The generative neural microdynamics of cognitive processing.

The entorhinal cortex and hippocampus form a recurrent network that informs many cognitive processes, including memory, planning, navigation, and imagination. Neural recordings from these regions reveal spatially organized population codes corresponding to external environments and abstract spaces. Aligning the former cognitive functionalities with the latter neural phenomena is a central challenge in understanding the entorhinal-hippocampal circuit (EHC). Disparate experiments demonstrate a surprising level of complexity and apparent disorder in the intricate spatiotemporal dynamics of sequential non-local hippocampal reactivations, which occur particularly, though not exclusively, during immobile pauses and rest. We review these phenomena with a particular focus on their apparent lack of physical simulative realism. These observations are then integrated within a theoretical framework and proposed neural circuit mechanisms that normatively characterize this neural complexity by conceiving different regimes of hippocampal microdynamics as neuromarkers of diverse cognitive computations.

Reproducible stability of verbal and spatial functions along the menstrual cycle.

Recent studies have reported brain changes in response to ovarian hormonal fluctuations along the menstrual cycle. However, it remains unclear, whether these brain changes are of an adaptive nature or whether they are linked to changes in behavior along the menstrual cycle, particularly with respect to cognitive performance. To address this knowledge gap, we report results from 3 well-powered behavioral studies with different task designs, leveraging the advantages of each design type. In all three studies we assessed whether verbal or spatial performance (i) differed between cycle phases, (ii) were related to estradiol and / or progesterone levels and (iii) were moderated by individual hormone sensitivity as estimated by premenstrual symptoms. Overall, results of all three studies point towards a null effect of menstrual cycle phase and - to a lesser extent - ovarian hormones on verbal and spatial performance and provided no evidence for a moderation of this effect by individual hormone sensitivity. We conclude that there is substantial consistency in verbal and spatial performance across the menstrual cycle, and that future studies of intra-individual variation are needed.

Effect of Intraoperative Mixed-Reality use on Nonsurgical Team Members in the Neurosurgical Operating Room: An Explorative Study.

OBJECTIVES: Mixed-reality (MxR) implementation in the neurosurgical operating room (OR) is emerging, but the impact of this technology on the nonsurgical OR staff has not been investigated yet. The purpose of this study is to evaluate the nonsurgical OR team's perception of the impact of intraoperative MxR use. METHODS: The evaluation occurred in a neurosurgical institution implementing MxR perioperatively on a daily basis for 15 months. The questionnaire measuring the impact of MxR consisted of 5 binary questions and 4 subquestions measured on a 7-point Likert scale. RESULTS: Fifteen nonsurgical staff members of a neurosurgical OR team were interviewed. Most (85%) of the cohort stated that MxR changed their perception of the surgery, improving understanding of the spatial orientation (median 6, interquartile range 5-7) and of the pathology dimensions (6, 5.5-7). One participant (7%) was of the opinion that MxR disrupted the OR workflow. The majority (60%) stated that use of the holograms improved efficiency in the OR. The participants were neutral about the potential role of MxR to improve communication among different OR team members (4, 2-5) and overall teamwork (4, 2-5). CONCLUSIONS: The use of 3-Dimensional interactive holograms of neurosurgical cases in the nonsterile intraoperative phase was not perceived as distractive, and neither was OR flow disruption by members of the nonsurgical OR staff. MxR was considered an adjunct to improve OR efficiency. A thorough understanding of the impact of MxR's implementation on the nonsurgical staff could lead to targeted improvement of the MxR use and, potentially, to increasing the quality of the teamwork.

Subjective visual vertical and postural control in patients following cochlear implantation.

