Gender differences in the functional organization of the brain for working memory

Sex differences in the medial temporal lobe during encoding and recognition of pseudowords and abstract designs

Sex differences in various cognitive abilities have been demonstrated in terms of performance differentials and, more recently, in differences in activation patterns during fMRI. Hemispheric lateralization is sometimes accentuated in sex differences; e.g., women demonstrating greater activation of the left hemisphere than men during verbal tasks. We were interested in whether this phenomenon applies to memory for words and designs (i.e., material specific memory). Using analogous verbal (pseudowords) and nonverbal (abstract designs) encoding and recognition tasks completed back-to-back in a 3T scanner, we found that women tend to show exaggerated left hippocampal activation during certain stages of encoding and recognition of verbal information, compared with men. Likewise (although to a lesser extent), men showed more right hippocampal activation than women did during the abstract design learning task. These results have important implications for the generalization of fMRI memory study results, for example to clinical populations such as patients undergoing epilepsy surgery.

Sex-related memory recall and talkativeness for emotional stimuli

Recent studies have evidenced an increasing interest in sex-related brain mechanisms and cerebral lateralization subserving emotional memory, language processing, and conversational behavior. We used event-related-potentials (ERP) to examine the influence of sex and hemisphere on brain responses to emotional stimuli. Given that the P300 component of ERP is considered a cognitive neuroelectric phenomenon, we compared left and right hemisphere P300 responses to emotional stimuli in men and women. As indexed by both amplitude and latency measures, emotional stimuli elicited more robust P300 effects in the left hemisphere in women than in men, while a stronger P300 component was elicited in the right hemisphere in men compared to women. Our findings show that the variables of sex and hemisphere interacted significantly to influence the strength of the P300 component to the emotional stimuli. Emotional stimuli were also best recalled when given a long-term, incidental memory test, a fact potentially related to the differential P300 waves at encoding. Moreover, taking into account the sex-related differences in language processing and conversational behavior, in the present study we evaluated possible talkativeness differences between the two genders in the recollection of emotional stimuli. Our data showed that women used a higher number of words, compared to men, to describe both arousal and neutral stories. Moreover, the present results support the view that sex differences in lateralization may not be a general feature of language processing but may be related to the specific condition, such as the emotional content of stimuli.

The less BOLD, the wiser: support for the latent resource hypothesis after traumatic brain injury

Previous studies of the BOLD response in the injured brain have revealed neural recruitment relative to controls during working memory tasks in several brain regions, most consistently the right prefrontal cortex and anterior cingulate cortices. We previously proposed that the recruitment observed in this literature represents auxiliary support resources, and that recruitment of PFC is not abnormal or injury specific and should reduce as novelty and challenge decrease. The current study directly tests this hypothesis in the context of practice of a working memory task. It was hypothesized that individuals with brain injury would demonstrate recruitment of previously indicated regions, behavioral improvement following task practice, and a reduction in the BOLD signal in recruited regions after practice. Individuals with traumatic brain injury and healthy controls performed the n-back during fMRI acquisition, practiced each task out of the scanner, and returned to the scanner for additional fMRI n-back acquisition. Statistical parametric maps demonstrated a number of regions of recruitment in the 1-back in individuals with brain injury and a number of corresponding regions of reduced activation in individuals with brain injury following practice in both the 1-back and 2-back. Regions of interest demonstrated reduced activation following practice, including the anterior cingulate and right prefrontal cortices. Individuals with brain injury demonstrated modest behavioral improvements following practice. These findings suggest that neural recruitment in brain injury does not represent reorganization but a natural extension of latent mechanisms that engage transiently and are contingent upon cerebral challenge.

Examining working memory task acquisition in a disrupted neural network

There is mounting literature that examines brain activation during tasks of working memory in individuals with neurological disorders such as traumatic brain injury. These studies represent a foundation for understanding the functional brain changes that occur after moderate and severe traumatic brain injury, but the focus on topographical brain-'activation' differences ignores potential alterations in how nodes communicate within a distributed neural network. The present study makes use of the most recently developed connectivity modelling (extended-unified structural equation model) to examine performance during a well-established working-memory task (the n-back) in individuals sustaining moderate and severe traumatic brain injury. The goal is to use the findings observed in topographical activation analysis as the basis for second-level effective connectivity modelling. Findings reveal important between-group differences in within-hemisphere connectivity during task acquisition, with the control sample demonstrating rapid within-left hemisphere connectivity increases and the traumatic brain injury sample demonstrating consistently elevated within-right hemisphere connectivity. These findings also point to important maturational effects from 'early' to 'late' during task performance, including diminished right prefrontal cortex involvement and an anterior to posterior shift in connectivity with increased task exposure. We anticipate that this approach to functional imaging data analysis represents an important future direction for understanding how neural plasticity is expressed in brain disorders.

Sex differences in β-amyloid accumulation in 3xTg-AD mice: role of neonatal sex steroid hormone exposure

The risk of Alzheimer's disease (AD) is higher in women than in men, a sex difference that likely results from the effects of sex steroid hormones. To investigate this relationship, we first compared progression of β-amyloid (Aβ) pathology in male and female triple transgenic (3xTg-AD) mice. We found that female 3xTg-AD mice exhibit significantly greater Aβ burden and larger behavioral deficits than age-matched males. Next, we evaluated how the organizational effects of sex steroid hormones during postnatal development may affect adult vulnerability to Aβ pathology. We observed that male 3xTg-AD mice demasculinized during early development exhibit significantly increased Aβ accumulation in adulthood. In contrast, female mice defeminized during early development exhibit a more male-like pattern of Aβ pathology in adulthood. Taken together, these results demonstrate significant sex differences in pathology in 3xTg-AD mice and suggest that these differences may be mediated by organizational actions of sex steroid hormones during development.

An fMRI study of functional abnormalities in the verbal working memory system and the relationship to clinical symptoms in chronic schizophrenia

There has been evidence for functional abnormalities of the verbal working memory system in schizophrenia. Verbal working memory crucially involves the interplay between the anterior and posterior language systems, and previous studies have shown converging evidence for abnormalities in the posterior language system in schizophrenia. In this functional magnetic resonance imaging study, we measured cortical activity in chronic schizophrenic patients and matched healthy controls during auditory and visual verbal working memory tasks. We employed 1) regional analyses specifically targeting the posterior language system and 2) analyses of functional connectivity between anterior and posterior language regions. We performed these analyses separately for each memory stage and modality. In the regional analyses, the left sylvian-parietal-temporal (Spt) area consistently showed reduced activation during encoding and retrieval stages in schizophrenia. Magnitudes of activation in the left posterior superior temporal sulcus were correlated with the severity of delusions at every memory stage. Functional connectivity analyses revealed reduced connectivity between the left Spt and the anterior insula during the encoding of auditory words. In addition, the connectivity strength was correlated with the severity of auditory hallucinations. These findings identify abnormal components in the verbal working memory system and illustrate their possible overlap with the mechanisms of core schizophrenic symptoms.

