Annual Review Of Neuroscience Research Articles

Repetitive magnetic stimuli over the motor cortex impair long-term consolidation of a balance task by suppressing up-regulation of intracortical inhibition

Introduction
 Recent findings have demonstrated that low-frequency repetitive magnetic stimulations (rTMS) over the primary motor cortex (M1) impaired short-term consolidation of a balance task, underscoring the causal connection between M1 and the consolidation of balancing skills (Egger et al., 2023). However, the underlying neural mechanisms induced by rTMS and whether these adaptations endure over an extended period, encompassing multiple acquisition sessions, remain insufficiently elucidated (Censor & Cohen, 2011). So far, its is widely acknowledged that GABAergic processes play an important role for consolidation (Sanes & Donoghue, 2000), at the same time, are affected by learning balance skills (Mouthon & Taube, 2019; Taube et al., 2020). Therefore, the present study aimed to investigate the impact of rTMS on GABA-mediated short-interval intracortical inhibition (SICI) and to explore the role of M1 in the long-term consolidation of a balance task (i.e., across multiple acquisition sessions).
 Methods
 Thirty-one volunteers underwent six balance acquisition sessions on a rocker-board, each followed by either rTMS or sham rTMS based on group affiliation. During the first and last training session, SICI was measured twice; before the balance acquisition and after the application of rTMS or sham-rTMS to investigate potential short- and long-term adaptations in intracortical inhibition. Adaptations were assessed during the execution of the learned balance task and in a non-learning postural control task (i.e., stable upright stance).
 Results
 Regardless of group affiliation, all participants achieved comparable improvements within the balance acquisition sessions. However, consolidation varied between groups. In particular, between the third and the fourth acquisition session, as Tukey corrected post-hoc tests showed a significant decline in performance for the rTMS group (p = 0.006). Both short- (p = 0.014) and long-term (p = 0.038) adaptations in SICI were affected by rTMS: while the sham rTMS group upregulated SICI, rTMS led to reduced levels of inhibition. No neurophysiological effects were observed in the non-learning control task (upright stance).
 Discussion/Conclusion
 The interfering effect of rTMS on balance consolidation and on upregulation of SICI indicates that increased intracortical inhibition is an important mechanism to protect and engrave newly acquired motor memory. Importantly, adaptations in SICI were only apparent during the execution of the learned task.
 References
 Censor, N., & Cohen, L. G. (2011). Using repetitive transcranial magnetic stimulation to study the underlying neural mechanisms of human motor learning and memory. The Journal of Physiology, 589(1), 21-28. https://doi.org/10.1113/jphysiol.2010.198077
 Egger, S., Wälchli, M., Rüeger, E., & Taube, W. (2023). Short-term balance consolidation relies on the primary motor cortex: A rTMS study. Scientific Reports, 13, Article 5169. https://doi.org/10.1038/s41598-023-32065-x
 Mouthon, A., & Taube, W. (2019). Intracortical inhibition increases during postural task execution in response to balance training. Neuroscience, 401, 35-42. https://doi.org/10.1016/j.neuroscience.2019.01.007
 Sanes, J. N., & Donoghue, J. P. (2000). Plasticity and primary motor cortex. Annual Review of Neuroscience, 23, 393-415. https://doi.org/10.1146/annurev.neuro.23.1.393
 Taube, W., Gollhofer, A., & Lauber, B. (2020). Training-, muscle- and task-specific up- and downregulation of cortical inhibitory processes. The European Journal of Neuroscience, 51(6), 1428-1440. https://doi.org/10.1111/ejn.14538

Behavioral studies of spinal conditioning: The spinal cord is smarter than you think it is.

