Behavioral and functional MRI study of attention shift in human verbal working memory

Neuroanatomy of complex social emotion dysregulation in adolescent offenders

Social emotions require the correct integration of emotional, cognitive, and social processes and are critical for complex social interactions. Adolescent criminal offenders (AOs) show abnormalities in the experience of basic emotions. However, most research has focused solely on basic emotions, neglecting complex social emotions that could be critical for social reintegration. The purpose of this study was to investigate the behavioral and neural correlates of social emotions (envy and Schadenfreude) in AOs. We explored the experience of complex social emotions, as well as their anatomical correlates, in AOs (n = 19) and a nonoffenders control group (NOs, n = 20). Additionally, we assessed the relationship between social emotions, executive functions (EFs), and fluid intelligence (FI). Structural brain imaging was obtained in all participants. The results showed that AOs had significantly lower envy and Schadenfreude ratings and exhibited lower performance in EFs compared with NOs. The measurement of EFs relied on the INECO frontal screening (IFS). Experiencing fewer social emotions was associated with diminished EFs but not with FI. Moreover, in AOs, reduced levels of envy and Schadenfreude were linked with reduced gray matter volumes in regions subserving mentalizing abilities (inferior parietal lobe and precuneus) and socioemotional processing (inferior and middle temporal regions), as well as key hubs of the executive frontoparietal network (inferior parietal lobule, orbital and rectus gyri). Additional analysis on the AOs revealed no associations between the type of crime and our variables of interest (EFs, FI and social emotions). Our findings are the first to provide evidence on abnormalities in the experience of social emotions in AOs that are associated with neurocognitive markers of social cognition and EFs. Understanding social emotions and their abnormalities (under-experience) as complex intertwined processes may have important future translational implications, including risk prediction for social adaptation/reintegration, sociocognitive targeted interventions, and skill training for social emotions in vulnerable populations.

Brain hemodynamic response in Examiner-Examinee dyads during spatial short-term memory task: an fNIRS study

The Corsi Block-Tapping test (CBT) is a measure of spatial working memory (WM) in clinical practice, requiring an examinee to reproduce sequences of cubes tapped by an examiner. CBT implies complementary behaviors in the examiners and the examinees, as they have to attend a precise turn taking. Previous studies demonstrated that the Prefrontal Cortex (PFC) is activated during CBT, but scarce evidence is available on the neural correlates of CBT in the real setting. We assessed PFC activity in dyads of examiner–examinee participants while completing the real version of CBT, during conditions of increasing and exceeding workload. This procedure allowed to investigate whether brain activity in the dyads is coordinated. Results in the examinees showed that PFC activity was higher when the workload approached or reached participants’ spatial WM span, and lower during workload conditions that were largely below or above their span. Interestingly, findings in the examiners paralleled the ones in the examinees, as examiners’ brain activity increased and decreased in a similar way as the examinees’ one. In the examiners, higher left-hemisphere activity was observed suggesting the likely activation of non-spatial WM processes. Data support a bell-shaped relationship between cognitive load and brain activity, and provide original insights on the cognitive processes activated in the examiner during CBT.

The Oscillatory Basis of Working Memory Function and Dysfunction in Epilepsy

Working memory (WM) deficits are pervasive co-morbidities of epilepsy. Although the pathophysiological mechanisms underpinning these impairments remain elusive, it is thought that WM depends on oscillatory interactions within and between nodes of large-scale functional networks. These include the hippocampus and default mode network as well as the prefrontal cortex and frontoparietal central executive network. Here, we review the functional roles of neural oscillations in subserving WM and the putative mechanisms by which epilepsy disrupts normative activity, leading to aberrant oscillatory signatures. We highlight the particular role of interictal epileptic activity, including interictal epileptiform discharges and high frequency oscillations (HFOs) in WM deficits. We also discuss the translational opportunities presented by greater understanding of the oscillatory basis of WM function and dysfunction in epilepsy, including potential targets for neuromodulation.