BACKGROUND: Cochlear implantation (CI) is associated with changes in the histopathology of the inner ear and impairment of vestibular function. OBJECTIVE: The objectives of our study were to evaluate patients for clinical manifestations of space perception and balance changes before surgery, compare them with asymptomatic subjects (controls), and report changes in posturography and subjective visual vertical (SVV) during the acute post-surgery period in patients. METHODS: Examination was performed using static posturography and the SVV measurement. We examined 46 control subjects and 39 CI patients. Patients were examined pre-surgery (Pre), 2nd day (D2) and then 14th day (D14) after implantation. RESULTS: Baseline SVV was not different between patients and control group. There was a statistically significant difference (p < 0.001) in SVV between subgroups of right- and left-implanted patients at D2 (-1.36±3.02° and 2.71±2.36°, right and left side implanted respectively) but not Pre (0.76±1.07° and 0.31±1.82°) or D14 (0.72±1.83° and 1.29±1.60°). Baseline posturography parameters between patients and control group were statistically significantly different during stance on foam with eyes closed (p < 0.05). There was no statistically significant difference in posturography among Pre, D2 and D14. CONCLUSIONS: CI candidates have impaired postural control before surgery. CI surgery influences perception of subjective visual vertical in acute post-surgery period with SVV deviation contralateral to side of cochlear implantation, but not after two weeks.

The power of vision: calibration of auditory space after sight restoration from congenital cataracts.

Early visual deprivation typically results in spatial impairments in other sensory modalities. It has been suggested that, since vision provides the most accurate spatial information, it is used for calibrating space in the other senses. Here we investigated whether sight restoration after prolonged early onset visual impairment can lead to the development of more accurate auditory space perception. We tested participants who were surgically treated for congenital dense bilateral cataracts several years after birth. In Experiment 1 we assessed participants' ability to understand spatial relationships among sounds, by asking them to spatially bisect three consecutive, laterally separated sounds. Participants performed better after surgery than participants tested before. However, they still performed worse than sighted controls. In Experiment 2, we demonstrated that single sound localization in the two-dimensional frontal plane improves quickly after surgery, approaching performance levels of sighted controls. Such recovery seems to be mediated by visual acuity, as participants gaining higher post-surgical visual acuity performed better in both experiments. These findings provide strong support for the hypothesis that vision calibrates auditory space perception. Importantly, this also demonstrates that this process can occur even when vision is restored after years of visual deprivation.

Contribution of the medial eye field network to the voluntary deployment of visuospatial attention.

Historically, the study of patients with spatial neglect has provided fundamental insights into the neural basis of spatial attention. However, lesion mapping studies have been unsuccessful in establishing the potential role of associative networks spreading on the dorsal-medial axis, mainly because they are uncommonly targeted by vascular injuries. Here we combine machine learning-based lesion-symptom mapping, disconnection analyses and the longitudinal behavioral data of 128 patients with well-delineated surgical resections. The analyses show that surgical resections in a location compatible with both the supplementary and the cingulate eye fields, and disrupting the dorsal-medial fiber network, are specifically associated with severely diminished performance on a visual search task (i.e., visuo-motor exploratory neglect) with intact performance on a task probing the perceptual component of neglect. This general finding provides causal evidence for a role of the frontal-medial network in the voluntary deployment of visuo-spatial attention.

Can arrows change the subjective perception of space? Exploring symbolic attention repulsion.

The attention repulsion effect (ARE) refers to distortions in the perception of space for areas near the focus of attention. For instance, when attending to the right-hand side of the visual field, objects in central vision may appear as though they are shifted to the left. The phenomenon is likely caused by changes in visual cell functioning. To date, research on the ARE has almost exclusively used exogenous manipulations of attention. In contrast, research exploring endogenous attention repulsion has been mixed, and no research has explored the effects of nonpredictive arrow cues on this phenomenon. This gap in the literature is unexpected, as symbolic attention appears to be a unique form of attentional orienting compared with endogenous and exogenous attention. Therefore, this study explored the effects of symbolic orienting on spatial repulsion and compared it with an exogenously generated ARE. Across four experiments, both exogenous and symbolic orienting resulted in AREs; however, the magnitude of the symbolic ARE was smaller than the exogenous ARE. This difference in magnitude persisted, even after testing both phenomena using stimulus timing parameters known to produce optimal effects in traditional attentional cueing paradigms. Therefore, compared with symbolic attention, it appears that exogenous manipulations may tightly constrict attention resources on the cued location, in turn, potentially influencing the functioning of visual cells for enhanced perceptual processing.

