Gender differences in the neural correlates of humor processing: implications for different processing modes

Humor is a complex phenomenon of human social cognition with large inter-individual variability. Gender differences in emotion processing are a common finding in functional neuroimaging studies, and have been documented in behavioral studies of humor, but have received limited attention in functional neuroimaging studies on humor. Using blood oxygenation level dependent (BOLD) contrasts with high-field (3T) functional magnetic resonance imaging (fMR) we investigated 29 healthy subjects (14 female, 15 male) during the processing of humorous cartoons. In women, the ventral system implicated ín detection and appraisal of emotion was activated, including amygdala, insula, and Anterior Cingulate Cortex (ACC). Men showed activation in both the ventral and dorsal processing systems. The results indicate that women process humor though limbic reactivity, involving appraisal of its emotional features, while men apply more evaluative, executive resources to humor processing.

Towards clinical trials of lie detection with fMRI

Recent reports of successful fMRI-based discrimination between lie and truth in single subjects raised the interest of prospective users and a public concern about the potential scope of this technology. The increased scrutiny highlighted the lack of controlled "real life", i.e. prospective clinical trials of this technology that conform to the common standards of medical device development. The ethics of conducting such trials given the paucity of data on fMRI-based lie detection has also been questioned. To probe the potential issues of translating the laboratory research into practice, we conducted a case study in which we adapted the standard Guilty Knowledge Test (GKT), a well-established model of producing deception, to the common scenario of lying on a resume. The task consisted of questions about pertinent items on the subject's resume, three of which could be independently verified as truth (KNOWN) and three that could not be verified and were thus termed UNKNOWN. The subject had an incentive to lie on all UNKNOWN items, and on debriefing confirmed that he had done so. Data was preprocessed, masked with a priori regions of interest, thresholded, and qualitatively evaluated for consistency with the previously reported prefronto-parietal Lie > Truth pattern. Deceptive responses to two out of the three UNKNOWN items were associated with the predicted prefronto-parietal fMRI pattern. In the third UNKNOWN this pattern was absent, and instead, increased limbic (amygdala and hippocampus) response was observed. Based on published prefronto-parietal Lie response pattern, only the first two items could be categorized as Lie. If confirmed, this demonstration of amygdala and hippocampus activation in a Lie > Truth contrast illustrates the need to integrate the limbic system and its emotional and cognitive correlates into the existing model of deception. Our experiment suggests an approach to a naturalistic scenario and the research questions that need to be answered in order to set the stage for prospective clinical trials of fMRI-based lie detection.

Effect of abstinence challenge on brain function and cognition in smokers differs by COMT genotype

The val allele of the catechol-O-methyltransferase (COMT) val(158)met polymorphism has been linked with nicotine dependence and with cognitive performance in healthy volunteers. We tested the hypothesis that the val allele is a risk factor for altered brain function and cognition during nicotine abstinence as compared with the normal smoking state. Chronic smokers (n=33) were genotyped prospectively for the COMT polymorphism for balanced selection of met/met, val/met and val/val groups. A visual N-back working memory task was performed during two separate blood oxygen level-dependent (BOLD) functional magnetic resonance imaging sessions in counterbalanced order: (1) smoking as usual, and (2)>or=14 h confirmed abstinence. Significant genotype by session interactions were observed for BOLD signal in right dorsolateral prefrontal cortex (DLPFC; (P=0.0005), left DLPFC (P=0.02) and dorsal cingulate/medial prefrontal cortex (P=0.01) as well as for task reaction time (P=0.03). Smokers with val/val genotypes were more sensitive to the abstinence challenge than carriers of the met allele, with the greatest effects on BOLD signal and performance speed at the highest working memory load. These data suggest a novel brain-behavior mechanism that may underlie the increased susceptibility to nicotine dependence and smoking relapse associated with the COMT val allele. Exploration of the effects of COMT inhibitors as a possible smoking cessation aid in this group may be warranted.