Sexual dimorphism of spatial working memory profiles in schizophrenia

INTRODUCTION

The aim of the present study was to compare spatial working memory performance of females and males schizophrenia patients to verify whether the sexual dimorphism of spatial abilities present in the general population is found also in schizophrenia.

METHODS

We analysed different types of errors committed by each gender on the spatial working memory test of the Cambridge Neuropsychological Test Automated Battery to determine potential differences between them.

RESULTS

Despite the lack of difference in the number of errors between men and women, different profiles of errors were associated with the strategy used according to gender. The men's strategy was better compared to women. Specifically, for women strategy score correlated positively with searches in previously visited boxes, whereas for men it correlated with both previously visited boxes and never visited ones. However, men's strategy is more impaired by the number of revisits in boxes in which tokens have previously been found than female's one.

CONCLUSIONS

These results suggested impaired either central executive and/or visuospatial sketchpad of working memory in patients with schizophrenia. We demonstrated also that the worsening of strategy in men is principally due to central executive deficits compared to women with schizophrenia. The study of sex differences in cognitive performances could help in delineating partially different endophenotypes of schizophrenia in men and women.

Cerebral hemodynamic lateralization during memory tasks as assessed by functional transcranial Doppler (fTCD) sonography: effects of gender and healthy aging

INTRODUCTION

Previous neuropsychological, lesional and functional imaging studies deal with the lateralization of memory processes, suggesting that they could be determined by the stage of processing (encoding vs retrieval) or by content (verbal vs non-verbal stimuli). The aims of the present study were: 1) to investigate if tasks that can be carried out using different strategies depending on the verbalizability of the material induce a lateralization of the mean cerebral blood flow velocity (mCBFV) in the middle cerebral arteries (MCAs), as monitored by a functional transcranial Doppler (fTCD); 2) to evaluate if these patterns of cerebral activation differ in relation to age, gender and task performance.

METHOD

Using TCD bilateral monitoring, we recorded mCBFV variations in 35 male and 35 female healthy, right-handed volunteers, classified as "young" (age range 21-40 years, n=35) or "old"(age range 41-60 years, n=35), performing four different cognitive tasks: encoding and recognition of Geometric Figures (GF), encoding and recall of Object Localization (OL) on a picture, encoding of a verbal Room Description (RD) and Arithmetic Skill (AS).

RESULTS

We found a significant right lateralization for the OL recall phase, and a significant left lateralization for RD and AS. When we took into consideration gender, age and performance, there was a strong effect of age on both OL encoding and recall phase, with significant right lateralization in young volunteers not seen in the older ones. No difference in gender was detected. We found a gender×performance interaction for RD, with poor performance females showing significant left lateralization.

CONCLUSIONS

According to our findings, hemispheric lateralization during memory encoding is material specific in both men and women, depending on the verbalizability of the material. mCBFV right lateralization during scene encoding and recall appears lost in older people, suggesting that healthy elderly could take advantage of mixed verbal and non-verbal strategies.

Vibrotactile Feedback for Information Delivery in the Vehicle

As technology advances, more functions have been, and continue to be added to the vehicle, resulting in increased needs for improved user interfaces. In this paper, we investigate the feasibility of using vibrotactile feedback for in-vehicle information delivery. First, we measured the spectral characteristics of ambient vibrations in a vehicle, and designed clearly distinguishable sinusoidal vibrations. We further selected via dissimilarity rating the four sets of sinusoidal vibrations which had three to six vibrations. Second, we evaluated the learnability of the vibration sets when associated with common menu items of a Driver Information System (DIS). We also replaced the two most confused sinusoidal vibrations with patterned messages, and assessed the degree of learnability improvement. Finally, we evaluated the extent to which participants could select a desired function in a DIS via vibrotactile messages while simultaneously performing a driving-like primary task with higher priority. The results demonstrated high potential for vibrotactile messages to be effectively used for the communicative transfer of in-vehicle system information.

No gender differences in brain activation during the N-back task: an fMRI study in healthy individuals

Gender differences have been well established in verbal and spatial abilities but few studies have examined if these differences also extend into the domain of working memory in terms of behavioural differences and brain activation. The conclusions that can be drawn from these studies are not clear cut but suggest that even though gender differences might not be apparent from behavioural measures, the underlying neural substrate associated with working memory might be different in men and women. Previous research suggests activation in a network of frontal and parietal regions during working memory tasks. This study aimed to investigate gender differences in patterns of brain activation during a verbal version of the N-back working memory task, which incorporates the effects of increased demands on working memory. A total of 50 healthy subjects, aged 18 to 58 years, that were equally split by gender were recruited matched for age, levels of education and ethnicity. All subjects underwent functional magnetic resonance imaging. We found that men and women performed equally well in terms of accuracy and response times, while using similar brain regions to the same degree. Our observations indicate that verbal working memory is not affected by gender at the behavioural or neural level, and support the findings of a recent meta-analysis by Hyde ([ 2005]: Sex Roles 53:717-725) that gender differences are generally smaller than intra-gender differences in many cognitive domains.

Sex-dependent age modulation of frontostriatal and temporo-parietal activation during cognitive control

Developmental functional imaging studies of cognitive control show progressive age-related increase in task-relevant fronto-striatal activation in male development from childhood to adulthood. Little is known, however, about how gender affects this functional development. In this study, we used event related functional magnetic resonance imaging to examine effects of sex, age, and their interaction on brain activation during attentional switching and interference inhibition, in 63 male and female adolescents and adults, aged 13 to 38. Linear age correlations were observed across all subjects in task-specific frontal, striatal and temporo-parietal activation. Gender analysis revealed increased activation in females relative to males in fronto-striatal areas during the Switch task, and laterality effects in the Simon task, with females showing increased left inferior prefrontal and temporal activation, and males showing increased right inferior prefrontal and parietal activation. Increased prefrontal activation clusters in females and increased parietal activation clusters in males furthermore overlapped with clusters that were age-correlated across the whole group, potentially reflecting more mature prefrontal brain activation patterns for females, and more mature parietal activation patterns for males. Gender by age interactions further supported this dissociation, revealing exclusive female-specific age correlations in inferior and medial prefrontal brain regions during both tasks, and exclusive male-specific age correlations in superior parietal (Switch task) and temporal regions (Simon task). These findings show increased recruitment of age-correlated prefrontal activation in females, and of age-correlated parietal activation in males, during tasks of cognitive control. Gender differences in frontal and parietal recruitment may thus be related to gender differences in the neurofunctional maturation of these brain regions.

