Beyond monoamines: glutamatergic function in mood disorders

The monoamine theory has implicated abnormalities in serotonin and norepinephrine in the pathophysiology of major depression and bipolar illness and contributed greatly to our understanding of mood disorders and their treatment. Nevertheless, some limitations of this model still exist that require researchers and clinicians to seek further explanation and develop novel interventions that reach beyond the confines of the monoaminergic systems. Recent studies have provided strong evidence that glutamate and other amino acid neurotransmitters are involved in the pathophysiology and treatment of mood disorders. Studies employing in vivo magnetic resonance spectroscopy have revealed altered cortical glutamate levels in depressed subjects. Consistent with a model of excessive glutamate-induced excitation in mood disorders, several antiglutamatergic agents, such as riluzole and lamotrigine, have demonstrated potential antidepressant efficacy. Glial cell abnormalities commonly associated with mood disorders may at least partly account for the impairment in glutamate action since glial cells play a primary role in synaptic glutamate removal. A hypothetical model of altered glutamatergic function in mood disorders is proposed in conjunction with potential antidepressant mechanisms of antiglutamatergic agents. Further studies elucidating the role of the glutamatergic system in the pathophysiology of mood and anxiety disorders and studies exploring the efficacy and mechanism of action of antiglutamatergic agents in these disorders, are likely to provide new targets for the development of novel antidepressant agents.     

Awareness of the false memory manipulation and false recall for people's names as critical lures in the Deese-Roediger-McDermott paradigm

In the present study, people's names were used as Critical Lures (central concept not on the lists) in the Deese-Roediger-McDermott (DRM) paradigm for studying false recall. Following Mukai, the transparency of false memory manipulation in the paradigm was manipulated to explore its influence on false recall. 80 volunteers (age range 17-30 years, M age = 20.9 yr., SD = 1.6) took part. Analyses showed that making the critical lure inconspicuous did not significantly increase false recall. However, the proportion of falsely recalled Critical Lures was significantly lower and the proportion of critical lures produced on a postrecall test (asking participants to report items that they had thought of but did not recall) was significantly higher when they spontaneously realized the nature of false memory manipulation. However, there was no effect on veridical recall of study items. These results suggest that participants strategically avoided reporting false recall for people's names as Critical Lures even without forewarning about false memory.     

Greater attention problems during childhood predict poorer executive functioning in late adolescence

Attention problems (behavior problems including inattention, disorganization, impulsivity, and hyperactivity) are widely thought to reflect deficits in executive functions (EFs). However, it is unclear whether attention problems differentially relate to distinct EFs and how developmental stability and change predict levels of EFs in late adolescence. We investigated, in an unselected sample, how teacher-rated attention problems from ages 7 to 14 years related to three correlated but separable EFs, measured as latent variables at age 17. Attention problems at all ages significantly predicted later levels of response inhibition and working memory updating, and to some extent set shifting; the relation to inhibiting was stronger than the relations to the other EFs or IQ. Growth models indicated that attention problems were quite stable in this age range, and it was the initial levels of problems, rather than their changes across time, that predicted later EFs. These results support the hypothesis that attention problems primarily reflect difficulties with response inhibition.     

A prelinguistic gestural universal of human communication

Several cognitive accounts of human communication argue for a language-independent, prelinguistic basis of human communication and language. The current study provides evidence for the universality of a prelinguistic gestural basis for human communication. We used a standardized, semi-natural elicitation procedure in seven very different cultures around the world to test for the existence of preverbal pointing in infants and their caregivers. Results were that by 10-14 months of age, infants and their caregivers pointed in all cultures in the same basic situation with similar frequencies and the same proto-typical morphology of the extended index finger. Infants' pointing was best predicted by age and caregiver pointing, but not by cultural group. Further analyses revealed a strong relation between the temporal unfolding of caregivers' and infants' pointing events, uncovering a structure of early prelinguistic gestural conversation. Findings support the existence of a gestural, language-independent universal of human communication that forms a culturally shared, prelinguistic basis for diversified linguistic communication.     