Assessment of NMDA receptor NR1 subunit hypofunction in mice as a model for schizophrenia

N-methyl-D-aspartate receptors (NMDARs) play a pivotal role in excitatory neurotransmission, synaptic plasticity and brain development. Clinical and experimental evidence suggests a dysregulation of NMDAR function and glutamatergic pathways in the pathophysiology of schizophrenia. We evaluated electrophysiological and behavioral properties of NMDAR deficiency utilizing mice that express only 5-10% of the normal level of NMDAR NR1 subunit. Auditory and visual event related potentials yielded significantly increased amplitudes for the P20 and N40 components in NMDAR deficient (NR1(neo)-/-) mice suggesting decreased inhibitory tone. Compared to wild types, NR1(neo)-/- mice spent less time in social interactions and showed reduced nest building. NR1(neo)-/- mice displayed a preference for open arms of a zero maze and central zone of an open field, possibly reflecting decreased anxiety-related behavioral inhibition. However, locomotor activity did not differ between groups in either home cage environment or during behavioral testing. NR1(neo)-/- mice displayed hyperactivity only when placed in a large unfamiliar environment, suggesting that neither increased anxiety nor non-specific motor activation accounts for differential behavioral patterns. Data suggest that NMDAR NR1 deficiency causes disinhibition in sensory processing as well as reduced behavioral inhibition and impaired social interactions. The behavioral signature in NR1(neo)-/- mice supports the impact of impaired NMDAR function in a mouse model with possible relevance to negative symptoms in schizophrenia.

Effect of retrieval effort and switching demand on fMRI activation during semantic word generation in schizophrenia

Verbal fluency deficits in schizophrenia are difficult to interpret because the tasks are multi-factorial and groups differ in total words generated. We manipulated retrieval and switching demands by requiring alternation between over-learned sequences in which retrieval is relatively automatic (OS) and semantic categories requiring increased retrieval effort (SC). Controlled processing was also manipulated by including switching and non-switching conditions, and formal thought disorder (FTD) was assessed with the communication disorders index (CDI). The OS/SC semantic fluency paradigm was administered during fMRI to 13 patients with schizophrenia and 14 matched controls. Images were acquired on a 3 Tesla Siemens scanner using compressed image acquisition to allow for cued overt word production. Subjects alternated between OS, SC, OS-switch, SC-switch, and baseline blocks. Images were pre-processed in SPM-2, and a two-stage random effects analysis tested within and between group contrasts. There were no group performance differences. fMRI analysis did not reveal any group differences during the OS non-switching condition. Both groups produced expected activation in bilateral prefrontal and inferior parietal regions. However, during the SC condition patients had greater activation than controls in left prefrontal, right anterior cingulate, right superior temporal, bilateral thalamus, and left parietal regions. There was also evidence of patient over-activation in prefrontal, superior temporal, superior parietal, and visual association areas when a switching component was added. FTD was negatively correlated with BOLD response in the right anterior cingulate, cuneus and superior frontal gyrus during increased retrieval demand, and positively correlated with fMRI activation in the left lingual gyrus, right fusiform gyrus and left superior parietal lobule during increased switching demand. These results indicate that patients are able to successfully perform effortful semantic fluency tasks during non-speeded conditions. When retrieval is relatively automatic there does not appear to be an effect of schizophrenia on fMRI response. However, when retrieval and controlled processing demands increase, patients have greater activation than controls despite unimpaired task performance. This inefficient BOLD response may explain why patients are slower and less accurate on standard self-paced fluency tasks.

fMRI investigation of the cognitive structure of the Concealed Information Test

We studied the cognitive basis of the functional magnetic resonance imaging (fMRI) pattern of deception in three participants performing the Concealed Information Test (CIT). In all participants, the prefrontoparietal lie activation was similar to the pattern derived from the meta-analysis (N = 40) of our previously reported fMRI CIT studies and was unchanged when the lie response was replaced with passive viewing of the target items. When lies were replaced with irrelevant responses, only the left inferior gyrus activation was common to all subjects. This study presents a systematic strategy for testing the cognitive basis of deception models, and a qualitative approach to single-subject truth-verification fMRI tests.

Are neurologic examination abnormalities heritable? A preliminary study

BACKGROUND

Neurologic examination abnormalities (NEA) are more prevalent among patients with schizophrenia as well as their unaffected relatives when compared with healthy controls, suggesting that NEA may be endophenotypes for schizophrenia. We estimated the heritability of NEA in moderately sized pedigrees. We also evaluated correlations between NEA and cognitive performance in order to examine their construct validity.