Estradiol effects on spatial memory in women.

To examine the role of estradiol in hippocampal-dependent spatial memory in women, 86 female undergraduates were tested in a virtual Morris water task (VMWT), a virtual radial arm maze (VRAM), and a mental rotation task (MRT) within a single daily session. The VMWT and RAM were also administered 24 h later to examine the effects of estradiol on memory consolidation. Women on oral contraceptives (OCs) or those who were naturally cycling and exhibited low estradiol (LE) or high estradiol (HE), as determined by salivary assays, were included. At the start of day two, the HE group showed superior spatial reference memory on the VMWT relative to the LE group, as evidenced by significantly shorter distances navigating to the hidden platform. The LE group also had the poorest probe trial performance at the start of day two compared to both other groups. There were no group differences in performance on the RAM or MRT. These results provide support for estradiol's role in the consolidation of spatial reference memory in women, and emphasize the differential sensitivities of various virtual memory tasks in assessing spatial memory function in women.

Spatial incompatibility training can prevent the occurrence of the enhanced Simon effect in elderly / Treinamento de incompatibilidade espacial pode prevenir a ocorrência do efeito Simon ampliado em idosos

The Simon effect is typically larger for older people than for young adults, maybe due to age-related decline in inhibitory capabilities. 32 right-handed aged people (5 male, 27 female; mean of 67,1 years ± 5,5) participated in this study. In screening were used the Mini-Mental State Examination and the Center for Epidemiological Study Depression Scale. Then, half of the participants practiced the spatial incompatibility task before the Simon task and the other group was only tested on the Simon task. The analysis of variance considering practice (incompatible, no-practice group) and correspondence (corresponding, non-corresponding) revealed a two-way interaction (F = 7.07; p = 0.012; ηp2 = 0.191) showing that the Simon effect was eliminated in the incompatible practice group, but remained intact in the group with no previous practice. These results indicated that cognitive processes required to the transfer of learning are preserved in elderly, being potentially useful to influence spatial inhibitory capabilities.

O efeito Simon é tipicamente maior em pessoas idosas do que em adultos jovens, talvez devido ao declínio de capacidades inibitórias em função da idade. Participaram deste estudo 32 pessoas idosas e destras (5 homens e 27 mulheres; média de 67,1 anos ± 5,5). Para rastreio, foram usados o Mini Exame do Estado Mental e a escala de depressão do Center for Epidemiological Studies. Metade dos participantes praticou a tarefa de incompatibilidade espacial antes da tarefa de Simon e o outro grupo foi testado apenas na tarefa de Simon. A análise de variância, considerando a prática prévia (incompatível ou sem prática) e correspondência (correspondente, não correspondente), indicou uma interação dupla (F = 7,07; p = 0,012; ηp2 = 0,191), demonstrando que o efeito Simon foi eliminado no grupo de prática incompatível, mas permaneceu ampliado no grupo sem prática anterior. Esses resultados indicaram que os processos cognitivos necessários para transferir a aprendizagem estão preservados em idosos, sendo potencialmente úteis para influenciar as capacidades inibitórias espaciais.

Do automotive window films affect drivers' safety by decreasing vision sensitivity? A Cross-sectional study / Películas automotivas e perda de acuidade visual? Estudo transversal

ABSTRACT Objective: To measure visual acuity in high contrast and low contrast sensitivities in different grades of visible light transmission films in three different positions (front, lateral and rear windows). Methods: Forty-four healthy volunteers between 30-75 y-o, with BCVA better than 0,5, were tested in the 5 following vehicles with different grades of visible light transmission films. Vehicle 1: 75% in the front and 70% in the lateral and rear windows; Vehicle 2: 70% in the front and lateral windows and 28% in the rear; Vehicle 3: 70% in the front, 28% in the lateral and 15% rear; Vehicle 4: 35% in all 3 windows; Vehicle 5: 50% in the front, 20% in the lateral and 15% in the rear. Descriptive statistics were used and the average of the 3 measurements of VA was considered. Wilcoxon Test was applied to compare the average visual acuity in each vehicle and position. P value<0.05 was considered statistically significant. Results: According to the Brazilian Traffic Regulations for driving in categories C/D/E, when low contrast was tested in the front window, all visible light transmissions were borderline, in the lateral window they were all outside the limit, while in the rear window for both low and high contrast, all visible light transmissions tested were outside the limit and also borderline for driving in categories A/B, with the exception of the vehicle with visible light transmission of 35%. Conclusion: Visual acuity is affected, especially in the rear window, by the use of automotive films. The study is an alert that window films is a possible cause of accidents and may contribute to the revision of traffic regulations worldwide.

