Serotonergic dysfunction: Brain imaging and behavioral correlates

Identification of gene-environment and gene-gene interactions has become increasingly important in understanding psychiatric disorders. Dysfunction of central serotonergic neurotransmission has been implicated in alcoholism, depression, and anxiety. We review the literature on nonhuman primates that assesses the interaction between the genetic constitution of the regulatory region of the serotonin transporter (5-HTT) and environmental factors. Prospective studies in nonhuman primates that underwent social stress found a reduction of the serotonin turnover rate among carriers of one or two short alleles in a functional polymorphism of the 5-HTT promoter. In these primates, brain imaging studies showed a relative increase in the availability of raphe serotonin transporters. A low serotonin turnover rate and a high availability of serotonin transporters were associated with reduced response to excessive alcohol intake, anxiety, and impulsive aggression. Animal experiments point to a relationship between serotonergic dysfunction, negative mood states, and excessive alcohol intake, which may in part be mediated by reduced alcohol-induced sedation.     

Brain imaging: Applications in psychiatry

For more than a century psychiatrists have suspected neuropathology in patients with mental illness. In the last decade there have been developed several technologies that are capable of looking at both neuroanatomy and neurophysiology in the brains of living humans. First, x-ray computerized axial tomography led the way in visualizing the living brain, and now magnetic resonance imaging allows brain structure to be shown with even more clarity. Brain electrical activity mapping allows computerized maps of electrophysiological activity to be visualized in a way never before possible. Nuclear medicine has provided the means of looking at various metabolic and neurochemical parameters in the living brain. These include regional cerebral blood flow studies using xenon¹³³, single photon emission tomography, and positron emission tomography. Psychiatrists are cautiously optimistic that these various brain imaging technologies will be important new tools in continued exploration of the causes of mental illness and ultimately may lead to more effective treatments.     

Digital filters in behavioral research

Behavioral control is almost always less than perfect. Rate of response is rarely as constant as it could be even when the greatest care is given to experimental procedures. Experimenters should always attempt to identify the causes of variation. Some fluctuations in response rate will be random, i.e., sometimes positive and sometimes negative, usually small but occasionally large. Digital filters are objective methods for reducing or eliminating such unsystematic “noise” components while preserving the systematic changes in response rate under study. Digital filters function in a manner that is strictly analogous to electronic filters. The major purpose of this technical note is to describe digital filters and to provide an example of their usage.     

Interface systems in behavioral research

The methods and criteria to be used for the design of a general interface system are evaluated in the light of the number, variety, and variability of the data points in behavioral experimentation. A simple and flexible interface scheme is presented that should satisfy the needs of a behavioral research laboratory.     

Brain imaging techniques in the diagnosis of dementia

Various recently developed brain imaging techniques used to assist in the diagnosis of dementia are reviewed. The methods reviewed are x-ray computed tomography scan imaging, magnetic resonance imaging, positron emission tomography, and the older techniques of pneumoencephalography and radioisotope cisternography. It was concluded that while these techniques often offer excellent diagnostic information, none of them provides a definitive characteristic image for Alzheimer's disease.     

Mediation of artifacts in behavioral research

An integrative artifact model is developed from a combination of role theory and McGuire's information-processing theory of social influence. The main extraneous sources of systematic error are reduced to three conjoint mediators, the end product of which determines the likelihood that a subject will positively or negatively react to demand characteristics. Conditions thought to affect the mediating variables are noted, and the practical advantage of this combinatory view is discussed as it applies to estimating the inferential validity of experimental findings in psychology.     

Internet research: an opportunity to revisit classic ethical problems in behavioral research

The Internet offers many new opportunities for behavioral researchers to conduct quantitative and qualitative research. Although the ethical guidelines of the American Psychological Association generalize, in part, to research conducted through the Internet, several matters related to Internet research require further analysis. This article reviews several fundamental ethical issues related to Internet research, namely the preservation of privacy, the issuance of informed consent, the use of deception and false feedback, and research methods. In essence, the Internet offers unique challenges to behavioral researchers. Among these are the need to better define the distinction between private and public behavior performed through the Internet, ensure mechanisms for obtaining valid informed consent from participants and performing debriefing exercises, and verify the validity of data collected through the Internet.     