METHODS

Members of eight extended families, each consisting of two first degree relatives with schizophrenia/schizoaffective disorders, as well as available first- to fifth-degree relatives were examined (n=96 participants). A modification of the Neurological Evaluation Scale (NES) was employed, augmented with localizing signs. Where feasible, we used untransformed data such as error counts and completion time, rather than ordinal measures. Heritability was estimated using the variance component method, implemented in SOLAR.

RESULTS

Statistically significant heritability (h2) estimates were obtained for several measures (p<0.05, h2+/-standard error: rapid alternating movements, right-sided completion time, 0.99+/-0.19; alternating fist-palm test, completion time, 0.77+/-0.19 s, errors, 0.70+/-0.32; fist-ring test, right-sided completion time, 0.53+/-0.23 s, left-sided completion time, 0.70+/-0.21 s; go-no go task, correct responses, 0.93+/-0.33; audio-visual integration, correct responses, 0.79+/-0.54). For most items, heritability analysis was hampered by insufficient data variability (infrequent errors). Correlational analyses show some degree of divergence among types of NEA, repetitive motor tasks being associated with most domains of cognitive functioning other than executive functioning, and cognitive-perceptual tasks being associated with memory and executive functioning.

CONCLUSIONS

Significant familial influences on certain aspects of neurologic performance were detected. These heritable measures were also correlated with heritable neurocognitive measures.

Normative neuropsychological test performance: effects of age, education, gender and ethnicity

Normative data on neuropsychological test performance for a sample of 131 adults (ages 18-49) is presented. All subjects were native speakers of English screened for past or present medical, neurological and psychiatric disorders, including substance abuse. A broad-based battery including measures of intellectual skills, memory and learning, receptive and expressive language, auditory and visual information processing and attention, sensory processing, motor skills, and self-reported anxiety and depression was administered. Means, standard deviations and percentile rankings for all tests are reported. Regression analyses were computed to consider the concurrent influence of sociodemographic factors on all tests. Significant effects of age (M=27.1 yrs), education (M=14.6 yrs), gender (58% male), and ethnicity (62% white) were observed for relatively few test scores. Younger age at testing was associated with better continuous performance test scores. Higher education levels were associated with higher vocabulary and reading scores. Males had higher WAIS-R Information scores and faster Finger Tapping scores compared to females Ethnicity was associated with Full-scale IQ, and additional tests with a verbal component, e.g., Boston Naming Tests, and non-verbal component, e.g., Drawing Tests. We conclude that sociodemographic factors infrequently account for more than 10% of the variance for many neuropsychological test scores.

Classifying spatial patterns of brain activity with machine learning methods: application to lie detection

Patterns of brain activity during deception have recently been characterized with fMRI on the multi-subject average group level. The clinical value of fMRI in lie detection will be determined by the ability to detect deception in individual subjects, rather than group averages. High-dimensional non-linear pattern classification methods applied to functional magnetic resonance (fMRI) images were used to discriminate between the spatial patterns of brain activity associated with lie and truth. In 22 participants performing a forced-choice deception task, 99% of the true and false responses were discriminated correctly. Predictive accuracy, assessed by cross-validation in participants not included in training, was 88%. The results demonstrate the potential of non-linear machine learning techniques in lie detection and other possible clinical applications of fMRI in individual subjects, and indicate that accurate clinical tests could be based on measurements of brain function with fMRI.

Cognitive performance of male adolescents is lower than controls across psychiatric disorders: a population-based study

OBJECTIVE

Psychiatric patients, as well as humans or experimental animals with brain lesions, often concurrently manifest behavioral deviations and subtle cognitive impairments. This study tested the hypothesis that as a group, adolescents suffering from psychiatric disorders score worse on cognitive tests compared with controls.

METHOD

As part of the assessment for eligibility to serve in the military, the entire, unselected population of 16-17-year old male Israelis undergo cognitive testing and screening for psychopathology by the Draft Board. We retrieved the cognitive test scores of 19 075 adolescents who were assigned any psychiatric diagnosis, and compared them with the scores of 243 507 adolescents without psychiatric diagnoses.

RESULTS

Mean test scores of cases were significantly poorer then controls for all diagnostic groups, except for eating disorders. Effect sizes ranged from 0.3 to 1.6.

