptoms were associated with greater error-related theta synchrony over MFC, as well as between MFC and sensory cortex. Social anxiety also was positively associated with incidental memory biases for error events. Moreover, greater error-related MFC-sensory theta synchrony during the Face-Flanker predicted subsequent incidental memory biases for error events. Collectively, the results demonstrate the potential of a novel paradigm to elucidate mechanisms underlying relations between error monitoring and SA.

We know what attention is!

Attention is one of the most thoroughly investigated psychological phenomena, yet skepticism about attention is widespread: we do not know what it is, it is too many things, there is no such thing. The deficiencies highlighted are not about experimental work but the adequacy of the scientific theory of attention. Combining common scientific claims about attention into a single theory leads to internal inconsistency. This paper demonstrates that a specific functional conception of attention is incorporated into the tasks used in standard experimental paradigms. In accepting these paradigms as valid probes of attention, we commit to this common conception. The conception unifies work at multiple levels of analysis into a coherent scientific explanation of attention. Thus, we all know what attention is.

Neural correlates of category learning in monkey inferior temporal cortex

We trained two monkeys implanted with multi-electrode arrays to categorize natural images of cats and dogs, in order to observe changes in neural activity related to category learning. We recorded neural activity from area TE, which is required for normal learning of visual categories based on perceptual similarity. Neural activity during a passive viewing task was compared pre- and post-training. After the category training, the accuracy of abstract category decoding improved. Specifically, the proportion of single units with category selectivity increased, and units sustained their category-specific responses for longer. Visual category learning thus appears to enhance category separability in area TE by driving changes in the stimulus selectivity of individual neurons and by recruiting more units to the active network.

Towards a mechanistic understanding of the role of error monitoring and memory in social anxiety

Cognitive models state social anxiety (SA) involves biased cognitive processing that impacts what is learned and remembered within social situations, leading to the maintenance of SA. Neuroscience work links SA to enhanced error monitoring, reflected in error-related neural responses arising from mediofrontal cortex (MFC). Yet, the role of error monitoring in SA remains unclear, as it is unknown whether error monitoring can drive changes in memory, biasing what is learned or remembered about social situations. Thus, we developed a novel paradigm to investigate the role of error-related MFC theta oscillations (associated with error monitoring) and memory biases in SA. EEG was collected while participants completed a novel Face-Flanker task, involving presentation of task-unrelated, trial-unique faces behind target/flanker arrows on each trial. A subsequent incidental memory assessment evaluated memory biases for error events. Severity of SA symptoms were associated with greater error-related theta synchrony over MFC, as well as between MFC and sensory cortex. SA was positively associated with memory biases for error events. Consistent with a mechanistic role in biased cognitive processing, greater error-related MFC-sensory theta synchrony during the Face-Flanker predicted subsequent memory biases for error events. Our findings suggest high SA individuals exhibit memory biases for error events, and that this behavioral phenomenon may be driven by error-related MFC-sensory theta synchrony associated with error monitoring. Moreover, results demonstrate the potential of a novel paradigm to elucidate mechanisms underlying relations between error monitoring and SA.

Backbone spiking sequence as a basis for preplay, replay, and default states in human cortex

Sequences of spiking activity have been heavily implicated as potential substrates of memory formation and retrieval across many species. A parallel line of recent evidence also asserts that sequential activity may arise from and be constrained by pre-existing network structure. Here we reconcile these two lines of research in the human brain by measuring single unit spiking sequences in the temporal lobe cortex as participants perform an episodic memory task. We find the presence of an average backbone spiking sequence identified during pre-task rest that is stable over time and different cognitive states. We further demonstrate that these backbone sequences are composed of both rigid and flexible sequence elements, and that flexible elements within these sequences serve to promote memory specificity when forming and retrieving new memories. These results support the hypothesis that pre-existing network dynamics serve as a scaffold for ongoing neural activity in the human cortex.