Impaired theory of mind in Chinese children and adolescents with idiopathic generalized epilepsy: Association with behavioral manifestations of executive dysfunction

BACKGROUND

Epilepsy is a common neurological disorder with a core feature of cognitive impairments. Previous studies showed that patients with focal epilepsy have deficits in both theory of mind (ToM) and executive function (EF). However, there are few studies of ToM in patients with idiopathic generalized epilepsy (IGE), especially in populations with pediatric epilepsy. The aim of this study was to examine the characteristics of ToM and EF, including some of their subcomponents, and explore the relationship between them in Chinese children with IGE.

MATERIALS AND METHODS

We recruited 54 children and adolescents with IGE as the experimental subjects and 37 typically developing children and adolescents as control subjects. Both groups completed ToM tests, namely, second-order false belief tasks (FBTs) and faux pas tasks (FPTs). Their caregivers completed the Behavior Rating Inventory of Executive Function (BRIEF) at the same time.

RESULTS

Children and adolescents with IGE displayed worse performance on some of the FBTs and FPTs than healthy controls (p<0.01). They also exhibited widespread EF deficits, comprising eight subcomponents (p<0.05). Pearson's correlation analysis revealed that several subcomponents of EF (inhibition, emotional control, initiation, working memory, and monitoring) were unequally correlated with FBT and FPT. Regression analysis showed that ToM had associations with inhibition, working memory, and duration of seizures. Analysis of variance (ANOVA) indicated that children with newly diagnosed epilepsy displayed significant deficits in FBT, FPT, and distinct subscales of EF.

CONCLUSIONS

Our results revealed significant impairments in ToM and EF in children and adolescents with IGE compared with healthy controls. We found significant correlations between ToM and two subcomponents of EF (inhibition and working memory) in children with IGE. Additionally, the duration of seizures affected ToM in patients but was a less powerful predictor than the two subcomponents of EF. Even for children with new-onset seizures and without medication, the deficits in ToM and some distinct subscales of EF were apparent. This result has clinical implications for both nonpharmaceutical therapies and cognitive rehabilitation.

Functional neuroanatomy on the working memory under emotional distraction in patients with generalized anxiety disorder

AIMS

Patients with generalized anxiety disorder (GAD) suffer the symptoms of psychological distress, including excessive and uncontrollable anxiety. Until now, the functional neuroanatomy for working memory (WM) in conjunction with the major anxiety symptoms in GAD patients has not yet been clearly identified. This study investigated the neural activation patterns associated with the effect of neutral and anxiety-inducing distractors during the delayed-response WM task in GAD patients.

METHODS

Eighteen patients with GAD and 18 age-matched healthy controls participated in this study. The functional magnetic resonance images were obtained while the subjects performed a delayed-response WM task with neutral and anxiety-inducing distractors.

RESULTS

During the neutral distractor, GAD patients compared to controls showed significantly lower activities in the fusiform gyrus, superior parietal gyrus, precuneus, superior occipital gyrus, lingual gyrus, cuneus, calcarine gyrus, parahippocampal gyrus and cerebellar cortex. During the anxiety-inducing distractor, GAD patients showed significantly higher activity in the hippocampus, whereas they showed lower activities in the dorsolateral prefrontal cortex, fusiform gyrus, superior parietal gyrus, precuneus, superior occipital gyrus and cerebellar cortex. The blood-oxygen-level dependent signal changes in the dorsolateral prefrontal cortex in GAD patients during the anxiety-inducing distractor were negatively correlated with Anxiety Sensitivity Index-Revised scores.

CONCLUSIONS

This study identified the specific brain areas associated with the interaction between emotional regulation and cognitive function associated with neutral and anxiety-inducing distractors during WM maintenance in GAD patients. These findings will be helpful for understanding the neural mechanism on the WM-related cognitive deficits and emotional dysfunction with typical anxiety symptoms in GAD.