Multisensory processing in the redundant-target effect: a behavioral and event-related potential study

Participants respond more quickly to two simultaneously presented target stimuli of two different modalities (redundant targets) than would be predicted from their reaction times to the unimodal targets. To examine the neural correlates of this redundant-target effect, event-related potentials (ERPs) were recorded to auditory, visual, and bimodal standard and target stimuli presented at two locations (left and right of central fixation). Bimodal stimuli were combinations of two standards, two targets, or a standard and a target, presented either from the same or from different locations. Responses generally were faster for bimodal stimuli than for unimodal stimuli and were faster for spatially congruent than for spatially incongruent bimodal events. ERPs to spatially congruent and spatially incongruent bimodal stimuli started to differ over the parietal cortex as early as 160 msec after stimulus onset. The present study suggests that hearing and seeing interact at sensory-processing stages by matching spatial information across modalities.     

Real-time clocks for microcomputers in behavioral research

Real-time clock strategies are described for microcomputers in behavioral research. Software-oriented and hardware-oriented counters are described in both free-running and strobed modes. An example of a clock using the Intel 8253 is given, along with driving software in 8080 assembly code and hardware for the S-100 bus.     

Computerized process control in behavioral science research

A general approach to the design and development of real-time operating systems is discussed. Operating system design for small to medium scale laboratory computers is described at a moderately elementary level. Analysis of system design as a supervisory control hierarchy is presented in an attempt to bridge the gap between an elementary general understanding of computer operation and the more sophisticated understanding assumed by the writers of most computer systems operator’s manuals. PROSS, a programming language developed at Indiana University, is presented as an example of the highest level of supervisory control.     

Some unsettled problems in behavioral neuroscience research

The goal of behavioral neuroscience is to map psychological concepts onto physiological and anatomical concepts and vice versa. The present paper reflects on some of the hidden obstacles that have to be overcome in order to find unique psychophysiological relationships. These are, among others: (1) the different status of concepts which are defined in the two domains (ontological subjectivity in psychology and ontological objectivity in physiology); (2) the distinct hierarchical levels to which concepts from the two domains may belong; (3) ambiguity of concepts, because—due to limited measurement resolution or definitional shortcomings—they sometimes do not cover unique states or processes; (4) ignored context dependencies. Moreover, it is argued that due to the gigantic number of states and state changes, which are possible in a nervous system, it seems unlikely that neuroscience can provide exact causal explanations and predictions of behavior. Rather, as in statistical thermodynamics the transition from the microlevel of explanations to the macrolevel is only possible with probabilistic uncertainty.     

Brain imaging of tongue-twister sentence comprehension: twisting the tongue and the brain

This study used fMRI to investigate the neural basis of the tongue-twister effect in a sentence comprehension task. Participants silently read sentences equated for the syntactic structure and the lexical frequency of the constituent words, but differing in the proportion of words that shared similar initial phonemes. The manipulation affected not only the reading times and comprehension performance, but also the amount of activation seen in a number of language-related cortical areas. The effect was not restricted to cortical areas known to be involved in articulatory speech programming or rehearsal processes (the inferior frontal gyrus and anterior insula), but also extended to areas associated with other aspects of language processing (inferior parietal cortex) associated with phonological processing and storage.     

New directions in behavioral process research: Implications for social psychology

Current theories of social judgment and social decision making emphasize dynamic process perspectives, but the methods used to investigate these processes have been relatively static and limited in scope. This paper describes a set of evolving procedures designed to capture process data and discusses how this approach may be used to study various psychological phenomena, including control schemata, attribution theory, attitude formation, impression formation, implicit personality theory, verbal report accuracy, postdecision dissonance reduction, attraction, choice behavior, time constraints, gender stereotypes, agenda effects, and task feedback effects.     