RESUMO Objetivo: Medir a acuidade visual em alto e baixo contraste nas diversas graduações de transparência de filmes em três janelas de veículos: frontal, lateral e traseira. Métodos: Foram avaliados 44 voluntários saudáveis entre 30 e 75 anos, com acuidade visual melhor corrigida acima de 0,5, em cinco veículos, sendo: veículo 1, com 75% de transparência frontal e 70% na lateral e traseira; veículo 2, com 70% na frontal e na lateral e 28% na traseira; veículo 3, com 70% na frontal, 28% na lateral e 15% na traseira; veículo 4, com 35% nas três janelas; e veículo 5, com 50% na frontal, 20% na lateral e 15% na traseira. Foi realizada estatística descritiva utilizando a média de três medidas consecutivas, com teste de Wilcoxon para comparar a média de acuidade visual em cada janela, e foi considerado estatisticamente significativo quando valor de p<0,05. Resultados: Todas as transparências testadas nos vidros reduziram a acuidade visual em situação de baixo contraste para níveis limítrofes na janela frontal e níveis ilegais na lateral para conduzir veículos nas categorias C/D/E. Na janela traseira, tanto em alto quanto em baixo contraste, todas as transparências mostraram redução da acuidade visual para níveis ilegais para categorias C/D/E e limítrofes para as categorias A/B, exceto na transparência de 35%. Conclusão: A acuidade visual é reduzida pelo uso dos filmes automotivos, especialmente na janela traseira. Condutores de veículos com filmes devem ser alertados pelo risco aumentado de acidentes. Esse dado científico propõe revisões nas regulações de tráfego mundiais.

Conceitos básicos de percepção de cena / Basic concepts of scene perception

A pesquisa sobre percepção de cenas é um esforço da comunidade científica em superar as dificuldades apresentadas ao estudo de estímulos complexos. As consistentes descobertas provaram a viabilidade do tema e encorajam uma abordagem mais holística e integrada nas investigações em percepção visual. Esse esforço e seus achados são, entretanto, pouco conhecidos pelos leitores em língua portuguesa e, até mesmo, entre alguns especialistas que se interessam pelo tema. O objetivo deste trabalho é fazer uma apresentação do campo, esboçar seu desenvolvimento, identificar suas principais questões e demonstrar sua pertinência e importância. Para isso, uma revisão seletiva de textos foi executada entre os autores que construíram os fundamentos da percepção de cenas. Ao concluir a leitura, espera-se que o leitor constate o papel relevante dos processos mnemônicos e do sujeito que observa no processo de captação visual do ambiente natural.

Scene perception research is a scientific community effort to overcome difficulties presented to the study of complex stimuli. Consistent findings support feasibility of the theme and encourage a more holistic and integrated approach to visual perception research. This effort and its findings are, however, poorly known by readers in Portuguese language, even among experts interested in the subject. The purpose of this paper is to introduce this field of research, outline its development, identify its main issues and demonstrate its relevance and importance. This task was accomplished by a selective review of papers from authors who built the foundations of scene perception. Upon completion of the reading, it is expected that the reader understands the relevant role of mnemonic processes and of the observer in the process of visual capture of natural environments.