Gender Differences in Cognitive Control: an Extended Investigation of the Stop Signal Task

Men and women show important differences in clinical conditions in which deficits in cognitive control are implicated. We used functional magnetic resonance imaging to examine gender differences in the neural processes of cognitive control during a stop-signal task. We observed greater activation in men, compared to women, in a wide array of cortical and sub-cortical areas, during stop success (SS) as compared to stop error (SE). Conversely, women showed greater regional brain activation during SE > SS, compared to men. Furthermore, compared to women, men engaged the right inferior parietal lobule to a greater extent during post-SE go compared to post-go go trials. Women engaged greater posterior cingulate cortical activation than men during post-SS slowing in go trial reaction time (RT) but did not differ during post-SE slowing in go trial RT. These findings extended our previous results of gender differences in regional brain activation during response inhibition. The results may have clinical implications by, for instance, helping initiate studies to understand why women are more vulnerable to depression while men are more vulnerable to impulse control disorders.

Do sex differences affect prefrontal cortex associated cognition in schizophrenia?

Cognitive deficits in schizophrenia, especially those related to prefrontal cortex (PFC) functions, influence functional outcome. There is evidence for sex differences in cognition in schizophrenia, but the results in the literature are still controversial.

OBJECTIVE

This study evaluated different modalities of working memory (WM) and executive control (EC), functions that are both associated with the PFC, between sexes in schizophrenic patients and controls.

METHODS

We used a battery of neuropsychological tests for assessing auditory, spatial, and visual-matching WM and used a dual task for assessing EC. The study included 50 inpatients (25 female) partially remitted and taking atypical neuroleptics, as well as 40 controls (20 female) matched for age and education.

RESULTS

Significant sex differences were found in the dual task; female patients detected fewer correct trials than male patients and controls did. Moreover, female patients performed significantly worse in the single visual subtest of the dual task. For the controls, no sex differences were found. Males showed higher positive symptoms than females, but no other differences in psychopathology, disease characteristics, or extrapyramidal symptoms were found between sexes.

CONCLUSION

The present study shows an absence of sex differences in WM in healthy subjects and in patients with schizophrenia. However, in the dual task and in the single visual subtest, female patients performed worse than males. This finding suggests that in contrast to males, nonacute female inpatients show an underlying attentional deficit that may contribute to impairment in higher-order functions such as EC.

Sex Differences in Working Memory

In two separate studies, sex differences in modal-specific elements of working memory were investigated by utilizing words and pictures as stimuli. Groups of men and women performed a free-recall task of words or pictures in which 20 items were presented concurrently and the number of correct items recalled was measured. Following stimulus presentation, half of the participants were presented a verbal-based distraction task. On the verbal working-memory task, performance of men and women was not significantly different in the no-distraction condition. However, in the distraction condition, women's recall was significantly lower than their performance in the no-distraction condition and men's performance in the distraction condition. These findings are consistent with previous research and point to sex differences in cognitive ability putatively resulting from functional neuroanatomical dissimilarities. On the visual working-memory task, women showed significantly greater recall than men. These findings are inconsistent with previous research and underscore the need for further research.

Sex differences in neural processing of language among children

Why females generally perform better on language tasks than males is unknown. Sex differences were here identified in children (ages 9-15) across two linguistic tasks for words presented in two modalities. Bilateral activation in the inferior frontal and superior temporal gyri and activation in the left fusiform gyrus of girls was greater than in boys. Activation in the left inferior frontal and fusiform regions of girls was also correlated with linguistic accuracy irregardless of stimulus modality, whereas correlation with performance accuracy in boys depended on the modality of word presentation (either in visual or auditory association cortex). This pattern suggests that girls rely on a supramodal language network, whereas boys process visual and auditory words differently. Activation in the left fusiform region was additionally correlated with performance on standardized language tests in which girls performed better, additional evidence of its role in early sex differences for language.

Mapping the relationship between cortical convolution and intelligence: effects of gender

The pronounced convolution of the human cortex may be a morphological substrate that supports some of our species' most distinctive cognitive abilities. Therefore, individual intelligence within humans might be modulated by the degree of folding in certain cortical regions. We applied advanced methods to analyze cortical convolution at high spatial resolution and correlated those measurements with intelligence quotients. Within a large sample of healthy adult subjects (n = 65), we detected the most prominent correlations in the left medial hemisphere. More specifically, intelligence scores were positively associated with the degree of folding in the temporo-occipital lobe, particularly in the outermost section of the posterior cingulate gyrus (retrosplenial areas). Thus, this region might be an important contributor toward individual intelligence, either via modulating pathways to (pre)frontal regions or by serving as a location for the convergence of information. Prominent gender differences within the right frontal cortex were observed; females showed uncorrected significant positive correlations and males showed a nonsignificant trend toward negative correlations. It is possible that formerly described gender differences in regional convolution are associated with differences in the underlying architecture. This might lead to the development of sexually dimorphic information processing strategies and affect the relationship between intelligence and cortical convolution.

Sex differences in sensory gating of the thalamus during auditory interference of visual attention tasks

Men and women have different cognitive abilities that might reflect sex-specific neural organization. Here we studied sex effects on brain function using functional magnetic resonance imaging (fMRI) with variable acoustic noise (AN) to modulate the cognitive challenge and enhance the sensitivity for the detection of sex differences in brain activation. During the performance of a visual attention (VA) task that requires the tracking of multiple moving objects and has graded levels of difficulty, women (n=15) but not men (n=13) had shorter reaction times for "Loud" than for "Quiet" scans. Men activated more than women in the superior prefrontal and occipital cortices and the anterior thalamus. The latent connectivity of the prefrontal cortex was higher with the anterior thalamus but lower with the auditory cortex for men than for women. Increases in activation with visual attention load were larger for men than for women in the superior parietal and auditory cortices. Increased AN reduced brain activation in the parietal cortex and the anterior thalamus for men but not for women. Together, these sex-specific differences in brain activation during the VA task, at different cognitive and acoustic levels suggest differences in auditory gating of the thalamus for men and women.