Micro-scale functional modules in the human temporal lobe

The sensory cortices of many mammals are often organized into modules in the form of cortical columns, yet whether modular organization at this spatial scale is a general property of the human neocortex is unknown. The strongest evidence for modularity arises when measures of connectivity, structure, and function converge. Here we use microelectrode recordings in humans to examine functional connectivity and neuronal spiking responses in order to assess modularity in submillimeter scale networks. We find that the human temporal lobe consists of temporally persistent spatially compact modules approximately 1.3mm in diameter. Functionally, the information coded by single neurons during an image categorization task is more similar for neurons belonging to the same module than for neurons from different modules. The geometry, connectivity, and spiking responses of these local cortical networks provide converging evidence that the human temporal lobe is organized into functional modules at the micro scale.

Ripples reflect a spectrum of synchronous spiking activity in human anterior temporal lobe

Direct brain recordings have provided important insights into how high-frequency activity captured through intracranial EEG (iEEG) supports human memory retrieval. The extent to which such activity is comprised of transient fluctuations that reflect the dynamic coordination of underlying neurons, however, remains unclear. Here, we simultaneously record iEEG, local field potential (LFP), and single unit activity in the human temporal cortex. We demonstrate that fast oscillations within the previously identified 80-120 Hz ripple band contribute to broadband high-frequency activity in the human cortex. These ripple oscillations exhibit a spectrum of amplitudes and durations related to the amount of underlying neuronal spiking. Ripples in the macro-scale iEEG are related to the number and synchrony of ripples in the micro-scale LFP, which in turn are related to the synchrony of neuronal spiking. Our data suggest that neural activity in the human temporal lobe is organized into transient bouts of ripple oscillations that reflect underlying bursts of spiking activity.

Optimal policy for attention-modulated decisions explains human fixation behavior

Traditional accumulation-to-bound decision-making models assume that all choice options are processed with equal attention. In real life decisions, however, humans alternate their visual fixation between individual items to efficiently gather relevant information (Yang et al., 2016). These fixations also causally affect one's choices, biasing them toward the longer-fixated item (Krajbich et al., 2010). We derive a normative decision-making model in which attention enhances the reliability of information, consistent with neurophysiological findings (Cohen and Maunsell, 2009). Furthermore, our model actively controls fixation changes to optimize information gathering. We show that the optimal model reproduces fixation-related choice biases seen in humans and provides a Bayesian computational rationale for this phenomenon. This insight led to additional predictions that we could confirm in human data. Finally, by varying the relative cognitive advantage conferred by attention, we show that decision performance is benefited by a balanced spread of resources between the attended and unattended items.

Feedforward prediction error signals during episodic memory retrieval

Our memories enable us to form expectations for our future experiences, yet the precise neural mechanisms underlying how we compare any experience to our memory remain unknown. Here, using intracranial EEG recordings, we show that episodic memories formed after a single visual experience establish expectations for future experience within neocortical-medial temporal lobe circuits. When subsequent experiences violate these expectations, we find a 80-120 Hz prediction error signal that emerges in both visual association areas and the medial temporal lobe. Critically, this error signal emerges in visual association areas first and then propagates to the medial temporal lobe. This error signal is accompanied by alpha coherence between the two regions. Our data therefore suggest that internal models formed from episodic memories are generated throughout the visual hierarchy after just a single exposure, and that these internal models are then used for comparison with future experiences.

Dynamic changes of timing precision in timed actions during a behavioural task in guinea pigs

Temporal precision is a determinant of performance in various motor activities. Although the accuracy and precision of timing in activities have been previously measured and quantified, temporal dynamics with flexible precision have not been considered. Here, we examined the temporal dynamics in timed motor activities (timed actions) using a guinea pig model in a behavioural task requiring an animal to control action timing to obtain a water reward. In well-trained animals, momentary variations in timing precision were extracted from the temporal distribution of the timed actions measured over daily 12-h sessions. The resampling of the observed time of action in each session demonstrated significant changes of timing precision within a session. Periods with higher timing precision appeared indiscriminately during the same session, and such periods lasted ~ 20 min on average. We conclude that the timing precision in trained actions is flexible and changes dynamically in guinea pigs. By elucidating the brain mechanisms involved in flexibility and dynamics with an animal model, future studies should establish more effective methods to actively enhance timing precision in our motor activities, such as sports.