CONCLUSION

As group, adolescent males with psychiatric disorders manifest at least subtle impairments in cognitive functioning.

Brain activity during simulated deception: an event-related functional magnetic resonance study

TheGuilty Knowledge Test (GKT) has been used extensively to model deception. An association between the brain evoked response potentials and lying on the GKT suggests that deception may be associated with changes in other measures of brain activity such as regional blood flow that could be anatomically localized with event-related functional magnetic resonance imaging (fMRI). Blood oxygenation level-dependent fMRI contrasts between deceptive and truthful responses were measured with a 4 Tesla scanner in 18 participants performing the GKT and analyzed using statistical parametric mapping. Increased activity in the anterior cingulate cortex (ACC), the superior frontal gyrus (SFG), and the left premotor, motor, and anterior parietal cortex was specifically associated with deceptive responses. The results indicate that: (a) cognitive differences between deception and truth have neural correlates detectable by fMRI, (b) inhibition of the truthful response may be a basic component of intentional deception, and (c) ACC and SFG are components of the basic neural circuitry for deception.

Effectiveness of an attention- and memory-training program on neuropsychological deficits in schizophrenia

The effect of two cognitive remediation procedures developed for closed head injury, Attention Process Training (APT) and Prospective Memory Training (PROMT), on neuropsychological deficits in schizophrenia was investigated. Six patients with schizophrenia, varying in baseline intellectual function and symptoms, were studied; three in a remediation condition and three in a nonremediated control condition. Results were evaluated individually for each of the three treated patients. Two of three remediation-treated subjects showed marked improvement on tests of sustained and divided attention. Untreated patients showed little evidence of change in neuropsychological test performance across a similar time interval, when tested on a subset of the measures administered to remediation-treated patients. The results of this study are discussed with a view toward future studies using larger sample sizes with homogeneous subject populations.

Approaches to cognitive remediation of neuropsychological deficits in schizophrenia: a review and meta-analysis

A review and critique of the literature pertaining to the use of cognitive remediation techniques in patients with schizophrenia is presented. The review is organized into three sections, according to the neuropsychological deficit targeted for remediation: 1) executive-function, 2) attention, and 3) memory. With regards to executive-function, despite an initial report suggesting that Wisconsin Card Sorting Test performance cannot be remediated, subsequent studies suggest that performance can be improved on a variety of dependent measures including perseverative errors, categories achieved, and conceptual level responses. These observations were confirmed by a meta-analytic investigation that revealed large mean effects sizes (d+ = 0.96) for these studies. Effect sizes were homogenous across discrepant remediation strategies and dependent measures. With regards to attention, serial scanning can be improved with instruction and reinforcement, whereas there is mixed evidence suggesting that practice-based attention drills can improve performance on measures of sustained attention in schizophrenia. With regards to memory, relatively simple semantic and affective elaborate encoding strategies elevates verbal list-learning memory in patients with schizophrenia to levels consistent with controls. A similar encoding procedure, combined with vigilance training, produces substantial improvement in social cue recognition. Avenues for future research are discussed.

Computerized neurocognitive scanning: II. The profile of schizophrenia

Cognitive dysfunction in schizophrenia is well established with neuropsychological batteries, which have assessed multiple domains indicating diffuse deficits especially in processing related to frontotemporal systems. Two studies are reported examining the feasibility of the computerized neurocognitive scan to assess differential deficits in schizophrenia. In Study 1, we tested 53 patients and 71 controls with the traditional and computerized assessments counterbalanced in order. Both showed comparable generalized impairment in schizophrenia with differential deficits in executive functions and memory. The profile was replicated in Study 2 in a new sample of 68 patients and 37 controls, receiving only the computerized scan. The combined sample showed robust correlations between performance on both speed and accuracy measures of the neurocognitive scan and clinical variables, including premorbid adjustment, onset age, illness duration, quality of life, and severity of negative symptoms. These correlations were higher and more prevalent in women than men, who showed correlations predominantly for speed rather than accuracy. Neuroleptic exposure was associated with poorer performance only for speed of memory processing, and in men, this association was seen only for typical neuroleptics. We conclude that the computerized neurocognitive scan can be applied reliably in people with schizophrenia, yielding data that support its construct and criterion validity.