Assessing the influence of scanner background noise on auditory processing. I. An fMRI study comparing three experimental designs with varying degrees of scanner noise

We compared two experimental designs aimed at minimizing the influence of scanner background noise (SBN) on functional MRI (fMRI) of auditory processes with one conventional fMRI design. Ten subjects listened to a series of four one-syllable words and had to decide whether two of the words were identical. This was contrasted with a no-stimulus control condition. All three experimental designs had a duration of approximately 17 min: 1) a behavior interleaved gradients (BIG; Eden et al. [1999] J Magn Reson Imaging 41:13-20) design (repetition time, TR, = 6 s), where stimuli were presented during the SBN-free periods between clustered volume acquisitions (CVA); 2) a sparse temporal sampling technique (STsamp; e.g., Gaab et al., [2003] Neuroimage 19:1417-1426) acquiring only one set of slices following each of the stimulations with a 16-s TR and jittered delay times between stimulus offset and image acquisition; and 3) an event-related design with continuous scanning (ERcont) using the stimulation design of STsamp but with a 2-s TR. The results demonstrated increased signal within Heschl's gyrus for the STsamp and BIG-CVA design in comparison to ERcont as well as differences in the overall functional anatomy among the designs. The possibility to obtain a time course of activation as well as the full recovery of the stimulus- and SBN-induced hemodynamic response function signal and lack of signal suppression from SBN during the STsamp design makes this technique a powerful approach for conducting auditory experiments using fMRI. Practical strengths and limitations of the three auditory acquisition paradigms are discussed.

Learning in a task of complex auditory streaming and identification

Adult humans were studied for improvements in their ability to segregate natural whole speech in background noise, in 6 test sessions spaced with a very wide range of inter-session interval (ISI) ranging from minutes to weeks apart so as to examine the effect of this parameter on initial (early) and late components of perceptual learning. Improvements were found even with spacings of 3 weeks between the punctate task sessions. All subjects showed similar total learning amounts but there were sex- and ISI-dependent differences in learning patterns, which we indexed by dividing the overall exponentially-decreasing learning pattern into an early phase between the first two sessions and a later phase between the second and sixth sessions. Males tested at all ISIs and females tested at short (2, 5 and 15 min) and long (1-21 days) ISIs showed small amounts of early-phase learning and large amounts of late-phase learning. However, females tested at intermediate (30 min and 1h) ISIs showed only early learning, i.e., faster learning given that the total learning was the same. This sex- and ISI-specific deviant pattern could be changed to the standard pattern by interposing an overnight interruption that included sleep amongst test sessions. Thus, improvement in this complex auditory streaming and identification task can occur even with very brief and widely-spaced exposure, generally through a standard pattern of slower overall learning, but also through a sex- and ISI-specific deviant pattern of very rapid early learning which can be modulated by interposed delay unlike the standard pattern.

Neurotrophic and neuroprotective actions of estrogen: basic mechanisms and clinical implications

Estrogen is an important hormone signal that regulates multiple tissues and functions in the body. This review focuses on the neurotrophic and neuroprotective actions of estrogen in the brain, with particular emphasis on estrogen actions in the hippocampus, cerebral cortex and striatum. Sex differences in the risk, onset and severity of neurodegenerative disease such as Alzheimer's disease, Parkinson's disease and stroke are well known, and the potential role of estrogen as a neuroprotective factor is discussed in this context. The review assimilates a complex literature that spans research in humans, non-human primates and rodent animal models and attempts to contrast and compare the findings across species where possible. Current controversies regarding the Women's Health Initiative (WHI) study, its ramifications, concerns and the new studies needed to address these concerns are also addressed. Signaling mechanisms underlying estrogen-induced neuroprotection and synaptic plasticity are reviewed, including the important concepts of genomic versus nongenomic mechanisms, types of estrogen receptor involved and their subcellular targeting, and implicated downstream signaling pathways and mediators. Finally, a multicellular mode of estrogen action in the regulation of neuronal survival and neurotrophism is discussed, as are potential future directions for the field.

fMRI delineation of working memory for emotional prosody in the brain: commonalities with the lexico-semantic emotion network

Decoding emotional prosody is crucial for successful social interactions, and continuous monitoring of emotional intent via prosody requires working memory. It has been proposed by Ross and others that emotional prosody cognitions in the right hemisphere are organized in an analogous fashion to propositional language functions in the left hemisphere. This study aimed to test the applicability of this model in the context of prefrontal cortex working memory functions. BOLD response data were therefore collected during performance of two emotional working memory tasks by participants undergoing fMRI. In the prosody task, participants identified the emotion conveyed in pre-recorded sentences, and working memory load was manipulated in the style of an N-back task. In the matched lexico-semantic task, participants identified the emotion conveyed by sentence content. Block-design neuroimaging data were analyzed parametrically with SPM5. At first, working memory for emotional prosody appeared to be right-lateralized in the PFC, however, further analyses revealed that it shared much bilateral prefrontal functional neuroanatomy with working memory for lexico-semantic emotion. Supplementary separate analyses of males and females suggested that these language functions were less bilateral in females, but their inclusion did not alter the direction of laterality. It is concluded that Ross et al.'s model is not applicable to prefrontal cortex working memory functions, that evidence that working memory cannot be subdivided in prefrontal cortex according to material type is increased, and that incidental working memory demands may explain the frontal lobe involvement in emotional prosody comprehension as revealed by neuroimaging studies.

Gender differences in the cognitive control of emotion: An fMRI study

The interaction of emotion and cognition has become a topic of major interest. However, the influence of gender on the interplay between the two processes, along with its neural correlates have not been fully analysed so far. In this functional magnetic resonance imaging (fMRI) study we induced negative emotion using negative olfactory stimulation while male (n=21) and female (n=19) participants performed an n-back verbal working memory task. Based on findings indicating increased emotional reactivity in women, we expected the female participants to exhibit stronger activation in characteristically emotion-associated areas during the interaction of emotional and cognitive processing in comparison to the male participants. Both groups were found to be significantly impaired in their working memory performance by negative emotion induction. However, fMRI analysis revealed distinct differences in neuronal activation between groups. In men, cognitive performance under negative emotion induction was associated with extended activation patterns in mainly prefrontal and superior parietal regions. In women, the interaction between emotion and working memory yielded a significantly stronger response in the amygdala and the orbitofrontal cortex (OFC) compared to their male counterparts. Our data suggest that in women the interaction of verbal working memory and negative emotion is associated with relative hyperactivation in more emotion-associated areas whereas in men regions commonly regarded as important for cognition and cognitive control are activated. These results provide new insights in gender-specific cerebral mechanisms.

Working memory deficits in adults with ADHD: is there evidence for subtype differences?

BACKGROUND

Working memory performance is important for maintaining functioning in cognitive, academic and social activities. Previous research suggests there are prevalent working memory deficits in children with attention deficit hyperactivity disorder (ADHD). There is now a growing body of literature characterizing working memory functioning according to ADHD subtypes in children. The expression of working memory deficits in adults with ADHD and how they vary according to subtype, however, remains to be more fully documented.

