Dendritic asymmetry cannot account for directional responses of neurons in visual cortex

Long-term sequelae of prefrontal cortex damage acquired in early childhood

Frontal lobe dysfunction is often invoked as a contributing factor in developmental disorders characterized by chronic maladaptive behavior, but interpretation of relevant neuropsychological findings has been hampered by the limited information available regarding the consequences of focal prefrontal damage early in life. We describe here the long-term behavioral and cognitive sequelae of damage to prefrontal cortex in two young adult patients who had sustained their brain damage prior to 16 months of age. In the context of normal neurological examinations, both cases had remarkable histories of impaired decision making, behavioral dyscontrol, social defects, and abnormal emotion. Performances were primarily normal on a broad range of neuropsychological measures (intellect, memory, language, academic achievement, visual perception, and visuoconstruction), but selective impairments of executive function were evident. Early dysfunction in the prefrontal region may result in severe and chronic social maladjustment despite largely normal cognitive abilities. These findings can help inform neuropsychological evaluation of patients with possible prefrontal dysfunction in the setting of developmental disabilities or early brain trauma.

Effects of early onset brain injury on the development of cognition and behavior: introduction to the special issue

The effects of brain injury acquired early in life on the development of cognition and behavior are not well understood. Deciphering these effects and modeling their neurodevelopmental trajectories are major concerns for clinicians and scientists. Historically, a prevailing notion has been that early-onset brain damage has a more favorable prognosis than does brain damage acquired in adulthood. However, there is growing evidence suggesting that early-onset damage to prefrontal brain structures may have devastating consequences on the emergence of adaptive behavior throughout development. Particularly prominent are disorders of personality, social behavior, and executive functions such as planning and decision making. This special issue presents a series of new empirical studies that address these issues in depth, from several different perspectives, and in both human and animal participants. The findings promise to shed further light on both the neurobiology of development, and diverse neurodevelopmental disorders. Such advances may also enhance clinical diagnosis and facilitate the design of more effective interventions to help reduce the tremendous burden that neurodevelopmental disorders place on personal well-being, family structure, educational systems, and social resources.

An intervention for children with disorders of executive functions

This article describes a cognitive-behavioral approach to teaching metacognitive executive thinking strategies to children with disorders of executive function. The intervention is based on the notion that some children with disorders of executive function have disorders of higher level language, which predispose them to the executive impairments. It is proposed that teaching and reinforcing metacognitive thinking strategies may help advance verbal mediation of complex tasks and self-regulation of behavior. Despite the growing literature on developmental executive disorders, little has been written about interventions that may enable the children to acquire some of the requisite adaptive skills. The ideas expressed herein should be considered an invitation for the initiation of empirical studies of intervention and outcome effects.

Behavioral Aspects of Frontal Lobe Epilepsy

There is growing interest in disorders of behavior, personality, and mood associated with focal epilepsies, though the neuropsychological and behavioral or psychiatric aspects of epilepsy have usually been treated separately. The causes of behavioral disorders in patients with focal epilepsies are multifactorial, though the positive effects of seizure control on behavior suggest that state dependency is a major contributing factor. Patients with temporal lobe epilepsy manifest depression, anxiety, neuroticism, and social limitations, as well as impaired memory. By contrast, studies of cognitive function in patients with frontal lobe epilepsy show executive dysfunctions in response selection/initiation and inhibition, as well as cognitive impairment, hyperactivity, conscientiousness, obsession, and addictive behaviors.

The emotional dog and its rational tail: a social intuitionist approach to moral judgment

Research on moral judgment has been dominated by rationalist models, in which moral judgment is thought to be caused by moral reasoning. The author gives 4 reasons for considering the hypothesis that moral reasoning does not cause moral judgment; rather, moral reasoning is usually a post hoc construction, generated after a judgment has been reached. The social intuitionist model is presented as an alternative to rationalist models. The model is a social model in that it deemphasizes the private reasoning done by individuals and emphasizes instead the importance of social and cultural influences. The model is an intuitionist model in that it states that moral judgment is generally the result of quick, automatic evaluations (intuitions). The model is more consistent that rationalist models with recent findings in social, cultural, evolutionary, and biological psychology, as well as in anthropology and primatology.