Evaluation of subjective vertical perception among stroke patients: a systematic review / Avaliação da percepção vertical subjetiva em pacientes com acidente vascular cerebral: uma revisão sistemática

Abstract Background: Verticality misperception is relatively common among patients after stroke, and it may be evaluated in terms of (a) subjective visual vertical (SVV), (b) subjective haptic vertical (SHV) and (c) subjective postural vertical (SPV). To better understand these assessment methods, we conducted a systematic review of the methodological characteristics of different protocols for evaluating SVV, SHV and SPV among individuals after stroke. Objective: To standardize the methodological characteristics of protocols for evaluating verticality perception after stroke. Methods: We searched the following databases: PUBMED, regional BVS portal (MEDLINE, LILACS, IBECS, CUBMED, Psychology Index and LIS), CINAHL, SCOPUS, Web of Science, Science Direct, Cochrane Library and PEDro. Two review authors independently used the QUADAS method (Quality Assessment of Diagnostic Accuracy Studies) and extracted data. Results: We included 21 studies in the review: most (80.9%) used SVV, eight (38.1%) used SPV and four (19.0%) used SHV. We observed high variability in assessments of verticality perception, due to patient positions, devices used, numbers of repetitions and angle of inclination for starting the tests. Conclusion: This systematic review was one of the first to explore all the methods of assessing verticality perception after stroke, and it provides crucial information on how to perform the tests, in order to guide future researchers/clinicians.

Resumo Antecedentes: A percepção errônea da verticalidade é relativamente comum em pacientes após Acidente Vascular Cerebral (AVC) e pode ser avaliada pelas: (a) vertical visual subjetiva (SVV), (b) vertical háptica subjetiva (SVH) e (c) vertical postural subjetiva (SPV). Para melhor compreender esses métodos de avaliação, realizamos uma revisão sistemática das características metodológicas de diferentes protocolos para avaliações de SVV, SHV e SVP em indivíduos após AVC. Objetivo: Padronizar as características metodológicas de protocolos de avaliação da verticalidade após AVC. Métodos: Foi realizada busca nas bases de dados PUBMED, Portal Regional da BVS (MEDLINE, LILACS, IBECS, CUBMED, Psychology Index, LIS), CINAHL, SCOPUS, Web of Science, Science Direct, Biblioteca Cochrane e PEDro. Dois revisores avaliaram independentemente o QUADAS (Avaliação da Qualidade dos Estudos de Precisão de Diagnóstico) e extraíram os resultados. Resultados: Foram incluídos 21 estudos: a maioria (80,9%) utilizando a SVV, oito (38,1%) a SPV e quatro (19,0%) a SHV. Observou-se grande variabilidade na avaliação da verticalidade, devido às posições dos pacientes, dispositivos utilizados, número de repetições e ângulo de inclinação para iniciar os testes. Conclusão: Esta revisão sistemática é uma das primeiras a explorar todos os métodos de avaliação da verticalidade após o AVC e fornece informações cruciais sobre como realizar os testes para orientar os futuros pesquisadores e clínicos.

Integrating pheromonal and spatial information in the amygdalo-hippocampal network.

Vomeronasal information is critical in mice for territorial behavior. Consequently, learning the territorial spatial structure should incorporate the vomeronasal signals indicating individual identity into the hippocampal cognitive map. In this work we show in mice that navigating a virtual environment induces synchronic activity, with causality in both directionalities, between the vomeronasal amygdala and the dorsal CA1 of the hippocampus in the theta frequency range. The detection of urine stimuli induces synaptic plasticity in the vomeronasal pathway and the dorsal hippocampus, even in animals with experimentally induced anosmia. In the dorsal hippocampus, this plasticity is associated with the overexpression of pAKT and pGSK3ß. An amygdalo-entorhino-hippocampal circuit likely underlies this effect of pheromonal information on hippocampal learning. This circuit likely constitutes the neural substrate of territorial behavior in mice, and it allows the integration of social and spatial information.

Sex hormones modulate sex differences and relate to hemispheric asymmetries in a divided visual field Navon task.