METHODS

This study assessed differences in working memory functioning between Normal Control (NC) adults (N = 18); patients with ADHD, Combined (ADHD-CT) Type ADHD (N = 17); and ADHD, Inattentive (ADHD-IA) Type (N = 16) using subtests from the Wechsler Adult Intelligence Scale-III and Wechsler Memory Scale-III and the Paced Auditory Serial Addition Task (PASAT).

RESULTS

The ADHD groups displayed significant weaknesses in contrast to the NC group on working memory tests requiring rapid processing and active stimulus manipulation. This included the Letter-Number-Sequencing test of the Wechsler scales, PASAT omission errors and the longest sequence of consecutive correct answers on the PASAT. No overall ADHD group subtype differences emerged; however differences between the ADHD groups and the NC group varied depending on the measure and the gender of the participants. Gender differences in performance were evident on some measures of working memory, regardless of group, with males performing better than females.

CONCLUSION

In general, the data support a dimensional interpretation of working memory deficits experienced by the ADHD-CT and ADHD-IA subtypes, rather than an absolute difference between subtypes. Future studies should test the effects of processing speed and load on subtype performance and how those variables interact with gender in adults with ADHD.

Different activation patterns for working memory load and visual attention load

Attention is a basic component of cognition, and is modulated by cognitive load. We aimed to map the common network that supports attentional load across different tasks using functional magnetic resonance imaging (fMRI). Twenty-two healthy volunteers performed two sets of tasks with graded levels of cognitive load: verbal working memory (WM) and visual attention (VA) tasks. For both tasks, increased cognitive load (WM-load and VA-load) activated a common network comprising parietal and occipital cortices, thalamus, and the cerebellum, indicating that these brain regions are involved in higher level of attention. The fMRI signals in the prefrontal cortices increased with WM-load but not with VA-load, suggesting that executive function is involved for the more demanding WM tasks but not for the more difficult VA tasks. Conversely, VA tasks activated more strongly an occipito-parietal network comprising the postcentral (PostCG) and the superior occipital (SOG) gyri, suggesting complex visual processing in this network.

The effect of gender on planning: An fMRI study using the Tower of London task

Since the introduction of brain mapping, evidences of functional gender differences have been corroborating previous behavioral and neuropsychological results showing a sex-specific brain organization. We investigated gender differences in brain activation during the performance of the Tower of London (TOL) task which is a standardized test to assess executive functions. Eighteen healthy subjects (9 females and 9 males) underwent fMRI scanning while solving a series of TOL problems with different levels of difficulty. Data were analyzed by modeling both genders and difficulty task load. Task-elicited brain activations comprised a bilateral fronto-parietal network, common to both genders; within this network, females activated more than males in dorsolateral prefrontal cortex (DLPFC) and right parietal cortex, whereas males showed higher activity in precuneus. A prominent parietal activity was found at low level of difficulty while, with heavier task demand, several frontal regions and subcortical structures were recruited. Our results suggest peculiar gender strategies, with males relying more on visuospatial abilities and females on executive processing.

Gender differences in the neural correlates of response inhibition during a stop signal task

We used functional magnetic resonance imaging to examine gender differences in the neural correlates of response inhibition during a stop signal task. The task has a frequent "go" signal to set up a pre-potent response tendency and a less frequent "stop" signal for subjects to withhold their response. A contrast in brain activation was made between successful and failed inhibitions for individual subjects. We compared 20 men and 20 women matched in age and years of education and in stop signal performance, with stop success rate, post-error slowing and task-related frustration ratings as covariates. The results showed greater activation in men, compared to women, in a wide array of cortical and subcortical areas, including the globus pallidus and motor thalamus during stop signal inhibition. In contrast, no brain regions demonstrated greater activation in women, even at a lower statistical threshold. Moreover, while men activated the medial superior frontal and anterior cingulate cortices, women activated the caudate tail to mediate response inhibition. These results extended gender differences in regional brain activation to response inhibition during a cognitive motor task. Men activated the motor circuitry while women appeared to involve visual association or habit learning during stop signal performance.

Cortical trapping of alpha-[(11)C]methyl-l-tryptophan, an index of serotonin synthesis, is lower in females than males

One neural system that may exhibit gender differences is serotonin (5-HT), a neurotransmitter implicated in the regulation of mood, cognitive processes, and impulse-control. However, most of the available evidence of gender-related differences in this system has been indirect and at times contradictory. The objective of the present study was to follow up on preliminary evidence that there are gender differences in brain regional 5-HT synthesis, as measured by trapping of alpha-[(11)C]methyl-l-tryptophan (alpha-[(11)C]MTrp). Sixty-minute dynamic scans were performed in healthy volunteers, 28 women and 31 men. Functional images of the brain trapping constant, used as a proxy for 5-HT synthesis, which correlate in the rat brain with tryptophan's conversion into 5-HT, were transferred to the standardized 3D space. The voxel based comparison was performed by Statistical Parametric Mapping with proportional normalization. There was lower normalized alpha-[(11)C]MTrp trapping in females than males throughout much of the cerebral cortex, including the left middle frontal gyrus, the bilateral inferior frontal gyrus, the bilateral precentral gyrus, the left supramarginal gyrus, the bilateral inferior parietal lobule, the left superior temporal gyrus, the bilateral posterior cingulate gyrus, and the bilateral precuneus. There were no regions in which the normalized trapping was significantly higher in females than in males. Gender differences in sub-cortical sites were not found. Women, compared to men, may have lower rates of this tracer trapping, used as a proxy for 5-HT synthesis, throughout much of the cerebral cortex which is likely related to differences in 5-HT synthesis because relative differences in the normalized trapping should be the same as those in 5-HT synthesis. These differences may be related, at least in part, to previously suggested gender differences in affect, cognitive processes, and susceptibility to 5-HT-related neuropsychiatric and neurological disorders.