The combined effects of neurostimulation and priming on creative thinking. A preliminary tDCS study on dorsolateral prefrontal cortex

The role of prefrontal cortex (PFC) in influencing creative thinking has been investigated by many researchers who, while succeeding in proving an effective involvement of PFC, reported suggestive but sometimes conflicting results. In order to better understand the relationships between creative thinking and brain activation in a more specific area of the PFC, we explored the role of dorsolateral PFC (DLPFC). We devised an experimental protocol using transcranial direct-current stimulation (tDCS). The study was based on a 3 (kind of stimulation: anodal vs. cathodal vs. sham) × 2 (priming: divergent vs. convergent) design. Forty-five healthy adults were randomly assigned to one stimulation condition. Participants' creativity skills were assessed using the Product Improvement subtest from the Torrance Tests of Creative Thinking (TTCT). After 20 min of tDCS stimulation, participants were presented with visual images of common objects. Half of the participants were instructed to visualize themselves using the object in an unusual way (divergent priming), whereas the other half were asked to visualize themselves while using the object in a common way (convergent priming). Priming was aimed at inducing participants to adopt different attitudes toward the creative task. Afterwards, participants were asked to describe all of the possible uses of the objects that were presented. Participants' physiological activation was recorded using a biofeedback equipment. Results showed a significant effect of anodal stimulation that enhanced creative performance, but only after divergent priming. Participants showed lower skin temperature values after cathodal stimulation, a finding which is coherent with studies reporting that, when a task is not creative or creative thinking is not prompted, people show lower levels of arousal. Differences in individual levels of creativity as assessed by the Product Improvement test were not influential. The involvement of DLPFC in creativity has been supported, presumably in association to shift of attention modulated by priming.

The link between impaired theory of mind and executive function in children with cerebral palsy

The aim of the study was to explore the relationship between theory of mind (ToM) deficits and executive function (EF) impairments in children with cerebral palsy (CP), 42 CP with children and 42 typically developing (TD) children, acting as controls, were assessed on the tasks of ToM (false belief and faux pas) and EF (inhibition, updating and shifting). Results showed that CP children had deficits both in ToM and EF tasks. The correlation analyses showed that two EF components (inhibition and updating) were strongly related to false belief and faux pas in both two groups. We also found correlation between shifting and false belief and faux pas. However, this correlation was only found in TD children and not in children with CP. These findings suggest that children with CP lag behind TD children in both ToM and EF. Further, the results reveal, interestingly, that ToM deficits in CP children might be related to their inhibition and updating impairments, but not to shifting impairments.

Parietal cortical neuronal activity is selective for express saccades

Saccadic eye movements are central to primate behavior and serve to move the eyes to visual objects of interest. Express saccades, unlike regular saccades, occur with very short reaction times, a behavior necessary for speeded reactions in goal-directed behavior. Previous studies have shown that introduction of a blank interval (gap) between the fixation point offset and the saccadic target onset leads to an increase in the number of express saccades and that the superior colliculus plays a crucial role in the generation of express saccades. A longstanding hypothesis asserted that express saccades are mediated largely by a subcortical circuit, circumventing extrastriate visual cortex. An alternative "posterior pathway" hypothesis proposed the involvement of posterior parietal cortex. In the present study, using a gap saccade task, we investigated the role of nonhuman primate's lateral intraparietal cortex (LIP) in generation of express saccades. We show that roughly half of recorded LIP neurons were modulated during the gap interval. Moreover, a group of neurons with persistent activity in a memory-guided saccade task enhanced their activity during express saccades relative to that during regular saccades. After reducing the target's certainty by increasing the potential target locations, neuronal activity remained in the similar level during express saccades but markedly reduced during regular saccades that correlated with the increase of saccadic reaction time in the regular saccade. Our results suggest that area LIP is directly involved in generating saccades in express mode.