In 1988 Robert Rescorla published an article in the Annual Review of Neuroscience that addressed the circumstances under which learning occurs, some key methodological issues, and what constitutes an example of learning. The article has inspired a generation of neuroscientists, opening the door to a wider range of learning phenomena. After reviewing the historical context for his article, its key points are briefly reviewed. The perspective outlined enabled the study of learning in simpler preparations, such as the spinal cord. The period after 1988 revealed that pain (nociceptive) stimuli can induce a lasting sensitization of spinal cord circuits, laying down a kind of memory mediated by signal pathways analogous to those implicated in brain dependent learning and memory. Evidence suggests that the spinal cord is sensitive to instrumental response-outcome (R-O) relations, that learning can induce a peripheral modification (muscle memory) that helps maintain the learned response, and that learning can promote adaptive plasticity (a form of metaplasticity). Conversely, exposure to uncontrollable stimulation disables the capacity to learn. Spinal cord neurons can also abstract that stimuli occur in a regular (predictable) manner, a capacity that appears linked to a neural oscillator (central pattern generator). Disrupting communication with the brain has been shown to transform how GABA affects neuronal function (an example of ionic plasticity), releasing a brake that enables plasticity. We conclude by presenting a framework for understanding these findings and the implications for the broader study of learning. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

A Predictive Processing Account of Card Sorting: Fast Proactive and Reactive Frontoparietal Cortical Dynamics during Inference and Learning of Perceptual Categories.

For decades, a common assumption in cognitive neuroscience has been that prefrontal executive control is mainly engaged during target detection [Posner, M. I., & Petersen, S. E. The attention system of the human brain. Annual Review of Neuroscience, 13, 25-42, 1990]. More recently, predictive processing theories of frontal function under the Bayesian brain hypothesis emphasize a key role of proactive control for anticipatory action selection (i.e., planning as active inference). Here, we review evidence of fast and widespread EEG and magnetoencephalographic fronto-temporo-parietal cortical activations elicited by feedback cues and target cards in the Wisconsin Card Sorting Test. This evidence is best interpreted when considering negative and positive feedback as predictive cues (i.e., sensory outcomes) for proactively updating beliefs about unknown perceptual categories. Such predictive cues inform posterior beliefs about high-level hidden categories governing subsequent response selection at target onset. Quite remarkably, these new views concur with Don Stuss' early findings concerning two broad classes of P300 cortical responses evoked by feedback cues and target cards in a computerized Wisconsin Card Sorting Test analogue. Stuss' discussion of those P300 responses-in terms of the resolution of uncertainty about response (policy) selection as well as the participants' expectancies for future perceptual or motor activities and their timing-was prescient of current predictive processing and active (Bayesian) inference theories. From these new premises, a domain-general frontoparietal cortical network is rapidly engaged during two temporarily distinct stages of inference and learning of perceptual categories that underwrite goal-directed card sorting behavior, and they each engage prefrontal executive functions in fundamentally distinct ways.

Consensus emerges and biased competition wins: A commentary on Luck et al. (2021)

ABSTRACT As the debate about the automaticity of attentional capture has raged on over the years, knowledge of how selection functions has been accumulating in the literature. Luck et al. (2021) highlights emerging areas of consensus, including support for multiple mechanisms that influence attentional guidance. Here, I revisit the biased competition model of [Desimone, R., & Duncan, J. (1995). Neural mechanisms of selective visual attention. Annual Review of Neuroscience, 18(1), 193–222. https://doi.org/10.1146/annurev.ne.18.030195.001205] to bring additional perspective. This aims to provide insight about open questions of “control” and to offer guidance in how to address other conceptual issues that hinder progress toward a better understanding of attentional functioning.

Mindfulness and Attention: Current State-of-Affairs and Future Considerations.

This review examines longitudinal studies of changes in components of attention following mindfulness training. A total of 57 retreat studies, non-randomized trials, and randomized controlled trials were identified. Employing the classical taxonomy proposed by Posner and Petersen (1990), outcome measures were broadly categorized based on whether they involved maintenance of an aroused state (alerting), selective prioritization of attention to target items (orienting), or assessed conflict monitoring (executive attention). Although many non-randomized and retreat studies provide promising evidence of gains in both alerting and conflict monitoring following mindfulness training, evidence from randomized controlled trials, especially those involving active control comparison groups, is more mixed. This review calls attention to the urgent need in our field of contemplative sciences to adopt the methodological rigor necessary for establishing mindfulness meditation as an effective cognitive rehabilitation tool. Although studies including wait-listed control comparisons were fruitful in providing initial feasibility data and pre-post effect sizes, there is a pressing need to employ standards that have been heavily advocated for in the broader cognitive and physical training literatures. Critically, inclusion of active comparison groups and explicit attention to the reduction of demand characteristics are needed to disentangle the effects of placebo from treatment. Further, detailed protocols for mindfulness and control groups and examination of theoretically guided outcome variables with established metrics for reliability and validity are key ingredients in the systematic study of mindfulness meditation. Adoption of such methodological rigor will allow for causal claims supporting mindfulness training as an efficacious treatment modality for cognitive rehabilitation and enhancement.