Memorability of words in arbitrary verbal associations modulates memory retrieval in the anterior temporal lobe

Despite large individual differences in memory performance, people remember certain stimuli with overwhelming consistency. This phenomenon is referred to as the memorability of an individual item. However, it remains unknown whether memorability also affects our ability to retrieve associations between items. Here, using a paired-associates verbal memory task, we combine behavioural data, computational modelling and direct recordings from the human brain to examine how memorability influences associative memory retrieval. We find that certain words are correctly retrieved across participants irrespective of the cues used to initiate memory retrieval. These words, which share greater semantic similarity with other words, are more readily available during retrieval and lead to more intrusions when retrieval fails. Successful retrieval of these memorable items, relative to less memorable ones, results in faster reinstatement of neural activity in the anterior temporal lobe. Collectively, our data reveal how the brain prioritizes certain information to facilitate memory retrieval.

Higher hypnotic suggestibility is associated with the lower EEG signal variability in theta, alpha, and beta frequency bands

Variation of information in the firing rate of neural population, as reflected in different frequency bands of electroencephalographic (EEG) time series, provides direct evidence for change in neural responses of the brain to hypnotic suggestibility. However, realization of an effective biomarker for spiking behaviour of neural population proves to be an elusive subject matter with its impact evident in highly contrasting results in the literature. In this article, we took an information-theoretic stance on analysis of the EEG time series of the brain activity during hypnotic suggestions, thereby capturing the variability in pattern of brain neural activity in terms of its information content. For this purpose, we utilized differential entropy (DE, i.e., the average information content in a continuous time series) of theta, alpha, and beta frequency bands of fourteen-channel EEG time series recordings that pertain to the brain neural responses of twelve carefully selected high and low hypnotically suggestible individuals. Our results show that the higher hypnotic suggestibility is associated with a significantly lower variability in information content of theta, alpha, and beta frequencies. Moreover, they indicate that such a lower variability is accompanied by a significantly higher functional connectivity (FC, a measure of spatiotemporal synchronization) in the parietal and the parieto-occipital regions in the case of theta and alpha frequency bands and a non-significantly lower FC in the central region's beta frequency band. Our results contribute to the field in two ways. First, they identify the applicability of DE as a unifying measure to reproduce the similar observations that are separately reported through adaptation of different hypnotic biomarkers in the literature. Second, they extend these previous findings that were based on neutral hypnosis (i.e., a hypnotic procedure that involves no specific suggestions other than those for becoming hypnotized) to the case of hypnotic suggestions, thereby identifying their presence as a potential signature of hypnotic experience.

Replay of cortical spiking sequences during human memory retrieval

Episodic memory retrieval is thought to rely on the replay of past experiences, yet it remains unknown how human single-unit activity is temporally organized during episodic memory encoding and retrieval. We found that ripple oscillations in the human cortex reflect underlying bursts of single-unit spiking activity that are organized into memory-specific sequences. Spiking sequences occurred repeatedly during memory formation and were replayed during successful memory retrieval, and this replay was associated with ripples in the medial temporal lobe. Together, these data demonstrate that human episodic memory is encoded by specific sequences of neural activity and that memory recall involves reinstating this temporal order of activity.

Rapid and specific processing of person-related information in human anterior temporal lobe

The anterior temporal lobe (ATL), located at the tip of the human temporal lobes, has been heavily implicated in semantic processing by neuropsychological and functional imaging studies. These techniques have revealed a hemispheric specialization of ATL, but little about the time scale on which it operates. Here we show that ATL is specifically activated in intracerebral recordings when subjects discriminate the gender of an actor presented in a static frame followed by a video. ATL recording sites respond briefly (100 ms duration) to the visual static presentation of an actor in a task-, but not in a stimulus-duration-dependent way. Their response latencies correlate with subjects' reaction times, as do their activity levels, but oppositely in the two hemispheres operating in a push-pull fashion. Comparison of ATL time courses with those of more posterior, less specific regions emphasizes the role of inhibitory operations sculpting the fast ATL responses underlying semantic processing.