Attention network impairments in patients with focal frontal or parietal lesions

Recently, research on attention has focused on 3 networks that are linked to separate brain regions, i.e. orienting, alerting, and executive control. The attention network test (ANT) is one of the methods to measure the three attention functions. However, neuropsychological investigations have not examined the anatomical disassociation of different attention networks with the same task. We compared the efficiencies of the 3 networks between brain-damaged patients (27 frontal lesions, 20 temporal lesions, and 21 parietal lesions) and healthy controls (N=58) with ANT. Comparing the brain damaged group with the normal controls, a reduced efficiency of the executive network was found in patients with frontal lobe and parietal lobe injuries, and there was also a deficit in the orienting network in patients with parietal lobe injuries. Analysis of lateralization indicated the right hemisphere superiority to the alerting system. The present study found that the three attentional networks were selectively impaired following brain damage which affected different areas in the brain.

Chronic smoking, but not acute nicotine administration, modulates neural correlates of working memory

RATIONALE

Beyond the amelioration of deprivation-induced impairments, and in contrast to effects on attentional processes, the cognitive-enhancing properties of nicotine on working memory (WM) operations remain unclear.

OBJECTIVES

In an effort to elucidate potential enhancing effects, we explored the impact of transdermal nicotine on neural functioning in minimally deprived smokers and, in addition, assessed differences between smokers and non-smokers using a mixed block/event-related fMRI design that attempted to isolate specific central executive operations (attentional switch events) within general WM function (task blocks).

METHODS

In task blocks, participants performed a continuous counting paradigm that required the simultaneous maintenance of, and frequent switching of attentional focus between, two running tallies in WM on some trials. Cigarette smokers (n = 30) were scanned twice, once each with a nicotine and placebo patch, while non-smokers (n = 27) were scanned twice with no patch.

RESULTS

Across both groups, task blocks were associated with bilateral activation, notably in medial and lateral prefrontal cortex (PFC), anterior insula, and parietal regions, whereas individual attentional switch trials were associated with activation in a similar, but predominantly left-lateralized network. Within the smoker group, although nicotine increased heart rate, altered performance and mood, and reduced tobacco cravings, no acute drug (state-like) effect on brain activity was detected for either the task or switch effects. However, relative to non-smokers, smokers showed greater tonic activation in medial superior frontal cortex, right anterior insula, and bilateral anterior PFC throughout task blocks (trait-like effect).

CONCLUSIONS

These data suggest smokers require recruitment of additional WM and supervisory control operations during task performance.

Cortex and memory: emergence of a new paradigm

Converging evidence from humans and nonhuman primates is obliging us to abandon conventional models in favor of a radically different, distributed-network paradigm of cortical memory. Central to the new paradigm is the concept of memory network or cognit--that is, a memory or an item of knowledge defined by a pattern of connections between neuron populations associated by experience. Cognits are hierarchically organized in terms of semantic abstraction and complexity. Complex cognits link neurons in noncontiguous cortical areas of prefrontal and posterior association cortex. Cognits overlap and interconnect profusely, even across hierarchical levels (heterarchically), whereby a neuron can be part of many memory networks and thus many memories or items of knowledge.

Asymmetric connectivity reduction and its relationship to "HAROLD" in aging brain

Hemispheric asymmetry reduction in older adults (HAROLD) has been frequently reported in studies of functional brain aging. It is commonly considered to be a plastic brain reorganization that provides compensation for declining unilateral neural efficiency. However, plastic functional alterations may also be associated with neural connectivity changes. Using activation and resting state functional magnetic resonance imaging (fMRI) as well as diffusion tensor imaging (DTI), we examined whether functional and structural connectivity related to prefrontal working memory function is asymmetrically reduced in the two hemispheres of the aging brain; and if yes, whether these asymmetric connectivity declines are correlated with asymmetry reduction in functional activation. With regions of interests defined by verbal working memory activations, it is revealed that although neural connectivity is generally reduced in the aging brain, prefrontal-parietal resting functional connectivity is better preserved in the left hemisphere while prefrontal DTI fiber pathways are better preserved in the right hemisphere. In addition, the laterality change of the functional activation is negatively correlated with that of the resting connectivity and positively correlated with that of the structural connectivity. These results reveal additional aspects of the neuronal alterations of aging and suggest a link between asymmetric connectivity reduction and HAROLD.