Connectome-based Models Predict Separable Components of Attention in Novel Individuals.

Although we typically talk about attention as a single process, it comprises multiple independent components. But what are these components, and how are they represented in the functional organization of the brain? To investigate whether long-studied components of attention are reflected in the brain's intrinsic functional organization, here we apply connectome-based predictive modeling (CPM) to predict the components of Posner and Petersen's influential model of attention: alerting (preparing and maintaining alertness and vigilance), orienting (directing attention to a stimulus), and executive control (detecting and resolving cognitive conflict) [Posner, M. I., & Petersen, S. E. The attention system of the human brain. Annual Review of Neuroscience, 13, 25-42, 1990]. Participants performed the Attention Network Task (ANT), which measures these three factors, and rested during fMRI scanning. CPMs tested with leave-one-subject-out cross-validation successfully predicted novel individual's overall ANT accuracy, RT variability, and executive control scores from functional connectivity observed during ANT performance. CPMs also generalized to predict participants' alerting scores from their resting-state functional connectivity alone, demonstrating that connectivity patterns observed in the absence of an explicit task contain a signature of the ability to prepare for an upcoming stimulus. Suggesting that significant variance in ANT performance is also explained by an overall sustained attention factor, the sustained attention CPM, a model defined in prior work to predict sustained attentional abilities, predicted accuracy, RT variability, and executive control from task-based data and predicted RT variability from resting-state data. Our results suggest that, whereas executive control may be closely related to sustained attention, the infrastructure that supports alerting is distinct and can be measured at rest. In the future, CPM may be applied to elucidate additional independent components of attention and relationships between the functional brain networks that predict them.

Pupil Diameter Tracks the Exploration-Exploitation Trade-off during Analogical Reasoning and Explains Individual Differences in Fluid Intelligence.

The ability to adaptively shift between exploration and exploitation control states is critical for optimizing behavioral performance. Converging evidence from primate electrophysiology and computational neural modeling has suggested that this ability may be mediated by the broad norepinephrine projections emanating from the locus coeruleus (LC) [Aston-Jones, G., & Cohen, J. D. An integrative theory of locus coeruleus-norepinephrine function: Adaptive gain and optimal performance. Annual Review of Neuroscience, 28, 403-450, 2005]. There is also evidence that pupil diameter covaries systematically with LC activity. Although imperfect and indirect, this link makes pupillometry a useful tool for studying the locus coeruleus norepinephrine system in humans and in high-level tasks. Here, we present a novel paradigm that examines how the pupillary response during exploration and exploitation covaries with individual differences in fluid intelligence during analogical reasoning on Raven's Advanced Progressive Matrices. Pupillometry was used as a noninvasive proxy for LC activity, and concurrent think-aloud verbal protocols were used to identify exploratory and exploitative solution periods. This novel combination of pupillometry and verbal protocols from 40 participants revealed a decrease in pupil diameter during exploitation and an increase during exploration. The temporal dynamics of the pupillary response was characterized by a steep increase during the transition to exploratory periods, sustained dilation for many seconds afterward, and followed by gradual return to baseline. Moreover, the individual differences in the relative magnitude of pupillary dilation accounted for 16% of the variance in Advanced Progressive Matrices scores. Assuming that pupil diameter is a valid index of LC activity, these results establish promising preliminary connections between the literature on locus coeruleus norepinephrine-mediated cognitive control and the literature on analogical reasoning and fluid intelligence.

