Friday, April 25, 2008

Neuronal activity related to faces and matching

Ojemann, J.G., Ojemann, G.A., & Lettich, E. (1992). Neuronal activity related to faces and matching in human right nondominant temporal cortex. Brain, 115, 1-13.

Using microelectrode recording, this group set out to look at changes in neuronal activity in response to faces, previously described in monkey cortex but not well established in humans. Recording was restricted to areas of right anterior temporal cortex that would be later resected in an epileptic lobectomy, areas that showed the least epileptic activity on electrocorticography. Seven neuronal populations related to face perception were identified. In addition, three other populations, only in middle temporal gyrus, increased activity with the labelling of the emotional expression of a face. The ease with which a given task can elicit specific, temporally-coupled changes in neuronal activity suggest that human association cortex is compartmentalized into behaviorally specific systems.

Friday, April 18, 2008

Addressing Psychosocial Problems at Work

Probst, T.M. et al. (2008). A preliminary evaluation of SOLVE: Addressing Psychosocial Problems at Work. Journal of Occupational Health Psychology, Vol. 13, No. 1, 32-42.

SOLVE is a workplace intervention program implemented by many companies worldwide which aims to address the interrelated issues of job stress, workplace violence, tobacco use, drug and alcohol abuse, and HIV/AIDS. Psychosocial issues tend to coexist, e.g. stress leads to workplace hostility which spills over into home life and often results in poor coping strategies. SOLVE is based on cognitive behavioral therapy (CBT) models, which believe that behavior is influenced by cognitions, knowledge is necessary for behavioral change, and both are broadly influenced by dynamic interactions between numerous forces. Therefore, SOLVE attempts to make individuals aware of threats and their consequences, make them aware of benefits of the touted strategies, and provide specific information for tackling the health-related issues, while being both person- and organization-directed. Although SOLVE is used widely, its efficacy has not been evaluated. Current studies demonstrate improvements in knowledge among participants across locale which is encouraging. However, they do not assess attitudinal or behavioral changes, or bottom-line benefits to the organization.

Thursday, April 17, 2008

The Visual Cliff

Gibson, E.J. & Walk, R.D. (April 1960). The "Visual Cliff". Scientific American.

To investigate depth perception in human and animal species, these authors created the "visual cliff" which allowed them to experimentally adjust the optical and tactical stimuli associated with a simulated cliff while protecting the subjects from injury. They discovered that all species can perceive and avoid a sharp drop by the time they take up independent locomotion, be it at Day 1 in chicks, 4 weeks in rats, or 6 months in humans. Most rely on visual cues for depth perception. The rat, however, relies predominantly on tactual cues (being nocturnal) but will fall back on sound vision when needed. Next, the experimenters wanted to find out which visual cues played the decisive role in depth perception. Using dark-reared animals, they concluded motion parallax is an innate cue for depth discrimination, whereas responses to differential pattern-density may be learned later.

(I, Doug G, am the author of this article, The Visual Cliff, and I release its content under the terms of the GNU Free Documentation License, Version 1.2 and later.)

Web-based Methods in Terrorism and Disaster Research

Schlenger, W.E. & Silver, R.C. (April 2006). Web-based Methods in Terrorism and Disaster Research. Journal of Traumatic Stress, Vol. 26, No. 2, 185-193.

Gaining access to a traumatized population in the aftermath of a disaster can be challenging. The need for rapid response and appropriate probability sampling along with the observational nature of the studies (i.e. no random assignment) and post-only design can be problematic for the generalizability of the results. Recently, web-based methods have helped to address some of these age-old issues. (1) The literature indicates that people respond more honestly to sensitive questions in self-report than in interview-based assessments. (2) The use of e-mail also assists greatly with retention rates in longitudinal studies. (3) Respondents can answer surveys within the privacy of their home at a time that is convenient to them. (4) Question delivery can be standardized. (5) Time-consuming and error-prone steps of data coding and entry are eliminated. (6) And most importantly, recent companies such as Knowledge Networks Inc. have recruited nationally representative probability samples for just such uses. Panels can even be created in advance of disasters, enabling premeasure to be linked to postevent responses. However, these new technologies are not without their issues, e.g. populations may suffer infrastructure disruptions due to disaster that render data collection impossible such as in Hurricane Katrina.

The Early Origins of Autism

Rodier, P.M. (February 2000). The Early Origins of Autism. Scientific American.

Miller and Stromland made a surprising observation that 5% of thalidomide victims had autism, a rate about 30 times higher than the rate among the general population. This suggested that autism originates in the early weeks of pregnancy when the nervous system is just beginning to develop. Examining these victims' specific malformations indicated that their development had been impacted about 20-24 days into gestation, before many pregnant women even know they are pregnant. This was way earlier than investigators would have guessed, since very few neurons are even formed by the 4th week. However, most are the motor nerves of the cranial nerves in the brain stem. And indeed, many subjects with autism exhibit abnormalities of eye movement and lack of facial expression, consistent with this observation.