Cross-modality priming for people's adjectivized names: failure to support the adjectivization hypothesis

This experiment tested a prediction derived from Hollis and Valentine's 2001 adjectivization hypothesis, that having an adjectival form is the key factor that makes certain classes of proper names, i.e., country names, exhibit a common name-like pattern of long-term priming. The hypothesis predicted that, when adjectivized historical celebrity names, e.g., William Shakespeare/Shakespearean, were compared with nonadjectivized historical celebrity names, e.g., Emile Zola, cross-modality long-term priming in a familiarity decision task would occur only for nonadjectivized name stimuli. 32 students of literature, history, or philosophy (21 women and 11 men; age range 18-41 years, M age = 22.4 yr.) were tested. Priming was measured by latency of response. Analysis showed that the mean RT to primed items was faster than the mean RT to unprimed items when the prime task was presented in both visual and auditory modalities both for the adjectivized and nonadjectivized names. Contrary to the hypothesis, cross-modality priming was observed regardless of the adjectivization of name stimuli. The findings of the present experiment did not support the adjectivization hypothesis.     

Testosterone prevents synaptic loss in the perineal motoneuron pool in the spinal cord in male rats exposed to chronic stress

Chronic stress is known to induce disorders of reproductive neuroendocrine functions. Motoneurons of the spinal nucleus of the bulbocavernosus (SNB) in male rats play an important role in copulatory behavior. In the present study, it was examined whether chronic stress would alter synaptic organization of the SNB motoneurons and whether androgen would modify the changes under chronic stress. Five male rats were under restraint stress for 5 days per week for 3 weeks, and five males implanted subcutaneously with Silastic capsules containing testosterone were also exposed to stress. Five males served as unstressed controls. After 3 weeks of restraint stress, cholera toxin-horseradish peroxidase (CT-HRP) was injected into the bulbocavernosus muscles and animals were killed 2 days later. The spinal cords containing the SNB were dissected, processed with a modified tetramethylbenzidine (TMB) method for visualization of retrogradely transported CT-HRP, and examined ultrastructurally. Neuronal structures apposing the membranes of 150 SNB motoneurons (total for three groups) were analyzed by measuring the percentage of somatic membranes covered by synaptic contacts. The mean percentage of somatic membranes covered by synapses in males exposed to chronic stress was significantly less than that in controls or stressed males treated with testosterone. Size and number of synaptic contacts per unit length of somatic membranes in males exposed to stress were also significantly less than those in controls or stressed males treated with testosterone. There was no significant difference in any of the parameters between controls and stressed males treated with testosterone. Changes in plasma levels of testosterone showed the same profile as changes in the synaptic contacts. These results suggest that the SNB motoneurons of male rats exposed to chronic stress retain a considerable synaptic plasticity in response to androgen, and that androgen treatment can rescue the SNB system in male rats when under chronic restraint stress.     

Comparison of four scoring methods for the reading span test

This study compared four common methods for scoring a popular working memory span task, Daneman and Carpenter’s (1980) reading span test. More continuous measures, such as the total number of words recalled or the proportion of words per set averaged across all sets, were more normally distributed, had higher reliability, and had higher correlations with criterion measures (reading comprehension and Verbal SAT) than did traditional span scores that quantified the highest set size completed or the number of words in correct sets. Furthermore, creation of arbitrary groups (e.g., high-span and low-span groups) led to poor reliability and greatly reduced predictive power. It is recommended that researchers score span tasks with continuous measures and avoid post hoc dichotomization of working memory span groups.     

Behavioral evidence for format-dependent processes in approximate numerosity representation

A genuinely abstract number representation is thought to be capable of representing the numerosity of any set of discrete elements, whether they are sequentially or simultaneously presented. Recent neuroimaging studies, however, have demonstrated that different areas of intraparietal sulcus play a role in extracting numerosity across simultaneous or sequential presentation during a quantification process, suggesting the existence of a format-dependent numerical system. To test whether behavioral evidence exists for format-dependent numerical processing in adult humans, we measured the Weber fractions of numerosity discrimination for sequential stimuli, simultaneous stimuli, and cross-format stimuli with a carefully controlled experimental procedure. The results showed distinct differences between the performance in the simultaneous and sequential conditions, supporting the existence of format-dependent processes for numerosity representation. Moreover, the performance on cross-format trials differed among participants, with the exception that performance was always worse than in the simultaneous condition. Taken together, our findings suggest that numerical representation may involve a complex set of multiple stages.