Multiple Perspectives on Body Image Research

Representation of the body is a nuclear aspect of self-image. Body representation includes both subjective and intersubjective experiences. The importance of visual body representation in our social life is demonstrated by the time we spend to take care of our physical appearance, including use of plastic surgery, as well as by the severe mental disorders associated to its alteration, including eating disorders (EDs) and body dysmorphic disorders. In spite of these issues, (neuro)psychological research on body representation has so far mainly focused on the body as a motor device, devoted to the perception of and interaction with objects. The complexity of factors involved in the development, maintenance, and plasticity of body image representations requires an integrated approach that facilitates the evaluation and treatment of EDs with novel, evidence-based, and more efficacious protocols. This special issue of European Psychologist aims to advance such an integrative approach, with a collection of papers that gather different perspectives on the phenomenological, cognitive, (neuro)psychological, and cultural aspects of body representation disorders.

Seeing What We Know, Knowing What We See: Challenging the Limits of Visual Acuity

Ageism has resulted in overstated expectations regarding the inevitable deterioration in human capabilities, such as visual perception, with age (Rowe and Kahn in Science, 237, 143–149, 1987; Grant in Health and Social Work, 21, 9–15, 1996). Human visual perception, however, is of a largely constructive nature, evidenced in the complementary interactions between top-down inputs (e.g., expectations) and bottom-up stimuli (Engel et al. in National Review of Neuroscience, 2(10), 704–716, 2001; Miller and Cohen in, Annual Review of Neuroscience, 24, 167-202, 2001). Based on this constructive nature, we hypothesized that visual perception may be better than is typically expected. In three experiments, we demonstrated the malleability of visual acuity using a conditioning procedure involving manipulations in bottom-up stimuli. Experimental groups read a book excerpt with one letter in decreased font size, while the control groups read the same book excerpt with all letters in the same font size. Experiment 1 (N = 112) examined whether visual acuity could be enhanced for a specific letter. Experiment 2 (N = 70) assessed whether visual acuity could be enhanced for a non-conditioned letter, while Experiment 3 (N = 108) evaluated whether the visual conditioning effects would transfer to all non-conditioned letters. Visual acuity for experimental groups was significantly better than that in the control groups, speaking to the general malleability of our visual sense.

Disentangling motor control processes in the basal ganglia using high-resolution fMRI in a 3T scanner