Attentional set-shifting ability in first-episode and established schizophrenia: Relationship to working memory

Patients with established schizophrenia perform poorly on attentional set-shifting tasks, due to a failure of inhibitory control and/or perseverative errors. However, attentional set-shifting is also dependent on working memory capacity, which is additionally impaired in schizophrenia. No studies in first-episode psychosis have specifically examined the contribution of working memory to set-shifting ability in schizophrenia. We investigated 48 first-episode schizophreniform psychosis/schizophrenia (FE) and 40 chronic schizophrenia (CHR) patients, compared to 67 comparable healthy subjects (CTL). All subjects were assessed using the CANTAB 'attentional set-shifting (IDED)' and 'spatial working memory (SWM)' tasks. Both FE and CHR made significantly greater errors on the SWM task (p< or =0.001). Compared with CTL, CHR was more likely to fail at intra-dimensional (p<0.05) and extra-dimensional (p<0.01) shifting and reversal stages of IDED; CHR required significantly greater trials to reach criterion, which was not explained by deficits in SWM (p<0.001). FE did not differ from CTL on IDED level reached. However, FE required significantly more trials (p=0.001); this was no longer significant after controlling for SWM deficits (p>0.05). Given that the capacity to be flexible and shift attentional set is intact only at the early stages of illness, 'neurodegenerative' processes may explain the more severe deficits in chronic schizophrenia. In contrast, deficits in SWM identified at all stages of schizophrenia may reflect incomplete maturation prior to illness onset ('neurodevelopmental arrest'). Longitudinal studies assessing these cognitive functions from illness onset or in prepsychotic individuals are required.

An MRI study of age-related white and gray matter volume changes in the rhesus monkey

We applied the automated MRI segmentation technique Template Driven Segmentation (TDS) to dual-echo spin echo (DE SE) images of eight young (5-12 years), six middle-aged (16-19 years) and eight old (24-30 years) rhesus monkeys. We analyzed standardized mean volumes for 18 anatomically defined regions of interest (ROI's) and found an overall decrease from young to old age in the total forebrain (5.01%), forebrain parenchyma (5.24%), forebrain white matter (11.53%), forebrain gray matter (2.08%), caudate nucleus (11.79%) and globus pallidus (18.26%). Corresponding behavioral data for five of the young, five of the middle-aged and seven of the old subjects on the Delayed Non-matching to Sample (DNMS) task, the Delayed-recognition Span Task (DRST) and the Cognitive Impairment Index (CII) were also analyzed. We found that none of the cognitive measures were related to ROI volume changes in our sample size of monkeys.

Shifting set about task switching: behavioral and neural evidence for distinct forms of cognitive flexibility

Task switching is an important aspect of cognitive control and understanding its underlying mechanisms is the focus of considerable research. In this paper, we contrast two different kinds of task switching paradigms and provide evidence that different cognitive mechanisms underlie switching behavior depending on whether the switch is between sets of rules (rule switch) or sets of features presented simultaneously (perceptual switch). In two experiments, we demonstrate that behavioral effects (Experiment 1) and neural recruitment (Experiment 2) vary with the type of switch performed. While perceptual switch costs occurred when the alternative feature set was physically present, rule switch costs were observed even in their absence. Rule switching was also characterized by larger target repetition effects and by greater engagement of the dorsolateral prefrontal cortex. In contrast, perceptual switching was associated with greater recruitment of the parietal cortex. These results provide strong evidence for multiple forms of switching and suggest the limitations of generalizing results across shift types.