Sex influences on material-sensitive functional lateralization in working and episodic memory: Men and women are not all that different

Research investigating the effects of sex on the lateralization of language functions has produced mixed results to date, with some studies finding sex differences and others not [Shaywitz, B.A., Shaywitz, S.E., Pugh, K.R., Constable, R.T., Skudlarski, P., Fulbright, R.K., Bronen, R.A., Fletcher, J.M., Shankweiler, D.P., Katz, L., et al., 1995. Sex differences in the functional organization of the brain for language. Nature 373 607-609.; Frost, J.A., Binder, J.R., Springer, J.A., Hammeke, T.A., Bellgowan, P.S., Rao, S.M., Cox, R.W., 1999. Language processing is strongly left lateralized in both sexes. Evidence from functional MRI. Brain 122 (Pt 2) 199-208.]. Further, few studies have evaluated how any such sex effects extend to tasks involving cognitive functions that may utilize language processes such as working and episodic memory. This study examined sex difference in material-sensitive functional activation (using fMRI) in working memory and episodic memory that included either words and faces. We performed these analyses on two large groups of healthy subjects with the goal of attempting to replicate results across two independent data sets. The results indicated that both males and females showed strong and consistent evidence for material-sensitive lateralization for both working and episodic memory, such that word tasks resulted in greater left-sided activation and face tasks resulted in greater right-sided activation. Further, few of the sex differences in regions showing material specificity effects in at least one gender replicated across studies, providing little evidence for any differences in lateralization patterns between the sexes. In conclusion, our data suggest that males and females show a similar pattern of lateralized activation to material type during working memory and recognition tasks.

Why sex matters for neuroscience

A rapidly burgeoning literature documents copious sex influences on brain anatomy, chemistry and function. This article highlights some of the more intriguing recent discoveries and their implications. Consideration of the effects of sex can help to explain seemingly contradictory findings. Research into sex influences is mandatory to fully understand a host of brain disorders with sex differences in their incidence and/or nature. The striking quantity and diversity of sex-related influences on brain function indicate that the still widespread assumption that sex influences are negligible cannot be justified, and probably retards progress in our field.

The human immunodeficiency virus reduces network capacity: acoustic noise effect

OBJECTIVE

Increased acoustic noise (AN) during working memory leads to increased brain activation in healthy individuals and may have greater impact in human immunodeficiency virus (HIV) patients.

RESULTS

Compared with control subjects, HIV patients showed reduced AN activation and lower neuronal marker N-acetylaspartate in prefrontal and parietal cortices. Competing use of the working memory network between AN and cognitive load showed lower dynamic range of the hemodynamic responses in prefrontal and parietal cortices in HIV patients.

INTERPRETATION

These findings suggest that reduced reserve capacity of the working memory network in HIV patients and additional stress (eg, AN) might exhaust the impaired network for more demanding tasks.

Males and females differ in brain activation during cognitive tasks

To examine the effect of gender on regional brain activity, we utilized functional magnetic resonance imaging (fMRI) during a motor task and three cognitive tasks; a word generation task, a spatial attention task, and a working memory task in healthy male (n = 23) and female (n = 10) volunteers. Functional data were examined for group differences both in the number of pixels activated, and the blood-oxygen-level-dependent (BOLD) magnitude during each task. Males had a significantly greater mean activation than females in the working memory task with a greater number of pixels being activated in the right superior parietal gyrus and right inferior occipital gyrus, and a greater BOLD magnitude occurring in the left inferior parietal lobe. However, despite these fMRI changes, there were no significant differences between males and females on cognitive performance of the task. In contrast, in the spatial attention task, men performed better at this task than women, but there were no significant functional differences between the two groups. In the word generation task, there were no external measures of performance, but in the functional measurements, males had a significantly greater mean activation than females, where males had a significantly greater BOLD signal magnitude in the left and right dorsolateral prefrontal cortex, the right inferior parietal lobe, and the cingulate. In neither of the motor tasks (right or left hand) did males and females perform differently. Our fMRI findings during the motor tasks were a greater mean BOLD signal magnitude in males in the right hand motor task, compared to females where males had an increased BOLD signal magnitude in the right inferior parietal gyrus and in the left inferior frontal gyrus. In conclusion, these results demonstrate differential patterns of activation in males and females during a variety of cognitive tasks, even though performance in these tasks may not vary, and also that variability in performance may not be reflected in differences in brain activation. These results suggest that in functional imaging studies in clinical populations it may be sensible to examine each sex independently until this effect is more fully understood.

Gender-related differences in lateralization of hippocampal activation and cognitive strategy

Gender-related differences in brain activation patterns and their lateralization associated with cognitive functions have been reported in the field of language, emotion, and working memory. Differences have been hypothesized to be due to different cognitive strategies. The aim of the present study was to test whether lateralization of brain activation in the hippocampi during memory processing differs between the sexes. We acquired functional magnetic resonance imaging data from healthy female and male study participants performing a spatial memory task and quantitatively assessed the lateralization of hippocampal activation in each participant. Hippocampal activation was significantly more left lateralized in women, and more right lateralized in men. Correspondingly, women rated their strategy as being more verbal than men did.

Low doses of delta-9 tetrahydrocannabinol (THC) have divergent effects on short-term spatial memory in young, healthy adults

Evidence suggests that manipulating spatial information within working memory depends upon a circuitry organized around the prefrontal cortex (PFC) and the activity of the catecholamine systems. Other evidence attests to the effects of Delta-9 tetrahydrocannabinol (THC) on short-term spatial memory function, most probably involving CB(1) receptor activity within hippocampal circuitries. At the current time, there have been no systematic studies of the effects of THC on spatial working memory in human subjects using tasks known to depend upon frontotemporal neural circuitries. We examined the effects of a single sublingual 5 mg dose of THC on a test of spatial working memory (requiring active manipulation of remembered spatial information for the management of future behavior) and a test of spatial span (requiring only the reproduction of sequences of previously presented spatial cues). In all, 19 healthy adults were administered 5 mg THC and placebo in a double-blind, placebo-controlled, within-subject, crossover design. Male participants performed more accurately than female participants. THC significantly enhanced spatial working memory performance of female participants. By contrast, male and female participants produced more intrusion errors during performance of the Spatial Span task. These results suggest that THC has relatively complex effects on spatial memory in human subjects, perhaps reflecting altered CB(1) receptor activity within frontotemporal circuits or altered activity of mesocortical dopaminergic pathways in PFC areas associated with spatial memory.

Sex-related lateralized effect of emotional content on declarative memory: an event related potential study

Several studies suggest that emotional arousal can promote memory storage. In this study, we evaluated the effects of emotional content on declarative memory, utilizing an adaptation of two versions of the same story, with different arousing properties (neutral or emotional), which have been already employed in experiments involving the enhancing effects of emotions on memory retention. We used event related potentials (ERP) to evaluate whether there is a sex-related hemispheric lateralization of electrical potentials elicited by the emotional content of a story. We compared left and right hemisphere P300 waves, recorded in P3 and P4 electrode sites, in response to emotional or neutral stimuli in men and women. In the left hemisphere, emotional stimuli elicited a stronger P300 in women, compared to men, as indexed by both amplitude and latency measures; moreover, the emotional content of the story elicited a stronger P300 in the right hemisphere in men than in women. The better memory for the arousal material may be related to the differential P300 at encoding. These data indicate that both sex and cerebral hemisphere constitute important, interacting influences on neural correlates of emotion, and of emotionally influenced memory.