Event Abstract Back to Event Disentangling motor control processes in the basal ganglia using high-resolution fMRI in a 3T scanner Megan E. Campbell1*, Jeff Bednark1* and Ross Cunnington1 1 The Queensland Brain Institute, The University of Queensland, Australia Our ability to interact with the environment is mediated by motor control processes that are largely controlled by basal ganglia-thalamo-cortico circuits (Alexander, 1986). However, our understanding of how specific motor control processes are represented in the intricate circuitry of the basal ganglia is poorly understood. Thus, using high-resolution fMRI (1.5x1.5mm) we investigated whether two fundamental motor control processes, the sequential structure and the temporal rhythm of movements, could be independently identified within the basal ganglia. Participants made short button-press responses to visual cues over three conditions: Simple, Complex-Rhythm and Complex-Sequence. At the cortical level our results revealed that partially independent cortical networks mediated motor sequencing and motor rhythm. A fronto-parietal network was more active for motor sequencing and the supplementary motor area was more active for motor rhythm. The application of high-resolution fMRI revealed that bilateral activation across the putamen, caudate and thalamus was common to all movement conditions. Crucially, we found that while the two complex movement conditions activated common portions of the putamen and thalamus; motor rhythm selectively activated regions of the basal ganglia to a greater degree. Specifically, motor rhythm had greater activation in dorsomedial portions of the right putamen and dorsolateral portions of the right caudate (see figure 1). This activation is consistent the with known role of the putamen in general timing processes (Draganski, 2008) and ordinal aspects of motor sequencing (Ferrandez, 2003). Moreover, additional recruitment of the caudate in the rhthym condition given its role in executive control circuits may reflect the greater need for executive control processes for co-ordination of rhythmic timing. In conclusion, our results demonstrate how high-resolution fMRI can help unravel the intricate circuitry of the basal ganglia mediating motor control. Figure 1 Acknowledgements This experiment was conducted by the first author, under the supervision of Associate Professor Cunnington, in partial completion of the Masters of Neuroscience program (Higher Research Degree) at the QBI, through The University of Queensland). References Alexander, G. E., Delong, M. R., & Strick, P. L. (1986). Parallel organization of functionally segregated circuits link basal ganglia and cortex. Annual Review of Neuroscience, 9, 357-381. Draganski, B., Kherif, F., Kloeppel, S., Cook, P. A., Alexander, D. C., Parker, G. J. M., Deichmann, R., Ashburner, J., & Frackowiak, R. S. J. (2008). Evidence for segregated and integrative connectivity patterns in the human basal ganglia. Journal of Neuroscience, 28, 7143-7152. Ferrandez, A. M., Hugueville, L., Lehericy, S., Poline, J. B., Marsault, C., & Pouthas, V. (2003). Basal ganglia and supplementary motor area subtend duration perception: an fMRI study. Neuroimage, 19, 1532-1544. Keywords: Basal Ganglia, Thalamus, motor control, fMRI BOLD, basal ganglia-thalamo-cortico circuits Conference: ACNS-2012 Australasian Cognitive Neuroscience Conference, Brisbane, Australia, 29 Nov - 2 Dec, 2012. Presentation Type: Poster Presentation Topic: Motor Citation: Campbell ME, Bednark J and Cunnington R (2012). Disentangling motor control processes in the basal ganglia using high-resolution fMRI in a 3T scanner. Conference Abstract: ACNS-2012 Australasian Cognitive Neuroscience Conference. doi: 10.3389/conf.fnhum.2012.208.00023 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 12 Oct 2012; Published Online: 07 Nov 2012. * Correspondence: Ms. Megan E Campbell, The Queensland Brain Institute, The University of Queensland, Brisbane, Australia, megan.ej.campbell@uq.edu.au Dr. Jeff Bednark, The Queensland Brain Institute, The University of Queensland, Brisbane, Australia, j.g.bednark@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Megan E Campbell Jeff Bednark Ross Cunnington Google Megan E Campbell Jeff Bednark Ross Cunnington Google Scholar Megan E Campbell Jeff Bednark Ross Cunnington PubMed Megan E Campbell Jeff Bednark Ross Cunnington Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Layer specific neuronal activities in response to visual object images in the inferior temporal cortex revealed by current source density analysis

Layer specific neuronal activities in response to visual object images in the inferior temporal cortex revealed by current source density analysis

Orienting of attention, pupil size, and the norepinephrine system

This research examined a novel suggestion regarding the involvement of the locus coeruleus-norepinephrine (LC-NE) system in orienting reflexive (exogenous) attention. A common procedure for studying exogenous orienting of attention is Posner's cuing task. Importantly, one can manipulate the required level of target processing by changing task requirements, which, in turn, can elicit a different time course of inhibition of return (IOR). An easy task (responding to target location) produces earlier onset IOR, whereas a demanding task (responding to target identity) produces later onset IOR. Aston-Jones and Cohen (Annual Review of Neuroscience, 28, 403-450, 2005) presented a theory suggesting two different modes of LC activity: tonic and phasic. Accordingly, we suggest that in the more demanding task, the LC-NE system is activated in phasic mode, and in the easier task, it is activated in tonic mode. This, in turn, influences the appearance of IOR. We examined this suggestion by measuring participants' pupil size, which has been demonstrated to correlate with the LC-NE system, while they performed cuing tasks. We found a response-locked phasic dilation of the pupil in the discrimination task, as compared with the localization task, which may reflect different firing modes of the LC-NE system during the two tasks. We also demonstrated a correlation between pupil size at the time of cue presentation and magnitude of IOR.