The emotional modulation of cognitive processing: an fMRI study

The functional neuroanatomy of visual processing of surface features of emotionally valenced pictorial stimuli was examined in normal human subjects using functional magnetic resonance imaging (fMRI). Pictorial stimuli were of two types: emotionally negative and neutral pictures. Task performance was slower for the negatively valenced than for the neutral pictures. Significant blood oxygen level dependent (BOLD) increases occurred in the medial and dorsolateral prefrontal cortex, midbrain, substantia innominata, and/or amygdala, and in the posterior cortical visual areas for both stimulus types. Increases were greater for the negatively valenced stimuli. While there was a small but significant BOLD decrease in the subgenual prefrontal cortex, which was larger in response to the negatively valenced pictures, there was an almost complete absence of other decreases prominently seen during the performance of demanding cognitive tasks [Shulman, G. L., Fiez, J. A., Corbetta, M., Buckner, R. L., Miezin, F. M., Raichle, M. E., & Petersen, S. E. (1997). Common blood flow changes across visual tasks: II. Decreases in cerebral cortex. Journal of Cognitive Neuroscience, 9, 648--663]. These results provide evidence that the emotional valence and arousing nature of stimuli used during the performance of an attention-demanding cognitive task are reflected in discernable, quantitative changes in the functional anatomy associated with task performance.

Working memory of identification of emotional vocal expressions: an fMRI study

The distribution of brain activation during working memory processing of emotional vocal expressions was studied using functional magnetic resonance imaging (fMRI) in eight female subjects performing n-back tasks with three load levels (0-back, 1-back, and 2-back tasks). The stimuli in the n-back tasks were the Finnish female name [Saara] uttered in an astonished, angry, frightened, commanding, and scornful mode, and the subjects were instructed to memorize the emotional connotation of the stimuli. Subregions in the prefrontal, parietal, and visual association areas were load-dependently activated during the performance of the n-back tasks. The most consistently activated areas in the prefrontal region were detected in the inferior frontal gyrus corresponding to Brodmann's areas (BAs) 44 and 45 and in the middle and superior frontal gyri (BAs 6/8). Activation was also found in the inferior parietal lobe and intraparietal sulcus (BAs 40/7) and visual association areas including the lingual and fusiform gyri. The results suggest that a distributed neuronal network in occipital, parietal, and frontal areas is involved in working memory processing of emotional content of aurally presented information.

The neurobiology of social cognition

Recent studies have begun to elucidate the roles played in social cognition by specific neural structures, genes, and neurotransmitter systems. Cortical regions in the temporal lobe participate in perceiving socially relevant stimuli, whereas the amygdala, right somatosensory cortices, orbitofrontal cortices, and cingulate cortices all participate in linking perception of such stimuli to motivation, emotion, and cognition. Open questions remain about the domain-specificity of social cognition, about its overlap with emotion and with communication, and about the methods best suited for its investigation.

NEURON: a tool for neuroscientists

NEURON is a simulation environment for models of individual neurons and networks of neurons that are closely linked to experimental data. NEURON provides tools for conveniently constructing, exercising, and managing models, so that special expertise in numerical methods or programming is not required for its productive use. This article describes two tools that address the problem of how to achieve computational efficiency and accuracy.

Characterization of the decision-making deficit of patients with ventromedial prefrontal cortex lesions

On a gambling task that models real-life decisions, patients with bilateral lesions of the ventromedial prefrontal cortex (VM) opt for choices that yield high immediate gains in spite of higher future losses. In this study, we addressed three possibilities that may account for this behaviour: (i) hypersensitivity to reward; (ii) insensitivity to punishment; and (iii) insensitivity to future consequences, such that behaviour is always guided by immediate prospects. For this purpose, we designed a variant of the original gambling task in which the advantageous decks yielded high immediate punishment but even higher future reward. The disadvantageous decks yielded low immediate punishment but even lower future reward. We measured the skin conductance responses (SCRs) of subjects after they had received a reward or punishment. Patients with VM lesions opted for the disadvantageous decks in both the original and variant versions of the gambling task. The SCRs of VM lesion patients after they had received a reward or punishment were not significantly different from those of controls. In a second experiment, we investigated whether increasing the delayed punishment in the disadvantageous decks of the original task or decreasing the delayed reward in the disadvantageous decks of the variant task would shift the behaviour of VM lesion patients towards an advantageous strategy. Both manipulations failed to shift the behaviour of VM lesion patients away from the disadvantageous decks. These results suggest that patients with VM lesions are insensitive to future consequences, positive or negative, and are primarily guided by immediate prospects. This 'myopia for the future' in VM lesion patients persists in the face of severe adverse consequences, i.e. rising future punishment or declining future reward.