Sex differences in brain activation elicited by humor

With recent investigation beginning to reveal the cortical and subcortical neuroanatomical correlates of humor appreciation, the present event-related functional MRI (fMRI) study was designed to elucidate sex-specific recruitment of these humor related networks. Twenty healthy subjects (10 females) underwent fMRI scanning while subjectively rating 70 verbal and nonverbal achromatic cartoons as funny or unfunny. Data were analyzed by comparing blood oxygenation-level-dependent signal activation during funny and unfunny stimuli. Males and females share an extensive humor-response strategy as indicated by recruitment of similar brain regions: both activate the temporal-occipital junction and temporal pole, structures implicated in semantic knowledge and juxtaposition, and the inferior frontal gyrus, likely to be involved in language processing. Females, however, activate the left prefrontal cortex more than males, suggesting a greater degree of executive processing and language-based decoding. Females also exhibit greater activation of mesolimbic regions, including the nucleus accumbens, implying greater reward network response and possibly less reward expectation. These results indicate sex-specific differences in neural response to humor with implications for sex-based disparities in the integration of cognition and emotion.

Sex differences in prefrontal cortical brain activity during fMRI of auditory verbal working memory

Functional imaging studies of sex effects in working memory (WMEM) are few, despite significant normal sex differences in brain regions implicated in WMEM. This functional MRI (fMRI) study tested for sex effects in an auditory verbal WMEM task in prefrontal, parietal, cingulate, and insula regions. Fourteen healthy, right-handed community subjects were comparable between the sexes, including on WMEM performance. Per statistical parametric mapping, women exhibited greater signal intensity changes in middle, inferior, and orbital prefrontal cortices than men (corrected for multiple comparisons). A test of mixed-sex groups, comparable on performance, showed no significant differences in the hypothesized regions, providing evidence for discriminant validity for significant sex differences. The findings suggest that combining men and women in fMRI studies of cognition may obscure or bias results.

fMRI-acoustic noise alters brain activation during working memory tasks

Scanner noise during functional magnetic resonance imaging (fMRI) may interfere with brain function and change blood oxygenation level dependent (BOLD) signals, a problem that generally worsens at the higher field strengths. Therefore, we studied the effect of increased acoustic noise on fMRI during verbal working memory (WM) processing. The sound pressure level of scanner noise was increased by 12 dBA from "Quiet" to "Loud" echo planar imaging (EPI) scans by utilizing resonant vibration modes of the gradient coil. A WM paradigm with graded levels of task difficulty was used to further access WM load. Increased scanner noise produced increased BOLD responses (percent signal change) bilaterally in the cerebellum, inferior (IFG), medial (medFG), and superior (SFG) frontal, fusiform (FusG), and the lingual (LG) gyri, and decreased BOLD responses bilaterally in the anterior cingulate gyrus (ACG) and the putamen. This finding suggests greater recruitment of attention resources in these brain regions, probably to compensate for interference due to louder scanner noise. Increased working memory load increased the BOLD signals in IFG and the cerebellum, but decreased the BOLD signals in the putamen and the LG. These findings also support the idea that brain function requires additional attention resources under noisier conditions. Load- and acoustic-noise-related changes in BOLD responses correlated negatively in the WM network. This study demonstrates that MR noise affects brain activation pattern. Future comparisons between studies performed under different acoustic conditions (due to differing magnetic field strengths, pulse sequences, or scanner manufacturers) might require knowledge of the sound pressure level of acoustic noise during fMRI.

Neuropsychological predictors of BOLD response during a spatial working memory task in adolescents: what can performance tell us about fMRI response patterns?

The relationship between standardized neuropsychological test performance and functional magnetic resonance imaging (fMRI) response during cognitive tasks is largely unknown. This exploratory investigation examined the relationship between neuropsychological test performance and fMRI response to a spatial working memory (SWM) task among 49 typically developing adolescents. Participants were administered a variety of neuropsychological tests in the domains of working memory, visuospatial skills, executive functioning, attention, learning and memory, visuomotor skills and processing speed, and language functioning. Neuropsychological domain scores were used to predict fMRI response during a SWM task. Results suggest that in many brain regions, neuropsychological performance negatively predicts fMRI response, suggesting that those teens with better neuropsychological abilities required fewer neural resources to adequately perform the task. This study provides further understanding of how neuropsychological abilities relate to neural activity during fMRI tasks, and provides an important link between neuropsychological and fMRI research.

Differential effects of chronic lithium and valproate on brain activation in healthy volunteers

RATIONALE

Previous functional imaging studies have shown altered brain activity during cognitive task performance in bipolar patients. However, the fact that these patients are often on medication makes it unclear to what extent these changes reflect treatment effects.

OBJECTIVES

This study aims to identify regional brain activity changes occurring following lithium and valproate treatment in healthy volunteers.

METHODS

This was a double-blind, placebo-controlled, study in which volunteers received either 1000 mg sodium valproate (n = 12), 900 mg lithium (n = 9), or placebo (n = 12). Functional images were acquired using functional magnetic resonance imaging (fMRI) while subjects performed three cognitive tasks, a word generation paradigm, a spatial attention task and a working memory task. fMRI was carried out both before and after 14 days of treatment with valproate, lithium or placebo. The changes in the magnitude of the blood-oxygen-level-dependent (BOLD) signal after treatment were compared between the groups using a one-way ANOVA for each task followed by a post-hoc multiple comparisons correction.

RESULTS

A significant group effect was noted in the change in BOLD signal magnitude from baseline to post-treatment, in all three tasks (working memory p< 0.000; spatial attention task p = 0.003; word generation paradigm p = 0.030). In the working memory task, the lithium group had a significant decrease in BOLD signal change, compared with the control group (p< 0.000). A decrease in BOLD signal change was also noted in the valproate group, in the spatial attention task (p = 0.004). Both lithium and valproate groups had a decreased BOLD signal in the verbal task, following treatment, compared with the placebo group (p = 0.061 (lithium approached significance); p = 0.050 (valproate)).

CONCLUSIONS

These findings suggest that lithium and valproate have independent effects on brain activation that vary in a task and region-dependent manner.

Right parietal contributions to verbal working memory: spatial or executive?