However, it is more likely that these early brain injuries affect more than just the function of the cranial nerve, and may interfere with proper development or wiring of other brain regions in turn. People with autism consistently show a reduction in the number of neurons in the cerebellum of the brainstem, a structure typically thought to involved in fine motor control but also seen activated during certain tasks requiring high-level cognitive processing. Some people with autism also display marked decreases in the facial nucleus (controls muscles of facial expression) and superior olive (a relay station for auditory information). Interestingly, "knock-out" mice engineered to lack the expression of the gene known as Hoxa1 (active when brainstem neurons are forming), show all of these symptoms. While variant alleles of Hoxa1 have been identified, these are only one of many genes involved in the spectrum of autism disorder. Other genes must be found which also increase the risk (or decrease the risk) of developing the disorder.

Wednesday, April 16, 2008

Coping with stress in different phases of romantic development

Nieder, T. & Seiffge-Krenke, I. (2001). Coping with stress in different phases of romantic development. Journal of Adolescence, 24, 297-311.

This study followed adolescents longitudinally between ages 14 and 17, annually measuring their quality of relationships, their stress levels, and their coping styles. The results taken together provide support for a developmental sequence in romantic development. The percent of participants in a relationship increased over this time period, and the durations of these relationships increased with time. With this came increases in depth -- intimacy, affection, and extent of sexual activity. Romantic stress was highest in earlier years stemming from diverse sources, later decreasing and stabilizing with age. And active coping with romantic stress was lowest initially and significantly increased at 15, remaining high. As romantic relationships develop, stress is more and more related to conflicts between the romantic partners; yet such conflicts are increasingly resolved by dyadic communication as a coping strategy. Surprisingly, the development of a more active coping style over time was not associated with the decrease in amount of romantic stress. Instead, intimacy and affection is consistently associated with reduced stress, suggesting that as the relationship matures over time romantic stress decreases.

Monday, April 7, 2008

HPA Axis, neuroendocrine factors, and stress

Tsigos, C. & Chrousos, G.P. (2002). Hypothalamic-pituitary-adrenal axis, neuroendocrine factors, and stress. Journal of Psychosomatic Research, 53, 865-871.

Psychology is concerned with the transactions and interactions we have with the world. Stress research examines how we respond to transactions that are stressful. This paper does a great job to illustrate the complexity of our physiological responses to stressors.

CRH/AVP. The paper begins with our physiological response following detection of a stressor. CRH and AVP are secreted into a special portal system and activate neurons of the paraventricular nuclei (PVN) of the hypothalamus, which primarily kicks off activation of the greater hypothalamic-pituitary-adrenal (HPA) axis.

LC/NE system. The locus ceruleus and other noradrenergic cell groups of the medulla and pons, collectively known as the LC/NE system, serve as a global alarm system, using brain epinephrine to execute autonomic and neuroendocrine responses.

The autonomic axis. The ANS provides rapid response to stress, engaging the SNS and withdrawing the PSNS, and enacting cardiovascular, respiratory, gastrointestinal, renal, and endocrine changes.

The HPA Axis. CRH and AVP normally follow certain circadian rhythms, with increasing pulses seen in the early morning hours and decreasing throughout the day. During acute stress, pulsations in this portal system markedly increase, resulting in release of ACTH from the pituitary into the general bloodstream, which finally results in secretion of cortisol and other glucocorticoids from the adrenal cortex. These corticoids involve the whole body in the organism's response to stress and ultimately contribute to the termination of the response via inhibitory feedback.

Other changes. Concomitant with the aforementioned changes, the sympathetic-adrenomedullary system (SAM) influences the body organs, and vagal and sacral parasympathetic responses are also instantiated mediating our gut responses to stress.

The paper also goes into advanced topics including interactions that exist between the HPA axis and the immune system, interactions between the HPA and the gonadal and growth axes, and interactions between the HPA and metabolism. It also discusses pathologies related to the HPA axis. A spectrum of conditions may be associated with increased and prolonged activation of the HPA axis, including melancholic depression, anorexia nervosa, OCD, panic anxiety, excessive exercising, and childhood sexual abuse. Another group of conditions may be associated with hypoactivation of the stress system, including atypical depression, seasonal depression, and chronic fatigue syndrome. Antalarmin, a CRH-R1 antagonist, was also mentioned as being a potentially important drug to combat HPA axis disorders characterized by HPA and LC/NE hyperactivity in the future.

Friday, April 4, 2008

Language Interpretation and the Immediacy Assumption

Hagoort, P. & von Berkum, J. (April 3, 2007). Beyond the sentence given. Philosophical Transactions of the Royal Society, 362, 801-811.

The view that language interpretation takes place in a two-step process has predominated, with the meaning of the sentence being computed first and the sentence meaning then being integrated with other sources of information (e.g. context, world knowledge). However, event-related brain potentials (ERPs) appear to be inconsistent with this model, finding strong empirical evidence that linguistic and extra-linguistic information are integrated in the same time-frame during sentence interpretation. Similar latencies and amplitudes of the N400 effect witnessed for all types of semantic mismatches support the immediacy assumption, that disparate information is brought to bear on language interpretation as soon as it becomes available. Neuroimaging studies suggest that the left inferior frontal cortex, including Broca's area, is an important node in the semantic unification network, and that this area is not language specific but acts as a single integration space.