Untangling dendrites with quantitative models

Our understanding of the function of dendrites has been greatly enriched by an inspiring dialogue between theory and experiments. Rather than functionally ignoring dendrites, representing neurons as single summing points, we have realized that dendrites are electrically and chemically distributed nonlinear units and that this has important consequences for interpreting experimental data and for the role of neurons in information processing. Here, we examine the route to unraveling some of the enigmas of dendrites and highlight the main insights that have been gained. Future directions are discussed that will enable theory and models to keep shedding light on dendrites, where the most fundamental input-output adaptive processes take place.

A clinical profile to predict decision making, risk behaviors, clinical status, and health-related quality of life for cancer-surviving adolescents. Part 1

The purpose of this two-part series is to describe a multifactorial model of clinical factors predicting decision-making quality, risk behaviors, clinical status, and health-related quality of life for cancer-surviving adolescents. This model was developed as a clinical profile to help health professionals in better identifying cancer-surviving adolescents at highest risk for substance use. Findings in the literature and results from the program of research by the author are presented to support the conceptualization of the model. In part 1, support for the antecedent predictors, both primary and secondary factors, is presented. Part 2 addresses decision making as a mediator, risk motivation as a moderator, and the expected outcomes related to risk behaviors, clinical status, and quality of life. In addition to describing the first part of the clinical profile in part 1, the background, theoretical basis of the model, and definitions of the model constructs also are provided.

Prefrontal and medial temporal correlates of repetitive violence to self and others

BACKGROUND

The neurobiological basis for violence in humans is poorly understood, yet violent behavior (to self or others) is associated with large social and healthcare costs in some groups of patients (e.g., the mentally retarded). The prefrontal cortex and amygdalo-hippocampal complex (AHC) are implicated in the control aggression, therefore we examined the neural integrity of these regions in violent patients with mild mental retardation and nonviolent control subjects.

METHODS

We used (1)H-magnetic resonance spectroscopy (MRS) to measure 1) concentrations and ratios of N-acetyl aspartate (NAA), creatine phosphocreatine (Cr+PCr), and choline-related compounds (Cho) in prefrontal lobe of 10 violent inpatients and 8 control subjects; 2) ratios of NAA, Cr+PCr, and Cho in the AHC of 13 inpatients and 14 control subjects; and 3) frequency and severity of violence in patients.

RESULTS

Compared to control subjects, violent patients had significantly (p <.05, analysis of covariance-age and IQ as confounding covariates) lower prefrontal concentrations of NAA and Cr+PCr, and a lower ratio of NAA/Cr+PCr in the AHC. Within the violent patient group, frequency of observed violence to others correlated significantly with prefrontal lobe NAA concentration (r = -0.72, p <.05).

CONCLUSIONS

NAA concentration indicates neuronal density, and Cr+PCr concentration high-energy phosphate metabolism. Our findings suggest that violent patients with mild mental retardation have reduced neuronal density, and abnormal phosphate metabolism in prefrontal lobe and AHC compared to nonviolent control subjects. Further studies are needed, however, to determine if these findings are regionally specific, or generalize to other groups of violent individuals.

Experience-dependent asymmetric shape of hippocampal receptive fields

We propose a novel parameter, namely, the skewness, or asymmetry, of the shape of a receptive field to characterize two properties of hippocampal place fields. First, a majority of hippocampal receptive fields on linear tracks are negatively skewed, such that during a single pass the firing rate is low as the rat enters the field but high as it exits. Second, while the place fields are symmetric at the beginning of a session, they become highly asymmetric with experience. Further experiments suggest that these results are likely to arise due to synaptic plasticity during behavior. Using a purely feed forward neural network model, we show that following repeated directional activation, NMDA-dependent long-term potentiation/long-term depotentiation (LTP/LTD) could result in an experience-dependent asymmetrization of receptive fields.