Broadening behavioral decision research: Multiple levels of cognitive processing

The area of behavioral decision research—specifically, the work on heuristics and biases—has had a tremendous influence on basic research, applied research, and application over the last 25 years. Its unique juxtaposition against economics has provided important benefits, but at the cost of leaving it disconnected from too much of psychology. This paper explores an expanded definition of behavioral decision research through the consideration of multiple levels of cognitive processing. Rather than being limited to how decision makers depart from optimality, we offer a broader analysis of how decision makers define the decision problem and link decisions to goals, as well as a more detailed focus on processes associated with implementing decisions.     

Brain imaging in catatonia: current findings and a pathophysiologic model

Karl Ludwig Kahlbaum originally described catatonia as a psychomotor disease that encompassed motor, affective, and behavioral symptoms. In the beginning of the 20th century, catatonia was considered to be the motoric manifestation of schizophrenia; therefore, neuropathologic research mostly focused on neuroanatomic substrates (ie, the basal ganglia underlying the generation of movements). Even though some alterations were found in basal ganglia, the findings in these subcortical structures are not consistent. Recently, there has been a reemergence of interest into researching catatonia. Brain imaging studies have shown major and specific alterations in a right hemispheric neural network that includes the medial and lateral orbitofrontal and posterior parietal cortex. This neural network may be abnormally modulated by altered functional interactions between gamma-aminobutyric acid (GABA)-ergic and glutamatergic transmission. This may account for the interrelationship among motor, emotional, and behavioral alterations observed in both clinical phenomenology and the subjective experiences of patients with catatonia. Such functional interrelationships should be explored in further detail in catatonia, which may also serve as a paradigmatic model for the investigation of psychomotor and brain function in general.     

How to consistently link extraversion and intelligence to the catechol-O-methyltransferase (COMT) gene: on defining and measuring psychological phenotypes in neurogenetic research

The evidence for associations between genetic polymorphisms and complex behavioral/psychological phenotypes (traits) has thus far been weak and inconsistent. Using the well-studied Val158Met polymorphism of the catechol-O-methyltransferase (COMT) gene as an example, we demonstrate that using theoretical models to guide phenotype definition and measuring the phenotypes of interest with a high degree of specificity reveals strong gene-behavior associations that are consistent with prior work and that would have otherwise gone unnoticed. Only after statistically controlling for irrelevant portions of phenotype variance did we observe strong (Cohen's d = 0.33-0.70) and significant associations between COMT Val158Met and both cognitive and affective traits in a healthy male sample (N = 201) in Study 1: Carriers of the Met allele scored higher in fluid intelligence (reasoning) but lower in both crystallized intelligence (general knowledge) and the agency facet of extraversion. In Study 2, we conceptually replicated the association of COMT Val158Met with the agency facet of extraversion after partialing irrelevant phenotype variance in a female sample (N = 565). Finally, through reanalysis of a large published data set we showed that Met allele carriers also scored higher in indicators of fluid intelligence after partialing verbal fluency. Because the Met allele codes for a less efficient variant of the enzyme COMT, resulting in higher levels of extrasynaptic prefrontal dopamine, these observations provide further support for a role for dopamine in both intelligence and extraversion. More importantly, the present findings have important implications for the definition of psychological phenotypes in neurogenetic research.     

VRVision: A new tool for the display of 3-D images in behavioral research

Researchers using three-dimensional (3-D) scenes in their studies often spend a lot of time prerendering the scenes into a set of images for later presentations. To improve efficiency, we have developed a new plugin program for MATLAB that eliminates this step. The program is able to manipulate and present 3-D scenes in real time. It allows fine control over numerous parameters, including the mode of projection, angular rotation, lighting, surface photo textures, and animation. Images can be presented with monoscopic or stereoscopic display. It can also dynamically track viewer position and update and display an appropriate 3-D projection. The program is fully compatible with existing MATLAB utilities such as the Psychophysics Toolbox (psychtoolbox.org). It is made freely available to the research community (www.hive.hull .ac.uk/software/vrvision).