Distinct brain networks in recognition memory share a defined region in the precuneus

Current models of recognition memory performance postulate that there are two fundamentally distinct retrieval processes, i.e. recollection and familiarity. This view has been challenged and little is known from human research about the functional connectivity of the brain areas involved in these processes. In our study we used a Remember-Know procedure to assess the functional connectivity of brain regions under recognition memory in 30 healthy adults. Using functional magnetic resonance imaging, we analysed the blood oxygen level-dependent responses during correct Remember, correct Know, correct Rejection and missed responses of the subjects during recognition of non-emotional nouns. One activation cluster was found in the left precuneus associated with both recollection and familiarity answers. To acquire information about the way in which activity in one brain region modulates activity in another brain region in response to the active task, we performed a psychophysiological interaction analysis with the left precuneus as a seed region. This analysis revealed functionally distinct networks of brain areas underlying recollection and familiarity. Furthermore, we discuss the differential involvement of the hippocampus in a recollection network as compared with a familiarity network. In summary, our results further strengthen the assumptions of a dual-process view of recognition memory [e.g. H. Eichenbaum et al. (2007) Annual Review of Neuroscience, 30, 123-152; A.P. Yonelinas (2001) Philosophical Transactions of the Royal Society London B Biological Sciences, 356, 1363-1374] and add empirical findings about the functional interconnectivity of brain regions supporting either recollection or familiarity.

Spatial attention in area V4 is mediated by circuits in primary visual cortex

The ability to covertly select visual stimuli in our environment based on their behavioral relevance is an important skill. Stimulus selection has been studied experimentally, at the single neuron as well as at the population level, by recording from the visual cortex of subjects performing attention-demanding tasks, but studies at the local circuit level are lacking. We conducted simulations of a primary visual cortex (V1) model to provide insight into the local circuit computation underlying stimulus selection in V4. Two small oriented rectangular bars were placed at different locations in the 4 by 4 degree visual field represented by the V1 model, such that they activated different V1 neurons but such that they were both inside the classical receptive field (CRF) of the same V4 neuron. The biased competition framework [Desimone, R., & Duncan, J. (1995). Neural mechanisms of selective visual attention. Annual Review of Neuroscience, 18, 193-222] makes predictions for the response of V4 neurons and the modulation thereof by spatial and feature attention. In our simulation of the V1 network, we obtained results consistent with these predictions for V4 when the model had long-range excitatory projections targeting inhibitory neurons and when spatial attention was mediated by a spatially restricted projection that either inhibited the inhibitory neurons or excited the excitatory neurons. Although it is not clear whether attention effects measured in V4 neurons are generated mostly by local circuits within V4, our simulations suggest that spatial attention at a resolution less than the size of the CRF of a V4 neuron is inherited from upstream areas like V1 and relies on circuits mediating surround suppression at the single neuron level. Furthermore, the model displayed global oscillations in the alpha frequency range (around 10 Hz), whose coherence was highest in the absence of visual stimulation, which is consistent with electroencephalograms recorded in humans. By contrast, when a stimulus was presented the alpha oscillation sped up and became less coherent, whereas at the single column level (40-480 cells) transient beta/gamma oscillations were observed with a frequency between 25 and 50 Hz.

Neural correlates of metaphor processing: The roles of figurativeness, familiarity and difficulty

There is currently much interest in investigating the neural substrates of metaphor processing. In particular, it has been suggested that the right hemisphere plays a special role in the comprehension of figurative (non-literal) language, and in particular metaphors. However, some studies find no evidence of right hemisphere involvement in metaphor comprehension (e.g. [Lee, S. S., & Dapretto, M. (2006). Metaphorical vs. literal word meanings: fMRI evidence against a selective role of the right hemisphere. NeuroImage, 29, 536–544; Rapp, A. M., Leube, D. T., Erb, M., Grodd, W., & Kircher, T. T. J. (2004). Neural correlates of metaphor processing. Cognitive Brain Research, 20, 395–402]). We suggest that lateralization differences between literal and metaphorical language may be due to factors such as differences in familiarity ([Schmidt, G. L., DeBuse, C. J., & Seger, C. A. (2007). Right hemisphere metaphor processing? Characterizing the lateralization of semantic processes. Brain and Language, 100, 127–141]), or difficulty ([Bookheimer, S. (2002). Functional MRI of language: New approaches to understanding the cortical organization of semantic processing. Annual Review of Neuroscience, 25, 151–188; Rapp, A. M., Leube, D. T., Erb, M., Grodd, W., & Kircher, T. T. J. (2004). Neural correlates of metaphor processing. Cognitive Brain Research, 20, 395–402]) in addition to figurativeness. The purpose of this study was to separate the effects of figurativeness, familiarity, and difficulty on the recruitment of neural systems involved in language, in particular right hemisphere mechanisms. This was achieved by comparing neural activation using functional magnetic resonance imaging (fMRI) between four conditions: literal sentences, familiar and easy to understand metaphors, unfamiliar and easy to understand metaphors, and unfamiliar and difficult to understand metaphors. Metaphors recruited the right insula, left temporal pole and right inferior frontal gyrus in comparison with literal sentences. Familiar metaphors recruited the right middle frontal gyrus when contrasted with unfamiliar metaphors. Easy metaphors showed higher activation in the left middle frontal gyrus as compared to difficult metaphors, while difficult metaphors showed selective activation in the left inferior frontal gyrus as compared to easy metaphors. We conclude that the right hemisphere is involved in metaphor processing and that the factors of figurativeness, familiarity and difficulty are important in determining neural recruitment of semantic processing.