Sex differences in functional hemispheric asymmetries (FHA) have been hypothesized as a fundamental mechanism behind sex differences in global-local processing. So far, it has not been assessed how interactive effects of sex and hemifield presentation influence common indicators of global precedence. The current study is the first to investigate the involvement of FHAs by using a divided visual field Navon paradigm and controlling for sex hormone status. Moreover, various factors that have previously shown a reliable influence on global-local processing performance are verified within the context of unilateral presentation. 39 men and 39 naturally cycling women in their luteal cycle phase completed a divided visual field Navon task with the instruction to detect targets either at any level (divided attention) or only at the global or local level (selective attention) in three different spacing conditions. The obtained evidence reveals significant sex differences in the global advantage effect (faster reaction to global vs. local level targets) for densely spaced letter stimuli, as well as significant sex differences in global-local level interference, with findings on both measures being mediated by testosterone. Also, estradiol showed different relationships to the global advantage effect in men and women together with a positive relationship to global advantage for the selective attention condition. Behavioural reaction time results were mirrored by accuracy measures but presented significantly higher global- over local-level accuracy in women compared to men for the divided attention condition. Our results did not show significant sex differences in FHAs but indicate differential relationships between progesterone and FHAs in men and women. In conclusion, sex hormones emerged as central mediators of sex differences in global precedence and possible moderators of hemispheric asymmetries.

Ipsilesional spatial bias after a focal cerebral infarction in the medial agranular cortex: A mouse model of unilateral spatial neglect.

Unilateral spatial neglect is a disorder of higher brain function that occurs after a brain injury, such as stroke, traumatic brain injury, brain tumor, and surgical procedures etc., and leads to failure to attend or respond to stimuli presented to the side contralateral to the lesioned cerebral hemisphere. Because patients with this condition often have other symptoms due to the presence of several brain lesions, it is difficult to evaluate the recovery mechanisms and effect of training on unilateral spatial neglect. In this study, a mouse model of unilateral spatial neglect was created to investigate whether the size of the lesion is related to the severity of ipsilesional spatial bias and the recovery process. Focal infarction was induced in the right medial agranular cortex (AGm) of mice via photothrombosis. After induction of cerebral infarction, ipsilesional spatial bias was evaluated for 9 consecutive days. The major findings were as follows: (1) unilateral local infarction of the AGm resulted in ipsilateral bias during internally guided decision-making; (2) the lesion size was correlated with the degree of impairment rather than slight differences in the lesion site; and (3) mice with anterior AGm lesions experienced lower recovery rates. These findings suggest that recovery from ipsilesional spatial bias requires neural plasticity within the anterior AGm. This conditional mouse model of ipsilesional spatial bias may be used to develop effective treatments for unilateral spatial neglect in humans.

Multi-band MEG signatures of BOLD connectivity reorganization during visuospatial attention.

The functional architecture of the resting brain, as measured with the blood oxygenation level-dependent functional connectivity (BOLD-FC), is slightly modified during task performance. In previous work, we reported behaviorally relevant BOLD-FC modulations between visual and dorsal attention regions when subjects performed a visuospatial attention task as compared to central fixation (Spadone et al., 2015). Here we use magnetoencephalography (MEG) in the same group of subjects to identify the electrophysiological correlates of the BOLD-FC modulation found in our previous work. While BOLD-FC topography, separately at rest and during visual attention, corresponded to neuromagnetic Band-Limited Power (BLP) correlation in the alpha and beta bands (8-30 Hz), BOLD-FC modulations evoked by performing the visual attention task (Spadone et al. 2015) did not match any specific oscillatory band BLP modulation. Conversely, following the application of an orthogonal spatial decomposition that identifies common inter-subject co-variations, we found that attention-rest BOLD-FC modulations were recapitulated by multi-spectral BLP-FC components. Notably, individual variability of alpha connectivity between Frontal Eye Fields and visual occipital regions, jointly with decreased interaction in the Visual network, correlated with visual discrimination accuracy. In summary, task-rest BOLD connectivity modulations match multi-spectral MEG BLP connectivity.

Dissociation between visuospatial neglect assessment tasks and its neuroanatomical substrates: a case report.