Flexible cognitive control: Effects of individual differences and brief practice on a complex cognitive task

Brain activations underlying cognitive processes are subject to modulation as a result of increasing cognitive demands, individual differences, and practice. The present study investigated these modulatory effects in a cognitive control task which required inhibition of prepotent responses based on the contents of working memory (WM) and which enabled a novel dissociation of item-specific and task-skill effects resulting from brief practice. Distinct responses in areas underlying WM and inhibitory control in the absence of behavioral changes reflected different effects of item repetition and general task practice on tonic working memory and phasic inhibitory processes. Item repetition was associated with decreases in both unique and common areas subserving WM and inhibitory control. In contrast, general task practice was reflected in decreases in the level of tonic WM activity required to maintain a consistently high level of task performance but increased activity in a number of core inhibitory regions including dorsolateral and inferior PFC and inferior parietal cortex. Furthermore, both practice and individual differences in task performance were associated with the ability to modulate and maintain activity in frontostriatal areas mediating attentional control, suggesting that the areas that differ between individuals can be modulated by practice within an individual. These results raise the possibility that a fundamental human ability, reflexive cognitive control, is amenable to practice.

Investigating principles of human brain function underlying working memory: What insights from schizophrenia?

Working memory dysfunction is a core component of schizophrenia, which likely contributes substantially to the pervasive and profound cognitive deficits observed in patients with this illness. Developments in functional imaging have facilitated the investigation of the neural basis of these cognitive deficits. A strong tradition within neuropsychology has been that circumscribed lesions provide observations which constrain theoretical models, and generate testable predictions on the basis of observed relationships between structural abnormalities and behavioral dysfunction. In this article, the extent to which the neuropsychological tradition can be applied to neuropsychiatry to advance understanding of the biological basis of working memory is addressed. Empirical studies in schizophrenia research are reviewed in relation to principles of normal brain function sub-serving working memory: the functional role of the lateral prefrontal cortex, physiological response capacity constraints, inter-regional functional integration, and compensatory adaptations. However, complex heterogeneous psychiatric disorders such as schizophrenia cannot be considered akin to a pure lesion model, and there are considerable methodological challenges in interpreting disruptions of working memory in psychiatric conditions, resulting from clinical, treatment and performance related confounds. The increasing use of psychopharmacological models of disease in healthy human subjects is therefore considered as an attempt to address, or to some extent circumvent these issues.

Attention shift in human verbal working memory: Priming contribution and dynamic brain activation

When multiple items in working memory need to be accessed and manipulated, the internal attention should switch between them and, this switching process is time consuming. However, it is not clear how much of this switching cost is due to the existence or absence of the stimulus identification priming. With a figure identification and counting task, we demonstrate a small but significant priming contribution to this attention-switching cost. Furthermore, through 64-channel event-related potential (ERP) recordings, we found two ERP correlates (at 280 ms and 388 ms) of this internal attention-switching function. Source localization analysis shows dynamic brain activation starts from the temporal-occipital region and finishes in the left prefrontal cortex. The occipital-prefrontal and cingulate-prefrontal co-activations were orderly observed. We discuss the present ERP results along with our previous fMRI findings and suggest a dominant role of the left prefrontal cortex associated with attention shifts in verbal working memory.

Backward inhibition in a task of switching attention within verbal working memory

Three experiments were conducted to examine the backward inhibition effect in attention switching within verbal working memory. Experiment one showed significant backward inhibition effect in a "tri-count task". Experiment two suggested that the effect was not due to a perceptual inhibition on the previously presented figure. Experiment three excluded the sequential expectancy explanation for this inhibition effect. Our results suggest that attention switching between working memory items is accompanied by inhibition of the previously attended working memory item. The findings are discussed in respect to the account of the executive function.