The left inferior parietal cortex has been claimed to be the site of the verbal short-term store, yet imaging studies report activity of a homologous right-hemisphere region in verbal working memory tasks as well. In spite of its prevalent activity, right parietal contributions to verbal working memory are poorly understood. To clarify its role in verbal working memory performance, we tested a patient with a lesion in the right parietal lobe on verbal and spatial versions of the N-back task. The patient was impaired in all the spatial conditions regardless of load (0-, 1-, and 2-back), whereas in the verbal N-back he was impaired only in the conditions with a memory demand (1- and 2-back). Given that we had presented stimuli at multiple locations in the verbal N-back, however, it remained possible that the lesion impaired spatial representation rather than verbal working memory per se. With central stimulus presentation, his performance dramatically improved indicating that his difficulty with the N-back task was largely due to his poor visuospatial abilities.

The influence of sex versus sex-related traits on long-term memory for gist and detail from an emotional story

Recent findings demonstrate sex-related differences in the neurobiological mechanisms by which emotional arousal influences memory, and raise questions about the extent to which memory for emotional events may differ between males and females. Here we examine whether sex-related differences exist in the recall of central (gist) information and peripheral detail from an emotional story. Healthy subjects viewed a brief, narrated slide-show containing emotional elements in its middle section. One week later, they received an incidental multiple-choice recognition test for the story. Following the test, each subject completed the BEM Sex-Role Inventory, an assessment of sex-related masculine and feminine traits. The results reveal no differences in recall of either central or peripheral story information when considering the performance of actual men and women, but a significant difference when considering male and females as determined by their BEM test scores. "BEM" males (subjects with net male BEM scores) showed significantly enhanced recall of central emotional information. "BEM" females did not. Both groups showed significantly enhanced recall of peripheral emotional information, although this effect appeared larger in BEM females than in BEM males. The influences of "BEM" sex and type of information (central, peripheral) significantly interacted to influence emotional memory performance. These findings confirm the existence of sex-related influences in the recall of emotional information, and suggest that sex-related traits, rather than actual sex per se, may be a more sensitive indicator of these influences.

fMRI of emotional responses to odors: influence of hedonic valence and judgment, handedness, and gender

Previous positron emission tomography studies of right-handed individuals show that the left orbitofrontal cortex is dominant during emotional processing of odors. We collected functional magnetic resonance imaging data from 28 subjects to study this network as a function of odor hedonic valence (pleasant vs. unpleasant), active hedonic judgments versus passive sensation of hedonically charged odors, handedness, and gender. Two functional runs were performed, with pleasant and unpleasant odors presented in different epochs. In the first run, subjects passively smelled odorants, whereas in the second run they rated degree of odor pleasantness or unpleasantness by using a "finger-span" technique that simulated a visual rating scale. Electrodermal and plethysmography responses were simultaneously recorded to control for covert, physiological manifestations of the emotional response. The piriform-amygdala area and ventral insula were activated more for unpleasant than pleasant odors. More extreme ratings were also associated with higher electrodermal amplitude, suggesting that activation stemmed more from emotional or hedonic intensity than valence, and that unpleasant odors induced more arousal than pleasant odors. Unpleasant odors activated the left ventral insula in right-handers and the right ventral insula in left-handers, suggesting lateralized processing of emotional odors as a function of handedness. Active decisions about odor pleasantness induced specific left orbitofrontal cortex activation, implicating the role of this area in the conscious assessment of the emotional quality of odors. Finally, left orbitofrontal cortex was more active in women than men, potentially in relation to women's well-documented advantage in odor identification.

Immunohistochemical changes induced by repeated footshock stress: revelations of gender-based differences

As a growing literature has proven, adverse experiences, particularly when severe and persistent, play a pivotal role in the development of neuronal dysfunctions and psychopathology. In the present study, the neurochemical changes induced by acute and repeated footshock exposure were investigated at the molecular and cellular level, using c-fos and phospho-ERK1/2 immunoreactivity and gene expression arrays. Marked gender-related differences were found following both acute and prolonged footshock exposure. Acute aversive conditioning resulted in significant immunohistochemical changes that might be critically involved in the modulation of fear-related responses, especially in males. Prolonged footshock exposure, on the contrary, was associated with sustained hypothalamic-pituitary-adrenal axis hyperactivity, differential gender-related patterns of cortical-limbic activity, and abnormal neuronal plasticity, especially in medial prefrontocortical regions. These data may provide additional insights into the understanding of the neural circuits underlying the effects of acute and repeated footshock exposure as well as clarify some of the mechanisms involved in the development of stress-related neuronal abnormalities.

Sex- and hemisphere-related influences on the neurobiology of emotionally influenced memory

Recent findings are beginning to reveal apparently pronounced influences of both sex and cerebral hemisphere on the neurobiology of emotionally influenced memory. In this article, I first provide a brief, general overview of sex-related influences on brain and cognition. I next describe recent findings from my laboratory and others demonstrating sex-related influences on neural mechanisms underlying emotionally influenced explicit recall of emotionally arousing events. Both the hemispheric involvement of the human amygdala in memory for emotionally arousing events and the impairing effect of beta-adrenergic blockade on memory for emotional events, exhibit sex-related differences. I hypothesize that both of these effects relate to a modulatory influence of each amygdala on ipsilateral hemispheric function. Specifically, I hypothesize that the right hemisphere amygdala modulates right hemispheric processing of global/central aspects of a situation (an effect more pronounced in males), while the left hemisphere amygdala modulates left hemispheric processing of more local/fine detail aspects of a situation (an effect more pronounced in females). More generally, these findings presented here suggest that the interacting influences of sex and cerebral hemisphere on emotionally influenced memory are more pronounced than has been widely appreciated to date.

The Effects of Gender on the Neural Substrates of Pitch Memory

Imaging studies have indicated that males and females differ anatomically in brain regions thought to underlie language functions. Functional studies have corroborated this difference by showing gender differences in terms of language processing with females relying on less lateralized processing strategies than males. Gender differences in musical functions might show similar differences in functional asymmetries, although no detailed study has been performed. The current study employed a pitch memory task while acquiring functional magnetic resonance images to investigate possible differences in hemispheric processing between males and females. Gender differences were found in the time course of activation (during the first four imaging time points after the end of the auditory stimulus—“perceptual phase”—and the subsequent three imaging time points after the end of the auditory stimulus—“memory phase”) in both anterior and posterior perisylvian regions. Male subjects had greater lateralized activations (left &gt; right) in anterior and posterior perisylvian regions during the “perceptual” as well as during the “memory” phase. There was a trend for males to have more cerebellar activation than females. Females showed more prominently posterior cingulate/retrosplenial cortex activation compared to males. Although activation patterns differed, there was no difference in the behavioral performance between both genders. These data indicate that similar to language studies, males rely more on left lateralized hemispheric processing even for basic pitch tasks.