Visuospatial neglect possesses significant heterogeneity in clinical features and neuroanatomical substrates. Behavioral dissociations on different neglect tasks have been reported in the past, and the investigation of their respective anatomical correlates at cortical and, to a lesser degree, subcortical levels has been attempted in stroke studies. We report a patient with a neoplasm occupying the right ventral post-central gyrus and anterior supramarginal gyrus. The patient was admitted preoperatively with dissociation on the performance of neglect tasks, showing clinical deficits in the line bisection task and clock drawing, but not on the cancelation task. The patient underwent an awake craniotomy for tumor excision. Intraoperative visuospatial mapping was employed by applying direct electrical stimulation (DES) to the supramarginal gyrus and the ventral branch of the superior longitudinal fasciculus (SLF III) during the line bisection task. According to our findings, DES was ineffective at the cortical level, but it induced strong rightward bias when applied subcortically at the SLF III. By combining our preoperative and intraoperative anatomical and clinical data, we suggest that the posterior part of the SLF III might have a distinct role in the perceptual component of neglect. Our findings are discussed within the context of previous literature supporting the notion that particular behavioral features of spatial neglect are mediated by different white-matter connections.

Endogenous variation in estradiol in women affects the weighting of metric and categorical information in spatial location memory.

Recent work has suggested that sex differences may exist in the strategies or types of cues that are utilized by men and women to remember discrete spatial locations or routes through a visual environment. The current study investigated the effects of circulating estradiol levels in women on the relative weighting of categorical versus fine-grained 'metric' information in a test of short-term memory for spatial locations, either presented within a simple geometric surround (a circular enclosure) or within more visually complex landscape scenes. Patterns of displacement error in the point location estimates made by men and women were analyzed. Results confirmed a sex difference in the weighting of metric versus categorical cues. Relative to men, women's estimates of locations were more strongly biased toward the center of the surrounding category (i.e., toward the category 'prototype'). Furthermore, objective measures of estradiol via saliva collected at the time of memory testing showed that, among naturally-cycling women, estradiol concentrations correlated in a positive, graded, fashion with the degree of emphasis that women placed on categorical information when estimating point locations. No associations were found for progesterone. These findings are consistent with a wider body of research showing that biological sex and reproductive hormone levels, including 17ß-estradiol, can subtly influence performance on certain spatial tasks. This is the first study to show that circulating estradiol levels may influence the relative emphasis placed on categorical versus metric cues when remembering simple point locations.

Attention-enhancing effects of propranolol and synergistic effects with nicotine.

Nicotine increases the output of every major neurotransmitter. In previous studies designed to identify the secondary neurotransmitter systems mediating nicotine's attention-enhancing effects in a rat model, the ß-adrenoceptor antagonist propranolol blocked these effects. The present study was designed to test whether this mechanism held true in humans, thus guiding development of novel nicotinic agonists for cognitive enhancement. Twenty-six nonsmokers completed a nicotine (7 mg/24 h transdermally) x propranolol (40 mg p.o., body weight-adjusted) interaction study. Over four test days, each participant received double-placebo, nicotine only, propranolol only, and nicotine plus propranolol in randomized sequence before cognitive testing. No drug effects were seen in a visuospatial attention task. In the Rapid Visual Information Processing Task, performed in two 15-min blocks, neither drug alone significantly affected hit rate, but both drugs combined acted synergistically to alleviate its decrement over time in the first block and displayed additive beneficial effects in the second. In a change detection task, propranolol enhanced accuracy and reduced reaction time independent of nicotine presence. Propranolol also enhanced subjective self-reports of vigor. Overall, the findings were contrary to those hypothesized. Propranolol displayed beneficial effects on cognition, especially on sustaining performance over time. ß-adrenoceptor activation by nicotine-induced noradrenaline release appeared to limit performance-enhancing effects of nicotine, because they were unmasked by ß-adrenoceptor antagonism. The results suggest that cognitive effects of changes in ß-adrenoceptor tone are context-dependent; contrary to rodent paradigms, human cognitive paradigms require no physical orienting in space but prolonged periods of remaining stationary while sustaining predictable processing demands.