Task context and organization in free recall

Prior work on organization in free recall has focused on the ways in which semantic and temporal information determine the order in which material is retrieved from memory. Tulving's theory of ecphory suggests that these organizational effects arise from the interaction of a retrieval cue with the contents of memory. Using the continual-distraction free-recall paradigm [Bjork, R. A., & Whitten, W. B. (1974). Recency-sensitive retrieval processes in long-term free recall. Cognitive Psychology, 6, 173-189] to minimize retrieval during the study period, we show that encoding task context can organize recall, suggesting that task-related information is part of the retrieval cue. We interpret these results in terms of the Context Maintenance and Retrieval model (CMR; [Polyn, S. M., Norman, K. A., & Kahana, M. J. (2009). A context maintenance and retrieval model of organizational processes in free recall. Psychological Review, 116 (1), 129-156]), in which an internal contextual representation, containing semantic, temporal, and source-related information, serves as the retrieval cue and organizes the retrieval of information from memory. We discuss these results in terms of the guided activation theory [Miller, E. K., & Cohen, J. D. (2001). An integrative theory of prefrontal cortex function. Annual Review of Neuroscience, 24, 167-202] of the role of prefrontal cortex in task performance, as well as the rich neuropsychological literature implicating prefrontal cortex in memory search (e.g., Schacter (1987). Memory, amnesia, and frontal lobe dysfunction. Psychobiology, 15, 21-36).

Emotion Circuits in the Brain

The field of neuroscience has, after a long period of looking the other way, again embraced emotion as an important research area. Much of the progress has come from studies of fear, and especially fear conditioning. This work has pin-pointed the amygdala as an important component of the system involved in the acquisition, storage, and expression of fear memory and has elucidated in detail how stimuli enter, travel through, and exit the amygdala. Some progress has also been made in understanding the cellular and molecular mechanisms that underlie fear conditioning, and recent studies have also shown that the findings from experimental animals apply to the human brain. It is important to remember why this work on emotion succeeded where past efforts failed. It focused on a psychologically well-defined aspect of emotion, avoided vague and poorly defined concepts such as “affect,” “hedonic tone,” or “emotional feelings,” and used a simple and straightforward experimental approach. With so much research being done in this area today, it is important that the mistakes of the past not be made again. It is also time to expand from this foundation into broader aspects of mind and behavior. (Reprinted with permission from Annual Review of Neuroscience; 2000. 23:155–184. Available online at http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.neuro.23.1.155 )

The basolateral amygdala modulates specific sensory memory representations in the cerebral cortex