Computerized neurocognitive scanning: I. Methodology and validation in healthy people

Neuropsychological testing batteries are applied in neurobehavioral evaluations of brain disorders, including neuropsychiatric populations. They are lengthy, require expert administrators and professional scorers, and are prone to data handling errors. We describe a brief computerized neurocognitive "scan" that assesses similar domains with adequate reliability. The scan and a traditional battery were administered to a sample of 92 healthy individuals (44 men, 48 women) in a counterbalanced order. Both approaches showed a significant "sex-typical" gradient, with women outperforming men in verbal memory relative to spatial tasks. Both methods also yielded similar profiles of sex differences, with the additional computerized measure of face memory showing better performance in women. Age effects were evident for both methods, but the computerized scan isolated the effects to speed rather than accuracy. Therefore, the computerized scan has favorable reliability and construct validity and can be applied efficiently to study healthy variability related to age and gender.

Controlled and automatic processing during animal word list generation in schizophrenia

Controlled and automatic aspects of semantic-associative functioning in schizophrenia were investigated by evaluating performance on animal word list generation (WLG). Responses from control (n = 47) and patient (n = 38) participants were subjected to multidimensional scaling (MDS), cluster analysis (CA), and indices on the basis of number of shared attributes (SA) between consecutive responses. Patient MDS results accounted for less variance and contained more error than control data. CA results yielded fewer and less clear animal-response subgroups among patients yet demonstrated intact associations among strongly related exemplars. The SA indices revealed better clustering and more effective switching among response clusters in controls than patients. Results suggest that animal WLG in schizophrenia is compromised both by aberrant automatic semantic-associative network activation and by controlled processes such as search, access, and selection. This pattern is consistent with prominent frontotemporal pathology evident in the disorder.

Neuropsychological differences among empirically derived clinical subtypes of schizophrenia

Neuropsychological profile differences between empirically derived clinical subtypes of schizophrenia were examined. Two hundred five patients and 209 demographically matched controls were administered a neuropsychological battery examining 8 domains. Subtypes included negative, disorganized, paranoid, Schneiderian, and mild. All subtypes displayed a neuropsychological profile of generalized impairment with greater deficits in learning, memory, and attention. Results were suggestive of diffuse cognitive dysfunction in schizophrenia with more severe deficits in learning and memory relative to executive skills. This pattern of greater learning and memory impairment was pronounced for disorganized patients. In contrast, paranoid patients outperformed disorganized and negative patients in several domains. These findings reflect bilateral frontal-temporal dysfunction, particularly in disorganized and negative patients. Subtype differences highlight the importance of conceptualizing schizophrenia as a multifocal disorder.

Striatal dopamine transporters and cognitive functioning in healthy men and women

OBJECTIVE

There is growing interest in distinguishing the biological bases of sex differences in behavior from environmental influences. Sex hormone levels seem to be related to some cognitive abilities, particularly memory, and the dopaminergic system participates in the mediation of memory. The dopamine transporter is the primary indicator of dopaminergic tone. This study investigated the relationship between cognition and dopamine transporter availability in healthy men and women.

METHOD

Dopamine transporter levels were measured with a technetium-99m radiolabeled analog of cocaine, TRODAT-1, in 66 healthy volunteers (30 men and 36 women). A neuropsychological battery designed to target functions associated with dopaminergic activity was administered during the uptake interval between the radiopharmaceutical injection and image acquisition.

RESULTS

Women and younger participants had higher dopamine availability in the caudate nucleus, and these groups also performed better on verbal learning tasks. Furthermore, dopamine transporter availability was correlated with learning performance within groups. Relationships between dopamine availability in the caudate and putamen and executive and motor functioning were observed in women, but not in men.

CONCLUSIONS

The results provide further evidence for age effects and sex differences in the neuromodulatory influences of dopamine on behavior in humans.

Effect of schizophrenia on frontotemporal activity during word encoding and recognition: a PET cerebral blood flow study

OBJECTIVE

Neuropsychological studies have shown that deficits in verbal episodic memory in schizophrenia occur primarily during encoding and retrieval stages of information processing. The current study used positron emission tomography to examine the effect of schizophrenia on change in cerebral blood flow (CBF) during these memory stages.