A special role for numbers in working memory? An fMRI study

Although numbers carry averbal semantics (i.e., magnitude), they are often utilized in verbal Working Memory (vWM) tasks. However, vWM is thought to rely on a purely phonological code. Here, we tested the influence of (a) averbal semantics and (b) different tasks on performance in a vWM context by examining stimulus and task-specific variation of activity in the horizontal parts of the intraparietal sulcus (hIPS). The hIPS has previously been shown to subserve magnitude processing modulated by (a) specific stimuli and (b) specific tasks. Two variants of an n-back paradigm (comparison and identity match tasks) utilizing letters and numbers as stimulus material at different levels of vWM load were administered in 16 participants. Behavioral and functional imaging data reveal stimulus-specific modulation of activity in the hIPS suggesting a semantic influence of numbers. In the identity match task, numbers induced additional hIPS activation compared to letters while letters never induced additional hIPS activation when compared to numbers. Letters as compared to numbers only induced additional hIPS activation in the comparison task. These results question the assumption of a purely phonological code in vWM because hIPS activation subserving magnitude processing is modulated by stimulus semantics and task demands.

Age-dependent brain activation during forward and backward digit recall revealed by fMRI

In this study, brain activation associated with forward and backward digit recall was examined in healthy old and young adults using functional MRI. A number of areas were activated during the recall. In young adults, greater activation was found in the left prefrontal cortex (BA9) and the left occipital visual cortex during backward digit recall than forward digit recall. In contrast, the activation in the right inferior frontal gyrus (BA 44/45) was more extensive in forward digit recall than in backward digit recall. In older adults, backward recall generated stronger activation than forward recall in most areas, including the frontal, the parietal, the occipital, and the temporal cortices. In the backward recall condition, the right inferior frontal gyrus (BA44/45) showed more activation in the old group than in the young group. These results suggest that different neural mechanisms may be involved in forward and backward digit recall and brain functions associated with these two types of recall are differentially affected by aging.

Raloxifene exposure enhances brain activation during memory performance in healthy elderly males; its possible relevance to behavior

Raloxifene is a selective estrogen receptor modulator (SERM) that is prescribed in females only, but its use in male subjects is increasingly considered. With a growing number of patients having potential benefit from raloxifene, the need for an assessment of its effects on brain function is growing. Effects of estrogens on brain function are very subtle and difficult to detect by neuropsychological assessment. Functional imaging techniques, however, have been relatively successful in detecting such changes. This study used functional magnetic resonance imaging (fMRI) to examine effects of raloxifene treatment on memory function. Healthy elderly males (n = 28; mean age 63.6 years, SD 2.4) were scanned during performance on a face encoding paradigm. Scans were made at baseline and after 3 months of treatment with either raloxifene (n = 14) or placebo (n = 14). Treatment effects were analyzed using mixed-effects statistical analysis (FSL). Activation during task performance involved bilateral parietal and prefrontal areas, anterior cingulate gyrus, and inferior prefrontal, occipital, and mediotemporal areas bilaterally. When compared to placebo, raloxifene treatment significantly enhanced activation in these structures (Z > 3.1), except for mediotemporal areas. Task performance accuracy diminished in the placebo group (P = 0.02), but remained constant in the raloxifene group (P = 0.60). In conclusion, raloxifene treatment enhanced brain activation in areas spanning a number of different cognitive domains, suggesting an effect on cortical arousal. Such effects may translate into small effects on behavior, including effects on attention and working memory performance, executive functions, verbal skills, and episodic memory. Further neuropsychological assessment is necessary to test the validity of these predictions.

Lateralized Attentional Functions of Cortical Cholinergic Inputs

The integrity of the cortical cholinergic input system is necessary for attention performance. This experiment tested hypotheses concerning the lateralized contributions of cortical cholinergic inputs to attention performance by assessing the effects of unilateral lesions of basal forebrain cholinergic neurons on sustained attention performance. Loss of right-hemispheric cortical cholinergic inputs impaired the rats' ability to detect signals but did not affect nonsignal trial performance. Conversely, loss of left-hemispheric cortical cholinergic inputs increased the number of false alarms in nonsignal trials. These data correspond with hypotheses about the mediation of detection processes primarily by right-hemispheric circuits and executive aspects of attention performance by left-hemispheric systems. Cortical cholinergic inputs represent a major component of the brain's lateralized attention systems.