Stress hormones released by an experience can modulate memory strength via the basolateral amygdala, which in turn acts on sites of memory storage such as the cerebral cortex [McGaugh, J. L. (2004). The amygdala modulates the consolidation of memories of emotionally arousing experiences. Annual Review of Neuroscience, 27, 1–28]. Stimuli that acquire behavioral importance gain increased representation in the cortex. For example, learning shifts the tuning of neurons in the primary auditory cortex (A1) to the frequency of a conditioned stimulus (CS), and the greater the level of CS importance, the larger the area of representational gain [Weinberger, N. M. (2007). Associative representational plasticity in the auditory cortex: A synthesis of two disciplines. Learning & Memory, 14(1–2), 1–16]. The two lines of research suggest that BLA strengthening of memory might be accomplished in part by increasing the representation of an environmental stimulus. The present study investigated whether stimulation of the BLA can affect cortical memory representations. In male Sprague–Dawley rats studied under urethane general anesthesia, frequency receptive fields were obtained from A1 before and up to 75 min after the pairing of a tone with BLA stimulation (BLAstm: 100 trials, 400 ms, 100 Hz, 400 μA [±16.54]). Tone started before and continued after BLAstm. Group BLA/1.0 ( n = 16) had a 1 s CS–BLAstm interval while Group BLA/1.6 ( n = 5) has a 1.6 s interval. The BLA/1.0 group did develop specific tuning shifts toward and to the CS, which could change frequency tuning by as much as two octaves. Moreover, its shifts increased over time and were enduring, lasting 75 min. However, group BLA/1.6 did not develop tuning shifts, indicating that precise CS–BLAstm timing is important in the anesthetized animal. Further, training in the BLA/1.0 paradigm but stimulating outside of the BLA did not produce tuning shifts. These findings demonstrate that the BLA is capable of exerting highly specific, enduring, learning-related modifications of stimulus representation in the cerebral cortex. These findings suggest that the ability of the BLA to alter specific cortical representations may underlie, at least in part, the modulatory influence of BLA activity on strengthening long-term memory.

The hypergeometric connectivity hypothesis: Divergent performance of brain circuits with different synaptic connectivity distributions

The development of connectivity among brain networks (e.g., thalamocortical, cortico-thalamic, cortico-cortical) proceeds via a combination of axon and dendrite growth followed by a later process of synaptic pruning [Purves, D., Lichtman, J.W., 1980. Elimination of synapses in the developing nervous system. Science, 210, 153–157; Oppenheim, R.W., 1991. Cell death during development of the nervous system. Annual Review of Neuroscience, 14(1), 453–501.; Oppenheim, R., Qin-Wei Y., Prevette D., Yan Q., 1992. Brain-derived neurotrophic factor rescues developing avian motoneurons from cell death. Nature, 360, 755–757]. Sparse synaptic distribution (i.e., the low probability (< 0.1) of contact among neurons; [Braitenberg, V., Schüz, A., 1998. Cortex: Statistics and geometry of neuronal connectivity: Springer Berlin.] can conform to any of a range of connectivity patterns with different distributional characteristics; and different distribution patterns can yield networks with very different functional properties. We rigorously investigate a range of different connectivity characteristics, and show that different synaptic distributions can substantially affect the functional capabilities of the resulting networks. In particular, we provide formal measures of information loss in transmission from one set of neurons to another as a function of synaptic distribution, and show a set of empirical cases with different information-theoretic utility. We characterize the trade-offs among utility and costs, and their dependence on different classes of developmental strategies by which axons from one cell group are “assigned” to synapses on dendrites from a target cell group. It is shown that hypergeometric distributions minimize a range of measured costs, compared to competing synaptic distributions. It is also found that the divergent performance among differently organized brain circuits expands with brain size, rendering the effects increasingly consequential for big brains. In summary, we propose that the characteristics of hypergeometric connectivity provide a coherent explanatory hypothesis of a range of developmental and anatomical data.

Analysis of attention and analogical reasoning in children of poverty

This study examined the relationship between specific attentional aspects of processing capacity and analogical reasoning in children from low-income families. 77 children aged 48–77 ( M = 56.7) months were assessed on an analogical reasoning task (matrices subtest of the Kaufman Brief Intelligence Test) and on computerized attention tasks designed to assess orienting, vigilance, and executive attention abilities [Posner, M.I., and Petersen, S.E. (1990). The attention system of the human brain. Annual Review of Neuroscience, 13, 25–42]. Results showed that analogical reasoning abilities were associated with the executive attention network abilities, suggesting that skills associated with this network, such as the resolution of conflicts between competing demands on attention, may be particularly important for relational mapping. This was evident in girls only. Implications for understanding how attentional components of processing capacity can affect children's academic success in impoverished environments are discussed.