METHOD

CBF was measured in 23 healthy comparison subjects and 23 patients with schizophrenia during four conditions: resting baseline, motor baseline, word encoding, and word recognition. The motor baseline was used as a reference that was subtracted from encoding and recognition conditions by using statistical parametric mapping.

RESULTS

Patients' performance was similar to that of healthy comparison subjects. During word encoding, patients showed reduced activation of left prefrontal and superior temporal regions. Reduced left prefrontal activation in patients was also seen during word recognition, and additional differences were found in the left anterior cingulate, left mesial temporal lobe, and right thalamus. Although patients' performance was similar to that of healthy comparison subjects, left inferior prefrontal activation was associated with better performance only in the comparison subjects.

CONCLUSIONS

Left frontotemporal activation during episodic encoding and retrieval, which is associated with better recognition in healthy people, is disrupted in schizophrenia despite relatively intact recognition performance and right prefrontal function. This may reflect impaired strategic use of semantic information to organize encoding and facilitate retrieval.

Age-related volumetric changes of brain gray and white matter in healthy infants and children

To date there is little information about brain development during infancy and childhood, although several quantitative studies have shown volume changes in adult brains. We performed three-dimensional magnetic resonance imaging (3D-MRI) in 28 healthy children aged 1 month to 10 years. We examined the volumes of whole brain and frontal and temporal lobes with an advanced method for segmenting images into gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF) compartments. Growth spurts of whole brain and frontal and temporal lobes could be seen during the first 2 years after birth. During this period the frontal lobes grew more rapidly than the temporal lobes, the right--left asymmetry was more noticeable in the temporal lobes than in the frontal lobes and the increase in GM was larger than that in WM in the temporal lobes. Subsequently, WM volume increased at a higher rate than GM volume throughout childhood. Quantitative information on normal brain development may play a pivotal role in clarifying brain neurodevelopmental abnormalities.

Comparison of the continuous performance test with and without working memory demands in healthy controls and patients with schizophrenia

The Penn Continuous Performance Test (PCPT), a measure of sustained visual attention developed for use in functional neuroimaging studies, was compared with a standard CPT developed by Gordon Diagnostic Systems (GDS; Vigilance subtest). The PCPT and the GDS CPT were administered with a standard neuropsychological battery to 68 healthy adults to assess reliability and construct validity. The test had adequate internal consistency, and convergent validity was established through significant correlations between measures of efficiency on the PCPT and the GDS CPT. With the exception of a significant correlation between efficiency measures on the GDS CPT and a measure of auditory sustained attention, neither version of the CPT correlated significantly with other measures in the battery. Factor analysis showed that the PCPT loaded with the GDS CPT. In 39 patients with schizophrenia and 39 matched, healthy controls, equivalent impairment was evident on the two CPT tasks. Neither version correlated significantly with symptom measurements. These results support previous conclusions that sustained visual attention in schizophrenia is a core information processing deficit, not directly related to symptomatology.

An fMRI study of sex differences in regional activation to a verbal and a spatial task

Sex differences in cognitive performance have been documented, women performing better on some phonological tasks and men on spatial tasks. An earlier fMRI study suggested sex differences in distributed brain activation during phonological processing, with bilateral activation seen in women while men showed primarily left-lateralized activation. This blood oxygen level-dependent fMRI study examined sex differences (14 men, 13 women) in activation for a spatial task (judgment of line orientation) compared to a verbal-reasoning task (analogies) that does not typically show sex differences. Task difficulty was manipulated. Hypothesized ROI-based analysis documented the expected left-lateralized changes for the verbal task in the inferior parietal and planum temporal regions in both men and women, but only men showed right-lateralized increase for the spatial task in these regions. Image-based analysis revealed a distributed network of cortical regions activated by the tasks, which consisted of the lateral frontal, medial frontal, mid-temporal, occipitoparietal, and occipital regions. The activation was more left lateralized for the verbal and more right for the spatial tasks, but men also showed some left activation for the spatial task, which was not seen in women. Increased task difficulty produced more distributed activation for the verbal and more circumscribed activation for the spatial task. The results suggest that failure to activate the appropriate hemisphere in regions directly involved in task performance may explain certain sex differences in performance. They also extend, for a spatial task, the principle that bilateral activation in a distributed cognitive system underlies sex differences in performance.